Effects of temperature and pCO2 on lipid use and biological parameters of planulae of Pocillopora damicornis

The successful dispersal and recruitment of coral larvae depend on endogenous energy stores that fuel swimming, the search for optimal habitat, and metamorphosis. Ocean acidification and warming threaten to disrupt this critical process within the life cycle of reef-building corals by increasing maintenance costs in the energy budgets of larvae. In this study, lipid utilization and biological parameters of planula larvae of the cauliflower coral Pocillopora damicornis under future ocean conditions were examined using manipulative CO2 experiments. For the first 24 h following their release, planulae were cultured in seawater controlled to mimic a future ocean scenario (1030 µatm pCO2, 30.7 °C) as well as present-day, ambient ocean conditions (475 µatm pCO2, 28.1 °C; confirmed by autonomous sensors deployed at our study site). Abundance of wax ester, triacylglycerol, and phospholipids as well as traits of physiological status were measured before and after incubations. High temperature and pCO2 conditions did not elicit changes in wax ester composition of larvae. Triacylglycerol content increased with temperature but was not sensitive to pCO2. In general, larvae consumed more total lipid and protein in response to conditions of warming but not high pCO2, and the day the larvae were released often played a large role in the biological patterns observed. Our results suggest that future ocean warming may influence some organismal properties of coral larvae. High pCO2 may not have a strong effect on the physiology of this early life history stage.