Enhanced particle-feeding capacity of corals on turbid reefs (Great Barrier Reef, Australia)

Reef corals occur across a wide range of habitats, from offshore clear waters to nearshore sediment-laden environments. This study tests the hypothesis that corals from turbid nearshore areas have greater capacity to utilise suspended sediment as a food source than conspecifics from less turbid and midshelf areas. The hypothesis was tested on two common and widespread coral species on the Great Barrier Reef (Pocillopora damicornis and Acropora millepora). The particle clearance rates of samples from more turbid reefs were two-fourfold those of conspecifics from less turbid and midshelf reefs. Rates of sediment ingestion were generally a linear function of sediment load indicating no significant saturation within the concentration range of 1–30 mg dry weight l⁻¹. Estimated assimilation efficiency of particulate ¹⁴C varied between 50 and 80%, and was maximised for midshelf A. millepora at the lowest sediment concentration, suggesting that heterotrophy is more efficient in oligotrophic habitats. Based on feeding-response curves, assimilation efficiencies, and published records of ambient particle concentrations, representatives of these species on turbid inshore reefs are 10–20 times more heterotrophic on suspended sediment than their conspecifics on less turbid and midshelf reefs. Accepted: 7 September 1999     

Behaviour, growth and survival of redfish larvae in relation to prey availability

Growth, survival and condition of redfish larvae Sebastes spp., reared in the laboratory (0, 500 1500 and 4500 prey l^-1) were highest in the 1500 prey l^-1 treatment. Significantly lower larval growth and survival in the 4500 prey l^-1 treatment corresponded with lower prey bite: orient ratios in later weeks, suggesting that larvae were unable to forage efficiently at high prey densities. While these prey densities are higher than those reported in the field, naturally co-occurring Atlantic cod Gadus morhua larvae require higher prey densities when reared under similar conditions in the laboratory. These data suggest that prey availability may not be as limiting to redfish as for other commercially important marine species.     

Experimental studies on microbial bioerosion at Lee Stocking Island, Bahamas and One Tree Island, Great Barrier Reef, Australia: implications for paleoecological reconstructions

Different kinds of experimental calcareous substrates were exposed at Lee Stocking Island (Bahamas) and One Tree Island (Great Barrier Reef, Australia) to study which endolithic bacteria, algae and fungi contribute to bioerosion and what their bioerosion rates are. The sites at Lee Stocking Island were several leeward shallow water and several windward shallow and deep-water positions (from the Acropora palmata reef at 2 m down to 275 m depth). At One Tree Island, the experiments were conducted in patch reefs treated with P and N to study the influence of mineral nutrients on bioerosion. The exposure periods ranged from 1 week to 2 years. The micritic carbonate substrates exposed on Lee Stocking Island contained 6 genera with 15 species of cyanobacteria, green and red algae, and different kinds of microendolithic heterotrophs. The mean values of bioerosion rates measured between 1 to 2 g/m²/y at 275 m and 520 g/m²/y at one of the leeward sites. The composition of the endolithic community and the bioerosion rates changed over time. At One Tree Island, shell pieces of Tridacna were used as substrate exposed for 5 months to endolith activity. Five genera and 6 species of cyanobacteria, green and red algae and different kinds of heterotrophic microendoliths were found with bioerosion rates of 20-30 g/m²/y. There are differences in abundance of taxa between Lee Stocking Island and One Tree Island. The introduction of nutrients had no apparent impact on the microborer community. Controlling factors for the distribution and abundance of microborers are mainly light, but also the kind of substrate and, possibly, the biogeographic position. The results support the paleoecological importance of microendoliths.     

Distributional ecology of milkfish,Chanos chanos,larvae in the Great Barrier Reef and Coral Sea near Lizard Island,Australia

Synopsis Plankton hauls captured 682 milkfish larvae (2.1–12.3 mm) in the Great Barrier Reef Lagoon and Coral Sea during 1979–1986. Larvae were present from November to March, and absent in April, July and October. We analyzed concentration, abundance and size-frequency data and concluded that spawning took place in the Coral Sea or at the outer edge of the continental shelf, apparently following an adult spawning migration of at least 50 km. Larvae then moved inshore to at least our most inshore routine sampling site near midshelf. Some larvae may have remained for a period in the lee of reefs along the shelf edge. Larvae apparently occupied the upper few metres of the water column, thereby becoming susceptible to shoreward movement in the wind-driven surface layer. Movement from spawning sites to midshelf probably required active maintenance of vertical position by larvae which enabled passive movement with favourable currents, and perhaps horizontal swimming. By the time larvae reach midshelf, continued inshore movement by horizontal swimming alone is possible.     

