THE BENTHIC FAUNA OF

THE TUGGERAH LAKES

B. J. Powis

This thesis is submitted for the

Degree of Master of Science at

University of New South Wales

JULY, 1975. UNIVERSITY CF N.3.W.,,

55701 1 3. JAN. 7 6 LIBRARY This is to certify that this thesis has not been submitted for a higher degree to any other university or institution. ACKNOWLEDGEMENTS

I would like to thank Dr. R.J. MacIntyre for his

continued guidance and advice throughout this project.

This study was financed by the Electricity Commission

of N.S.W. and the Wyong Council. I would like to thank

them for this assistance.

I would also like to thank the Electricity Commission

for their cooperation and assistance in the collection of

field material.

I am grateful to the following people for their assistance in the identification of the various taxonomic groups: Dr. Pat Hutchings (polychaetes), Cathy Drummond

(crustaceans) and Dr. Winston Ponder (molluscs).

I am also very grateful to Leon Collett who has given a great deal of assistance in many areas of this study, especially with the computer analysis.

With regard to the use of computer programs I would like to thank Alan Collins who has given a great deal of assistance with the computer analysis.

Thanks are also due to Professor Stephenson for his advice on statistical procedures.

Considerable assistance has been given in the collection of samples by Bill Jefferson, Stephen Sparkes, Gary

Bebbington, Bruce Hodgson and Ray Wallis.

For proof reading and grammatical correction of the text

I would like to thank Helen Stoddart, Charles Pregenzer, Harry

Booth and Paul Kloedon.

I would also like to thank Judi for her expert drawings and Mrs. Hutton for her typing. SUMMARY

Qualitative and quantitative studies were conducted on the benthos of Tuggerah Lakes. Fifty-eight sites were sampled in the qualitative study using a diver-held corer. Information analysis was used to delineate the major faunal groups. Four groups were found and all were related to the substrate type. The substrates were; mud, sand, weed in mud, and weed in muddy sand. Nineteen sites were sampled in the quantitative surveys.

These were sampled both in winter and summer. Within any substrate the fauna throughout the three lakes was homogeneous and seasonally stable. The most diverse communities were those associated with the weed Zostera capricorni. Assessment of the effects upon the benthos of Munmorah Power Station and of weed clearing operations were made. The Power Station discharge changed the community structure in weed beds. Only in weed near the discharge were found large numbers of the gastropod Velacumantis australis. A "before and after" study of a weed clearing operation showed that it greatly reduced the numbers of both species and individuals living in the test plot. The effects upon the benthos of a very severe flood were shown to be rather variable. The mud and Halophila fauna was greatly euffected with a reduction of species and of individuals. However, no other weed areas were affected. CONTENTS PAGE

LIST OF FIGURES i

LIST OF PLATES

CHAPTER 1 INTRODUCTION 1

CHAPTER 2 AREA STUDIED 3 2.1 TUGGERAH LAKES 3 2.2 LAKE MACQUARIE 5

CHAPTER 3 PRELIMINARY SURVEY 9 3.1 INTRODUCTION 9

3.2 METHODS 9 3.3 RESULTS 15 3.4 DISCUSSION 30

CHAPTER 4 QUANTITATIVE SURVEY 31 4.1 INTRODUCTION 31 4.2 METHODS 31 4.3 RESULTS AND DISCUSSION 35 4.31 Faunal Similarity 35

4.32 Community Structure of Site 43 Groups

4.33 Comparisons with Fauna of Lake 56 Macquarie

CHAPTER 5 THE EFFECT OF A SEVERE FLOOD UPON THE 63 BENTHOS

5.1 GENERAL EFFECTS 63 5.2 THE HALOPHILA COMMUNITY 64

5.3 FAUNA OUTSIDE OURIMBAH CREEK 68 CHAPTER 6 THE EFFECT OF WEED CLEARING OPERATIONS UPON 72 THE BENTHOS

6.1 INTRODUCTION 72

6.2 METHODS 74

6.3 RESULTS AND DISCUSSION 74

CHAPTER 7 THE EFFECT OF POWER STATION DISCHARGES UPON 77 SHALLOW WATER BENTHOS

7.1 INTRODUCTION 77

7.2 SCUBA OBSERVATIONS 79

7.3 BEHAVIOURAL EXPERIMENTS 79

7.4 POWER STATION DISCHARGES AND BENTHOS: 83 AN OVERVIEW

CHAPTER 8 GENERAL CONCLUSION 84

REFERENCES 85

APPENDIX A SITE/SPECIES DATA FOR PRELIMINARY SURVEY 87

APPENDIX B CLASSIFICATION TECHNIQUES 95

APPENDIX C SITE/SPECIES DATA FOR QUANTITATIVE SURVEYS 108

APPENDIX D HYDROLOGICAL DATA 113

APPENDIX E DESCRIPTION OF SPECIES 117 LIST OF FIGURES

PAGE Tuggerah Lakes 2 2 Sediment of Tuggerah Lakes 4 3 Circulation in Budgewoi/Munmorah Lakes g

4 Lake Macquarie 7

5 Sampling Sites in Munmorah Lake 10

6 Sampling Sites in Budgewoi Lake 11

7 Sampling Sites in Tuggerah Lake 12

8 Distribution of Nassarius fonasi 17 9 Distribution of Xenostrobus securis 18

10 Distribution of Owenia fusiformis 19

11 Distribution of Nereis (Hediste) diversicolor 20 12 Distribution of Macoma deltoidalis 21 13 Distribution of Family Capitellidae 22 14 Dendrogram of Site Groups in Preliminary Survey 24 15 Topographic Illustration of Site Groups 25 16 Isoplethes of the Abundance of Owenia fusiformis 29 and Nereis diversicolor 17 Sampling Sites for Quantitative Surveys 32

18 Dendrogram of Winter Site Groups 36 19 Topographic Illustration of Winter Site Groups 37

20 Dendrogram of Summer Site Groups 39

21 Topographic Illustration of Summer Site Groups 40

22 Number of Species in Mud Zone 42

23 Number of Individuals in Mud Zone 42 24 Particle Size Structure of Sediment in the Mud 44 Zone 25 Number of Species at Zostera Sites 48 26 Number of Individuals at Zostera Sites 48 ii

27 Abundance of various species at Zostera Sites 49

28 Sampling Sites in Myuna Bay 59

29 Salinity Levels at Site 3 for the Period 62 4/73-12/74

30 Total Number of Individuals Present in Mud Zone 66 before and after the Flood

31 Distribution of Dead Velacumantis Outside the 78 Discharge of Munmorah Power Station

32 Test Chamber Used in Behavioural Study of 80 Velacumantis

33 Response of Velacumantis to a Temperature 82 Gradient

34 Choices of Classification 97

35 The Dendrogram 97

36 Divisive and Agglomerative Dendrograms 100

37 Group Average Sorting 105 iii

LIST OF PLATES

PLATE PAGE

1 A Core being taken in Shallow Water 14

2 Owenia fusiformis 27

3 Nereis diversicolor 27

4 A Core being taken in Deep Water 46

5 Debris from Ourimbah Creek 67

6 Weed in. Budgewoi Lake 71

7 Weed Clearer in Operation 73 1

CHAPTER 1

INTRODUCTION

Benthic animals live in or above the sediment. They

are an integral part of the aquatic food chain. Apart from

work conducted by MacIntyre (1959) there is very little

knowledge regarding the ecology of benthic animals in

estuarine lakes in Australia. It was the aim of this

investigation to examine in detail the benthos of the

Tuggerah Lakes.

The Tuggerah Lakes fauna were examined in two ways.

Firstly, a qualitative study was carried out to establish

what species were present and where. Secondly, a

quantitative seasonal study was done to examine the

differences in community structure of the benthos throughout

the three lakes. A comparative study was also carried out

on the fauna of Myuna Bay in Lake Macquarie.

The area around Tuggerah Lakes is rapidly becoming the

site for large scale regional development. The effects of

man's influence upon the lake system need to be minimal if

the lakes are to survive unchanged. This study examined the

effects upon the benthos of changes in the lakes' ecology

induced by power stations and weed clearing operations. The

impact of the changes must, however, be considered in relation

to the effects of natural phenomena. The effects upon the benthos of a severe flood that occurred in the Tuggerah Lakes were also examined. 2

Munmorah Power Station

Wallerah Creek Munmorah

Wyong Creek

Ourimbah Creek The Entrance

Long Jetty

Figure 1. - The Tuggerah Lakes. 3

CHAPTER 2

AREAS STUDIED

2.1 TUGGERAH LAKES

Tuggerah Lakes consist of three interconnected lakes -

Munmorah Lake, Budgewoi Lake and Tuggerah Lake (Figure 1) -

located 112 kilometres north of Sydney. They have an area of 116 square kilometres. The water level in the lakes is controlled mainly by the amount of freshwater runoff, most of which is fed into the lakes by one of three creeks. These are Wallarah Creek located in Budgewoi Lake and Wyong and

Ourimbah Creeks situated in Tuggerah Lake. Tidal exchange is negligible with the rate of seawater exchange being restricted by the narrow channel connecting Tuggerah Lake to the Pacific Ocean. This channel is located near the township of "The Entrance".

The lakes are shallow with an average depth of only 2 metres (Higginson, 1971). They are also essentially brackish with salinities of 17°/oo to 25°/oo being most common.

Tuggerah Lake, because of its connection to the Ocean, has the highest salinities of the three lakes (Harper, 1972).

Three weed species exist in the lakes; Zostera oapricorni Ashers, Ruppia spiralis Dumort and Ealophila sp.

Weiner (1974), working on the distribution of these weeds in

Tuggerah Lakes, has shown that all three species are found in a band around the perimeter of the lakes.

Roy and Peat (1974) have analysed the sediments of the three lakes. Four basic types were recognised; Sand, Muddy 4

Sandy Mud (51-99% mud)

Muddy Sand (0-50% mud)

Sand

Figure 2. - The sediment of Tuggerah Lakes

(modified after Roy and Peat 1974). 5

Sand (1-50% mud), Sandy Mud (51-99% mud) and Mud. A

simplified version of their sediment map is presented in

Figure 2.

A feature of the Munmorah/Budgewoi Lakes is an

artificial warm water current that circulates from the discharge of Munmorah Power Station, located in Budgewoi

Lake, to the intake of the Power Station which is located

in Munmorah Lake (Figure 3).

2.2 LAKE MACQUARIE

Lake Macquarie is 2 kilometres north of Tuggerah Lakes.

It has an area of 69 square kilometres and a catchment area of 240 square kilometres. Water from the catchment area is fed into the lake primarily by one of three major creeks.

These are, Mannering Creek, Dora Creek and Cockle Creek (Baas

Becking et al., 1959). Figure 4 gives topographical details of Lake Macquarie.

The tidal amplitude within the lake is dampened to only

7.5 centimetres by a long winding channel that connects the lake to the Ocean (Spencer, 1959). The salinity within the lake is, however, predominantly marine with salinities usually ranging between 25-30°/oo (Harper, 1972).

The substrate has been classified by MacIntyre (1959) as either Weed, Slope or Mud. The Weed areas are present around the perimeter of the lake whereas the Mud zone occupies the flat lake bottom. The Slope zone is a distinct area between the Weed and Mud zones. The sediment of the lake has been studied by Roy and Peat (1974). They have divided it into four classes of sediment. Apart from areas surrounding Figure 3. - The artificial warn water current that is circulated by the Munmorah Power Station. Cockle Creek

Mannering 4 Km. Creek Station

Figure 4. - Lake Macquarie. 8

"Swansea" channel which is composed of sand, the lakes perimeter is composed primarily of muddy sand (1-50% mud).

The central area of the lakes is composed of mud while the area between it and the sediment of the perimeter is composed of sandy mud (51-99% mud).

Two Power Stations use water from Lake Macquarie as a coolant. These are Wangi and Vales Pt. Power Stations. The locations of these Power Stations is given in Figure 4.

