Moreton of Coral Deaths at Peel Island, Moreton Bay, in Early 1956

C/iorO flJrO

pry-er University of Queensland Papers

DEPARTMENT OF ZOOLOGY

Volume I. 1959 Number 7

An ln�est�gation Peel An Investigationl$Iand'�:··,·Moreton of Coral Deaths at Peel Island, Moreton Bay, in Early 1956

BY R. J. SLACK-SMITH, B.Sc.

Price: Two Shillings

Fry, QL a 1 .117 v.l THE UNIVERSITY OF QUEENSLAND PRESS BRISBANE NO, 7 20th JANUARY, 1960 1

Vol. I 1959 No.7

An Investigation of CoFal I)eaths at Peel Island, ·• ' Moreton Bay, in Early I 9 s6

R. ]. SLACK-SMITH, B.Sc.

Department of Zoology, University of Queensland

THE UNIVERSITY OF QUEENSLAND PRESS BRISBANE JANUARY, 1960 Wholly set up and pnnted in Australia by WATSON, FERGUSON AND COMPANY Brisbane, lll60 An Investigation of Coral Deaths at Peel Island, Moreton Bay, in Early 1956

R. ]. SLACK-·SMITH, B.Sc.

SUMMARY

The distribution of corals 'at Peel Island and adjacent areas in Moreton Bay was investigated in early 1956, following a report of coral .deaths. This report was cO:nfirmed, and the deaths are related to excessive summer rainfall. The zonation of common animals in the lower littoral and sublittoral is described. Only Fa via speciosa had been permanently affected.

I INTRODUCTION

The OCCJJrrence of corals in Moreton Bay, which is over 150 miles south of the Great Barrier Reef area, has aroused the attention of several authors (Strutchbury 1855; Saville-Kent 1893; Hedley 1925b; Fairbridge 1950; Wells 1954; Stephenson and Wells 1956; and Endean, Kenny and Stephenson 1956).

The most extensive coral patches are found at Peel Island (Lat. 27" 31 ', Long 1 S3' 41') where a partially developed fringing reef is present. This island is in southern Moreton Bay and its position with reference to the adjoining mainland and to neighbouring islands is shown in Fig. 1. In early 1956 Professor W. Stephenson observed that many of the corals were dying and a brief note was pl)blished (Stephenson 1956). This mortality was further investigated in the present work to determine its extent and possible causes. The zonation and abundance of common organisms occurring amongst the corals was examined concurrently to determine whether they were similarly affected.

U METHODS The entire peripheral areas of Peel Island from the level of mean low water neap tide to the limit of distinct visibility (approx. 8 ft. below low water spring tides (L.W.S.) ) were examined. Horizontal distances were paced, or, where the water became too deep, estimated. The inaccnracies of these methods are obvious. Most of the species encountered were identified by comparison with named material housed in the Department of Zoology, University of Queensland. Due to the difficulty of sponge taxonomy and the lack of work on Australian sponges members of this phylum were largely left unidentified. Pachycha!ina elongata (Lendenleld) was identified by the author; Mr. T. Hailstone identified the two alcyonarians which are mentioned. 212 R. ]. SLACK-SMITH, B.Sc.

III PHYSICO-CHEMICAL FACTORS

Hedley (1925b), Crohamhurst Observatory (1926), Hynes (1951 ) , Rochford (1952), Wells (1954) and Endean, Kenny and Stephenson (1956) all ' make reference to physico-chemical factors operating in Moreton Bay.

Reviewing the existing data Wells (1954, p. 4) notes: (i) salinity changes are comparatively small although large amounts of water enter the bay from the Brisbane and Logan Rivers; (ii) scant information is available on the turbidity of the water and although the western side of the bay shows opacities varying from 1-5 metres (for a 27 in. Secchi disc) "the turbidity is probably less in the eastern parts of the bay where coral growth is stronger"; (iii) little is known about water currents; (iv) the substratum consists of mud, sand or shell and coral fragments ; and (v) the range of water temperatures is from 15'C to 27'C in the shallows, 17'C to 26'C in deeper waters.

IV DESTRUCTION OF CORALS

A close exa mination of the total coral fauna showed that only F m;ia speciosa (Dana) appeared to be affected. This is unexpected as its complete dominance in the bay would indicate that it is much the hardiest of the species present.

In order that the extent of the dam age to the corals could be estimated it was necessary to know (i) the density of corals in the areas around the island, and (ii) the proportion of colonies destroyed in these areas.

(i) Density of Corals

The percentage of area of the substratum covered by coral in a given locality was a scertained by a veraging the proportions so covered in iive randomly chosen three metre squares . In deeper water estimates replaced measurements. Table I lists the values recorded.

