On coral reefs, sites that receive consistently high levels of recruitment relevant to other sites (“recruitment hotspots”) may be crucial to the persistence of populations. However, few studies of coral recruitment have the necessary replication in space and time required to detect recruitment hotspots. The aim of this study was to detect recruitment hotspots at One Tree Reef (southern Great Barrier Reef) and to explore associations between hotspots, hydrodynamics, adult abundance and reef benthos. Recruitment hotspots were detected on the reef slope and in the lagoon. Almost all hotspots were located on the leeward side of the reef, however, there was little congruence among hotspots for different families of coral recruits. Recruitment hotspots in some taxa in some habitats were correlated with water flow or adult abun-dance. A clear recruitment hotspot for two families (Pocilloporidae and Poritidae) in the lagoon had medium levels of water flow (∼4 cm s^-1), but there was no re-lationship with water flow on the slope. In experimental aquaria, Acropora nasuta settlement was six to 10 times greater under low (2.1 cm s^-1) compared to medium water flow (4.6 cm s^-1). Abundance of pocilloporid and poritid, but not acroporid, recruits at each site was often correlated with adult cover indicating either aggregative settlement or limited dispersal. Recruitment hotspots are likely to be both sources and sinks for some taxa, and therefore identifying and protecting hotspots should be a high priority in marine reserve design.

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Coral communities at nine sites off the coast of Motobu, Okinawa, were examined 6 and 12 years after a 1998 mass coral bleaching event caused by anomalous seawater temperatures. Overall, mean coral coverage increased from 17% in 2006 to 28% in 2010 at these sites, although these percentages were lower than the coral coverage at a nearby reef at Sesoko Island. Some of the corals that had not recovered (the “losers”) at the Sesoko reef were found at some sites in the present study. Dominant coral taxa differed among sites, probably because of differences in the environmental conditions at the sites, e.g., the so-called massive-type coral Porites dominated at a protected site near a river, while branching-type Acropora was dominant at exposed sites. Acropora was one of the prominent short-term losers, but contributed significantly to coral coverage increases due to its fast growth at some exposed sites. Adjacent reefs, which may share similar environmental conditions, also showed some variability, possibly due to processes such as coral recruitment and post settlement survival, which acted on a smaller spatial scale. Multivariate analyses such as multidimensional scaling were more sensitive than univariate analyses. Overall, recruitment was low, especially at sites with high coral coverage, which implies that remnant corals may have contributed to the recovery of these reefs. Coral communities in this area are recovering and there has been no apparent shift to algae-dominated communities. The recovery of coral communities appears to be related to the life history traits of corals and environmental conditions.

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Coral reefs in many regions are under threat because of global warming, and local anthropogenic environmental changes and monitoring of the dynamics of coral communities is indispensable for understanding their response to these stresses. Different taxonomic resolutions have been used in the monitoring of coral communities depending on the research objective and the availability of resources. In this study, we examined the variation in the patterns of coral communities with the use of different taxonomic resolutions and assessed which of these were most sensitive to changes. Richness and composition measures of coral communities at 9 sites in Motobu, Okinawa, southwestern Japan, were monitored in 2006 and 2010. We compared taxonomic richness of corals among sites using univariate analysis, and taxonomic composition based from percent cover of each taxonomic group at different taxonomic resolutions using multivariate analysis. The pattern in terms of taxonomic composition employing life-form (taxonomic resolution based on colony morphology) were similar with the finer taxonomic resolution (family, genus, and “genus×life-form”) in 64% of all the possible site pair-wise comparisons in 2006, and 75% in 2010. Thus monitoring using life-form taxonomic resolution may be sufficient, particularly in the analyses of composition measures when resources are limited. However for the analyses of richness measurements, use of at least family level of taxonomic resolution may be recommended because the pattern of the richness difference among the sites at the life-form level were different from those at the finer levels of taxonomic resolution in 39% of the comparisons, especially in 2010. The adequacy of the use of coarser taxonomic resolution has some important implications for coral reef management because most monitoring is conducted by non experts in coral taxonomic identification.

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Some coral species have extremely long life spans. Many corals have the capacity to regenerate from fragments or pieces of tissue; thus, they rely, at least in part, on asexual reproduction for the maintenance of their populations. As a first step in understanding the mechanism underlying the long life span of corals and their possible rejuvenation during asexual reproduction, we studied whether the somatic tissues of the coral Galaxea fascicularis had telomerase activity. We quantified the level of telomerase activity in various parts of polyps using stretch PCR. The outer and inner wall tissues of the polyps showed similar levels of telomerase activity, which were comparable with that of HeLa cells, on a unit protein basis. Because the outer wall tissue does not contain gonads, it is suggested that somatic tissues of the coral possesses telomerase activity. Telomerase activity was detected throughout the year in the polyps, regardless of the gonad maturation stage. This study reports that the somatic tissue of the coral has telomerase activity.