Myuna Bay

Myuna Bay is the actual area that was studied in this investigation. It has all the substrate zones described by

MacIntyre (1959). The weed zone is wide and composed primarily of Zostera oapricorni. 9

CHAPTER 3

PRELIMINARY SURVEY

3.1 INTRODUCTION

A semi-quantitative benthic survey of the Tuggerah Lakes

area was necessary as no previous knowledge existed

regarding the benthos of the area. It was conducted to establish the species present and their distribution.

3.2 METHODS

A. Field and Laboratory Methods

Fifty-eight sites were sampled throughout the three lakes during March-April 1974. Figures 5-7 give locations, and

Table 1 gives descriptions, of each site.

A diver-held corer was used to sample each of the sites.

Plate 1 shows the corer being used in shallow water. The 2 sample taken by the corer was 0.02 m . Two cores were taken at each site and the sample obtained was then washed through a 1 mm sieve. The animals and sediment retained were stored in 10% formalin. The animals were sorted from the sediment using a pair of forceps and a stereo microscope. The animals were then placed in 70% Alcohol and later identified and counted.

B. Computer Methods

Delineation of community groups from large amounts of species/site data is facilitated by computer analysis and many computer programs have been developed for this purpose. Figure 5. - Sampling sites in Munmorah Lake. 11 L a k e .

B udgew oi i n s i t e s

S a m p lin g

-

6 .

F ig u r e 12

49*

Figure 7 Sampling sites in Tuggerah Lake. 13

TABLE 1 DESCRIPTION OF SAMPLING SITES

STATION SEDIMENT WEED COVERING

16/35/2/47/51/49 Muddy sand Zosteva sp.

31/50 Mud t f

18/34/46/32 Sandy mud 11

Halophila sp.

55/17/21/13/58 Muddy sand

28/24/54/37/27 Mud 11

20 Sand f f

45 Sandy mud it

15/22/3/19 Muddy sand Ruppia sp.

30/53/57/44 Mud 11

12 Sand I f

38/1/11/5/4/6/23/

25/48 Sand No Weed

10/14/7/8/9/26/ 56/55/52/42/40/

41/43/39/56/36 Mud No Weed 14

Plate 1 A core being taken in shallow water 15

A discussion of the application of these programs to benthic surveys and a detailed explanation of the techniques used in this thesis is given in Appendix B. The procedure used for this survey is contained in the C.S.I.R.O. computer program designated DIVINF. This uses a monothetic divisive technique based on the Shannon Information

Content of the population, I. The formula for I is as follows: s I = snlnn - £ [a.lna. + (n-a.)In(n-a.)] j = i J J J J where n sites are defined by the presence or absence of s species and that the jth species occur in a^ of the site. Only Normal Analysis (grouping of sites with respect to species present) was carried out. All calculations were based on the pooled results of the two cores from each site. Species which did not occur in each of the two cores per site were eliminated from the analysis.

3.3 RESULTS A. Species Present A total of 33 species were identified from the survey. Tables presenting the species found and the species composition of each site are given in Appendix A. Appendix E gives descriptions of the species collected. Table 2 presents a list of the species found in order of total abundance. The distribution of the six top ranking species is illustrated in Figures 8-13. 16

TABLE 2

RANK OF SPECIES IN ORDER OF ABUNDANCE

SPECIES ABUNDANCE FREQUENCY OF OCCURRENCE

Nassarius jonasi 392 29 Xenostrobus securis 353 28 Owenia fusiformis 234 20 Nereis (Hediste) diversicolor 193 16 Macoma deltoidalis 183 31 F. Capitellidae 181 33 Sanguinolaria onuphia 173 14 Theora fragilis 153 20 Melita sp. 126 19 Velacumantis australis 115 19 Mesanthura sp. 98 23 Notospisula trigonella 70 25 Armandia intermedia 57 18 Austrocochlea constrieta 39 2 Class Actinozoa 32 13 F. Oedicerotidae 27 12 F. Eusiridae 23 9 Parphoxus sp. 18 8 Haploscopolos simplex 15 6 Laternula tasmanica 12 4 Exoediceros sp. 11 3 Orchestia sp. 9 2 Nephtys australiensis 7 4 Halicarcinus australis 5 4 Phylum Nemertinea 4 4 Marphysa sanguinea 3 3 Australonereis ehlersi 2 1 Conuber conica 2 2 F. Magelonidae 1 1 F. Pilargidae 1 1 Halicarcinus sp. 1 1 Bedeva hanleyi 1 1 17

Figure 8. - Sampling areas in Tuggerah Lakes where Nassarius jonasi was present • , not present o . 18

3 Km.

Figure 9. - Areas in Tuggerah Lakes where the mussel

Xenostrobus seouris was present • , not present o . 19

3 Km.

Figure 10. - Sampling areas in Tuggerah LaJces where the

polychaete Owenia fusiformis was present • , not present o 20

Figure 11. - Sampling areas in Tuggerah Lakes where the polychaete Nereis (Hediste) diversicolor was present • , not present o 21

3 Km.

Figure 12. - Sampling areas in Tuggerah Lakes where the bivalve Maooma deltoidalis was present • , not present o . 22

Figure 13. - Sampling areas in Tuggerah Lakes where members of the Family Capitellidae were found to be present • , not present O . 23

B. Results of Computer Classification

The dendrogram of site classification is presented in Figure 14. Four ecologically meaningful site groups could be established in the upper levels of the hierarchy. These site groups are topographically illustrated in Figure 15. Following is a description of each of these site groups.

Site Group 1 - The unifying species in this group is the tube dwelling polychaete Owenia fusiformis. All sites are located in areas with weed growing in muddy sand. All three species of weed are found in this group. Site Group 2 - The sites in this group all possess the bivalve Theora fragilis and are all non-weed, mud sites. Site Group 3 - These sites all possess the bivalve Macoma deltoidalis. They include sites with a weed and mud substrate and several sites with a mud substrate that are located near weed. Site Group 4 - Prominent in this group are sites with a sand substrate. Also present are sites with a weed and sand substrate.

Noticeable from the above results is that the fauna of different weed species is not separated in the classification.

It may be deduced then, that four important ecological zones exist in Tuggerah Lakes. These are mud, sand, weed on muddy sand, and weed on mud.

C. Descriptions of Fauna of Different Zones i. The Mud Zone The mud zone comprises 60% of the lake's substrate. The faunal diversity in this zone is very low with an average of 24 25

|| || Site Group 1.

[■—-| Site Group

Site Group 3.

| | Undetermined.

Figure 15. - Distribution of site groups in Tuggerah Lakes. One site group (4) has been omitted to present a simpler picture. 26

4.3 species per sampling site being recorded. The detrital

feeding bivalve, Theora fragilis, is by far the dominant

species of this zone. It comprises over 50% of the

individuals in 75% of the sites sampled. The remaining sites were dominated jointly by Theora sp. and the bivalve

Notospisula trigonella. Other species to occur frequently but in very low numbers include the bivalve, Maooma

deltoidalis and the isopod Mesanthu^a sp.

ii. The Sand Zone

This zone occurs only in small patches throughout the lakes. It is primarily found in the southern parts of

Munmorah Lake, outside Wallarah Creek in Budgewoi Lake and near "The Entrance" in Tuggerah Lake. The diversity is again very low with an average of 5.2 species recorded per site.

The bivalve, Sanguinolaria onuphia, is clearly dominant in over half the sites and is present in all but one of the sites sampled. The only site not to contain Sanguinolaria sp. was located near "The Entrance" where the gastropod

Nassarius gonasi and the polychaete, Haploscopolos simplex, were dominant.

iii. The Weed Zones

The composition of the fauna of these zones is much less uniform over the sites sampled than those areas mentioned above. The diversity of the fauna from the weed areas is variable but generally exceeds that of the sand or mud zones.

The species number varies from zero to eleven species. 27

Plate 2. - Owenia fusiformis in it's sandy tube.

Plate 3. - Nereis diversi color. 28

1. Weed on Muddy Sand - This zone is characterized by the presence of Owenia fusiformis (Plate 2). Isoplethes drawn for the abundance of this species (Figure 16) reveal that it occurs in most abundance outside Wyong, Ourimbah and Wallarah Creeks as well as the Munmorah Power Station Inlet area. All these areas are subject to a great deal of water movement and have large areas of muddy sand sediment. Both these factors would aid this species since it is a tube­ dwelling (sandy tube) filter feeder.

2. Weed on Mud - This substrate is primarily found in

Tuggerah Lake. The fauna is dominated by the deposit feeding polychaete, Nereis (Hediste) diversicolor (Plate 3). As can be seen from a comparison of the distribution of Nereis and

Owenia (Figure 16)^ these two species rarely occur together.

Presumably, the fine silty mud is not suitable for Owenia to build its sandy tube or to feed, whereas Nereis, being a detrital feeder, does not find these conditions disadvantageous.

iv. Sites of Particular Interest

1. The Entrance - The fauna of this area was markedly different from that of the rest of the lake. Unique to this area are the polychaete Australonereis ehlersi, and a large number of Hermit crabs. Samples taken from Zostera sp. contain very large numbers of Nassarius jonasi.

2. Empty Sites - Two sites in the survey had no fauna present - sites 33 and 44. Both contained Ruppia sp. growing on very fine silt. Both areas were situated away from any currents, in very sheltered areas. 29

Figure 16. - Isoplethes for the abundance of Owenia fusiformis (—) and Nereis (Hediste)diversigo lor (---). 30

3.4 DISCUSSION

This survey provides the first faunal list for Tuggerah Lakes. It is clear from the analysis of the site/species data that the substrate is an important factor controlling the distribution of species. That faunal assemblages are related to particular substrates has been substantiated by many other workers. Lie (1968) found that the nature of the substrate was the most important factor governing the differences between faunal assemblages. Nicoles (1970) found that the clay content of the sediment was the controlling factor governing species composition. A number of workers have found that the fauna inhabiting sediments with a high clay and silt content is dominated by deposit feeders, the filter feeders living in more consolidated areas (Young and Rhoads, 1971; Driscoll and Brandon, 1973). The distribution of fauna in Tuggerah Lakes certainly seems to be in agreement with these findings. The mud areas are dominated by such deposit feeders as Theora fragilis, Macoma deltoidalis, Nereis diversicolor and polychaetes of the Family Capitellidae. The more consolidated sand areas are host to the filter feeders

Owenia fusiformis and Xenostrobus securis.

Clearly, the relatively small number of samples taken per site is a limiting factor in the study of community structure. Chapter 4 describes a more quantitative study in which this aspect of the benthic populations is studied in more detail. 31

CHAPTER 4

QUANTITATIVE SURVEY

4.1 INTRODUCTION The Preliminary Survey, discussed in Chapter 3, outlined the existence of four distinct faunal zones in Tuggerah Lakes. It is the aim of this study to establish the faunal similarity between and within these zones. This was done by incorporating the numbers of each species present at each site.

4.2 METHODS A. Field Methods The field and laboratory methods employed were the same as for the Preliminary Survey except that five cores were taken at each site. Sampling took place in July and again in December, 1974. These periods represented winter and summer respectively. Nineteen sites were sampled in winter.

