Documenting successional dynamics of coral communities following large-scale bleaching events is necessary to predict coral population responses to global climate change. In 1998, high sea surface temperatures and low cloud cover in the western Pacific Ocean caused high coral mortality on the outer exposed reefs of Palau (Micronesia), while coral mortality in sheltered bays was low. Recovery was examined from 2001 to 2005 at 13 sites stratified by habitat (outer reefs, patch reefs and bays) and depth (3 and 10 m). Two hypotheses were tested: (1) rates of change of coral cover vary in accordance with habitat, and (2) recovery rates depend on recruitment. Coral cover increased most in the sheltered bays, despite a low recruitment rate, suggesting that recovery in bays was primarily a consequence of remnant regrowth. Recruitment densities were consistently high on the wave-exposed reefs, particularly the western slopes, where recovery was attributed to both recruitment and regrowth of remnants. Recovery was initially more rapid at 10 m than 3 m on outer reefs, but in 2004, recovery rates were similar at both depths. Rapid recovery was possible because Palau's coral reefs were buffered by remnant survival and recruitment from the less impacted habitats.

This study assessed the effects of seasonal temperatures on suspension feeding, related physiological parameters and energy budgets in 2 pearl oysters, Pinctada margantifera and P. maxima. Pearl oysters that were acclimatised at approximately 19, 23, 28 and 32°C in the field were tested in the laboratory at these temperatures Clearance rate (CR), absorption efficiency (ae), absorbed energy (AE), respired energy (RE), excreted energy (EE) and the value of (AE -RE) were significantly affected by temperature. They usually Increased with increasing temperature. ae, RE, EE and the value of (AE -RE) differed significantly between the pearl oyster species. P. margaritifera had a significantly higher CR than P. maxima at 19°C. P maxima had higher a e than P. margaritifera at 28 and 32°C. As a result, P. margantifera had greater AE than P. maxima at lg°C, but the latter species had greater AE at 32°C. Temperature significantly affected the RE of P. margaritifera over a wider temperature range (19 to 32°C) than P, maxima (19 to 23°C). However, interspecific Mferences in RE were only significant at 32°C. P maxima had significantly higher EE at 32'C than P. margaritifera, although this energy accounted for a very small portion of AE (<5 %). P. maxima exceeded P. margaritifera in Scope for Growth [SFG = (AE -RE) -EE] at 32"C, but the latter species had greater SFG at 19OC. These results agree with observations of the occurrence of P. margaritifera at higher latitudes and lower temperature habitats. The temperature effects on suspension feeding, related physiological parameters and SFG indicate that there will be marked seasonal variations in growth in both species in environments where water temperatures vary seasonally. In bioenergetic terms, the optimum temperature ranges for these pearl oysters are approximately 23 to 28 and 23 to 32°C for P. margaritifera and P. maxima, respectively.

This study compared suspension f e e d n g , assimdation efficiency, respiration and excretion, and energy budgets (= scope for growth, SFG) in relation to body size in 2 pearl oysters, Pinctada maryaritifera and P. maxima, at a low food concentration (ca 5000 cells ml-l Tahitian Isochrysis galbana). Clearance rate (CR), respiration rate (K) and ammonia excretion rate (E) were strongly correlated with body size ( p < 0 001) in both species, wlth exponents of 0.60 and 0.61 (CR), 0.44 and 0.56 (R), and 0.64 and 0.78 (E), respectively, for P margaritdera and P maxima. CR did not differ significantly between the species, but absorption efficiency, which was unrelated to size, was significantly greater in P maxima (57 5 vs 51 %, p < 0.05). There was, however, no significant difference in absorbed energy (AE) between the species. Respired energy (RE) and excreted energy (EE) as proportions of AE were slgniflcantly lower ( p < 0.01) in P. maxima of 0.1 g dry soft tissue wt (ca 36 mm shell height, SH). The former was 0.36 compared to 0.58 in P. margaritifera of the same size. Thus, P. m a x m a of 0.1 g dry soft tissue wt exceeded P. margaritlfera of the same size in SFG, which accords with the former species' more rapid early growth. Both species of pearl oysters have a high abihty to acquire energy under low phytoplankton conditions. Both species are exceptional bivalves in terms of energy fluxes, with clearance rates of 50 to 100 1 h-' in large oysters of 150+ mm SH. They show among the highest CR, R, E and SFG values recorded for blvalves (using 1 g dry soft tissue wt as a standard size). The largest g a n t clam, Tridacna gigas, is one tropical bivalve with comparable SFG. It, however, 1s dependent on energy from autotrophy as well as heterotrophy to achieve its high SFG.

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ABSTRACT-This study aimed to determine the influence of microalgal species and food concentration on various physiological parameters and Scope for Growth (SFG) in adults of 2 pearl oysters, Pinctada margantifera and P maxima. Clearance rate, pseudofaecal production rate, absorption efficiency, respiration rate and excretion rate were determined over a range of food concentrations using 2 microalgal diets, Tah~tian Isochrysis sp. (T-Iso) and Dunaliella primolecta at 28'C. Clearance, pseudofaecal production and respiration rates were significantly affected by microalgal diet. From these results, and because of the higher energy content of T-Iso, pearl oysters feeding on T-lso had maximum values of SFG that were 1.5 to 2 1 times higher than when feeding on D. pnmolecta. Clearance rate and absorption efficiency were significantly related to food concentration as negative exponential relationships (p c 0 001). Generally, pseudofaecal production, respiration and excretion rates were significantly related to food concentration as positive linear relationships (p < 0.005) Optimal food concentrations for max~mum SFG for P margarjtifera and P maxima were 1 to 2 mg I-' and 2 to 3 mg I-', respectively. P. maxima was better adapted to a wider range of food concentrations. P. maxima maintained positive SFG up to 9 mg I-' food concentration when feeding on T-lso and up to 7 mg I-' when feeding on D. primolecta, while equivalent values for P. margaritifera were 7 mg 1-' and 5 mg I-', respectively. Thesc results are in accordance with P. maxin~a occurring in a wider range of habitats than P margaritiferd, and experiencing greater concentration ranges of suspended particulate matter