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ppt

Abstract

This project continues the retrospective analysis of physical and biological changes in the Gulf of Maine region begun by Greene, Pershing, and colleagues under Phase III. Much of these efforts will focus on understanding the causes and consequences of the influx of relatively fresh water during the 1990s. Analyses to date have attributed widespread shifts in the Gulf of Maine and Georges Bank ecosystem to this freshening. By increasing stratification, the freshwater allowed for stronger and more persistent autumn phytoplankton blooms. The increased phytoplankton production supported larger populations of zooplankton that, in turn, contributed to the recovery of herring stocks. The increase in herring likely contributed to a decline in the older life history stages of the dominant copepod species, with adverse impacts on reproduction in the endangered right whale. These results highlight the importance of autumn, a season that has received little attention from the oceanographic community, and demonstrate a novel mechanism by which climate change can impact marine ecosystems.

Under Phase IVb, Greene et al. will conduct a review of conditions in the Labrador Sea and Arctic Ocean and examine the hypothesis that the 1990s freshening in the Gulf of Maine is a manifestation of Arctic climate change. This project will hold a workshop in November 2006 to consider these questions as well as the relative importance of top-down vs. bottom-up processes in structuring the Gulf of Maine ecosystem. This project will also extend the retrospective analysis downstream to the Middle Atlantic Bight, and will use the Oleander CPR data to compare ecosystem changes in this region with those in the Gulf of Maine.