Zoanthids (Anthozoa, Hexacorallia) from the Great Barrier Reef and Torres Strait, Australia: systematics, evolution and a key to species

 Zoanthid taxonomy is currently in a state of chaos, with many described species very few of which can be reliably identified. As part of a genetically based, objective reappraisal of the number of northern Australian species, a total of 355 zoanthid specimens were collected from 19 localities in the Great Barrier Reef and Torres Strait during 1992–1994. Specimens, initially assigned to one of ten morphological or ecological forms, were subjected to allozyme electrophoretic analysis. Analysis of genetic data revealed only seven discrete (i.e., non-interbreeding) groups in the family Zoanthidae. These groups, which are delimited by fixed gene differences, are considered species under a biological species concept. Some species show considerable morphological variation and have broad environmental tolerances. We provide the first key to Great Barrier Reef zoanthid species based on our results and observations. Species can be differentiated in the field on the basis of gross colony morphology, sand encrusting habit, polyp form and habitat. Genetic data are also used to generate a phylogenetic hypothesis of relationships among the Zoanthidae, which is compared to previous morphologically based systems. Division of the group on the basis of mesenterial arrangement appears justified, but nematocyst data appear less valuable in phylogenetic studies of the group than has been suggested previously. Accepted: 29 January 1996     

Reproduction and growth of Craterocephalus marjoriae and C. stercusmuscarum (Pisces: Atherinidae) in south-eastern Queensland, Australia

SUMMARY. 1. The reproductive cycle and growth of Craterocephalus marjoriae and Craterocephalus stercusmuscarum (Atherinidae) were studied in Brisbane, south-eastern Queensland, over a 17-month period (1981–82).
2. Both species had a 5-month breeding season in spring and summer, with a breeding peak in spring (September-October). Multiple spawning occurred but life time fecundity was not determined.
3. Gonosomatic index values and mean fecundity per female were higher in Craterocephalus marjoriae than in C. stercusmuscarum. Fecundity increased with body length in both species according to the relationship, F=aL^b. Growth rates were similar and growth was adequately described by the von Bertalanffy equation. Both species grew rapidly during the first year and reached maturity the following season. Reproductive strategies are considered in relation to seasonal flooding in the streams inhabited.     

Modern cryptic microbialite/metazoan facies from Lizard Island (Great Barrier Reef,Australia) formation and concepts

Summary From shallow water caves of fringing reefs related to continental islands of the Lizard Island Section thrombolitic micritic microbialites were observed. The microbialites exhibit always a light decreasing facies succession. The succession starts with a coralgal community and ends with light independent microbial biofilms and benthos (coralline sponges). The sessile mineralized benthos community is constructed of crustose foraminifera, serpulids, thecidean brachiopods, bryozoans, and coralline sponges. The observed benthic community is very similar to those one observed in cryptic habitates of Aptian and Albian reefs of northern Spain. For longtime studies of the microbialite formation and growth rates of coralline sponges the specimens were stained in vivo, within their natural habitat with histochemical fluorochromes and nonfluorescent agents. Main results are a very slow growth of the microbialite and associated sponges (50–100 μm/y). Only few calcifying microbes are participators during microbialite formation. Calcifying acidic organic macromolecules are mainly responsible for microbialite formation by cementing detritical material. Fe/Mn-bacterial biofilms are responsible for strong corrosion of the microbialite. Beside the corrosive activity of the Fe/Mn-bacterial biofilms boring sponges (Aka, Cliona) are the main destructors. Geochemically the observed microbialites are composed of mainly high-Mg calcites and exhibit high positive δ¹³C (+3 to +4) values.     

