MCR LTER: Coral Reef: Coral Larval Metabolism in pH and Temperature Treatments

In this study, we explored plasticity of physiological responses of coral larvae from a
reef in French Polynesia. The study was motivated by these questions: (1) what is the
present-day exposure of Pocillopora damicornis to natural variability of pH and temperature
on the natal reef?, (2) what is the response of P. damicornis larvae to conditions of
decreased pH and warming, measured via two indices of metabolism - rates of oxygen
consumption and citrate synthase activity?, and (3) are there differences in larval
sensitivity to environmental change between cohorts that are released from adult colonies at
different times? P. damicornis larvae were incubated for 6 hours in seawater containing
combinations of CO 2 concentration (450 and 950 μatm) and temperature (28 and 30C). Rates of
larval oxygen consumption were higher at elevated temperatures. In contrast, high CO 2 levels
elicited depressed metabolic rates, most dramatically for larvae released later in the
spawning period. Rates of citrate synthase, a rate-limiting enzyme in aerobic metabolism,
suggested a biochemical limit for increasing oxidative capacity in a warming, acidifying
ocean. Biological responses were also compared between cohorts, larvae released from adult
colonies on the same day. The metabolic physiology of P. damicornis larvae varied
significantly by day of release. Without adaptation or acclimatization, only a portion of
naive P. damicornis larvae may have suitable metabolic phenotypes for maintaining function
and fitness in an end-of-the century ocean. These data are published in
Rivest, E.B. and G.E. Hofmann. 2014. Responses of the metabolism of the larvae of Pocillopora damicornis to ocean acidification and warming. PLoS ONE DOI:10.1371/journal.pone.0096172