Fall 2006 Update: Summary of Spring Conditions of the Northeast Shelf Ecosystem
This advisory is an examination of satellite remote sensor and in situ survey data related to the plankton of the Northeast U.S. Shelf ecosystem. Specifically, we report on the sea surface temperature (SST), chlorophyll concentration, and zooplankton biomass. These are ecosystem wide environmental measurements. The results can best be interpreted with other physical and biological data to provide a complete description of the 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 2005. 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 recent years.
Data on total zooplankton abundance is available from 1977. There is also substantial inter-annual variability in zooplankton biomass, as represented by a biovolume measurement, yet a long-term trend is apparent. Zooplankton biomass decreased through the late-1970s, remained at relatively constant levels from about 1980-1995, and increased after 1995. 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.