Understanding coral responses to environmental change is critical to predicting their health and future distribution. While tropical and subtropical corals generally experience limited environmental changes, temperate corals undergo pronounced seasonal cycles in irradiance, temperature and nutrients. Their ability to cope with environmental changes makes temperate organisms an ideal model to investigate the effects of global change on coral physiology.
Using the two symbiotic Mediterranean corals, Cladocora caespitosa and Oculina patagonica, we studied the effects of natural changes in light and temperature on their physiological responses both in laboratory and in situ. Temperature was shown to be the major factor affecting coral metabolism. Photosynthetic and growth rates were maximal under normal summer temperatures up to a physiological threshold after which very high temperatures induced, in both coral species, a severe decrease in the rates of photosynthesis and growth. Coral response to high temperatures was species-specific, and highly dependent on the amplitude and length of the temperature stress. These results, together with the observations of recurrent mass-mortalities during recent summers suggest that endemic Mediterranean corals are living near their upper thermal limits. A second study assessed the effects of seasonality, thermal stress (+ 3 °C) and ocean acidification (700 μatm; end-of-century prediction) on the coral C. caespitosa. Corals were collected at 30 m depth and maintained in aquaria over a one-year period under experimental conditions. Surprisingly, calcification and photosynthetic rates were not affected by the high pCO2 conditions, while the seasonal change in temperature had significant effects.
Rodolfo-Metalpa, R., and Ferrier-Pagés, C., 2009. Physiological responses of Mediterranean corals to temperature and pH perturbations. Comparative Biochemistry and Physiology – Part A: Molecular & Integrative Physiology 153(2): 168. Abstracts of the Annual Main Meeting of the Society of Experimental Biology, 28th June – 1st July, Glasgow, UK. Abstract.
