Holocene evolution of the granite based Lizard Island and MacGillivray Reef systems, Northern Great Barrier Reef

Radiocarbon dating of seven drill cores from both the windward Lizard Island fringing reef and the windward and leeward margins of MacGillivray platform reef, Northern Great Barrier Reef Province, reveal the Holocene evolution of these two mid shelf coral reefs. The windward margin at Lizard Island started growing approximately 6,700 calendar years before present (cal yr BP) directly on an assumed granite basement and approached present day sea level approximately 4,000 cal yr BP. Growth of the windward margin at MacGillivray Reef was initiated by 7,600 cal yr BP and approached present day sea level by approximately 5,600 cal yr BP. The leeward margin at MacGillivray was initiated by 8,200 cal yr BP also directly on an assumed granite basement, but only approached sea level relatively recently, between 260 and 80 cal yr BP. None of the cores penetrated the Holocene-Pleistocene unconformity. The absence of Pleistocene reefal deposits, at 15 m depth in the cores from MacGillivray Reef, raises the possibility that the shelf in this region has subsided relative to modern day sea level by at least 15 m since the last interglacial [125,000 years ago (ka)].     

Microbiological assessment of a disease outbreak on corals from Magnetic Island (Great Barrier Reef, Australia)

Unusual disease lesions were observed in Montipora corals on the fringing reef of Magnetic Island (Great Barrier Reef, Australia) following a period of high water temperature in early January 2002. Tissue death in Montipora spp. appeared as a black layer that spread rapidly across the colony surface, though this appeared as the final phase of disease progression (with three previous disease phases now identified, S. Anthony, unpublished). Culture and molecular-based microbial analysis of this layer did not identify a likely microbial pathogen. Despite this, DNA sequencing of microbial 16S rDNA indicated a shift in the bacterial population associated with affected coral tissue. A clone library of the healthy coral sample predominantly contained sequences within the -Proteobacteria. A disease coral sample representing the margin of the black lesion and healthy coral tissue was dominated by sequences, which demonstrated low sequence identity to a range of -Proteobacteria, -Proteobacteria and cyanobacteria. The microbes identified in the diseased Montipora spp. samples are likely to be opportunistic rather than the causative agent of the observed lesion. Studies are in progress to further characterise the ecology of this disease and describe the potential microbial pathogen(s).     

Copepoda associated with the coral Gardineroseris planulata (Dana) on the Great Barrier Reef,northeastern Australia

Three new lichomolgid copepods associated with the scleractinian Gardineroseris planulata (Dana) are described: Sociellus torus, n. gen., n. sp., characterized by a 2-segmented endopod in leg 3 and the lack of an inner seta on the first segment of the endopod in legs 1–3; Odontomolgus pumilus, n. sp., of very small size and having a much elongated free segment in leg 5 of the female; and Paramolgus ampullaceus, n. sp., distinguished by the bottle-shaped genital segment of the female. In addition, the harpacticoid Alteuthellopsis corallina Humes, 1981, is reported from this coral. With the inclusion of 3 species of the poecilostomatoid genus Xarifia already described (Humes, 1985) there are now 7 species of copepods known to be associated with Gardineroseris planulata on the Great Barrier Reef.     

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     

Sand and nest temperatures and an estimate of hatchling sex ratio from the Heron Island green turtle (Chelonia mydas) rookery, Southern Great Barrier Reef

Sand and nest temperatures were monitored during the 2002–2003 nesting season of the green turtle, Chelonia mydas, at Heron Island, Great Barrier Reef, Australia. Sand temperatures increased from ∼ 24°C early in the season to 27–29°C in the middle, before decreasing again. Beach orientation affected sand temperature at nest depth throughout the season; the north facing beach remained 0.7°C warmer than the east, which was 0.9°C warmer than the south, but monitored nest temperatures were similar across all beaches. Sand temperature at 100 cm depth was cooler than at 40 cm early in the season, but this reversed at the end. Nest temperatures increased 2–4°C above sand temperatures during the later half of incubation due to metabolic heating. Hatchling sex ratio inferred from nest temperature profiles indicated a strong female bias.     