Coastal climate of northwest Australia and comparisons with the Great Barrier Reef: 1960 to 1992

 Significant coral reef ecosystems occur along the northwest (NW) coast of Australia in an oceanographic setting somewhat similar to that of the Great Barrier Reef off the northeast (NE) Australian coast. Seasonal and inter-annual variations of several surface climate variables are described for the NW coastal region of Australia from 10^°–30^°S over the period 1960 to 1992. Average climatic conditions in this region are compared with those for similar latitudes on the Great Barrier Reef. On average, sea surface temperatures (SSTs) along the NW Australian coast are warmer than at similar latitudes along the NE coast north of ∼20^°S and cooler than the NE coast at higher latitudes. The annual range of SSTs along the NW coast is lower than found along the NE coast. There is also lower average cloud amount (and greater incoming solar radiation) along the NW coast compared with the NE coast. Corals reefs off the NW Australian coast are less likely to be influenced by freshwater and associated terrestrial impacts than nearshore reefs of the GBR. Although the latitudinal distribution of tropical cyclone activity is similar along the NW and NE Australian coasts, the total number of tropical cyclones and tropical cyclone days is substantially higher on the NW coast compared with the NE coast. Accepted: 22 June 1998     

Reproduction of the inshore coral trout Plectropomus maculates (Perciformes: Serranidae) from the Central Great Barrier Reef, Australia

The reproductive biology of the serranid fish Plectropomus maculatus sampled from inshore waters of the Central Great Barrier Reef was studied based on histological analyses of gonad material. This species was shown to be a monandric protogynous hermaphrodite. The process of sex change foliowed the spawning period observed during September through November. Plectropomus: maculatus showed multiple spawning during this period. Sex change followed the usual protogynous mode with degeneration of ovarian germinal tissue accompanied by proliferation of male germinal tissue in the gonad. The sex structure of the sampled population was analysed based on age and size information. The size and age of first reproduction for females was 30.0cm s. L. and 2 years of age. The size and age of sex-transition was 35.4 cm s. L. and 4.4 years of age. The sex/size and sex/age relationships indicated that sex-change can occur over a broad range of sizes and ages. The sizes and age distributions of males and females P. maculates overlapped over 38% of the length range and over 42% of the maximum age observed.     

The cercaria of Galactosomum bearupi Pearson, 1973 (Trematoda: Heterophyidae) at Heron and Masthead Islands,Great Barrier Reef,Australia

Magnacercous cercariae, all morphologically identical but with different coloured tails, were found naturally infecting the intertidal prosobranch gastropod Clypeomorus batillariaeformis Habe & Kosuge (Cerithiidae) at Heron and Masthead Islands. Several species of coral-dwelling fishes were exposed to magnacercous cercariae. Active ingestion by the fish, followed by the complete development of the metacercaria in the optic lobes, occurred in Pomacentrus molluccensis Bleeker, but not in Dascyllus aruanus (L.), where development stopped short after encystment. All cercariae turned out to belong to the same species, Galactosomum bearupi Pearson, 1973. Natural infections of G. bearupi metacercariae were found in eight species of fish at Heron Island: Pomacentrus molluccensis, P. wardi Whitley, P. bankanensis Bleeker, P. flavicauda Whitley, Stegastes cf. fasciolatus (Ogilby), Sillago maculata Quoy & Gaimard, S. cf. ciliata Cuvier and Crenimugil crenilabris (Forsskål). This represents the fourth account of the cercaria of a species of Galactosomum.     

Identical digeneans in coral reef fishes from French Polynesia and the Great Barrier Reef (Australia) demonstrated by morphology and molecules

Three coral reef fish species, Zanclus cornutus, Chaetodon vagabundus and Naso lituratus, were collected in French Polynesia and on the Great Barrier Reef, Queensland. These fish species were each infected by one morphologically similar digenean species in both localities; Schistorchis zancli Hanson, 1953 was found in Zanclus cornutus, Preptetos laguncula Bray and Cribb, 1996 in Naso lituratus and Neohypocreadium dorsoporum Machida and Uchida, 1987 in Chaetodon vagabundus. In addition, on the Great Barrier Reef P. laguncula was also found in Naso unicornis and N. dorsoporum in Chaetodon ephippium and Chaetodon flavirostris. Morphometric differences between the species from the two sites were only slight. Sequences from the second internal transcribed spacer of the ribosomal DNA of each worm revealed total homology or negligible divergence between samples from hosts caught in French Polynesia and on the Great Barrier Reef. These results show that across more than 6000 km these digeneans are similar in morphology and genotype. Some species of fishes and molluscs are considered to have distributions that encompass the entire tropical Indo-West Pacific. These findings suggest that at least some of their parasites have similarly broad distributions.     

