ECOLOGICAL STUDIES ON ILLAWARHA
LAKE WITH SPECIAL REFERENCE TO
Zostera capricorni Ascherson.
By
Malcolm McD. Harris, B.A. ( Univ. of New England, Armidale )
A thesis submitted in fulfilment of the
requirements for the degree of Master of Science
of the University of New South Wales.
School of Botany,
University of New South Wales.
January, 1977 UNIVERSITY OF N.S.W.
19851 16 SEP. 77 LIBRARY THIS IS TO CERTIFY that the work described in this thesis has not been submitted for a higher degree at any other university or institution. (iii)
SUMMARY
This thesis describes aspects of the ecology of Illawarra
Lake, with special reference to the biology of the seagrass,
Zostera capricomi Aschers. Observations were made from the air, from power boats, by wading and by SCUBA diving, over the period 1972 - 1976. Use has also been made of aerial photographs. The environmental factors studied include both sediment characteristics and water quality. Correlation coefficients have been calculated and used in the assessment of the functional relationships between the parameters examined.
Reference has been made to corroborative evidence from a number of sources.
The relationship between the distribution and biomass of the benthic flora of Illawarra Lake, and the selected environmental parameters, is examined. Seven other coastal saline lagoons were observed so that observations made and the conclusions drawn for Illawarra Lake, could be seen in the wider context.
Long term observations and analyses have been made of the morphology, growth and flowering cycles of Z. capricomi. Evidence is presented showing some diagnostic features,used in published accounts to distinguish between Z. capricomi and Z. muelleri « are of little taxonomic use.
Propagation of Z. capricomi was investigated by transplanting sods and rhizomes into natural and dredged sediments, together with observations of areas of the lake known to have altered in recent years. Seed production has been assessed and photographs showing germinating seeds and seedlings of Z. capricomi. observations not previously recorded in the ( iv ) literature, are presented.
Data is also presented on the population and biomass of benthic macrofauna of Z_. capricomi colonised sediments, together with the feeding habits of a variety of birds, demonstrating the importance of seagrasses and other components of lake flora in the biology of coastal saline lagoons. (v)
CONTENTS
PAGE
SUMMARY (iii)
1. BACKGROUND AND APPROACH TO THE PROBLEM
1.1# Statement of the Problem 2
1.2. Scope of the Investigation 4
1.2.1. Illawarra Lake and Other Coastal Lakes 4
1.2.2. The Study Area : Geological and
Geographical Outline 10
1.2.3. Data Collected 15
2. ENVIRONMENTAL FEATURES
2.1. Introduction 18
2.2. Sediments 19
2.2.1. Previous Data 19
2.2.2. Particle Size Analysis 20
2.2.3. Nutrients - Organic Carbon 29
2.2.4. Nutrients - Total Phosphorus 30
2.2.5. pH 32
2.2.6. Eh 34
2.3. Water 37
2.3.1. Previous Data 37
2.3.2. Salinity 43
2.3.3. Temperature 46
2.3*4. Nutrients - Total Phosphorus 48
2.3.5. pH '48
2.3.6. Eh 49
2.3.7. Turbidity 49
2.4. Conclusion 51
3. BIOLOGICAL FEATURES
3.1 Introduction - Other Lakes 78 3.2. Distribution of Animals in Illawarra Lake 37
3.3* Distribution of Algae in Illawarra Lake 99
3.3.1. Gracilaria confervoides 99
3.3.2. Lamprothamnion 103
3.3.3. Epiphytic Algae of Angiosperms 104
3.3.4. Filamentous Algae 107
3.4. Distribution of Angiosperms 112
3.4.1. Taxonomy 112
3.4.2. Ecological Observations on Posidonia
australis 113
3.4.3. Ecological Observations on Halophila
ovalis 115
3.4*4. Ecological Observations on Ruppia maritima 116
3.4.6, Zostera capricomi and Zostera muelleri 127
BIOLOGY OF ZOSTERA CAPRICORNI IN ILLAWARRA LAKE
4.1, Introduction 132
4.2. Taxonomy of Genus Zostera 133
4.3* Distribution of Zostera in Illawarra Lake 139
4.3.1. Introduction 139
4*3.2, Distribution of Zostera in Relation to
Environmental Factors 139
4.3.3* Zostera Biomass in Relation to
Environmental Factors 150
4.4. Growth of Zostera oapricomi in Illawarra Lake 168
4.4.1. Morphological Variations in Zostera
capricorni 168
4.4.2. Vegetative Cycle of Zostera capricomi 168
4.4.3. Flowering and Seed Production in Zostera ( vii )
4.4*4* Propogation of Zostera capricomi in
Illawarra Lake 183
4*5* Conclusions Related to Published Work 195
5. REFERENCES 203
6. APPENDIX
Appendix A1 215
Appendix A2 218
Appendix A3 233
Appendix A4 239
7. ACKNOWLEDGEMENTS 256 ( viii)
MAIN PLANT SPECIES.
ALGAE
Bnteromorpha intestinalis ( L. ) Link.
Gracilaria confervoides f. ecortica May
Lamprothamnion papulosum ( Wallr. ) J. Gr., em. R.W.D.
ANGIOSPERMEAE
Halophila ovalis ( R. Br. ) Hook, f.
Heterozostera tasmanica ( Martens ex Aschers. ) den Hartog
Phragmites australis ( Cav. ) Trin. ex Steud.
Posidonia australis Hook, f.
Ruppia martima L. ex Dumort.
Trifflochin procera R. Br.
Zostera capricomi Aschers.
Zostera muelleri Irmisch. ex. Aschers 1
BACKGROUND AND APPROACH TO THE
PROBLEM 2
1.1 STATEMENT OF THE PROBLEM.
Saline lagoons are a notable feature of the N.S.W. coast.
Despite their prominence, few have been studied and relatively little
of their biology had been discussed in publications prior to the
commencement of this study. The only detailed investigation was
that of Macquarie Lake ( Baas Becking, 1959; David, 1959; MacIntyre,
1959; Spencer, 1959; Thomson, 1959 a,b,c,d; and Wood, 1959 a,b,c. )
made in relation to an alleged depletion of fish. Higginson ( 1965 )
discussed the aquatic plants of the Tuggerah Lakes and in 1971> he
reported upon pollution effects in the same system. This investigation
was undertaken to provide information on environmental and biological
aspects of Illawarra Lake.
Illawarra Lake is surrounded by one of the most heavily urbanised
coastal lake catchments in N.S.W. Until recently, and perhaps even
still, only token attempts have been made to control pollution,
regulate development and maintain environmental quality. The agents
that have created environmental problems include not only the private
urban developers, heavy industries or quarries, but also the residents
who litter, dump rubbish indiscriminately, abandon motor vehicles and
deliberately or accidentally discharge septic tank effluents into the
drainage system. Neither are government agencies without fault. The
Metropolitan Water Sewerage and Drainage Board provides for emergency
overflow into the lake of sewerage mains during high rainfall periods.
The N.S.W. Housing Commission has undertaken housing development
adjacent to streams without taking adequate precautions to prevent the
mobilisation of sediment and rapid siltation of lake shallows. The
Department of Main Roads and both of the local councils have failed
to control sediment mobilisation and lake siltation associated with
road construction and maintenance within the catchment. Further, the
decision by the Public Works Department,that the road access across the 3 entrance to the lake should include a causeway, has contributed to a degrading of aquatic habitats in that area, to a restriction of tidal flow and to an aggravation of local flooding.
This public and private neglect and abuse has subjected the lake to increasing environmental changes. It was considered essential that basic data be gathered so that the nature, extent and effects of these changes could be gauged, thus making possible the development of criteria useful in the formulation of lake management policies.
The studies cited, together with those of Renn ( 1936 ),Dexter
( 1950 ), Imai ( 1951 ),Baas Becking and McKay ( 1956 ), Thomson ( 1959 e )
Wood ( 1967 ),Brown ( 1969 ),McRoy and Barsdate ( 1970 ), Fox ( 1972 ),
Braithwaite ( 1975 ),Powis ( 1975 ), Adams ( 1976 a,b ) and Pollard
( 1976 ) drew attention to the basic role of benthic flora; in the biological energy budget of lakes, as shelter and a nursery for commercial fish, as a habitat for myriads of other organisms, in the stabilisation of sediments, and in the recycling of nutrients between the sediment and the water.
The emphasis in this study was placed upon an investigation of the biology, distribution and abundance of the benthic flora, together with an assessment of the influences of environmental factors upon this flora, 4
1.2 SCOPE OF THE INVESTIGATION.
1.2.1 Illawarra Lake and Other Coastal Lakes.
Lagoons on the N.S.W. coast have been formed by; the occlusion of shallow bays by bay mouth sand bars, the drowning of river valleys as a result of eustatic changes and coastal submergence, or by a combination of these processes ( Bird, 1965 )• The origin and subsequent evolution of the lake has a marked influence upon its hydrology and bathymetry. Lakes derived by sand bar occlusion of bays tend to be broad, shallow, exposed, turbulent expanses of water with an extensive sandy zone on which benthic ( submerged ) flora may survive. Of the 8 lakes observed in this study ( Pig. 1.1 ), Toubouree,
Swan, Tuggerah, Wollumboola and Illawarra Lake exhibit these features.
By comparison, lakes derived mainly by the drowning of river valleys tend to be irregular in shape, dendritic with numerous protected reaches, deeper, with a steeply rising foreshore and with a narrow zone of benthic flora growing upon variable sediments. Conjola,
Macquarie and Burrill Lake exhibit these features. All of these lakes have narrow tortuous, shallow channels connecting them with the sea.
The mouths of these channels, except in the case of Macquarie Lake,
/ \ * are frequently or intermittently closed by sand bars. Table Al.l J.
Given the ageing process to which lakes are subjected
( Powers and Robertson, 1966 ) and the combined effects of sedimentation and eutrophication suffered by lakes in urban areas ( Edmondson,1969 )
Illawarra Lake by virtue of its bathymetry, hydrology and location was seen to be vulnerable and urgently in need of study and management.
Illawarra Lake is smaller than Macquarie Lake, comparable in size with Tuggerah Lake, but is considerably larger than the other shallow lagoons cited in this study. Hence with the exception of
* Tables and figures appearing in the Appendix bear the prefix A. 5
150-50
,----Port Stephens
Newcastle Hunter River
Macqusu.’ie Lake
The Tuggerah Lake s
Port Jackson Sydney
Botany Bay
Port Hacking
Wollongong 3 4-30 34-30 Illawarra Lake
Shoalhaven River Crookhaven inlet ■ Wollvunboola Lake
Jervis Bay
St. Georges Basin Swan Lake Conjola Lake •Burrill Lake Tou bounce Lalce Fig. 1.1. LAKES, BAYS AND INLETS ON THE Tcrnieil Lake N.S.W. COAST’ - PORT STEPHENS Mcroo 1 .alee TO BATEMANS BAY. 'Willinga Lake Burras Lalce Batemans Bay
150-50 k m 40 60 80 100 6
Macquarie Lake and the Tuggerah Lakes, it is therefore more stable and less subject to marked fluctuations resulting from small environmental changes. Similarly its greater size allows for the development of greater diversity of habitats. It also offers a wider range of environmental factors to influence the composition and biomass of the benthic flora.
In 1972, when this study was commenced, little environmental data was available for Illawarra Lake. Wood ( 1964 ) included a scant reference to salinity, Eh and pH of lake waters and sediments. Intermittent surveys had been conducted by and on behalf of the Wollongong City Council Health Surveyor. These analyses, including Escherichia coli counts, indicated contamination of the lake waters by domestic sewage and revealed nutrient levels sufficient to produce nuisance algal growth ( Table A1.2 ).
During 1972, Dr. J. Ellis from the Chemistry Department of
Wollongong University initiated an investigation of Illawarra Lake to determine salinity variations, tidal ventilation, thermal pollution and the nutrient status of the lake water.
Several aerial photographic surveys of the lake were available, the earliest dating from 1949* Many of these photographs were taken during periods of high turbidity or on days of strong wave action and therefore reveal little information on submerged features.
Those that were taken on calm days^when the lake turbidity was low, have provided invaluable information on seagrass distribution, development of the foreshores, sediment accretion and delta formation.
The State Pollution Control Commission ( S.P.C.C. ) commenced the monitoring of lake water quality during 1974 and though these surveys have been only intermittent they have provided useful corroborative data*
In 1975,the Wollongong City Council secured a grant from 7 the Department of Urban and Regional Development of the Australian
Government, to finance a study of Illawarra Lake. The purpose of this multidisciplinary study was to gather data and develop criteria useful in the formation of lake management policies. This report, published by the Wollongong City Council, September 1976, under a National
Estate grant, includes two articles on the biology of the lake. These are Part 5 - EcologicalM ilieu of Illawarra Lake, and Part 6 - The
Biota of Illawarra Lake ( Harris, 1976 ).
Illawarra Lake is a valuable natural resource. It is the last remaining expanse of enclosed water in the Illawarra region. With the growing industrial development and environmental deterioration of
Botany Bay to the north ( Fox, 1972 ) Illawarra Lake must assume greater significance as a refuge for aquatic birds, many of which are migratory and rare. A list of aquatic birds observed on Illawarra Lake during this study is presented in Table A%
The economic significance of estuaries to the commercial fishing industry of N.S.W. has been reviewed by Pollard ( 1976 ). In that report, the dependence of the commercial fishery upon the estuaries as nursery grounds was established clearly. It wa3 shown that about 60% of the catch offered for sale on the Sydney Fish Market, was dependent upon the estuarine environment, during some stage of its development.
Illawarra Lake is important as a regional fishery. A monthly average of
25 fishermen have caught a 10 year annual average of 15,900 Kg of fish and 72,500 Kg of prawns, worth an estimated $280,000 annually ( N.S.W.
Fisheries Department - unpublished ). While only limited sand extraction has occurred from the entrance, the sand reserves within the lake exceed
50 x 10^ tonnes ( Soros-Longworth and McKenzie, 1976 ). Any attempt to utilise this resource would destroy the seagrass beds of the Windang
Peninsular and Bevans Island and would pose a serious threat to both the commercial fishery and amateur prawning. Industrially, the lake water is 8 used as a coolant for Tallawarra Power Station.
Aesthetically, Illawarra Lake shares with most similar expanses of enclosed water, the appreciation of mankind everywhere as is reflected in real estate prices, tourism and the abundance of holiday makers. As a recreational resource, the lake is used extensively for sailing, power boating, water-skiing, fishing and prawning, with limited swimming in the entrance channel. To date the financial return to the region from tourism and holiday resort activities attributable to the lake has not been assessed but it is believed to be considerable and capable of greater exploitation.
The threat to the continued existence of the lake as a valuable regional resource stems from four causes: nutrient enrichment,
sedimentation, heavy metals, and thermal pollution.
(i) Nutrient enrichment.
Nutrient increments from prolonged sewage contamination,
as well as from farm wastes and fertilizers have created a
state of marked nutrient enrichment. The excessive plant
growth ( algae and Zostera ) that results from these
additions becomes unsightly, accumulates in shallows and
along the shore during strong winds, decomposes and
becomes a foul-smelling nuisance. Contamination by sewage
must also pose a health risk for water contact recreation.
(ii) Sedimentation and flooding.
Extensive urban development, road construction,
quarrying and mining within the catchment have mobilised and
will continue to mobilise large volumes of sediment.
Leopold ( 1971 ) drew attention to the fact that urban
development increases surface run-off dramatically. The
magnitude of peak discharge from sewered areas, and hence
flooding severity may increase by 200 to 400 The frequency 9
of overbank flooding may increase by up to 400
Sediment load resulting from this greater frequency and severity of flooding may increase markedly, exceeding 2 erosion from woodland by a factor of 2-4 x 10 in a similar period. The consequences of this increased erosion have been; the more rapid siltation of the entire lake with incipient to marked deltaic formations at the outlets of most drains and creeks, localised but rapid siltation of some shallows causing them to become emergent during periods of low water ( this effect is most marked in Griffins Bay, Koonawarra Bay, adjacent to Hooka Creek and in Koona Bay ), and to maintain and probably increase the turbidity of the lake water,thus rendering it aesthetically less attractive and limiting the euphotic zone. More severe and frequent flooding not only represents an increasingly perplexing problem for the low-lying caravan parks and residential development,but also increases the salinity variability of the lake. This imposes more frequent and more severe osmotic stresses upon lake fauna and flora.
(iii) Heavy metals.
Investigations by Beavington ( 1973 ) showed that sediments within 5 km of Pt. Kembla heavy industrial area had been contaminated with heavy metals. Later studies by
Roy and Peat ( 1974 ) demonstrated that this contamination extended to the sediments of Illawarra Lake and particularly those of Griffins Bay. In these sediments the concentrations of copper, lead and zinc were twice, three times and four times that found in sediments from the southern portion of the lake. This metal pollution could be incorporated into 10
the biota and hence become a health risk.
(iv) Thermal pollution.
The water of Illawarra Lake is used as a coolant in
the Tallawarra Power Station. Studies by Warinner and
Brehmer ( 1966 ), Clark ( 1969 )* Langford ( 1972 ) and
Coulter et ad. ( 1974 ) on the environmental effects of
thermal discharges to rivers and lakes,and the impact of
these discharges upon the biota^indicated that some degree
of thermal pollution could occur in the vicinity of the
power station.
1*2.2 The Study Area : Georeaphical and Geological Outline.
Illawarra Lake,Latitude 34°30' S. Longitude 150°50* E ,
straddles the boundary between the City of Wollongong in the north
and Shellharbour Municipality in the south ( Pig. 1.2 ). It has a
maximum length of 9*5 km, a maximum width of 5*5 km, an area of
33 km and an estimated volume of 6 x 10 in ( Kanamori, 1976 ). The
lake is shallow; it is estimated that 25 % of the lake is usually
less than 1.2 m deep and the maximum depth is usually about 3*7 ®
( Roy and Peat, 1973 )• All water depths quoted in this study have
been reduced to normal lake level which is that adopted as 3*50 feet
( 1.065 metres ) above L.W.O.S.T. ( Ocean ) Port Kembla ( as indicated
on P.W.D. plan,Lake Illawarra No. 24992 ) and gauged at the Tallawarra
Power Station inlet channel.
There is an extensive zone of Zostera up to 1 km wide, in
water less than 1,5 m deep on the eastern side of the lake. These
seagrass beds extend 5*7 km from Boonerah Pt. to beyond Purry Burry
Pt. at Primbee.
Because it is oriented approximately N-S and is exposed to
strong southerly and southwesterly winds, the lake water can become
turbulent, with wave heights approaching 50 cm ( Eliot, 1976 ). This 11
Hooka Ok.
Kuily Bay
Joes Bay Mullet Ck, C7 O Purry Burry Pt
Nieolle Rd
Brook:; Ck,
Koonawarra Bay 2WL Transmitter ILLAWARRA LAKE
Tallawarra Pt Cudgeree Hole
Pith-Thung-Nar Bay Tallawarra
Power Yallah Bay Station Bevans Is do 11 ingurry Ck Back Channel
V/incang Is
Mt. Warrigal
Oakey Ck.
Horsley Ck.
GEOGRAPHICAL NAMES 12 turbulence, coupled with the shallow nature of the lake causes considerable turbidity and is probably a significant factor in maintaining the concentration of dissolved oxygen ( Kanamori, 1976).
Illawarra Lake is a saline lagoon that has evolved from a broad bay, that formed as a result of eustatic changes in
Pleistocene times ( Langford-Smith, 1969 )• These sea-level fluctuations resulted in repeated drowning of the natural drainage channels of Macquarie Rivulet, Brooks Creek and Mullet Creek. The bay was later occluded from the sea; the last occasion was at the end of the Holocene Transgression, 6 - 7000 years ago ( Thom, 1974 ) by the reformation of a baymouth sand bar extending from Red Point in the north to Windang Island in the south.
Since the time of submergence, the area of the lake is estimated to have decreased by about 17 % and sedimentation has filled about 90 io of the original lake basin ( Young, 1976 ). Roy and Peat
( 1974 ) estimated an average annual rate of sedimentation for the last 6,000 years of 1.4 mm/year. If this trend were to continue, the entire lake would be converted to a shallow swamp 1,200 to 1,500 years from now ( Young, 1976 ) and would have ceased to perform its current economic and recreational roles long before then. Studies of the delta formations of Macquarie Rivulet and Mullet Creek by Brown ( 1969 ) and Young ( 1976 ) show this rate of sedimentation to be a conservative estimate, a view shared by Roy ( pers. com. ). The rapid expansion of these deltas and the increasing rate of accretion that has occurred since the clearing and settlement of the catchment has accelerated the rate of infilling far above the long term average.
The occluding dune system of marine sands shows evidence of alternating periods of accretion and erosion ( Young, 1976 )• It varies in width from 2.7 km at Primbee to 0.8 km at Windang and reaches a maximum height of 15 m adjacent to Primbee. Stabilisation of these 13
dunes has been achieved by species of Spinifex. Hydrocotyle, Acacia,
Leptospermun, Banksia, Casuarina, Juncus and Eucalyptus with later invasion by several species of salt tolerant grasses. Sand extraction has been permitted in the area and severe beach and dune erosion have been evident during the last few years.
At present the lake entrance occurs near the southern end
of the sand barrier where it is partially protected by Windang Island,
This rocky prominence, which commonly is land-tied by a tombolo, tends
to dissipate wave energies and thus suppresses the rate of infilling of
the entrance channel. In the past, other entrances have existed and
traces of these are clearly discernible on early aerial photographs.
Recent urban and industrial developments have obliterated much of the
evidence. The more notable of these include the still existing
Coomaditchy Lagoon and the lagoon to the south of Primbee Hill. These
archaic entrances occurred on a region of high wave energy coastline
and have been occluded.
The present channel from the lake to the sea changes
continually in position, width and depth,depending on rainfall, wind
and wave action. During the period 1972 to 1976, it has been about
2.4 km long, winding and varying in depth between 0.5 to 2.5 m.
Though the entrance has a maximum width of 600 m, the main channel
is seldom wider than 100 m and at places is less than $0 m wide. On
several occasions during the recent past the entrance has been choked
with sand. The last occasion was in the summer of 1971 when a
bulldozer was used to remove the blocking bar.
As a consequence of the restricted access to the sea,
very little tidal influence extends into the lake, even during spring
tides.A 1.8 m rise at Port Kembla Harbour resulted in a rise of 0.2 m
at Windang Bridge ( Robinson, unpublished ). Tidal gauging by the N.S.W.
Electricity Commission at Tallawarra Power Station has established that 14 the lake at times experiences a tidal rise of about 0.1 m on the western side ( Eliot, 1976 ). Investigations by Kanamori ( 1976 ) indicated a tidal exchange of 1 $ of lake volume for each tidal cycle.
Observations by Roy and Peat ( 1973 ) revealed that the outflow of lake water may be increased markedly by persistent, strong,westerly winds.
In spite of this apparently limited tidal flow, there is extensive evidence,in the pattern of the dunes and bars at the eastern end of the channel ( clearly visible on aerial photographs ) of beach sand being swept into the lake. Wave action during heavy storms reinforces this tidal transport,sweeping large quantities of ocean sand up the inlet,to form an extensive tidal delta at the lake end of the channel. These developments are clearly evident in a comparison of
Lands Department aerial photographs taken in 1949 ( Kiama, Run 2K, July
•49, 261-35 ), 1963 ( Kiama Run IK, August *63, 1189-5109 ), 1972 ( N.S.W.
Coastline, Run 11, 1.7.72, 2019-5106 ) and 1974 ( Kiama, Run 1, 29.12.74,
2288-143 ).
Six to seven km to the west of the lake, the escarpment of the Illawarra Range rises to an elevation of 300 to 460 m. It is composed of Triassic, Hawkesbury Sandstone and the Narrabeen Group which overlie the Permian, Illawarra Coal Measures. The northern and southern boundaries of the lake catchment are determined by resistant ridges of latite of the Permian, Gerringong Volcanics ( Nashar, 1967 ).
Fig. Al.l shows the geology of the Illawarra Lake region. The area of the lake catchment,as estimated by the " cut and weigh M method,is 2 approximately 200 km . Apart from the alluvium filled valleys of the
Macquarie Rivulet and Mullet Creek, the area to the west of the lake, below the escarpment, consists of low, undulating,residual ridges and hills.
Prior to settlement, the catchment supported mixed eucalypt 15 and cedar forests that have been cleared for farming, grazing and
•urban development. Remnants of the coastal rainforest vegetation exist on Hooka Island, Gooseberry Island and to a lesser extent on
Wollamai Point ( Table A1.3 )• Fringing growths of Phragmites australis exist at several points around the lake, particularly along the Windang Peninsular and in the entrance channel.
1.2.3 Data Collected.
The data and observations presented in this thesis have been gathered over the period 1971 to 1976. For convenience, some aspects of environmental data are considered separately from biological information.
Observations have been made from an aeroplane, from the shore and from power boats. Samples of fauna, vegetation, water and sediments have been collected from a boat, by wading and by SCUBA diving.
The environmental data on water characteristics include depth, salinity, temperature, turbidity, pH, Eh, and total phosphorus.
The data on sediments include particle size, organic carbon, pH, Eh and total phosphorus.
Observations have been made of the distribution and abundance of the benthic flora and their epiphytes, as well as of algal growths. Detailed investigations have been made of the distribution of Zostera, the relationship between Zostera biomass and environmental parameters, the recolonisation by Zostera of normal and disturbed sediments, the response of Zostera to transplanting, and the morphological variations in Zostera. Long term observations of the growth and flowering cycles of Zostera capricomi have also been presented*
Zoological data include long term observations of the 16 feeding of birds, particularly swans and ducks, and the differences
in the benthic macrofauna in Zostera beds at four sites within
Illawarra Lake. 2
ENVIRONMENTAL FEATURES 18
2.1 INTRODUCTION.
Early studies by Pond ( 1905 ) and Misra ( 1938 ) established
that sediment characteristics were significant factors in determining
both the distribution and abundance of freshwater benthic flora.
Published reports by Wood ( 1959 a ) and Higginson ( 1965 ) indicated
that the distribution of the benthic flora of coastal saline lagoons
may be influenced by the sediment factors, redox potential ( Eh ),
particle size and nutrient status. Higginson ( 1965 )* in his study of
the Tuggerah Lakes, a system similar to Illawarra Lake,
concluded that sediment particle size, possibly because of its effect
upon the nutrient status, was of prime significance in explaining the
distribution of Zostera capricomi and Ruppia maritima in that lake.
Both authors agreed that illumination was important and therefore
water depth and turbidity were limiting factors. The predominant
species of benthic flora, Zostera capricomi and Ruppia maritima were
found to differ in their tolerance of currents with Ruppia being
restricted mainly to lentic situations. Both species were found to
tolerate a wide range of salinities,but Wood ( 1959 a ) suggested that
Zostera grew best at about sea salinity.
Because of the wide range of environmental factors implicated,
it was determined that in this study, analysis of both sediment and
water characteristics should be undertaken. Sediments were analysed
for particle size, organic carbon content, total phosphorus, pH and
Eh. Water monitoring and analyses were selected to gather data
relating to possible environmental hazards including salinity
fluctuations, flooding, turbidity, water temperature ( and thermal pollution ) and the total phosphorus content as an indication of nutrient enrichment. 19
2.2 SEDIMENTS.
2.2.1 Previous Data.
Wood ( 1959 b ) commented briefly upon the relationship between sediment type and the distribution of benthic flora in
Macquarie Lake. He observed that Posidonia grew upon an oxidised, sandy substrate ( Eh to +250 mV ) with a low organic content, while
Zostera grew in more reduced environments. The role of Zostera, in helping to create these reducing conditions by excreting reducing substances, was reported by Wood ( 1955 )• Wood ( 1959 a ) stated that Zostera grew well in sediments in which the Eh varied from
+180 mV to -150 mV, with abundant H^S and a pH as low as 5*5» Even when the surface sediments were oxidised, the Zostera roots were generally in a reducing environment, with strong sulphate reduction proceeding a centimetre below the surface. Zostera was observed to grow on a sediment range from gravels to mud. Ruppia was also reported to grow on reduced muds.
Higginson ( 1965 ) concluded that sediments played a major role. Zostera tended to favour sandy sediments while Ruppia grew more commonly on clay sediments. He also reported that an increase in the clay content of the sediments was associated with an increase in organic matter, nitrogen, potassium, magnesium and iron.
No published data on the sediments of Illawarra Lake were available at the commencement of this study. In 1975» Hoy and
Peat published their findings on the bathymetry and sediments of
Illawarra Lake. The sediments were grouped into broad categories but no detailed data on sediment particle size analyses were included 20
2.2.2 Particle Size Analyses.
Initially, sediment samples were collected from Zostera
and Ruppia beds at 21 sites within Illawarra Lake ( Fig. 2.1 ). At
each site, 3 cores, each 5 cm diameter and 10 cm deep,were extracted
using a cylindrical plastic corer, and mixed thoroughly in a plastic
container, after the addition of 50 ml of 10 % formalin solution
to prevent putrefaction.
In the laboratory, each sample was placed in a separate
1 litre beaker and mixed thoroughly with just sufficient distilled
water to produce a stiff slurry. A 50 ml sub-sample was taken from
each 1 litre beaker, placed in an evaporating dish and oven dried for
later organic carbon analysis. A second sub-sample of approximately
100 ml was analysed for particle size.
Particle size analysis was conducted according to the method outlined in Folk ( 1968 ). This is essentially:
(i) To the wet 100 ml sample in the 1 litre beaker,
add approximately 10 ml, 27£ $ hydrogen peroxide.
(ii) Add sufficient distilled water to completely cover
the sample, stir and leave overnight.
(iii) Next morning,add more hydrogen peroxide and speed
up the oxidation of the organic matter by heating gently
on a hot plate. Watch the sample carefully. If there is
a danger that the sample may froth and overflow, and this
cannot be controlled by stirring, add 1-2 drops of capryl
alcohol ( octan-2-ol or sec octyl alcohol ). Continue
adding hydrogen peroxide until no further reaction is
apparent. If the sample is rich in organic matter,this
process may take several days. Do not leave the samples on
the hotplate overnight as they will dry out and be difficult
to disperse.
(iv) When the oxidation of organic matter is complete,add 21
1972-75 Flora survey sites 1972-73, 1975-76 Secchi disc sites 1975 Sediment survey sites 1975 Sediment and benthic flora biomass survey sites - November 1975 Benthic macrofauna survey 1975 Zostera transplant sites 1976 Zostera biomass and sediment transects - January ♦ Dredge sites
Q I'll is and Kanamori sampling rites k m
2
j''i ;« j.l. SANPLING SITES - ILLAWARRA LAKE. 22
25 ml, 6 % Calgon ( sodium polymetaphosphate - a mixture
of approximately 88 % sodium metaphosphate and 12 %
sodium tetrapyrophosphate ) and agitate the sample in
an ultrasonic hath for 10 minutes.
(v) Separate the sand from the silt and clay by washing
the sample through a 65 pm sieve with distilled water and
pour the washings into a 1 litre measuring cylinder. If
more than 1 litre of water is needed to wash the sample
through the sieve then more than one cylinder may be used
and the results added together. Make the cylinders up to
1 litre with distilled water.
(vi) Wash the contents of the 65 pm sieve into an
evaporating basin and dry in an oven at 100°C for later
sieving.
(vii) To determine the silt and clay by the pipette method,
pre-weigh 2 x 50 ml beakers; stir contents of the measuring
cylinder for 1 minute with a stirring rod, taking care
not to break the surface as this may introduce air
bubbles.
(viii)At 20 seconds after stirring, insert a 25 ml pipette
20 cm into the sample and withdraw a 25 ml aliquot. Drain
the 25 ml sample into a 50 ml beaker and then add 25 ml
distilled water using the same pipette. This sample gives
total mud.
(ix) At 1 hr 58 minutes, insert the pipette to 10 cm and withdraw 25 ml. Drain the 25 ml sample into a 50 ml beaker and then add 25 ml distilled water using the same pipette.
This sample gives the amount of clay.
(x) Place the beakers in the oven and dry completely at
100°C for 1-2 days.
(xi) Reweigh when cool to determine the amount of mud and 23
clay in each 25 ml sample.
(xii) Subtract 0.02 g to correct for Calgon, then multiply
by 40 to determine the amount of sediment in each cylinder.
The silt content is obtained by subtracting the clay from
the mud sample.
(xiii)Sieve the oven dried sand samples through the
selected sieves ( Endecott laboratory test sieves, 500 pm,
250 pm, 63 pm ) on a sieve shaker ( Retsch ) for 15
minutes at maximum revolutions.
(xiv) Empty the contents of each sieve onto waxed paper and
weigh.
(xv) Collect and weigh the fines that pass through the
63 pm sieve, and add proportionally to the silt and clay
fraction to give the total weight of silt and clay. By
convention, the percentages of non-volatiles is calculated
without including volatile matter in the total weight.
The results of these analyses are shown in Table A2.1 and
Fig. 2.2. The data show that the sediments supporting seagrass vegetation in Illawarra Lake are mostly sandy. The extensive seagrass bed zones adjacent to the Windang Peninsular and Bevans Island
( sites 1, 14, 17, 18 and 21 ) occur on sediments with a sand content greater than 93 % by weight. Most other sites yielded high sand contents in excess of 80 % by weight. Only at site 5 ( 52 io sand ) adjacent to Macquarie Rivulet in Koona Bay, and at site 9 ( 88 % sand ) in Koonawarra Bay, an area that has received large additions of sediment from Brooks Creek,were there significant difference in texture from that observed elsewhere in the seagrass zone of the lake. Variations in sediment composition are summarised in Table
2.1. %
Carbon
Organic 24 %
Size
c 1 Partic
COMPOSITION OF SEDIMENTS SUPPORTING ZOSTERA IN ILLAW 25
TABLE 2,1 COMPOSITION OF SEDIMENTS ON WHICH SEAGRASSES
GROW IN ILLAWARRA LAKE
(a) Variation in Sand Fraction in Sediments Containing > 80 % Sand
Particles Coarse Sand Medium Sand Fine Sand
500 pm 500 to 250 pm 250 to 63 pm Frequency | Max, Min. , Max:, Min, . Max. Min.
% 14 0.1 71 2 90 17 Site______6______2______21 11______12 21
(b) Variation in Fines Fraction of all Sediment Samples from Seagrass Beds
Particles Silt Clay Total Fines <63 pm Frequency . Max. Min, | Max. Min, . Max. Min,_____
% 16 0.2 19 1 48 2 Site 9 1 5 12 5 11,16
nrnu ■■■■ zmmasst=sss==sxBsaamaBKBss:
The results of analyses of a further 13 sites from the eastern weed beds ( A to M on Fig. 2.1 ), taken in association with a benthic flora biomass survey, are given in Table A2.2.
More intensive investigations of textural variations within Zostera beds were conducted along two transects west of Bevans
Island and along two transects in Griffins Bay ( Fig. 2.1 ). The results of these analyses are given in Tables A2.3 and A2.4* The
Bevans Island transects encountered one facies change ( according to the classification of Roy and Peat ) with most samples being taken from muddy sand ( 51 - 95 % sand ) showing a variation in fines content ( particles 63 pm ) from 6 to 12 %, but one sample was of clean sand « 5 % mud ) Fig. 2.3# Griffins Bay samples were all taken from muddy sand but showed a variation in fines content from
9 to 23 % as shown in Fig. 2.4*
In an investigation of the effects of dredging upon sediments and Zostera recolonisation, samples were collected at various depths using a steel box corer ( Fig. 2.5 ) from within a Carbon
5° Organic O O M O VO H- CD o
pi i
> J
O — » $
O size
O O -P* 26 Particle o 'Osl (V) o
* — o I o
i*1 1*z !*4 !*5 1.6 1.7 2.1 2.2 2.5 2.4 2.5 2.6 2.7 2.8 T ran sect 1 S ite s T ransect 2 Fig* 2 .5. SEDIMENT COMPOSITION - BEVANS ISLAND TRANSECTS. °/o
Carbon -F^
ro Organic
1 — h O O
VO O
O CD
0 O — °/o co
n O CT Size
1 O VJ
O 27 Particle j T i
.
I
i i I
a ’ A
« \2 o o l till. ITT
i . 1 — i o jljli o -
j 3 -3 ►i co CD o c+ t 5 co 02 ct- CD CO S CD O c+ y
H- (\J • • J'l SEDIMENT COMPOSITION - GRIFF I ITS BAY TRANSECTS 28
—12 cm—a»J
Kitt, 2, ^. STAINLESS STEEL BOX CORER FOR EXTRACTION OF SEDIMENT SAMPLE. 2.9
3 m x 3 m. square, located in Zostera beds on muddy sand, west of
Sevens Island ( Fig. 2.1 ). Further samples were taken 5 weeks and
20 weeks after dredging the area to a depth of 20 cm. These data, as
given in Table A2.5, show a higher proportion of fines in the surface
sediment than at depth, and quite a dramatic increase in the
proportion of fines following dredging. Profiles of total phosphorus
and organic carbon, from the dredged area, are also given in Table
A2.5.
2.2.3 Nutrients - Organic Carbon.
In view of the correlations between clay, organic matter
and mineral content of lake sediments, as reported by Higginson ( 19&5 )
it was desirable that the lake sediment samples be analysed for organic
carbon. The method used was weight loss on ignition at 550°C as described by Dean ( 1974 ) and. appraised by Hallberg ( 1974 )•
Samples awaiting analysis were stored below - 18°C.
The analysis method used wa3:
(i) The sample was thawed and oven dried at 100°C for
24 hours.
(ii) The oven dried sample was thoroughly ground and
oven dried for a further 24 hours.
(iii) The samples were cooled in a desiccator. Three to
four grams were placed in a pre-weighed silica crucible and
the mass of the sample was determined.
(iv) The samples were then heated for 1 hour, at 550°C,
in an electric furnace.
(v) After cooling to room temperature in a desiccator,
the samples were once again weighed and the organic carbon
loss was calculated.
These various data ( Tables A2.1 to A2.5 ) show that the organic carbon content of sediments supporting seagrasses in Illawarra 30
Lake ranges from 0.5 to 8.5 /». In general, sediments with higher content of silt and clay contained more organic carbon than the more
sandy sediments.