Elemental signatures of Acanthochromis polyacanthus otoliths from the Great Barrier Reef have significant temporal, spatial, and between-brood variation

We evaluated the spatial and temporal scales over which otolith signatures varied in a reef fish on the Great Barrier Reef (GBR) using the non-dispersing damselfish Acanthochromis polyacanthus. We found a robust multi-element separation in otolith signatures from reef clusters in the northern and southern GBR. Variance components indicated that this spatial scale accounted for the majority of the variation in two elemental ratios (Ba/Ca and Sr/Ca) over the 2 years of the study. There was also significant variation in elemental signatures between otoliths collected over two consecutive years, as well as within a season. Individual reefs within clusters were less distinguishable based on otolith chemistry and were probably observed by differences within reefs (among sites and broods within sites). These results indicate that it may be difficult to determine the reef of origin for individual fish using otolith chemistry, while determining natal region seems a realistic goal.     

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.     

Ontogenetic habitat shifts in fusiliers (Lutjanidae): evidence from Caesio cuning at Lizard Island,Great Barrier Reef

Planktivorous reef-associated fishes provide a significant nutrient input to the reef, linking pelagic and reef environments. Highly mobile and relatively large body-sized fusiliers (Lutjanidae) often dominate reef fish biomass, but their role in ecosystem processes is poorly understood. We therefore combined fish counts and behavioural observations at Lizard Island, Great Barrier Reef, to investigate: (1) the spatial distribution and biology of fusiliers on a lagoonal coral reef system, and (2) how does fusilier behaviour and size distribution change from exposed to sheltered locations. We found higher abundances of large-sized fusiliers (≥ 20 cm total length) on exposed reef sites. Sheltered sites had almost exclusively small individuals (< 20 cm total length). We interpret this pattern as indicative of an ontogenetic habitat shift. This shift was estimated to occur at about 11.15 cm total length; the size at which the likelihood of an individual being in exposed or sheltered locations was equal. The age corresponding to this length was 1.01 years, based on a von Bertalanffy growth model using size-at-age data from otolith rings of Caesio cuning, the most abundant fusilier species in this location. This suggested that the shift in distribution occurred prior to the onset of sexual maturity. This apparent ontogenetic shift to more exposed habitats with increasing size, especially in C. cuning, was also associated with a distinct behavioural profile: larger fish at the exposed sites travelled further off reef, occupied deeper habitats, and formed larger schools compared to smaller individuals. This study provides the first evidence of seascape-scale ontogenetic habitat shifts in a planktivorous reef fish, providing a foundation for future detailed analyses of the ecological roles of fusiliers.

     

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.     

Methods for sampling free-living Symbiodinium (zooxanthellae) and their distribution and abundance at Lizard Island (Great Barrier Reef)

The abundance and distribution of free-living dinoflagellates in the genus Symbiodinium have important implications for the ecology of coral reefs, determining both the symbionts available to newly recruited corals and symbiont types available for uptake by adult corals during environmental stress. However, little is known about where symbiotic dinoflagellates reside outside the host, due to the difficulty of capturing and detecting unicellular organisms in the marine environment. This study presents a successful protocol for sampling Symbiodinium from both the benthos and the water column. Comparisons of two detection methods for enumerating Symbiodinium indicated that conventional microscope analysis is accurate and more efficient when estimating Symbiodinium densities in sediment samples, while an automated particle counter (FlowCAM) was more efficient in detecting cells in the water column where densities are low. Symbiodinium densities were found to be relatively high (1000–4000 cells/mL) in sediment samples and much lower (up to 80 cells/mL) in the water column, indicating that the free-living form resides mainly in the benthos. Symbiodinium densities were found to be highly variable spatially, differing significantly between two reef locations. Within sites, elevated densities of Symbiodinium along reef margins combined with significant decreases in densities one meter away from the reef, suggest that cells aggregate within the reef habitat.     

