Temporal settlement patterns of larvae of the broadcast spawning reef coral Favites chinensis and the broadcast spawning and brooding reef coral Goniastrea aspera from Okinawa, Japan

The faviid corals, Favites chinensis and Goniastrea aspera are widely distributed in the Indo-Pacific region. Both corals are hermaphroditic broadcast spawners, but G. aspera is also known to brood planula larvae in Okinawa. This study investigated the temporal settlement patterns of planula larvae of the scleractinian corals F. chinensis and G. aspera that developed from spawned gametes, and planula release and settlement of brooded larvae of G. aspera from Okinawa, Japan. Some of the broadcast-spawned larvae of F. chinensis and G. aspera had very short pre-competency periods of 1–2 and 2–3 days after spawning, and relatively long maximum settlement-competency periods of 56–63 and 63–70 days after spawning, respectively. These pre-competency periods are among the shortest reported for larvae of broadcast spawning coral species, and appear to be negatively correlated with seawater temperature. F. chinensis larvae tended to settle rapidly with 34–39% of larvae settling in the first week after spawning, while broadcast-spawned G. aspera larvae had a slower settlement pattern with 11–15% of larvae settling in the first week after spawning. Brooded larvae of G. aspera settled more rapidly, with settlement rates of 27–31% within the first 24 h and 45–65% within the first week after the start of the experiment. The production of planula larvae with rapid settlement capabilities may enable F. chinensis and G. aspera to establish and maintain populations in shallow reef sites at Okinawa. The release of the brooded planulae for up to 2 months may explain why G. aspera is locally more dominant on shallow reefs in Okinawa than F. chinensis. On a broader scale, the longer settlement competency periods of some of the broadcast-spawned larvae of these species increase their potential for longer-distance dispersal and may partly explain the wide biogeographic distribution of these species in the Indo-Pacific region.     

The effects of hydrogen peroxide on metabolism in the coral Goniastrea aspera

Coral metabolism reflects the physiological condition of a coral colony. We studied coral metabolism using a continuous-flow, complete mixing (CFCM) experimental system. Small-size Goniastrea aspera coral colonies were incubated in the CFCM system with and without hydrogen peroxide (H₂O₂) added to the supplied seawater (0 µM H₂O₂ for 12 days; 0, 0.3, 3.0, and 30 µM H₂O₂ for 3 days, for each treatment) Without addition of H₂O₂, coral metabolism, including photosynthesis (gross primary productivity) and calcification, was relatively stable and there were no significant metabolic changes, suggesting that, without H₂O₂ added to the CFCM system, the corals did not suffer significant stress from the experimental system over a 12-day incubation period. When H₂O₂ was added, large decreases in photosynthesis and calcification were observed. The non-parametric Mann–Whitney U-test showed that there were statistically significant differences in photosynthesis after addition of 3.0 µM and 30 µM H₂O₂, compared with the control. We also found statistically significant differences in net calcification after addition of 30 µM H₂O₂. Thus, the incubation experiments suggest that higher H₂O₂ concentrations in seawater clearly influence coral metabolism. However, the results also suggest that the current seawater H₂O₂ level in Okinawa is not likely to pose significant acute effects on the metabolic activities of corals.     

Characterization of fatty acid composition in healthy and bleached corals from Okinawa, Japan

Under bleaching conditions, corals lose their symbiotic zooxanthellae, and thus, the ability to synthesize fatty acids (FAs) from photosynthetically derived carbon. This study investigated the lipid content and FA composition in healthy and bleached corals from the Odo reef flat in Okinawa, southern Japan, following a bleaching event. It was hypothesized that the FA composition and abundance would change as algae are lost or die, and possibly microbial abundance would increase in corals as a consequence of bleaching. The lipid content and FA composition of three healthy coral species (Pavona frondifera, Acropora pulchra, and Goniastrea aspera) and of partially bleached and completely bleached colonies of P. frondifera were examined. The FA composition did not differ among healthy corals, but differed significantly among healthy, partially bleached, and completely bleached specimens of P. frondifera. Completely bleached corals contained significantly lower lipid and total FA content, as well as lower relative amounts of polyunsaturated FAs and higher relative amounts of saturated FAs, than healthy and partially bleached corals. Furthermore, there was a significantly higher relative concentration of monounsaturated FAs and odd-numbered branched FAs in completely bleached corals, indicating an increase in bacterial colonization in the bleached corals.     

Isolation of microsatellites from two species of scleractinian coral

Microsatellites were isolated from two broadcast‐spawning species of scleractinian coral (Platygyra daedalea and Goniastrea favulus) from Australia's Great Barrier Reef. We found 27 microsatellites across both species, although only five loci were polymorphic in each species. Microsatellite loci displayed a wide range of diversity levels with four to 11 alleles per locus (H_O = 0.26–0.91) in P. daedalea and two to seven alleles per locus (H_O = 0.16–0.96) in G. favulus. Most loci showed departures from Hardy–Weinberg equilibrium which may reflect nonrandom mating but may also be related to difficulties associated with coral DNA.