The positions of these sites are shown in Figure 17. Table 3 gives a description of the environment of each of the sites. It was hoped that all these sites could also be sampled in summer but owing to a large fall in the lake level, sites 9, 6 and /2could not be sampled. It must also be noted that two sites sampled in summer had different substrates to that sampled in winter. Site 1 in winter had Halophila roots in sand but by summer the roots had degraded and only sand remained. Site 4 which in winter had zostera in a sand/mud sediment, by summer, due to sand movements, consisted of Zostera in sand. 32

Figure 17. - Sampling sites for quantitative survey. 33

TABLE 3

DESCRIPTION OF SITES SAMPLED IN THE QUANTITATIVE SURVEYS

DESCRIPTION

Ealophila roots in sand

2 Zostera in gravel/sand/mud

3 Mud

4 Zostera in muddy sand

5 Mud with dead or dying weed

6 Zostera, very sparse, in mud

7 Zostera in muddy sand

8 Mud

9 Ealophila roots in sand

10 Mud

11 Ruppia in mud

12 Ruppia in sandy mud

13 Zostera in muddy sand

14 Mud

15 Zostera in sand

16 Zostera in mud

17 Zostera in muddy sand

18 Zostera in muddy sand

19 Ruppia and Zostera in muddy sand 34

B. Hydrology

Using a Hamon Temperature-Salinity Bridge, salinity and temperature profiles were recorded at each site during both

the summer and winter surveys.

C. Sediments

During the winter sampling period an extra core of

sediment was taken from sites in the mud zone. This sediment was not sieved but left untreated. It was later used to determine the silt and clay content of the mud zone. The Hydrometer method for particle size analysis as outlined by Milner (1962) was used. The actual laboratory work was carried out by Ground Test Pty. Ltd.

D. Species/Site Analysis i. Faunal Similarity The degree of faunal similarity between sampling sites was established by using the C.S.I.R.O. computer program designated as "MULCLAS". This program incorporates the Canberra Metric and the Group Average Sorting Strategy. Both of these measures are discussed in detail in Appendix B. In short, the numbers of each species at each of the sites are compared and sites are grouped together when composition and numbers of species is very similar. This is termed a Polythetic method of classification as opposed to the

Monothetic procedure used in the Preliminary Survey which bases its groupings on the presence or absence of species.

ii. Faunal Composition and Dominance Benthic communities are often characterized by the dominant species present. For the purposes of this survey, 35

the fauna of areas that have low diversity and show no

dominance hierarchy are discussed in terms of species present

and the abundance of those species. The fauna of the more

diverse areas is discussed in terms of their dominant species.

These species are defined simply as the five most abundant

species on the community.

4.3 RESULTS AND DISCUSSION

4.31 Faunal Similarity

i. Winter Survey

The dendrogram of site classification is given in

Figure 18. Four site groupings were found as well as a number of sites that remained ungrouped. The dendrogram shows the ungrouped sites leaving the hierarchy at a very high level indicating that the fauna at these sites was very different to that found in the former groupings. The site groupings are topographically illustrated in Figure 19.

Site Group 1 - This group consists of sites 1 and 9 which are unique in having a Ealophila roots in sand substrate.

Site Group 2 - The group contains sites 3, 8, 10 and 14 all of which are areas that contain a mud substrate.

Site Group 3 - This consists of sites 2, 4, 13 and 18; all contain a substrate of Zostera in muddy sand.

Site Group 4 - This consists of sites 5, 11 and 12, the latter two sites having Ruppia growing in a mud sediment.

Ungrouped Sites

a) Site 15 - This site is located in the channel that connects Tuggerah Lake to the Ocean. 36 sampling.

winter for groupings site of

Dendrogram

-

18.

Figure 37

Figure 19. - Site groups and ungrouped sites produced by the MULCLAS analysis of the winter data. 38

b) Site 16 - This is the only site sampled that

contained Zostera growing in mud.

c) Site 19 - This site, located near Long Jetty,

contained a mixture of Ruppia and Zostera.

d) Site 17 - This site, located at the mouth of

Wyong Creek, consisted of Zostera in muddy sand.

e) Site 6 - This site consisted of dying Zostera in mud.

f) Site 7 - This site consisted of Zostera in muddy sand and was situated in the path of a warm water current generated by Munmorah Power Station.

ii. Summer Survey

The dendrogram of site classification is presented in

Figure 20. The site groupings are topographically illustrated in Figure 21. Only two groups could be established from the analysis of the summer data. This is possibly due to the fact that only sixteen sites were sampled and that some of these sites had changed in the nature of their substrate.

This prevented the equivalents of winter site groups 1 and 4 from forming. However there were groupings that were very similar to those of the winter survey.

Site Group 1 - This was a very large group consisting of sites 1, 2, 3, 8, 10, 11 and 14. With the exception of sites 2 and 11, all other sites consisted of areas containing a mud substrate. Site 2 consisted of Zostera in gravel/muddy sand and site 11 consisted of Ruppia in mud.

Site Group 2 - This group consists of sites 13, 17 and

18 all of which contain Zostera growing in muddy sand. 39

Figure 20. - The dendrogram of site groups and ungrouped sites generated from the MULCLAS analysis of the summer data. 40

Figure 21. - Site groups and ungrouped sites produced by the MULCLAS analysis of the summer data. 41

Ungrouped Sites - Consistent with the winter ungrouped

sites are sites 15 (Zostera growing in the channel), 16

{Zostera growing in mud), 19 (Zostera and Ruppia growing in

muddy sand near Long Jetty), and site 7 (located in the path

of the Power Station discharge). Peculiar to the summer study

are the ungrouped sites 4 and 5. As mentioned earlier, site

4 had undergone sedimentary changes since the winter sampling, which may account for the non-grouping of this site. Site 5

is located in the channel connecting Budgewoi Lake to Munmorah

Lake. Through this channel flows the current generated by

the Munmorah Power Station. This current periodically brings with it large amounts of weed debris from the weed beds

located in its path in Budgewoi Lake. Consequently, the area U.s is continually changing and may account for the site not being grouped with other areas.

iii. General Trends

When viewed together the results of the Winter and

Summer Surveys present a definite picture of the relationships between the various benthic communities in Tuggerah Lakes.

The most noticeable feature is the delineation of faunal groups on the basis of substrate. This follows the pattern established in the Preliminary Survey. The fact that nearly all sites within one substrate type are grouped together, even at the numerical level, points out the apparent homogeneity of the fauna in substrate areas. The fauna of all mud areas sampled have been grouped together, establishing that the faunal composition of the mud zone does not vary throughout the three lakes. The other very predominant substrate, Zostera in muddy sand, also shows that the fauna 42

Sites

Figure 22. - The number of species found at each site containing a mud substrate in winter (X—x) and summer ( • I ) .

Sites

Figure 23. - The number of individuals found per 5 cores at each "mud" site in winter (X—X) and summer (•—• ). 43

is very homogeneous with only one site consistently not being grouped with all other sites containing the substrate. The grouping of sites containing Ruppia indicates that the fauna associated with this weed is different to that found in Zostera. Areas that were found throughout both surveys to contain fauna pe culiar to particular sites were: site 16, the only site sampled that contained Zostera in mud; site 15, the site containing Zostera located in the channel near "The Entrance"; site 19, an area containing a mixture of Zostera and Ruppia, and site 7, the area containing Zostera located near Munmorah Power Station. To understand more fully why these divisions have been made, the dominant species and population structure of the fauna of the abovementioned areas will be discussed.

4.32 Community Structure of Site Groups 1. The Mud Zone The number of species and number of individuals found at each of the sites containing a mud substrate are presented in Figures 22 and 23. Pooling the results of all the samples together, the average number of species found per five cores is 8, the average number of individuals, 16. In no area in the mud zone do the numbers of animals recovered give any indication of dominant species. This is in marked contrast to the findings of the Preliminary Survey where the bivalve

Theora fragilis was clearly the dominant species. The reason for this marked change in faunal composition is probably the severe flood that occurred between the two sampling periods of March and July. Chapter 5 deals with the effect of this flood in more detail. 44

P e r c e n ta Composition g e 100 20 30- 40- 50- 90- 10 60- 70- 80- •0001 of Figure < - - — -

----- sites CLAY

24.

3

------

- (°

— •001 Particle o

) ->

, ^

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size (

SILT x —

*

Size structure ) and

in

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sediment

j 1 > 45

The species that were found throughout the mud areas include the bivalve Maooma deltoidalis , the polychaetes Notomastus hemipodus and Ancistrosyllis sp., the isopod

Mesanthura sp., and the bivalve Notospisula trigonella.

Notospisula was the only suspension feeding animal recovered from the mud zone.

It has been established by Sanders (1956) that sediment with a high percentage of silts and clays supports only small numbers of species and individuals. He found that the optimal range for the greatest diversity was 13-25% of silts and clays. Larcombe (1974) points out that many estuarine lake systems are subject to siltation resulting in a predominantly silt/clay substrate. The result of this is low numbers of species and individuals. According to Higginson (1971) the central areas of Tuggerah Lakes had, fifty years ago, a sandy substratum. However, due to erosion and urbanisation of the foreshores, this has changed to a predominantly clay/silt substrate. In the light of these findings a closer examination of the sediment of the mud zone may aid in explaining the relative lack of animal life.

Figure 24 gives the particle size structures of sediments from sites 3, 10 and 14. They all show that the sediment is composed primarily of clay and silts, with their proportions ranging from 78 to 95% of the total sediment. These values far exceed Sanders' optimum range of 13-25% of clay and silts for benthic diversity. Noticeable in the sediment are large numbers of dead Notospisula shells. Sixteen percent of the dry weight of sediment from site 14 consisted is

turbidity

high

where

water

deep

in

encountered. taken

being

core

< I

•p0) rd i—I fii 47

of these shells alone.

Diving observations in the mud zone revealed that, as would be expected, the very fine particles of silt are deposited in the top layer of the sediment. Any slight movement above this silt causes it to be resuspended in the overlying water - the visibility being reduced to near zero.

Plate 4 illustrates the very turbid conditions encountered when taking a core. The apparent ease of resuspension of the fine silt coupled with the relatively shallow depths of the lakes would cause resuspension to occur when wave action was high. This high turbidity may account for the very few suspension feeding animals found in the area. The fine particles would tend to clog their filtering mechanisms. The unstable nature of the substrate would also tend to prevent the settling out of any animal that requires a solid medium within which to form burrows.

2 . Zosteva Communities The number of species found at sites containing Zostera varied from 10 to 20 species. Figure 25 gives the number of species found at each site during summer and winter. The number of individuals recovered from five cores varied from 116 to 917. Figure 26 gives the total number of individuals found at each site for the two sampling periods. This figure shows that the total number of individuals found at site 17 (Wyong Creek) is much greater than the total number of individuals found at any other sampling site. Closer examination of the faunal constituents of the community at

Wyong Creek reveal that in the Winter Survey the large population is due to a number of species. Figure 27 illustrates 48

Sites Figure 25. - The number of species found at sites containing Zostera in winter (X—X) anc^ summer (•—• ).

Sites Figure 26. - The number of individuals found at sites containing Zostera in winter (X—X) an^ summer (•—#). 260r - - -

CM t 2 ■H CO ■P (D U)

Figure 27. - The number of individuals of the species Owenia fusiformis (o —o) , 49 Melita sp. <*-*> and F. Oedicerotidae (<_* ) at each Zcetera site during winter. 50

this point in giving the abundance of the polychaete Owenia fusiformis and the amphipods Melita sp. and the Family

Oedicerotidae at all sites containing Zostera. In summer

the large population at Wyong Creek is predominantly due to

the 703 individuals of Xenostrobus securis found there.

Figure 25 shows that of all the sites sampled, the Wyong

Creek area has the greatest number of species in both winter and summer. The large number of species and individuals outside Wyong Creek may be due to the effluent from a sewerage treatment works that is situated on the banks of Wyong Creek.

The effluent may supply a level of nutrients that promotes a large population of benthic animals.

The most variable factor between Zostera sites is the species that characterize them. Table 4 gives the dominant species at each site containing Zostera. Each site-group generated by the MULCLAS analysis will be discussed in terms of these species.