Taxonomy, host specificity and dietary implications of Hurleytrematoides (Digenea: Monorchiidae) from chaetodontid fishes on the Great Barrier Reef

Five new and five previously described species of Hurleytrematoides are reported from 19 of 34 chaetodontid species examined from the Great Barrier Reef; new species are H. faliexae n. sp., H. galzini n. sp., H. loi n. sp., H. morandi n. sp., and H. sasali n. sp. Previously described species are H. coronatum, H. fijiensis, H. prevoti, H. bartolii, and H. zebrasomae. The genus is rediagnosed in the light of morphological variation of the new species; the degree of spination and shape of the terminal genitalia distinguish individual species. Species of Hurleytrematoides infect almost every clade of the family Chaetodontidae found on the Great Barrier Reef, but obligate corallivores are not infected. All ten species were found at Heron Island on the southern Great Barrier Reef, but only six at Lizard Island on the northern Great Barrier Reef. For three of the four species not present at Lizard Island, the absence appears to be statistically significant. Although all species are apparently restricted to chaetodontids on the GBR, specificity within the family varies from oioxenous to euryxenous; a core/satellite host paradigm explains the distribution of several species.     

Low genetic structuring among <Emphasis Type="Italic">Pericharax heteroraphis</Emphasis> (Porifera: Calcarea) populations from the Great Barrier Reef (Australia), revealed by analysis of nrDNA and nuclear intron sequences

A new nuclear marker system for sponges, the second intron of the nuclear ATP synthetase beta subunit gene (ATPSbeta-iII), was analysed together with nuclear ribosomal DNA (nrDNA) internal transcribed spacer (ITS) sequences aiming to uncover phylogeographic patterns of the coral reef sponge Pericharax heteroraphis in the south-west Pacific, focussing on the Great Barrier Reef (GBR). Variation among ITS sequences was low (<1.1% p-distance), in contrast to ATPSbeta-iII (<8.3% p-distance). Single-Stranded Conformation Polymorphism (SSCP) analysis proved to be an effective tool for phasing ATPSbeta-iII alleles of 292 bp length. Although sample sizes were limited for most populations and these results await corroboration by an extended sampling regime, a past population subdivision with subsequent range expansion was indicated by a ‘dumb-bell’ shaped statistical parsimony network of GBR ATPSbeta-iII alleles. Although no clear phylogeographic break was discovered on the GBR, the northern GBR was genetically differentiated from the central/southern GBR and Queensland Plateau, based on significant pairwise F _st values (0.137–0.275 and p ≤ 0.05) of pooled regional populations. The ATPSbeta-iII used in this study outperformed the frequently employed nrDNA ITS and might also turn out to be useful for phylogeographic studies of other coral reef taxa. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Genetic diversity of isolated populations of Nautilus pompilius (Mollusca, Cephalopoda) in the Great Barrier Reef and Coral Sea

Nautilus species are the only remaining cephalopods with an external shell. Targeted heavily by the shell trade across their distribution area, these species have a poorly known population structure and genetics. Molecular techniques have been used to assess levels of inter- and intra-population genetic diversity in isolated populations of Nautilus in the northern sections of the Great Barrier Reef (GBR), Australia and in the Coral Sea. Distinct populations, physically separated by depths in excess of 1,000 m were examined. RAPD analysis of genetic differences showed limited differentiation of the “Northern GBR” populations and the “Coral Sea” populations. Discrimination between the two geographic groups was observed from these data. In addition, partial sequencing of the CoxI gene region, yielded 575 bp of sequence, which was aligned for 43 samples and phylogenetic trees constructed to examine genetic relationships. Two distinct clades were resolved in the resulting trees, representing the “Northern GBR” and “Coral Sea” population groups. Inter- and intra-population relationships are presented and discussed. The differentiation of the Nautilus populations from the Northern section of the Great Barrier Reef and those from the Coral Sea were supported by two distinctly different methodologies and the significance of this separation and the potential evolutionary divergence of these two population groups is discussed.     