2.2.4 Nutrients - Total Phosphorus.
Sediment samples from 59 sites ( Fig. 2.1, November benthic flora survey, Zostera biomass transects in Griffins Bay and
off Bevans Island, and the Bevans Island dredge site ), extending from
the seagrass beds west of Bevans Island, along the Windang Peninsular and into Griffins Bay, were analysed for total phosphorus,using an
acid digestion process. The samples were collected by the same method
as particle size samples but without the addition of formalin. In
the field,the samples were frozen using dry ice and were stored below - 18°C until analysed.
The analysis method used was:
(i) In the laboratory, the samples were thawed quickly
and stirred well in a glass beaker. 10 - 20 g of each
sample was placed in a clean 100 ml beaker and oven
dried at 80°C for 24 hours. The dry samples were thoroughly
ground, placed in a 10 ml test tube and then oven dried
for a further 24 hours at 110°C.
(ii) 1.00 g of the dried sample was placed in a 50 ml
beaker. 5*0 nil of concentrated A.R. nitric acid was added
and the slurry was gently heated on a hot plate, in a
fume cupboard, until dry. This digestion with nitric acid,
which took between 6 and 8 hours, was repeated twice.
(iii) The phosphate in the digested sample was then
dissolved by the addition of 0.1 ml of concentrated A.R.
nitric acid, plus 10 ml distilled water, and filtered
through a Whatman No. 542 ( 9 cm ) filter. The sample was
thoroughly eluted during filtration by several washings 31
with distilled water* The filtrate was collected and
diluted to 100 ml with distilled water*
(iv) A 10 ml sample of this solution was taken ana the
total phosphorus concentration was determined, using the
single solution method for dissolved orthophosphate as
described by Major ( 1972 )• A blank, obtained by the
evaporation of 15 ml of A*R* nitric acid, was also
analysed for total phosphorus content, as a measure of
the purity of the nitric acid* Colour development was
measured on a recording spectrophotometer ( Hitachi
Model EPS - 5T ) at 885 nm using a 10 cm cell*
Armstrong ( 1965 ) in his review of the methods for determining phosphorus in sear-water, reported that the single solution method, as adopted in this study, had the precision hown in the figures;
Mean phosphate pg P/l 0.5 1*0 2.0
Coefficient of Variation % ±10 ±5.0 ±5*5
To assess the variation in the total phosphorus content of sediments at any one site, cores from the dredged area off Bevans
Island, were analysed separately. For the surface samples, the observed range was 71 to 115 pg P/g sediment and a mean of 81 pg P/g sediment. The complete results of these analyses are given in Table
A2.6.
In the light of these determinations it was decided that to avoid the need to analyse an excessive number of replicates, 5 samples would be collected from each site and thoroughly mixed before analysis. The results of these several analyses are given in Tables
A2.2 to A2.6. In general, the sediments with higher content of silt and clay contained more total phosphorus than the more sandy sediments. 52
2.2.5 jaH.
pH was determined in the field at 39 sites using a specific ion meter ( Orion Model 407A ) and a pH combination electrode ( Orion No. 91-02 ). The electrode was calibrated against standard buffer solutions ( 0.05 m potassium hydrogen phthalate, pH 4*01 and 0.05 m sodium tetraborate, pH 9*18 ) that were carried into the field so that electrode stability could be checked between measurements.
As the performance of the glass pH combination electrode is affected by friction and scratching, it is essential that pH determinations be made of the interstitial water, and not of the sediment as a whole. Electrode damage in slurries can be quite rapid and costly, apart from the production of spurious readings.
To obtain interstitial water, sediment samples were taken using a 5 cm diameter plastic tube ( Pig. 2.6 ) which was driven into the sediment to the level of the small bungs ( 12 cm ).
A hole was then scraped into the sediment to expose the lower end of the tube, and a large bung was inserted. The tube was then withdrawn and the two small bungs were removed to allow the lake water to escape without disturbing the interstitial water trapped in the tube ( Pig. 2.7 )• The lower bung was removed and 10 cm of sediment, with its interstitial water, was then discharged into a pressure and vacuum filter ( Drager No. SM16510 ). Filtration was conducted under pressure, using a foot operated, car pump.
This reduces the loss of dissolved carbon dioxide and sulphurous gases. The pH of this filtered interstitial water was determined immediately.
These data are presented in Tables A2.2 to A2.5 • The narrow range of pH observed ( 7*4 to 8.0 ) is apparent. 53
1.5 m x 5 cm diam. plastic tube.
Lake Water Level
Sediment removed and bung inserted into lower end of tube to retain sediment and interstitial water.
Fig. 2.6. pH SAMPLE CORER
Bungs removed to allow lake water to decant.
Bung to retain sediment and interstitial water.
Fig* 2.7. pH SAMPLE CORER 34
2,2,6 Eh,
Wood ( 1959 a ) stated that Zostera grew mainly upon
reduced sediments, Hutchinson ( 1957 ), Jitts ( 1959 )>
Fitzgerald ( 1970 ) and Serruya ( 1971 ) demonstrated that the
interchange of phosphorus between lake waters and sediments was
controlled mainly by the redox potential ( Eh ) of the water and
sediment,For these reasons it was decided that the Eh of lake
water and sediments should be examined in this study.
Eh was determined in the field using a specific ion
meter ( Orion Model 407A ) and an Eh combination electrode
( Orion No, 96-78 ), The electrode was standardised using Zo Bell
solutions as described by Whitfield ( 1971 )• The Zo Bell solutions were carried into the field so that the electrode performance
could be checked between measurements, as sulphide poisoning of
the platinum electrode may result in spurious results. Because it was undesirable to totally immerse the electrode, in situ measurements could not be obtained, making it necessary to bring
sediment samples to the surface. Further, as the redox potential
of sediments is a measurement of activity and not of capacity
( ” buffer ability " ) care had to be taken to exclude atmospheric
oxygen from the sample.
To collect the sample, a 5 cm diameter plastic tube was inserted 10 cm into the sediment. The sediment was then scraped away to expose the lower end of the tube into which a large bung was inserted ( Fig, 2,9 )• The core was then removed with the
sample isolated from the atmosphere by a 5 cm layer of bottom water.
Before commencing field determinations, electrode performance was tested in the laboratory using a variety of sediment samples. As electrode drift appeared to be a problem, the 35
End piece 5 cm plastic tube
Sediment removed and bung inserted to retain sediment in tube.
Fig. 2.8. Eh SAMPLE CORER.
To Specific Ion Meter
Eh Electrode
•5 cm layer of lake water retained to isolate sediment sample from the air. V Electrode inserted down through water.
■Bung to retain sediment.
Fig. 2.9 Eh SAMPLE AND ELECTRODE 36 time needed to obtain a stable reading was investigated. Two different sediment samples ( clean sand and muddy sand ) each in excess of 5 litre, were collected from Zostera beds, submerged with 5 cm of lake water and returned in plastic containers to the laboratory. There they were puddled and allowed to stand for
7 days to compensate for disturbance during collection. Eh determinations were made by inserting the electrode 2 cm into the sediment, taking care not to introduce air bubbles. Readings were taken at 30 second intervals until the reading was constant for 90 seconds. After each determination, the electrode was washed thoroughly in distilled water, dried with a tissue and inserted into Zo Bell solution to test constancy of response at
+ 230 mV. Before each measurement, the electrode was washed thoroughly with distilled water and dried with a tissue. Five trials were made on each sediment type.
The results obtained are given in Table A2.7 and
A2.8. On this evidence, the field procedure adopted was to obtain two stable readings at 30 sec. intervals.
In the field, simple insertion of the electrode into the sediment produced results that were difficult to replicate for any given sample. Repeated insertions and readings from xhe one sample gave results that at times varied by as much as 380 mV
( Table A2.9 ).
If the sample was carefully mixed using a glass rod, without introducing air, it was possible to obtain results that were much more consistent ( Table A2.10 ). Consequently all Eh measurements given in Tables A2.2 to A2.5, for sediments taken from Zostera/Ruppia beds, were made after carefully stirring the sediment sample. The values given are the mean of 2 values ( to the nearest 5 mV ) observed from three samples at each site. 37
2.3 WATER.
2.3.1 Previous Data.
There were few records of water quality of Illawarra
Lake at the commencement of this study. On 15. 8.1962, the
Wollongong City Council "began intermittent sampling of lake water to determine E. coli contamination. This programme was expanded in
1970 to include analyses of pH and nitrites ( sic ) and then again in 1972, to include ammonia, temperature, sulphate, sulphides, detergents and phosphate. Although sampling was irregular and the analyses are often incomplete for one or more parameters, contamination from domestic sewage was established clearly. E. coli populations commonly were too numerous to count, ammonia and phosphorus concentrations often exceeded 1 mg/l with a maximum reported level for phosphorus of 6 mg/l near Brooks Creek on
30.10.72 ( Wollongong City Council Files, Table A1.2 ).
The Electricity Commission of N.S.W. collated their climatic and limnological data for the Tallawarra area, covering the period 1950 to 1971 ( N.S.W. Electricity Commission, 1971 )•
This data included precipitation, air temperature, wind, water temperature,water level and salinity.
During 1972, Dr. J. Ellis, and later S. Kanamori, both of the Wollongong University, commenced gathering data on salinity, temperature, dissolved oxygen, turbidity, nitrate, phosphate phosphorus and total phosphorus of lake water. (Table
A2.ll )
Further analyses of lake waters were begun by the
State Pollution Control Commission ( S.P.C.C.) in May 1973.
Although analyses were intermittent and the location of sampling sites varied, valuable corroborative data was produced. The data collected included water depth, surface temperature, salinity, 38
pH, suspended solids, nitrite and nitrate nitrogen, total phosphorus,
B.O.D., E. coli, dissolved oxygen and chlorophyll "a" ( Table A2.12 ).
Lake Water Level, Lake water level fluctuates, at times
dramatically, over a 2 m range. Rises of about 1.5 m have been recorded
in three days ( July, 1973 )# when 236.8 mm rainfall was registered
at the Wollongong University Climatological Station, resulting
in a doubling of lake volume. Similar floods occurred in 1919# 1943
and 1939 ( Soros-Longworth and McKenzie, 1976 )• Tallawarra records
for the period 1966 - 1970 revealed the average variation in lake
level during any one year was about 60 cm; the maximum variation
was 74 cm and the minimum rise and fall during any one year was
51 cm ( Table A2.13 )•
Salinity. Lake level fluctuations, as influenced by
rainfall, stream flow and evaporation, are reflected in marked
salinity variations. Ellis and Kanamori ( 1976 ) reported good
negative correlation between surface salinity and rainfall during
the previous 7 days. Salinity records ( N.S.W. Electricity
Commission ), for the period 1957 to 1963 show that lake salinity
varied erratically within the range 4 ( Nov. 1961 ) to 39
( April 1957# August 1957 and February 1958 ). During that period,
lake salinity fell by more than 10 io , within two weeks, on six
occasions ( Table A2.14 )• The most dramatic change was approximately
19 %o in less than a week,during November 1961. Salinity variability
and expected frequency are given in Table A2.15 and Fig. 2.10.
Measurements by Kanamori ( 1976 ) during the period
7. 4*1972 to 21. 1.1974 ( 25 samplings at 10 stations ) revealed
a usual surface salinity of 23 to 24 io and a usual bottom
salinity of 24 to 26 %o . The range in surface salinity was 8.1
to 32.6 c/oo while bottom salinity variation was 12.1 ioo to 32.9 i°*> •
Wood ( 1964 ) reported a salinity determination of 42 i>o for 39
40 |
Time ( /6 )
Fir;. 2.10. THE 'jo TIMJ-: THAT A SALINITY VALUE WAS EQUALLED OH EXCEEDED. • Electricity Commission continuous data ( 1937 - 1963 )
A Kanamori discrete data ( 1972 - 1973 ) 40
Illawarra Lake,
Equilibration between bottom and surface salinity, even after flooding, occurred within 2-3 weeks and at times more rapidly when the flooding was coincident with strong winds.
The lack of persistent salinity stratification was shown by an observed difference between surface and bottom salinity, at any one site, within the range 0.07 $0 to 2.91 %o • Only slight salinity differences were observed between the western side
( which receives influent of fresh water ) and the eastern side
( which receives seawater ) of the lake. On only one occasion during the study by Ellis and Kanamori was a site difference of
4 °/oo observed. The salinity difference at various sites within the lake was usually less than 2 %o and was often less than 1 %o
This similarity in salinity was attributed to the fact that the eastern side of the lake is more shallow than the western side, and hence a given volume of freshwater inflow would have a maximum dilution effect upon the eastern shallows, despite sea water inflow.
Temperature. Surface water temperature was monitored discontinuously, in Yallah Bay, by the N.S.W. Electricity
Commission from 1950 to 1970. During that time, the observed range was 29°C ( February 1968, January 1969* and February 1970 ) to 9°C ( July 1951 )• Annual maxima and minima are given in
Table A2.16, while the temperature variability, which shows that for the greater part of the year the surface temperature falls within the range 15 to 25°C, is given in Table A2.17 and Fig. 2.11.
Temperature measurements by Kanamori ( 1976 ) during
1972-1974* involving 25 samplings at 10 stations, revealed a maximum surface ( 20 cm ) water temperature of 29.9°C ( 6. 2.1973 ) and minimum of 11.2°C ( 29. 7*1972 ). These data also show that 20 40 60 80 100
Time ( °/o )
Fir:. -2.11. THE c/> TIME THAT A TEMPERATURE WAS EQUALLED OR EXCEEDED. • N.S.W. Electricity Commission continuous data for year’s 1950, 1951* 1966 and 1967* A Kanamori discrete data ( 1972 - 1973 ) 42
variation in surafce temperature over the lake is: usually small,
A range of surface temperature exceeding 4°C was observed on only 2 occasions, > 3°C but < 4°C once,^> 2°C but
1°C but<'2°C on 11 occasions. Even though the hot water outlet from
Tallawarra Power Station enters the lake on the southern side of
Yallah Bay, the temperature of the bay water was only slightly higher than the rest of the lake. The Kanamori ( 1976 ) data show that in 20 surveys the highest lake temperature was recorded in Yallah
Bay on 8 occasions, off Mullet Creek 7 times, off Macquarie Rivulet
4 times, off Primbee twice and once in Tuggerah Bay, The western side of the lake was often about 1°C warmer than the eastern side.
The observed differences between surface and bottom temperatures were in the range 0.1 to 0.8°C. That study also revealed that the lake temperature was little affected by the sea, with the lake being up to 9°C warmer in the summer and 5°C cooler in the winter. The average surface water temperature for 1972-73 was
18.5°C. A strong positive correlation ( 0.958 ) was reported between surface water temperature and the mean air temperature for the previous seven days.
Turbidity. Turbidity measurements by Kanamori ( 1976 ) based upon filtration and weighing of 7 samplings from 12 stations, during 1973-74» gave a range of suspended matter from 1.0 to 29.6 mg/l, with a mean of 7*1 mg/l. Concurrent determinations of seawater gave a mean of 1.7 mg/l. Samples from stations on the western side of the lake gave mean levels of suspended matter almost twice the values from stations on the eastern side ( 8.3 - 10.8 mg/l and 5.0 to 5.4 mg/1 respectively ).
Total Phosphorus and Nitrates. Seven samplings, from 12 stations, by Kanamori ( 1976 ) during the period JO. 5.1972 to
23.lO.i975, revealed a range of phosphate phosphorus of 2.1 to 68.5 }ig/l 43
and a total phosphorus range of 4*0 to 145 }ig/l* No seasonal pattern was apparent. Some very high concentrations of total phosphorus, up to 5f600 >ig/1 were observed in small creeks draining from non-sewered urban areas. The nitrate levels of the lake water were determined concurrently and were found to be low throughout the year, with a weighted mean value of 2.0 >ig/l. There has been a regular joint occurrence of high E. coli contamination with high concentrations of phosphorus and nitrates in streams draining from unsewered urban areas of the lake catchment. This has established that much of the nutrient inflow to Illawarra Lake is derived from domestic effluents and sewage ( Harris, 1976 ).
Dissolved Oxygen. Determinations of dissolved oxygen by
Kanamori ( 1976 ) revealed a range for surface waters of 81 - 108 % saturation and for bottom waters of 75 - 131 % ol saturation. It was concluded that the lake was well oxygenated.
2.5*2 Salinity.
Salinity determinations in the present study were made in the field and in the laboratory, using a combination chloride electrode ( Orion No. 96-17 ) and a specific ion meter ( Orion
Model 407A ). The chloride electrode was calibrated against normal and lO*"1 normal seawater, and regularly checked in the field. The concentration of chloride in these solutions was determined by the titration of a standard A.R. grade silver nitrate solution with
seawater. This reaction was monitored using a mercurous sulphate reference electrode ( Radiometer K601 ) and a silver/silver sulphide electrode ( Orion Model 94-16 ) coupled to a digital ion activity meter ( Philips PW9414 ) • Reaction end-point was determined graphically.
The salinity of lake water was determined on 14 occasions, for 4 stations, during the period 7. 6.1975 to 14. 2.1976. 44
The 4 stations were the sites of benthic flora biomass surveys and transplant experiments ( Fig, 2,1 )„ These data are given in
Table A2.18.
In association with a selection of sites for a survey of benthic macrofauna, salinity measurements, on inflow and outflow tide, were taken at a number of sites. Subsequently, heavy rain, registering 236 mm at the Wollongong University Climatological
Station resulted in a rise of 1,5 m in the lake level. As a consequence, the salinity in Griffins Bay fell from 28 to
12 °Joo in ten days. In the following 8 weeks, surface salinity increased to 31 %o • These salinity changes were monitored on three occasions at the 4 sites chosen for the benthic macrofauna survey and the data are presented in Table A2.19 and Fig. 2.12.
The dramatic changes in salinity in Griffins Bay, which is distant from the entrance channel,is demonstrated clearly. The greater recovery time for Griffins Bay is also apparent.
As Zostera was observed growing in Mullet Creek and
Hooka Creek, measurements of salinity were made in these streams.
During periods of high rainfall, salinity in both streams was less than 0.5 °/>e ( eg. late June, 1975 ) • Owing to the presence of an extensive shallow delta at the mouths of these streams, and blocking sand bars in Mullet creek, lake water penetrates only slowly, even during periods of low stream flow. A survey of salinity gradients along these streams was conducted in October, 1975* The rainfall for the previous 30 days, as recorded at the Wollongong University
Climatological Station was 58 mm. At the time of the survey, there was no detectable flow in either stream. The salinity of the adjacent lake water, beyond the delta, was 29.9 • In Mullet
Creek, Zostera was observed flowering in water of 6.2 °/oo and in
Hooka Creek in 3*5 i°o salinity. As the 70 year average rainfall for 45
Rainfall previous 30 days Days since rain 4. 6. 75 0 mm 54 29. 6. 75 252 mm i
O 0 0) 0 Entrance Back Bevans Griffins Channel Channel Island Bay Sites
FifV, 2.12. SALINITY VARIATIONS IN RELATION TO TIDAL PLOW AND RAINFALL - ILLAWARRA LAKE. 46
September is 68 mm, the salinity observed on this occasion could fairly be considered to be normal or slightly higher than average for that time of year. The salinity gradient observed in this survey is shown on Fig. 2.13.
2.3.3 Temperature.
Lake surface water temperature measurements were made at a depth of 20 cm, using a standard 50°C mercury thermometer, graduated in l/lO°C. Temperature uniformity along the eastern seagrass beds at the times of the biomass surveys, is shown in Table A2.20 to
A2.22.
Measurements of surface water temperature, made in the deep areas of the lake, do not indicate conditions in seagrass areas. As one wades through Zostera beds, the temperature difference between the surface and bottom water, and the difference between bare sand areas and seagrass colonised areas, are sufficient to be detected by the skin.
Table A2.23 gives the temperature measurements recorded in Koonawarra Bay, taken at 5 m intervals, showing the typical surface temperature gradient observed across a weed bed, from 60 cm water, with submerged Zostera, to emergent Zostera, in 35 cm water.
The air temperature was 22°C at 11.50 hours when the measurements were made, while the surface temperature of the open water in
Koonawarra Bay was 20.2°C. These data show a variation in surface temperature of 3.5°C over a distance of 45 m, and that the temperature over seagrass growth was higher than over bare sand.
Table A2.24 shows a vertical temperature gradient of 6°C in an emergent Zostera bed, recorded at 11.30 hours, in 20 cm water, in Koonawarra Bay. The air temperature was 23°C.
The hot water discharge from Tallawarra Power Station enters the lake via an outlet channel that is separated from Yallah 47
Hooka Creek
/Panic Trap Blocking submerged sand, bar
Kostera
Salinity • Partially emergent delta ...
Mullet Sostera Creek
Submerged delta ,
Illawarra Lake ILLAWARRA LAKE
Fig. 2.1-j. SALINITY GRADIENTS IN MULLET CREEK, TANK TRAP AND HOOKA CREEK - 2.10.75 48
Bay by a man-made, rock training wall. The water in this channel is commonly 4° to 6°C wanner than the water in Yallah Bay, As the electricity output of Tallawarra Power Station varied markedly, the volume of hot water discharged, and hence the temperature of the outlet channel, also varied markedly,
2.3.4 Nutrients - Total Phosphorus.
Water samples were collected in the field, frozen in dry ice and stored below - 18°C until analysed. In the laboratory, the samples were thawed quickly in warm water and filtered through a No. 541 Whatman filter paper to remove suspended solids. One gram of potassium persulphate was added to 100 ml of the filtrate which was then heated in a boiling water bath for 1 hour. After cooling to room temperature, the volume was made up to 100 ml with distilled water. The sample was then analysed for phosphate phosphorus as described in section 2.2.4-
Total phosphorus analyses of lake water were conducted in association with surveys of the biomass of benthic flora. The results of these analyses, which show a range of 16.5 to 73 }igAf
are given in Tables A2.20 to A2.22. These data also show considerable variation in total phosphorus concentration ( 27.7 to 55*7 )igA>
transect 1 and 16.5 to 49.9 ,pgA transect 3 ) within a seagrass bed.
2.3.5 £H.
The pH of lake surface water was measured in situ,
using a specific ion meter ( Orion Model 407A ) and a combination
pH electrode ( Orion No. 91-02 ) that had been calibrated as
described in Section 2.2.5. These data, as presented in Table A2.20
to A2.22 show a range of pH for surface lake water of 8.0 to 8.4.
This compares with a range of 7*4 to.8.9 as reported by the State
Pollution Control Commission in their more extensive measurements
( Table A2.12 ). Both sets of data indicate that the normal range of
pH for Illawarra Lake would fall between pH 8.0 and pH 8.4» which is 49 comparable with Macquarie Lake ( Baas Becking, 1959 )•
2.5.6 Eh.
The Eh of lake surface water was measured in the field using a specific ion meter ( Orion Model 407A ) and an Eh combination electrode ( Orion No, 96-78 ). Standardisation of the electrode was as described in Section 2.2.6.
As shown in Table A2.20 to A2.22 the observed Eh values of lake surface water fell within the range + 510 mV to + 550 mV, which is comparable with Macquarie Lake ( Baas Becking, 1959 ).
2.5.7 Turbidity.
Turbidity measurements of the water of Illawarra Lake were made in the field using the Secchi disc and in the laboratory using a turbidimeter ( Hach Model 2100 A ). All water samples were
agitated in an ultrasonic vibrator for 5 minutes. This treatment is
essential to produce an homogeneous suspension free from dissolved
air. The presence of air bubbles in the sample results in spurious
readings on the turbidimeter. Surveys of turbidity were conducted during 1972 and 1975. Measurements in the 1972 survey were made with
the Secchi disc only. In the 1975 survey, both the Secchi disc and the
turbidimeter were used. The 1972 survey included sites throughout the
lake but the 1975 survey was focused on the eastern seagrass beds
( Fig. 2.1 ). The results of these surveys are shown in Tables A2.25
and A2.26. Secchi disc extinction occurred within the limits 0.8 to
2.6 m and usually between 1 and 2 m. Turbidity as measured on the
turbidimeter was usually within the limits 0.25 to 5 national turbidity units ( N.T.U. ).
Initially water samples for analysis on the turbidimeter were collected only from sites on the outer edge of the seagrass beds.
Later it became apparent that the turbidity within the seagrass bed was often less than in the deeper areas of the lake. This difference 50 is shown in Table A2,27, including turbidity determinations of water from the outer edge and from the centre of the seagrass beds.
Occasional measurements, in the narrow fringing seagrass beds on the western side of the lake, revealed that within 10 minutes of a strong southerly change acting upon the lake, the turbidity inshore could change from 2 to 40 N,T.U, as determined on the turbidimeter. 51
2.4 CONCLUSIONS.
From the analyses of particle size, as given in Table A2.1 it may be seen that the greater part of the vegetated zone of
Illawarra Lake consists of sediments with a high sand content.
Nineteen of the 21 sites yielded greater than 80 % sand, while all of the eastern seagrass bed had a sand content in excess of 90
Sediments with a silt and clay content in excess of 20 a/o were found in the sheltered water of Koona Bay and in Koonawarra Bay at a site of recent deposition ( sites 5 and 9» Fig- 2.1 ). This is consistent with the findings of Roy and Peat ( 1975 ) and Jones
( 1976 ) who also noted the occurrence of finer sediments in sheltered bays, in areas of recent deposition adjacent to streams, and in deeper water beyond the seagrass zone.
The general low proportion of fines within the vegetated zone is attributed to the turbulence of the lake. Wind-induced wave action constantly reworks the shallow sediments, keeping much of the fines content in suspension. Final deposition occurs in deeper areas only.
In the extensive Zostera zone on the eastern side of the lake, turbulence is much reduced, and deposition of fines might be expected. Wood ( 1964 ) and Brown ( 1969 ) both suggested that
Zostera could act as a trap for suspended fines. From the evidence of Leopold ( 1971 ) on the effects of development upon stream flow and erosion, and the clearing of catchment forests that has occurred
since the turn of the century, one would also expect an increase in lake turbidity and sediment deposition during that time. Sediment profiles, to a depth of 40 cm, were examined in one area only, and
these did show a higher proportion of fines in the upper layers
( 0 - 5 cm ) than in the deeper layers ( Table A2.5 )• This is consistent with a recent increase in sedimentation of fines but no 52
firm conclusion can be drawn from this data as the possible effects of bioturbation are acknowledged.
Correlation coefficient product matrices were calculated for
Eh and pH, as observed in the several sediment surveys, according to
Pearson ( Moroney, 1957 )• The formula used was; S xy - jg x S Y
The coefficients give a measure of the probability that two factors have a functional relationship and are presented in Table A2.28.
High positive correlations were observed between >6 fines and % organic carbon ( 0.52 to 0.93f X 0.87 ), % fines and total phosphorus ( 0.60 to 0.81, X 0.65 ) and % organic carbon and total phosphorus ( 0.50 to 0.88, X 0.83 )• These relationships are plotted in Fig. 2.14 to 2.16.
Lower, negative correlations were found for the relationships
% fines and pH ( - 0.45 )* % organic carbon and pH ( - 0.27 )» total phosphorus and pH ( - 0.35 )» % fines and Eh ( - 0.59 )*
% organic carbon and Eh ( - 0.62 ) and total phosphorus and Eh
( “0.53 )• These Eh relationships are plotted in Fig. 2.17 to 2.19.
The correlation between pH and Eh for all sediment samples was 0.24 and was therefore insignificant.
The somewhat poorer correlations of % fine/total phosphorus and % organic carbon/total phosphorus in Griffins Bay, as compared with the other sites, is attributed to the higher coal wash content of the sediments of Griffins Bay. Coalwash has been used extensively as a fill material around the shore of the bay. In the sediment, the coal wash contributes to the fines and carbon fraction but neither contributes to, nor adsorbs phosphates to the same degree as do Fines ( y ; particles< 63 Jim diam Fig.
2.14 Q ▼ A ■ O •
.
Mean THE Whole Eastern CARBON Bevans Griffins Bevans Organic 53
RELATIONSHIP of
CONTENT Lake
Island Island
Carbon all Seagrass Bay
Survey
Values,R
Transects
Transects
Dredge OF (
°/o Bed BETWEEN X@^R SEDIMENTS. )
Biomass 0.87 Site
X@,R X© 0.95
FINES #
R
O Survey
0.75 .52 AND
ORGANIC X(o)^R
0.81
54
Total Phosphorus ( P/g sediment ) Pig. 2.15* THE RELATIONSHIP BETWEEN THE TOTAL PHOSPHORUS AND FINES CONTENT OF SEDIMENTS. • Be vans Island Transects X^), R 0.81 A Griffins Bay Transects X(2)f R 0.60 O Eastern Weed Bed Biomass Survey X(o), R 0.77 ■ Bevans Island Dredge Site (Sh Mean of all Values, R. 0.65 Higginson Values, Tuggerah Lakes tal Phosphorus ( pig ?/g Sediment Fig.
2.16 @ O ■ ± • .
Mean Eastern THE Bevans Griffins Bevans AND
RELATIONSHIP ORGANIC 55 Value
Island Island
Seagrass Bay
all
CARBON
Transects
Transects Dredge Sites,
Beds BETWEEN
CONTENT
Site
R Biomass
X( x(*)*R
a TOTAL 0.83 ),R
OF
0.50
0.85 Survey SEDIMENTS. PHOSPHORUS
X(o),R
0.88
56
( Bare sand area in Zostera bed )
• O O (J
-100
-120
Organic Carbon ( (/o ) Fig, 2.17. THE RELATIONSHIP BETWEEN ORGANIC CARBON AND Eh OF SEDIMENTS. • Bevans Island Transects X(*),R - 0.45 A Griffins Bay Transects X@,R - 0.51 O Eastern Seagrass Beds Biomass Survey X(o),R - 0.60 ■ Bevans Island Dredge Site Mean of all values,R - 0.62 57
Bare sand area in Zostera beds )
-100
-120
-100
40 60 80 100 Total Phosphorus ( yxg F/g sediment ) Fig. 2.18. THE RELATIONSHIP BETWEEN Eh AND TOTAL PHOSPHORUS CONTENT OF SEDIMENTS. • Bevans Island Transects X - O.46 a Griffins Bay Transects XQ/1 - 0.11 O Eastern Seagrass Beds Biomass Survey X (o^R - 0.50 ■ Bevans Island Dredge Site Mean of all sites, R - 0.55 58
( Bare sand area in Zostera bed )
-100
-120
-180
Fines ( $> ) Fig. 2.19. THE RELATIONSHIP BETWEEN Eh AND FINES CONTENT OF SEDIMENTS. • Bevans Island Transect X Qjl - 0.45 a Griffins Bay Transect X£)*R - 0.50 O Eastern Seagrass Bed Biomass Survey X(6)jR - 0.58 ■ Bevans Island Dredge ©Mean of all Values,R - 0.59 59 clays and humus. The ability of clays to adsorb phosphate was investigated by Jitts ( 1959 ) who demonstrated that under aerobic conditions, 0.4 g ( dry weight ) of mud could adsorb about 0.05 mg phosphate in less than 30 minutes.
The negative correlation between % fines and Eh ( X - 0.53 ) is not strong, but the Eh factor needs to be discussed first to put into perspective subsequent discussion of % organic carbon and total phosphorus content of the sediment.
Whitfield ( 1969, 1971 ) stated that the interpretation of
Eh measurements in natural aqueous systems is difficult because of problems associated with the technique of measurement, poisoning of the inert metal electrode and the complex thermodynamic behaviour of the environment. However, his views agree with those of Baas Becking and McKay (1956 ), Baas Becking ( 1959 )» Mankeim ( 1961 ), Berner
( 1963 ) and Wood ( 1964 ), that Eh is a useful semi-quantitative indicator of the degree of stagnation. Whitfield ( 1971 ) also suggested that differences in Eh less than 50 mV should not be regarded as significant. The field technique used in this study to obtain replicate results, and to check upon electrode poisoning, have been discussed in Section 2.2.6.
The third problem, the complexity of thermodynamic reactions in estuarine sediments, is beyond the control of the investigator.
Whitfield ( 1971 ) stated that several hundred reactions may be involved in sediment redox reaction and not all of these will be in equilibrium with the system, or at the electrode surface. Further, as the redox potential depends upon the ratio of oxidised and reduced reactants, it does not indicate concentration. Consequently, a system may be poorly buffered, so that its redox potential may be altered greatly by small additions. Of reactants of opposite potential. In addition, many redox reactions are bacterially mediated. Great care 60
must be taken not to introduce air into the sediment during redox determinations.
In spite of the complexity of the system, Whitfield ( 1969*
1971 ) and Baas Becking and McKay ( 1956 ) agreed that there was a
2- close relationship between Eh and pS indicating that under reducing conditions, a simple redox couple, H^S ( SH ) ^ S,
( Baas Becking and McKay, 1956 ) controls the potential of the platinum electrode. Berner ( 1963 ) stated that the Eh of many
sediments containing H^S is controlled by the reversible J cells;
HS aq ±5, S° rhomb. + H+ aq + 2 e* , or S2” aq ^ S° rhomb. + 2 e •
When a sediment contains adequate organic matter, and there is little movement of water, bacterial respiration may so deplete the supply of dissolved oxygen that sulphate bacteria become active. Sulphate reduction, which can occur at an Eh up to + 110 mV
( Baas Becking, 1959 ) quickly reduces the redox potential.
Investigations by Wood ( 1964 ) on the sediments of Macquarie
Lake revealed that whenever the Eh was below 0, the sulphate- reducing bacterium, Desulfovibro could be cultured from the
sediment.
Nutrient flow is also influenced by the Eh of the
sediment. As the Eh becomes negative, free hydrogen sulphide may be generated, the pH will drop and phosphoric acid may be released from insoluble ferric and calcium phosphate ( Wood, 1964 )•
Consequently, phosphates that axe precipitated under oxidising conditions, may be mobilised in reduced sediments. The Eh status may also influence the flow of nitrogen between the sediment and the lake water. Under reduced conditions, the nitrogen content of organic remains is converted to the ammonium ion, through ammonification ( Riley and Chester, 1971 )• The NH+ content of the sediment rapidly reaches equilibrium with the overlying water, which 61
if oxidised, will convert the NH* to NO, as it moves out of tne 4 3 anaerobic sediment. Garetz ( 1973 ) suggested that this process could produce sufficient nutrient to sustain algal blooms. The low mean nitrate content of Illawarra Lake waters ( 2 )xg/l ) indicates that either the process proceeds slowly or that the released nitrate is absorbed rapidly by the abundant planktonic and benthic flora.
Baas Becking ( 1959 )•> in his study of Macquarie Lake, reported an Eh range for sediments of - 300 mV to + 600 mV and a pH range 5 bo 9«5» while the Eh range of lake water was + 180 mV to + 450 mV and the pH was 7*4 to 9*2. His figure showing these relationships is reproduced in Fig. 2.20 with the values from
Illawarra Lake added for comparison, showing the relative similarity of the Illawarra Lake sites, as compared with the diversity observed in Macquarie Lake.
Garetz ( 1973 ) stated that the Eh of lake water is relatively insensitive to dissolved oxygen and remains relatively constant down to 0.1 % of oxygen saturation. Consequently, high positive Eh values do not necessarily indicate high levels of dissolved oxygen.
The observed pH range of both the sandy sediments ( 7»4 to
8.0 ) and the lake water ( 8.0 to 8.4 ) was narrower than that observed by Baas Becking ( 1959 ) in Macquarie Lake which included some mud sites. At the time of the Illawarra Lake determinations, salinity levels were high ( 29*5 to 32.7 %o ).
At this salinity range, the buffer capacity of the water is higher than at lower salinities owing to the carbonate/ bicarbonate content of seawater. Consequently, little variation in lake water pH would be expected.
The sediments in the areas examined had a high density of 62
+600
+500 Illawarra Lake, all values
+400
+500
+200
+100
-100
-200
-500 4 5 6 7 8 9 10 pH. Fig. 2.20. THE RELATIONSHIP BETWEEN Eh AND pH OF ILLAWARRA LAKE SEDIMENTS AND WATER ( AFTER BAAS BECKING, 1959, SHOWING MACQUARIE LAKE VALUES). # Bevans Island Transect ▲ Griffins Bay Transect
O Eastern Seagrass Bed Biomass Survey 65
burrowing macrofauna ( Section 5 ) which would allow some exchange
of water between the sediment and the lake. This would also be
enhanced by the natural porosity of sandy sediments. Further, as
all sediments examined contained some shell fragments, the pH
range observed would seem reasonable.
In this study, pH measurements were made in association
with benthic flora biomass surveys, and indicate the degree of
uniformity at those times. They were not intended to indicate
the range that may be observed; over a longer period, in other
areas of the lake, or under different seasonal conditions.
Higginson ( 1965* 1971 ) reported that an increase in the
clay content of sediments was associated with an increase in
organic matter, nitrogen, potassium, magnesium, iron, total
phosphorus and total exchangeable cations. In Illawarra Lake
there was a positive correlation between the proportion of fines
( silt and clay ) the percent organic carbon and total phosphorus
in the sediment. If the other relationships observed by
Higginson ( 1965, 1971 ) also apply in Illawarra Lake,then the
generally low proportion of fines would result in a relatively
low nutrient status in the vegetated sediments of this lake.
The nutrient status, and particularly the sediment
phosphorus content was less than that observed in some other lakes
because of the low ion absorptive capacity of the sandy sediments.
Table A2.29 gives the comparative phosphorus content of sediments
of several lakes, most of which are freshwater. Little comparative
data is available from other N.S.W. coastal saline lagoons.
Higginson ( 1971 ) reported for Tuggerah Lakes a mean total phosphorus content for sand sediment ( X 88.1 °/o coarse sand and
8.8 % clay ) of 50 i*g P/g sediment, for loamy-sand sediments
( X 81.8 (,jo coarse sand and 15.1 $ clay ) of 90 )ig P/g sediment, 64
and for clay sediments ( X 4*2 fo coarse sand and 72.5 clay ) of
290 yg P/g sediment. The values for sand and loamy-sand sediments of Tuggerah Lakes are comparable with those of Illawarra Lake and have been included in Pig. 2.15 for comparison. Determinations of the total phosphorus content of deep muds were made of samples from off Primbee, beyond the Zostera zone. These yielded 520 and
675 iig P/g sediment ( X ^ 600 pg P/g ).
In spite of the lower phosphorus content of Illawarra Lake sediments, by comparison with those of the lakes cited in Table
A2.29, they contain vast reserves of phosphate. Consideration here must be given to both sediment and water phosphorus.
