COMBINED EFFECTS OF PCO2 AND IRRADIANCE ON THE ENERGY RESERVES AND CALCIFICATION OF A REEF BUILDING CORAL
Ocean acidification (OA) from increased concentrations of pCO2 in seawater is predicted to reduce calcification rates in reef corals, and may affect the storage and metabolism of physiologically important energy reserves (lipids, carbohydrates, proteins). Irradiance levels affect the bioenergetics of reef corals, and the effects of OA are modulated by light availability. However, the interactive effects of OA and irradiance on coral biomass energy reserves are not well understood. This study used fragments of the reef coral Pocillopora damicornis from Kane'ohe Bay, Hawai'i, to test for light (400 vs. 800 umol photons m-2 s-1) and pCO2 (435 vs. 961 uatm) effects on calcification, symbiont and chlorophyll densities, and the composition (lipids, carbohydrates, protein) and energy content (kJ) of coral biomass. Fragments (N = 168) from seven adult coral colonies were exposed to treatments in 24 flow-through aquaria (n = 6 replicate tanks/treatment) for 32 d. Results revealed no effect of pCO2 or irradiance on net calcification or symbiont density. Carbohydrates/gdw increased under high light, but high pCO2 reduced lipids/gdw and biomass energy (kJ/gdw) and protein/cm2 was reduced under high light and high pCO2. These findings suggest OA will interact with irradiance to affect the composition and energetic content of coral biomass in this ecotype of P. damicornis. However, under ecologically relevant irradiances P. damicornis may be resistant to the OA-driven reduction in calcification reported for other reef corals.
Wall, C. B., University of Hawaii at Manoa, USA, email@example.com
Ellis, W., Northeastern University, USA
Mason, R., University of Queensland, Australia
Cunning, R., University of Hawaii at Manoa, USA
Gates, R., University of Hawaii at Manoa, USA
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