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Fall 2007 Update: Summary of Spring Conditions of the Northeast Shelf Ecosystem

This advisory is an examination of temperature and plankton conditions associated with the Northeast Shelf Ecosystem during the spring of 2007.  The spring bloom, and its antecedent winter production period, is pivotal to the recruitment process of many resource species.

  • During fall into winter of 2006-2007, sea surface temperature (SST) was warm in the Northeast Shelf Ecosystem, with the exception of Georges Bank where late winter was noticeably cooler. During the spring of 2007, SST tended to be cool in all subregions of the Shelf with the most extreme cooling occurring on Georges Bank.
  • The spring bloom was of higher intensity, i.e. with higher chlorophyll concentrations, in all subregions of the Northeast Shelf Ecosystem. The blooms were of average or less than average duration, so bloom magnitude was not particularly high.
  • Spring blooms in the Gulf of Maine and on Georges Bank had been occurring later in the spring in recent years, however, both the 2006 and 2007 blooms commenced closer to the average bloom start date in both subregions.
  • Zooplankton biomass was at lower levels during the winter of 2006-2007 both for the entire ecosystem and in each of the four subregions. During fall of 2006, ecosystem wide biomass was near average while it was above average in the southern subregions, near average on Georges Bank, and below average in the Gulf of Maine.
  • Springtime abundance of larger phytoplankton is at low levels in the Gulf of Maine, based on the Ship of Opportunity Program color index. Similarly, springtime abundance of smaller copepods (e.g., Oithona spp) is also at lower levels. Abundance of Calanus in the spring, however, remains at or slightly above average.
  • Results of climate change modeling done by the Canadian Centre for Climate Modeling and Analysis suggests that sea surface temperature will increase on the Northeast Shelf. The focus of the highest anticipated change is the Gulf of Maine. Under most climate change scenarios, the Gulf of Maine is expected to increase in temperature on the order of 2-4°C. However, under the scenario with the highest greenhouse gas loading, the change in SST could be as high as 7°C.
  • There has been an increase in cannibalism in the northern stock of silver hake.

Data Sources
Spring Conditions on the Northeast Shelf Ecosystem
Spring Condition by Shelf Subregions
Spring Sea Surface Temperature Distribution
Spring Chlorophyll Distribution
Timing of the Spring Bloom
Ship of Opportunity Data-Dominant Zooplankton Species
Potential Changes in Northeast Shelf Climate
Silver Hake Cannibalism

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