5. Dynamics of Gulf Coral Communities: Observations and Models from the World’s Hottest Coral Sea

Coral reefs are adapted to a relatively narrow band of environmental optima and the harsh Gulf environment tests the physiological and ecological limits of reef corals. The environmental variability (minimal and maximal annual temperatures, salinity extremes, etc.; Chap. 2; Sheppard et al. 1992, 2010) are outside the range of typical tropical reefs. Regular summer temperatures are several degrees above the bleaching and mortality thresholds of some regions in the Great Barrier Reef and the Caribbean (Baker et al. 2008; Chap. 6). Yet, corals thrive in the Gulf. However, they have recently been exposed to severe temperature anomalies at a recurrence faster than in any other coral reef region (Riegl 2002, 2003; Sheppard and Loughland 2002; Riegl and Purkis 2009; Sheppard et al. 2010) and it appears that hot-anomalies are increasing in severity and frequency (Nasrallah et al. 2004). Thus, corals in the Gulf already exist in a thermal environment that is equal to, or even worse than, what is predicted (IPCC 2007) as occurring throughout the tropical oceans by 2099 and recognized as likely causing problems for coral reef persistence. Clearly, important lessons can be learned from Gulf corals about environmental extremes that corals can survive and, given the high frequency of disturbances, maybe even lessons in adaptability. Since the world is getting warmer and extremes are becoming more pronounced, the study of such extreme reef systems gains increased relevance.