ASSESSING THE EFFECT OF THERMAL STRESS ON LARVAL LIPID RESERVES OF THE THREATENED ELKHORN CORAL, ACROPORA PALMATA

Reef-building corals have a biphasic life cycle with a sessile adult and a dispersive larval stage. The dispersive stage is important because it connects populations and maintains genetic diversity. Global warming has increased sea surface temperatures, which has resulted in faster development rates of some marine invertebrate larvae. Here we explore if temperature stress affects larval energy reserves in corals. Because these lecithotrophic larvae rely on their lipid-rich energy reserves, lipids are a good proxy to quantify energy reserves. Larvae of the threatened coral Acropora palmata were exposed to 27 and 30°C temperatures and sampled 48 hours post-fertilization. To test the hypothesis that higher temperatures deplete energy reserves faster, lipids were extracted, quantified and analyzed. A base hydrolysis on the total lipid fractions was performed on a subset of the samples, which were then further analyzed using gas chromatography-mass spectrometry to separate and quantify different lipid classes. Total lipid reserves were more depleted at 30°C (23.28µg/larva) than at 27°C (28.74µg/larva); these results are not statistically significant. In the subset of samples which were base hydrolyzed, 16 and 18 carbon chains were most abundant consistent with previous findings. Only one of four larval cultures differed significantly in the abundance of 16 and 18 carbon lipid derivatives at 30°C in pair-wise comparisons. The observed trends may be biased by small sample sizes (n=3), however, these results suggest that at higher temperatures larvae may run out of energy faster, which may have implications for larval dispersal and settlement.