Lipid content in two Montastrea species of coral in the Florida Keys after the 1998 El Niño bleaching event

Abstract

Coral reefs are some of the most sensitive ecosystems to environmental change. With massive declines reported since the 1980s, there are many concerns that they could disappear due to human activities. The most common stress response in corals is bleaching, the breakdown of the symbiosis, which leaves the coral without their main energy source: their symbiotic algae. Without enough energy, corals cannot afford to invest in reef accretion, which creates the basic habitat for reef ecosystems. Differential bleaching severity and mortality has been largely documented, with high temperatures being the main stress. During bleaching, some corals switch symbiont types to a more thermo-tolerant clade, although this might present a metabolic cost. Thermo-tolerant symbionts have been reported as opportunistic generalists, suboptimal to most coral species. A way to assess coral fitness is through the monitoring of physiological parameters such as the lipid content. In this study, lipid content was analyzed in coral tissue samples from Montastrea annularis and Montastrea faveolata collected seasonally in the years 2000-2002 following the 1997-98 El Niño catastrophic bleaching in the Florida Keys. Seasonal variation was observed in most samples. Recovery was visible but slowed down after 2001, and the probable causes for that are discussed. Lipid content was significantly correlated to physiological parameters related to the symbiotic algae, confirming zooxanthellae’s role in the supply of lipids to the coral. M. annularis presented about half the lipids per unit surface, and we suggest that this is due to the many different types of Symbiodinium it contained in contrast to M. faveolata which presented only one type.