The Effects of Habitat on Coral Resistance and Resilience to Bleaching.

Abstract

This study examines the bleaching responses of scleractinian corals at four sites in Kenya (Kanamai, Vipingo, Mombasa Marine Park and Nyali) representing two distinct lagoon habitats (relatively shallow and relatively deep). Bleaching responses were monitored for the general coral community and zooxanthella densities and chlorophyll levels were monitored for target species (Pocillopora damicornis, Porites lutea and Porites cylindrica ) during a nonbleaching year (2006) and a year of mild bleaching (2007). The objective of this study is to determine whether corals in different habitats display varying resistance and resilience to bleaching stress and to indicate which environmental characteristics are responsible for the variation in response. Considerable differences in bleaching responses between shallower and deeper lagoon sites were observed, with shallower sites Kanamai and Vipingo exhibiting much lower bleaching and paling incidence than deeper sites Nyali and Mombasa Marine Park. These shallower lagoons display much more fluctuating thermal and light environments than the deeper sites, with higher maximums, lower minimums, higher standard deviations and higher diel variation. These results suggest that corals in the shallower lagoons have acclimatized and/or adapted to the fluctuating environmental conditions they endure on a daily basis and have become more resistant to bleaching stress. Furthermore, in deeper sites that did exhibit significant bleaching (Mombasa Marine Park and Nyali), it was found that coral recovery occurred more quickly in the protected area compared to the nonprotected area.