(ii) Destruction of Corals

Table I also records the areas where coral mortality occurred and the percentage of affected corals in the population. These values were determined by selecting, at random, five groups each of ten colonies. The number of abnormal corals was counted in each group, and then the overall percentage for the five groups found.

Dying polyps assumed a light grey-brown coloration and this colour change was used in the field as an indicator of their imminent death. Final death was recognised by decomposition of the coenenchyme, which eventually washed from the skeleton leaving it bare. Moorhouse ( 1936) records a similar death process in Por·itcs spp. caused by a lowered water level in moats at Low Isles, Great Barrier Red. AN INVESTIGATION OF CORAL DEATHS AT PEEL ISLAND 213

TABLE I Areas and Amounts of Coral and of Coral Damage

Percentage of bottom Percentage Area Substratum covered death by coral

A1 Broken coral and shell on muddy sand 40--50 30 A2 As Al .. 50--70 50----70 A3 Sandy mud .. 30---40 30 A4 Sandy with some broken coral and shell 40-50 20 A5 As A4 but more sand 20 10 A6 As Al 30--40 ao . . ..; � Bl . 30 50 B2 .., . . 10 10 B3 30 40 B4 40 20 c 60 20--30

Dl II 1J '' 10 80 D2 Sand with coral and shell fragments 30 0-10 D3 As Al . . 60 30 D4 As Al .. 50 50 El Muddy sand 20 70---100 E2 20 50--90 � Fl Sar{dy m1;d alt�r'natingwith muddy sand and fragments 40 40 60 F2 As Fl .. 50 60 5(f- .. 6o F3 ...... 40-50 F4 Sandy gravel with broken coral and shell .. 40 2o--ao Gl As F4 .. 50 70--80

G2 " JJ •• 40 70--80 . G3 Washed sand with coral and shell fragments . Too deep ---·------._-:.-_-::..==-==:::::::===----=:--======-==:-�--==10 = I to observe ! =------======---==--:=-=-··· ·------

V DEATH OF CORALS IN OTHER PARTS OF MORETON BAY

No systematic investigation was carried out, but one visit was made to each of the following areas :-Coochiemudlo Island, Macleay Island, Cassim Island, Raby Bay, D unwi ch , and Niyora.

Small cora ls were observed at Pat's Point, Macleay Island, 10% of which were totally or partially destroyed. The corals at all levels were similar to those found in the soft coral zone at Peel Island.

Quite robust growths of cor a ls were present at Cassim Island and Raby Bay. Ten per cent. of the corals at the first loca lity and 80% of those at the second were killed.

VI ZONATION OF THE LOWER LITTORAL AND SUB-LITTORAL AT PEEL ISLAND

The typical zonation of the dominant organisms was as shown in Fig. 3. Briefly these zones were: -

(a) Mussel Zone (L.W.N. to 6in. above L.W.S.).

The substratum consisted of sand, mud and sandy mud. A few loose plates of Acropora spp. were strewn about and specimens of Acropora, Favia and Euphyllia spp., still in situ, protruded through the surface. 214 R. ]. SLACICSMITH, B.Sc.

Almost every solid object was thickly covered .with clumps of the hairy mussel Trichornya hirsuta (Lamark). An abundance of small invertebrates was found within these clumps. Found commonly between these clumps were the pearl oyster Pinctada albina sugillata Reeve. The commercial oyster Crassostrea cornrnercialis (Iredale and Roughley), oflen extended into this zone.

(b) Mussel-Blacle Sponge Zone (6in. above L.W.S. to L.W.S.).

The substratum was identical with (a) above.

The mussel was slightly less abundant than in the prev1ous zone and a black encrusting monaxon sponge became co-dominant.

\c) Soft Coral Zone (L.W.S. to 6in. below L.W.S.).

Sandy, sandy mud, and mud, each with varying amounts of shell and coral fra gments, provided the substratum. The alcyonarian Micro.rpicularia pachyclados (Klunzinger) was dcminant and Xenia cylindric a Roxas very common. Small globular specimens of Favia Jj)eciosa were present in the lower third of this zone, no other coral s pecies being represented. Numerous sponges were encountered the commonest being Pach:ychalina elongata.

(d) Coral Zone (from 6in. below L.W.S. to limit of distinct vis ibility).

The substratum was sandy or sandy mud, with varying amounts of shell and coral fragments.

Corals dominated this zone and of these Favia .rpeciosa was completely dominant. The following species were also prcsent:---Favites abdita (Ellis and Solander); Acropora digiti/era (Dana);Favites A. specifera (Dana ); Psarnmocora ·vaughani Yabe, Sugiyama and Eguchi ; Cyphastrea serialis Forsbll; Goniopora lobata Milne Edwards and Bedot; halicora (Ehrenberg); Favia stelligera · (Dana) ; Turbinaria danae B ernard ; T. peltata Esper; and Euphyllia sp. (The Euphyllia is an additional record to Wells' 1954 list). Microspicularia and Xenia cylindrica were commonly attached to dead corals and dead portions of corals.