A. Fauna Associated with Zostera in Muddy Sand

All sites containing a muddy sand sediment, with the exception of site 7, were grouped together in the MULCLAS analysis. As seen from Table 4 they all have in common certain dominant species. Predominant is the mussel

Xenostrobus securis , the isopod Mesanthura sp. and the amphipods Melita sp. and Family Oedicerotidae. However, separating sites 16, 17 and 18 from sites 2 and 4 is the presence in the former group of large numbers of the polychaete

Owenia fusiformis. The rather large populations found at site 17 (Wyong Creek) have been discussed in the preceding section. X W E-i Q o 2 P < E- CO p CJ z w 1 co w a. co a w E-i co sz; < H i rn CO — E-i U O Z H < — Z i C h Z Co Q — 1X1 o Pi i OJ CO § s W Pi E fei § a? Q — t z H m Pi — — h D h t i i i l 1 1 w 2: E-i Pi — co QJ is. s n Pi 1 CO i E-i w — co p CJ w 1 w co — o\o p CO w u i w co — i 1 i <

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51 TABLE 4 C o n t. E- ( w CO CO Cft w u 1 w co — o\° — co 1 w u w CO P — h 1 h 1 1 % § 2: & Q u w < z ABUNDANCE •ft •ft •c~3 £5 o to fti *ft •ft ft4 Eft « CO CO ^ co Pi C0V O to s o 03 a co Pi co S «v 03 so CO CO ft

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52 53

Site 7 was the only site containing Zostera in muddy sand that was consistently ungrouped. The area represented by site 7 is situated in the path of an artificial warm water current produced by Munmorah Power Station. The chief effects of this upon the fauna would firstly be to subject it to a continual current and secondly, subject it to temperatures that exceed normal lake temperatures. The temperatures recorded above the sediment were up to 4°C higher than areas outside the influence of the current

(Appendix D). The benthic fauna is characterized by the presence of the gastropod Velacumantis australis. This animal appears as the most abundant species in winter and ranks second to Xenostrobus in summer. At no other site does

Velacumantis appear in such large numbers. It would appear that the discharge from Munmorah Power Station provides conditions that are preferred by Velacumantis.

B. Fauna Associated with Zostera in Mud

Site 16 was the only site with a Zostera/mud substrate to be sampled. The MULCLAS analysis of both summer and winter fauna consistently separated this site from the mass of others very early in the dendrogram. This implies that a very dissimilar fauna existed at this site when compared to the rest of the lake. The dominant species found at this site bear this out (Table 4). Such species as the deposit feeding polychaetes, Nereis diversicolor and Nephtys australiensis, characterize the site. Noticeable by their absence are the many suspension feeders, such as Owenia fusiformis and

Xenostrobus securis that characterize the more sandy substrates. 54

C. Fauna from Zostera near "The Entrance"

In both summer and winter classifications site 15, located in the channel connecting the lake to the ocean, separated off at a very high level in the dendrograms. Many of the species found in this area were not found at any other site. These include the gastropod Austroeoclea constriota and an unidentified Hermit crab. Animals that were found in large numbers at this site were only found in very low numbers in the rest of the lake system. These included the polychaetes Haploscopolos simplex and Nephtys austv aliens is and the prawn Macrobraohium sp. The close proximity of this area to the ocean and the high salinities recorded there (up to 30°/oo) (Hodgson, 1975, personal communication) may explain the very different species composition at this site.

D. Seasonal Variation in Fauna of Zostera Beds Table 4 shows that over the six month period, July- December, the species composition at each site remained relatively constant. However, there were some major changes in species abundance. Xenostrobus caused a marked change in the order of dominance at sites 7, 13 and 17 in December. Its numbers increased so that it became the most abundant species at those sites. This is probably due to the fact that Xenostrobus has its major spawning period around October (Bayliss, 1973). By December the new generation of mussels would have been sampled.

The polychaete Nephtys australiensis, low ranked in abundance at sites 15 and 16 in July, became top ranked at site 15 and ranked third at site 16 in December. The 55

abundance of amphipods of the Family Oedicerotidae decreased

in abundance at sites 2, 17, 18 and 19, and increased its

abundance at site 4 from July to December.

The only site to drastically change its faunal

composition over the period was site 16 where only the polychaete Nereis diversieolor remained in the top five

ranking species from July to December.

3. Fauna Associated with Ruppia Beds

Sites sampled that contained Ruppia were sites 11 and

12. Site 12 was located in Tuggerah Lake. The sediment consisted of a sand/mud mixture with fine silt comprising a top layer. A total of 8 species and 66 individuals were found at this site. Clearly dominant was the amphipod species of the Family Eusiridae, comprising 73% of the individuals.

Site 11 was located in a very protected area of Budgewoi

Lake. The sediment consisted almost entirely of mud. This site was situated in the same position as site 33 of the

Preliminary Survey which at that time was completely devoid of macroscopic life. In July, however, the sampling yielded

21 individuals and 6 species. No species occurred in large enough numbers to establish any dominance trends. Present were the amphipods Paraphoxus sp. and Melita sp., the mussel

Xenostrobus securis and the polychaete Nereis diversieolor.

The December samples at this site yielded quite different faunal components. Five species and 116 individuals were found with Nereis diversieolor accounting for 108 of the individuals.

In the light of the abovementioned results it would appear that Ruppia can support only small populations of 56

benthic animals. A lack of stability in the fauna is reflected in the unpredictable nature of the species compos ition.

4. Fauna in a Mixed Zostera/Ruppia Area

Site 19 was situated near Long Jetty and was comprised of an area where Zostera and Ruppia were growing intermixed. The MULCLAS analysis indicated that the faunal composition of this site was unlike that of any other site. This can be explained when the dominant species are examined (Table

5). At no other site do the polychaete Nereis diversieolor and the mussel Xenostrobus securis occur together in large numbers. The reason for this mixture of fauna must be associated with the mixture of weed species and their sedimentary requirements. Ruppia requires a layer of silt in which to grow, whereas Zostera does not have this requirement (Higginson, 1965) . It is possible that the area represented by site 19 consists of patches of muddy sand and mud; the two faunal groups occurring next to each other.

4.33 Comparisons with Fauna of Lake Macquarie According to studies conducted in Europe by Remane and

Schlieper (1971), the number of species found in brackish lakes is much less than the number found in fully marine environments. This is attributed to the fact that the salinity regimes in brackish environments are not stable enough to support a large number of species. It is, therefore, of considerable interest to compare the fauna of Tuggerah Lakes with the fauna of a marine lake. Comparisons such as these are hampered due to the variety of methods used in TABLE 5

DOMINANT SPECIES PRESENT AT SITE 19 DURING SUMMER AND WINTER

WINTER SUMMER

Percentage Percentage Species Species Abundance Abundance

Nereis diversicolor 28 Nereis 41 diversicolor

Xenostrobus 21 Mesanthura sp. 15 securis

Mesanthura sp. 14 Xenostrobus 14 securis

Melita sp. 9 Haploscoplos 11 simp lex

F. Oedicerotidae 8 Laternula 4 tasmanica 58

benthic studies and also due to the lack of benthic work in

Australia. For these reasons a small but quantitative survey was carried out in Lake Macquarie, a marine lake situated two kilometres north of Tuggerah Lakes. The physical and chemical characteristics of the lake have been discussed in Chapter 2. The benthic fauna of Lake Macquarie has previously been studied by MacIntyre (1959) but this was a very broad survey and not suitable for quantitative comparisons.

1. Sites Sampled

The two sites sampled were located in Myuna Bay. This area was chosen because it was the site proposed for a power station. The results of the study serve not only to enable faunal comparisons with Tuggerah Lakes but will allow future workers to assess the effect of the power station upon the benthic fauna. The locations of the sites are given in Figure 28. These sites were sampled in July, at the same time as the Tuggerah Lakes Winter Survey was being conducted. Sampling methods were the same as those described for the Tuggerah quantitative studies. Salinity measurements of the water immediately above the sediment were recorded at each site using a Hamon Temperature-Salinity Bridge. Table 6 presents the salinity and sedimentary characteristics of the sites.

2. Results and Discussion

The species composition of sites 1 and 2 are presented in Table 7. A total of 9 species and 37 individuals were found at site 1, both of which exceed the species/individual 59

Whitehead Lagoon

Goonda

Rocky

Figure 28. - Location of sampling sites in Myuna Bay.

TABLE 6

DESCRIPTIONS OF SAMPLING SITES IN MYUNA BAY.

SITE DEPTH (m) WEED SEDIMENT SALINITY( ^)

1 8 None Mud 34.3

2 2 Zostera Gravel/Muddy 33.0 Sand 60

TABLE 7

SPECIES COMPOSITION AT SITES 1 AND 2 IN MYUNA BAY

SITE SPECIES ABUNDANCE PER 5 CORES

1 Maldane sarsi Malmgren 15

Nereis (Hediste) diversicolor O.F.Muller 6

Lumbrinereis latrelli Audouin and Milne 4 Edwards Magelona sp. 1

Ancistrosyllis sp. 2

Armandia intermedia Fauvel 3

Marphysa sanguinea Montague 2

Corophium sp. 2

Ishyrocerus sp. 2

2 Owenia fusiformis della Chiaje 36

Nassarius gonasi Dunker 22

Velacumantis australis Quoy § Gaimard 16

Anadara trope zia Deshays 9

Species 1 7

Macoma deltoidalis Deshays 2

Notomastus hemipodus Hartman 2

F. Aphroditidae 1

Terebellides stroemi Sars 1

Tapes sp. 1

Walluncia assimilis Iredale 1

F. Spionidae 1

Corophium sp. 1

Species 2 1 61

values for the mud zone in Tuggerah Lakes. The majority of species found at site 1 were different to those found in Tuggerah Lakes. The polychaete Maldane sarsi was the most abundant species at site 1. The dominance of Maldane in the mud zone of Lake Macquarie was reported by MacIntyre in 1959. Also present at site 1, but not found in Tuggerah Lakes, are the amphipods Corophium sp. and Ishyrocerus sp. The mud area of site 1 contained a relatively large number of Nereis diversieolor. This is in contrast to Tuggerah Lakes where

Nereis was found exclusively in weed beds.

Site 2 had a very different benthic fauna to that of site 1. Present were 7 species of molluscs, 5 of which are not found in Tuggerah Lakes. These include Anadara trapezia, Walluncia assimilis and Tapes sp. Occurring in relatively large numbers were the polychaete Owenia fusiformis and the gastropods Nassarius jonasi and Velacumantis australis all of which are common in Tuggerah Lakes. A direct comparison of species number and abundance of site 2 with those of Zostera sites in Tuggerah Lakes is not possible as such a rocky substrate is not found in Tuggerah Lakes. Site 2 is situated in what MacIntyre (1959) termed the slope zone. This is a zone that is intermediate between the weed and mud zones of Lake Macquarie. Tuggerah Lakes, probably because of its shallow nature and lack of rocky headlands, does not have areas comparable to the slope zone. 62

A 5 6 7 8 9 10 11 12 1 234 5678 Months

Figure 29. - Salinity levels recorded by the

Electricity Commission of N.S.W. at substrate level at site 3 for the period 4/74 to 12/75. 63

CHAPTER 5

THE EFFECT OF A SEVERE FLOOD UPON THE BENTHOS

5.1 GENERAL EFFECTS Prolonged exposure to low salinities reduces the diversity of marine and estuarine benthic fauna. Andrews

(1972) recorded unprecedented changes in the distribution and abundance of estuarine biota in Chesapeake Bay after a tropical cyclone exposed the fauna to low salinities. Pearce

(1974) points out that sessile or attached invertebrates may be affected for many decades after flooding. Severe flooding of the Tuggerah Lakes area occurred during May and June 1974. This resulted in a substantial fall in salinity levels (Figure 29) which had a number of effects upon the ecology of the lakes. The first of these was the death of the weed Halophila sp. which, up until the time of the flood, had been growing throughout the lakes. Secondly, Munmorah Lake, which experienced the lowest salinities (Appendix D) because of its distance from the ocean channel, was the site for a massive fish kill. This was attributed to the low salinities in the lake (Bebbington, 1974). Accompanying the rain was a severe storm with very high wind velocities. This resulted in the devastation of certain areas of Zosteva and Ruppia. These changes prompted a study of the effects of the storm and flood upon the benthos. The study was incorporated in the quantitative surveys outlined in Chapter 4. However, extra samples were taken in September. The September samples 64

were taken to see if any recolonisation of the fauna had occurred. The sites sampled were 3, 7, 10, 14, 16, 17 and 18. All corresponded to sites sampled in the quantitative surveys. The species composition of these sites is given in Appendix C. To assess any damage to the benthos, the results of the

March Preliminary Survey were used to establish the species composition of the sites before the flood. Table 8 presents the three most abundant species at the seven sites for March, July and September. It points out one obvious feature - that the dominant species, Theora fragilis, found in mud areas in

March is not found in comparable numbers after the flood. In fact, throughout the July and September sampling periods, only one individual of Theora was found alive. The effect of the mass death of Theora upon the total number of individuals found at mud sites 3 and 10 is illustrated in Figure 30. As shown, there is a marked reduction in the numbers of benthic individuals after the flood. The fauna of the weed sites 7, 16, 17 and 18 showed no similar dramatic changes.

