The changing ecology of temperate coastal waters during a warming trend

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In the temperate North Atlantic Ocean the ecological changes in coastal waters associated with a warming period in the 1930s were compared with the past couple of decades when the North Atlantic Oscillation was also positive. Long-term monitoring data sets from Rhode Island and nearby coastal waters were used to identify trends in the recent warming period. During both events winter water temperatures warmed above a mean value of 2.9°C from 1°C to 3°C. There was no apparent trend in the annual salinity cycle correlated with the increased temperature. During both periods boreal species declined, southern species increased, and widespread declines in eelgrass occurred. Estuaries on the western Atlantic Ocean during the recent warming period had phytoplankton biomass during the winter-spring bloom decrease, zooplankton number increase, and nutrients remain elevated due to enhanced zooplankton grazing. Zooplankton numbers decreased in summer due to enhanced ctenophore predation. In these waters the loss of boreal demersal fish has been compensated by an increase in demersal decapods. The very large ecological changes caused by small increases in seasonal temperature provide an insight to the large alterations that may be associated with global warming.

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