Determinations of Illawarra Lake total phosphorus concentration revealed a range 16.5 to 75 Hg P/l which is in fair agreement with Kanamori ( 1976 ) ( 4*0 to 145 yg P/l, X 46 yg P/l ) and the State Pollution Control Commission ( unpublished,
10 - 114 yg P/l )• Total phosphorus concentrations reported for waters from other N.S.W. coastal lagoons were Macquarie Lake
22.2 to 55*2 yg P/l ( Spencer, 1959 ) and Tuggerah Lakes, 6.4 to
107 >ig P/l ( Higginson, 1971 )• The concentration of total phosphorus in Illawarra Lake was usually beyond the level needed for incipient eutrophication, defined in Higginson ( 1971 ) as
30 pg p/i.
From the data gathered, one may estimate the total phosphorus reserves of Illawarra Lake.
Given that the lake volume » 6,2 x 10 m and that the X total phosphorus ** 46 jig P/l then the total phosphorus reserves in the lake waters 2.8 x lCrkg. 2 Given that the area of sand sediment in the lake^ 11.0 Km and the X total phosphorus in sand sediments « 80 yg P/g then the total phosphorus reserves in the top 10 cm of lake sandal.1 x 10 Kg. 65
2 Given that the area of fines in the lake^ 22 Km and the X
total phosphorus in fine sediments^ 600 pg P/g then the total c phosphorus reserves in the top 10 cm of lake finest 1.7 x 10 Kg.
Thus the total phosphorus reserves in the top 10 cm of
sediments for the whole lake^? 1.8 x 10^ Kg.
The ratio of total phosphorus in lake water to lake sediments
« 1:600.
As benthic flora grows only in the shallows which represents 2 about 25 °/o of the total lake area or ^ 8 Km , total phosphorus in the benthic flora zone & 8 x 10^ Kg.
The ratio of total phosphorus in lake water to sand sediments
supporting benthic floral 1:50.
The ratio of the mass of total phosphorus in equal volumes of lake water and sand ^ 1:4500.
These several estimates are not considered to be more than crude approximations but they do indicate an abundance of phosphorus, and the improbability that this nutrient would be limiting to plant growth.
Studies reported by Hutchinson ( 1957 ) and Serruya ( 1971 ) demonstrated that in oxygen rich lake waters, soluble phosphates are precipitated as insoluble iron phosphate, becoming adsorbed readily to clays. Under reducing conditions by contrast, sulphur bacteria generate H^S, which precipitates the iron as black FeS, thus liberating the phosphate.
In sediments of the Zostera beds of Illawarra Lake, the observed Eh was usually in the range - 50 mV to - 150 mV, with a mean of - 100 mV, and therefore continuous flow of phosphorus from the sediment to the water could be expected. The sediments of
Griffins Baytwhich were more reduced ( X Eh - 140 mV ) than those of Bevans Island ( X Eh - 85 mV ) and with a distinctly more 66
sulphurous aroma, could be expected to have a lower total phosphorus content than those of Bevans Island. This was not the case. The mean values obtained for total phosphorus were Griffins
Bay 84 pg P/g and Bevans Island 69 jag P/g. If the phosphorus were free to flow from the sediment to the water, one might expect to find a close correlation between the total phosphorus content of the sediment and that of the overlying water. The calculated correlation coefficients given in Table A2.28 show this not to be the case. As the lake is very turbulent,perhaps no such relationship could be detected even if the phosphorus flow occurred.
This paradox could be explained by the observations of
Kanamori ( 1976 ) that the bottom waters of Illawarra Lake are well oxygenated. In situ inspection of sediments, even in the deeper parts of the lake, using SCUBA gear, revealed that the surface layer was pale grey in colour, while the sediment 2 - 3 mm beneath the surface was black. When fine sediments were brought up from deep water and puddled, they were uniformly black. If allowed to stand for a few days covered by lake water that varied in depth between
1 cm and 30 cm ( as observed in the laboratory ), the surface colour faded to a pale grey, indicating the absence of the reduced
PeS and therefore an oxidised layer.
These several observations indicate that under usual lake conditions, the surface of the sediment is oxidised, thus preventing the direct flow of phosphorus, from the sediment, into the lake water.
At times, there is a difficulty in identifying functional relationships simply by considering correlation coefficients. The correlation between °/o fines and total phosphorus content of the sediment is consistent with the findings of Jitts ( 1959 )• The correlation between organic carbon and total phosphorus ( X 0.83 ) 67 indicates that phosphorus could both/either be adsorbed to/or be a component of humus, both of which are known facts. The negative correlation between organic carbon and Eh ( - 0.62 ) indicates that the sediment becomes more reducing as the organic carbon content increases. This is consistent with the notion that bacterial respiration would readily produce reducing conditions in sediments rich in organic carbon. The negative correlation between total phosphorus and Eh ( - 0.53 ) while low, does suggest that the total phosphorus content of the sediment increases as the sediment becomes reduced. As there is no elucidated chemical explanation of such a trend, and as the evidence presented points to the contrary, it is concluded that functional relationships exist between fines/total phosphorus, organic carbon/total phosphorus, and organic carbon/Eh,but the correlation total phosphorus/Eh is coincidental.
The salinity range, and rate of change reported in this study, are consistent with the observations of Kanamori ( 1976 ) and the
N.S.W. Electricity Commission ( 1971 )• These observations add to the data that shows that the salinity of Illawarra Lake fluctuates widely ( 20 in this study ) with periods of rapid decline coincident with high rainfall, followed by periods of slower increases. These changes are more marked and prolonged at sites remote from the entrance channel. The salinity at Bevans
Island was 1 to 5 greater than the salinity at both Griffins
Bay and Yallah Bay during 90 % of the observation time ( Pig. 2.21 ).
For any given sampling run,the salinity in Yallah Bay ( on the western side of the lake ) and in Griffins Bay ( in the north east comer of the lake ) was similar. Both of these sites are remote from the entrance channel and neither one receives water directly from a major stream. The period of high salinity at all 68
Time ( °/o ) Fig. 2.21, THE % TIME THAT A SALINITY VALUE WAS EQUALLED OR EXCEEDED. • N.S.W. Electricity Commission Data A Bevans Island Data ▼ Griffins Bay Data ■ Yallah Bay Data 69
stations was of a higher frequency than the longer term average,
based upon N.S.W. Electricity Commission data, and the range was
less than that of the long term observations.
Turbidity observations during this study indicate that
the waters of the southern end and western side of the lake are more turbid than on the eastern side. This is in agreement with
the findings of Kanamori ( 1976 ). Griffins Bay had a higher
average turbidity than the Zostera zone adjacent to the Windang
Peninsular or Bevans Island. Turbidity within a single Zostera
bed may vary considerably ( 1.5 to 4*0 N.T.U. off Bevans Island )
over a distance of 50
Secchi disc extinction, which is equivalent to the depth at
which between 10 and 15 °/> ( Royce, 1973 ) or 18 - 24 % ( Backman, 1976 )
of solar radiation penetrates, was seldom greater than 2.2 m, but
was often less than 1.5 m. In the most turbid waters,it may be as
little as 0.6 m. The correlation between Secchi disc and turbidity,
as measured in national turbidity units on the turbidimeter,is
shown in Fig. 2.22. While a straight line is fitted to this
relationship, it is appreciated that over a wider range of turbidities
the distribution would probably be parabolic.
Observations in Koonawarra Bay, Yallah Bay and Griffins Bay
have shown that wind - induced turbulence may quickly generate high
levels of local turbidity in the shallows. This effect was greatly
reduced on the Windang Peninsular and Bevans Island Zostera beds,
where the sediments have a lower fines content, and the magnitude
of the plant growth markedly suppresses wave action.
Major increases in the level of lake turbidity are usually
associated with periods of high rainfall,which tends to be the
most significant controlling factor. This relationship between lake
turbidity and rainfall is given in Fig. 2.23* 7 0
3l\2 5
Turbidity Secchi Disc ( m ) Fig. 2.22. THE RELATIONSHIP BETWEEN THE TWO MEASURES OF TURBIDITY. 1. Secchi Station 1 2. Secchi Station 2 3. Secchi Station 3 R = -0.87. 4. Secchi Station 4 5. Secchi Station 5 )
m
H O vn ( 1972 1 — o l o )
mm vji
( Extinction
O Disc
IV) vn Rainfall Secchi vn )
m
O ( vn v>i
1 - l ro vn 71 )
mm M O O ro
( Extinction
vn Disc
M o Rainfall Secchi IV) vn
F ig .2 .2. 5 SECCHI DISC EXTINCTION DEPTH AS A FUNCTION OF 72
The 70 year mean rainfall data,as given in Table A2.30, shows that the months January to May usually experience falls in excess of 100 mm,while the months August to November are markedly drier* The incidence of heavy rainfalls ( Table A2.31 ) also matches this distribution with the exception that occasionally heavy rains and floods occur in June/July. From this data and field observations, one may conclude that the highest levels and most prolonged periods of high turbidity tend to occur during the period December to May*
Changes in sediments,following dredging at Bevans Island, were considerable ( Fig* 2*24 to 2.26 ). The rate and magnitude of the change in surface fines, organic carbon and total phosphorus content suggested that this depression, created by dredging, became a collection/settling site for material from the surrounding area.
Numerous birds, particularly cormorants, were observed to perch upon the stakes used to mark the dredge site. These birds, through their excreta, would have added to the phosphorus content of the sediment.
Changes in the fines, organic carbon and total phosphorus content of the sediments from 10 cm below the dredged surface indicate that some mixing process had been active. Wave action in the area was minimal and would have had a negligible effect at a depth of 60 cm. Further, had wave action been significant, the fines would not have settled. New worm casts and burrows were observed 10 days after the dredge and became numerous during the following month. It is concluded that the observed changes at depth were created by bioturbation.
It is suggested that the rate and magnitude of changes observed at this small site would not apply to a larger site, except as a boundary effect. Consequently, if a larger area were dredged, it is expected that the recovery of nutrient 73
Original surface
Dredged surface
Fines ( % ) Fig. 2.24. FINES CONTENT, SEDIMENT DEPTH PROFILE, BEVANS ISLAND DREDGE SITE.
• io fines pre-dredge A °/o fines 5 weeks post dredge
■ °/o fines 20 weeks post dredge 74
12 5 4 5
Organic Carbon ( % )
Fig. 2.25. ORGANIC CARBON CONTENT,SEDIMENT DEPTH PROFILE, BEVANS ISLAND DREDGE SITE.
• °/o Organic carbon pre-dredge
± °/o Organic carbon 5 weeks post-dredge
■ io Organic carbon 20 weeks post-dredge Sediment Depth ( cm Fig,
2,26 Total .
A ■ •
Phosphorus Total Total Total TOTAL
PHOSPHORUS,DEPTH phosphorus phosphorus phosphorus 75
DREDGE (
ug
P/g
pre-dredge SITE. 20 5
weeks sediment weeks
PROFILE,BEVANS
post-dredge post-dredge
Dredged
Original )
Surface
Surface
ISLAND 76 status would be much slower.
In review, those sediments of Illawarra Lake that support benthic flora are generally sandy, low in organic carbon, reduced and neutral to slightly alkaline. They have a sulphurous odour and contain phosphate reserves greatly exceeding those observed in the lake water. The water of Illawarra Lake is shallow, turbulent and turbid. It is well oxygenated, rich in phosphorus but contains little nitrate. The salinity is highly variable and the water temperature is equivalent to warm temperate values on the open coast ( Knox, 1963 ). There is no marked spatial variation nor persistent vertical stratification in salinity or temperature. 3
BIOLOGICAL FEATURES 78
3.1 INTRODUCTION - OTHER LAKES.
So that Illawarra Lake could be assessed in the broader context of coastal saline lagoons of central and southern N.S.V., eight other bodies of water were examined briefly in this study
( Fig. 1.1 ). Macquarie Lake and the Tuggerah Lakes were visited during September 1972 and January 1975 while Willinga, Toubouree,
Burrill, Conjola, Swan and Wollumboola lakes were observed during
November 1973* Heavy rain had fallen in the two weeks prior to the observation of the southern lakes.
These lakes showed differences in origin, foreshore topography and vegetation, urban and agricultural development of the catchment, sediments, bathymetry, salinity, turbidity, occlusion from the sea, and benthic flora.
The most diverse, and the largest lake, Macquarie Lake, has been described extensively in a series of twelve papers in
Aust. J. Mar. and Freshw. Res. 10 (3)f 1959. Tuggerah Lake, which of the lakes observed most closely resembles Illawarra Lake, was studied by I-Iigginson ( 1965> 1971 )• No further descriptions of these lakes are offered here.
Willinga Lake. Observations of Willinga Lake ( Fig. 3*1 ) were limited to the entrance channel. Boat access to the lake was blocked by an extensive, partially emergent delta, and the surrounding land was marshy and heavily covered with low growing scrub. The water draining from the lake was stained a dark brown colour characteristic of water in which large quantities of plant detritus have accumulated.
On the seaward end of the inlet, Zostera capricomi grew sparsely upon subtidal sand and was free of filamentous algal epiphytes. Enteromorpha intestinalis and Ectocarpus grew sparsely on the intertidal rocks. Near the bridge over the channel, samples 79
Key: Pacific Ocean •\yV Shallows < 30 cm Exposed sand Z Zostera capricorni Z m Zostera muelleri r Ruppia
WILLING A LAKE
Pacific Ocean
Toubouree
i'ir:. r). 2 TOUBOUREE LAKE 80
of Zostera, tentatively identified on root structure as
Z. muelleri, were collected from a colony growing on heavy clay sediments in water 5 to 30 cm deep. Sparse Z. capricomi grew in the deeper water ( 20 to 60 cm ) in association with extensive growths of Ruppia maritima.
Toubouree Lake, Toubouree Lake ( Pig, 3*2 ) was connected to the sea by a 4 km long, shallow entrance channel. Boat access through this channel was obstructed by numerous sand bars and fallen trees. Water depth at the lake end of the entrance channel was less than 20 cm. The lake itself was also shallow; the deepest part recorded was 75 cm, but most had less than 50 cm of water.
On the eastern side, shallows less than 20 cm deep extended almost 100 m into the lake. Turbidity, resulting from suspended fines rather than organic stain, was high, and Secchi disc extinction occurred at about 20 cm. Numerous luderick were brought to the surface in the wake of the outboard motor. The eastern sediments were sandy with little visible organic matter, while those in the lake centre were black and silty but not foetid.
Stony outcrops were a feature of the western foreshores and shallows,
Z, capricomi was the only submerged macrophyte observed growing in the lake. It occurred in small, sparse, isolated clumps, and though free of filamentous algal epiphytes, the leaves were heavily coated with silt, Z. capricomi also formed extensive beds on the sand and mud banks in the inlet channel, and in the shallows at the seaward end of the channel, numerous flowering clumps were observed. At this site, Z. capricomi grew on sand sediments 30 to 40 cm above low tide mark.
Toubouree Lake was fringed by Phragmites, Typha and Juncus, behind which grew species of Leptospermum and Eucalyptus.A small pine plantation had been established at the northern end of the lake 81
Burrill Lake. Burrill Lake ( Fig. 3*3 ) was relatively deep
( 3 m + ) with steeply rising foreshores, much of wnich supported
an open sclerophyll forest. The northern catchment had been cleared
extensively and was used mainly for cattle grazing. Several small,
ephemeral creeks drained into the lake but the mouths of these
streams had been choked with dense growths of Phragmites and Typha.
The water was saline ( 25 %o + ) and moderately turbid,
with Secchi disc extinction occurring at 1.5 m adjacent to the ski
club, at 1 m in the bay opposite Kings Point and at 0.5 m in the
bay to the south of Kings Point. The vegetated sediments in the
shallows were mainly silty, rich in organic matter and foetid.
Z. capricorn!. Z. muelleri and Halophila ovalis were the
only submerged macrophytes observed in this lake. Z• capricomi
occupied extensive beds on the shallow, silty to sandy, sub-tidal
flats in the entrance channel, and occurred as a narrow ( usually
5 m wide ) peripheral growth in the lake proper. The leaves were free of both epiphytes and sediment. Both Z. muelleri and
H. ovalis were observed on gritty sediments, in water generally
20 cm deep, adjacent to the stream mouth at the head of the
lake. H. ovalis was also collected from the bay to the south of
Kings Point, where it was growing on foetid, silty sediments in
1 m of water. Ectocarpus and Cladophora occurred on rocks around the lake edge. Abundant Aurelia medusae up to 5 cm diameter and numerous small tailor fish to 15 cm were observed throughout the lake.
Con.jola Lake. Conjola Lake ( Fig. 3*4 )» like Burrill Lake, was deep ( generally>3 m ) with steeply rising, but more elevated, we11-wooded foreshores. Some of the catchment had been cleared for the village of Yatteyatta, the caravan park at Killamey and for cattle grazing in the upper reaches of the lake and along Conjola Ulladulla
Pacific Ocean
Key: Conjoin Shallows 50 cm Creek
Fi,T. :3. 4. CONJOLA LAJKK. 83
Creek.
The water was saline ( 25 °fc>o + ) and clear, with a Secchi disc visibility in excess of 2.5 m. Sediments sampled from the lower reaches and throughout the entrance channel were sandy while those further up the lake were silty. Some grit and fine gravel deposits occurred in the shallows below Conjola Creek.
As in Burrill Lake, Z, capricomi. Z. muelleri and H. oval is were the only submerged macrophytes observed in Conjola Lake.
Z. capricomi was widely distributed, occupying the shallows in the inlet channel, a narrow vegetated zone ( usually < 5 m wide ) around the lake and on various sediments, including muddy silts, at the mouth of Conjola Creek. _Z. muelleri occurred as a band 1 to 3 m wide in the intertidal zone along the inlet channel and was particularly well developed adjacent to the Council Caravan Park. H. oval is was observed on the gritty to gravelly sediments throughout the lake, with an extensive colony on the shallows (< 30 cm deep ) below the mouth of Conjola Creek. An extensive, degenerating growth of the alga.Chaetomorpha^occurred at this site.
Within the lake, Zostera leaves were generally free of epiphytic filamentous algae or silt. By contrast, in the inlet channel, they were heavily coated with epiphytic animals and various algae, but predominantly Cladophora. Colopomenia sinuosa was also a prominent epiphyte throughout the channel. No animal life was observed in the surface waters.
Swan Lake. Swan Lake ( Pig. 3*5 ) was shallow ( June us grew around the lake margins except where interrupted by small patches of Phragmites australis. The lake bed was mainly sandy or gritty with little visible 84 Pacific SWAN LAKE Ocean Crookhaven Inlet Key: Shallows < 30 cm Exposed sand Zostera capricomi Ruppia Triicclochin procera Lamprothamnion C Chaetomorpha Water depth ( m ) Pacific Ocean Coonemia Creek WOLLUMBOOLA LAKE. 85 organic matter. Extensive areas of exposed rock occurred on the western side, while small areas of dark grey to black,silty sediments were observed adjacent to the entrance of streams. The water was saline ( 25 %* + ) with a Secchi disc visibility of 1.4 to 1.6 m. This lake was remarkable in that its sediments were completely devoid of submerged macrophytes. Wollumboola Lake. Wollumboola Lake ( Fig. 3*6 ) was shallow, with a maximum depth of 2.1 m. It had been cut off from the sea for the previous three years, during which time its salinity had fallen to less than 10 . The sand bar between the lake and the sea was narrow, so that at low tide, water could be seen to seep through the bar, from the elevated lake into the sea. Throughout most of the lake, the water was too clear for Secchi disc extinction but visibility at the mouth to Coonemia Creek was 1 m. The sediments were sandy in the east and silty in the centre and western side of the lake. The submerged vegetation of this lake contrasted sharply with that of the other lakes observed. Vast areas of its bed, where the water was deeper than 1 m, was covered by a continuous meadow of the charaphyte. Lamprothamnion papulosum. This alga grew to almost 1 m in the deeper water and usually only to within about 1 m of the surface. It varied in colour from dark green to pale yellow. The shallower areas (<1 m ) and particularly the eastern sands, were colonised by an association of discontinuous Ruppia maritima and abundant Chaetomorpha. In the more turbid area adjacent to the mouth of Coonemia Creek, several algae, including Enteromorpha intestinalis, Chaetomorpha and Cladophora grew on the branches of drift trees or floated freely in the water. This lake was populated by a flock of swans, estimated at more than 1000 birds, that were presumed to be the agent that kept 86 the Lamprothamnion to such a uniform height. They were observed feeding in areas that supported only Lamprothamnion. Braithwaite ( 1975 ) listed Charaphytes as a basic food for swans. Such a large flock of birds would undoubtedly be of great significance in the active nutrient cycle needed to maintain such a large mass of vegetation. No Zostera was observed in Wollumboola Lake, but it grew abundantly in the adjacent Crookhaven Inlet. A narrow band of Juncus« that was well developed on the eastern side, formed a border to the lake. Triglochin procera grew abundantly in the sandy shallows along the northern shores. This was further evidence of the extended low salinity status of this lake as Triglochin procera has a reported salinity range of 0.2 to 2.5 %© T.D.S. ( Aston, 1973 )• A dry sclerophyllous scrub covered the southern foreshores that rose steeply to a low elevation. Heavy rains during March 1974 caused a rise of approximately 2 m in the level of Wollumboola Lake, more than doubling it volume. The sand bar was breached so that during the next week, the water fell to 50 to 60 cm below the November level. Thousands of small dead fish, mainly bream,were washed up on the banks. Most of the Lamprothamnion turned yellow and began to decay,and the odour of the lake became offensive, both from the dead fish and the decaying algae. The composition of the benthic flora of the lakes observed is summarised in Table A3.1. The limited environmental data is also included in this table. It is appreciated that the description of salinity and turbidity is based upon limited observations and a sampling of " local knowledge”. 87 3.2 Distribution of Animals in Illawarra Lake, Although prime emphasis in this study was placed upon the benthic flora, observations of animal life have also been made. Illawarra Lake supports a small commercial fishery, employing about 50 fishermen, many of whom are either itinerant or part-time only. During the five year period 1968 to 1973» the average annual fish and prawn catches were 174»200 Kg and 111,500 Kg respectively, worth an estimated $220,000 at the Sydney Pish Markets ( N.S.W. Fisheries Department - unpublished ) • Amateur fish catches were very much less than the commercial yield as the most abundant fish in the lake axe mullet, which are seldom taken on a line. The amateur prawn catch was estimated to exceed the commercial catch by about 20 io ( Fisheries Inspector for Illawarra Lake - pers, com. ). In order of importance, the main commercial fish species were sea mullet, luderick, flat tail mullet, garfish, dusky flathead, black bream, leather jackets, tailor, whiting and eels. Mullet species usually accounted for about 60 % of the annual catch ( N.S.W. Fisheries Department - unpublished ). The viability of this fishery is based upon the eastern Zostera beds where much of the netting by commercial fishermen and amateur prawners is focused. Analyses of the stomach contents of various species of fish, particularly mullet, luderick and garfish, have shown the importance of Zostera and its epiphytes, especially the diatom fraction, in their diet ( Thomson 1959 a,e; Wood 1959 a ). These, and other species of fish, also feed upon crustaceans, molluscs and anneleids, which Powis ( 1975 )» has shown occur at much higher population densities in Zostera beds than in uncolonised sediments. Ruello ( 1973 ) demonstrated the preference of the school prawn, Metapenaeua macleayi. for sediments within a particle size range of 250 to 500 pm and an organic content exceeding 2 % by 88 weight. Their food, was found to include minute bivalve molluscs, crustraceans ( and their larvae ) as well as polychaete worms. These environmental conditions, as assessed in Section 2.2.2, and to be discussed in Section 3*4*5> are provided by the extensive Zostera beds of Illawarra Lake. A great variety of non-commercial fish have also been observed, including pipe fish, fortesques, gobies, abundant porcupine fish and occasional stingrays. The coelenterate medusa, Catostylus mosaicus, occurred abundantly, often aggregating to form visible population densities of 1 to 5 per m over an area of 200 x ^00 m. Populations of this magnitude have often been observed in Griffins Bay, Tugger ah Bay and Yallah Bay. Smaller populations were observed throughout the lake. During periods of strong wind, hundreds of medusae are commonly stranded in Zostera beds. Ctenophores and Aurelea medusa, have occasionally been observed in the entrance channel. During the summer of 1975> when salinity was high ( 32 ) an octopus, about 30 cm long, was seen in Griffins Bay, feeding in water 10 cm deep. In the same period, blue swimmer crabs were collected from the Zostera beds along the Windang Peninsular shallows. Illawarra Lake supports a large and varied bird population, including gulls, terns, cormorants, pelicans, swans, ducks, coot, grebes, raptores, ibis, spoonbills,egrets, herons and reed warblers, plus a variety of resident and migratory waders. The list presented in Table A3.2, is not exhaustive but indicates the occurrence of selected species and their dependence for food upon the seagrass zone, the shallows and the detritus washed up on the shore. Although cormorants, gulls, terns and sea eagles fed over the entire lake, most other species were restricted to a zone extending from the shore vegetation to water 20 to 30 cm deep. Large flocks of black 89 swan, at times exceeding 500 "birds, were often observed feeding in a zone that extended from the shallows ( 10 cm ) out to about 1 m water depth, but most commonly in water from 20 to 60 cm deep. While they were often seen in some of the small bays around the lake, particularly Koona Bay, they usually congregated on the eastern Zostera/Ruppia beds. When a flock was disturbed while feeding, the area was often littered with Zostera leaves, confirming the report of Wood ( 1959 a ) that swans feed heavily upon this plant. They were also observed to feed intensively in areas that contained only Ruppia and around the edge of Enteromorpha masses. No swans were observed in the entrance channel. During June/July 1975j an investigation was conducted to determine the variation in biomass and species composition of the benthic macrofauna ( animals living in the sediments and which will not pass through a 1 mm screen ) from four sites, within the Zostera beds of Illawarra Lake. These sites were chosen on similar sediments ( ( Fig. 2.1 ) and the number of samples taken from the Zostera beds were; 1. the entrance channel east of Windang Bridge, 10 samples, 2. the back channel south of Bevans Island, 6 samples, 3. west of Bevans Island, 6 samples, 4. the eastern end of Griffins Bay, 10 samples. Sediment, vegetation and fauna samples were taken to a depth of 15 cm, using a 20 cm diameter cylindrical corer ( Fig. 3.7 ). Each sample was sieved through a 1 mm screen, placed in a plastic container and covered with lake water,to which had been added 10 ml of saturated magnesium chloride solution to narcoticise the fauna, so preventing the shock loss of appendages. In the laboratory, the animals were preserved in 3 $ formalin until they were sorted, 90 [ --- Handle Sediment removed to allow for insertion of plate to retain sample. Fig. 5.7. BENTHIC MACROFAUNA CORER 91 identified, counted and weighed. These data are presented in Table A3*3» Because of the variation in the number of samples at the four sites, all results have been extrapolated to the number and mass of organisms/m . These data are given in Table A3*4* Considerable variation in population composition, as revealed in each sample, was observed within and between sites. To assess the degree of variation, similarity indieies were calculated using the relationship: Similarity index = 2S a + b where S = number of shared species a = number of species found only in area a, b = number of species found only in area b. The similarity index within each of the four sampling sites was calculated after randomly dividing the discrete samples into two groups. These similarity indices are given in Table 3*1» TABLE 3.1 SIMILARITY INDICES - BENTHIC MACROFAUNA Entrance Back Bevans Griffins Channel Channel Island Bay Site 1 2 3 4 Entrance channel 1 Ojje 0.58 0.60 0.36 Back channel 2 Ml 0.74 0.63 Be vans Island 5 0.72 0.65 Griffins Bay 4 0.78 Within site values are underlined. These values show that the within site similarity in population composition was generally greater than the between site similarity. The difference between the entrance channel and Griffins Bay ( similarity index 0.36 ) was quite marked. Other significant differences occurred in biomass, population density, number of species, species diversity and the relative significance of the 92 phyla Mollusca, Annel^ida and Arthropoda, doth in diomass and number of organisms. These various differences are shown in Fig 3*3. The biomass of the benthic macrofauna ( net weight of the formalin preserved specimens blotted dry in a standard manner ) in the entrance channel was 8.5 times that in the back channel, 18.4 times that west of Bevans Island and 80 times that of Griffins Bay. At each site, 4 or 5 species made up 85 to 95 % of the biomass ( Table 5#2 )• In the entrance channel, the pelecypod mollusc, Macoma deltoldalis made up 47 ft and in Griffins Bay, the polychaete annel£id, Nereis diversicolor made up 45 ft of the benthic macrofauna biomass. The total number of animals, and the number of individuals of a species,varied from site to site. Highest population densities were observed in the back channel and west of Bevans Island, exceeding the entrance channel by a factor of 2 and Griffins Bay by a factor of 8. In the entrance channel, back channel and Griffins Bay, 5 or 6 species made up 85 to 95 ft of the population,with the gastropod molluscs, Nassarius and Diala, and the polychaete annel|id, Nereis diversicolor, being most abundant. West of Bevans Island Diala made up 81 ft of the population while in Griffins Bay, Nereis diversicolor made up 62 fto of the population ( Table 5*5 )• A similar dominance of the population by one or two species, was noted by Powis ( 1975 ) in the Tuggerah Lakes. A marked difference was also observed in the number of species. The entrance channel supported 60 ft more species than the back channel, 70 ft more than west of Bevans Island, and 110 fto more than Griffins Bay. Each of the three groups, molluscs, arthropods and anneleids were proportionally well represented at each of the 4 sites. The species diversity of the entrance channel, using the 93 100 100 80 80 oj a) rH rH P~i I* o «HO w oG w 40 •H ! t 30 o& p< 20 10 CVJ o 12 3 4 »—i Nemertineans t>D Annelids ci Arthropods GlL9 rH .& Molluscs Ph N"\ O 0 I—I X 3 O •H 1 rH rH >> >5 fi Ph fH u 2 a a W 0) § •H •H O a CO o o 52; o 5S5 12 3 4 12 3 4 2 3 4 Fig. 3.8. ANALYSIS OF BENTHIC MACR0FAUINA FROM FOUR SITES IN ILLAWARRA LAKE ( Fig. 2.1 ) JUNE 1975. 94 TABLE 5.2 BENTHIC MACROFAUNA BIOMASS Species that exceed 5 % of °/o biomass at Occurrence total biomass sites No. oi samples. 