Effects of temperature on the respiration of brooded larvae from tropical reef corals

This study describes the effects of temperature on the respiration of brooded larvae of scleractinian corals, and evaluates the implications of these effects relative to seawater temperature when peak larval release occurs. Respiration rates of larvae from Pocillopora damicornis, Seriatopora hystrix and Stylophora pistillata were quantified in darkness as oxygen uptake during 1-3. h exposures to five temperatures between 26.4 and 29.6 degrees C. To assess the biological significance of these experiments, the temperature of the seawater into which larvae of P. damicornis and S. hystrix were released was measured for 32-34. months over 5 years between 2003 and 2008. Mean respiration varied from 0.029 to 0.116 nmol O-2 larva(-1) min(-1), and was related parabolically to temperature with a positive threshold at 28.0 degrees C. The temperature coefficients (Q(10)) for the ascending portion of these relationships (Q(10)=15-76) indicate that the temperature dependency is stronger than can be explained by kinetics alone, and probably reflects behavioral and developmental effects. Larval release occurred year-round in synchrony with the lunar periodicity when seawater temperature ranged from 21.8 to 30.7 degrees C, and more than half of the sampled larvae were released at 27.5-28.9 degrees C. The coincidence on the temperature scale of peak larval release with the thermal threshold for respiration suggests that high metabolic rates have selective value for pelagic coral larvae. The large and rapid effects of temperature on larval respiration have implications for studies of the effects of climate change on coral reproduction, particularly when seawater temperature exceeds similar to 28 degrees C, when our results predict that larval respiration will be greatly reduced.