SOUTH AUSTRALIAN FOULING BRYOZOANS

Transcription

1 SOUTH AUSTRALIAN FOULING BRYOZOANS Brian J. Brock Faculty of Art, Design and Applied Science, South Australian College of Advanced Education, Holbrooks Road, Underdale, South Australia 5032 ABSTRACT Important fouling species were determined during the course of settlement experiments near Port Adelaide between 1975 and Colonies were obtained from experimental tiles and other surfaces at a thermally enhanced site near a power station, and at a control cold water site nearby. Major fouling species observed were Bowerbankia gracilis, Bugula neritina, B. stolonifera, Cryptosula pallasiana, Schizoporella errata, Scrupocellaria bertholettii, Watersipora subovoidea, and Zoobotrvon verticillatum. Minor fouling species observed were Bugula flabellata, Bugula simplex, Tricellaria porteri and Watersipora arcuata. Collections made during 1983 indicate that Watersipora arcuata is now a major fouling species in South Australian waters. I NTRODUCTION Port Adelaide has been the most important port for South Australia since the founding of the colony in A map from 1841, based on surveys by Commander Stokes on the Beagle, shows the mangrove lined shores of the Port River and adjacent waters. Mangroves (Avicennia marina var. resini fera (Forst. f.) Bakh. v.d. Brink (1921)) still thrive around much of the shoreline of Torrens Island and Garden Island. Discharge of heated effluent from the Torrens Island Power Station has made Angas Inlet pseudo-tropical and warmer-water fouling species flourish on small boats moored there. There have been several studies of fouling in the Port Adelaide region and Angas Inlet in particular (Brock 1980, Chittleborough 1952, Host 1977, Neverauskas 1977, Zed 1972), but there has been some uncertainty about the bryozoan species present. This paper aims at reducing that uncertainty. The dynamics of invasion by Watersipora arcuata warrants further study. SITES AND CONDITIONS My work on the South Australian fouling bryozoans has been concentrated in the Royal South Australian Yacht Squadron basin at Outer Harbour (cold water site), and at the Small Boat Sailing Club's moorings in Angas Inlet (warm water site). Point Turton on Southern Yorke Peninsula, and Coffin Bay on Southern Eyre Peninsula are other sites at which Watersipora arcuata was collected early in 1983 (Fig. 1). During the course of settling experiments carried out in (Brock 1980) surface water temperature was C at the Outer Harbour site, and C at the Angas Inlet site. Salinities were %, at Outer Harbour and %) at Angas Inlet. Water movement was generally greater at Angas Inlet because of the continuous flow of effluent from the power station. The tidal range is about two metres.

2 46 BRIAN J. BROCK THE FOULING SPECIES Watersipora is one of the most important genera of fouling Bryozoa in South Australia. Watersipora arcuata Banta and Watersipora subovoidea (d'orbigny) (Fig. 2A-B) both settled on tiles immersed at Outer Harbour and at Angas Inlet. W. arcuata was more abundant than W. subovoidea at the Outer Harbour site, but W. subovoidea was the more abundant of the two species at Angas Inlet (on boats, pontoons and tiles). Collections during May 1983 indicate that a change in relative abuddance may have occurred. Watersipora subovoidea was rare in both hot and cold water sites near Garden Island whereas W. arcuata was abundant on old hulks, mangrove logs and rocks near low tide level. W. arcuata was the only Watersipora species found on jetty piles at Point Turton and on lower intertidal rocks near Coffin Bay early in It is the species Skerman (1960a) recorded as a recent invader of Auckland Harbour. Ryland (1974) records it for Sydney Harbour, where Wisely (1958) studied it as a component of the fouling fauna. Bok (1982) refers to it as `a significant component of the fouling community'. The earliest specimen I have was collected on a seasquirt at Outer Harbour on 17.xii.70. Ten collections of fouling bryozoans from boats and pontoons in Angas Inlet during 1975 contained only Watersipora subovoidea. Cryptosula pallasiana ( Moll.) and a Schizoporella species are other encrusting species common in the fouling community in South Australia. Schizoporella unicornis (Johnston) is the species traditionally recorded in the Australian fouling fauna (Allen 1953, Wood & Allen 1958, Russ & Wake 1975). Clear drawidgs of S. unicornis and S. errata ( Ryland 1965, Ryland 1971, Haywood & Ryland 1979) lead me to question whether the Adelaide species is S. unicornis. Specimens collected from pontoods in Angas Inlet on 25.ii.77 ( Fig. 2C) and an ovicellate specimen (Fig. 2D) found on a dead mangrove branch in the