Spatial and temporal patterns of non-colonial boring organisms (polychaetes,sipunculans and bivalve molluscs) in Porites at Lizard Island,Great Barrier Reef

A study of the spatial and temporal patterns of colonisation by non-colonial boring organisms to dead Porites coral substrate was conducted at Lizard Island, Great Barrier Reef over a 4 year period. These fluctuations were analysed for each group of borers, and most exhibited strong site preferences, with preferred sites being on the windward slope in 10 m and on the reef flat in 1 m. A lagoonal patch reef site exhibited consistently low colonisation. Most groups showed inter-year variations in colonisation with spring/early summer dominating. These variations are discussed in terms of what is known about their life histories. These results together with those of Kiene (in preparation) which document varying rates of bioerosion, at these sites over the same time period, demonstrate that variations in borer colonisation are responsible for the variations in rates of bioerosion calculated. Thus rates of bioerosion by borers will vary significantly between different reef environments.     

Stock Structure, Mortality and Growth of The Decorated Goby, Istigobius decoratus (Gobiidae), at Lizard Island, Great Barrier Reef

Gobiids are an abundant component of coral reef ichthyofauna, yet little is known of their life histories. I examined population structure, mortality and growth of the decorated goby, Istigobius decoratus, a common gobiid of shallow patch reefs on the Great Barrier Reef. Presumed daily increments in sagittal otoliths were used as a proxy for age. The upper age estimate was 266 days suggesting at most an annual life cycle. Instantaneous natural mortality rate estimates were 5.92 year^–1 and 7.92 year^–1 using two estimators, both corresponding to less than 1% annual survivorship. Specimens ranged from 12 to 84 mm total length. Analysis of size-at-age data indicated linear growth at a rate of 0.33 mm day^–1. The linear relationship between size and age meant the population size structure mirrored the age structure with both skewed toward the smallest and youngest classes. High mortality over a 1-year longevity and linear growth suggest high population turnover and, therefore, that I. decoratus and ecologically similar species serve a potentially important role as prey species. This suite of traits is rarely reported for coral reef fishes, which is probably due to the limited attention paid to small-bodied species rather than the rarity of such a life history in these communities.     

Reproductive development and timing of tropical sponges (Order Haplosclerida) from the Great Barrier Reef,Australia

Reproductive development of three species of the Haplosclerida, Haliclona amboinensis (Lévi 1961), Haliclona cymiformis (Esper 1794) and Niphates nitida Fromont (1993), was monitored for three years on a fringing reef in the central section of the Great Barrier Reef, Australia. All species are viviparous, and gonochoric. Haliclona amboinensis and N. nitida incubated eggs, embryos and larvae in brood chambers. The branching sponge. H. cymiformis, incubated eggs, embryos, and larvae along the central axis of branches. In all species, sperm cysts in high densities are evenly distributed throughout the mesohyl. Mature larvae of all species are creamy white, oval, parenchymella, with a dark coloured ring at the posterior pole. Eggs, embryos and larvae are present contemporaneously for periods of two consecutive months in individuals of H. cymiformis and seven months in H. amboinensis and N. nitida. The first observation of female reproductive products in H. amboinensis and N. nitida coincided with an increase in water temperature, while cessation of reproductive activity was associated with decreasing water temperature. Onset of reproduction in H. cymiformis coincided with peak sexual and vegetative reproductive activity of its algal symbiont, Ceratodictyon spongiosum.     

Ostracoda (Crustacea) from Lizard Island,northern Great Barrier Reef,Australia. I. Families: Cytherellidae,Loxoconchidae, Cytherideidae,Cytheruridae, Paracytherideidae,Pectocytheridae, Krithidae,Cytheromatiidae, Bythocytheridae,Cytheridae

This paper deals with the taxonomy of the ostracod families Cytherellidae, Cytheridae, Cytheromatidae, Cytherideidae, Krithidae, Loxoconchidae, Paracytherideidae, Cytheruridae, Pectocytheridae and Bythocytheridae from the coral reefs around Lizard Island, northern Great Barrier Reef, Australia. 22 species belonging to these families were found. 7 species had been described from Australian coasts, 1 from the Red Sea and 1 with Indopacific-Westatlantic distribution. 9 species are newly described and 4 species remain in open nomenclature.