5.2 THE HALOPHILA COMMUNITY

The death of the weed Halophila sp. took place over a period of three to four months. By July, remnants of the weed still remained with the root system still intact. However, by December no remains of the weed were found. This gradual reduction in the biomass of the weed is accompanied with a reduction in the number of species and total number of individuals found. The following table presents the species THE THREE MOST ABUNDANT SPECIES PRESENT DURING MARCH, JULY AND SEPTEMBER AT THE SEVEN STATIONS USED TO ASSESS THE MAY-JUNE FLOOD CO H H 1 z < o — 2 < pc; u K p h co w P W 2 m H PQ 4 P h r-3 CO *3 *3 'K+i &H *3 •3 p 3 *3 a 3 a co *^> V P5 co CO a a 3 CO 3 P 3 a CO a CO CO a 3 CO 3 3 P CO P

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•

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*3 fti *3 P in P P P *3 3; 03 3 O in 3 CO S3, p, O OP 03 03 CO 3 03 3 co o O 3 03 • .

fti •H P W *H 3 in P P P P O H 3 to S in P P p h . • h •3 *3 X5 •3 fe; •3 *3 *3 4~» O^U *3 *3 •3 ^ P 3 e 3 P O P p 3 P P O 3 3 P 3 P P 3 3 O g P 3 P 3 P *-» P O 3 g co

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4^ ^ *3 4i 4i •3 O g O P P ^ 4i P P 3 g p S^,*3 O p n 3 p, P Pfl P 3 O P P 3 3 P co P P 3 p 3 •

3•3 •3 •3 <+-, 0 O •H •rH nd T5 P •H O ■p •H T3 3 p 3 p p 0 g 3 3 p p u P p +-> 0 P aj P 0 p rt p 0 p h • • h •3 *3 '*-» 03 rP •3 Pj 44 to •3 3 ^ P p 3 P 3 p 3 g P P P 3 O P 3 o 3 P P P p P 3 in P 3 P P

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•

*3 P-, W 'H X5 ^ 4^ -rH 4^> r3 CL, O g p O P S3. P p p 1/) p 3 P Oj g P 3 in p. 3 a. P P O 3 p H • • 65 site during Figure Number of Individuals Per Core

10

March, 30. (o

— - o

The )

July .

number

and MARCH

September of

individuals Month

at

JULY site

per

3

core (• — •

SEPTEMBER

found )

and

66 68

number and total number of individuals per core at site 1 (a Haloiphila in sand site) for the months of March, July and December.

MARCH JULY DECEMBER

Species 10 7 5

Individuals 49 29 13

5.3 FAUNA OUTSIDE OURIMBAH CREEK

Scuba divers near the mouth of Ourimbah Creek during September encountered unusual conditions. The bottom sediment was covered with leaf-litter, logs, branches and articles of human garbage - all washed down from the creek. The leaf litter and debris illustrated in Plate 5 was several centimetres thick throughout the area. Table 9 gives the three top ranking species found outside

Ourimbah Creek for the months July, September and December. The sedentary filter feeders, Xenostrobus seeuris and Owenia fusif ormis together, comprised over half the total population in July. However, by September the population structure had changed completely. Both Owenia and Xenostrobus were absent.

Instead, the amphipods, Melita sp. and the Family

Oedicerotidae were the most abundant species. This change in species composition is very likely to be associated with the carpet of debris found at the sampling site. Presumably, species like Owenia that are attached to the substrate, could not escape the debris and hence were killed off, whereas the amphipods, which are very mobile animals, would not be trapped.

By December the area was free of debris and both Owenia and 67

Plate 5. - Leaf litter and debris found outside Ourimbah Creek TABLE 9 THE THREE MOST ABUNDANT SPECIES FOUND NEAR OURIMBAH CREEK DURING JULY, SEPTEMBER AND DECEMBER

JULY SEPTEMBER DECEMBER

Xenostrobus securis Melita sp. Xenostrobus securis

Owenia fusiformis F. Oedicerotidae Owenia fusiformis

F. Eusiridae Paraphoxus sp. Notospisula trigone Ha 70

Xenostrobus were back to their previous abundance levels. 71

Plate 6 Weed growth in Budgewoi Lake 72

CHAPTER 6 THE EFFECT OF WEED CLEARING OPERATIONS UPON THE BENTHOS

6.1 INTRODUCTION

In many lake systems throughout the world increases in cultural eutrophication have led to excessive growths of submerged angiosperms. These growths severely limit man's use of the lake as a fishing, boating and recreational area.

Consequently, attempts have been made to clear the weed from these lakes. The rationale behind this is that it serves in the short term to "mow the lawn" and in the long term to place sufficient stress on the plant so that it will die or a more desirable species will take over. Three weed species occur in Tuggerah Lakes. They are

Zostera capricorni Ashers, Ruppia spiralis Dumort and

Halophila sp. Ruppia and Zostera are thin leafed plants, Ruppia growing up to 2 metres in length. Halophila is a broad leafed plant that grows only a few centimetres in height. It is the physical characters of Ruppia and Zostera that make them the plants that cause concern to residents and tourists. Higginson (1971) states that these plants have grown to excess in Tuggerah Lakes due to the eutro­ phication of the area. He also points out other consequences of their growth, in that plants accumulate in large quantities on the shore after they have died. This gives rise to organic sludges and unpleasant odours. Plate 6 illustrates the growth of weed in Budgewoi Lake. Plate 7 The weed clearer in operation 74

Wyong Council, in an attempt to alleviate the weed problem in Tuggerah Lakes, proposed to rake areas of weed in the lakes. Previous chapters in this thesis have discussed the importance of the weed zones in the lakes as habitats for a wide diversity of benthic fauna. There was, consequently, concern regarding the effect a mechanical harvester would have, not only on weed growth but upon the benthic fauna living in and near the weed. A pilot study was arranged with

Wyong Council to assess the possible effect that a large scale weed clearing operation would have upon the benthic fauna.

6.2 METHODS An area of approximately 40 square metres located near the foreshores of Long Jetty in Tuggerah Lake was chosen to be the test site. Growing intermixed in the area was Ruppia and Zostera. Ten core samples were taken randomly throughout the area before the clearing commenced. The sampling and sorting procedures were the same as those outlined previously

(Chapter 4). Two weeks after the clearing operation another ten samples were taken in the same manner. The harvester consisted of a bulldozer with a large rake fitted on the front. It proceeded by working from the lakeside of the test plot into the shore. The weed and mud collected t - deposited on shore. Pate 7 illustrates the bulldozer in operation.

6.3 RESULTS AND DISCUSSION Table 10 gives the species’ composition and Table 11 the total number of species and individuals, found before and 75

after the weed clearing operation. They show that the weed clearing greatly reduced the number of species and total number of individuals living in the test plot. It would appear that any large scale weed clearing would severely deplete the benthic fauna in the weed zones.

The significance of such a reduction in the size of benthic populations would be reflected by the fishing industry. Current investigations by the N.S.W. State

Fisheries show that in Tuggerah Lakes Nereis diversicolor is the basic food for Whiting, while Notospisula trigonella is commonly found in the gut of Bream. The mussel

Xenos trobus securis figures prominantly in the diet of a wide variety of the commercial fish species found in Tuggerah

Lakes (Henry, per. comm.). All these benthic species were greatly reduced in abundance by the weed clearing and if carried out on a large scale the clearing would probably lead to reduced fish populations. 76

TABLE 10

SPECIES COMPOSITION OF TEST SITE BEFORE AND AFTER WEED CLEARING SPECIES ABUNDANCE BEFORE AFTER

Nereis diversicolor 412 156

Armandia intermedia 10 0

Marphysa sanguinea 4 0

Haplos eopolo s simplex 73 23

Notomastus hemipodus 5 0

Mysella sp. 110 84

Xenostrobus securis 19 0

Macoma deltoidalis 5 0

Laternula tasmanica 10 0

Notospisula trigonella 56 11

Paraoorphium sp. 12 0 F. Eusiridae 79 24 F. Oedicerotidae 40 5

Megamphapus sp. 40 5

Paraphoxus sp. 3 0

Melita sp. 16 5

TABLE 11

THE TOTAL NUMBER OF SPECIES AND INDIVIDUALS FOUND BEFORE AND AFTER WEED CLEARING

BEFORE AFTER

Species 16 8 Individuals 894 312 77

CHAPTER 7

THE EFFECT OF POWER STATION DISCHARGES UPON SHALLOW WATER BENTHOS

7.1 INTRODUCTION

Power Stations that use marine or fresh water as a coolant produce an artificial current in, and raise the temperature of, the area around the discharge. Investigations concerning the effects of these factors upon the benthic infauna in Lake Macquarie and Budgewoi Lake have been carried out by Powis (1973). He found no changes in community structure near the discharges. However, the sites sampled in this study were situated in the mud zones and were relatively deep. Hence, the temperatures recorded showed that the benthos experienced only very small increases in temperature.

The quantitative surveys outlined in Chapter 4 discussed the characteristic benthic community in the Zostera beds of

Budgewoi Lake. These beds are located in shallow water (less than one metre deep) in the path of the Power Station discharge. The feature of the benthos was the presence in large numbers of the gastropod Velaoumantis australis . It was also noted that in this area the current was very pronounced and the temperature up to 4°C greater than that of the surrounds.

Subsequent to the findings of the quantitative survey, an underwater study was made of the shallow areas around the

Wangi and Vales Pt. Power Station discharge areas located in Discharge Canal /f,

Figure 31. - The distribution of dead

Velaoumantis (X) in relation to the hot water discharge (—*) and the presence of weed beds

(////). 79

Lake Macquarie and the area around Munmorah Power Station discharge located in Budgewoi Lake. uje rt A series of laboratory experiments ’ also conducted to observe the response of Velacumantis to a temperature gradient.

7.2 SCUBA OBSERVATIONS

Observations revealed that Velacumantis was very abundant in areas around Wangi and Vales Pt. Power Station discharges. These areas consisted of stoney sediment with little or no fine sediment present. The sediment around

Munmorah Power Station discharge consisted of clay and silt. Turbidity was too great to enable any observations to be made. However, large numbers of dead Velacumantis were found along the shore line. These dead shells were found when the Zostera beds and warm water current occurred together (Figure 31) .

7.3 BEHAVIOURAL EXPERIMENTS A. Methods

A 1.3 metre chamber was used as a test tank. A rectangular piece of perspex divided the tank into two chambers. These were connected by a five centimetre gap, formed between the end of the perspex and the wall of the tank (Figure 32). Sea water (35°/00) was placed in the tank and left for 24 hours. A submersable heater was placed at one end of the tank. Velacumantis were collected from an area in Wangi Bay, Lake Macquarie. The temperature recorded at this site was 17°C. Fifteen animals were placed randomly eater

erspex Divider

Ve lacumantis

Test Tank

Figure 32. - Apparatus used in behavioural study of Velaoumantis australis. 81

in each chamber and then the heater turned on. Due to the

slow moving nature of the animals it was possible to check

their positions every ten minutes. The experiment ran for

three hours. It was repeated five times, each time with

a different set of animals.

