Abstract Summary
Coral reefs are threatened by rising seawater temperatures and ocean acidification. However, some populations of coral can cope with relatively high temperature and pCO2 conditions, which may be a function of their heterotrophic capacity. Reefs surrounding Oahu, Hawai'i, USA vary in temperature and pCO2 conditions reflective of those observed on most reefs today to those not typically expected until mid-century. We hypothesize that corals from sites with elevated seawater temperature and pCO2 will incorporate a greater proportion of heterotrophic carbon into their tissues than corals from sites representative of normal reef conditions. We measured the δ13C values in two dominant species (Montipora capitata and Porites compressa) of coral from four sites around Oahu to determine the proportionate contribution of photoautotrophic and heterotrophic carbon to coral tissues. Preliminary results show that the contribution of heterotrophic carbon to coral tissues is higher in corals from sites with elevated summertime temperatures and pCO2 conditions. These preliminary findings support our hypothesis and suggest that corals in more stressful environments have adapted to those conditions by increasing their intake of heterotrophically derived C as a mechanism to supplement nutritional needs in stressful environments. Overall, this study suggests that corals with higher capacity to incorporate heterotrophic carbon into their tissues may be good candidates for coral conservation efforts as they might have greater potential to cope with future ocean conditions.
