Upwelling Areas as Possible Refugia for Reefs in Times of Rising SST? Further Evidence from the Caribbean and Indian Oceans

A link seems to exist between upwelledcool water and coralhealth in Eleuthera, Cat Island (Bahamas) and Sodwana Bay (South Africa). In 1999, coralhealth and recovery from the 1998 bleachingwas better in Cat Island than in Eleuthera (70% versus 44% of coralshealthy). The southern Cat Island shelf is narrow and reefsare protected from bank waters by the island. Upwellingwas observed in the field and on satellite imagery. The northern Eleuthera shelf is wide, and reefsare influenced by bank waters ( downwellingof hyperpycnal waters). In hot years, when oceanic and bank waters get heated beyond bleachingthreshold, upwellingprotects Cat Island reefs. South African reefsare protected from high temperatures by annual upwellingin summer. Therefore, even during the 1998 world-wide bleachingevent, <1% of South African corals bleachedand coralcover did not decrease. Upwellingmay create refugia for reefsin times of increased sea surface temperature. 1 Institut fur Geologie und Palaontologie, Universitat Graz, Heinrichstrasse 26, 8010 Graz, Austria 2 NCRI Oceanographic Center, Nova Southeastern University, 8000. Ocean Drive, Dania 33004 Florida, USA; email : reiglb@nova.edu