B. RESULTS

Throughout the series of experiments only four animals moved against the temperature gradient. Sixty percent of the

animals moved, to a greater or lesser degree, towards the heater. Figure 33 gives details of the movements of the

Velaoumantis and the test temperatures in one of the trials.

In most cases animals placed in the non-heated chamber actively sought the small opening that connected the non- heated chamber to the heated chamber. They did this by moving towards the heated chamber until the perspex divider was encountered. They would then move along the perspex wall until they found the opening. Approximately one-third of the animals were found huddled around the heater by the end of the experiment. The temperatures at this site were at times as high as 27°C. In all trials a temperature gradient of between 2°C and 4°C was maintained throughout.

The positive response of Velaoumantis to higher temperatures indicates that temperature may be the factor that explains the large populations of the animal outside Power

Station discharges. Time = 0 hours 16.9 16.9 C

Time = 2 hours 21.0 C 18.4 C

Time 3 hours 19.8 C 22.8 C

Figure 33. - Behavioural response of Velacumantis ( <

to a temperature gradient applied over 3 hours

Temperatures recorded are cited. 83

7.4 POWER STATION DISCHARGES AND BENTHOS: AN OVERVIEW

It is clear that the Power Station discharges studied do not greatly effect the benthic fauna living in mud or weed substrates. The only significant alteration to the faunal composition in the discharge area is the presence of large numbers of Velacumantis australis in shallow water areas .

Earlier chapters in this thesis have shown that weed areas in both Tuggerah Lakes and Lake Macquarie contain a greater number of species and individuals than any other substrate. Prior to the construction of the Munmorah Power

Station large areas of Budgewoi Lake were described by

Higginson (1965) as having an extensive weed coverage. It is consequently of great concern that these areas are described in this thesis as the mud zone - that is, having no weed present. Substrate areas in Munmorah and Tuggerah Lakes have remained relatively constant since Higginson’s surveys. The reason for the changes in Budgewoi Lake is probably related to the high turbidity found outside the discharge of the

Power Station (Hodgson, 1974). This would cause a reduction in transmittable light reaching the substrate and hence inhibit weed growth. The reduced weed growth would cause a marked reduction in benthic diversity and hence would be detrimental to the health of the lake.

It is of vital importance when planning the site for any power station that the distribution and extent of weed growth be determined to ascertain the possible effects upon the benthic fauna. 84

CHAPTER 8

GENERAL DISCUSSION

Tuggerah Lakes' benthic fauna is divided into several

faunal groups whose distribution is dependant upon the type of substrate present. The majority of the lakes’ substrate consists of mud. This supports a ”mud” fauna which is composed of small numbers of individuals and species. In contrast to this fauna is that which characterizes the weed areas of the lakes. This has larger numbers of both species and individuals. The weed fauna can itself be divided into several different faunal groups. The type of group found depends both upon the weed species and upon the type of sediment in which the weed grows. The most diverse groups are those associated with Zostera oapricorni. Within any substrate the fauna throughout the three lakes is generally homogeneous and seasonally stable. The faunal destruction caused by the flood was extensive. In comparison, the Munmorah Power Station was shown to only change the structure of the benthic communities, not to reduce their diversity. However, the proposed weed clearing operations were demonstrated to be extremely detri­ mental to the weed fauna and ultimately to the fishing industry.

The survival of the present weed areas in Tuggerah Lakes should, therefore, be paramount in any future development of the Tuggerah Lakes area. 85

REFERENCES

ANDREWS, J.D. (1973) - Effects of tropical storm Agnes on epifaunal invertebrates in Virginia Estuaries. Chesapeake Science 14_(4) : 223-234.

BAAS BECKING, L.G.M., THOMSON, J.M., and WOOD, E.J.F. (1959) - Some aspects of the ecology of Lake Macquarie, N.S.W. with regard to an alleged depletion of fish. I. General Introduction. Aust. J. Mar. Freshw. Res. 10: 269-278. BAYLISS, D. (1973) - Marine Fouling Organisms in Lake Macquarie and the Tuggerah Lakes, N.S.W. M.Sc. Thesis, University of N.S.W. BEBBINGTON, G.N. (1974) - Fish Kill in Lake Munmorah - 1st July 1974. Technical Report GNB:RH, State Fisheries of N.S.W. DRISCOLL, E.G., and BRANDON, D.E. (1973) - Mollusc-sediment relationships in northwestern Buzzards Bay, Massachusetts, U.S.A., Malacologica 12: 13-14. HARPER, S. (1972) - The Hydrology and Some Aspects of the Ecology of Selected Zooplankton Organisms of Lake Macquarie and the Tuggerah Lakes System. Honours Thesis, University of N.S.W. HIGGINSON, F.R. (1965) - The distribution of submerged aquatic angiosperms in the Tuggerah Lakes System. Proc. Linn. Soc. N.S.W. 90_: 328-334. HIGGINSON, F.R. (1971) - Ecological effects of pollution in Tuggerah Lakes. Proc. ecol. Soc. Aust. 5: 143-152.

HODGSON, B. (1974) - The Effect of a Power Station Cooling System on the Ecology of Estuarine Plankton: an Abstract in Aust. Marine Sci. Bull. No.47. LIE, U. (1968) - A quantitative study of benthic infauna in Puget Sound, Washington, U.S.A. in 1963-64. Fisk. Dir. Skr. (Ser. Havunders) 1_4: 229-556.

MacINTRYE, R.vT. (1959) - Some aspects of the ecology of Lake Macquarie, N.S.W., with regard to an alleged depletion of fish. VII. The benthic macrofauna Aust. J. Mar. Freshw. Res. 10: 341-353.

MILNER, H.B. (1962) - ’’Sedimentary Petrography" Vol.l. Methods in Sedimentary Petrology (George Allen and Unwin Ltd: London). 86

NICOLES, F.N. (1970) - Benthic polychaete assemblages and their relationship to sediment in Port Madison, Washington. Marine Biology 6_: 48-57.

PEARCE, J.B. (1974) - Invertebrates of the Hudson River Estuary. Annals of the N.Y. Acad, of Sci. 250: 137-143.

POWIS, B.J. (1973) - The Effect of Power Station Discharges upon Benthic Infauna. Honours Thesis, University of N.S.W.

REMAINE, A., and SCHLIEPER, C. (1971) - "Biology of Brackish Water". (Wiley Interscience: N.Y.).

ROY, P.S. and PEAT, C. (1974) - Sediment Map of Tuggerah Lakes. Report to Geological Survey of N.S.W., Department of Mines, 14-1-74.

SANDERS, H.L. (1956) - Oceanography of Long Island Sound, 1952-1954. 10_. The biology of marine bottom communities. Bull Bingham oceanogr. Coll. 15: 345-414.

SPENCER, R.S. (1959) - Some aspects of the ecology of Lake Macquarie, N.S.W., with regard to an alleged depletion of fish. II. Hydrology. Aust. J. Mar. Freshw. Res. 10: 279-96.

WEINER, P. (1974) - Unpublished material.

YOUNG, D.K., and RHOADS, D.C. (1971) - Animal-sediment relations in Cape Cod Bay, Massachusetts. I. A transect study. Marine Biology. 11(3): 242-254. 87

APPENDIX A

TABLE A LIST OF SPECIES FOUND IN PRELIMINARY SURVEY

TABLE B SPECIES (GIVEN BY ARBITRARY COMPUTER NUMBER)/SITE DATA FOR PRELIMINARY SURVEY 88

TABLE A

SPECIES LIST - WITH EACH SPECIES ARBITRARY COMPUTER NUMBER

Class Polychaeta

Armandia intermedia Fauvel (3)

Australomereis ehlersi Augener (24)

Family Capitellidae (42)

Haploscopolos simplex Hutchings (6)

Marphysa sanguinea Montagu (28)

Hereis (Hediste) diversicolor O.F. Muller (1)

Magelona sp. (45)

Nephtys australiensis Fauchald (5)

Owenia fusiformis della Chiaje (4)

Family Pilargidae (46)

Class Gastropoda

Austrocochlea constricta Dillwyn (13)

Bedeva hanleyi Angas (31)

Conuber conica Lamarck (32)

Nassarius jonasi Dunker (8)

Velacumantis australis Quoy and Gaimard (9)

Class Pelecypoda

Laternula tasmanica Iredale (15)

Macoma deltoidalis Deshays (11)

Notospisula trigone l la Lamarck (10)

Sanguinolaria onuphria Iredale (7)

Theora fragilis Adams (12)

Xenostrobus securis Lamarck (14) 89

TABLE A (Cont)

Class Crustacea

A) Order Amphipoda

Family Eusiridae (17)

Exoedicevos sp. (16)

Melita sp. (18)

Family Oedicerotidae (19)

Orohestia sp. (23)

Paraphoxus sp. (20)

B) Order Isopoda

Mesanthura sp. (21)

C) Order Decapoda

Halicarcinus australis (38)

Halicarcinus sp. (39)

Class Actinozoa - Species 1 (22)

Nematodes (44) 90

TABLE B SPECIES COMPOSITION OF EACH SAMPLING SITE SHOWING ABUNDANCE OF EACH SPECIES (DENOTED BY ITS COMPUTER NUMBER) COMPUTER NUMBER STATIONS OF SPECIES 1 2 3 4 5 6 7 8 9 10 11 12 13

1 1 3 11 3 3 111 4 4 10 11 3 11 5 6 7 22 18 13 2 1 33 48 8 15 8 1 6 1 16 2 2 9 9 7 12 1 1 1 13 10 4 12 2 1 7 11 4 5 11 7 9 12 2 123 13 14 7 7 15 4 16 17 18 5 1 4 19 1 1 20 5 1 21 1 7 2 3 23 24 28 1 1 31 32 38 1 1 39 42 7 3 2 43 44 1 45 1 46 91

TABLE B (CONT)

COMPUTER NUMBER STATIONS OF SPECIES 14 15 16 17 18 19 20 21 22 23 1 1 3 3 3 1 1 2 5 2 4 25 11 7 19 7 7 5 1 CNJ

6 2 rH

7 21 rH 8 2 1 6 3 1 12 1 11 9 4 4 3 10 3 3 2 11 12 20 11 5 9 9 12 49 1 9 13 14 2 27 10 584 107 15 16 2 5 17 1 1 18 8 20 5 5 12 19 5 1 3 2 1 20 1 7 1 21 4 9 7 3 12 6 1 23 6 3 24 28 31 1 32 38 39 42 2 3 11 43 44 1 45 46 92

TABLE B (CONT)

COMPUTER NUMBER OF STATIONS SPECIES 24 25 26 27 28 29 30 31 32 33 34 35 36

1 19 61 3 2 3 2 4 4 30 5 6 7 8 3 9 17 10 3 11 20 2 12 3 4 13 14 6 62 18 3 15 16 17 1 18 3 1 19 2 20 2 21 4 118 1 23 24 28 31 1 32 38 39 42 7 2 11 9 2 42 43 2 2 2 44 45 46 1 93

TABLE B (CONT)

COMPUTER NUMBER STATIONS OF SPECIES 37 38 39 40 41 42 43 44 45 46 47 48 49

1 18 4 15 3 4 8 25 5 2 6 4 2 7 8 252 1 9 34 1 2 10 3 11 2 4 3 12 2 13 35 14 13 2 15 1 16 17 2 7 18 1 19 20 21 12 3 2 23 24 2 28 31 32 1 38 39 42 2 4 1 1 1 7 43 1 44 1 45 46 94

TABLE B (CONT)

COMPUTER NUMBER OF STATIONS SPECIES 50 51 52 53 54 55 56 57 58

1 30 1 1 10 3 4 10 3 46 5 6 7 5 8 3 18

9 4 CM

‘ — 10 4 11 1 2 I

11 4 3 112 1 1 CM 12 10 1 2 13 14 5 20 23 15 16 17 7 1 18 1 19 2 19 20 6 21 4 11 4 23 24 28 31 32 1 38 39 42 13 4 43 5 3 44 45 46 APPENDIX B

CLASSIFICATION TECHNIQUES 96

1.0 INTRODUCTION

When a benthic ecologist is confronted with a large amount of species/site data, two avenues of analysis present themselves. The first of these, Classification, is used when the data is assumed to consist of groups of sites or species.