1 2 3 4 Mollusca Macoma deltoidalis 47 22 10 Xenostrobus securis 7 16 14 Eurytrochus strangei 5 10 Nassarius sp. 7 20 30 23 Pyrazus ebeninus 24 11 9 Velacumantus australis 7 5 Diala sp. 21 16 S 90 53 58 16 Arthropoda Macrobrachium intermedius 26 6 23 Family Eusiridae sp.l. 8 6 24 S 8 26 12 Annel£ida Nephtys australiensis 21 19 Nereis diversicolor 20 45 25 5 20 66 S all a/o 90 91 84 94 S all species 5 5 4 5 95 TABLE 3.5 BENTHIC MACROFAUNA - NUMBER OF ORGANISMS Species that exceed 5 % of * numbers at Occurrence total numbers sites No. of samples 1 2 5 4 Mollusca . Macoma deltoidalis 17 10 Lasaea australis 17 8 8 CM ros Nassarius sp. 25 8 5 Pyrazus ebeninus 15 9 Diala sp* 27 81 16 S 55 52 86 8 Arthropoda Macrobrachium intermedius 18 23 Family Eusiridae sp.l. 8 5 24 2 18 8 5 Annel&ida Nephtys australiensis 6 6 19 Nereis diversicolor 54 62 25 Haploscoloplos sp. 5 5 2 6 54 75 Nemertinea Nemertean sp. 7 20 S 7 S all % 86 94 86 86 S all species 6 5 2 3 96 species diversity index, "a", of Lewis and Taylor ( 1968: 372 ) was twice that of the other sites, all of which were similar in this respect. These differences in the benthic macrofanna indicate that the sites differed significantly in one or more environmental factors. All sites were within Zostera beds, on similar sediments ( (i) Salinity. In Section 2.3.2, details were given of observations of salinity variations on inflow and outflow tides, at the four benthic macrofauna sampling sites, following a July flood. It was noted that one week after the flood had subsided, the salinity in the entrance channel had fallen by 7*5 %o (on the outflow tide ) while the corresponding decrease in Griffins Bay was 15 °/°*> Organisms in Griffins Bay were subjected to more pronounced and prolonged salinity changes than in the entrance channel. For most of the time,organisms in Griffins Bay experienced little daily variation in salinity. Over a period of several weeks,they may have to adjust to gradual salinity changes in order of 10 °/oo . By comparison, organisms in the entrance channel experience a salinity fluctuation coincident with the tidal cycle. Salinity changes were usually between 3 to 9 Lpo in dry season but 7 to 15 %© in wet seasons. Many organisms in the entrance channel would not have to adjust to this variation as they are able to retreat into the sediment where salinity variation is minimal ( McLusky, 1971; Bayly, 1975 )* They could then emerge to feed and recharge the oxygen in their burrows when the salinity of the tidal 97 flow was tolerable. This behavioural response would be of little use in Griffins Bay. When a flood occurred, both sites experienced a sudden salinity drop. For organisms in Griffins Bay the change was long term ( at least several weeks ) but in the entrance channel, the tidal cycle usually returned within 3 to 5 days. (ii) Temperature. During the months April to August, lake temperature was usually 2° to 5°C less than sea temperature ( Kanamori, 1976 ). Consequently the entrance channel would be warmer than Griffins Bay. (iii) Biomass. The total plant biomass ( dry weight ), animal biomass and total animal population at each site is summarised in Table 3«4» TABLE 3.4 PLANT BIOMASS, ANIMAL BIOMASS AND TOTAL ANIMAL POPULATIONS AT THE FOUR SITES. ^ Site Entrance Back Bevans Griffins Parameter^ Channel Channel Island Bay Plant Biomass (g) 136 81 127 76 Animal Biomass (g) 1500 175 83 19 Animal Population 2800 6200 6230 825 From these data it may be seen that there is no correlation between plant biomass and either animal biomass or animal population. The entrance channel ranks 1st in plant biomass and animal biomass but 3rd in animal population. Bevans Island, which has a comparable 98 plant biomass had a much lower animal biomass but a much higher animal population. The back channel and Griffins Bay were similar in plant biomass but very different in the other two characteristics. (iv) Tidal Flux. The fourth factor, tidal fluxtwas considered from this and studies in other places ( Collett - pers. com. ) to be the most significant controlling variable. This twice daily tidal cycle in the entrance channel provided a nearly continuous flow of nutrients. Tidal influence in the back channel was much less than in the entrance channel; west of Bevans Island it was a little less than in the back channel, and was zero in Griffins Bay ( Fig.4#4 )• Nutrient flow, associated with tidal flux, higher temperature and less severe or prolonged osmotic stresses are considered to be adequate explanation of the much higher species number, species diversity, population density and biomass of lbenthic macrofauna in the entrance channel when compared with the other three sites. 99 3.3 DISTRIBUTION OF ALGAE IN ILLAWAHRA LAKE. 3.3.1 Gracilaria confervoides ( L. ) Grev. Gracilaria occurs abundantly in some areas of Illawarra Lake ( Fig. 3*9 )• In this survey, heaviest growxns were observed in Koona Bay, Haywards Bay, Koong Burry Bay and Griffins Bay. In Koona and Haywards Bay,it was the dominant species, occupying most of the silty sediments ( 30 to 95 c/° fines ) in the central areas of these bays. At the western end of Koona Bay, its distribution was limited by a massive, persistent, floating Enteromorpha mass. Patchy growth was also noted on silty sediments ( 80 to 95 % fines ) in water 1 to 1.5 m deep, in Karoo Bay. In Griffins Bay, the entrance to Haywards Bay and in Koong Burry Bay, it grew in an association with Zostera capricomi. Lesser amounts occurred in most other areas, including the eastern Zostera beds. The depth to which Gracilaria grew varied markedly. On the western side of the lake, where Gracilaria and Zostera grew together,, Zostera was usually dominant in the shallow water (<^ 50 cm ), but beyond this depth Zostera became sparser and Gracilaria more abundant.. At these sites, Gracilaria was observed to extend to a depth of about 2 m. In Koong Burry Bay, on silty sediments ( 20 - 50 % fines ) Gracilaria was dominant over Zostera even in water less than 1 m deep during 1972, and by 1975 had almost completely replaced the Zostera throughout the bay. During 1974/75* Gracilaria invaded the entrance to the outlet channel from Tallawarra Power Station and since that time it has sparsely colonised former bare, muddy-sand ( 15 % fines ) over an area of several hundred m . On the eastern side of the lake, in the extensive Zostera beds, Gracilaria grew sparsely and was seldom seen in water deeper than 1m, even though the eastern side of the lake was less turbid than the western side. In this area Gracilaria was not observed to grow 100 \b CD Illawarra Lake !A A A Zostera Ruppia Lamprothamnion Gracilaria Fi/?. ^.BENTHIC FLORA. IN ILLAWARRA LAKE, 101 beyond the Zostera zone. Young Gracilaria plants were first seen as a tuft growing from the sediment, often attached to a shell or stone. As the plant grew, the branching became more extensive, and either irregular and idefinite, or sometimes sub-dichotomous. The thailus often reached a length of 40 to 60 cm. In sheltered bays, Gracilaria often formed dense,tangled, continuous clumps that 2 covered up to 100 m . Usually the plant was attached to the sediment, but during periods of high winds, wave action fragmented the colonies setting free large quantities of floating algae. These fragments were driven by the wind until they lodged in a Zostera bed or on the bank. Large masses of this drift material often accumulated in the shallows of Griffins Bay, Koona Bay and Haywards Bay, or less frequently in Tuggerah Bay. The persistence of this drift material suggested either that there was a continuous supply, or more probably, the Gracilaria continued to grow even when not attached to the sediment. Fragments that were transplanted by hand into the sediments in the outlet channel at Tallawarra Power Station grew readily, demonstrating that this algae could vegetatively colonise new areas. Although sexual structures were observed throughout the year, cystocarp development was most common during the summer months. No Gracilaria was seen in the entrance channel or in any of the inflow streams. Its observed salinity range therefore was 10 to 32 °/oo . The lower salinity was experienced for only a few weeks at a time during the observation period. It grew mainly in areas of black, foetid muddy-sand or silts and was most abundant in the more turbid areas of the lake 102 Gracilaria was also observed in Conjola Lake and Burrill Lake but only as discrete plants. It was only a minor component of the benthic flora of those lakes. Published reports on Gracilaria include Causey et al. ( 1946 ) and May ( 1940 )• The observations of the growth of Gracilaria in Illawarra Lake are consistent with the comments of May ( 1940 ) who recognised two forms of Gracilaria confervoides ( L. ) Grev. in Illawarra Lake. These were G. confervoides f. ccortica May and G. confervoides f. gracilis ( Turn. ) Grunow. The form observed in this study was consistent with May's description of G. confervoides f. ecortica. Causey et al. ( 1946 ) reported the influence of environmental factors upon the growth of G. confervoides. They concluded that the plant was euryhaline, with an optimum salinity requirement in the range 25 to 35 p.p.m. ( sic ) but that the plant made growth throughout a salinity range of 15 to 50 p.p.m. ( sic ). It is assumed that the units should have read 25 to 35 c/°o and 15 to 50 ioo respectively. Maximum growth rates occurred within the temperature range 25° to 28°C and ceased at 10°C. Light intensity was also significant with rapid growth, in which a weight increase of 100 °/o was observed in ten days, occurring at a depth of 2 to 4 feet. On this empirical data and observations in the field, it is concluded that the environmental conditions of Illawarra Lake would be limiting to the growth of Gracilaria for only 1 to 2 months during the winter and during seasons of heavy flooding. In Illawarra Lake, Gracilaria appeared to tolerate high turbidity better than Zostera. The much more vigorous growth of Gracilaria on the finer, and therefore higher nutrient status sediments of 103 the western side of the lake, in spite of the higher turbidity, than on the lower nutrient status sands of the eastern Zostera beds, is consistent with the findings of Goxterma , et al, ( 19&9 ) who showed that algae growing on sediments can utilise sediment phosphorus. It seemed also to thrive best in lentic situations. 3.3.2 Lamprothamnion. Lamprothamnion occurred sporadically, or at times extensively, throughout the low turbidity and sheltered Ruppia zone of the Windang Peninsular seagrass beds ( Pig. 3*9 )• Maximum development usually occurred during spring and early summer with a late autumn decline that at times coincided with the influx of swans. Braithwaite ( 1975 ) stated that charaphytes were an important food source for swans, which may in part account for the large populations of these birds on both Illawarra Lake and Wollumboola Lake. This branching, erect alga grew attached to sediments, that varied from clean sand to muddy-sand in Illawarra Lake and from clean sand to silts, in Wollumboola Lake. In this study, the observed salinity range in Illawarra Lake was 10 to 32 °/*o but Lamprothamnion grew abundantly in Wollumboola Lake at less than 10 °/oo salinity* Lawson ( 1961 ) stated that charaphytes were generally restricted to water in which the salinity does not exceed 20 a/ue , but Womersley ( pers. com. ) has observed Lamprothamnion growing abundantly in the Coorong of South Australia. The salinity of that lake may exceed twice normal sea water. It is concluded that Lamprothamnion is a euryhaline species and that possibly, because of its brittle nature, it can survive best in lentic situations ( the Ruppia zone of Illawarra Lake ) or in deeper water of low turbidity ( as in Wollumboola 104 Lake ). Given that the plant has a wide salinity tolerance, it is suggested that the die-off that occurred in Wollumboola Lake following the April flood of 1974 was most probably a result of greatly increased turbidity, 3.5*3 Epiphytic Algae of Angiosperms. Samples of Zostera epiphytes were collected at about monthly intervals during the period from August 1972 to January 1973* Epiphyte density and species composition varied seasonally and between sites. Five Zostera leaves, bearing epiphytes, were collected from each site and examined microscopically. A record of observations, on only the most common species,showing distribution and relative abundance, is given in Table 3*5* No attempt has been made to distinguish between species of diatoms, nor to identify filamentous alga beyond generic level. The Zostera at site 4» in Koonawarra Bay ( See Fig. 2.1 ) was unusual in that no epiphytes were observed at this site, except for a sparse growth of diatoms during January, 1973. Polysiphonia was the only epiphyte seen to occur at all stations ( except site 4 ) throughout the observation period, and it was also the most abundant epiphyte. On the older Zostera leaves, it formed a dense growth, to 3 cm in length along the upper 5 to 20 cm of the leaf,resembling a small feather duster. Fertile material, cystocarpic, spermatangial and tetrasporangial wa3 observed throughout the year, as were sporelings on the younger Zostera leaves. The density and length of Polysiphonia growth appeared to be a function of the age of the Zostera leaf it was attached to, rather than a reflection of seasonal changes or variations in other environmental factors such as temperature or daylength. The visual impression of the epiphyte was most marked during late summer and early autumn when the 105 S eg sp a rse O P = s p o medium, = m n o d en se, = p o d : D e n sity s p e c ie s , S rH o th e r = 0 pi pi common, o o = C p p dom inant, = D Abundance 106 number of older Zostera leaves in a weed bed was ad a maximum. Similar long, dense growths were observed on individual leaves throughout the whole of the year. Other epiphytic algae ( Knteromorpha, Cladophora, Ceramium,Oscillatoria, Lyngbya, Calothrix and diatoms ) were also observed throughout the year, but they were not usually as abundant or as widespread. Ceramium was more common during the summer but was seldom observed on the western side of the lake. Knteromorpha was more abundant during the winter than the summer. Some algae ( Kctocarpus, Anabaena, and Spirulina ) were observed only during the summer while Rhizoclonium was seen only in the spring. While most of the species mentioned had a wide range, Fercusaria and Rhizoclonium were collected only from the Windang Peninsular Zostera beds. During the 1972 survey, Kctocarpus occurred as a dominant only off chore from Primbee at site 6, but since that time it has been abundant during late summer, along the Windang Peninsular and Be vans Island Zostera beds. Five species of blue-green algae were observed in the epiphyte association, but only Calothrix was actually epiphytic. This population of cyanophytes increased during the summer and was most common on the older Zostera leaves, particularly those with a heavy coating of silt. Ceramium was also more common on the older leaves suggesting a successional development. Less frequent observations since the 1972 survey have confirmed Polysiphonia as the dominant algal epiphyte of Zostera in Illawarra Lake and the increased abundance of cyanophytes during the summer months. Subsequent observations 107 have shown also that 1972/73 was a season of exceptionally heavy epiphyte development. During 1975/76, epiphytes longer than 1 cm were observed only inshore of site 4* The major epiphyte on that occasion was Cladophora. Most of the eastern Zostera beds bore abundant diatoms but fewer filamentous algae. Similar heavy epiphytic algal growths on Zostera were reported by Wood ( 1959 a ) and contrary to his observations , abundant epiphytes were noted on Ruppia during both the 1972/73 and the 1975/76 surveys. There were fewer species, with Cladophora, up to 5 cm, dominating throughout the year. Diatom populations fluctuated but at times were abundant. The importance of such algal epiphytes of aquatic angiosperms as a food source for fish has been discussed by Wood ( 1959 a ) and Thomson ( 1959 a,e ). 3.3*4 Filamentous Algae. During 1972, monthly observations were made of the abundant filamentous algal masses of Illawarra Lake. These growths were of four types. (i) An Enteromorpha intestinalis dominated growth, that was attached to the sediments in shallow water, was widespread during the winter and spring. It extended continuously over areas measuring up to 50 m x 150 m, in Koona Bay, Koong Burry Bay and in Griffins Bay. A fringing growth developed along the Tuggerah Bay shore and filled the back channel shallows at the Windang Bridge ( Fig. 3*10 ). During December, the growths disintegrated rapidly in all but a few minor clumps in Koonawarra Bay, Koona Bay, Griffins Bay and the back channel. In water less than 25 cm deep, Enteromorpha 108 Illawarra Lake Entoromorpha growth Mixed filamentous algal growth Fig. 5.10. DISTRIBUTION OF FILAMENTOUS ALGAL GROWTHS IN ILLAWARRA LAKE, 109 formed, a continuous growth from the black, sulphurous sediment to the water surface. Upper portions of the growth were usually bright green, while the shaded, lower portions were usually yellow and in varying degrees of decomposition. This mass was supported in part by gases trapped within the hollow thallus. Within these growths there often occurred large quantities of the coarse, uniseriate, filamentous alga, Chaetomorpha. (ii) Floating Enteromorpha intestinalis growths that occurred in association with Zostera/Ruppia beds and covered areas up to 30 m x 10 m. The occurrence of these growths was usually, though not exclusively associated with the distribution of Ruppia, which became entangled with the floating mass, allowing for a more effective anchorage than provided by Zostera. This growth, which seldom extended deeper than 20 cun, often contained abundant Cladophora. Buoyancy resulted from the trapping of gases in the hollow Enteromorpha thallus. Towards early summer, when these masses began to degenerate, various other algae were observed as part of the association. These included Polysiphonia ( epihpytic on Enteromorpha ), Oscillatoria, Chaetomorpha and Lyngbya. An abundant crustacean and mollusc fauna was observed within these Enteromorpha growths. (iii) A Cladophora dominated growth formed an extensive, dense, submerged mass through which only the tips of Zostera leaves were visible, with the lake bottom completely obscured. This growth extended continuously over the Windang Peninsular Zostera/Ruppia bed and formed dense patches over the Bevans Island bed. Only sparse 110 development occurred in the western Zostera beds, but not at all in Koonawarra Bay. When the growths were first sampled, during September, they were composed almost entirely of Claaophora. During October and November, other algae began to appear. Enteromorpha became common with occasional occurrences of Ceramium and Polysiphonia. As the growth began to degenerate during late November and December, blue-green algae, notably Oscillatoria, Lyngbya and Spirulina became more common. By late December, the mass had degenerated and dispersed. An abundant crustacean fauna was observed living in this community throughout its existence, but decreased during December as the growth degenerated. This heavy algal growth was a great hindrance to the commercial and amateur prawners as it clogged their nets. Pishing nets were similarly fouled and difficult to clean. (iv) An Ulothrix - ulvales floating growth that in some areas replaced the floating Enteromorpha growths during December and persisted until March. The dominant alga however, was Ulothrix .that formed a dense surface network trapping large gas bubbles. Associated with the Ulothrix was a multiseriate, highly branched member of the Ulvales, possibly an Enteromorpha species. Observations during subsequent years have confirmed that the floating and submerged algal masses show a seasonal growth pattern. Disintegration of the growths during the summer was usually preceded by a marked bleaching; hence high light intensity may be a significant factor. Residual populations of Enteromorpha do however persist through the summer. All growths showed an increasing species diversity with Ill age and the onset of decay. The blue-green algae in particular, became more common during this disintegration phase. During periods of high water and strong winds, masses of the floating algae washed ashore where they decayed and became a foul-smelling nuisance. This decaying mass supported a vast population of crustaceans, anneleids and molluscs, so becoming a focal feeding area for numerous birds ( Table A3.2 ). ' The vast quantity of algal growth in this lake confirms the high nutrient status as indicated by water analyses. The phosphate recycling capacity of Bnteromorpha intestinalis ( Baas Becking and Mackay, 1956 ) could be important in maintaining the phosphate level of lake water, by transfer from the phosphate rich sediments. 112 5.4 DISTRIBUTION OF ANGIOSPERHS 5*4*1 Taxonomy. Five species of aquatic angiosperms are common in the saline lagoons observed in this study. These were: Posidonia australis Hook.f. Ruppia maritima L. ex Dumort. Halophila ovalis ( R. Br. ) Hook.f. Zostera capricomi Aschers. Zostera muelleri Irmisch. ex. Aschers. Comprehensive descriptions of these plants have been given by Bentham ( 1877 )» Ostenfeld ( 1916 ), Wood ( 1959 a ), den Hartog ( 1970 ) and Aston ( 1975 )• (i) Posidonia. Wood ( 1959 a ) suggested the presence on the N.S.W. coast of two species of Posidonia; a broad leaf form and a narrow leaf form, with quite distinct floral structures. This has been rejected by den Hartog ( 1970 ) who asserted that the illustrations presented by Wood ( 1959 a, f.la^-b, p.220 ) were incorrectly drawn and questioned the observations presented in f. lc-d. From observations of drift material in which he found rhizomes bearing both broad and narrow leaves, den Hartog ( 1970 ) concluded that there was only one species and that the narrow leaved shoots probably indicated senility of the rhizome system. (ii) Ruppia. Thompson ( 1961 ) has recognised two species of Ruppia, R. maritima and R. spiralis, in N.S.W. This has been followed by Beadle, Evans and Carolin ( 1972 ). R. spiralis was considered to be widespread and common, R. maritima rare. Aston ( 1975 ) detailed the confusion over specific delimitation in the genus and considered that until the taxonomy is clarified,all Ruppia in Australia should 113 be referred to R. maritima. Wood ( 1959 a ) referred to R. maritima on the N.S.W. coast; this is the same species referred to R. spiralis by later workers. (iii) Halophila. Wood ( 1959 a ), Higginson ( 1965 )» den Hartog ( 1970 ) and Aston ( 1973 ) agreed on the description and specific designation of Halophila ovalis ( R.Br. ) Hook.f. Den Hartog ( 1970 ) commented upon the wide variation in leaf morphology and attributed this to environmental differences. He suggested also the possibility of distinguishing subspecies H. ovalis ssp. ovalis and H. ovalis ssp. australis. (iv) Zostera. The taxonomy of this genus and discussion of the morphological variations of Z, capricorni and Z. muelleri are included in Section 4*1* The occurrence of these several species has been given in Table A3.1 and Fig. 3.1 to 3.6 and 3.9. 3•4•2 Ecological Observations on Posidonia australis. The reported range of Posidonia australis on the east coast of Australia extends from Port Stephens, south ( Wood, 1959 a ). It occurs in sheltered bays that are largely marine in character ( Botany Bay and Port Hacking ) and also within some coastal lakes and estuaries. Wood ( 1959 a ) noted its presence in Macquarie Lake, St. Georges Basin and Merimbula Lake. For reasons that remain obscure, Posidonia does not occur in Illawarra Lake. Aspects of the ecology of Posidonia australis have been reported on by Wood ( 1959 a,b, ), den Hartog ( 1970 ), Aston ( 1973 ) and Larkum ( 1975 )• From these accounts and from observations made in this study, it is noted that Posidonia will grow from the low-water mark to a depth of 10 m in clear water, 114 of variable salinity, but it is not tolerant of high turbidity. It survives on a range of sediments that vary from oxidised sand, as in Macquarie Lake, to reduced muddy sands as in Botany Bay near Towra Point. Posidonia is not tolerant of strong currents or of high turbulence. Studies by Larkum ( 1975 ) in Botany Bay suggest that the Towra Point beds have been damaged by recent heavy wave action coincident with port works and the dredging of navigation channels. The rhizomes are capable of vertical growth and hence Posidonia can recover from burial by sand. In St. Vincent Gulf, S.A., buried Posidonia rhizomes, that were at one time harvested commercially, form a deposit about 3 m thick ( Womersley, pers. com. ). Flowering occurs from June to October, but no fertile specimens were observed during this study. Posidonia was observed in this study to support a variety of epiphytic algae including Polysiphonia, Ceramium, Laurencia, Rnteromorpha, Colpomenia and Oscillatoria. as well as a host of diatoms and epiphytic animals. It is possible that high turbidity may exclude Posidonia from the body of Illawarra Lake but it would not prevent growth in the entrance channel. Suitable sediments are available and although the salinity fluctuates widely, the entrance channel area usually experiences a salinity approaching ocean levels. Turbulence may be an excluding factor but as the tidal flux is small, current velocities do not approach the rip conditions observed in the entrance to Macquarie Lake. As Illawarra Lake is well within the geographical range of P. australis, and as colonisation is known to occur from seeds ( den Hartog, 1970 ) it is reasonable to assume that Posidonia seeds could enter the lake The nearest known growth of Posidonia occurs 3*5 Km to the south at Shellharbour. The failure of Posidonia to grow in Illawarra Lake 115 remains an enigma. 5*4*5 Ecological Observations on Halophila ovalis. Halophila was observed to grow on a wide range of sediments, varying from clean sand at Shellharbour, to rauddy-sand in Tuggerah Lake , to gravels and sulphurous mud in Gondola and Burrill Lake. The water at these sites varied in salinity from brackish in upper Conjola Lake and the Tuggerah Lakes to normal seawater at Shellharbour. Variations in turbidity were from clear ocean water ( Secchi disc extinction greater than 5 m ) to high turbidity situations ( Secchi disc extinction less than 0.5 m ) in Burrill Lake. It was observed growing over a depth range from 20 cm in upper Conjola Lake to 2 m in Burrill Lake. While this plant obviously has wide ecological tolerances of turbidity, salinity and substrate, it was not observed to form more than minor colonies; neither was it observed growing in Illawarra Lake, an absence that remains -unexplained. It readily colonises new sediment, regenerating rapidly from fragments of the brittle rhizome and can withstand repeated burial with sand, as has occurred at Shellharbour. Den Hartog ( 1970 ) stated that under calm conditions, Halophila can accumulate sediment and hence build the sea or lake floor. The depth to which Halophila is found, in relation to other aquatic angiosperms varies considerably. In Tuggerah Lake, it usually occurred in water less than 1 m deep, and at times as a fringe above the Zostera. In Conjola Lake and Burrill Lake it occurred at levels shallower and deeper than Zostera while in the study of Spencer Gulf, by Shepherd and Branden ( 1974 ). Halophila was observed at 10 m, at the bottom of the series Posidonia - Amphibolus association, Posidonia, Heterozostera, Halophila. Halophila is recorded as flowering in January and February 116 ( den Hartog, 1970 ) out no fertile material was observed during this study. 3.4*4 Ecological Observations on Ruppia maritima. In Illawarra Lake, Ruppia occupied a third of the vegetated area of the Windang Peninsular shallows. It formed a dense growth in water 40 to 60 cm deep, but in the shallower areas grew more sparsely, often as discrete plants less than 20 cm across. The change from Ruppia to Zostera, in the deeper water, was abrupt. Occasionally single plants or a few plants of Ruppia. usually occupying less than 1 m , occurred in the shallows (< 40 cm ) west 2 of Be vans Island. Clusters up to 10 m were noted in water less than 40 cm deep in Griffins Bay, with occasional plants in water 60 cm deep. Sparse growth also occurred in the Koonawarra Bay shallows. Hooka Creek supported widely fluctuating colonies, with dense growth persisting in its upper reaches. During this study, Ruppia has been observed to grow on a wide range of sediments. Analyses of sediments from Illawarra Lake observed to support Ruppia. are given in Table 3*6. These data show that in Illawarra Lake, Ruppia grew upon sediments in which the sand fraction ranged from 68 % to 97 with a mean of 91 °/o and a mean organic carbon content of 2.4 The most dense growths, as shown by a survey of benthic flora biomass ( Fig. 3*H> Section 3*4*5 ) occurred off shore from Primbee and in Griffins Bay ( Fig. 2.1 ) at sites 21, D, G and I,with a sand range of 91 $ to 97 %,a mean of 95 % and a mean organic carbon content of 1.75 In Hooka Creek, Ruppia grew upon sediments composed of about 14 $ sand, 77 % silt, 9 % clay and an organic carbon content of 12 % ( Jones, 1976 ). Ruppia was also observed to grow on clean sand in Wollumboola Lake, on muddy-sand and silts in Tuggerah Lake and upon a clay bank in the Willinga Lake entrance channel. TABLE 5*6 COMPOSITION OF SEDIMENTS SUPPORTING RUPPIA - ILLAWARRA LAKE M O O to & H- P c+ H- 3 CO o CO c+ o O CD 3 H* 0*3 ’ o S CO s o CD p^ H- - c+ CD CO H- S CD 1-3 S- CO M H H- c+ p o ►3 o c+ P M o 3 H- O <<; Or? . ’ ’ pi p. CO p- g CD »*1 S CO cf p R o 2 ; V tf. J n — on o O 1 ON ro ro vn -o • on NJI ' CD IN) — 00 M ro » vo -fi ' 1 — — (V) ON ON 1 J •• vo ON Ul ' 1 — od M H-* CD IN) CT\ I 4N- Vjl — i NO V>i 4N O (\D •• -o VO -o H on -4 H - n ro H M NH -P>. -J -£>• Ui o 117 W M ro •• — on ON VH n on ro on o rv> • -£>. O 1 — M Q t ON • VM vn -fN- -J VM J 1 J — — O M t o ffl IV) V_n -fN- on — ON fO m (O ON H ON ro 00 •• 1 d I- < w H> < P c X| ro VOVOVOVOVOVOVOVO • -r- X| most dense sites ) 95 5 1.75 118 The observed salinity range under which Ruppia grew in Illawarra Lake was from approximately 5 iQo in Hooka Creek to approximately 52 west of Bevans Island. During the period June 1975 to February 1976, the most dense growth along the Windang Peninsular experienced a salinity range 50 to 92 ^>0 50 °/o of the time, 25 to 50 %, 20 % of the time, 20 to 25 1<*> 25 % of the time and less than 20 5 $ of the time ( Fig. 2.21 ). The highest Ruppia biomass was observed at sites at the northern end of the peninsular, which were remote from the entrance. Flowering was observed during the period September to March,with an abundance during December to February. Fruits were also abundant. As mentioned in Section 5*5*3* extensive floating algal masses were localised in the Ruppia zone of the Windang Peninsular. Submerged growths were abundant during the winter and the algal epiphyte population, though poorer in species than that observed on Zostera, was at times dense and long ( Plate 1 ). The feeding of large flocks of swans was usually concentrated in the Ruppia zone of the Windang Peninsular seagrass beds. At all sites in Illawarra Lake, where Ruppia was present, it grew in association with,or inshore of Zostera. This was the reverse of the situation in the Tuggerah Lakes, as described by Higginson ( 1965 )• Higginson ( 1965 ) suggested that the distribution of Ruppia and Zostera in that lake system could be best explained in terms of sediment differences. "The results show that Zostera tends to favour the sandy sediments and Ruppia the clayey sediments, the intermediate sediments having a mixed community" p. 331-332* He demonstrated in the laboratory; the higher nutrient status of the clay sediments, that the growth rate of Ruppia on 119 PLATE 1, Ruppia maritima bearing long, dense , filamentous algal epiphytes - Illawarra Lake - November 1976# Natural size. 120 121 clay was twice that on sand,and the Ruppia biomass on clay sediments was 6 times that on sandy sediments. However, because attempts to cultivate Zostera under laboratory conditions have been unsuccessful, it has not been possible to conduct similar investigation of this species, or to study the relative growth rate of these two species, in competition, under controlled conditions. In Illawarra Lake, there was no relationship between the distribution of Ruppia and sediment type. As mentioned earlier, Ruppia was the dominant angiosperm on sediment consisting of 97 % sand. In Wollumboola Lake, Ruppia occurred mainly on the clean sand sediments along the eastern and northern shallows. Wood ( 1959 a ) reported that Ruppia required " good " illumination, a conclusion that was supported by Higginson ( 1965 who noted that while Zostera grew to a depth of 4 m, Ruppia was rarely observed in water deeper than 2.7 m. This could partially explain the reason for Ruppia being seldom found on the less sandy sediments along the southern and western side of Illawarra Lake. At these sites, neither salinity nor nutrients would have been limiting, but turbidity was usually significantly higher than along the eastern shallows. Both Wood ( 1959 a ) and Higginson ( 1965 ) agreed that Ruppia was intolerant of strong currents, as it occurred mainly in lentic locations such as sheltered bays. This could explain why, in Illawarra Lake, Ruppia occurs inshore of Zostera beds. As mentioned in Section 1, Illawarra Lake is exposed to strong winds and is often dangerously turbulent for small boats. This turbulence diminishes rapidly over the Zostera beds. On the western and southern margins of the lake, the Zostera zone was narrow and the water was deeper. Consequently strong wave action 122 is common along the whole of these shores. These several observations do not explain the marked differences in the abundance of Ruppia on the Windang Peninsular and Bevans Island seagrass beds. The sediments in both areas were sandy, both areas were protected by extensive Zostera beds and the turbidity at both sites was similar. During the observation period, June 1975 to February 197&, the salinity at Bevans Island, 500 m off shore, in water 1 m deep, was usually 1 to 2 higher than at the northern end of the Windang Peninsular beds. More significantly, the inshore areas off Bevans Island, i.e. water less than 40 cm deep, often experienced direct tidal water from both the main channel and the back channel. Consequently these shallows at times approached sea salinity and experienced daily salinity variations of several parts per thousand. Ruppia has been reported to exist over a very wide salinity range from 0.2 to 60 c/oc ( Yezdani in Aston, 1973 )• In spite of this, and as it has been observed in this study that the biomass of Ruppia increased with distance from the entrance channel, one must support Higginson’s ( 1965 ) conclusion that the plant does not grow well in strongly saline water. Early in the investigation of this problem, it was thought that perhaps the Windang barrier sands behaved as an aquifer, supplying fresh water to inshore areas of the lake, ana that the extensive growth of Ruppia and Zostera would inhibit the mixing of this lower salinity water with the main lake water. Repeated traverses across the weed beds in this zone failed to reveal salinity differences greater than 1 a/oo • Similar variations were observed in Griffins Bay and off Bevans Island. Therefore this difference, and the possibility of freshwater inflow from the water table, were not considered to be significant. 