In-situ measurement of metabolic status in three coral species from the Florida Reef Tract

Abstract

The goal of this study was to gain an understanding of intra- and inter-specific variation in calcification rate, lipid content, symbiont density, and chlorophyll a of corals in the Florida Reef Tract to improve our insight of in-situ variation and resilience capacity in coral physiology. The Florida Keys are an excellent place to assess this question regarding resilience because coral cover has declined dramatically since the late 1970s, yet has remained relatively high on some inshore patch reefs. Coral lipid content has been shown to be an accurate predictor of resilience under stress, however much of the current lipid data in the literature comes from laboratory-based studies, and previous in-situ lipid work has been highly variable. The calcification rates of three species were monitored over a seven-month period at three sites and lipid content was quantified at two seasonal time points at each of the three sites. Montastraea cavernosa had the highest mean calcification rate (4.7 mg cm−2 day−1) and lowest mean lipid content (1.6 mg cm−2) across sites and seasons. In contrast, Orbicella faveolata and Porites astreoides had lower mean calcification rates (2.8 mg cm−2 day−1 and 2.4 mg cm−2 day−1, respectively) and higher mean lipid contents (3.5 mg cm−2 and 2.3 mg cm−2, respectively) across sites and seasons. Given the recent Endangered Species Act (ESA) listing of O. faveolata and the relative persistence of M. cavernosa and P. astreoides on a population-scale, this study suggests that the hypothesis that coral lipids are good indicators of resilience may be species-specific, or more complex and interrelated with other environmental factors than previously understood. Additionally, coral lipid storage under benign thermal conditions may differ from lipid storage before, during, and after thermal stress events.