Symbiodinium (Dinophyceae) community patterns in invertebrate hosts from inshore marginal reefs of the southern Great Barrier Reef,Australia

The broad range in physiological variation displayed by Symbiodinium spp. has proven imperative during periods of environmental change and contribute to the survival of their coral host. Characterizing how host and Symbiodinium community assemblages differ across environmentally distinct habitats provides useful information to predict how corals will respond to major environmental change. Despite the extensive characterizations of Symbiodinium diversity found amongst reef cnidarians on the Great Barrier Reef (GBR) substantial biogeographic gaps exist, especially across inshore habitats. Here, we investigate Symbiodinium community patterns in invertebrates from inshore and mid‐shelf reefs on the southern GBR, Australia. Dominant Symbiodinium types were characterized using denaturing gradient gel electrophoresis fingerprinting and sequencing of the ITS2 region of the ribosomal DNA. Twenty one genetically distinct Symbiodinium types including four novel types were identified from 321 reef‐invertebrate samples comprising three sub‐generic clades (A, C, and D). A range of host genera harbored C22a, which is normally rare or absent from inshore or low latitude reefs in the GBR. Multivariate analysis showed that host identity and sea surface temperature best explained the variation in symbiont communities across sites. Patterns of changes in Symbiodinium community assemblage over small geographic distances (100s of kilometers or less) indicate the likelihood that shifts in Symbiodinium distributions and associated host populations, may occur in response to future climate change impacting the GBR.     

Batch fecundity of Lutjanus carponotatus (Lutjanidae) and implications of no-take marine reserves on the Great Barrier Reef, Australia

This study investigated body size to fecundity relationships of a reef fish species targeted by line fishing, and examines the potential benefits of increased batch fecundity in no-take reserves compared to fished areas around the Palm, Whitsunday and Keppel Island Groups, Great Barrier Reef, Australia. Lutjanus carponotatus batch fecundity increased with fork length in a non-linear relationship that was best described by a power function. Batch fecundity differed by more than 100-fold among individuals, with a range from 7,074 to 748,957 eggs in fish ranging from 184 to 305 mm fork length. Furthermore, egg diameter increased with fish size. Based on underwater visual census, the potential batch fecundity per unit area in all three island groups ranged from 1.0 to 4.2 times greater in the no-take reserves than in the fished areas between 2001 and 2004. In 2002, a mean 2.3-fold difference in biomass between no-take reserves and fished areas converted to a mean 2.5-fold difference in batch fecundity per unit area. Greater batch fecundity, longer spawning seasons and potentially greater larval survival due to larger egg size from bigger individuals might significantly enhance the potential benefits of no-take marine reserves on the Great Barrier Reef.     

A new genus and species of cryptogonimid from Lutjanus spp. (Pisces: Lutjanidae) on the Great Barrier Reef and New Caledonia

Lobosorchis tibaldiae n. gen. and n. sp. (Digenea: Cryptogonimidae) is described from the intestine, pyloric ceca, and rectum of 2 species of Lutjanus (Pisces: Lutjanidae), Lutjanus carponotatus and Lutjanus fulviflamma, from the Great Barrier Reef, Queensland, Australia, and New Caledonia. The genus is tentatively placed in the Neochasminae and is distinguished within the Cryptogonimidae by the combination of follicular testes, oral spines, and vitelline follicles restricted to the anterior region of the body not extending posteriorly to the ventral sucker.     

