Joseph Karpos-Maravigli takes a rest during a walk through a semitropical rain forest in St. Croix with Katy Kolker, Chris Nytch, and Karla Parsons-Hubbard.
			Reefs through Time and Space: Winter Term in St. Croix By Marci Janas
	Beth Spalding, Katy Kolker, and Kellly Berry work on a fossil reef.		FEBRUARY 28, 2000--Leonardo DiCaprio was not spotted on the beach in St. Croix last month, but 14 Oberlin College students were. They participated in Reefs through Time and Space, a Winter Term project sponsored by Karla Parsons-Hubbard, assistant professor of geology. Dennis Hubbard, visiting associate professor of geology (and Parsons-Hubbard's husband), also accompanied the group, which spent two weeks in the Virgin Islands studying the biology and geology of modern coral reefs--above and below the sea's surface--and comparing their development to that of ancient reefs. In geological terms modern and ancient don't mean what they mean in common parlance. Dennis Hubbard has drilled through many of the modern reefs around St. Croix, extracting corals and sending them away to be radiocarbon dated. Parsons-Hubbard says the dates show the modern reefs began accreting about 10,000 years ago. "Reefs can be quite long-lived if environmental conditions don't change too fast." The couple compared the modern reefs offshore to two ancient fossil reefs exposed on land, one from the Pleistocene age (about a million years old) and one from the Miocene age (about 15 million years old). Parsons-Hubbard reports that they discovered the same environmental controls--wave and light energy--at work in both fossil reefs. "Different types of coral are adapted for high wave energy than those adapted to low wave energy, and distribute themselves differently depending on these factors," she says. Sedimentation does not occur, for example, on corals in high-energy zones; corals in quiet water have a problem with sediment collecting on them. Likewise, corals that become sediment covered, or that settle in deep, dark zones, don't do as well, she says. "Corals rely on photosynthetic dinoflagellates (minute organisms) within their tissues to supplement their nutrition." Parsons-Hubbard says that St. Croix reveals several types of coral reefs, all within easy reach of the beach. "The students were able to snorkel over these various reef types," she says, and to examine "why reefs are different in different locations." Some of the questions they investigated concerned why certain corals are found at certain depths, and what controlling factors contribute to coral growth. All of this study and exploration is important because changes in reef health and development are possible indicators of larger changes in the global environment. "We saw a lot of coral damage on the trip," says Parsons-Hubbard. "Much of the damage has been caused by disease that has seriously affected corals." The question then becomes Are these diseases linked to human effects? Making this sort of determination is difficult, she says. "In the 1980s, many of the hypotheses concentrated on high nutrient loads due to runoff from near-shore construction and sewage dumping. Many of the patterns of coral disease, however, don't follow patterns that you would expect if the problem were entirely human induced. For example, you would expect heaviest coral damage downstream from sewage outfalls, but this is not always the case. These diseases seem to have a less-easily isolated cause." Could climatic change--global warming and increased levels of carbon dioxide in the upper atmosphere--be a factor? "Certainly," says Parsons-Hubbard. "Corals are adapted to fairly narrow temperature ranges. When it gets too warm, they will be more susceptible to disease." Two of the students who went to St. Croix have also been helping Parsons-Hubbard in various aspects of her own research. Students considering spending next Winter Term engaged in such tropical research should be willing to think, says Parsons-Hubbard, in broad, multidisciplinary terms. "Any ecosystem is a product of physical, biological, and chemical processes. Students interested in this type of field research need a background in biology and geology as well as a good grounding in mathematics, particularly statistics, and chemistry. Attempting to reconstruct ancient environments requires cross-disciplinary thinking."
			Julie Fritz snorkels in St. Croix.
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