Marine & Environmental Sciences Faculty Articles

Possible Refugia for Reefs in Times of Environmental Stress

ORCID

0000-0002-6003-9324

ResearcherID

F-8807-2011

Document Type

Article

Publication Title

International Journal of Earth Sciences

ISSN

1437-3254

Publication Date

9-1-2003

Keywords

Coral reef, Upwelling, Reef health, Sea surface temperature, Bahamas, South Africa, Red Sea, Cayman Islands, Refuge

Abstract

This paper investigates the refuge potential of (1) upwelling areas, (2) coral areas at medium depth, and (3) offshore bank and island reefs in a scenario of increased global warming, and thus increased sea surface temperature (SST) and increased solar UV radiation. (1) Observations on coral health and water temperature in the subtropical Atlantic (Eleuthera and Cat Island, Bahamas) and Indian Ocean (Sodwana Bay, South Africa) suggest a link between cool water delivered by upwelling and coral health. After the 1998 bleaching event, caused by strong SST anomalies, coral health and recovery from the previous year's bleaching was significantly better on the narrow southern Cat Island shelf (70% of corals healthy) where the presence of cold water was observed, which was attributed to small-scale upwelling, than on the wide northern Eleuthera shelf (44% of corals healthy), where downwelling of hot bank waters was believed to have damaged corals. In South Africa, regular, short-term upwelling events in five summers reduced SST to well below bleaching level. (2) In the northern Red Sea (Safaga Bay) and in South Africa (Sodwana Bay), wide areas with either coral frameworks or non-framework communities exist. Calculations show that if the top 10 m (20 m) of the ocean became inhospitable to corals, still 50.4% (17.5%) of the coral area would remain intact in the Red Sea and 99% (40%) in South Africa. (3) Offshore bank and island reefs investigated in the Turks, Caicos, and Mouchoir Banks and Grand and Little Cayman showed high rates of mortality and coral diseases. The most remote sites (Mouchoir Bank) were not the healthiest. Refuge areas appear to exist in (1) and (2), but in (3) only if vigorous water-circulation is encountered.

DOI

10.1007/s00531-003-0328-9

Volume

92

Issue

4

First Page

520

Last Page

531

Comments

©Springer-Verlag 2003

Additional Comments

Austrian Science Foudnation grant #: P13165-GEO; NOAA grant #: NA16OA1443

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