Several common sponges also occurred, the mos t prominent being

Pachychalina elongata and a red-mauve encrusting species with many high, circular oscula.

This zone extended commonly to lOft. below L.W.S., but its lower limit was probably nearer 15-20 ft.

A variation in this pattern occurred in current swept areas e.g. F2-3, C-Dl and G3, where the relative abundances of Aficrospicularia sp. and X enitJ cylindrica were reversed in the Coral Zone. AN INVESTIGATION OF CORAL DEATHS AT PEEL ISLAND 215

VII DISCUSSION

A. Zonation

At Dunwich, Moreton Bay (see Fig. 1) Endean, Kenny and Ste phenson (1956) recorded a mussel zone and stated that "Below L.W.S. (a zone of) soft coral and Sargassum sp. intermingled". This area is identical with area (c) at Peel Island.

Munro (1940) observed the following- zonation of the dominant animals on the lower beach at Green Island, Moreton Bay:-

Brachyodontes ( = Trichomya)';,Zone (below 2ft. above L.W.M.). Xenia Zone (below 6in. to L.W.M.).'' Alcyonium Zone (L.W.M. downwards). It can be seen that there are basic similarities between the zonations at Green and Peel fslands. However, the definite coral zone at Peel Island is represented by scattered corals which become very common only in the lower portion of Munro's Alcyonium zone. On the other hand at Peel Island Xenia becomes a dominant in the soft coral zone only where the zone is swept by strong currents.

A combination of observations at Peel, Cassim and Macleay Islands, Raby Bay and Myora, with those of the above authors yields the following typical zonation patterns:----

Mus.rel Zone (L.W.M. to 6in. above L.W.S.). Black Sponge-Mussel Zone (6in. L.W.S. to L.W.S.). Soft Coral Zone (L.W.S. downwards), with frequently a Madrepora Zone extending from L.W.S. downwards.

On the rocky ocean shores south of Moreton Bay the zone below L.W.N. differs in the dominance of algae and Pyura stolonifera (Dakin, Bennett and Pope (1948); Bennett and Pope (1953) and Endean, Kenny and Stephenson ( 1956) ) ; whereas north of Moreton Bay algae alone dominate (Endean, Kenny and Stephenson 1956; Endean, Stephenson and Kenny 1956).

The zonation at Peel Island is roughly similar to patterns described at Low Isles by Stephenson, Endean and Bennett ( 1958). At Low Isles a mussel zone, a soft coral zone and a coral zone are described but at different points on the island i.e. not contiguously. It should also be noted that the species comprising the zones at Low Isles were dissimilar, with a different mtissel, a greater variety of soft corals and with Favia Jpeciosa being far from the dominant coral species.

No significant deaths of any species other than Favia speciosa were observed during this study. It was noted that recently dead portions of corals were immediately colonised by filamentous algae. Portions longer dead showed considerable growths of larger algae, soft corals and occasionally mussels indicating a succession of colonizing species. 216 R. ]. SLACK-SMITH, B.Sc.

B. Coral Death and its Possible Cause

The destruction of the Peel Island corals, as described above, was probably caused by changes in the following environmental factors, either acting collectively or individually:--

(a) Temperature, (b) Turbidity, and (c) Salinity.

(a) Temperature

The fatalities occurred in summer indicating that low temperatures were not responsible. More than half the corals tested for heat-resistance by Edmondson (1928) died when subjected to a temperature of 32'C for 8 hours; the family Faviidae being most resistant. A maximum water temperature exceeding 33'C has been recorded at low tide on the reef flat at Heron Island, Great Barrier Reef by Woodland (personal communication). No damage to corals, especially to Favia sp,eciosa, which is moderately common at Heron Island, was observed.

The maximum recorded water temperature in the shallow waters of Moreton Bay is 27'C. It is possible that temperatures higher than this value have occurred as the records were taken only spasmodically by Hedley (1925b) and Rochford (1950) and did not include the 1951-56 period. It is unlikely that

the temperatures over this period· reached a fatal value and caused the deaths described above.

(b) Turbidity

Edmondson (192tl) records that certain members of the family Faviidae are unaffected by five days complete burial in silt. Endean, Kenny and Stephenson (1956, p. 13tl) comment:--- "Turbidity as a factor primarily responsible for the paucity of corals on the (Queensland) mainland can be dismissed, because the water in localities where corals are found was just as turbid as in other localities where corals were absent". At Cassim Island, healthy corals were observed which has been three-fourths buried under silt for at least two weeks.