Trematodes of the Great Barrier Reef,Australia: emerging patterns of diversity and richness in coral reef fishes

The Great Barrier Reef holds the richest array of marine life found anywhere in Australia, including a diverse and fascinating parasite fauna. Members of one group, the trematodes, occur as sexually mature adult worms in almost all Great Barrier Reef bony fish species. Although the first reports of these parasites were made 100 years ago, the fauna has been studied systematically for only the last 25 years. When the fauna was last reviewed in 1994 there were 94 species known from the Great Barrier Reef and it was predicted that there might be 2,270 in total. There are now 326 species reported for the region, suggesting that we are in a much improved position to make an accurate prediction of true trematode richness. Here we review the current state of knowledge of the fauna and the ways in which our understanding of this fascinating group is changing. Our best estimate of the true richness is now a range, 1,100–1,800 species. However there remains considerable scope for even these figures to be incorrect given that fewer than one-third of the fish species of the region have been examined for trematodes. Our goal is a comprehensive characterisation of this fauna, and we outline what work needs to be done to achieve this and discuss whether this goal is practically achievable or philosophically justifiable.     

Characterization of Gambierdiscus lapillus sp. nov. (Gonyaulacales,Dinophyceae): a new toxic dinoflagellate from the Great Barrier Reef (Australia)

Gambierdiscus is a genus of benthic dinoflagellates found worldwide. Some species produce neurotoxins (maitotoxins and ciguatoxins) that bioaccumulate and cause ciguatera fish poisoning (CFP), a potentially fatal food‐borne illness that is common worldwide in tropical regions. The investigation of toxigenic species of Gambierdiscus in CFP endemic regions in Australia is necessary as a first step to determine which species of Gambierdiscus are related to CFP cases occurring in this region. In this study, we characterized five strains of Gambierdiscus collected from Heron Island, Australia, a region in which ciguatera is endemic. Clonal cultures were assessed using (i) light microscopy; (ii) scanning electron microscopy; (iii) DNA sequencing based on the nuclear encoded ribosomal 18S and D8‐D10 28S regions; (iv) toxicity via mouse bioassay; and (v) toxin profile as determined by Liquid Chromatography‐Mass Spectrometry. Both the morphological and phylogenetic data indicated that these strains represent a new species of Gambierdiscus, G. lapillus sp. nov. (plate formula Po, 3′, 0a, 7″, 6c, 7‐8s, 5?, 0p, 2″″ and distinctive by size and hatchet‐shaped 2′ plate). Culture extracts were found to be toxic using the mouse bioassay. Using chemical analysis, it was determined that they did not contain maitotoxin (MTX1) or known algal‐derived ciguatoxin analogs (CTX3B, 3C, CTX4A, 4B), but that they contained putative MTX3, and likely other unknown compounds.     

Contrasting patterns of reef utilization and recruitment of coral trout (Plectropomus leopardus) and snapper (Lutjanus carponotatus) at One Tree Island, southern Great Barrier Reef

Patterns of abundance, age structure and recruitment of coral trout (Plectropomus leopardus) and snapper (Lutjanus carponotatus) were described in different environments, which varied in benthic cover, in a 12-yr study at One Tree Island. It was hypothesized that both taxa would show strong preferences to different environments and benthic cover and that patterns would be consistent through time. Plectropomus leopardus were abundant on the reef slope and seaward edge of the lagoon, where live coral cover was high, and recruitment was generally low, in all environments. The population was sustained by a trickle of recruits, and total abundance varied little after 10 to 25 yr of protection in a no-take area, suggesting P. leopardus had reached an environment-related carrying capacity. Protogynous P. leopardus recruited to shallow environments at sites with 20% or more hard live coral and age data indicated the abundance of fish on the reef slope was from redistribution. Most recruits of gonochoristic L. carponotatus (<150 mm Standard length, SL) were found in the lagoonal environments, and adults were rare on the reef slope. Abundance of recruit L. carponotatus and P. leopardus did not correlate with percent cover of live and soft coral within environments. Recruits of L. carponotatus were usually rare in all lagoonal environments, but in 2003, many recruits (80 to 120 mm SL) were found in lagoonal environments with low and high hard live coral cover. A substantial proportion of the population (age max 18 yr) was from strong recruitment events. In 2003 and 2004, total abundance of L. carponotatus was supported by 1 year class 51.7 and 41% respectively. The utilization of environments and types of substrata varied among taxa and in some cases among life-history stages. There was also temporal variation in the importance of some environments (e.g. Lagoon Centre).