Field studies have shown for the first time that several common species of seaweeds in both the Pacific and Caribbean Oceans can kill corals upon contact using chemical means.
While competition between seaweed and coral is just one of many factors affecting the decline of coral reefs worldwide, this chemical threat may provide a serious setback to efforts aimed at repopulating damaged reefs. Seaweeds are normally kept in check by herbivorous fish, but in many areas overfishing has reduced the populations of these plant-consumers, allowing seaweeds to overpopulate coral reefs.
A study documenting the chemical effects of seaweeds on corals was scheduled to be published May 10, 2010 in the early edition of the journal Proceedings of the National Academy of Sciences (PNAS). The research was supported by the National Institutes of Health, the National Science Foundation, and the Teasely Endowments at the Georgia Institute of Technology.
"Between 40 and 70 percent of the seaweeds we studied killed corals," said Mark Hay, a professor in the School of Biology at Georgia Tech. "We don't know how significant this is compared to other problems affecting coral, but we know this is a growing problem. For reefs that have been battered by human use or overfishing, the presence of seaweeds may prevent natural recovery from happening at all."
Coral reefs are declining worldwide, and scientists studying the problem had suspected that proliferation of seaweed was part of the cause perhaps by crowding out the coral or by damaging it physically.
Using racks of coral being transplanted as part of repopulation efforts, Hay and graduate student Douglas Rasher compared the fate of corals from two different species when they were placed next to different types of seaweed common around Fijian reefs in the Pacific and Panamanian reefs in Caribbean. They planted the seaweeds next to coral being transplanted and also placed plast
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Georgia Institute of Technology Research News