3 SOUTH AUSTRALIAN FOULING BRYOZOANS 47 Fig. 2. A, Watersipora arcuata, North Arm hulk, 17.v.1983; B, W. subovoidea, North Arm hulk, 17.v.1983; C, Schizoporella errata from pontoons, Angas Inlet, 25.ii.1977; D, S. errata, an ovicellate specimen from an old mangrove branch, Angas Inlet, 17.v.1983; E, Cryptosula pallasiana from pontoons, Angas Inlet; F, C. pallasiana part of a colony showing several zooids with avicularia, from pontoons, Angas Inlet (the 1 mm scale). warm waters of Angas Inlet in May 1983 look more like S. errata ( Waters). The mangrove branch was thickly covered with Schizoporella and Bugula neritina. I have collected Cryptosula pallasiana on boats, pontoons, oysters, and cement aggregate tiles at Angas Inlet, and on pontoons and tiles at Outer Harbour (Fig. 2E-F). It is well known as a fouling species (Woods Hole Oceanographic Institution 1952, Skerman 1960b, Ryland 1965, Hayward & Ryland 1979, Bok 1982). Two stoloniferous ctenostomes occur in the Adelaide fouling fauna. One appears to be Bowerbankia gracilis Leidy (Fig. 3D-E). The other is Zoobotryon verticillatum (delle Chiaje). Both occur at Outer Harbour and Angas Inlet. Zoobotryon grows rapidly in the warmer weather, festooning pontoons, boats, buoys, and hulks. Other fouling bryozoans settle readily on the branches of the colony (e.g., Watersipora subovoidea, Scrupocellaria bertholettii, Bugula neritina and Bugula stolonifera). Masses of Zoobotryon are commonly torn loose and become stranded amongst the mangrove pneumatophores on Garden Island. It was found growing on sponges in warm shallow bays near Coffin Bay in March Bushy anascan cheilostomes that are major fouling species near Adelaide are Bugula neritina ( Linnaeus), B. stolonifera Ryland, and Scrupocellaria bertholettii ( Audouin). The two Bugula species are common at both sites but S. bertholettii ( Fig. 3A-C) was more abundant at the warm water site. I have seen numerous B. stolonifera ancestrulae (Fig. 3F) but no B. avicularia ancestrulae while analysing tiles and other substrates. I believe that many of the reports of B. avicularia in Australian waters in fact refer to B. stoloni-

4 4 8 BRIAN J. BROCK Fig. 3. A-C, Scrupocellaria bertholettii, A, lateral view of ancestrula, B, frontal view of two-zooid stage, C, part of an older ovicellate colony; D-E, Bowerbankia gracilis, D, zooid arrangement along stolons, E, one zooid detached showing a tail; F-G, Bugula stolonifera, F, ancestrula and basal part of a young colony, G, part of an ovicellate colony; H, Tricellaria porteri part of a colony, bifurcate bottom outer spines and other scutum shapes. All scales are 200 µm. fera. Ryland & Hayward (1977) comment that confusion between the two species is common. S. bertholettii forms dense crusty bushy mats on pontoons and boats in Angas Inlet at the peak of its season. Densities on settlement tiles were as high as ten colonies per square centimetre. A minor fouler at Outer Harbour was Tricellaria porteri (MacGillivray) (Fig. 3H). It was not recorded at Angas Inlet. Bugula flabellata ( Thompson in Gray) and Bugula simplex Hincks were also minor foulers. CONCLUSION South Australia's fouling bryozoan fauna includes several cosmopolitan species. It is probable that these have been introduced during our 150 years of shipping history. The invasion appears to be continuing.

5 EVOLUTION OF PARVOHALLOPORA 49 REFERENCES Allen, F.E Distribution of marine invertebrates by ships. - Aust. J. Mar. Freshwat. Res. 4: Bok, P. E Bryozoans (phylum Bryozoa or Ectoprocta). - In S.A. Shepherd & I. M. Thomas (eds): Marine Invertebrates of Southern Australia. Part 1, pp Government Printer, South Australia. Brock, B.J Biology of Bryozoa involved in fouling at Outer harbour and Angas Inlet. - Unpublished M. Sc. thesis. University of Adelaide. Chittleborough, R. G Marine fouling at Port Adelaide, South Australia. -Unpublished M. Sc. thesis. University of Adelaide. Hayward, P.J. & J.S. Ryland British Ascophoran Bryozoans. - Synopses B. Fauna, N.S. 14: Host, W. M Marine biological studies in relation to the operation of the Torrens Island Power Station. - Unpublished M. Sc. thesis. University of Adelaide. Neverauskas, V.P Some biological effects from warm effluent water discharged from the Torrens Island Power Station. - Unpublished M. Sc. thesis. University of Adelaide. Russ, G.R. & L.V. Wake A manual of the principal Australian marine fouling organisms. - Report 644 of the Materials Research Laboratories, Maribyrnong, Victoria. Ryland, J.S Catalogue of main marine fouling organisms. 2, Polyzoa, O.E.C.D. Paris. Ryland, J.S Bryozoa (Polyzoa) and marine fouling. - In E.B. Gareth Jones & S.K. Eltringham (eds): Marine Borers, Fungi and Fouling Organisms of Wood, pp O.E.C.D., Paris. Ryland, J.S Bryozoa in the Great Barrier Reef Province. - Proc. Second Internat. Coral Reef Symp. 1: Ryland. J.S. & P.J. Hayward British Anascan Bryozoans. - Synopses B. Fauna, N.S. 10: Skerman, T.M. 1960a. The recent establishment of the Polyzoan Watersipora cucullata (Busk) in Auckland Harbour, New Zealand. - N.Z. J. Sci. 3: Skerman, T.M. 1960b. Ship fouling in New Zealand waters. - N.Z. J. Sci. 3: Wisely, B Settling and experimental reactions of larvae of Watersipora cucullata. - Aust. J. mar. Freshwat. Res. 9(3): Wood, E.J.F. & E. Allen Common marine fouling organisms of Australian waters. - Department of the Navy, Melbourne. Woods Hole Oceanographic Institution Marine Fouling and its Prevention. - U.S. Naval Institute, Annapolis. Zed, P.A The effect of warm water from the Torrens Island Power Station on the marine fauna of Angas Inlet. - Honours Zoology thesis. University of Adelaide.