The Northeast Shelf ecosystem is among the more productive of the world's 64 Large Marine Ecosystems (LMEs). The most recently measured ecosystem wide levels of zooplankton and primary productivity are close to the long term mean (1986 - 2006) of 40 cc 100m^-3 and 337 gC m^-2 y^-1, respectively. However, spatial and temporal variability has been observed among subareas and seasonal pulses of the LME in zooplankton, chlorophyll, and primary productivity are described in this Advisory.

• Sea surface temperature and surface chlorophyll data exhibit a large amount of within and between year variability, but there is an indication in recent years of a warming trend in shelf-wide SST during fall. Inter-annual variability in fall levels of chlorophyll has been large, making it difficult to discern a shelf-wide trend; however, the northern areas of the shelf have had depressed chlorophyll levels in recent years, whereas the southern areas of have shown an increase.
  
  
• 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 during fall is increasing in some areas and decreasing in others.
  
  
• Long term trends (1854-2006) in SST show that the NE Shelf Ecosystem is warming, both in terms of annual mean and fall temperatures, but SST has been higher in the past. These same analyses show that the summer to winter range in temperature is at its highest level recorded, suggesting that the ecosystem is experiencing extreme ranges in temperature and rapid heating and cooling rates.
  
  
• Ship of opportunity data shows that in situ chlorophyll trends in the Gulf of Maine match those observed in the satellite data, suggesting a decline in fall phytoplankton. The principal fall zooplankton species, Centropages typicus and Oithonia, have also declined in recent years.
  
  
• Analysis of regional phytoplankton cycles shows that there is a high degree of year to year variability in seasonal bloom and phytoplankton concentrations. In the northern part of the ecosystem, the fall bloom in the Gulf of Maine and on Georges Bank has declined and even failed to develop in some years. In the southern areas the trends are less well developed.