123 MacIntyre ( pers. com. ) from his long term observations of Tuggerah Lakes, suggested that the variations in the abundance of Ruppia from year to year could be related to rainfall, with periods of expansion during high rainfall - low salinity years and contraction during low rainfall - higher salinity years. The rainfall for Illawarra Lake for the last four years was ; 1972, 1058 mm; 1973* 963 mm; 1974* 1990 mm; and 1975* 1740 mm; as compared with the 70 year average of 1118 mm. Luring this time there has been no obvious change in the distribution or abundance of Ruppia in Illawarra Lake, apart from some decline in the rapidly accreting shallows in Koonawarra Bay. 3.4*5 Benthic Flora Biomass. To assess variation in the abundance of the species comprising the eastern seagrass beds, a biomass survey was conducted during November, 1975* Ten sites were selected ( A to J, Pig. 2.1 ). Five samples were taken at each site with a 25 cm diameter cylindrical corer. In the field, each sample was washed thoroughly in a 2 mm sieve to remove the sediment, rinsed in 10 % formalin and placed in a plastic bag. In the laboratory the material was once again washed thoroughly in a 2 mm sieve, to remove all trace of sediment and salts. The plant material was then sorted into categories : Zostera shoots, Zostera rhizomes, Ruppia, Gracilaria, filamentous algae, and sundry organic matter. Each sample was then oven-dried thoroughly at 98°C ( the limit of the drying oven available ) and weighed. The results cf this survey, Table A3.5* show variations between samples and between sites. Samples from sites that were judged visually to have little variation in growth ( B and C ) produced similar results, indicating the degree of reliability of the sampling procedure. A summary of these results is presented in Table 3*6 and in Pig. 3*11* TABLE 5 .6 BENTHIC FLORA BIOMASS - DRY WEIGHT ( g /0 .2 5 ) NOVEMBER 1 9 7 5. * — i lor o o H- o m IV) H* ch p o p »-« CO s P o P H* CO • • • /-N 1 4 n — a b M o o o H- t H- H- CD P cf P 03 >-3 cf p O ib CD 3 o P Q g H- s P 6 p C CO cH CD c+ tb t~* p 3 o C/3 CD P P 3 ts: CD CO H* no - 1 h n o B P W a tr + h- > P CD bd H- o B CO Cfl po P P CD o CO 3 CD CD P' O C+* § P Cm ° b H- CD b p 5 O i ct* C+- cm B o o B cm 'oL cm cm cm "cL cm cm 1 1 1 1 4 1 —J — — — o o o o ON O t o H CD rv> I- I o f 1 IV) • • rv> • • • • • • • > % -4 VM VM vn -4 4^ vn vn VM VM — 4^ VM 4^ VM VM vn vn 1 1 1 1 | o h- CO h- O O o H O M O ro ON M O ON O bd • M « • • • • • vn -4 VO vo vo vn -4 vn -4 VM VM VM 4^ vn VM vn 1 J | 1 1 | 1 124 o o o o O M 00 O rv> o ON rvo h- (V) c ON • •• • • • O ••• VO — -4 vo -4 vn 4^ VM VO VM VM 4^ VM J 1 I 1 O CD IV) CD ro M ON 00 O M ON • o • • • • ON • • O •• • fcJ -V vn -4 VM — -V VM vn vo vo vn 4^ vo VM VM vo vn 1 1 J — 1 o o o H-* O o M t h- M o CD CD ON H-* CD IV) ro ON rv IV) • • • • • • • td O • IV) • • * — VM vo vo VM VM vo vn vn vn VM vn VM 1 1 J 1 1 1 1 1 o CD o o H~ h- O ON CD rv ON O o rv> • • O • • • • • -4 VO — vo VM vo VM VM vn 4^ * ’ J J 1 1 1 1 1 1 — 1 — M t— t— CD l rv ON IV) CD f CD rv rv> ON IV) O • Q • • • -IV -4 4^ VM vn vn 1 1 1 1 o I- o o O o M CD M OO CD CD ON M o O ON (V) ON O M IV) • • • • •• • • • w • -0 vn -4 vo -P^ VM -£=• VM vo VM VM I O CD M 2 5 .4 6 2 5 .9 2 9 .8 7 2 8 .1 2 8 .4 4 2 6 .8 2 2 .5 4 2 1 .2 - - 1 0 6 .5 1 vn rv) vn 1 0 O CT\ -4 vn Biomass ( dry weight, g/ 0.25 100 80 70 Fig. 5.11 . BENTHIC 125 FLORA NOVEMBER BIOMASS 1975. - EASTERN Rhizomes Ruppia Zostera matter Gracilaria Other SEAGRASS algae shoots and BEDS organic 126 Analysis of sediments and water samples from these sites have been presented and discussed in Section 2. This survey revealed a variation in plant biomass ( dry weight ) from 45 g/0.25 m in the shallows off Bevans Island to 161 g/0.25 m in the dense Ruppia bed at site G. These values should not be extrapolated to estimate total plant biomass at the sites sampled, as the sample areas were small ( and therefore susceptible to large errors of estimation ) and no attempt was made to sample widely enough to indicate total variability or the extent of uncolonised areas. These results do however 3how the variation in species abundance at each site. Inshore sites ( A, D, and I ) in shallow water 50 to 60 cm deep, showed a greater species number than the deeper water, off shore sites ( B, C, F, H, and J ) which were dominated by Zostera. The widespread though sparse occurrence of Gracilaria in the eastern weed beds, with its abundance in Griffins Bay is demonstrated. The much greater abundance of Ruppia in Griffins Bay and along the Windang Peninsular, than at Bevans Island, together with the heavy filamentous algal growth of the northern beds, are also apparent. From the data given,it seemed possible that water depth and salinity may be important in influencing biomass and species composition. Both Ruppia and Gracilaria were more abundant at sites remote from the entrance channel. Ruppia was rarely observed in water deeper than 60 cm. Highest yields of plant shoots were obtained from sites with an intermediate water depth,60 to 90 cm ( B, C, E, F, G, and I ) while shallow sites ( 50 cm at A ) and deeper sites (<^ 80 cm II and J in more turbid waters ) gave low yields 127 Some selected relationships, as observed at Bevans Island ( sites A, B and C ) Fig. 3«12 revealed that as water depth increased, so did the mean Zostera shoot length. Zostera shoot biomass and total plant biomass was greatest at site B, even though the nutrient status ( total phosphorus, and organic carbon ) continued to increase in the series A Similarly, at the Griffins Bay sites ( I and J ) -» mean Zostera shoot length increased with water depth ( Fig. 3*13 ) but both Zostera shoot mass and total plant biomass decreased as did nutrients ( total phosphorus and organic carbon ). Opposite the 2WL radio transmitter ( at sites D, E and F ), mean Zostera shoot length reflected neither water depth nor nutrient status ( Fig. 3#14)*The greatest biomass was observed at F, even though this site had the lowest nutrient status. The much greater mass of organic matter, mainly decomposing leaves and rhizomes, recovered from areas supporting Zostera than from Ruppia areas, would be of ecological significance. This detritus forms part of the diet of many of the benthic macrofauna ( MacIntyre, 1959 ) and is probably an important food source for prawns ( Ruello, 1973 )• The tentative conclusions drawn from these observations were that Zostera shoot length usually increased with water depth, as did biomass, up to a critical water depth, beyond which biomass decreased. The total plant biomass did not seem to be related directly to the nutrient status of the sediment. More intensive investigations of these conclusions, in relation to Zostera growth, are presented and discussed in Section 4* 3.4• 6. Zostera capricomi and Zostera muelleri. Section 4 of this thesis is devoted to investigations ana discussion of the biology of Zostera. No further comment is offered in this section 128 /—. 6 I Eh 5 f3 ft 4 X -po o & o 3 0 tjo •H 1 -p n o •H 2 0) & w 1 W o •Hpq Fig. j,12. ZOSTERA SHOOT LENGTH, SHOOT MSS AND TOTAL BIOMSS IN RELATION TO PHYSICO-CHEMICAL FACTORS - BEVANS ISLAND SITES A,B,C, NOVEMBER 1975. ^ Shoot length A Mass Zostera Shoots ▼ Total Biomass ■ Total Phosphorus-Sediment O Organic Carbon 129 ho 6 ^ 120 &H 5 4 G O rO a o o 5 •H % o 2 1 20 w ta $ o •H PQ 0 Water Depth ( cm ) Fig. 5.1% ZOSTERA SHOOT LENGTH, SHOOT MASS AND TOTAL BIOMASS IN RELATION TO PHYSICO-CHEMICAL FACTORS - GRIFFINS BAY SITES I,J, NOVEMBER y 1975. ^ Shoot length A Mass Zostera shoots ▼ Total Biomass * Total Phosphorus - Sediment O Organic Carbon 130 -p a o ho 6 —120 Ph I Eh 5 100 ft c 0) 4 I—I 80 c o -p p o a o o 0 •H 3 1 o p ■& •H 2 0) £ 40 w 1 w cti a o •H pq D E F Sites off 2W1 Radio Transmitter Fig. '3.14. ZOSTERA SHOOT LENGTH, SHOOT MASS AND TOTAL BIOMASS IN RELATION TO PHYSICO-CHEMICAL ■r FACTORS - NOVEMBER 1975. • Shoot length A Mass Zostera Shoots ▼ Total Biomass ■ Total Phosphorus - Sediment O Organic Carbon w Water Depth 4 BIOLOGY OF ZOSTERA CAPRICORNI IN ILLAWARRA LAKE 132 4.1 INTRODUCTION. In this project, investigations have been made of various aspects of the biology of Zostera. These include morphological variations and an assessment of diagnostic features used by various authors to distinguish between Z_. capricomi and Z, muelleri. Previous studies have reported upon the environmental range of Z. capricomi in other lakes, suggesting tolerance limits and optimum conditions. Results of field studies conducted in Illawarra Lake, to examine these limits, are discussed. Zostera biomass and its relationship to selected environmental factors have also been investigated. The findings of these studies in part corroborate and in other aspects disagree with published reports. Long term observations have been made of shoot length, together with the effects of flooding and turbulence upon leaf shedding. The flowering cycle and seed production have been examined over two seasons. Included are the first recorded reports and photographs of Z. capricomi seeds germinating, with some seedlings at the two leaf stage. Transplant experiments using Zostera turfs and rhizomes in undisturbed and dredged sediments are discussed. The recolonisation of dredged and accreting sediments, over prolonged periods^are also described. 133 4.2 TAXONOMY OF GENUS ZOSTERA. Three species of eelgrass are currently recognised in south-east Australia, These are: Zostera capricomi Aschers. Zostera muelleri Irmsch. ex. Aschers. Heterozostera tasmanica ( Martens ex Aschers. ) den Hartog. Hcterozostera is easily distinguished from Zostera by the number and arrangement of lateral bundles in the rhizome. Heterozostera has 4 - 10 lateral bundles in the outer cortex whereas in Zostera there are only two lateral vascular bundles in the inner region of the cortex. Z. capricomi and Z. muelleri are morphologically similar and in some instances are difficult to distinguish in the field. Several characters have been used by different authors. Wood ( 1959 a ) gave the following groups of diagnostic characteristics: M Z. muelleri Z, capricomi H. tasmanica Anthers 10 -11 Anthers 15-20, in Anthers 20-24, in alternate. 2 packed rows. 2 packed rows. Leaves up to Leaves from 45 - 100 Leaves from 45 - 100 c. 50 x 2 ram. x 4*5 nim. x 5 mm. One lateral bundle One lateral bundle Multiple bundles in on each side of on each side of intemode s. intemode. intemode. Fibres in inner Fibres in inner Fibres near . cortex. cortex. epidermis. Spathe obvious, Spathe obvious, Spathe conspicuous. not swollen. not swollen. Swollen. Fertile stem Fertile stem Fertile stem longer than barren longer than barren similar to barren stem. stem. stem. Wood ( 1959 a ) also stated that the features leaf apex shape and the number of interstitial nerves in the leaf blade ( diagnostic features proposed by Setchell, 1933 ) were of little 134 taxonomic use ( Plato 2 ). Den Hartog ( 1970 ) disagreed with Wood ( 1959 a ) and claimed that the leaf apex and interstitial nerves were useful diagnostic features. He also drew attention to the retinacula and root morphology as key characteristics. Den Hartog ( 1970 ) summarised the differences between Z. capricomi and Z. muelleri as follows : Z. capricomi Z. muelleri Leaf tip truncate; retinacula Leaf tip obtuse or truncate obliquely triangular to obliquely deeply notched; retinacula ovate 2/5 - 1 l/3 by 1 - 1 1/3 mm. obliquely ovate, 1 - l£ mm long. Nerves 3 - 5» rhizomes with 2 groups of roots at each node. or Nerves 3» rhizome with 2 Nerves 3> rhizome with 2 ( sometimes 1 - 4 ) roots at ( sometimes 1 - 4 ) roots at each node. each node. Thus according to den Hartog ( 1970 ) Z. capricomi may have 2 groups of roots at each node or 2 ( sometimes 1 - 4 ) roots at each node. In neither case is the leaf-tip notched. In his description of the species, he did allow for the " leaf-tip truncate slightly denticulate, seldom with a central cleft." p.84. Z. muelleri may be recognised by the presence of 2 ( sometimes 1 - 4 ) roots at each node of the rhizome. Most of the specimens observed in this study belong to Z, capricomi but others could not be identified positively owing to the lack of fertile material. On root morphology and leaf dimensions they appeared to be more typical of Z. muelleri ( Plate 3 )# The genus is being re-examined at the National Herbarium, Royal Botanic Gardens, Sydney 135 PLATE 2 Leaves of Zostera capricomi. Note that the three central leaves all show a notched leaf apex. The variation in the density and length of filamentous algal epiphytes is also shown. Size x 3 156 137 PLATE 3 A sample of Zostera from colonies in which the leaf length is usually about 5 cm,seldom exceeds 10 cm, the leaf apex may be either truncate or notched, and the rhizome produces only 2 roots at each node. Size x 2 138 159 4.3 DISTRIBUTION OF ZOSTERA IN ILLAWARRA LAKE. 4-3.1 Introduction. capricomi occurred abundantly in Illawarra Lake ( Fig. 3*9 )• Its major development was upon the sandy shallows of the Windang Peninsular and west of Bevans Island. Extensive growth also occurred in Griffins Bay, in the entrance channel, at the mouth of Haywards Bay and at the mouth of Mullet Creek. A narrow fringing growth, seldom more than 20 m wide, occurred in most other bays and in the outlet channel at Tallawarra Power Station. The inner portions of Haywards Bay supported no Zostera growth,while the beds that existed in Koona Bay near the mouth of Horsley Creek, and in Koong Burry Bay during 1972/73> had almost totally degenerated by 1976. Minor colonies also occurred in Mullet Creek and Hooka Creek. Small colonies, identified on vegetative features as Z. muelleri, occurred sporadically as a fringing growth in the shallows (<^ 20 cm water ), along the northern shore of Griffins Bay and the western shallows of Koonawarra Bay. Similar colonies existed on the northern side of the Tallawarra Power Station training wall in 1974 hut disappeared,presumably as a result of strong wave action during the summer of 1975- 4.3.2 Distribution of Zostera in Relation to Environmental Factors. Analyses of sediments and water samples were conducted to determine the environmental conditions under which Z. capricomi grew in Illawarra Lake. These several analyses have been presented and discussed in Section 2.2 and 2.% The environmental range of Zostera in Illawarra Lake, with regard to sediments, is given in Table 4*1. This lists the maximum and minimum values for percent sand, percent fines, percent organic carbon and total phosphorus COMPOSITION OF SEDIMENTS SUPPORTING ZOSTERA - ILLAWARRA LAKE 140 Hooka 141 ( pg P/g dry sediment ) from a number of localities that supported Zostera. Extreme ranges for particle size were sand 14 to 98 lor oganic carbon 0.5 to 12 $ and lor total phosphorus 55 to 120 ug P/g. pH and Eh determinations were limited to the eastern sands. They revealed a range of sediment pH of 7*4 to 8.0 and Eh of +10 to - 185 mV. Fig 4*1 shows the distribution of Zostera in relation to the distribution of sediments ( after Roy and Peat,1974 )• This supports the analytical findings that in Illawarra Lake, the distribution of Zostera was not limited by sediment type. The demise of Zostera in Koona Bay and Koong Burry Bay seemed to be related to the rapid accretion that occurred in these areas in recent years. Both areas supported Zostera in 1972. Other inhibitory factors must be operating at these sites. Zostera growing in other places within the lake were subjected to similar accretion and have been seen to recover. Burial and recovery of Zostera beds has been a frequent occurrence on the northern side of the entrance channel east of the Windang Bridge, on the delta at the lake end of the channel, in the shallows to the north of Cudgeree Island and the delta of the Griffins Bay tank trap. Similar burial, but less rapid recovery, has occurred at the mouth of Mullet Creek and Macquarie Rivulet. This development is clearly discernible from aerial photographs. Photographs taken during 1961 ( Greater Wollongong Area, R5, IO63 - 5109 ) show that at that time, the lake delta of the entrance channel was limited in development and fully colonised. By 1963 ( Kiama, R lk, 1189 - 5109 ) a large, uncolonised sand splay had developed. Photographs taken in 1966 ( Greater Wollongong Area, R 13, 1475 - 5023 ) show that this delta extension had been partly colonised. Since that time there have 142 Key: f Boundary to Zostcra growth / Facies change Sediment Types Quartzose Lithis Marine Non-Mar:ne Clean sand ( 5/o sand ) VA Muddy sand ( 50-95 /o sand ) Sandy Mud km ( 50-95 ./■; mud ) Fig. DISTRIBUTION OF ZOSTERA IN RELATION TO SEDIMENT TYPE ( facies changes after' Roy and Peat, 1973 )• 143 been repeated burials and regrowth as this delta continued to develop. As discussed in Section 2.3» water quality in Illawarra Lake was highly variable. Although the salinity was usually between 20 to 30 ioo , Zostera was seen flowering over a salinity range of 32 ioo , varying from approximately 3 in Hooka Creek to approximately 35 in the entrance channel. As no part of the lake was observed to have a salinity less than 12 for more than a few days, nor greater than 32 » it is concluded that salinity did not limit the distribution of Zostera in Illawarra Lake. During this study, surface water temperature was usually within the range 12° to 29°C; the minimum was 11°C. In the Tallawarra Power Station outlet channel, water temperature at times exceeded 35°C yet Zostera persisted at this site. It is concluded that water temperature did not limit the distribution of Zostera in Illawarra Lake since; the difference in temperature between various sites on the lake was always slight ( usually 3°C ), the vertical thermal gradient was <^1°C, and new growth was observed throughout the year. The nutrient status of the lake water, with regard to phosphate, was usually beyond the level of enrichment needed to promote nuisance algal blooms ( Sawyer in Higginson, 1971; Anon., 1975 > and Wetzel, 1975 )• The observed total phosphorus range for the whole lake was 4 to 145 pg P/l»with a mean of 46 pg P/l. Because the lake was turbulent and the phosphate level of the sediment was high, localised deficiencies in water phosphorus concentration would be quickly restored by water circulation and by disturbance of the sediment ( Wetzel, 1975 )• It would seem improbable that the distribution of Zostera would be limited by phosphorus deficiency. However, in 144 areas adjacent to some streams and in some bays, notably near Albion Creek in Koona Bay, in Kully Bay, Joes Bay, Why Juck Bay, and in the back channel behind Picnic Island, where the sewage effluent derived nutrient levels were high, the growth of Enteromorpha was so dense that Zostera grew sparsely or not at all. In this way, excessive phosphorus levels may have restricted the distribution of Zostera by interspecific competition, with the Zostera being excessively shaded by the floating Enteromorpha. Lake nitrate levels were usually lower than Tuggerah Lake ( Higginson, 1971 ) or Macquarie Lake ( Spencer, 1959 ) with a mean of 2 pg/l ( Kanamori, 1976 ). Samples from sites adjacent to the extensive eastern Zostera beds showed mean nitrate levels less than the lake mean. The highest values were obtained from sites adjacent to the western stream mouths, where the Zostera growth was much more sparse. Consequently it is argued that low nitrate concentrations did not limit the distribution of Zostera. However, like phosphorus, nitrogen compounds, in various forms, are abundant in sewage effluent. This nutrient would also have contributed to the massive algal growth that tended to exclude Zostera from the areas stated. The observed ranges of pH and Eh for lake water; 8 to 8.4 pH ( this study ) or 7.4 to 8.9 pH ( S.P.C.C. Table A2.12 ) and +310 to +350 mV Eh, were narrow. This, and the lack of a systematic variation between different areas of the lake suggested that it was improbable that either of these factors would have limited the distribution of Zostera. While no factor considered to this point ( sediment type, salinity, water temperature, nutrient status, pH or Eh ) would seem separately to be limiting to Zostera distribution, 145 the possibility of synergistic effects of two or more factors is acknowledged. One laboratory trial did indicate a response to salinity. Short lengths of young rhizomes,bearing 3 to 10 nodes and 5 to 30 leaves that varied in length from 4 to 18 cm, were transplanted into muddy-sand sediment in 2.5 litre jars, Five rhizomes were placed in each of 10 jars. The initial salinity was 14*1 $ lake salinity at the time of collecting the rhizomes. During the following 14 weeks, or while the rhizomes remained alive, the salinity was varied. Salinity reduction was achieved by dilution with water from Macquarie Rivulet ( made by the addition of seawater evaporated to approximately twice normal salinity. The rate of change of salinity and the survival time of the rhizomes is given in Table 4*2. From these data it may be seen that although all rhizomes died, those in a salinity of 25 to 30 lived the longest. It was also noted that the rhizomes deteriorated more rapidly in hyposaline than in hypersaline conditions. Of the environmental factors examined, turbidity appeared to be the most important in limiting the distribution of Zostera in Illawarra Lake. The relationship between Zostera distribution and water depth is shown in Fig. 4*2. In the entrance channel, which was twice daily filled with low turbidity seawater, Zostera grew to a depth of approximately 2 m. Throughout most of the eastern weed beds, the outer growth limit was usually found at 1.5 to 1.8 m, even though the sandy substrate continued beyond 2 m. In Griffins Bay and off the mouth of Mullet Creek,the depth limit was inside the 1 m contour. These sites, as indicated in Section 2.3.7, were more turbid than the eastern beds. Away from TABLE 4.2 ZOSTERA RHIZOME SURVIVAL AS A FUNCTION OF SALINITY S o M CD VO ro m 1 1 — — r r M — — • • 4^ 4^ £ I r M H • • O 4^ 4^ 1 1 1 — o r H OV ov H • • r- — • H O H • vo O H . • ( on 4^ M • 4^ • on on • on m ov ro • VJ1 OM VM on 4" 1 1 1 — — t Ov • ro on • o ro H — ro on • OV on on r • VO ro 1 O • ro on • OM M • OV VO • M on ro vo 4 4 4 O crv ro M M ro C\ • • • M 10 O ro • • om — ro . -400 H om 4^- vo • vo CD — • 146 om OM • VO on VO — vo on 4^ 1 1 j 1 OV — ro ro o OV • • • ro — • ro t VM OM • 00 vo OM 4^ o ro VO H • OM o o ( — OM vo VO • on on * J j — H ro H ro • o CD r OM ov OV • • od CD • om • — VO • on OM ro • vo 4v CD • OM on OM OM vo OM • — 4^ 1 ^. — ^ CD OD o OV o ON I • r • • • o ro ro OV • ro vo • CD 4=- om 4 4^ on • o ro OM OM on 4 on VO n 1 I ^ O I O — I O • 00 • O « ro ov • o\ ro 4^ 4^ OM on • t 4^ on • OM OM 4 on 4^ H-* O ' 1 I — r O O H- I OV I • • o ro 4^ OM OM on OM on • ro O ro • IO M 1 I I I I I I I m I ro ro • ro . — OM on f 4^ S u r v i v a l 1 1 — — o o 1 t ( W e e k s ) 5 *2 8 9 *2 1 1 1 5 * 5 1 2 # 5 1 0 . 3 4^ 147 Illawarra Lake [1 *2 m •2m Boundary to Zostera growth 1*0 m fl»0 m Contour - 0.5 m intervals Growth Limit of Zostera at site- water depth in metres THE DISTRIBUTION OF HOST FRA IN RELATION TO WATER DEPTH ( contours after Roy and Peat, 1975 ) 148 the eastern weed beds, Zostera was seldom observed to grow in water deeper than 1 m. The sites of nil or slow recovery following burial, were usually in deep ( about 1 m ) or turbid areas. In the highly turbid areas of Koong Burry Bay, Haywards Bay and Koona Bay, Zostera was dominated by Gracilaria, but in the lower turbidity conditions of the eastern weed beds, Zostera dominated Gracilaria. Griffins Bay, which was intermediate in turbidity, supported vigorous growth of both Zostera and Gracilaria. In this association,the relative abundance of Zostera would seem to be controlled by the turbidity of the water. Zostera appeared to be less turbidity tolerant than Gracilaria and was unable to compete effectively in the more turbid areas. Z_. capricomi in Illawarra Lake was tolerant of currents of several knots but appeared to be less tolerant of strong wave action. Extensive colonies thrived along the margins of the entrance channel where it experienced a strong tidal flow. Similarly the colonies in Mullet Creek and Hooka Creek were not obviously disturbed by flood flows. By comparison, an extensive growth of Ruppia in Hooka Creek was reduced considerably during the floods of June 1975 and March 1976. These Ruppia colonies showed no recovery up to the spring of 1976,but the less abundant Zostera has persisted. The Zostera growth on the outer perimeter of the entire eastern weed beds, was frequently subjected to strong wave action. This occurs when westerly and south-westerly winds gust up to 70 kilometers per hour ( Electricity Commission of N.S.W., 1971 )• On the eastern side of the lake, the intensity of this wave action was most marked along the Windang Peninsular which tends to shoal more rapidly than the Bevans Island bed. This effect was most marked just north of the inlet channel. At this point, the outer 149 growth limit fell well within the 1,5 m contour ( Pig. 4*2 ). Prom Fig. 4*1 and from evidence presented in this section, it is clear that this distribution was not a function of sediment type. This area was subjected to sand accretion during and since the 1960's,so it cannot be concluded with certainty, which factor has been most limiting. Further north, opposite the 2WL radio transmitter, shoaling was still rapid and wave action was still intense, but Zostera extended down to 1.8 m. On exposed peninsulars like Wollingurry Point, Tallawarra Point, Kanahooka Point and Wollamai Point, or in open bays like Tuggerah Bay, Yallah Bay, and Moureendah Bay, strong wave action periodically deposited several cm of sediment, but later removed it, exposing the underlying rock. Zostera has been unable to produce more than minor colonies in these areas. Small clumps of Zostera grew on rocky substrate in the lee of Gooseberry Island, but not on similar substrate on the exposed southern side of the island. During 1975-76, the Zostera beds on the northern side of the training wall in Yallah Bay degenerated greatly. This was coincident with periods of high wave action generated by persistent, strong easterly winds. Similar degeneration occurred at the mouth to Haywards Bay and in the beds to the south of Wollingurry Creek. Considerable sediment disturbance was also evident along the training wall and along the shore line south of Wollingurry Creek. The upper limit to which Zostera grew in Illawarra Lake, varied markedly. In Griffins Bay, along the Windang Peninsular and west of Be vans Island, the growth of both Ruppia and Zostera was sparse in water less than 40 cm deep. These shallows were the areas of most intensive feeding by ducks and 150 swans. Ducks have been observed, to feed upon the shoots of Zostera while swans feed upon the rhizomes of both Zostera and Ruppia. In axeas of the lake where swans were seldom observed, such as the back channel and east of the Windang Bridge, Zostera grew well in 15 to 20 cm of water. East of the Windang Bridge and in the entrance to Toubouree Lake, Zostera has been observed growing upon sandy sediments that were exposed at low tide. In September 1976, the lake fell to an unusually low level, exposing the Zostera colonised sediments of Koonawarra Bay. Several hundred black ducks ( Anas superciliosa ) congregated in this area and in the following 2 to 3 days the exposed Zostera and Ruppia were cropped to within 1 cm of the sediment surface. These several observations support the conclusion that in Illawarra Lake, the intense grazing pressure of the large population of ducks and swans limit the growth of both Zostera and Ruppia in the shallows along the eastern side of the lake. The greater abundance of Ruppia than Zostera in the shallows along the Windang Peninsular suggests that under these conditions, either Ruppia can better withstand and recover from grazing, or that Zostera is grazed preferentially. This second possibility is supported by the observation that in Koonawarra Bay, the cropping of Zostera was more intensive than that suffered by Ruppia. If ducks and swans do preferentially graze Zostera. then this factor could contribute to the absence of Zostera from Wollumboola Lake. 4*3*3. Zostera Biomass in Relation to Environmental Factors. In the survey of floral composition of the eastern seagrass beds, Section 3*4*5, the biomass of Zostera was seen to vary markedly 151 at different sites. In January 1976, the causes of this variation were investigated. Two sample transects were established west of Bevans Island, with a further two transects along the northern side of Griffins Bay. The Bevans Island sites were chosen because of their proximity to the entrance channel, while the Griffins Bay sites were chosen because of their remoteness from the entrance. The location of these sites is shown in Pig. 2.1,while a plan of sampling points along each transect is shown in Fig. Along each transect, sampling points were selected in areas subjectively chosen as representative of Zostera growth in the area. At each sampling point samples of sediments, water and Zostera were taken as described in Section 2 and 3* The results of sediment analyses are given in Tables A2.3 and A2.4, and water analyses in Tables A2.21 and A2.22. The significance of this environmental data has been discussed in Section 2.4. As in the earlier biomass survey, five plant samples were taken from each sampling point, washed, sorted and oven dried at 105°C. The categories used were living Zostera ( shoots and rhizomes), Ruppia, total algae, and unclassified organic matter ( decaying vegetable matter, mostly Zostera ). These data are presented in Table A4*l and A4*2. At neither locality was there an apparent correlation between Zostera biomass and the factors particle size, sediment pH or Eh, water pH or Eh, water temperature or water total phosphorus. The lack of correlation between Zostera biomass and sediment total phosphorus, as shown in Pig. 4«4» demonstrated that the growth of Zostera was not limited by the level of this major nutrient. Although this was the case, the concentration of sediment total phosphorus did have a moderating effect. At both P • VM VM • PO P Scale VM • VM S 2 S PO O O -P» vn * • VM 4^ 3 4^ • VM vn 4^ o\ ’ • VH r-i- I I I 1 P 8 c+ 4 O o p H> (SI CO c+ P P 2 S l I I I I <3 l I I ’ 9 Hj H) H* 4 ►3 CO co S § p p c+ o P P »i Hj c+ g o 152 ^ 1 ro po IV) • 4 O m P IS c+ P 4 * rv> po • rv) p v_n VN > CO P P o P 8 P O / „vn PO / 3 ^ X m 1 I- M o\ P p rc p • p . -Pi VJ1 < co P IP co c+- CO p CO M § o B H- VN 4^ PLAN OF ZOSTERA BIOMASS TRANSECTS - JANUARY 1976 ( Transect locations are shown on Fig, 2.1 ) 153 Zostera biomass ( dry weight, g ) (—1 f\J VM VJ1 o o o o o o H- Transects Griffins tM O Bay U1 •-3 I bd t—i tr* ti M i—i O tr1 « E H3 *: O t? I 6 ► <=! I—' CO VD—0 o o 154 sites, where samples were taken at the same depth, those of the higher biomass occurred on sediments with a higher total phosphorus content. However, although the sediments of Griffins Bay had a higher total phosphorus content than those of Bevans Island ( X,G.B. 84; X B.I. 69 pg P/g ) the biomass at Griffins Bay was only l/3rd to 2/3ras that at Bevans Island, for samples from a comparable depth. Over the long term of this study, it was noted that the salinity in Griffins Bay was more variable and generally lower than at the Bevans Island site. During the three month period prior to sampling ( the period of most active growth ) the salinity was stable at both sites. The difference between sites was approximately 2 °/oo ( Griffins Bay 31 » Bevans Island X ^ 32 %o , as shown in Table A2.18 ). Consequently, salinity differences have been discounted as an important factor in this analysis. There was however a distinct relationship between Zostera biomass and water depth, and therefore light intensity. Along the Bevans Island transect, Zostera grew to a depth of 1.2 m. At adjacent sites,patchy growth extended to a depth of 1.7 m. The most vigorous growth occurred in water 0.5 to 1.1 m deep,with a peak at 0.7 m. Beyond 1.1 m, growth was short and sparse. In water less than 0.4 m deep, Zostera shoots seldom exceeded 15 cm in length. At the Griffins Bay transects,no plant growth was observed in water deeper than 1 m. The most vigorous growth occurred within the limits 0.5 to 0.9 m with a peak at 0.85 m. The Zostera growth in water less than 0.4 m deep was short and sparse. These observations have been plotted in Fig. 4.5 and 4*6- The relationship between total plant biomass and water depth is shown in Fig. 4*7* 166 • Sample 60 » Mean value for site 60 -p fo •H0) 40 & w w 60 aJ 0 o •H aJ (Df-l 20 O(/) N] 10 • ■« • • 40 60 80 100 120 Water Depth ( cm ). Fift'. 4.6 ZOSTERA BIOMASS IN RELATION TO WATER DEPTH - BEVAN ISLAND - JANUARY 1976. Z o s te rb a io m a ss( d ry w e ig h t,g ) 10 20 50 0 Fig. ■Mean • 4.6 Discrete sample site 20 . 156 value DEPTH ZOSTERA Water biomass for - 40 GRIFFINS BIOMASS Depth 60 ( IN BAY cm RELATION ), - JANUARY 80 TO WATER 1976. 100 Total Benthic Flora Biomass ( dry weight, g ) Fig, A • 10 4*7 Griffins Bevans . 20 TOTAL Island 30 Bay BENTHIC 40 DEPTH - DEPTH Water 157 50 Depth FLORA JANUARY 60 ( BIOMASS 70 cm 1976. ) 80 IN 90 RELATION 100 110 TO WATER 120 158 Turbidity differences between the two sites was discussed in Section 2,where it was noted that Griffins Bay ( mean Secchi disc extinction ^ 1 m ) was usually more turbid than the Bevans Island site ( mean Secchi disc extinctions 1.4 m ). Hence light penetration at Griffins Bay would have been less than at Bevans Island and the compensation depth would have been deeper at Bevans Island than in Griffins Bay. These observations are consistent with the earlier conclusion that the depth limits of Zostera at any given site was a function of turbidity. The reduced biomass in water less than 40 cm deep was presumed to result from waterfowl and swan grazing pressure. Variables influencing Zostera biomass were shoot density ( turions or bundles of shoots per unit area ) leaf width, rhizome density and rhizome thickness. The length of the shoots can be used in only most general ways as an indicator of Zostera biomass but as shoot length was one of the more obvious and easily measured indicators of Zostera growth, the relationships shoot length v water depth and shoot length v biomass were examined. At Bevans Island, no functional relationship was observed between shoot length and water depth, within the range 0.6 to 1.1 m. In water less than 0.6 m deep, the shoots were usually short, probably reflecting grazing pressure. In water 1.2 m deep and deeper at other sites, shoots were also short, showing an apparent etiolation effect and probably reflecting reduced vigour as a result of lower light intensities. These data are given in Table A4.1 and the relationship shoot length v water depth is given in Fig. 4*8. That this reduced growth was a nutrient effect was improbable. The site 1.7 in 1.2 m of water hah a higher nutrient status than site 2.8 in 1.1 m of water, yet the mean shoot length at 1.7 was only l/5rd that at site 2.8. In Griffins Bay, a site that was more turbid Zostera Shoot Length ( cm Fig. • 4*8, Most Range 20 - BEVANS ZOSTERA common 40 growth SHOOT ISLAND 159 Water Depth LENGTH - 60 JANUARY IN RELATION ( cm 1976. 