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Climate Change Paper Published in Science

May 17, 2007

In a paper published in a recent issue of the journal Science, Andrew Pershing, of the UMaine School of Marine Sciences and the Gulf of Maine Research Institute, and Charles Greene, of Cornell University’s Ocean Resources and Ecosystems Program, state that significant changes in the marine ecosystems of the Northwest Atlantic are the result of a significant increase in meltwater entering the ocean due to climate change.

Pershing and Greene suggest that the increase in low-salinity water entering the Atlantic from the Arctic altered circulation and stratification patterns, resulting in what they refer to as an ecosystem regime shift: a large, relatively rapid alteration in the ecosystem at multiple levels. The shift was marked by significant changes in the abundances and seasonal cycles of phytoplankton, zooplankton, and fish populations.

“Around 1990, the abundance of small copepods--rice grain sized crustaceans that are food for small fish--increased a hundred fold”, said Andrew J. Pershing, Ph.D., Ecosystems Modeler at the Gulf of Maine Research Institute and Professor at UMaine School of Marine Sciences. “Our work suggests that the increase in copepods was caused by an increase in the amount of freshwater entering the Gulf of Maine. When saltier conditions returned around 2001, the changes we saw reversed.”

Dramatic changes in the abundance of herring, shrimp and other species in the 1990s have been attributed by some to the reduction in predation by cod and other large fish following the collapse of groundfish populations in the 1980s. Pershing and Greene suggest that a bottom-up change in the populations of a variety of North Atlantic species would have occurred with or without the collapse of cod, due primarily to significant changes in climate.

“Climate scientists are predicting that the North Atlantic will get fresher, due to more precipitation and ice melt. While we can't say that conditions in the 1990s were caused by global warming, our work suggests a new way that global warming could impact marine ecosystems.”

Pershing, who received his Ph.D. in ecology from Cornell in 2001, is a leader in the use of computing technology to model and visualize how the ocean environment influences fish and mammal populations over time and to predict potential future population changes.
Marine Science

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