Classification describes the process by which the most informative set of groups is extracted from the data. The second type of analysis available to the ecologist is conceptually much harder to visualise, it is the process of

Ordination. Ordination is used when the data is assumed to be continuous - not capable of being broken into groups. The ecological sense is derived by plotting the elements in a

Euclidean Space. Sokal and Sneath (1974) point out that it is much easier for man to conceptualise groups of elements, rather than elements in a continuum. It is probably for this reason be C O-yjSC- and also statistically - units or groups are easier to manipulate - that Classification appeals more to the benthic ecologist than does Ordination.

Stephenson et al. (1970) extensively reviews the development of community concepts and their relationship to

Classification. They conclude that communities are best characterized by the internal associations among species. The concepts of Constancy (percentage of samples in which a species occurs) and Fidelity (degree of restriction of a species to a particular association) have dominated the development of community statistics. Methods of characterizing communities by the constancy and fidelity of their species have developed in the form of Similarity Coefficients. These will be dealt with in more detail later in the discussion. 97

Non-Hierarchical Hierarchical

Divisive Agglomerative

Monothetic Polythetic Polythetic

Figure 34. - Choice of Classification Strategies.

X

+A ______|______.-A

(X) (x)

+B ______|______, -B I I (XB) (Xb)

Figure 35. - The dendrogram resulting from the example

cited by Williams and Lambert (1959). 98

Classification may be seen as a two part process. The first procedure is to calculate similarity coefficients from the data, forming a matrix (normally site x site) of coefficients. The next stage is to group together the elements (sites say) that most closely resemble each other. This process is termed Clustering.

The following discussion will attempt to sort out from the vast array of classificatory techniques, the most suitable form for the benthic ecologist to use.

2.0 TYPES OF CLASSIFICATION Upon deciding to use Classification the benthic ecologist is then confronted with a series of choices, these are summarised in Figure 34. These choices relate to the method by which the coefficients of similarity coupled with the Clustering strategy are applied to the data.

2.1 HIERARCHIAL OR NONHIERARCHIAL A Hierarchial strategy always optimizes a route between the entire population and the set of individuals of which it is composed. The route may be defined by either progressive fusions from individuals to the population, or by division from the population to its individuals. To accomplish this the strategy must optimize some function between the two groups to be fused next. A Nonhierarchial strategy optimizes the structure of the individual groups, no routes being defined

(Williams, 1971). The best way to illustrate the functional differences between these two forms is by an example presented by Williams and Lambert (1959). Imagine a population, X, 99

which is divided into two sub-groups (X) and (x). The division occurs because (X) possess the species A and (x) lacks the species. (X) is then found to be divisible on the basis of the presence or absence of species B, resulting in two populations (XB) and (Xb), the latter group not containing the species. A nonhierarchial classification would pool (Xb) with (x) to form a new population. An hierarchial strategy does not discard the information relating to the (X)/(x) discontinuity, but presents it graphically in the form of a Dendrogram (Figure 35). In support of hierarchial classifications Williams and Lambert (1959) criticise the pooling of populations in nonhierarchial classifications. They point out that the final groups produced are not capable of statistical definition in terms of presence or absence of key species and the route by which these groups are obtained is not meaningful. In essence then, it would appear that hierarchial strategies give the ecologist much more information and present more of a "story” than do nonhierarchial procedures.

2.2 DIVISIVE OR AGGLOMERATIVE Divisive classifications treat the population containing

"n" attributes as an entity "N" and then progressively split it up, eventually into "n" groups. An Agglomerative classification begins with "n" attributes and progressively fuses them until the population "N" results. Figure 36 illustrates these two forms. Williams (1971) points out inherent disadvantages with agglomerative classifications. Firstly, the agglomerative 100

DIVISIVE

n entities

AGGLOME RATIVE n entities

Figure 36. - Graphical representation of Divisive and Agglomerative procedures. 101

system initiates calculations at the inter-individual level where chances of sampling error are greatest. As a result there is a great chance of early incorrect fusions which would lead to misclassifications in the higher levels of the hierarchy. Agglomerative techniques require much longer computational time to reach these high levels, whereas divisive calculations can be truncated at an early stage, thus reducing the cost of computer time considerably.

2.3 MQNOTHETIC OR POLYTHETIC

Monothetic strategies are strategies that divide the population on the basis of the presence or absence of a single species . The species chosen must divide the population into two groups which are as unlike as possible. Since the selection of the attribute depends on the properties of the whole population then agglomerative monothetic models are impossible.

A Polythetic system is one based on a measure of similarity applied over all individuals of a site, so that sites are grouped with those, on average, they most resemble. The measure of similarity used considers the numbers of each species belonging to each site. If the number of each species at the sites is very similar then the similarity measure is high and the sites are grouped together. If the numbers are quite different then the similarity measure is low and the sites separated.

The monothetic approach has the advantage of ease of computation and simplicity. However, as Williams (1971) points out misclassifications are common. This is borne out when 102

one considers for example a site "A" which on the whole resembles site "Y" but by chance happens to possess the division species, "B" which monothetically groups it with site "X”.

2.4 NORMAL OR INVERSE ANALYSIS

The preceding discussion has used in examples the classification of sites with respect to the species composition. This is termed normal analysis. However, it is sometimes useful to ecologists to elucidate species’ assemblages. This is accomplished by using inverse analysis, that is, classification of the species with respect to the sites they occur at.

2.5 RECOMMENDATIONS

It would seem that the best classificatory technique to use would be an Hierarchial-Divisive-Polythetic classification.

Unfortunately this form is the least statistically developed.

Hierarchial-Agglomerative-Polythetic methods have been developed and have been demonstrated to give ecologically meaningful results by Stephenson et al. (1970), Stephenson and

Williams (1971) and Hughes and Thomas (1971). Since this classificatory approach has been shown to be the best of the developed forms, it is thought at present to be the most desirable.

3.0 COEFFICIENTS OF SIMILARITY

The next choice facing the ecologist is to choose a suitable association measure. The choice is dictated by the 103

type of data collected.

3.1 BINARY DATA

Binary data is data based on records of the presence or absence of species. The most frequently used association index is the Czechanowski coefficient (Stephenson et al, 1970;

Field and McFarlane, 1968 and Day et al., 1971)

The measure used in the Tuggerah Lakes Preliminary Survey was Information Analysis. It has not been widely used in benthic work but has had considerable success in botanical work (Lambert and Williams, 1966 and Williams et al., 1966).

The analysis used is contained in the C.S.I.R.O. computer program designated "DIVINF". This incorporates the Shannon

Information Content, I where:

s I = snlnn - £ {a.lna. + (n-a.)In(n-a•)} j=i J J where a total of n stations is defined by the presence or absence of s species and let the jth species occur at a^ of the station. The formula is applied to each species. The population is divided each time into those possessing and those lacking the species. If we assume the information content of the two populations as I( + ) and I(-) respectively then the information gain is represented by Al such that:

Al = I - (!(+)+!(-))

The population is divided on that species for which Al is maximum. This process is repeated until the number of site groups required is obtained (Stephenson et al f 1970). 104

3.2 QUANTITATIVE DATA

Quantitative data is data that includes the number of each species at each site. There are two coefficients that are extensively used in benthic studies. These are the

Canberra Metric and the Bray-Curtis coefficients. They are as follows:

Canberra Metric = j £

Bray-Curtis i xirx2i

two sites being compared. The Bray-Curtis has been success­ fully used by Field and McFarlane (1968) and Stephenson and Williams (1971). It has the disadvantage that the denominator is the sum of all individuals of all species. Hence the value obtained is greatly influenced by dominance. The Canberra Metric differs in being the sum of a series of fractions. Outstanding values, due to dominant species,

contribute only a fraction to the overall value.

4.0 CLUSTER ANALYSIS

As discussed in the Introduction once a matrix of similarity coefficients has been established the coefficients need to be grouped. This is facilitated by one of the many methods of Cluster analysis. The most widely used are; Nearest

Neighbour, Centroid, Group Average, Furthest Neighbour and Flexible. These procedures measure the distance between the 105

C ^ ^ N

B

Figure 37. - Illustration of Group-Average Sorting

where an individual "B" will join the group "A" or "C", whichever it is closest to on average after measuring the distance between it and every member of each group. 106

coefficients of similarity. It is the mode of measurement that differs. Group average is depicted in Figure 37. In this figure the distance between B and each of the individuals of groups A and C is measured. B joins the group to which it is closest to on average. Centroid strategies find the centre of gravity of each group. Fusion of an element, say

B, depends on its proximity to a particular centroid. It would appear that Nearest Neighbour sorting is guilty of poor clustering abilities (Williams et al., 1966) and for this reason is seldom used in benthic work.

5.0 CONCLUSION This review was necessary due to the widespread nature of the information relating to classification. The study of the Tuggerah Lakes fauna successfully used information analysis to demonstrate the broad faunal zones in the lakes. The Canberra Metric and Group Average Sorting was used to examine more closely these faunal zones. If time and money exist it would be most profitable to use as many different combinations of similarity coefficients and clustering strategies as possible. These two requirements seldom exist and one is often forced to decide upon one or two techniques. The choice is dictated by the type of benthic survey conducted. It is hoped that this review has elucidated the factors involved in making such a choice. 107

REFERENCES

DAY, J.H., FIELD, J.G. and MONTGOMERY, M.P. (1971) - The use of numerical methods to determine the distribution of benthic fauna across the Continental Shelf of North Carolina. J. Anim. Ecol., 40: 93-123. FIELD, J.G. (1969) - The use of information statistics in the numerical classification of heterogeneous systems. J. Ecol. , 5_7 : 565-569. FIELD, J.G. and McFARLANE, G. (1968) - Numerical methods in marine ecology. 1. A quantitative "similarity" analysis of rocky shore samples in False Bay, South Africa. Zool. Afr., 3y 119-137. HUGHES, R.N. and THOMAS, M.L.H. (1971) - The classification and ordination of shallow water benthic samples from Prince Edward Island, Canada. J. exp. mar. Biol. Ecol. , 7_: 1-39. LAMBERT, J.M. and WILLIAMS, W.T. (1966) - Multivariate methods in plant ecology. VI. Comparison of Information analysis and Association analysis. J. Ecol., 54: 635-650. LANCE, G.N. and WILLIAMS, W.T. (1966) - A generalised sorting strategy for computer classifications. Nature, 212: 218. SOKAL, R.R. and SNEATH, P.H. (1973) - "Numerical Taxonomy" (Freeman and Co.: San Francisco). STEPHENSON, W. (1974) - Unpublished material. STEPHENSON, W. and WILLIAMS, W.T. (1971) - A study of the benthos of soft bottoms - Sek Harbour, New Guinea, using numerical analysis. Aust. J. Mar. Freshw. Res., 22: 11- 34. STEPHENSON, W., WILLIAMS, W.T. and LANCE, G.N. (1970) - The macrobenthos of Moreton Bay. Ecol. Monogr., 40: 459-494. WILLIAMS, W.T. (1971) - Principles of Clustering. A rev, ecol. sys t. , 2_: 303-326. WILLIAMS, W.T. and LAMBERT, J.M. (1959) - Multivariate methods in plant ecology. I. Association analysis in plant communities. J. Ecol. , 4 7 : 83-101.

