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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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