Fall 2006 Update: Ship of Opportunity Data-Dominant Zooplankton Species

Phytoplankton color index from the Continuous Plankton Recorder transect across the Gulf of Maine is shown in the top panel. The decrease in spring chlorophyll concentration observed from satellites is also evident in the in situ data. Extremely low color indices were observed in the 1960s and early 1970s. There was then a rapid increase until about 1985 when a gradual decrease started. The decrease in color index seemed to accelerate in 2000 and low levels have been observed since. Abundances of two species of copepods from the Gulf of Maine Continuous Plankton Recorder transect are shown. Adult Calanus finmarchicus, which is a key indicator species for ecosystem status in the Gulf of Maine, has recently increases after a period of lower values in the 1990's. Smaller zooplankton, as exemplified by Oithona, have decreased after a period of higher values in the 1990's. These changes are indicators of shifts in community structure from larger bodied copepods, including Calanus in the 1980's, to smaller bodied copepods in the 1990's, including Oithonia, back to larger bodied copepods in the 2000's. The increase in larger-bodied copepods coincides with an increase in total zooplankton biomass during the fall

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(File Modified Apr. 19 2017)