80 )• TO 100 WATER DEPTH 120 160 than the Bevans Island sites, no apparent etiolation effect was discernible, there being an abrupt boundary to the tall Zostera growth ( Pig. 4.9 ). Excluding the extremes of water depth, there was no functional relationship between shoot length and biomass of Zostera at the Bevans Island sites ( Tables A4.1 and Pig. 4*10 )• The exceptionally heavy growth at site 1.5 was reflected more in the apparent density of shoots, width of leaves and thickness of rhizomes, than in shoot length. In Griffins Bay by contrast, biomass tended to increase with increasing shoot length but as shown in Fig. 4*11 the relationship would seem to have little predictive value. Localities with the same shoot length may have widely different biomass,while localities with similar biomass may differ greatly in shoot length. The Zostera beds of Illawarra Lake were extremely variable in growth, a feature that rendered the selection of sampling sites a perplexing problem. This mosaic structure is clearly visible in aerial photographs taken when the lake turbidity and turbulence was low. To locate sites randomly would necessitate a much larger sampling program than could be undertaken in this study,where the emphasis has been upon a comparison of factors affecting growth vigour. Throughout this study, sites were chosen within areas that supported vigorous growth. To gauge the extent of this variability, two transects, each 220 m long, were examined on the Zostera beds west of Bevans Island ( Fig. 2.1 ) during January 1976. Measurements were made along the length of the graduated transect line. The observations recorded were shoot length, shoot density and incidence of flowering plants. Water depth was measured at 10 m intervals. 161 O Most common growth T Range Water Depth ( cm ). Fig. 4*9. ZOSTERA SHOOT LENGTH IN RELATION TO WATER DEPTH - GRIFFINS BAY - JANUARY 1976. 162 • Most common growth Range Mean Zostera Biomass ( dry weight, g ) Fig. 4.10. ZOSTERA SHOOT LENGTH IN RELATION TO BIOMASS - BEVANS ISLAND - JANUARY 1976. 163 • Most common growth T Range Mean Zostera Biomass ( dry weight, g ) Fig. 4*11* ZOSTERA SHOOT LENGTH IN RELATION TO BIOMASS - GRIFFINS BAY - JANUARY 1976. 164 This survey indicated clearly the wide variations in shoot length and shoot density that occur within Zostera beds. Along the transects studied, the observed variation in density wa3 0 io bare sand, 22 °/o sparsely colonised, 23 a/° supported medium density growth while 48 % supported dense Zostera growth. The density criteria used were; dense = continuous cover, medium 2 density = discontinuous growth with open spaces up to 0.25 m » and sparse = discontinuous growth with open spaces greater than 2 0.25 m in area. The observed variations in shoot length were; mean shoots 55 cm and longer 35 mean shoots 35 to 50 cm 28 c/o and mean shoots 30 cm or less 32 Colonies producing flowering shoots occupied 9 of the area, and were widely spaced. The absence of a functional relationship between shoot length and water depth was also apparent. These several observations are presented in Table A4.3 and summarised in Table 4*5 and. Pig. 4*12. ZOSTERA SHOOT LENGTH. DENSITY AND FLOWERING.220 m TRANSECTS - BEVANS ISLAND 165 Bare - 7 3.2 27 12.3 166 ) cm 1 ( Depth Transect Water fcJ B c+" co B o CD H* ] 167 2 ( 1 - O M H o VJl o Depth Transect o vn Water Fig. 4.12. VARIATION IN ZOSTERA GROWTH - BEVANS ISLAND - JANUARY 1976. £ Dense growth J|| Medium growth 1 | (Sparse growth • Flowers 168 4.4 GROWTH OF ZOSTERA CAPRICORNI IN ILLAWARRA LAKE. 4*4.1 Morphological Variations in Zostera capricomi. As the growth of Zostera capricomi in Illawarra Lake was highly variable, a study was made of the morphological variation shown by this plant. In November, when the new season growth was well developed, samples were collected from flora sites 1, 3 and 4 ( Fig. 2.1 ). Measurements and observations were made of the features described by den Hartog ( 1970 ). The variations noted are presented in Table A4.4. It is implicit in this comparison that the only characters listed in Table A4*4 are those found in samples from sites 1, 3 and 4 to be at variance with den Hartog*s ( 1970 ) description of Z. capricomi. It is stressed that all specimens possessed 2 groups of roots at the node of the rhizome, a key characteristic in den Hartog*s criteria for distinguishing Z, capricomi from Z. nruelleri. which has 2 roots at each node. These observations show that Z. capricomi exhibits a much greater morphological variability than recorded in the literature and that leaf apex shape is of little diagnostic value for distinguishing between Z. capricomi and Z. muelleri. 4*4.2 Vegetative Cycle of Zostera capricomi. Prior to this study, published reports contained only general references to the growth cycle of Z. capricomi. During 1972, and in subsequent years, observations have been made of seasonal variations in shoot length at a number of sites. While it was realised that shoot length varied within a Zostera bed, it was reasoned that the changes in shoot length at any one point would be a valid indicator of the growth cycle for that area. The sampling procedure involved careful location by triangulation of sighting lines. It was not practical to place 169 fixed markers as these interfered with the netting activities of fishermen and usually had a field life of only a few weeks. Compass sightings were also impractical in a rocking boat and resulted in site location errors in excess of 100 m. Sight triangulation was adopted as the most reliable procedure. Once the boat had been positioned, it was allowed to drift on a 20 m anchor rope. This permitted measurements over a large area so that errors of estimation could be avoided. The number of measurements varied between 10 and 20 according to the uniformity of the growth in the area. At each site the shoot length of the shortest, tallest and most common growth form was measured to the nearest 5 cm. This data ( Table A4*5 ) is summarised in Fig. 4*13 » 1-8. The record is unfortunately incomplete for autumn owing to the unavailability of a boat, but the general trend during this period is indicated. These data show a seasonal growth cycle for Zostera with maximum growth during the summer, and minimum standing crop during the winter. The onset of the new growth cycle usually occurred during August - September. During autumn and winter the previous seasons growth was shed. When observations began in January 1972, tall, vigorous growth existed at all sites, although the standing crop varied in height between sites. The second observations,during February 1972,indicated that this was the period of maximum standing crop,with some sites showing slight increases and others slight decline. By the time observations were resumed during July 1972,the decline in standing crop was slight at the inlet delta, Haywards Bay and Koonawarra Bay ( sites 1, 3 and 4 ) hut dramatic along the Windang Peninsular ( sites 5> 6> 7 and 8 ). Regrowth began at the southern end of the Windang 100 ) o © cm ( o\ o o length o w Shoot + o 3 c 1 H o o co ) o 170 cm Q\ o ( o length o ro Shoot Fig. 4,15. SEASONAL VARIATION IN ZOSTERA SHOOT LENGTH SHOWING THE RANGE AND MOST COMMON GROWTH, 1972 - 1973 ( C ont• ) 100 171 Fig. 4*15.( Cont.) SEASONAL VARIATION IN 20STERA SHOOT LENGTH SHOWING THE RANGE AND MOST COMMON GROWTH 1972 - 1973. 172 Peninsular ( site 8 ) in August, at the inlet delta, Haywards Bay, Primbee and opposite the 2WL radio transmitter ( sites 1, 5 and. 7 ) during September, but not until October at Bevans Island,in Koonawarra Bay and some areas of the Windang Peninsular ( sites 2, 4 and 6 ). At all sites shoots were growing rapidly during December - January. No decline in standing crop was observed at any site up to the end of January 1973* Rapid degeneration occurred during February and March, coincident with heavy rain. Similar rapid declines in the standing crop have been seen to follow heavy late summer to autumn rains in subsequent years. Marked leaf shedding followed the March rain of 1974> hut in 1975> when rainfall was 40 % less than average, little decline occurred until the June - July floods. In 1976, there was a dramatic leaf shedding during the floods associated with the February - March rains. These changes were most marked in areas covered by less than 0.5 to 0.6 m. In deeper water, leaf shedding seemed to be a progressive process and was not observed to occur as precipitously as in the shallows. This relationship between flood rains and leaf-shedding of Zostera is not easily explained, as the response varied at different sites. The decline was most marked on the eastern seagrass beds, while colonies in sheltered locations, like Haywards Bay and Koonawarra Bay ( sites 5 and 4* Fig. 2.1 ) or the beds along the southern shore, were little affected. Had leaf fall been a response to a salinity drop, increased turbidity or reduced temperature, one would have expected little difference between sites. It is suggested here that while those changes may contribute to the susceptibility of leaf shedding, a further factor, wind - induced wave action may be more significant. Those sites 173 that usually showed late decline ( the southern shores, Haywards Bay, Koonawarra Bay and Griffins Bay ) were little exposed to strong wave action and hence retained their growth longer. Normally, wave action over the eastern weed beds was suppressed by plant growth,but during periods of hign water, high turbulence has been experienced throughout the zone. The Zostera displaced at these times includes young green shoots as well as old, decaying, epiphyte coated leaves. Floods that had a marked effect upon the eastern weed beds had little effect upon the Zostera growth in Mullet Creek or in the entrance channel. It is suggested here, that while Zostera is tolerant of strong currents, it is damaged extensively by strong wave action, with only the young, short shoots ( Reference has been made earlier to variations between sites in the onset of new growth. Sites adjacent to the inflow channels ( 1, 2 and 8 ) usually began to show new leaf growth before sites remote from the entrance. Although sites 5, 6, 7 and 8 all occurred within the Windang Peninsular beds, and showed a similar growth cycle, new leaf development occurred earlier at site 8 than at the other sites. Site 8 was located adjacent to one of the lesser tidal channels that flow to the north of Cudgeree Island ( Fig. 4.14 )• The moderating effects of seawater in the spring would be to raise temperature, and reduce turbidity, thus promoting carbon assimilation. Salinity changes would also occur but from other observations it is considered not to be a controlling factor. 4*4*3 Flowering and Seed Production in Zostera capricomi. Little information on the flowering characteristics of Z. capricomi was available in the literature, so a flowering 174 175 survey was conducted concurrently with the growxh cycle study of 1972. Observations of numerous inflorescences revealed a set pattern of development. In the early stages the inflorescence , a spadix, is enclosed within a spathal sheath consisting of two, semitransparent, longitudinally overlapping flaps of tissue. The gynoecium matures before the androecium and the dual stigmata protrude through the spathal sheath* The roughly triangular retinacula, that usually accompany each stamen, recurve to force open the spathal sheath. This exposes the stamens which usually consist of two oblong^-ellipsoid, bilocular thecae. The thecae dehisce, releasing the filamentous pollen, and are shed. In this study, the terms used to indicate the state of maturity of the spadices were defined as follows: (a) A "juvenile" spadix was one in which the spathal sheath had not begun to open and no fertile parts of the inflorescence were yet visible, (b) A "mature" spadix was one in which the spathal sheath had begun to open and the stigmata at least were visible. (c) A "dehiscent" spadix was one in which the pollen had been shed. (d) A "deciduous" inflorescence was one which had been shed and only the short, rigid process at the base of the spadix remained. Immature fertile shoots were first observed at the beginning of September and towards the end of that month, when flowers were more abundant, an analysis of anther number and arrangement was conducted on samples taken from sites 3 and 4 ( Pig. 2.1 ). A number of fertile shoots were collected from each 176 site. A count was made of the number of spadices on each fertile shoot to gauge how long flowering had been in progress. In each spadix, where possible, anthers were counted and their arrangement was noted. Where the anther count could not be made, because the spadix was immature or had already shed its anthers, this was noted. These results are shown in Table A4*6. According to Wood ( 1959» a ) • Z. muelleri has anthers 10 - 11, alterante, and Z. capricorni has anthers 13-20, in 2 packed rows. In the majority of fertile shoots examined,anthers occurred in pairs, in two packed rows, but in numerous spadices, there was often an unpaired anther at one or other end of the inflorescence. The number of anthers per spadix, as shown in Table A4*6, was observed to vary from 11 to 28. In the fertile shoots examined, the anther arrangement was consistent with the criteria set by Wood ( 1959 a ) for Z. capricorni. however the anther count fell beyond the upper and lower limits set for this species by Wood ( 1959 a ). All flowering specimens collected subsequently from Illawarra Lake possessed paired anthers in 2 packed rows, apart from the single anther at either end of the spadix. The flowering cycle of Z. capricorni was examined at 8 sites ( Fig. 2.1 ). At each site the boat was allowed to drift over the sampling area on a 20 m anchor rope. Ten samples were taken, using a three pronged garden cultivator. The number of fertile ( flower bearing ) and sterile shoots in each sample were recorded and the fertile shoots were retained for measurement, and observation of the inflorescences. The result of this survey, presented in Table A4*7> show the number of sterile shoots ( S ) and the fertile shoots ( F ) 177 in ten samples from each of the sites on the four dates indicated. The columns have been totalled and the number of fertile shoots has been expressed as a percentage of the total shoots ( S + F ). These data have been plotted in Fig. 4*15* The site number is shown in the upper centre of each graph, eg. site 1 is shown a3 \^l/. Other data collected included the length of the fertile shoots, the number of spadices per fertile shoot and the state of maturity of these spadices. These data are presented in Table A4*8. No measurements of the length of fertile shoots were made for 3*10.1972 but measurements are given for each of the other sampling dates. An additional column,showing the number of deciduous spadices,is included in the data for 3*1*1973* The data from Table A4*8 have been summarised in Table A4#9 in which the abundance of each of the development stages of the spadices has been expressed as a percentage of total spadices. As the flowering of Zostera was quite patchy, an attempt was made to determine the reliability of the sampling techinique used to collect the data on the abundance of fertile shoots, as presented in Table A4.8. Five sets of 10 samples were taken from site 4* The results are summarised in Table A4.10 and demonstrate the reliability of the techinque. The reliability of the sampling technique is also demonstrated by two further sets of data: (i) The samples from site 4 on 3*10.1972, 3 days after the test samples yielded 13*2 °/o fertile shoots, compared with a mean of 13*1 $ from the test samples. ( Table A4*7)* (ii) Sites 6 and 7 on the Windang Peninsular appeared to be similar in terms of location, water depth, turbidity, substratum and wind exposure. One could expect comparable -£=• °/o ro Abundance 4^- /o ( 178 IV) Abundance Fig. 4.15. ABUNDANCE OF FERTILE ZOSTERA SHOOTS - ILLAWARRA LAKE 1972 - 1973 179 results from the survey of the abundance of fertile shoots at these sites. These data,extracted from Table A4.7,are presented in Table 4*4• TABLE 4.4 ABUNDANCE OF FERTILE SHOOTS. Date Site 6 Site 7 5.10.1972 l.4'$ 1.0 % 24.10.1972 9.8 $ 9.7 $ 12.12.1972 16.2 # I8.5 1° 5. 1.1975 9.1 $ 6.4 % Seeds were first observed during December. Observations of seed production are presented in Table A4.ll. The data of Tables A4.8 and A4.11 have been summarised in Table 4*5* A similar flowering survey was conducted in 1975-76 using the same sites as the November, 1975 benthic flora survey ( Fig. 2.1 ) that was discussed in Section 3• 4• 5• These data are presented in Tables A4.12 and A4.15. The 1972-75 survey revealed differences in the incidence and duration of flowering between the 8 sites. The onset of flowering at sites 2 and 4 wa3 earlier ( September ) than at the other sites ( October ). At sites 2, 5» 4> 6, and 7 a decline in the incidence of fertile shoots was evident in December,while at sites 1, 5 and 8 there was a continuing increase during January, when the final observations were made. It is important to note that the similarity between sites 1 and 8,both of which were adjacent to tidal channels, related to the growth cycle as well as flowering. Fertile shoots eventually detach as a result of basal decay of the stem. They were shed even though there were still a number of mature and juvenile spadices on the shoot, and continuing growth of the leaves was TABLE 4 .3 FLOWERING CHARACTERISTICS OF ZOSTERA CAPRIC0RNI CO H- O O • O • • h$ CO CD co CD CG • CD O H- O O O O CD CD CD CD CD c+- CD H* O c+ 1 1 1 j — o o o o O o I M M — h- CO r\o o a t ro \_M • -f** -P* — -p* 180 J j O H O ON f\0 ON • H M 00 * 00 NJ1 4^ ino ro H M — r\o • — 1 J o r\o ino ON ON M K O ON -0 VM -J v>J -P- V_M — D ata e x tra c te from d T ab les A4*8 and. A4*H 181 indicated by their bright green colour. The detailed analysis of flower development ( Table A4.8 and summarised in Table 4*5 ) showed that there was no relationship between the length of the fertile shoot and the number of spadices, that new fertile shoots were produced as late as January and the number of spadices per fertile shoot was highly variable. Flower production was a continuous process through the period September to March,but limited seed production was observed to be restricted to the period December to March. By Janaury, the proportion of spadices still on a fertile shoot may represent as few as 50 % of the total spadices produced to that date ( Table A4.9 )• The observed rate of seed production seemed to be remarkably low. Only 2.6 °fo of flowers produced seeds during January. This suggests that the first half of the flowering season and for a large percentage of the flowers, no seeds were produced. No seedlings were observed. Attempts to germinate seeds in laboratory conditions were singularly unsuccessful. Observations of flowering during 1975-76 confirmed most of the 1972-73 observations but revealed some important differences. On 20.7#1975» 50 fertile shoots were collected adjacent to site B ( Fig. 2.1 ) west of Bevans Island. The presence of these shoots was striking as at the time, most of the old leaves had been shed, leaving only short vegetative growth <^15 cm long. These fertile shoots were 50 to 60 cm long and bore the processes of numerous deciduous spadices, estimated at between 12 and 30 per shoot. Only those spadices extant were counted. Of the 207 spadices borne by these shoots, 103 were dehiscent, 51 were mature and 53 were juvenile. No seeds were found in the dehiscent spadices. All of these fertile shoots were shed in mid-August. These observations extended considerably the recorded flowering period of 182 Z. capricorni and confirmed the production of juvenile flowers late into the winter. Six of these fertile shoots were most unusual in that they produced, from within the spadix cluster, lateral 'branches that bore sterile shoots. In 1975» new season fertile shoots were first observed in October. Flowering was widespread by November. The structure and development of the fertile shoots were the same as observed in 1972 but they were less abundant. The highest incidence of fertile shoots in relation to sterile shoots was 25 % as compared with 54 % in 1972. By contrast, the observed maximum seed production at 10.9 $ of flowers was 4 times that noted in 1972. Seed production was first noted in November in the 1975 survey, one month earlier than in the 1972 survey. Flowering was terminated abruptly in 1976 with the rapid shedding of fertile shoots following the heavy January rains. While sorting the benthic macrofauna collected from the Bevans Island site 15*7*1975* two germinating seeds, suspected to be the seed of Z. capricorni. were found. On 20.7*1975* three sediment samples, each 5 cm deep x 20 cm square, were collected from the area adjacent to site B ( Fig. 2.1 ) that supported the long-surviving fertile shoots. These samples were washed through a 0.75 mm sieve. This process, which took 6 hours, yielded 25 germinating seeds and I69 non-germinating seeds. A second set of sediment samples of the same dimensions, collected on 22.7*1975 and sieved in the same way, yielded 66 seeds and 5 seedlings. These seedlings showed an emergent plumule and like Z. marina ( Tut in, 1942 ) no primary root developed. One seedling was at the two leaf stage and showed the developing rhizome, with one node clearly visible. Photographs of these germinating seeds and 183 seedlings are presented in Plate 4. No previous record of the germination of Z. capricorni seeds, has been found in the literature 4*4*4 Proportion of Z. capricorni in Illawarra Lake. Effective lake management may require that areas be dredged to provide boat access or to maintain the body of water against rapid accretion. To stabilise the dredged-disturbed sediments and to maintain the biological diversity of the infauna, it would be desirable that such areas be recolonised rapidly by benthic flora. Natural recolonisation seems to proceed very slowly. Yallah Bay, in the section adjacent to the power station training wall, is one site where voluntary recolonisation is known to have occurred. During 1974* the distribution of Zostera in Yallah Bay was examined. This area has been subjected to major alterations resulting from the Tallawarra Power Station development. The work undertaken included reclamation, dredging and the construction of a rock training wall in 1951-52. A shallow channel was enclosed by the training wall, thus separating the hot water outflow of the power station from the intake of cooler water in Yallah Bay. Dredging occurred at the inner end of the outflow channel and at the mouth of the inflow channel. The reclamation obliterated existing Zostera beds and created new shallows that could be colonised. Pig. 4*16, drawn from aerial photographs taken in 1949 ( Kiama, R 2K, July 49, 261-37* Lands Department ) and 1974 ( Electricity Commission property, 6-2-74, 1450* Austrlian Iron and Steel ), shows the changes in the shore line and the extent of the disturbance of benthic flora associated with this development. Water depths prior to the power station development, as indicated on Tallawarra Power Station Water System Layout, Drawing TA, 18B, 184 PLATE 4 Germinating seeds and seedlings of ^ostera capricomi. Germination commence: with the rupturing of the testa by the expanded and protruding scut: .lum tnat supports the hypocotyl and coeloptile enc ?sed plumule ( inset ). The testa has be3n removed fre the upper right germinating eed. The plum ;.„e is just eme *ing from the coleoptile the smaller eedling on the right. As s...own on the lax ;er seedling or ,he 3eft, numerous long fine hairs d. relop at the \.se of the hypocotyl tu, the first rc :-s develop ad-'- ititiously, ae i pair, at th first node of ;he hypocotyl. Size x 5 185 186 ] ■ ’49 Water depth ( rn ) 1974 Water depth ( in ) 1974 Zostera growth Pith - Thung - Nar Bay 1949 Zostera growth Post 1951 Zostera growth 1949 Shoreline Reclaimed area 1949 Zostera growth Tallawarra power station Lr.-let channel Reclaimed area Yailah Bay Post 1991 Zostera growth Transects as shown on Fig. 4.IB Transects as shown on Fig. Training wall Outlet charmc1 1974 Zostera remnant growth 1 949 Zostera growth CHANG!-;:: rw zhornlinh and o.r 'rtbution 1 . Y ....A" B ii - 1949 TO 1 >74. 187 of 1951t are shown at selected sites, while current water depxhs are given beneath in brackets. These observations show that prior to the power station development, the shallows of Yallah Bay supported a continuous fringing growth of benthic flora, reasonably assumed to be Zostera. The present Zostera growth in the outlet channel represents either the degenerate remnants of the pre-power station colonies, or growth that has regenerated subsequent to development works. No record exists of dredging in the lower half of the outlet channel, so the former is the more probable. These patches, that, measured 1 to 10 m across, occurred at a depth limit less than the 1949 colonies. Degeneration of Zostera in the outlet channel, would be consistent with a raised compensation depth,resuiting from increased temperature^ and reduced light intensity as a consequence of increased turbidity. The post 1951-52 shore-line stands in what had been 1.8 to 2.2 m of water. In 1949» this zone supported no Zostera. Since the wall was constructed, sandy sediments have accumulated in the south-west comer of Yallah Bay, producing a substrate that has been colonised by Zostera. During the same period, there has also been an extension of the beds in the adjacent Pith-Thung-Nab Bay ( Pig. 4*16 )• These sites are important as they are the only ones for which there exists objective evidence of new colonisation, of recently accreted sediments,in areas that did not previously support Zostera. They are the only recognised sites of recent extensions to existing colonies of Zostera anywhere on the western side of the lake, during the last 25 years. To assess the extent of the colonisation adjacent to the reclaimed area, water depth and Zostera distribution 188 was examined along 8 transects, as shown on Fig. 4*16 and 4*17* The majority of plants growing at this site were morphologically typical of Z. capricomi. One cluster of small colonies of Zostera. thought to be Z. muelleri, bearing shoots 5 to 10 cm long and only two roots at each node, were observed in the shallows along and adjacent to transect 5* No fertile shoots were found. Some aspects of the Z. capricomi growth in this area were notable. At transect 5» the most vigorous Zostera colonies occurred on and between rocks that were encrusted with the mussel Mytilus. In these clusters, the Zostera grew densely to a height of 45 cm in 75 cm of water while in the adjacent sediment, the growth was sparse with thinner turions and a shoot length that varied from 15 to 20 cm. This luxuriance of the Zostera growing in association with the Mytilus suggested that the Zostera may derive nutrients from the excretion of the mollusc. Also, at this site, Zostera grew to a greater depth (bs 1 m ) than at any other site on the western side of the lake. It is particularly significant that no Zostera grew along the outlet channel side of the training wall ( transect 7 ) even though the sediment was similar to that at transects 2 and 5 and the water depth was only about 0.5 m. This supports the contention that a thermal effect may have adversely affected Zostera growth at this site. Fragments of Ruppia rhizomes were commonly observed in the outlet channel and in Yallah Bay, but no Ruppia became established. A further site, where Zostera beds had been dredged, wa3 located on the eastern side of the lake. A channel, 10 m wide and 2 m deep, was dredged along the shoreline north of Cudgeree Island in 1966; it has remained uncolonised. Only minor invasion 189 Fig. 4.17. YALLAII BAY TRAINING WALL PROFILES. 190 has occurred from adjacent,dense Zostera beds. This channel has been used intensively by power boats during' the summer tourist season. The resulting turbulence and increased turbidity may have inhibited recolonisation. Because rapid accretion of sediments is occurring in Illawarra Lake, lake management may require the dredging of shallows and the rapid recolonisation of disturbed sediments. Successful transplants of Z. marina sods,on the east coast of America,were reported by Phillips ( 1974 ) who reviewed the chequered history of seagrass transplant experiments. To assess the response of Z. capricomi to transplanting,several trials were conducted during 1975» using three sites ( Fig. 2.1 ). These trials were commenced in the outlet channel to Tallawarra Power Station in June, 1975» using sods and washed rhizomes. Transplant material was obtained from Koonawarra Bay and from beds adjacent to the transplant site. Four rows,10 m long and 1 m apart,were planted. The first row contained 20 sods of Koonawarra Bay Zostera, approximately 10 cm x 20 cm in size, bearing about 30 leaves, and with the roots embedded in little-disturbed sediment. The second row was planted with 20 sets of washed rhizomes that bore 5 to 20 leaves each. Row 3 contained 20 sods from the adjacent Zostera bed,while row 4 was planted with 20 sets of washed rhizomes and shoots from the 3ame bed. The transplant method involved digging a depression 5 to 10 cm deep into which the transplant material was placed. The sediment was then moved around the transplant and firmed. By early September, 8 sods in row 1 and 6 sods in row 3 had become established and had started to spread. The largest covered an area 25 x 40 cm. No live Zostera was visible in the rows that had been planted with washed rhizomes 191 Subsequently, during late September and early October, 4 further transplant trials were conducted using sods only. The sites, number of sods, origins of transplant material and dates of transplanting are given in Table 4*6, The sites into which the sods were transplanted were areas of bare sand within existing Zostera beds, and a 3 i x 3 m site in Griffins Bay that was hand dredged to a depth of 20 cm during September, 1975* During the following 3 months, all transplants remained green in colour and most showed signs of spreading, with numerous new rhizomes visible. As persons unknown removed the markers used to locate the Bevans Island site, it was not possible to recognise these transplants after the January flood. Consequently their longer term progress is unknown. Similarly the trials on the dredged site in Griffins Bay were inconclusive owing to the accumulation of abundant Gracilaria during January. Floating fragments of this alga settled in the dredged depression, smothering the transplanted material. Only one sod, which from the beginning carried longer shoots than the other sods, survived until May but it too degenerated. All of the sods transplanted into the bare sand area in Griffins Bay survived but did not spread greatly. By comparison, the sods transplanted into the back channel at Tallawarra Power Station have thrived. Both the June and October transplants spread to at least 2 to 3 times their original area. The rows of the June transplants merged to form a continuous bed 12 m long and 6 m wide. During September, 1975* a second 3 m x 3 m area was hand dredged to a depth of 20 cm. This dredged site was located west of Bevans Island and adjacent to the Zostera biomass transects ^ 9 S3 o o 02 CO e . 4 H* CO tr CO H* 1 h- O S' M 4 Hj H* Hj H O Q • • • • On On on -0 on / / _ bd 3 — -P* ^ V * j 0 o — ro ro • ON -0 on vo --3 vjn — vo — (■ vn 192 1 s — H- ro -- 4^ ' o H* ON H • • — • . -J VJl V>J ( ' s ' — _ t O O — ro + ro ro t _ ^ * Numbers in brackets indicate the number of transplants + Griffins Bay 1 = dredged site. 195 ( 2,1 ) discussed earlier. Sediment samples from this site were analysed and the results were discussed in Section 2. Following dredging, the site was left bare to allow for voluntary recolonisation. By mid-November, Zostera rhizomes had extended 50 cm into the dredged area. Some regression occurred in January-February, coincident with flooding. By June, numerous rhizomes had colonised about l/^rd of the dredged area and bore shoots 5 - 10 cm long. Two rhizome fragments, bearing 5 and 11 shoots respectively, lodged in the area during December. These took root and were still present in June, 1976. No seedlings were observed. In the 1972 algal epiphyte survey, it was noted that the Zostera at site 4» in Koonawarra Bay, supported no epiphytes. The leaves were shorter and wider,while the rhizomes were thicker than on Zostera from most other sites ( Table A4.4 ). Consequently, before the sods were transplanted, measurements were made of leaf length, leaf width, rhizome thickness, length of intemodes and abundance of epiphytes. Although these features were different in Zostera from the different sites, all sods, regardless of origin, produced uniform growth at the transplant site. Site 4 sods bore sparse algal epiphytes in Griffins Bay and in the Tallawarra channel while Zostera at site 4 remained free of epiphytes. It is concluded that these morphological and epiphytic association differences, even though marked at site 4» were phenotypic. Phillips ( 1974 ) also reported that most transplants grew to be morphologically similar to the indigenous population and concluded that for the material he studied, most morphological variations were environmentally induced. This does not exclude the possible existence of distinct genotypes but they have yet 194 to be identified. With the success of these transplant experiments, the way is now open to establish clones from more widely separated populations. 