The waters of the MAB undergo the typical annual temperature cycle characteristic of temperate regions. Temperature warms in spring to a summer maximum, followed by gradual cooling until the winter minimum is reached. Waters become stratified in spring and summer with a warm surface layer underlain by a distinct thermocline. Beneath it is a layer of cooler water called the "cold pool" (Bigelow, 1933) , which persists until the normal seasonal overturn. The average seasonal and interannual

more »

... ns of circulation, temperature, and salinity have been described for the region in several previous studies (e.g. Bigelow, 1933; Manning, 1991; Mountain, 2004) . There is a growing body of evidence that climate related and anthropogenic processes are altering Northwest Atlantic marine ecosystems (Frank et al., 2005; Greene and Pershing, 2007; Nye et al., 2009) . Zooplankton community structure in the Gulf of Maine and on Georges Banks shifted to a greater dominance by smaller sized species when salinity decreased during the early 1990s