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Research Document - 2004/074

The 1990s a Unique Decade for Plankton Change in the Northwest Atlantic

By Sameoto, D.

Abstract

Continuous Plankton recorder data collected between Iceland and New England between years 1959 and 2001 showed that the 1990s decade was one in which large changes in the abundance of phytoplankton and zooplankton occurred. Total diatoms and dinoflagellates increased in the 1990s in the western North Atlantic and along the Scotian shelf, whereas the abundance of C.  finmarchicus stages 1 to 4 decreased on the western North Atlantic and Scotian Shelf zones. In the eastern North Atlantic (east of longitude 45°W), the abundance of C. finmarchicus stages 1 to 4 did not decline in the 1990s. In the 1990s the yearly fluctuations in the phytoplankton color index were similar in the western North Atlantic, Scotian Shelf and Georges Bank zones. However, the pattern of yearly change on the eastern North Atlantic was lower and different from those seen on the other zones. The changes observed in the 1990s were due to changes in abundance of the taxa in the early and late months of the year with little change seen during the summer and early fall months. January to March 1998 and 1999 had the largest positive diatom deviations from the monthly means in the 1991 to 2001 decade, and 1999 was a year of exceptionally high haddock recruitment on the Scotian Shelf.

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