WILLIAMS, W.T., LAMBERT, J.M. and LANCE, G.N. (1966) - Multivariate methods in plant ecology. V. Similarity analysis and Information analysis. J. Ecol., 54: 427-446. 108

APPENDIX C

TABLE A COMPUTER NUMBERS GIVEN TO SPECIES FOUND IN QUANTITATIVE SURVEYS

TABLE B SPECIES/SITE DATA FOR THE JULY QUANTITATIVE SURVEY

TABLE C SPECIES/SITE DATA FOR THE SEPTEMBER QUANTITATIVE SURVEY

TABLE D SPECIES/SITE DATA FOR THE DECEMBER QUANTITATIVE SURVEYS 109

TABLE A COMPUTER NUMBER OF ALL SPECIES FOUND IN JULY, SEPTEMBER AND DECEMBER QUANTITATIVE SURVEYS

COMPUTER NO. SPECIES

1 Nereis (Hediste) diversicolor 2 Ancistrosyllis sp. 3 Armandia intermedia 4 Owenia fusiformis 5 Nephtys aus traliensis 6 Haploscopolos simplex 7 Sanguinolaria onuphia 8 Nassarius jonasi 9 Velacumantis australis 10 Notospisula trigonella 11 Macoma deltoidalis 12 Theora fragilis 13 Austrococlea constrict a 14 Xenos trobus securis 15 Laternula tasmanica 16 Magelona sp. 17 Family Eusiridae 18 Melita sp. 19 Family Oedicerotidae 20 Paraphoxus species 1 21 Mesanthura sp. 22 Class Actinozoa 23 Orchestia sp. 24 Australonereis ehlersi 25 Barantolla lepte 26 Notomastus hemipodus 27 Macrobrachium sp. 28 Marphysa sanguinea 29 Prionospio sp. 30 Hermit crab 31 Bedeva hanleyi 32 Parophoxus species 2 33 Metapenaus bennettae 34 Pyrazus ebeninus 35 Ealicarcinus sp. 36 Callianassa sp. 37 Nematodes 38 Ealicarcinus australis 39 Coleopteran larvae TABLE B SPECIES/SITE DATA FOR THE JULY QUANTITATIVE SURVEY COMPUTER NO. STATIONS OF SPECIES T7 7 HCOLOH-LOvDNOOOlOHNLOH-LOvONOOaiOHCOLOH-LJlvOISOOOlOHCOLOH-LOvOtsCO H" LO cd LO

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STATIONS

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1 12 3 10 2 1 1 1 3 4 13 233 2 5 1 6 8 10 7 8 7 14 4 2 9 15 10 5 4 1 11 4 46 1 1 1 12 1 3 13 14 174 10 83 4 15 5 16 17 9 2 4 12 2 18 16 16 15 32 19 13 2 77 22 20 1 31 12 10 21 29 2 1 13 1 22 2 2 23 1 1 24 25 4 1 2 26 5 1 1 3 3 27 4 28 1 1 1 5 29 4 30 31 32 1 9 1 16 1 33 34 35 36 37 1 1 38 2 39 40 4 TABLE D SPECIES/SITE DATA FOR THE DECEMBER QUANTITATIVE SURVEYS COMPUTER NO. STATIONS K O X OF SPECIES , , 4 - H(OtOH-LOCTT'OOCTiOHMtOH-uivONODOiOrHNtOH-LOCTt O rH OO CO LO OO OO OO LO

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APPENDIX D HYDROLOGICAL DATA 114

TABLE 1 TEMPERATURE AND SALINITY PROFILES FOR ALL STATIONS SAMPLED IN QUANTITATIVE STUDY IN JULY 1974

STATION DEPTH (m) TEMPERATURE SALINITY (fc) (u/oo)

1 0 14.4 7.7 1 14.4 7.7 2 14.4 7.7 2 0 13.5 7.0 1 13.5 7.0 3 0 14.4 7.7 1 14.4 7.7 2 14.3 7.8 3 14.3 7.8 4 0 16.0 8.0 1 16.0 8.0 5 0 15.6 8.0 1 15.8 8.0 2 15.7 8.0 2.5 15.7 8.0 6 0 15.6 8.3 1 15.6 8.3 2 15.4 8.3 2.5 13.9 8.4

7 0 17.6 8.0 1 17.6 8.0 2 17.6 8.0 2.5 17.5 8.0

8 0 22.0 7.8 1 20.5 7.8 1.7 15.6 9.1

9 0 15.6 8.3 0.5 15.6 8.3

10 0 16.4 8.0 1 16.4 8.0 2 16.0 8.3 11 0 14.1 8.2 1 14.1 8.2 2 14.8 12.2

12 0 13.4 13.4 1 13.1 13.4

13 0 12.8 13.6 1 14.2 13.5 2 14.7 13.8 115

TABLE 1 (Cont)

STATION DEPTH (m) TEMPERATURE SALINITY -per (°/oo) 14 0 12.6 14.2 1 12.6 14.2 2 12.6 14.2 2.5 12.6 14.7 3.0 14.2 26.6 3.3 14.7 28.7

15 0 13.9 16.2

16 0 13.6 15.5 1 14.1 17.3 1.2 14.5 21.6

17 0 13.5 13.5 .0 13. 1 15.5

18 0 13.0 13.5 1 12.8 14.3 2 13.3 14.7 19 0 13.0 13.7 1 13.0 13.7 116

TABLE 2 TEMPERATURE AND SALINITY PROFILES FOR ALL STATIONS SAMPLED IN DECEMBER QUANTITATIVE STUDY

STATION DEPTH (m) TEMPERATURE SALINITY -per (°/oo)

2 0 25.9 19.4 1 25.9 19.4

3 0 25.9 19.4 1 25.8 19.4 2 25.8 19.3 3 25.4 19.2

5 0 25.6 19.2 1 25.4 19.2 2 25.4 19.2 2.5 25.4 19.2

7 0 26.5 19.4 1 26.5 19.4 2 26.5 19.4 8 0 31.7 18.7 1 28.7 18.8 1.8 26.0 19.0 10 0 28.5 19.1 1 28.4 19.2 2 25.7 19.5 2.2 25.7 19.5 11 0 25.8 19.0 1 25.8 18.8 1.7 25.8 18.9

13 0 26.4 22.8 1 26.4 22.8

14 0 26.2 22.2 1 26.0 22.3 2 25.5 22.5 3 25.4 22.5 15 0 25.2 27.4

16 0 24.5 29.0 1 25.4 29.0 17 0 .265 21.2 .5 26.3 21.5

18 0 26.7 19.8 1 26.7 22.0 19 0 26.3 23.4 . 5 25.8 23.4 117 118

DESCRIPTIONS OF BENTHIC ANIMALS FOUND

IN TUGGERAH LAKES.

The following descriptions include only those species that are very abundant in Tuggerah Lakes. As such, they serve as an illustrated guide book, not a key to the species. 119

POLYCHAETES 1. Family Capitellidae a) Notomastus hemipodus

Characteristics - A dark brown-red animal that has distinctive cross hatched marks on the first few segments

It has a rounded prostonium, Distribution - Found throughout the three lakes in weed and mud areas. b) Bavantolla lepte

Characteristics - A small thread-like worm with a small pointed prostonium. Distribution - Throughout the three lakes in mud and weed areas. 120

2. Family Eunicidae

a) Marphysa sanguinea

Characteristics - A long and stout body with brown pigmentation around the head region. The head has two eyes and is bilobed.

Distribution - Not very common but usually found in weed beds in muddy sediment. 3. Family Oweniidae

a) Owenia fusiformis

Characteristics - The worm is found in a tough sand tube. The head appendages consist of a frilly food gathering membrane.

Distribution - Found throughout the Tuggerah Lakes in weed beds with muddy sand sediment. Large numbers are found at the mouths of Wyong and Ourimbah Creeks. 122

4. Family Nereidae

a) Nereis (Hediste) diversicolor

Characteristics - The body is usually green or yellow.

The head has brown pigmentation, four eyes and eight

tentacular cirri.

Distribution - Very common in weed beds with a muddy

sediment. This substrate is found predominantly in

Tuggerah Lake. b. Australoneris ehlersi

Characteristics- The animal is found in a thin sand tube. The ventral surface has a number of white papillae.

Distribution- Found near "The Entrance" in a sandy substrate 5. Family Nephtyidae a) Nephtys australiensis

Characteristics - The head is five sided. A groove runs ventrally down the length of the body.

Distribution - Found primarily in weed beds near

The Entrance". 6. Family Ophelidae

a) Armandia intermedia

Characteristics - The body is long and rounded.

Gills extend over most of the body. A deep groove runs down the ventral side.

Distribution - Found throughout the three lakes in muddy sediment. 7. Family Orbinidae a) Haplos copolos simplex

Characteristics - The head is conical and pointed.

The gills are well developed in the abdomen.

Distribution - Common in sandy substrates in Tuggerah and Budgewoi Lakes. 127

8. Family Lumbrineridae a) Lumbvineveis latreilli

Characteristics - Conical prostonium with no appendages.

Distribution - Not common, found mainly in mud zone. 9. Family Magelonidae a) Magelona sp.

Characteristics - Head is flattened and has two long palps.

Distribution - Found in mud zone of all lakes. 129

10. Family Pilargidae a) Anoistrosyllis sp.

Characteristics - Body is elongate, head has three antennae and two palps.

Distribution - Found in mud zone of all lakes. MOLLUSCS

A. BIVALVES

1. Laternula tasmanioa

Characteristics - Shell is white - elongately oblong with prominent central umbos.

Distribution - Widespread in weed beds with sandy sediment. 2. Notospisula trigonella

Characteristics - Shell is cream coloured, smooth, and triangularly ovate.

Distribution - Very abundant in the mud areas of all three lakes. 132

3. Sanguinolaria onuphia

d Characteristics - Shell is distinctively redlsh in colour.

Distribution - Found only in sand substrates. 133

4. Maeoma deltoidalis

Characteristics - A large white shell which is solid and opaque.

Distribution - Widespread throughout all mud substrate and sandy mud sediment. 134

5. Xenostrobus seouris

Characteristics - The colour of adults is dark brown, however, juveniles often have a brown/yellow variegated pattern.

Distribution - Found attached to weed and algae primarily in areas where a flow of water exists i.e. outside creeks and in the path of the Power Station current. 135

B. GASTROPODS

1. Austro co chlea oonstricta

Characteristics - Shell is thick, solid and turbinate.

The surface is marked with zig-zag lines or stripes.

The colour is variable - red, grey or white.

Distribution - Found exclusively in the channel near

"The Entrance".

2. Bedeva hanleyi

Distribution - Found primarily in Zostera/mud substrates throughout the lakes. 136

3. Nassarius jonasi

Distribution - Found in all sediment/substrate areas of the three lakes. 137

4. Velacumantis australis

Distribution - Large numbers are found in Zostera beds that are located in the path of the Power Station discharge. They occur in small numbers in weed beds throughout the lakes. 138

CRUSTACEANS

1. ISOPODS a) Mesanthura sp.

Characteristics - Extensive brown and black pigmentation on dorsal surface.

Distribution - Occurs in small numbers throughout the lakes. 139

2. AMPHIPODS 1. Family Phoxocephalidae

a) Paraphoxus sp.

Distribution - Occurs only in weed beds. Present in all lakes. 140

2. Family Gammaridae a) Melita sp.

Distribution - Found in weed beds throughout the lakes. 141

3. Family Eusiridae

Distribution - Found in weed beds with a mud sediment. 142

4. Family Oedicerotidae

Distribution - Widespread in weed areas. 143

3. CRABS

a) Ealicaroinus australis

Distribution - Found in weed beds throughout the three lakes.