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The Mg/Ca and Sr/Ca ratios were determined for Porites lutea specimens that were collected from Koh Chueak, Surat Thani Province, Thailand, using inductively coupled plasma optical emission spectrometry. The elemental analyses were performed from the surface to the interior of the coral specimen along its growth axis at 1-mm intervals, generating the near-monthly resolved time series for the Mg/Ca and Sr/Ca ratios. The ratios demonstrate clear annual cycles, which are assumed to reflect variations in the sea surface temperature (SST). Comparing with the annual maximum and minimum values of SST, the following Mg/Ca-SST and Sr/Ca-SST relations were determined: Mg/Ca (mmol/mol)=-1.72+0.193×SST and Sr/Ca (mmol/mol)=11.83-0.098×SST. These relations are different than those of previously published studies. The reason for this difference is unclear; however, it may be related to vital effects that have been observed for geochemical proxies in coral skeletons and to differences in chemical composition of seawater and in sampling procedure.

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Ninety-three coral species have been identified at Okinotorishima (Okinotori Island), an isolated table reef located in the center of the Philippine Sea. The species composition of the island is similar to that of other islands in the northwestern Pacific, but the number of species is small in comparison with surrounding islands. The coral fauna at the island is characterized by a unique species composition that is independent of the Ryukyu Islands, mainland Japan, Palau, and the Mariana Islands. No endemic species were found, but the dominant Acropora species (A. aculeus, A. sp. aff. divaricata, and A. globiceps) were morphologically different from corresponding species at the Ryukyu Islands. The relatively low species diversity at the island despite the close proximity to an area of high diversity is explained by its small habitat diversity and isolation from other islands. The island is located in a subtropical gyre and is isolated from major currents. Thus, only coral larvae with a long competency period (as long as 70 days) can settle at the island from surrounding islands. This unique species composition seems to have been maintained for at least the last 7600 years, since the last stage of sea level rise in the post-glacial period (Holocene).

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This paper presents the first temperature-growth performance curves for a coral reef fish. Thermal tolerance and growth for the juvenile spiny damselfish Acanthochromis polyacanthus were measured at a range of temperatures from 15°C to 38°C. A. polyacanthus juveniles showed a critical thermal minimum at 15.5°C±0.1 and a critical thermal maximum at 38°C±0.12. Maximal growth (based on changes in length) occurred at 28-31°C, whereas weight gain was maximised at 28°C, which corresponds closely with the annual mean temperature currently experienced by these fishes in their natural environment. At temperatures >31°C the growth rate decreased markedly in length and weight up to 34°C, where fishes had negligible growth and died within 8-15 days. Sustained increases in ambient temperature (due to climate change) are expected to have significant adverse effects on these fishes. However, any effects of increasing temperature may also be offset by changing the timing of reproduction; by breeding in early spring or late summer, these fishes may still be able to exploit narrow windows of thermal optima, whereas fishes breeding in the height of summer will expose offspring to potentially lethal temperatures at critical stages during their development.

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Opisthobranchs are marine gastropod mollusks, which are noted for their often extraordinary colors and striking forms. Opisthobranchs falls under the least studied category of mollusks not only from Andaman and Nicobar Islands but also in entire Indian waters. The taxonomy and ecology of these animals of these Islands recently gained an attention after about a century of the publication by Eliot, 1910. The present work deals with 20 species of opisthobranchs, belonging to 11 families of these 17 species are new to the Indian waters.

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The contribution of coral rubble associated microbial community to the dissolution of calcium carbonate at different pCO₂ levels were investigated using incubation experiments at Sesoko Island, Okinawa, Japan. Short incubation (24h under natural illumination) and long incubations (4 days under natural illumination and dark condition) were carried out using white coral skeleton (control), natural rubble, treated rubble (removed epilithic community) and natural rubble with added organic matter (glucose) under different levels of pCO₂ (ambient, 520, 720 and 1120ppm). Net primary production, respiration and dissolution rates of the endolithic communities were much higher than the epilithic communities at all pCO₂ levels. During the long experiment under natural illumination, carbonate dissolution rates varied from 23.7±0.1 (ambient) to 50.5±1.5 (1120ppm)μmol m^-2d^-1 at night time and 3.2±1.1 (ambient) to 5.8±1.2 (1120ppm) μmol m^-2d^-1 at day time. However, in long experiment under complete dark condition dissolution increased to 81.6 ±0.2μmol m^-2d^-1 at high pCO₂. With addition of glucose as source of organic matter, growth of bacteria was enhanced and therefore respiration rate increased. Heterotrophic microbial communities produced more CO₂ and promoted carbonate dissolution. This was reflected by further decrease in aragonite saturation state (Ωa) and increase in pCO₂ levels. The results show that inputs of organic matter in the reefs enhance metabolic activities of microbial communities associated with coral rubble which ultimately increase dissolution of calcium carbonate. These suggest the importance of biological processes (photosynthesis vs. respiration) in determining calcification and dissolution.

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