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Coral Records of Paleoflooding and Bleaching Events
Finally, graduate student Brendan Roark and I are investigating the history and frequency of past coral bleaching events. Reef building corals may be one of the organisms most sensitive even to relatively small increases in sea surface temperatures. Increases in temperature of only 1°-2° C above the normal maximum average induce severe stress resulting in bleaching or expulsion of the symbiotic algae, often leading to coral death. In the first part of 1998, many such events of unprecedented severity occurred throughout the world’s oceans.
In 1997, Brendan and I, along with our collaborator, Prof. Malcolm McCulloch at the Australian National University in Canberra , began a project documenting longer-term frequency of coral bleaching, to determine whether coral bleaching is a recent phenomenon or part of the longer–term natural cycle. If such events re-occur with higher frequencies as global temperatures increase, many of the world’s coral reefs will be threatened. Coral reef bleaching has been reported since the late 1800s on reefs worldwide, although this phenomenon appears to be increasing in frequency over the past few decades. We are using carbon and oxygen isotopes, as well as minor elements (Sr/Ca, Ba/Ca, etc.) as proxies for past coral bleaching events and associated paleoceanographic conditions, to document coral bleaching in Moorea, French Polynesia and the Great Barrier Reef .
PUBLICATIONS:
Roark, E.B., Guilderson, T.P., Flood-Page, S., Dunbar, R.B., Ingram, B.L., Fallon, S.J., and McCulloch, M., (2005). Radiocarbon-based ages and growth rates of bamboo corals from the Gulf of Alaska. Geophysical Research Letters, 32, LXXXX, doi:10.1029/2004GL021919.
Moore, J. G., Ingram, B. L., Ludwig, K. L., and Clague, D. A. (1996) Coral ages and island subsidence, Hilo Drill Hole, Journal of Geophysical Research V. 101, p.11,599-11,605.
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