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Sea surface temperature and surface chlorophyll data exhibit a large
amount of internal variability, but there is an indication in recent
years of a cooling trend in shelf-wide SST and a reduction in surface
chlorophyll. There was no appreciable trend in SST until the late
1990s, when temperatures began to increase. The data suggest a peak
in SST around the year 2000, followed by a decreasing trend through
2006. Estimates of chlorophyll concentration are derived from remotely-sensed
measurements made by the SeaWiFS sensor which began operation in
September 1997. The available time series in chlorophyll mirrors
SST, with a decline evident in the trend line for recent years;
however, the measurement in 2006 indicated an increase in shelf
chlorophyll.
Data on total zooplankton abundance is available
from 1977. There is also substantial variability in zooplankton
biomass, as represented by a biovolume measurement, yet a long-term
trend is apparent. Zooplankton biomass decreased through the late-1970s
and into the 1980's, and has since increased.
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