Spring 2008 Update: Summary of Conditions of the Northeast Shelf Ecosystem
Sea surface temperature (SST) in the Northeast Shelf Large Marine Ecosystem was cooler in 2007 as compared to the trend in recent years, though SST varied by subregions within the ecosystem. Spring bloom production was well above average; however, summer productivity and the fall bloom were only at average levels. Zooplankton biomass began the year at below average levels, but by summer and fall began to exceed recent trends, perhaps reflecting the added productivity in the system resulting from the robust spring bloom earlier in the year.
- Sea surface temperature in respect to recent term trends (1985-2006) was cooler in all seasons on Georges Bank; in contrast it was warmer in the Middle Atlantic Bight area, especially during winter and fall. The Gulf of Maine was also warmer during those periods, but not to the same extent as in the Bight.
- There was an intense spring bloom on the Northeast Shelf owing to well developed blooms in the Gulf of Maine, Georges Bank and Southern New England areas. A relative weak fall bloom was observed in the Gulf of Maine and despite relatively high chlorophyll concentrations, the George Bank fall bloom never fully developed.
- Zooplankton biomass during fall was at or above historical levels across the ecosystem as a whole. Regionally, zooplankton biomass was near average levels in the Gulf of Maine and Georges Bank while biomass was above average levels in Southern New England and Middle Atlantic Bight
- The dominant zooplankton on Georges Bank exhibit contrasting patterns. Calanus finmarchicus has been increasing in abundance in recent years, but 2006 was lower relative to the previous three years. However, there have been marked decreases in the abundance of Centropages typicus and Temora longicornis in recent years, but 2006 was higher relative to the previous three years.
- Long term trends (1854-2007) in SST show that the NE Shelf Ecosystem is warming, especially in the Gulf of Maine, Georges Bank and Southern New England subregions. The Middle Atlantic Bight does not show the same overall warming trend largely due to a continuing trend of cool winter conditions.
- Analysis of mean length of finfish captured in the NEFSC trawl survey suggest that average fish size has declined in the Gulf of Maine and Southern New England subregions of the Northeast Shelf; however, despite dramatic changes in the population levels of stocks, fish size has remained remarkably constant on Georges Bank.