Yentsch, C. S.. Bigelow Laboratory for Ocean Sciences, csyentsch@bigelow.org
Phinney, D. S.. Bigelow Laboratory for Ocean Sciences, dphinney@bigelow.org
O'Reilly, J. E.. NOAA/NMFS Narragansett Laboratory, oreilly@fish1.gso.uri.edu

 
SLOPE WATER CHLOROPHYLL BLOOMS OBSERVED WITH SEAWIFS - CAPE HATTERAS TO THE GULF OF MAINE
 
The National Marine Fisheries Service collected extensive seasonal data on coastal and slope water primary productivity from Cape Hatteras to the Gulf of Maine as part of MARMAP survey cruises between 1977 and 1982. The data show an unusual reversed seasonal pattern with a marked transition between higher production in the offshore waters and lower production in the nearshore slope waters of the Northwest Atlantic. Observations by SeaWiFS confirm this pattern and show the transition region as a trough of low chlorophyll water (<0.5 mg/m3) extending from the tip of Cape Hatteras to Georges Bank. The trough is bounded by coastal pigment concentrations >3 mg/m3 and seasonal offshore slope waters with 1-2 mg/m3 in water depths of 200 to 1000 meters. The low pigment trough appears in February and persists through April in SeaWiFS monthly composite images, it is not present during autumn months. The appearance of higher pigment concentrations in the offshore waters which define the boundary of the trough coincides with the spring bloom in the deep basins of the Gulf of Maine. We believe this indicates that the trough is a manifestation of the early stages of spring blooms in coastal and slope waters. Our hypothesis concerning the low pigment trough reflects the interaction of geostrophic forces and resulting nutrient delivery associated with the Gulf Stream and the onset of increased solar radiation in spring.
 
Day: Tuesday, Feb. 2
Time: 08:30 - 08:45am
Location: Sweeney Center
 
Code: SS43TU0830S