195 4.5 CONCLUSIONS RELATED TO PUBLISHED WORK. Previous studies of the "biology of Z. capricomi have been published by Wood ( 1953* 1959 a,b, 1964 )> Higginson ( 1965» 1971 )» den Hartog ( 1970 ) and. Aston ( 1975 )• Studies of the related species, Z. marina, by McRoy and Barsdate ( 1970 ) demonstrated the ability of this species to recycle sediment phosphorus, releasing it into the water column. McRoy ( 1974 ) also described the functional relationship between light intensity and carbon assimilation, while Backman and Barilotti ( 1976 ) reported upon the effects of irradiance reduction upon the standing crop of Z. marina. The importance of eelgrass to the fishing and oyster industries have been discussed by Dexter ( 1950 ), Imai ( 1951 )» Thomson ( 1959 a, b,e ), Pollard ( 1976 ) and Adams ( 1976 a, b ). Zostera capricomi is an euryhaline species. While there are experimental results and field observations that suggest that the plant grows best within a range of approximately 20 to 35 > it has been observed to flower in and survive both extremes of salinity and rapid fluctuations. Higginson ( 1965 ) reported a salinity range in Tuggerah Lakes of 3 to 34 and Higginson ( 1971 ) a range of 5 to 49 °/°° • Wood ( 1967 ) reported a salinity maximum in Illawarra Lake of 42 °/oo • In Illawarra Lake, Zostera was observed to grow and flower at sites that experienced at least several weeks of salinity^3 %o ( in Mullet Creek and Hooka Creek ). A salinity drop of 15 /&# in three days ( Griffins Bay, June, 1975 ) had no obvious effect upon the Zostera beds. The distribution of Zostera within a lagoon is limited 196 by water depth. Wood ( 1959 a ) concluded that Zostera required •’good" illumination so it did not grow well in turbid water. Consequently, the depth limit is a function of turbidity. Experimental evidence to support this conclusion was provided by McRoy ( 1974 )• He demonstrated the maximum rate of carbon uptake occurred at 50 % of surface illumination. The light half-saturation constant, that is the light intensity at which one-half of the maximum rate of carbon uptake occurred, was determined at 12.5 $ of surface intensity. Backman and Barilotti ( 1976 ) investigated the effects of light intensity upon eelgrass biomass by covering sections of Z. marina with canopies. These covers reduced the downwelling illumination by 63 $. This created in water 1.5 m deep, the optical conditions prevailing at 2.5 m, the observed depth limit of Zostera at the experimental site. Marked degeneration in the number of turions ( the bundles of shoots that grow from the rhizome ) occurred within 18 days. After removal of the canopies, the turions recovered at a rate proportional to the duration of the shading. The observed depth limits of Z. capricomi %from low tide to 6 m in Macquarie Lake ( Wood 1959 b ), to 2.5 m in Tuggerah Lakes ( Higginson, 1965 ) and to less than 2 m in Illawarra Lake, reflected a corresponding difference in the turbidities of the three lakes. The direct relationship between differences in turbidity and depth limits for Zostera in Illawarra Lake, confirms that Z. capricomi is limited in its distribution by illumination. It is also noted that the summer growth cycle of Z. capricomi coincides with the period of highest turbidity. In Illawarra Lake,it was noted tnat there was a fair agreement between the Secchi disc extinction depth, which approximates the half-light saturation constant for Z. marina, 197 and the depth limit of Z. capricomi. This suggests that mean annual Secchi extinction depth may be a useful indicator of the depth limits for Z. capricomi. Prom this evidence, and field observations,it is noted that approximately 80 $ of the floor of Illawarra Lake lies beyond the depth limit of Z. capricomi. Current tolerance by Zostera has been noted by Wood ( 1959 a ) and Higginson ( 1965 )• In Illawarra Lake, flood flows through Mullet Creek and Hooka Creek had no noticeable effects upon Zostera colonies. Zostera thrives in the entrance channels of many coastal lagoons, where it is subjected to strong tidal currents. The massive shedding of leaves coincident with periods of high turbulence, indicates that Zostera beds are damaged by strong wave action. Higginson ( 1965 ) concluded that the distribution of Zostera in the Tuggerah Lakes was a function of sediment distribution. Zostera was restricted to the sandy or muddy-sand sediments. Wood ( 1959 a ) noted Zostera growing on muds in Macquarie Lake. The Eh of sediments supporting Zostera in Macquarie Lake, varied from + 180 to - 150 mV ( Wood 1959 a ). Although the surface sediment was at times oxidised, the sediment in the root zone was usually reduced. Wood ( 1959 a ) concluded that Zostera grew best in reduced sediments. In Illawarra Lake, most sediments supporting Zostera were reduced and sandy, but varied greatly in texture, from clean sand to muds, with no apparent correlation between Zostera distribution and sediment type. Wood ( 1959 a ) reported that Zostera was slow to recolonise disturbed sediments. He suggested that sediments that were mobilised by currents or wave action became oxidised and so were unfit for further growth of Zostera. The recolonisation of 198 the sandy delta at the laxe end of the entrance channel of Illawarra Lake stands in contradiction of this view. As no information is available on the depth of this accretion, it is possible that some colonies simply recovered from burial by growing up through the new deposit. As Zostera is known to produce reducing substances ( Wood, 1953 ) the redox potential could have altered as the sediments were restabilised. The long time-lag between the main accretion and recolonisation, a period of several years, precludes total regrowth from buried rhizomes. Recolonisation was most probably achieved by surface rhizome extension. At the Bevans Island dredge site, which was in a lentic situation, it was noted that the sediments became reduced, presumably from the accumulation of organic matter, before much rhizome invasion occurred. Zostera did not colonise the floor of the entrance channel. In this situation, growth would not have been prevented by illumination as the channel was shallow, but the sediments were highly mobile and oxidised. Wood ( 1959 a ) reported that Zostera grew rapidly during the spring-summer, but during the winter, the leaves were shed, resulting in seagrass flats that were bare except for a network of rhizomes. Studies in Illawarra Lake confirmed the seasonality of the growth,but the timing of leaf shedding was more variable than suggested by Wood ( 1959 a ). This study also revealed the role of turbulence in promoting leaf shedding, regardless of the season. On only one occasion in the period 1972 to 1976 was any Zostera bed of Illawarra Lake denuded, by agents other than grazing, to the extent suggested by Wood ( 1959 a ). This bed was in the very turbulent shallows of Moureendah Bay ( Fig. 2.1 ). Commonly, the winter standing crop, in the shallows « 0.5 m ) west of Bevans Island, was only 5 to 10 cm tall,but in 199 the deeper water it was seldom less than 30 cm. In some years ( 1974 > 1973 ) the Zostera shoots in water approximately 1 m deep, west of Bevans Island,was continually longer than 50 cm. According to Wood ( 1959 a ) flowering of Z, capricomi extended from October to March. Both den Hartog ( 1970 ) and Aston ( 1975 ) reported a flowering period from September to March, with fruit production extending from October to March. In Illawarra Lake, flowering commenced in September and extended into late July. In some years ( 1976 ) flowering may cease abruptly with the massive shedding of fertile shoots during floods. Fruiting in Illawarra Lake was observed from October to June. Wood ( 1959 a ) noted the patchiness of the flowering, a feature that has been confirmed in this study. The January 1976 transects west of Bevans Island ( Fig. 4»12 ) taken at a time when flowering would be expected to be at a peak, revealed that only 9 n/° of the colony was flowering, and the patches of fertile shoots were widely separated. The abundance of fertile shoots varies from year to year, with many more flowering colonies observed in 1972-73 than 1975-*76* This study revealed the continuity of the production and multiplicity of spadices,as well as the longevity of fertile shoots. The low rate of seed production was also shown. This study also established that seeds of Z. capricorni germinate in the field and survive at least to the 2 leaf stage. Wood ( 1959 a ) noted Zostera seedlings at Paynesville, on King Lake, Victoria. These must be either Z. muelleri or H. tasmanica as no Z. capricomi has been recognised from that lake. ( Wood 1959 a; Aston, 1973 )• From his observations of the low frequency or assumed absence of seed germination, Wood ( 1959 a ) concluded that 200 propogation of Z. capricomi must be largely vegetative, but offered no evidence other than failure to observe seedlings. Studies in Illawarra Lake have established that propogation by seeds does occur. Observations of volunteer rhizome invasion from adjacent colonies and the settling of drift material on the Bevans Island dredge site established that vegetative propogation can occur not only by colony increase. The success of the transplant experiments demonstrated that artificial propogation is possible and could be useful in lake management. In his study of Macquarie Lake,Wood ( 1959 b ) suggested that seagrasses obtained nutrients from both the mud and the water. McRoy and Barsdate ( 1970 ) established that the related species, Z. marina.absorbed phosphorus from the sediment and secreted phosphorus compounds into the overlying water. While this capacity has not been investigated for Z. capricomi. the implications are important. Estuarine sediments act as a phosphate trap ( Jitts 1959 ) and consequently hold reserves of phosphorus many times greater than the lake water. While the overlying water remains oxidised, this phosphorus remains immobilised in the sediment. However, if Z. capricomi behaves as a phosphorus pump, much like Z. marina does, then the consequences may be continuing high levels of phosphorus in the water column,with attendant algal problems, even if phosphorus inflow to coastal lagoons could be controlled. Resolution of this question is eminently suitable for further study. Zo3tera is known to tolerate a wide range of temperature. Wood ( 1959 a ) reported that it survived in water too hot to walk in with comfort; a temperature which killed Gracilaria.From that report and field observations from this 201 study, Zostera is known to tolerate a temperature range from 10°C to approximately 40°C. Concern has been expressed by Coulter ( pers. com. ) that degeneration of Zostera in Munmorah Lake ( one of the Tuggerah Lakes ), may be a consequence of hot water discharge from Mummorah Power Station, As indicated earlier, a temperature increase would accelerate the metabolic process and hence the respiration rate, resulting in a reduction in the compensation depth. Observations in the outlet channel at Tallawarra Power Station indicates some degeneration of Zostera colonies. There was an apparent retreat from the deeper areas. At this site, the issue was complicated by the high turbidity that prevailed in the outlet channel. Interestingly, the most vigorous growth of Zostera transplants occurred at this site. Only shallow water areas ( Earlier studies have also reported upon the relationship between Zostera and other organisms. The abundant epiphyte population of Z• capricomi observed in this study, is confirmed by the findings of Wood ( 1959 a ). Similarly, investigations of the benthic macrofauna in Illawarra Lake confirmed the findings of Powis ( 1975 ) that Zostera colonised sediments supported an abundant and varied fauna,dominated by only a few species. The grazing pressure of swans upon Z. capricomi in Illawarra Lake corroborated the observations of Wood ( 1959 a ) in Macquarie Lake. Intensive grazing of exposed Z. capricomi by black ducks, as observed in Illawarra Lake, provided evidence of a nutrient source not mentioned by Braithwaite ( 1975 )• 202 The morphological features used by various authors to distinguish between the species Z. capricomi and Z• muelleri were found to be of doubtful value. Den Hartog ( 1970 ) and subsequently Beadle, Evans and Carolin ( 1972 ) and Aston ( 1973 ) all quoted differences in the leaf apex, particularly the presence or absence of notching, as diagnostic features. Observations by Wood ( 1959 a ), confirmed in this study, have shown that the notching of the leaf apex is so variable in Z. capricomi to be of little taxonomic use. Similarly, the root morphology, as used by den Hartog ( 1970 ) and Aston ( 1973 ) presents a problem. Den Hartog ( 1970 ) suggested that Z. muelleri bears only two roots ( but sometimes 1 to 4 ) at the node while Z. capricomi usually produces 2 groups or roots ( but sometimes 1 to 4 ) at the node. This overlap in these two key characteristics is sufficient to render certain identification of some sterile material almost impossible. One of the sets of sods transplanted from Koonawarra Bay into the Tallawarra outlet channel, bore leaves 5 to 10 cm long with 20 °/> showing a notched leaf apex, and 2 roots at the node. These sods developed to produce leaves approximately 30 cm long, of which 5 % showed an apical notch, and rhizomes that bore 2 groups of roots at the nodes. 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WARINNER, J.E., and BREHMER, M.L., 1966 - The effects of thermal effluents on marine organisms. In : FORD, R.F., and HAZEN, W.E., ( ad. ), " Readings in Aquatic Ecology. " Philadelphia : Saunders, 381 - 393• WETZEL, R.G., 1975 - " Limnology. " Saunders, Phil. 666. WHITFIELD, M., 1969 - Eh as an operational parameter in estuarine studies. Aus. J. Limnol. Oceanogr., 14 : 547 - 558. WHITFIELD, M., 1971 - " Ion Selective Electrodes for the Analysis of Natural Waters. ” AMSA Handbook No. 2. Sydney : Australian Marine Science Association. WOOD, E.J.F., 1953 - Reducing substances in Zostera. Nature, 172 : 916. WOOD, E.J.F., 1959a - Some east Australian sear*grass communities. Proc. Linn. Soc. N.S.W., 84 : 218 - 226. 213 WOOD, E.J.F., 1959b - Some aspects of the ecology of Lake Macquarie, N.S.W., with regard to an alleged depletion of fish. VI. Plant communities and their significance. Aust. J. Mar. Freshw. Res., 10 ( 3 ) s 322 - 340* WOOD, E.J.F., 1959c - Some aspects of the ecology of Lake Macquarie, N.S.W., with regard to an alleged depletion of fish, IV. Bacterial and fungal studies. Aust. J. Mar. Freshw. Res., 10 ( 3 ) j 304 - 315. WOOD, E.J.F., 1964 - Studies in microbial ecology of the Australiasian region. C.S.I.R.O. Div. Fish. Oceanogr. Rep. 541. WOOD, E.J.F., 1967 - " Microbiology of Oceans and Estuaries.,, Amsterdam : Elsevier. WOOD, R.D., 1971 - Characeae of Australia. Nova. Hedwigia. 22 1 1 - 120. WOMERSLEY, H.B.S., 1972 - Reader in Botany, lecture notes. Adelaide University. Unpublished. YEZDANI, G.H., 1970 - A study of the quaternary vegetation history in the volcanic lakes region of western Victoria. Ph.D. thesis, Monash Univ., Melbourne. YOUNG, R.W., 1976 - Part 2 - Infilling of the lake. In : " Illawarra Lake ". Wollongong City Council. Wollongong. 6 APPENDIX 215 A1 TABLE Al.l CONDITIONS OF ENTRANCE CHANNEL OF COASTAL SALINE LAGOONS. Unless otherwise indicated data has been obtained from Lands Department aerial photographs. *Report of camping ground proprietors ©Personal observation. (Location of lakes shown on Fig. 1.1) Illawarra Wollumboola Swan Conjola Burrill Toubouree Willinga Lake Lake Lake Lake Lake Lake Lake July 49 1.7.72 8.1.69 18.3.67 18.3.67 18.3.67 18.3.67 open closed closed closed closed closed closed August 63 Nov. 73 4.2.72 8.1.69 4.6.72 4.6.72 4.6.72 open closed closed closed open closed closed U ^ov. 71 9pril 74 Nov. 7 3 4.6.72 Nov. 7 3 *Jan.73 to *Jan. 73 to closed open closed open open Oct. 73 Oct. 73 closed closed ^pen since 29.12.74 nov. 73 Dec. 71 closed open Nov.7 3 Nov.73 open open -Illawarra Fiff. Al.l. GEOLOGY OF ILLAWARRA LAKE AREA ( After Nashar, 1967 ). Qa - Quaternary alluvials Rh - Triassic Hawkesbury Sandstone Rn - Triassic Narrabeen Group Pi - Permian Illawarra Coal Measures Peg - Permian Shoalhaven Group Gerringong Volcanics Psb - Permian Shoalhaven Group Berry Formation 216 TABLE A1.2 WATER QUALITY - ILLAWARRA LAKE. (Site locations shown on Fic 1.2) E. coli Coliform Nitrites Phosphate Date /100ml /100ml P.P.M. pH P.P.M Brooks Creek _ 9. 2.71 2,160 TNTC .02 7.1 12. 5.71 12 450 .01 8.0 - 31. 8.71 1,008 7,500 - - - 2. 2.72 700 - - - - 1. 5.72 72 450 <.01 8.5 <.l 5. 6.72 4 500 <.01 8.2 <.l 4. 7.72 496 4,400 <.01 8.1 <.l 21. 8.72 160 5,000 .015 8.4 .65 11. 9.72 260 TNTC <.01 8.4 2.1 30.10.72 3,400 45,000 .023 7.1 6.0 18.12.72 20 2,000 .011 7.6 3.6 Mullet Creek - Point of Discharge into Lake. 9. 2.71 250 TNTC <.01 7.1 - 12. 5.71 - 70 <.01 7.8 - 31. 8.71 25 130 - - - 2. 2. 72 280 420 - - - 28. 3.72 - 9,500 <.01 8.1 .10 1. 5.72 - 330 <.01 8.5 <.l 5. 6.72 5 410 <.01 8.3 <.l 4. 7.72 7 - <.01 8.0 <.l Hooka Creek - Berkeley Boat Harbour. 9. 2.71 185 2,600 <.01 7.9 . 2. 5.71 18 1,600 <.01 7.2 - 31. 8.71 2 10 <.01 8.0 - 2. 2.72 - 960 - - - 28. 3.71 - 2,100 - 7.5 .12 1. 5.72 1 170 - 8.3 <.l 5. 6.72 1 100 <.01 7.8 <.l 4. 7.72 7 400 <.01 7.9 <.l Lake Heights Road - Entrance to Griffins Bay. 9. 3.71 4 930 <.01 8.5 - 26.10.71 2 260 <.01 7.6 - 2. 2.72 17 79 - - - 6. 4.72 - - <.01 - <.l 29. 5.72 4 320 <.01 8.5 <.l 13. 6.72 25 4,800 .015 8.3 .29 King Street - Southern End - Griffins Bay. 9. 3.71 - 4,352 <.01 7.7 - 26.10.71 - 600 <•01 7.8 - 2. 2.72 186 240 - - - 6. 4.72 TNTC TNTC .01 7.2 .3 29. 5.72 600 8,250 .15 7.5 .016 13. 6.72 875 TNTC .028 7.6 .09 Primbee Bay - Southern Side of Griffins Bay. 9. 3.71 12 100 <.01 8.4 - 26.10.71 - - <.01 7.8 - 29. 5.72 575 TNTC <•01 8.3 .13 13. 6.72 - 1,200 - 8.6 .09 Lake Illawarra - 1 Entrance tc) Sea. 9. 3.71 120 490 <.01 7.8 26.10.71 1 330 <.01 7.9 - 6. 4.72 450 7,500 - 7.8 .1 29. 5.72 34 1,860 <.01 8.4 <.l 13. 6.72 5 700 <.01 8.5 .13 TNTC = too numerous to count. Data source: Wollongong City Council Health Surveyer Council files, unpublished. 217 TABLE A1.3. VEGETATION OF GOOSEBERRY ISLAND, HOOKA ISLAND, AND WOLLOMAI POINT - RAIN FOREST REMNANTS. TAXA Point Hooka Island Island Wollomai Gooseberry Gymnospermae Family Podocarpaceae Podocarpus elatus Plum Pine X X Angiospermae Dicotyledonae Family Moraceae Ficus macrophylla Moreton Bay Fig X X X Ficus rubiginosa Port Jackson Fig X X Ficus henneana Deciduous Fig X Family Urticaceae Dendrocnide excelsa Giant Stinging Tree X XX Family Pittosporaceae Pittosporum undulatum Pittosporum X Family Sterculiaceae Brachychiton acerifolium Flame Tree X Pteridophyta Family Adiantaceae Adiantum formosum Giant Maidenhair Fern X 218 A2 TABLE A2.1 COMPOSITION OF SEDIMENTS SUPPORTING BENTHIC FLORA IN ILLAWARRA LAKE. (Site locations are shown on Fig. 2.1) Medium Fine Coarse Sand % Sand % Total Total Organic Sand % <500 to <250 to Sand % Fines Carbon Site >500ym >250ym > 63ym >63ym Silt % Clay % <6 3pm % 1 4 42 50 96 0.2 4 4 1.5 2 0.1 11 86 97 0.3 3 3 1.5 3 2 13 73 88 2 10 12 1.3 4 6 21 63 90 3 7 10 1.8 5 2 8 42 52 29 19 48 8.5 6 14 32 35 81 7 12 19 3.3 7 3 19 68 90 4 6 10 2.9 8 10 20 56 86 6 8 14 3.2 9 3 8 57 68 16 16 32 5.2 10 0.2 4 88 92 3 5 8 2.1 11 0.1 2 82 84 6 10 16 2.9 12 0.2 8 90 98 1 1 2 1.9 13 3 45 34 82 4 14 18 4.9 14 9 63 25 97 1 2 3 0.8 15 3 23 68 94 1 5 6 2.9 16 14 61 23 98 0.5 2 2 0.9 17 5 65 26 96 0.5 3.5 4 1.1 18 0.5 32 62 94 1 5 6 1.6 ' 19 2 39 41 82 13 5 18 4.6 20 4 53 34 91 6 3 9 2.2 21 9 71 17 97 1.5 1.5 3 0.5 TABLE A2.2 COMPOSITION OF SEDIMENTS - NOVEMBER 1975 BENTHIC FLORA BIOMASS SURVEY (Site locations are shown on Fig. 2.1.) ym % % % ym % sed. % ym ym >250 >63 Carbon Sand Sand Phosphorus P/g Sand mV Fines % <63 Sand to % >63 % to jim yg Eh. K Silt X Organic >500 <500 <250 Total Total Site Clay Total Fine Coarse Medium ft L A 4 54 34 92 1 7 8 1.1 63 7.7 -75 B 5 55 31 91 1 8 9 2.8 89 7.8 -95 C 4 50 34 88 3 9 12 4.3 120 7.4 -130 D 5 63 27 95 1 4 5 2.1 81 7.8 -65 E 5 64 26 95 1 4 5 2.0 111 7.6 -75 F 5 65 26 96 1 3 4 0.5 39 7.8 -20 G 9 73 13 95 1 4 5 1.6 49 7.5 -130 H 10 70 15 95 1 4 5 2.7 81 7.6 -105 I 3 26 62 91 3 6 9 2.8 105 7.7 -160 J 12 61 24 97 1 2 3 0.8 35 7.9 -70 K 8 73 16 97 1 2 3 0.8 39 8.0 +75 L 5 70 22 97 1 2 3 1.3 42 7.9 -80 M 5 71 20 96 1 3 4 1.3 44 7.6 -110 219 TABLE A2.3 COMPOSITION OF SEDIMENTS - ZOSTERA BIOMASS TRANSECTS - BEVANS ISLAND, ( Site locations shown on Fig. 2.1 and Fig. 4.3.) urn % % join dfi % % tn e um a) a. >250 >63 Carbon Sand Sand •h m Sand ft kO Phosphorus mV to >63 Sand % to % % jim V M g / g * p Eh. w Site <500 Coarse <500 Medium Fine <250 Silt Total Clay Organic Total £ ft X 1.1 4 51 38 93 1 6 7 1.7 65 8.0 -100 1.2 5 54 33 92 1 7 8 2.2 78 7.9 -105 1.3 5 57 32 94 1 5 6 1.3 53 7.8 -70 1.4 4 53 34 91 2 7 9 1.7 65 7.7 -110 1.5 4 52 33 89 4 7 11 2.2 79 7.4 -90 1.6 4 54 36 94 4 2 6 1.6 64 7.5 -90 1.7 5 61 27 93 1 6 7 0.9 59 7.5 -45 2.1 5 54 33 92 2 6 8 1.5 60 7.5 -70 2.2 5 53 35 93 2 5 7 1.8 77 7.8 -60 2.3 5 56 27 88 3 9 12 2.5 84 7.4 -60 2.4 5 58 29 92 2 6 8 1.3 68 7.6 -125 2.5 5 54 31 90 3 7 10 2.3 89 7.4 -120 2.6 6 57 30 93 1 6 7 1.6 76 7.5 -110 2.7 6 60 26 92 2 6 8 0.8 62 7.4 -65 2.8 5 77 15 97 0.5 2.5 3 0.8 53 7.6 -40 TABLE A2.4 COMPOSITION OF SEDIMENTS - ZOSTERA BIOMASS TRANSECTS - GRIFFINS BAY. (Site locations are shown on Fig. 2.1 and Fig. 4.3.) pm % % % p m <#> % pm ■o i ______>250 >63 Carbon Sand Sand 63 Phosphorus Fines KD mV CO % % % Sand to to A hg/g pm < * p Eh. X <500 Silt <500 Clay Site X Medium <250 Total Organic Total Coarse Fine ft ____ | 3.1 5 60 22 87 2 11 13 1.8 96 7.6 -125 3.2 3 34 52 89 4 7 11 2.3 67 7.7 -140 3.3 3 34 54 91 3 6 9 2.3 81 7.4 -90 3.4 3 36 52 91 3 6 9 2.3 77 7.5 -165 3.5 2 36 53 91 3 6 9 2.6 67 7.6 -155 3.6 3 26 48 77 16 7 23 3.2 105 7.4 -165 4.1 2 29 58 89 4 7 11 3.4 101 7.8 -175 4.2 3 34 54 91 3 6 9 1.5 68 7.9 -150 4.3 3 35 52 90 3 7 10 2.0 85 7.6 -110 4.4 2 37 51 90 4 6 10 2.3 96 7.6 -145 220 TABLE A2.5 COMPOSITION OF SEDIMENTS - BEVANS ISLAND DREDGED SITE (Site location is shown on Fig. 2.1) © Eh values determined at 5cm; mean of three values. © From 7.9.75 sampling depth, was measured from the top of the area that had been dredged to a depth of 20cm. i.e. 0 - 5cm is equivalent to 20 - 25cm original depth. ® Mean of 4 total phosphorus determinations. © Mean of 2 organic carbon determinations. 31. 8.75 -105 7. 9.75 +195 5.10.75 20. 1.76 5. 2.76 TABLE A2.6 TOTAL PHOSPHORUS CONCENTRATION OF SEDIMENTS - BEVANS ISLAND DREDGED SITE. Total Phosphorus concentration (pg P/g dry sed.) V>v\§ite Deptn\ 1 2 3 4 Mean Surface 77 63 113 71 81 5cm 34 29 36 33 33 10cm 35 37 53 24 37 20cm 31 28 28 24 28 30cm 31 32 30 19 28 40cm 26 16 14- 11 17 Total phosphorus in water sample collected on same day was 20.2 pg P/1. 221 TABLE A2.7 REDOX ELECTRODE - TIME TAKEN TO ACHIEVE STABLE POTENTIAL IN CLEAN SAND Time mV mV mV mV mV Min. 0 +390 +390 +350 +360 +380 +320 +285 +300 +300 +350 1 +260 +245 +250 +270 +300 +240 +230 +235 +240 +260 2 +230 +220 +225 +220 +250 +225 +215 +220 +220 +240 3 +220 +215 +220 +210 +220 +220 +210 +215 +210 +215 4 +220 +210 +210 +210 +215 +210 +210 +215 5 +210 Variation in final reading +210 to +220 mV Range = 10 mV Average time to achieve stable readings = 3.5 minutes. TABLE A2.8 REDOX ELECTRODE - TIME TAKEN TO ACHIEVE STABLE POTENTIAL IN MUDDY SAND Time mV mV mV mV mV Min. 0 -120 -130 -140 -150 -145 -110 -125 -130 -150 -130 1 -100 -120 -110 -140 -120 -90 -110 -115 -135 -110 2 -85 -100 -110 -135 -110 -75 -100 -100 -130 -110 3 -70 -100 -100 -130 -70 -90 -130 4 -70 -90 -90 5 Variation in final reading -70 to -130 mV Range = 60 mV Average time to achieve stable reading = 2.5 minutes. 222 TABLE A2.9 REDOX ELECTRODE - STABLE POTENTIAL OBTAINED BY REPEATED INSERTION 5CM INTO MUDDY SAND - mV Trial Sample Sample Sample Sample Sample 1 2 3 4 5 1 +430 +180 +260 +70 0 2 +310 +130 0 +220 +120 3 +160 +60 -150 +10 -140 4 -70 -10 -10 -90 0 5 -150 -190 -120 -170 -180 6 -50 +30 +60 -110 -190 X +105 +33 +7 -12 -65 Range +430 to +180 to +260 to +220 to +120 to -150 mV -190 mV -150 mV -170 mV -190mV = = = = = 580 mV 370 mV 410 mV 390 mV 310 mV TABLE A2.10 REDOX ELECTRODE - STABLE POTENTIAL OBTAINED BY REPEATED INSERTION 5CM INTO MUDDY SAND THAT HAD BEEN CAREFULLY STIRRED - mV Trial Sample Sample Sample Sample Sample 1 2 3 4 5 1 -150 -140 -150 -120 -200 2 -140 -140 -160 -160 -190 3 -170 -130 -160 -170 -180 4 -170 -140 -160 -170 -210 5 -170 -140 -160 -180 -200 X -160 -138 -158 -160 -196 Range -140 to -138 to -150 to -120 to -180 to -170 mV -140 mV -160 mV -180 mV -210 mV = = = = = 30 mV lOmV lOmV 60mV 30mV 223 TABLE A2■11a SALINITY (°/oo) AND TEMPERATURE (°C) FOR ILLAWARRA LAKE AND OCEAN (Location of sample site indicated in brackets beneath each value is given in Fig. A2.1) Date Salinity Temp. Mean Ocean Max. Min. Max. Min. Sal. Temp.|| Sal. Temp. 28. 1.72 1 16.429 10.726 1 22.8 21.4 1 14.063 22.0 |1 34.674 - (5) (8) (4) (7,10) 23. 2.72 18.815 17.057 21.7 20.0 17.748 21.1 34.895 - (ID (6) (3) (8) 11. 3.72 17.327 14.065 21.5 19.5 15.907 20.4 34.791 - (3) (8) (4) (8,10) 28. 4.72 18.278 15.054 18.5 14.6 16.499 15.5 35.160 - (ID (8) (5) (2) 30. 5.72 20.152 16.917 14.4 13.0 18.989 13.3 35.153 - (ID (8) (5) (8) 19. 6.72 21.889 17.623 14.6 13.3 19.946 14.0 35.110 - (11) (8) (6) (9) 29. 7.72 22.881 21.531 12.7 11.2 22.251 11.7 35.291 - (3) (8) (5) (8,9) 25. 8.72 25.739 22.942 16.0 14.4 24.046 15.0 35.030 16.1 (10) (8) (6) (7,11) 14. 9.72 25.986 25.239 15.6 12.9 25.677 14.5 35.178 15.7 (9) (11) (6) (8) 10.10.72 29.027 27.445 19.7 18.4 27.938 18.7 34.963 17.2 (10) (4) (5) (2,4,10) 14.11.72 25.006 22.405 21.0 18.8 23.439 19.4 35.063 19.1 (10) (8) (5) (9) 7.12.72 26.984 25.812 22.9 20.6 26.429 21.6 34.994 21.1 (7) (6) (9) (11) Data source: 28.1.72 - 11. 3.72 Ellis unpublished. 28.4.72 - 7.12.72 Kanamori, 1976. TABLE A2.lib SALINITY (°/oo) AND TEMPERATURE (QQ OF ILLAWARRA LAKE SURFACE WATERS. (Site locations shown on Fig. A2.1) Site 2 4 5 6 8 10 s^tem Sal. Temp. Sal. Temp. Sal. Temp. Sal. Temp. Sal. Temp. Sal. Temp. Date\J 6 1.73 30.73 21.9 29.96 23.0 29.56 23.4 l 29.75 23.3 1 30.83 22.5 l 30.32 23.3 6 2.73 32.62 27.8 31.64 29.9 30.56 29.5 30.90 28.3 30.94 27.4 31.02 27.8 6 3.73 25.07 23.4 21.60 23.6 23.87 24.7 24.06 23.4 21.62 22.8 24.58 23.4 5 4.73 25.25 21.1 24.81 21.3 24.96 22.1 24.07 21.7 23.99 21.4 24.98 21.3 8 5.73 25.59 18.1 25.42 18.2 26.01 19.0 25.42 18.2 24. 78 17.4 26.10 17.8 7 6.73 27.58 12.5 27.66 12.4 27.66 14.0 27.53 12.9 27.37 10.0 27.87 12.4 11 7.73 26.60 13.9 25.92 14.1 26.40 14.7 8.06 14.2 25.00 13.3 25.65 13.7 5 8.73 27.12 13.9 26.69 14.0 27.14 13.9 26.93 14.3 26.40 12.9 27.07 13.4 25 9.73 28.61 18.8 15.07 21.6 28.10 19.4 23.61 19.6 28.75 18.8 28.68 18.1 23 10.73 27.68 20.7 27.29 21.5 27.49 21.4 27.36 21.4 27.05 19.5 27.73 20.3 22 11.73 27.77 21.0 27.16 21.8 27.43 23.7 27.45 21.3 27.57 20.6 27.81 21.6 20 12.73 24.71 22.8 22.95 23.7 24.15 23.6 24.06 23.5 24.30 23.0 24.62 22.7 Data Source: Kanamori, 1976. (Cont.) 224 TABLE A2.11c TOTAL PHOSPHORUS - ILLAWARRA LAKE WATERS AND INFLOW STREAMS - 1972 TO 1974 Site Total Phosphorus Illawarra Lake 4 - 145 yxg/1 ★ 10 114 pg/1 Mean Lake 46 pg/1 Macquarie Rivulet 12 45.7 pg/1 Mullet Creek 13.7 30.6 pg/1 Brooks Creek 54.2 - 150 pg/1 Madigan Creek 389 - 3440 ug/1 Trumper Creek 3550 - 3610 ng/l Seawater 15.5 pg/1 Data source: Kanamori, 1976. ♦State Pollution Control Commission - unpublished. TABLE A2■12a WATER QUALITY - ILLAWARRA LAKE. SUMMARY OF 11 SAMPLINGS 23.5.73 TO 22.9.75. (Site locations shown on Fig. 1.2) Site Quantity Temp. Sal. pH B.O.D. D.O. E. coli Chlorophyll "a" °C °/oo mg/1 % Sat. /100 ml jJg/i Boonerah Max. 23.0 30.3 8.6 6.0 120 25 30 Point Min. 10.5 9.5 7.8 1.4 72 0 25.5 Wollingurry Max. 23.0 30.0 8.4 16.0 118 25 33.0 Point Min. 10.2 9.8 7.8 1.0 62 0 Currung-Goba Max. 20.8 30.3 8.3 3.0 119 25 37.1 Point Min. 10.4 9.8 7.7 2.6 78 10 . Koonawarra Max. 22.1 30.6 8.4 2.6 107 25 28.1 Bay Min. 10.2 9.8 7.4 1.0 61 0 Cudgeree Max. 20.5 30.7 8.9 5.0 121 30 256.5 Hole Min. 10.6 14.3 7.5 0.8 62 0 3.29 Data Source: State Pollution Control Commission, unpublished. (Cont.) 225 TABLE A2■ 12b WATER QUALITY - ILLAWARRA LAKE INFLOW STREAMS. (Site locations shown on Fig. 1.2) 11/8/75 6 mm rain in previous 3 days 22 mm rain in previous 30 days. Oakey Horsley Macquarie Duck Dapto Robbins Item Creek Creek Rivulet Creek Creek Creek BOD mg/1 52 14 4.8 3.6 2.6 4.4 S.S. mg/1 110 118.8 4.4 2.4 4.0 6.8 NH3-N mg/1 19 31.5 3.6 1.3 0.9 1.4 NO3-N mg/1 0.49 0.69 0.29 0.2 0.22 0.5 T-P mg/1 1.74 2.06 0.08 0.3 0.05 0.06 E. coli/lOOml 11,400 5,000 80 nil 940 nil Coliforms/lOOml T.N.T.C. 100,000 990 80 7,600 1,200 Chlorophyll 'a' H9/1 29.88 2.4 2.19 44.36 2.98 5.86 22/9/75 0 mm rain in previous 6 days Mullet 20 mm rain in previous 40 days Creek BOD mg/1 84 16 5.2 3.6 7.4 8.2 S.S. mg/1 108 84 12.8 4.2 8.2 10.4 NH3-N mg/1 21 28.8 5.7 2.6 3.1 2.6 NO3-N mg/1 0.62 0.56 0.05 0.22 0.22 0.44 T-P mg/1 2.04 1.86 0.05 0.28 0.16 0.12 E. coli/lOOml 6,000 1,300 130 30 20 nil Coliforms/lOOml 30,000 40,000 2,500 700 960 BOD = Biochemical Oxygen Demand S.S = Suspended solids T-p = Total phosphorus. Data source: State Pollution Control Commission, unpublished. TABLE A2.13 LAKE WATER LEVELS Year Minimum cm. Maximum cm. Range cm. Rainfall mm. 1966 91.4 147.3 55.9 861.8* 1967 86.4 149.9 63.5 838.5 1968 76.2 149.9 73.7 529.2 1969 record incomplete 1278.1 1970 99.1 149.9 50.8 786.9 X 61.0 * No record of August rainfall - yearly rainfall estimated by addition of 70 year mean to 1953 (61.8mm) as recorded at Wollongong East Post Office. During August, lake level fell indicating the absence of heavy rain. The estimate therefore is reasonable. Data source: N.S.W. Electricity Commission (1971). 226 TABLE A2.14 SALINITY CHANGES - FALLS EXCEEDING 10 PARTS PER THOUSAND IN 14 DAYS. Salinity Range Salinity Fall Rainfall Date °/oo (approx.) °/oo (approx.) mm February 1958 39 to 27 12 303.8 March 1959 34 to 18 16 367.8 October 1959 26 to 11 15 158.8 December 1960 33 to 22 11 149.1 November 1961 24 to 5 19 618.5 December 1963 28 to 16 12 191.5 Continuous data unavailable for other years. Data source: N.S.W. Electricity Commission (1971). TABLE A2.15 SALINITY VARIATION - NUMBER OF MONTHS LAKE SALINITY WAS WITHIN THE RANGES LISTED o V & d o k o o' o o 0 Year >30 °/oo ^0 <10 °/oo 1957 12.0 1958 3.5 8.5 1959 2.25 5.0 4.5 0.25 1960 4.0 8.0 1961 10.5 0.5 1.0 1962 1.0 9.0 2.0 1963 8.75 3.25 % Time 27.1 59.2 12.2 1.5 Data source: N.S. W. Electricity Commission (1971) TABLE A2.16 LAKE WATER TEMPERATURE - MAXIMA AND MINIMA. °C °C Year Max. Month Min. Month 1950 25.5 December 11.7 July 1951 26.7 March 8.9 July 1952 26.7 January 9.4 July 1954 26.7 February 9.4 August 1966 28.9 January 11.7 July 1967 26.7 January/February 11.7 July 1968 29.4 February 9.4 July 1969 29.4 January 11.7 June 1970 29.4 February 11.1 July Data source:: N.S.W. Electricity Commission (1971) 227 TABLE A2.17 TEMPERATURE VARIATION - NUMBER OF MONTHS LAKE TEMPERATURE WAS WITHIN THE RANGES LISTED. Year >26°C <26>20°C <20>15°C <15>10°C <10°C 1950 4.5 3.5 4.0 1951 4.5 4.5 2.75 0.25 1966 0.25 6.0 3.25 2.5 1967 5.0 4.0 3.0 % Time 41.6 31.7 25.5 0.5 Continuous date unavailable for other years. Data source: N.S.W. Electricity Commission (1971) TABLE A2 ,.18 SURFACE SALINITY - ILLAWARRA LAKE 1975 - 1976 (Site locations shown on Fig . 2.1. ) Bevans 2WL Griffins Tallawarra Island Transmitter Bay Power Date Dredge (F) Dredge Station 4. 6.75 31.1 32.9 28.5 30.3 29. 6.75 24.1 14.4 12.4 12.2 20. 7.75 23.4 20.6 19.2 20.7 26. 7.75 24.1 22.5 21.9 20.9 31. 8.75 32.5 32.1 31.2 31.4 20. 9.75 32.5 32.2 31.3 31.5 18.10.75 32.2 31.0 28.6 29.9 25.11.75 32.7 31.9 30.3 30.2 10.12.75 33.8 32.5 32.2 31.6 4. 1.76 32.5 32.2 32.1 31.4 17. 1.76 30.3 29.4 29.5 28.6 29. 1.76 24.6 23.9 23.6 22.3 8. 2.76 27.0 26.4 26.4 25.2 14. 2.76 24.0 22.2 22.6 21.3 TABLE A2.19 SALINITY VARIATIONS (°/oo) CAUSED BY FLOODING IN ILLAWARRA LAKE ( Site locations as for benthic macrofauna survey Fig. 2.1. ) Date Tide Entrance Back Bevans Griffins Rainfall Days Channel Channel Island Bay Previous Since 30 Days Rain 4.6.75 In 35.0 35.0 31.5 28.5 0mm 34 Out 32.5 31.5 30.0 28.5 29.6.75 In 34.2 34.0 24.1 12.4 252mm 1 Out 27.4 25.0 20.2 12.4 26.7.75 In 34.6 34.2 27.3 21.9 238mm 20 Out 30.9 28.3 26.8 21.9 Salinity Variations 7.5 10 12 15 228 TABLE A2.20 WATER QUALITY - BENTHIC FLORA BIOMASS SURVEY - NOVEMBER 1975 ( Site locations shown on Fig . 2.1.) Total Temperature Water Salinity Turbidity Phosphorus °C Eh Site Depth cm °/oo N.T.U. ug P/1 at 10 cm pH mV A 50 32.7 0.4 66.9 22.0 8.2 +340 B 85 32.0 0.8 73.6 22.0 8.1 +340 C 90 32.0 0.5 38.9 21.5 8.1 + 330 D 60 32.0 0.8 26.8 22.0 8.2 + 340 E 75 32.0 1.5 32.0 22.0 8.2 +340 F 60 32.0 1.5 33.9 21.5 8.1 +330 G 70 31.7 3.5 58.8 22.5 8.4 +350 H 110 31.3 5.0 24.1 22.5 8.0 + 330 I 60 31.3 12.0 21.9 22.5 8.0 + 320 J 80 30.6 3.5 52.0 23.0 8.1 +310 K 125 32.0 1.5 35.6 22.0 8.2 +340 L 100 32.0 1.5 35.6 22.0 8.2 +340 M 95 32.0 1.5 35.6 22.0 8.2 + 340 TABLE A2.21 WATER QUALITY - ZOSTERA BIOMASS SURVEY - BEVANS ISLAND ( Site location shown on Ficj. 2.1.) Total Temperature Water Salinity Turbidity Phosphorus °C Eh Site Depth cm °/oo N.T.U. ug P/1 at 10cm pH mV Transect 1 1.1 40 32.6 3.5 27.7 22.5 8.4 +340 1.2 40 32.9 3.5 44.3 22.5 8.3 +340 1.3 50 32.2 1.75 50.8 22.0 8.4 +340 1.4 60 32.6 1.75 48.6 22.0 8.2 +345 1.5 70 32.9 1.75 46.4 22.0 8.3 +350 1.6 80 31.9 3.5 39.0 22.0 8.3 +340 1.7 120 32.9 3.25 55.7 22.0 8.2 +330 Transect 2 2.1 65 32.2 1.75 49.7 22.0 8.4 +340 2.2 70 32.5 1.75 49.0 22.0 8.2 +340 2.3 90 32.7 1.75 47.5 22.0 8.3 +350 2.4 90 32.8 2.75 45.7 22.0 8.2 +345 2.5 110 32.6 3.5 47.5 22.0 8.2 +340 2.6 80 32.2 1.5 46.5 22.0 8.4 +330 2.7 105 32.2 3.5 48.1 22.0 8.4 +340 2.8 110 31.9 4.0 60.3 22.0 8.3 +340 229 TABLE A2.22 WATER QUALITY - ZOSTERA BIOMASS SURVEY - GRIFFINS BAY ( Site location shown on Fig . 