Spring 2007 Update: Annual Conditions of the Northeast Shelf Ecosystem
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.
Although these data suggest an overall increase in secondary production and a decrease in temperature and phytoplankton biomass, regional and temporal dynamics must be considered in the assessment of the entire ecosystem.