It seems unlikely that excessive turbidity in early 1956 had any considerable bearing on the coral deaths at Peel Island

The literature records many instances of fresh waler killing marine orgamsm�. Fischer--Piette (1931) notes the death of estuarine ascidians and sponges m northern France after excessive flooding. At Stone Island, near Bowen, Queensland, Hedley (1925a) recounts the complete destruction of the marine fauna following heavy cyclonic rains producing local flooding and excessive outflow from the adjacent rivers. Endean, Kenny and Stephenson (1956, p. 138) record similar destruction at Coral Point near Mackay, Queensland in 1951. Snelling (1959) has records of spectacular variations in the degree of penetration of marine crabs into the Brisbane River estuary which are correlated with droughts and floods respectively. Fairbridge and Teichert (1947, .1948) record coral death at Low Isles by excessive flooding from the Daintree River in 1945. The subject of coral deaths at Low Isles is discussed and reviewed by Stephenson, Endean and Bennett (1958). AN INVESTIGATION OF CORAL DEATHS AT PEEL ISLAND 217

Edmondson (1928) records that certain reef corals, chiefly members of the family Favi idae, can live unharmed in a 66 2/3% solution of seawater (approx. 13 Cl0/00 ) , but die in about four days if placed in a 50% solution (approx. 10 Cl0/00 ).

During the early summer of 1956 the Brisbane Weather Bureau recorded the highest rainfall for 27 years over this peri od. Correspondingly high falls were recorded at Peel Island over the same period.

Possible methods by which this rainfall could have caused coral damage are:-

(a) direct rainf a ll on specimens. at lmv tide;

(b) dilution of water in the irnmediate vicinity of corals by drainage from the upper beach; and

As this rain coincided with a period of neap tides it is unlikely that (a) would apply.

It is possible that (b) caused some of the above effects, at least initi ally because Stephenson (1956) notes that: ..."Corals high up the beach have been destroyed, seemingly by fre s hwater, apparently in drainage channels from the upper beach". Some six weeks later there was no localization as Stephenson noted, but instead widespread destruction. The slower and more widespre ad destruction was eventually the more important.

In 1 950 variations in the outflow from the Brisbane and Logan Rivers were responsible for the following sali nity records, in Moreton Bay localities (Rochford 1952) ;-·

------·--·--- Locality Variation in Cl"/00 .. ----- Dunwich oyster lease 19.27----13.27 Channel between Dunwich and Peel I. 19.60--18.54 Channel between Cleveland and Peel I. 19.50-16.66 Channel at Pat's Point (Madeay I.) 19.57--16.10 Channel at Pannikin I. 19.64--12.27

These results were obtained at intervals ranging from one to two· months and the salinity changes between these periods could have been much greater.

Records obtained at the Peel Islan d Hansen's Disease Settl e ment show that particularly heavy rain fell during 7-lOth (11.07 ins .) and 18-20th February 1956 (unrecorded).

These facts indicate that dilution of Moreton Bay water by excessive outflow from the Logan and B risbane Rivers, is the likely cause for most of the coral deaths in 1956, with a probability of initial damage due to drainage from the upper beach. 218 R. ]. SLACK-SMITH, B.Sc.

VIII ACKNOWLEDGEMENTS

The author is deeply grateful to Professor W. S tep henson , Dr. R. Endean and Dr. M. C. Bleakly for supervision and guidance in the execution and presentation of this research. P rofessor S tephenson read the manuscript and suggested many improvements.

Sincere thanks are due to the Department of Health and Home Affairs and to the staff and patients of the Peel Island Hansen's Disease Settlement for the provision of accommodation a1�d transport. Parti cularly thanks are due to Dr. M. H. Gabriel, Matron Ahlburg and Mr. C(:m Burns.

Assistance has been provided by Mr. B. Campbell and Mr. C. Illidge of the Queensland University techn ica l staff.

Finance for this research was provided from research project moneys of the University of Queensland. AN INVESTIGATION OF CORAL DEATHS AT PEEL ISLAND 219

IX REFERENCES

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RoCHFORD, D. J. (1952). "Estuarine hydrological investigations in eastern and south-eastern Australia." C.S..T.R.O. Aust. Div. Fish. Oceanogr. Sta. List invest., 5. 1-150

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FIG. I

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ISLAND £R BRIS!lAN£ RlV

I. · CCOCHlEMUDI.ll

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LOGAN RIVER

z o . o o o �--��·------SCA I.E , 40,000 ft AN INVESTIGATION OF CORAL DEATHS AT PEEL ISLAND 221

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. . LC-MT, B.Sc. SLACK-SMITH, J. R. 222