2.1. ) Total Temperature Water Salinity Turbidity Phosphorus °C Eh mV Site Depth cm °/oo N.T.U. Mg p/1 at 10cm PH Transect 3 3.1 40 29.5 2.0 39.4 22.5 8.0 +320 3.2 50 29.5 1.0 49.9 22.0 8.1 +330 3.3 60 29.5 1.25 24.0 21.5 8.1 +325 3.4 70 29.5 1.0 27.6 21.5 8.1 +320 3.5 80 29.5 1.5 29.5 21.5 8.2 +320 3.6 90 29.5 1.5 16.5 21.0 8.1 +310 Transect 4 4.1 55 29.5 1.0 24.6 21.5 8.2 +320 4.2 65 29.5 1.0 25.4 21.5 8.2 +310 4.3 75 29.5 0.75 25.7 21.5 8.2 + 320 4.4 85 29.5 1.5 26.3 21.5 8.1 +320 TABLE A2.23 VARIATION IN SURFACE WATER TEMPERATURE ACROSS A ZOSTERA BED - KOONAWARRA BAY, 24-10-1972 • Distance (m) Temperature °C Water Depth cm. Zostera Growth 0 21.5 60 Submerged 5 22.0 55 Submerged 10 22.5 52 Submerged 15 22.5 48 Submerged 20 23.0 45 Emergent 25 24.0 38 Emergent 30 23.0 42 Bare area 35 24.0 37 Emergent 40 24.5 35 Emergent 45 25.0 35 Emergent TABLE A2.24 TEMPERATURE CHANGES WITH DEPTH IN AN EMERGENT ZOSTERA BED - KOONAWARRA BAY, 8-11-1972. Water Depth cm. Water Temperature °C Surface 1 27.0 5 25.6 10 22.5 15 21.1 20 21.0 230 TABLE A2.25 SECCHI DISC EXTINCTION DEPTHS (m) ZOSTERA BEDS. Where the water depth was insufficient to allow for disc extinction when resting upon the bottom, subjective estimates' (V+, V, V-) based upon the visibility of distinctive markings on the Secchi disc have been presented: V+ = small distinctive markings visible, V = only larger distinctive markings visible, V- = Secchi disc visible but distinctive markings not visible. (Site locations shown on Fig. 2.1.). Site 1 2 3 4 5 6 7 8 9 Water Date Depth 0.9 1.0 1.1 0.6 0.6 0.6 0.8 0.6 1.0 12. 1.72 ______2. 2.72 4. 7.72 V! v+ v+ V+ v+ v+ V+ V+ V+ 15. 8.72 V+ v+ v+ V V V V+ V+ V 19. 9.72 V+ v+ V V v+ v+ V+ V+ V 3.10.72 V+ v+ V V V v+ V+ V+ V- 24.10.72 V+ v+ v+ v+ v+ v+ V+ V+ V- 8.11.72 V V V 0.5 V V V V 0.4 12.12.72 V- 0.6 0.4 0.3 V V V V 0.2 3. 1.73 V- V+ 0.3 V 0.4 v+ V V 0.2 TABLE A2.26 SECCHI DISC EXTINCTION DEPTH (m) IN BODY OF LAKE - 1972 AND 1975. (Site locations shown on Fig. 2.1) Site Date SI S2 S3 S4 S5 12. 1.72 2.1 2.0 2.0 _ - 2. 2.72 1.2 1.0 1.0 - - 4. 7.72 2.4 2.2 2.3 - - 15. 8.72 2.3 2.2 2.2 - - 19. 9.72 2.2 2.0 2.2 - - 3.10.72 2.6 2.0 2.1 - - 24.10.72 2.0 2.0 2.2 - - 8.11.72 1.4 1.6 1.6 - - 12.12.72 1.2 1.0 1.1 - - 3. 1.73 1.2 1.3 1.2 - - Mean 1.9 1.7 1.8 4. 6.75 2.0 1.6 1.8 1.2 1.3 13. 7.75 1.6 1.4 1.5 1.0 0.9 30. 8.75 2.0 1.5 1.6 1.5 1.0 18.10.75 2.1 1.5 1.6 1.4 0.9 20.11.75 1.4 1.2 1.4 1.3 0.9 8. 1.76 2.0 1.4 1.6 1.3 1.2 17. 1.76 1.6 1. 7 1.3 1.,4 1.4 1..4 1.2 1.3 0.95 1.1 29. 1.76 1.4 1.5 1.2 1.5 1.25 8. 2.76 1.2 1.0 1.2 1.25 0.95 1.,0 0.,9 1..0 1.1 0.9 14. 2.76 0.9 0.85 0.85 0.95 0.8 Mean 1.7 1.4 1.5 1.3 1.0 Note During both the 1972 and 1975 surveys, the depth of Secchi disc extinction in Zostera beds on the western side of the lake was commonly less than 0.6m and at times less than o.2m. 231 TABLE A2.27 TURBIDITY (N.T.U.) AT SECCHI DISC SITES AND INSHORE OVER ZOSTERA BEDS. (Site locations shown on Fig. 2.1.) Date ^NJ1 SI Inshore 11 S2 Inshore 1| S3 Inshore | S4 Inshore j S5 Inshore on n 76 '' l.n rv o n ivs ' 'is A S 1 76 ‘Vn ' 4.S TABLE A2.28 CORRELATION COEFFICIENT MATRICES BEVANS ISLAND TRANSECTS Biomass Total O.C. T-P pH Eh Zostera Biomass fines 0.75 0.81 -0.40 -0.43 0.46 0.46 O.C 0.85 0.01 -0.43 0.47 T-P -0.24 -0.46 0.43 0.44 PH -0.16 Eh -0.08 -0.13 GRIFFINS BAY TRANSECTS Biomass Total O.C. T-P PH Eh Zostera Biomass fines 0.52 0.60 -0.38 -0.30 -0.34 -0.40 O.C. 0.50 -0.25 -0.51 -0.17 T-P -0.29 -0.11 -0.14 -0.18 pH -0.35 Eh 0.01 0.10 EASTERN SEAGRASS BEDS - NOVEMBER Biomass Total O.C. T-P pH Eh Zostera Biomass fines 0.81 0.77 -0.57 -0.58 0.07 0.08 O.C. 0.88 -0.62 -0.60 0.11 T-P -0.56 -0.50 -0.03 -0.02 pH 0.69 Eh -0.05 -0.49 EASTERN SEAGRASS BEDS - ALL SAMPLES O.C. T-P PH Eh fines 0.62 0.65 -0.45 -0.59 O.C. 0.83 -0.27 -0.62 T-P -0.35 -0.53 PH 0.24 Other values Lake sediment survey fines v O.C. 0.93 All sediment samples fines v O.C. 0.87 Bevans Island T-P(sed) v T-P(water) -0.24 Griffins Bay T-P(sed) v T-P(water) -0.44 Eastern bed survey T-P(secL) v T-P (water) -0.19 All values T-P(sed.) v T-P (water) -0.35 232 TABLE A2.29 TOTAL PHOSPHORUS CONTENT OF LAKE SEDIMENTS Total Phosphorus Lake (mg/kg dry wt.) Reference Shagawa Lake, Minnesota 1231 (± 238) Hart et.al. Lake Erie, U.S.A./Canada 713 - 1238 1976 Upper Klamath Lake, Oregon 629 - 1033 Agency Lake, Oregon 426 - 725 Diamond Lake, Oregon 460 - 994 16 Wisconsin Lakes 730 - 7000 (mean 2550) Lake Kinneret, Israel 1000 - 4500 Lake Mulwala 350 - 1188 Tuggerah Lakes. sand sediments 50 Higginson loamy sand sediments 90 1971 clay sediments 290 Illawarra Lake. sand sediments 39 - 120 This study (mean 80) clay sediments 520 - 675 (mean 600) TABLE A2.30 SEVENTY YEAR AVERAGE OF MONTHLY RAINFALL (mm) RECORDED AT WOLLONGONG EAST POST OFFICE January February March April May June 106.2 109.8 118.0 128.2 112.2 98.0 July August September October November December 92.0 61.8 68.0 68.2 68.8 87.2 TABLE A2.31 INCIDENCE OF HIGH MONTHLY RAINFALL, (mm) TALLAWARRA POWER STATION - 1958 to 1970 ^\Rainf all MontlT\ | 150 - 199 | 200 - 249 | 250 + January 1 2 1 1 February 2 1 (304) March 1 3 1 (368) April 3 May 1 June 2 1 (314) July . August 1 September 1 October 2 November 1 1 1 (618) December 5 233 A3 o ^ a ^ 3 * csa cn to CO > ro ^ w d cn H CD o G N 0 £ *0 3 M w d cn U1 g H (D W H tr< h* CD M • h< H- to S- % ~ 0> 2 tsj £ A cn M X X X X X LTI 3 M CD O trt o (T> H* H H- S-S nJ rtBi sr(D r+ M 5 W cn s (U W NJ f IS n> M 0) 03 X (0 3 •s w JT A CD O (D M O M + rt * NH3HMC N cn c5 CD H W H M to H- \ 0» € X 01 rt\ (0 3 (D * A W M H» CD X X O 0) H* U> M * H* -f \ * fDe !p> 0) cn W H* hh CD O CD M U> M * H- + \ ii (D H* M v cn hh H ID H H fl) H \ W O' £ H- ^ X 0 cn c 2 0) a tr1 p* O 0) P1 X *\) H X P- H* — h-* (D 3 cn o 03 0) 234 TABLE A3.2 BIRDS OF ILLAWARRA LAKE. KEY Bird distribution and abundance. C = common = seen throughout the year on most outings. U = uncommon = seen seasonally or spasmodically and may at times be abundant. A1 = abundant = in flocks exceeding 50 birds. A = abundant = in flocks exceeding 20 birds. M = moderate = fewer than 20 birds in flocks but more than a pair. F = few = singly or in pairs. KEY Bird feeding. L = feeding over the whole lake including deep water areas. Z = feeding in seagrass bed zone including on or around floating algal masses. W = waders feeding in water <20cm deep. S = feeding amongst decomposing Zostera or algae along the strand line. (Locality shown on Fig. 1.2) Locality Burry Taxa Bay Bay Bay Bay Island Feeding Koong Haywoods Migratory Channel Koonawarra Peninsular Back Bevans Griffins Windang Order Pelecaniformes Australian Pelican Pelicanus conspicillatus CM CM CF CM CF CF UF Z Darter Anhinga rufa CF CM CF CM CF CF UF Z Black Cormorant Phalacrocorax carbo CM CM CM CM CM CM CF L,Z Little Black Cormorant Phalacrocorax sulcirostris CM UM UM CM CM UF UF Z Little Pied Cormorant Phalacrocorax melanoleucos CM CM CM CM CM CM CM L,Z Order Podicipitiformes Little Grebe Podiceps novaehollandiae CF CF CF 7 Order Ciconiiformes White-Faced Heron Ardea novaehollandiae CF CF CF CF CF CF CF W,S White Egret Egretta alba CF CF CF CF CF CF CF W,S Little Egret Egretta garzetta CF CF CF CF CF CF CF W,S White Ibis Threskiornis molucca UM UM UM UM UM W,S Straw Necked Ibis Threskiornis spinicollis UM UM UM UM UM UM UM W,S Royal Spoonbill Platalea regia CM CM CM CM CM CF CM W,S Yellow-Billed Spoonbill Platalea flavipes UF UF UF UF UM UF W,S Order Anseriformes Black Swan Cygnus olor CM CA1 CA1 CM Z Black Duck Anas superciliosa CA1 CA1 CM CM CA1 CA1 CA1 Z,S Chestnut Teal Anas castanea UA UA UA Z,S Grey Teal Anas gibberifrons CA z,s Order Falconiformes Black-Shouldered Kite Elanus notatus CF CF White-breasted Sea Eagle Haliaeetus leucogaster UF CF CF L, Z Swamp Harrier Circus approximans CF CF L Order Gruiformes Dusky Moorhen Gallinula tenebrosa CM CM CM CM CM Z,S Swamphen Porphyrio porphyrio CF CF CF CF Z,S Coot Fulica atra CF CF CF CF CF z,s Order Charadriiformes Pied Oystercatcher Haematopus ostralegus CF CF CF w,s Spur-Winged Plover Vanellus novaehollandiae CF CF s Red-capped Dotterel Charadrius alexandrinus UM UM UM UM UM UM w,s Double-banded Dotterel Charadrius bicinctus UM UM UM w,s Whimbrel Numenius phaeopus UF UF UF X w,s Eastern Curlew Numenius madagascariensis UF UF UF X w,s Greenshank Tringa nebularia UF UF UF X w,s Grey-tailed Tattler Tringa brevipes UM UM UM UM X w,s Black-tailed Godwit Limosa limosa UM UM X w,s Bar-tailed Godwit Limosa lapponica UM UM UM UM UM UM X w,s Banded Stilt Cladorhynchus leucocephalus UF w,s Silver Gull Larus novaehollandiae CA1 CA1 CA1 CA CA CM CM s Little Tern Sterna albifrons CM CM CM CM CM s Nomenclature according to Slater, 1974. BENTHIC MACROFAUNA 1LLAWARKA LAKE,JUNE 1975 TABLE A3.3 ' -~_^SITE & SAMPLE ENTRANCE CHANNEL SITE 1 BACK CHANNEL SITE 2 WEST BEVANS ISLAND SITE 3 GRIFFINS BAY SITE 4 TAXA 123456789 10 E 1 2 3 4 5 6 E 12 3 4 5 6 E jl 2 34 56789 10 E Phylum Mollusca 554 626 1027 4? Class Pelecypoda 165 219 33_ Lasaea australis 39 50 25 60 204 18 4 22 Laternula creccina 1 1 Macoma deltoidalis 17 25 7 17 18 10 15 15 15 10 149 1 3 4 Xenostrobus securis 12 3 13 11 5 2 2 12 5 2 Mysella sp. 10 1 3 Soletellina donaciodes 5 Class Gastropoda 389 407 1011 Bembicium nanum 1 Diala sp. 1 1 10 100 70 40 45 50 315 230 120 200 250 150 950 8 Eurytrochus strangei 1 2 2 4 3 1 23 Nassarius sp. 20 14 10 25 35 13 221 12 22 18 15 12 11 90 20 10 6 14 4 7 61 1 1 Pseudoliotia micans 3 1 4 21 Pyrazus ebeninus 4 3 17 21 13 113 1 1 2 2 2 2 9 Phylum Arthropoda 199 134 100 22 Class Crustacea 199 134 100 22 Order Decapoda 165 13 35 3 Alpheus sp. 1 2 1 4 Eriocheir sp. 1 2 Euchiorgrapsus sp. 1 1 Halicarcinus australis 1 Halicarcinus ovatus 1 1 Macrobrachium intermedius 21 19 9 4 13 10 26 17 154 11 6 2 34 Paragrapsus gaimardii______1 1 2 2 1 1 Order Amphipoda 120 Melita sp. 1 4 15 1 3 Paracorophium sp. 6 3 9 14 38 Parhalimedon sp. Siphonocetes sp. 2 1 3 1 1 Tethygenia sp. 1 2 1 4 f. Eursirida 2 2 4 1 9 1 1 1 21 8 28 13 32 3 12 96 3 3 4 3 9 22 6 2 1 2 1 12 Order Isopada 4 1 1 Chitonopsis sp. 3 1 4 1 1 1 1 Phylum Anneleida 63 409 45 194 Polychaeta 63 409 45 194 Australonereis chlersi 1 1 5 Nephyts australiensis 5 12 49 1 2 3 5 1 12 4 12 8 15 Nereis diversicolor 3 45 86 69 38 62 95 395 1 15 40 17 27 10 11 14 12 10 10 37 13 161 Phyllodoce sp. 3 Barantolla sp. 1 Capitella sp. 4 Desdemona sp. Haploscoloplos sp. 10 14 Notomastus sp. Phylum Nemertinea 63 13 25 2 Nemertean sp. 5 5 11 9 6 2 7 9 9 63 5 4 4 13 1 5 1 5 8 5 25 1 1 2 TOTAL ORGANISMS 879 1182 1197 260 No. Species 30 18 16 14 BENTHIC MACROFAUN* - ILLAWARRA LAKE,JUNE 1975. TABLE A3.4 . .ENTRANCE CHANNEL SITE 1 , _ BACK CHANNEL SITE 2 1 BEVANS ISLAND SITE 3 GRIFFINS BAY SITE 4 o No. iu2 % Mass g/m % 1 No. /m2 % Mass g/m2 % No. /m2 % Mass g/ra2 % No. /m2 % Mass g/m2 % Phylum Mollusca 1770 63 1415 94 1 3275 52.5 110 62 5450 87 48 58 135 16 4 - 21 Class Pelecypoda 525 19 775 51 1115 17.5 48 27 85 1.4 6 7 105 12.5 3 16 Lasaea australis 1080 4.9 5 0.1 70 0.3 Laternula creccina 5 23.5 Macoma deltoidalis 475 708.0 20 37.8 Xenostrobus securis 15 5.0 65 5.4 35 3.0 Mysella sp. 30 0.7 15 0.4 Soletellina donaciodes 15 44.0 Class Gastropoda 1245 44 640 42 2160 35 62 35 5365 86 42 51 30 3.5 0.6 5 Bembicium nanum 5 0.4 5 0.6 Diala sp. 5 <0.1 1670 5.6 5040 16.9 25 0.1 Eurytrochus strangei 75 72.3 Nassarius sp. 700 107.2 480 36.3 325 24.6 5 0.5 Pseudoliotia micans 70 0.3 Pyrazus ebeninus 360 360.3 5 19.4 Velacumantus australis 30 98.1 Phylum Arthropoda 645 23 70 4 5 715 11.5 27 15 525 8.5 28 34 75 9 2 10.5 Class Crustacea Order Decapoda 530 19 65 4 70 1 12 6. 5 185 3.0 24 30 10 1 1.1 5 Alpheus sp. 15 2.8 Eriocheir sp. 5 0.2 Euchirograpsus sp. 5 0.9 Halicarcinus australis 5 1.6 Halicarcinus ovatus 5 0.1 Macrobrachium intermedius 490 57.7 60 6.9 180 21.2 10 1.1 Paragrapsus gaimardii 5 2.9 10 4.8 5 2.4 Order Amphipoda 100 3.5 2 0.1 640 10 15 8.5 335 5.4 4 4 65 8 1.2 5 Melita sp. 20 0.1 80 0.2 15 0.1 5 <0.1 Paracorophium sp. 50 0.1 200 0.3 Parhalimedon sp. 5 <0.1 Siphonocetes sp. 10 <0.1 5 <0.1 Tethygenia sp. 15 <0.1 f. Eusiridae 70 1.9 510 14.8 115 3.4 40 1.1 Order Ispoada 15 0.5 0.1 <0.1 5 <0.1 <0.1 <0.1 5 <0.1 <0.1 <0.1 Chitonopsjs sp. 15 0.1 5 <0.1 5 <0.1 Phylum Anneleida 205 7 23 1.5 2175 35 40 23 235 40 7 8 620 75.0 13 68 Polychaeta 205 23 1.5 2175 35 40 23 235 40 7 620 13 68 Australonereis chlersi 15 9.5 Nephtys australiensis 155 13.0 65 5.3 50 4.0 Nereis diversicolor 10 0.2 2100 34.6 210 3.5 510 8.5 Phyllodoce sp. 10 <0.1 Barantolla sp. 5 <0.1 Capitella sp. 10 3.5 15 <0.1 Desdemona sp. 5 <0.1 Haploscoloplos sp. 45 0.1 Notomastus sp. 5 <0.1 Prionospio sp. 5 <0.1 5 <0.1 15 0.1 Phylum Nemertinea 200 7 0.6 <0.1 70 1 0.2 <0.1 30 0.5 0.1 <0.1 5 <0.4 <0.1 0.1 Nemertean sp. 200 0.6 70 0.2 30 0.1 5 <0.1 TOTAL ORGANISMS 2800 100 1500 100 6200 100 175 100 6250 100 83 100 825 100 19 100 No. Species 30 18 16 14 237 TABLE A3.5 BENTHIC FLORA BIOMASS - DRY WEIGHT (g) - NOVEMBER 1975. (Site locations shown on Fig. 2.1) BEVANS ISLAND Zostera Zostera Other Organic Sample Shoots Rhizomes Ruppia Gracilaria Algae Matter Total A 1 2.27 4.42 0.38 0.39 5.85 13.31 2 0.65 1.94 0.06 4.09 6.74 3 0.56 0.63 1.36 0.19 4.98 7.72 4 1.56 3.13 0.02 4.52 9.23 5 0.39 1.06 0.05 0.11 6.52 8.13 Z 5.43 11.18 1.36 0.45 0.75 25.96 45.13 X 1.09 2.24 0.27 0.09 0.15 5.19 9.03 B 1 11.67 13.38 0.37 2.90 28.32 2 11.28 10.60 0.10 4.22 26.20 3 11.33 10.97 0.08 5.27 27.65 4 9.64 11.00 0.21 0.01 3.32 24.18 5 9.78 15.52 0.31 3.74 29.35 Z 53.70 61.47 1.07 0.01 19.45 135.70 X 10.74 12.29 0.21 3.89 27.14 C 1 7.92 8.16 4.23 20.31 2 7.31 7.43 0.01 4.45 19.20 3 5.36 7.69 4.91 17.96 4 6.47 6.30 4.50 17.27 5 7.33 6.51 0.02 4.10 17.96 Z 34.39 36.09 0.03 22.19 92.70 X 6.88 7.22 0.01 4.44 18.54 OPPOSITE 2WL RADIO TRANSMITTER Zostera Zostera Other Organic Sample Shoots Rhizomes Ruppia Gracilaria Algae Matter Total D 1 3.06 6.11 0.02 6.08 15.27 2 1.44 1.76 0.32 0.20 9.87 13.59 3 2.02 3.49 5.00 8.21 18.72 4 1.16 5.04 0.47 6.16 12.83 5 1.46 3.70 0.41 0.10 2.57 8.24 Z 9.14 20.10 5.73 0.79 32.89 68.65 X 1.83 4.02 1.15 0.16 6.58 13.73 E 1 3.77 8.98 0.09 0.82 7.37 21.03 2 6.78 9.72 0.25 0.08 4.05 20.88 3 6.63 3.94 4.46 15.03 4 2.98 7.21 0.01 5.48 15.68 5 3.77 10.11 0.05 7.29 21.22 Z 23.93 39.96 0.09 1.13 0.08 28.65 93.84 X 4.79 7.99 0.02 0.23 0.02 5.73 18.77 F 1 5.63 6.91 0.99 4.28 17.81 2 11.87 10.62 0.12 12.93 35.54 3 4.71 12.10 2.41 19.22 4 10.08 14.09 4.50 28.67 5 7.80 14.82 0.19 5.31 28.12 Z 40.09 58.54 1.30 29.43 129.36 X 8.02 11.71 0.26 5.89 25.87 238 TABLE A3.5 (Cont.) OFF NICOLE RD., PRIMBEE Zostera Zostera Other Organic Sample Shoots Rhizomes Ruppia Gracilaria Algae Matter Total G 1 15.47 4.36 19.83 2 16.50 11.83 28. 33 3 23.04 23.04 4 22.70 0.98 23.68 5 48.53 18.01 66.54 E 126.24 35.18 161.42 X 25.25 7.04 32.28 H 1 1.82 5.20 3.53 10.55 2 4.12 6.62 0.50 13.48 24.72 3 2.42 10.31 0.05 4.59 17.37 4 0.78 5.42 3.49 9.69 5 0.88 8.23 0.04 0.03 5.97 15.15 Z 10.02 35.78 0.59 0.03 31.06 77.48 X 2.00 7.16 0.12 0.01 6.21 15.50 GRIFFINS BAY Zostera Zostera Other Organic Sample Shoots Rhizomes Ruppia Gracilaria Algae Matter Total I 1 3.49 5.46 0.67 5.46 0.63 15.71 2 2.08 6.00 3.32 0.31 0.03 11.74 3 1.85 1.43 5.74 13.71 0.45 23.18 4 17.65 12.61 0.35 0.37 30.98 5 0.39 1.02 18.71 2.71 1.87 24.70 T, 25.46 26.52 28.44 22.54 3.35 106.31 X 5.09 5.30 5.69 4.51 0.67 21.26 J 1 2.81 11.03 0.14 1.82 15.80 2 3.72 15.39 2.22 2.03 23.36 3 2.00 4.80 0.29 3.69 10.78 4 3.65 8.00 0.21 0.52 12.38 5 1.18 5.22 0.79 4.78 11.97 £ 13.36 44.44 3.65 12.84 74.29 X 2.67 8.89 0.73 2.57 14.86 239 A4 TABLE A4.1 , ZOSTERA BIOMASS SURVEY - DRY WEIGHT (g) - JANUARY 1976. (Site locations shown on Fig. 2.1 and Fig. 4.3) BEVANS ISLAND TRANSECTS 1 AND 2 Water Shoot Water Shoot Depth Organic Length Depth Organic Length Site cm Zostera Ruppia Algae Matter cm Site cm Zostera Ruppia Algae Matter cm 1.1 40 1.74 6.13 5 1.2 40 4.26 1.19 3.21 5 1.71 4.0 to 4.14 0.2 2.40 to 0.54 6.05 10 6.07 2.0 3.45 20 3.23 0.45 X 5.48 4.21 X 0.8 3.12 4.15 <10 3.78 0.45 3.81 10 £ 8.02 3.12 20.78 23.73 3.64 0.2 17.08 1.3 50 19.95 4.40 35 1.4 60 23.64 3.67 40 20.12 6.04 to 27.03 3.30 to 22.83 3.86 50 24.60 3.82 75 20.38 4.51 X 17.06 4.00 X 20.05 2.07 40 21.96 3.57 65 £ 103.33 20.88 114.29 18.36 1.5 70 60.4 6.27 50 1.6 80 25.33 6.01 40 44.64 2.43 to 25.91 5.72 to 52.65 5.61 85 22.98 4.69 70 41.16 4.91 X 19.32 5.34 X 35.73 3.87 65 32.84 4.21 60 £ 234.58 23.09 126.38 25.97 1.7 120 3.08 1.02 10 2.1 65 18.38 3.33 40 4.24 6.23 to 10.30 6.10 to 4.29 3.82 20 20.42 2.76 55 5.62 3.96 X 14.67 3.76 X 2.49 3.81 15 12.15 6.19 50 £ 19.72 18.84 75.92 22.14 2.2 70 35.64 3.27 40 2.3 90 18.46 3.27 50 28.28 2.18 to 24.62 4.01 to 27.66 5.30 65 19.78 3.02 75 34.37 4.16 X 26.51 4.21 X 36.10 3.02 55 22.88 3.64 65 £ 162.05 17.93 112.25 18.15 2.4 90 8.55 3.03 50 2.5 110 23.52 2.81 50 11.03 4.61 to 18.89 6.42 to 8.29 5.87 65 23.64 5.39 85 10.81 3.71 X 18.59 2.73 X 9.09 3.81 60 22.67 3.61 65 £ 47.77 24.06 107.31 20.96 2.6 80 27.14 3.92 35 2.7 105 16.82 4.73 40 21.39 4.56 to 9.82 3.68 to 34.82 4.69 65 19.62 5.26 70 27.51 3.87 X 13.10 3.81 X 25.37 4.28 50 13.89 2.97 50 £ 136.23 21.32 73.25 20.45 2.8 110 10.33 2.47 35 9.23 1.86 to 7.12 3.24 55 11.78 2.73 X 8.99 1.97 45 £ 47.45 12.27 240 TABLE A4.2 ZOSTERA BIOMASS SURVEY - DRY WEIGHT (g) - JANUARY 1976. (Site locations shown on Fig. 2.1. and Fig. 4.3) GRIFFINS BAY TRANSECTS 3 AND 4 Water Shoot Water Shoot Depth Organic Length Depth Organic Length Site cm Zostera Ruppia Algae Matter cm Site cm Zostera Ruppia Algae Matter cm 3.1 40 0.66 0.19 0.26 5 3.2 50 12.41 4.55 15 1.77 0.30 to 6.79 0.61 to 2.14 0.10 1.94 15 4.03 0.08 0.49 45 0.22 0.99 1.84 X 4.07 2.20 0.03 2.77 X 3.35 1.91 1.52 10 3.04 0.01 0.68 30 Z 8.14 3.09 0.10 5.86 30.34 2.20 0.12 9.10 3.3 60 1.69 4.68 3.44 35 3.4 70 18.74 1.81 45 6.90 0.08 2.28 to 16.27 2.08 to 6.23 0.04 8.58 1.62 60 17.92 0.1 1.98 65 13.89 0.63 1.04 X 9.27 1.67 3? 13.87 0.64 1.93 50 21.57 1.82 55 Z 42.58 0.04 14.61 10.31 83.77 0.1 9.36 3.5 80 22.16 3.12 45 3.6 90 6.35 0.88 3.51 45 15.03 0.52 2.26 to 9.09 0.15 1.02 to 14.41 0.28 1.44 70 12.27 0.31 2.10 70 15.19 0.19 2.52 X 2.35 1.36 0.67 X 15.64 0.12 0.89 60 4.72 0.89 0.88 60 Z 82.43 1.11 10.23 34.78 3.59 8.18 4.1 55 2.60 1.32 0.46 20 4.2 65 4.73 5.18 1.98 25 3.24 1.43 2.59 to 5.64 1.48 3.09 to 4.10 0.29 1.17 0.38 45 4.53 3.14 2.36 50 5.22 0.05 0.08 1.56 X 8.64 4.02 3.09 X 4.37 0.16 0.94 0.59 35 5.44 4.42 2.63 40 Z 19.53 1.82 3.62 5.58 28.98 18.24 13.15 4.3 75 12.81 1.19 2.98 40 4.4 85 19.66 1.15 4.30 45 12.65 2.45 1.00 to 23.70 0.75 5.65 to 20.94 0.53 2.80 60 25.21 0.73 4.46 75 16.86 1.49 3.39 X 21.92 0.58 3.24 X 18.72 0.28 4.48 50 24.58 0.28 0.66 65 Z 81.98 5.94 14.65 115.07 0.28 3.21 18.31 241 D WNJtOHHHHHHHHHH NJHO^ODvl(^Ln^WMHO^)(DvJ(?in^WNJH CA oooooooooooooooooooooo 3 r+ Qi 3 Ti ri v)Njoo h-'O'sDOO'OCT'Ln^UJNJl—'OOOOOOOOOO I OOOOOOOOOOOOI I I I I I I I I to I I I I I I I I I I I I hhoido3^^^^uho3 g g g g g g g g £*QOOOC0OroO O NJ "J - * ' " " " " " " CL ggggggggsggg _ a> > > ...... g [/i g w tii a a a g 3 CL (Dt3(D^^(D(D(D(DW (D cLQiCbQjPj(0PiaOiQigpiQ)a(D^D^?ai(D 3(D(l)(D(D(Dt3(II(D(D(D(DH-f1H-f1hWW(flH- w33333p^^g3CLcwgww(Da)(Dcu; CDwwcowwHwcn(/)cnH-ga>ga>a)^ ^ go * (D(Tl(T)(DfD(fifD(DfD(l)C ' ' ' > - Q (D ' ' 3 in cn ui cn g C?> cr* co ■» in in Oiouiwwoino^'' in si sj O' o in OOcncn ^Qootoogggo^ ^ w w 8 f|fp S 8 8 P I g o-ISS ?'• 3 ID '• .ft. 00 O O' E Cb M 0 ui m to (5 M m i 1 I I 3 to « CO o (A I 3 cn (A cn 242 (O ISJ NJ t—• I—• I—‘I—1 t—• I—'I—• ■ I—1 t—' g K)HOWa)NlO'Ult>UMHOlDa)'JO'UliliUWI-1 in oooooooooooooooooooooo 3 rt s3 o s CD 0) *0 rt rt CD OO^UlfOWOUlUlUlUlOOOOUMDCDCDHOOa) ^ h< ►-*Ov0OO'O(r>Cn*D>U>NJMOOOOOOOOOO I OOOOOOOOOOOOI I I I I I I I I M I I I I I I I I I I I I WWMHHHHHHHHHOOQW^fOMLninB toooo)CDNiyiui^wHH03 3 3 3 3 3 3 3 " 0UJ0Ln00 COMPARISON OF SELECTED MORPHOLOGICAL FEATURES OF 2.CAPRICORNI, 2. MUELLER! AND THOSE OF SAMPLES FROM SITES 1, 3 AND 4. Characters according to den Hartog (1970)______Characters of plants in Illawarra Lake Z.capricorni Z.muelleri Site 1 Site 3 Site 4 Rhizome. Diameter 0.75- 2mm 0.5 - 1.5mm 3 - 4mm x 1.5 - 2mm 1.5 x 1 - 3 x 2mm 1.5 x 1 - 2.5 x 1.5mm oval in section oval in section oval in section Internode 4 - 40mm 4 - 31mm 5 - 30mm 10 - 45mm 5 - 35mm Leaf Blade Sheath 2 - 10cm long, as 1.5 - 11cm long 30cm 24cm 7 - 12cm wide as base of blade- generally wider than Lower halves of Lower halves of Lower halves of narrow membranous flaps blade, lower halves flaps overlap. flaps overlap. flaps overlap. which DO NOT overlap. of flaps OVERLAP. Length 7 - 50cm 5 - 30cm Shoot to 86mm Shoots to 81cm Shoots to 50cm 20cm sheath, 66cm blades 35 - 40 cm some blade, Av. shoot 75cm. stools short 25cm with blades 18cm. Apex Truncate, slightly Obtuse or truncate Some ± notched (up Obtuse or truncated Obtuse or truncated. denticulate. ± deeply notched. to 10% in some samples) -notched in minority NOT NOTCHED. (5%) if notching occurs then present in both fertile and sterile shoot. Fertile Shoot Axis - taken to be 1 - 30cm Very variable 1cm. 30 - 50cm to 50cm. 12 - 40cm. base to last tidal water to 50cm branch. in still water. Peduncle Length free portion 9 - 20mm 6 - 60mm 25mm 20 - 35mm 20mm Width Q, 5mm 0-25-.75mm 0.5 - 1mm 1 - 2mm 0.5 - 1mm Prophyllum Size 15mm x 2xran 25 - 35mm x 2.5mm 25 - 35mm x 2.5mm Spathal Sheath Length 14 - 16mm 16 - 55mm 30mm 25 - 35mm 25mm Width 1.5 - 2mm 1*5 - 2•5mm 3mm 2.5mm 3mm Spadix Shape Linear to sessile, linear linear distinct linear small linear apical spatulate-short lanceolate, obutse apical process apical process process on mucro blunt mucro with distinct apical on mucro less distinct - process. more prominent on some No. (3* flowers 7-10 pairs 4-12 pairs to 12 pairs to 8 pairs to 11 pairs anthers anthers anthers anthers anthers No. Q flowers 7-10 4-12 to 12 to 8 to 10 244 M tO M M H* h3 wtoco^^ui^toto h-* M M (D CD HMHO'X)03v]tOH CD ujtotototorotototo to M M M H* (jj JS* tn tn O O O tn tn II 1 1 1 1 1 CD iti W H Ul O' ^ kD tn O OUlUlOOMfO h-* II 1 1 1 1 1 <0 vD tn tn 4* tn (T\ Ui O Oi O O Ui Oi H to H H H H H tn O O O O O tn 1 1 1 1 1 1 1 COintOHHHWCOOD oooinmuiuiiUco to 1 1 1 1 1 1 1 <0 CD £> O O tn O O tn O cn rt ^ £> to to to ^ lU 0) tn o tn o o o o 1 1 1 1 1 1 1 M tnOOOtnOOtOM to £ ^ 1 1 1 1 1 1 rt O kD ^ 4^ O 00 O O tn in in in O H* M M M m to to tn in tn in tn O O 1 1 1 1 1 1 1 *u^tototo^£>£>tn tnOOOOtntnooco 1 1 1 1 1 1 1 Ui in ^ w to in on tn O O O tn O O H to M M M H-* M M 0 in in o O in in 1 l l l 1 i 1 to ^inwtoHiotOsi^ J—1 tnOtnotnOOOOO tn 1 1 1 1 1 1 1 vi in oj to m tn tn o o O O O to 1—• 1—• t—* 1—• 1—* 1—* 0 tn O O O tn tn 1 1 1 1 1 1 1 di^tOHHtOfOvJvl tnOOtntnOOOO (T> 1 1 1 1 1 1 1 vj OI w w to w ^ tn O tn o O tn O - 5 1 - 0 1 - 0 1 - 5 1 - 5 1 - 0 1 - 0 1 tn^WtOHHHO^^ tnOOOtntntntnto ^1 1 1 1 1 1 1 1 0^ in tn to to to to tn tn O tn tn O O M M H-* M M M M tn tn o o o o o t i l 1 1 1 1 - 5 6 68 - 0 4 70 - 0 5 - 5 3 - 0 3 - 5 1 - 5 1 00 -j tn ^ to to tn tn o O O tn O O 245 TABLE A4.6 VARIATION IN ANTHER NUMBER ZOSTERA CAPRICORNI SPADICES - 24 .9.1972. (Site locations shown on Fig. 2.1.) Spadices Spadices with anthers Spadices without anthers per visible visible fertile shoot No. Anthers on each No. Juvenile Dehixed Site 3 14 4 13,12,11,14, 10 X - 2 2 23,19 0 - - 2 1 23 1 X - 3 2 17,18 1 X - 4 2 27,24 2 X - 4 3 15,12,12 1 X - 7 4 26,17,14,23 3 X - 4 1 25 3 X - 4 3 22,14,20 1 X - Site 4 5 5 14,14,15,15,13 0 - - 7 0 - 7 X - 2 1 19 1 - X 18 2 18,15 16 - X 8 1 18 7 - X 4 1 15 3 - X 3 1 17 2 X - 5 1 28 4 - X 5 3 25,22,23 2 - X 5 2 23,15 3 - X 9 2 17,21 7 X X 5 1 22 4 X X 246 TE IT S dP t-3 to cd dP cn U) § f 0 1 ' i £ s £ s rt cd (D cd 0) cn 'O 01 cn tO to 1 r 218 1 8 3 HN)MHtV)WU)N)H LOtOWtOUlWW^HtO (T>COtO cn M 2 dP tv) CD toto^l 1 OJUlLOWt-'UI 00 1 1 M tO tO 1 H tO 1 O 199 co tOWHfOHWMHHtO 4*. J»HtOMWWWWHU1 tOOOJtOODO^tOtOtOtO M oo>t»'-Jcnfoa5.P»i-i'0>&> CD M C CD CD to dP ______11 tv) cn 17 12 4 4 2 4 2 3 •O 2 1 Ln 3 3 7 | 7 L L 196 260 N) W H H tO H H tO tO (OtOHtO^WtOtOtOtO cDtOO>OOOMOO(T*COCO OltOOlWtOWWOtOsl w tv) co E to CO dP ____ 15 22 CO 5 1 o 3 3 5 1 5 0> O H to H w | CD CO t 204 ST to HHHHtOHWH HHHHtOtOWtOHtO tv) OcDHCT>01WWCOtO^ (DUlUlslHIO^sJslO CD to C tv) dP dP CO CO WU)(T»U)CnU)CD^tOH to w H l oj co Ln Ln cn CD ^ Tl ABUNDANC! L tv) e tv) (OtOHtOtOtO^HHtO ucj^toO)wcocouico CD ^OtOWO^WWWHHW 98 COLJtOvltOCDCDvlLnLn ______M cn iU to dP tv) M CD ^ tO H H 0) ^ ^ 1 K-*CD 1 1 ^ 1 ^ 1 1 CO ON 1 tv) 277 Cn HCOtOtOUJWtOlOtO tOtOHWtOWtOtOWW CD I-* HtOCDOOOCDHlDtO^ HO^HvltOcDOsJCDO CD M CO dP to to to co 1 h 0) to oi cn i 4* 1 1 1 1 1 1 1 CO M 1 225 208 HH^HtOtOtOWtO HHIOtOHWiUtO M CD NiHtoo^oocnoi^ww (DLncoto^ocTtooocn iO M o * tv) to H to 1 to U) cn CD H 1 to 1 1 1 1 I I 1 to 1 1 tv) 338 (J\ HtOCOfOWWtOUJtOtO W^^tOCOCOCOCOLOH CD HHOltOOlCDsJtOWIO LnCT'CT'vlOO^tOCDtOCT' S to 00 CO cr» dp Ln 11 20 4 1 1 7 9 1 CD 1 to 1 M 0> 1 1 1 1 1 247 to H to to to____ 3 00 E •-3 O M i M i w £ NJ ft CD C/) (D w W (/) u Jo i 194 w H tO H M M M tO tO M tO M M tO M to M v£vQCT>tocnvO-JOCnv£) vJ^DCD^^O^slvJHM OO to 00 00 ______00 to dP dP 10 n 14 10 on 12 6 6 1 = 4 9 5 8 5 8 5 9 2 1 1 VO 1 l l L 0 7 1 0 3 1 HHHtOHHHHIOH M M M M M M M iUCt»0nCT'0O*tw00O^^*U ^vOslVOMslvOMCTivJ 5 to dP CO 00 (J^^UlOnHHHHH 1 W si a) to M M 1 00 00 00 176 11 22 27 17 11 tO IO H tO to MM 17 37 16 9 S 9 vDcoto^Mtoon^Mon to 00 VO 00 ______on dP dP 16 23 17 19 21 4 4 (Tv 6 4 7 00 6 1 2 5 5 3 3 5 1 on VO | l l 0 6 2 184 MMtOMMOOtOMtOM OOtOOOMtOtOtOOOMtO to ►UODMOMtT'OOOtOvO on s VO ^l,t*Cniti o 1 148 w 204 MMMMMMMMMM MtOMOOtOtOMMMtO O^^NjN](^OnM1UsJO> VOOOVOMMIOCT*OOVOM o to M w § on o dP dP I 00 w M (OWWW^.bO'UOUl to (vJOJ 1 Cn NJ £. 4* £ g on 15 10 (T* 4 4 9 9 2 oo wuMinuiMOiHoodo 00 5 5 5 248 TABLE A4.8 ZOSTERA - FERTILE SHOOTS AND MATURITY OF SPADICES. 3.10. 1972. No. No. No. No. No. No. No. No. Site Infl'ce Dehis . Mat. Juv. Site Infl'ce Dehis.. Mat. Juv. 1 1 - - 1 4 5 2 3 - 3 - - 3 6 2 3 1 1 -- 1 1 - - 1 1 -- 1 8 5 2 1 1 - - 1 2 - - 2 1 - - 1 1 __ 1 1 -- 1 3 -- 3 1 -- 1 10 5 3 2 10 - - 10 5 2 - 3 3 _ _ 3 2 2 “ ” 2 8 2 4 2 1 1 — 1 1 5 2 1 2 3 3 1 “ “ 1 6 3 3 1 1 2 2 3 1 2 64 21 18 25 1 - i 5 6 1 3 2 10 4 3 3 3 - 2 1 10 3 5 2 5 - 3 2 10 8 1 1 3 - _ 3 5 - 2 3 3 - _ 3 1 - - 1 4 1 2 1 1 - - 1 4 - 2 2 1 - - 1 1 - _ 1 1 -- 1 4 - 2 2 2 - - 2 4 - 3 1 3 - - 3 37 2 17 18 4 1 3 3 - - 1 6 1 - - 1 67 17 14 36 1 -- 1 1 - 1 3 3 - - 3 1 -- 1 5 - 1 4 1 - - 1 3 - 1 2 4 - - 4 1 - - 1 2 _ 1 1 7 2 - - 2 1 1 1 - - 1 3 3 _ 3 - - 3 3 - 3 8 2 __ 2 1 - - 1 1 _ _ 1 4 1 2 1 3 __ 3 1 - - 1 2 _ 1 1 5 - 3 2 1 _ _ 1 1 - - 1 1 __ 1 4 - 1 3 1 _ _ 1 1 1 - 2 - - 2 3 3 " 13 - 1 12 1 2 3 1 1 1 4 - 2 2 3 - 1 2 54 5 15 34 Cont. 249 TABLE a4,8 Cont. ZOSTERA - FERTILE SHOOTS AND MATURITY OF SPADICES. 24.10.1972 No. No. No. No. Length No. No. No. No. Length Site Infl'ce Dehis. Mat. Juv. cm Inf11ce: Dehis. Mat. Juv. cm 11- 1 66 3 - 2 1 21 2 1 32 3 - 1 2 41 3 3 31 5 2 2 1 33 2 2 30 3 - - 3 32 2 2 40 3 - 1 2 26 2 2 43 2 - 1 1 28 4 2 54 7 1 3 3 39 4 1 1 42 3 - 1 2 32 1 1 36 4 - 1 3 29 1 - 1 38 2 - - 2 28 22 1 16 35 3 12 20 = = — = 2 1- 1 51 3 - - 3 32 6 2 1 3 28 2 - 1 1 17 4 1 3 39 1 - - 1 18 5 2 3 48 3 - 2 1 27 4 1 3 37 2 - 1 1 19 5 1 2 2 36 5 - 3 2 23 5 1 1 3 45 7 - 3 4 26 3 1 2 42 1 - - 1 23 3 1 2 43 5 2 2 1 19 6 - 2 4 48 2 - - 2 21 42 4 12 26 31 2 12 17 9 5 4 52 3 - 1 2 35 7 4 2 49 2 - 1 1 30 5 4 1 41 6 4 1 1 33 1 1 38 6 2 2 2 32 6 4 49 5 1 2 2 29 3 3 51 4 1 2 1 29 10 2 3 45 4 2 1 1 32 3 2 1 51 1 - - 1 40 8 6 1 1 53 1 -- 1 33 14 10 2 2 56 4 2 1 1 31 66 22 22 22 36 12 11 13 10 3 3 38 1 - - 1 57 8 6 2 41 3 - 1 2 40 18 11 2 5 51 3 - 1 2 39 7 1 6 48 6 2 2 2 42 6 2 1 3 44 3 1 1 1 33 5 2 3 45 7 3 2 2 41 10 6 2 2 38 6 1 2 3 43 4 4 55 5 1 2 2 37 8 5 1 2 43 2 - 1 1 44 7 2 3 2 42 3 - 1 2 38 83 35 16 32 39 8 13 18 Cont. 250 TABLE A4.8 Cont. ZOSTERA FERTILE 1SHOOTS AND MATURITY OF SPADICES. 12.:L2.1972 No. No. No. No. Length No. No. No. No. Length Inf1'ce Dehis. Mat . Juv. cm Site Infl'ce Dehis. Mat,. Juv. cm 12 5 3 4 5 8 6 1 1 11 1 4 6 7 5 1 1 8 3 3 2 40 17 8 5 4 42 2 1 - 1 to 6 3 2 1 to 2 - - 2 80 8 6 1 1 64 5 - - 5 cm 10 7 1 2 cm 8 2 2 4 8 4 3 1 14 4 6 4 16 10 3 3 12 4 5 3 9 7 2 - 5 2 1 2 4 4 - - 79 22 24 33 93 60 19 14 12 4 6 2 6 6 3 2 1 8 - 2 6 5 1 1 3 7 1 3 3 48 10 5 3 3 45 5 - 3 2 to 11 6 2 3 to 10 5 2 3 100 7 3 2 2 70 11 2 2 7 cm 8 3 3 2 cm 13 3 4 6 13 9 2 2 6 2 1 3 13 9 2 2 4 1 2 1 5 3 1 1 10 4 2 4 9 6 1 2 86 22 27 37 87 48 19 20 4 1 1 2 7 7 3 2 2 5 2 2 1 12 10 1 1 5 2 2 1 45 11 7 2 2 35 11 8 1 2 to 6 3 1 2 to 5 3 1 1 78 7 5 1 1 60 2 - 1 1 cm 9 5 2 2 cm 12 7 1 4 7 1 3 3 17 10 2 5 6 4 1 1 3 1 - 2 16 8 4 4 4 1 1 2 12 8 2 2 68 35 12 21 93 54 19 20 9 7 _ 2 8 6 1 3 2 14 10 1 3 11 5 4 2 6 5 - 1 32 13 7 3 3 40 8 6 1 1 to 11 8 2 1 to 3 3 - - 41 13 8 2 3 65 10 8 - 2 cm 11 8 1 2 cm 12 10 - 2 4 2 1 1 10 8 1 1 15 10 3 2 3 - 1 2 10 8 1 1 12 5 3 4 14 10 2 2 87 62 7 18 108 67 22 19 Cont. 251 TABLE A4.8 Cont. ZOSTERA - FERTILE SHOOTS AND MATURITY OF SPADICES. 3.1. 1973. No. No. No. No. No. Length No. No. No. No. No. Length Inf1'ce Decid. Dehis. Mat. Juv. cm Site Infl1 ce Decid. Dehis . Mat. Juv. cm 21 7 9 1 4 5 45 19 19 3 4 14 7 5 2 1 10 7 3 -- 16 6 6 2 2 58 11 4 5 1 1 28 9 1 2 3 3 to 10 6 3 - 1 to 16 8 4 2 2 70 23 11 8 1 3 66 24 9 9 3 3 cm 15 7 7 - 1 cm 9 5 2 - 1 14 8 5 1 - 17 6 7 2 2 15 8 6 - 1 19 9 6 2 2 10 7 3 - - 19 4 11 2 2 39 17 15 2 5 165 62 61 19 23 192 94 74 8 16 20 7 9 2 2 6 9 4 4 1 - 19 6 10 2 1 17 9 7 1 - 16 8 7 - 1 43 12 5 5 1 1 33 22 10 8 2 2 to 19 8 7 2 2 to 6 1 5 - _ 81 18 5 9 2 2 52 20 3 12 2 3 cm 9 3 4 1 1 cm 7 2 3 1 1 19 10 5 2 2 23 9 10 2 2 11 5 4 1 1 19 10 7 - 2 12 5 6 - 1 26 10 11 3 2 18 1 12 1 4 178 66 82 14 16 144 55 63 12 14 21 10 7 2 2 7 21 9 8 2 2 18 6 7 3 3 10 3 5 1 1 30 19 7 2 2 63 21 11 6 2 2 30 13 7 5 - 1 to 19 8 8 1 2 to 26 7 12 4 3 97 9 5 4 - - 50 23 10 8 2 3 cm 26 6 14 3 3 cm 10 4 4 1 1 22 9 9 2 2 13 5 5 1 2 12 9 1 1 1 35 19 10 3 3 15 8 7 - - 10 3 5 - 2 19 7 9 1 2 199 90 70 18 21 174 75 71 13 15 9 3 4 1 1 8 9 3 4 1 1 9 3 4 1 1 9 6 2 1 - 11 4 5 1 1 35 19 8 6 2 3 40 9 3 4 1 1 to 20 7 11 1 1 to 15 3 9 1 2 40 12 6 4 - 2 54 13 5 6 1 1 cm 14 7 5 - 2 cm 13 7 5 _ 1 10 2 6 - 2 17 5 8 2 2 10 4 4 1 1 5 - 3 _ 2 20 8 8 2 2 21 9 10 1 1 14 7 5 1 1 122 42 58 9 13 137 58 55 9 15 252 TABLE: A4.9 ZOSTERA - ABUNDANCE OF DEVELOPMENTAL STAGES OF SPADICES. (SUMMARY OF DATA FROM TABLE A4.8) Development Stage % % % Date Site Dehis. Mat. Juv. 3.10.72 1 - _ 100.0 2 25.4 21.0 53.6 3 9.3 27.8 63.0 4 32.8 28.2 39.0 5 5.4 46.0 48.6 6 - - 100.0 7 - - 100.0 8 - 7.7 92.3 24.10.72 1 4.5 22.5 73.0 2 9.5 28.5 62.0 3 33.3 33.3 33.3 4 42.0 19.5 38.5 5 8.5 34.5 57.0 6 6.5 39.0 55.0 7 33.5 30.5 36.0 8 20.5 33.5 46.0 12.12.72 1 27.8 30.4 41.8 2 25.6 31.4 43.0 3 51.5 17.7 30.9 4 71.2 8.1 20.7 5 64.5 20.4 15.1 6 55.2 21.8 23.0 7 58.0 20.4 21.6 8 62.0 20.3 17.6 (a)* (b)* (b)* (b)* % % % % Infl'ce Dehis. Mat. Juv 3.1.72 1 62.4 59.2 18.4 22.3 2 62.9 73.2 12.5 14.3 3 54.8 64.2 16.5 19.3 4 65.6 72.5 11.3 16.3 5 51.0 75.5 8.2 16.3 6 61.8 70.8 13.5 15.7 7 56.9 71.7 13.1 15.1 8 57.7 69.6 11.4 19.0 (a)*% inflorescences calculation based upon the total number of inflorescences discernable on a fertile shoot and includes both current inflorescences and those deciduous, i.e.,______extant_____ x 100 extant + deciduous 1 (b)*% calculations based upon extant inflorescences only. 253 TABLE A4.10 ABUNDANCE OF FERTILE SHOOTS - ASSESSMENT OF SAMPLING TECHNIQUE - SITE 4, 1-10-1972. (Site location shown on Fig,. 2.1), Setsi of 10 samples 1. 2. 3. 4. 5. No. Sterile Shoots. 221 186 162 252 162 No. Fertile Shoots. 33 28 26 38 24 TOTAL 254 214 188 290 186 % Fertile. 13% 13.1% 13.8% 12.8% 12.9% Average % Fertile Shoots = 13.1% Range 12.8% to 13.8% Deviation from mean =+0.7 = + 5.3% 1371 0.3 = - 2.3% 1371 i.e. Sampling deviation range = + 5.3% 254 TABLE A4.ll ABUNDANCE OF SEEDS - ZOSTERA CAPRICORNI (Site locations shown on Fig . 2.1) No. Spadices Total No. Date Site Bearing Seeds Seeds 12.12.72 1 3 5 3 6 21 4 9 28 5 2 7 20 61 3. 1.72 1 4 16 2 2 5 3 6 21 4 8 28 5 4 13 6 5 9 7 6 11 8 5 12 40 U5 m^mm Total spadices observed 12.12.1972 ..... 700 Total dehiscent spacides 12.12.1972 .... 370 Observed seed set rate, 20 of the 370 dehiscent spadices, i.e., 5.4% of spadices produced seeds. Allowing for an average of 8 flowers per spadix, then the sample contained 8 x 370 = 2,960 flowers of which 61, i.e., 2% produced seeds. Total spadices observed 3.1.1973 ...... 769 Total dehiscent spadices 3.1.1973 ...... 545 Observed seed set rate, 40 of the 545 dehiscent spadices, i.e., 7.3% of spadices produced seeds. Allowing for an average of 8 flowers per spadix, then the sample contained 8 x 545 = 4,360 flowers of which 115, i.e., 2.6% produced seeds. It was not alway possible to determine if a spadix that had reached the stage of anther dehiscence would actually produce seeds. Even allowing a generous margin for this factor, the rate of seed production would not have exceeded 5%. 255 TABLE A4.12 FLOWERING OF ZOSTERA CAPRICORNI - 1975 - 1976. (Site locations shown on Fig. 2.1) 1 ; ; ; ] < 1 J Date 5.10.75 20.11.75 15.12.75J ; 8.1.76 7.2.76 j • fertile of fertile of fertile fertile fertile of of of 9 4TS fertile fertile fertile fertile fertile % Shoots Seeds shoots Seeds Shoots Number Number Number Number % Seeds % shoots Shoots % shoots Shoots % shoots Shoots shoots Seeds Seeds Number Number Number Number Number Number A . 4 1.6 . 11 4.6 1 16 6.8 11 . B . 15 4.3 44 27 12.6 72 27 15.3 53 2 1.0 1 C . 22 5.6 13 31 15.8 16 38 22.7 48 7 3.4 6 E • 36 6.1 15 19 10.3 21 22 18.1 39 . F 9 6.6 . 46 11.9 4 43 16.8 17 41 25.2 27 3 1.2 2 H • 15 4.7 15 21 8.8 23 26 11.2 17 . I . 29 17.4 1 23 11.4 3 27 12.8 9 J 28 14.7 185 25 12.7 172 28 14.4 92 • TABLE A4.13 SEED PRODUCTION - ZOSTERA CAPRICORNI - 1975 - 1976. Date Item 5.10.75 20.11.75 15.12.75 8.1.76 2.2.76 No. Dehiscent Spadices 4 3.19 576 624 47 No. flowers estimated* 30 2550 4600 4990 375 No. Seeds 0 277 325 296 9 % fertile flowers 0 10.9 7.1 5.9 2.4 ♦Number of flowers estimated on X of 8 flowers per spadix. 7 ACKNOWLEDGEMENTS I wish to thank my supervisors, Br. R. King, School of Botany, University of New South Wales, and Br, J, Ellis, Chemistry Bepartment, Wollongong University, for their assistance and guidance throughout this project. Thanks are also expressed to Professor M, Hindmarsh of the School of Botany, University of New South Wales, and Br, J, MacIntyre, Zoology Bepartment, University of New South Wales, for providing the encouragement that initiated this project; to Br, P, Rowley for his guidance in the development of electrode techniques; to Br, S, Kanamori for his guidance in chemical analysis procedures and for providing access to his data; to Ms J, Guy for assistance in developing sediment analysis procedures; and to Br, L, Collett for identifying the "benthic macrofauna. I wish also to acknowledge grants from the N.S.W. Electricity Commission and the Bepartment of Urban and Regional Bevelopment of the Australian Government, under a National Estate Grant provided to the Wollongong City Council for the Illawarra Lake Environmental Assessment Project, Finally, I wish to express my gratitude to my wife, Pat, for her assistance with field work and typing of this thesis.