Phytoplankton pigment in the Gulf of St. Lawrence, Canada, as determined by the Coastal Zone Color Scanner—Part I: spatio-temporal variability

This study describes for the first time the spatial structure of surface phytoplankton pigments (chlorophyll a plus phaeophytin) in the Gulf of St. Lawrence (GSL), Canada, based on 80 Coastal Zone Color Scanner (CZCS) images taken between April 1979 and September 1981. Pigment concentrations estimated from the satellite images were validated using available concurrent in situ data. In general, broad spatial patterns in the production of the GSL inferred from shipboard measurements, were confirmed. The spatial distribution matched major physical features of the Gulf, with the highest pigment levels in the estuarine region in the northwestern Gulf and the lowest in the more marine eastern Gulf. The CZCS imagery revealed strong year to year variations in the abundance and distribution of pigments, comparable in magnitude to the seasonal variations. Furthermore, the seasonal cycle was dominated by pigment increases in late summer-early fall, not in the spring as is generally expected. Changes in the productivity of the Anticosti Gyre in the northwest Gulf, an area generally considered to be oligotrophic, seemed to dominate the seasonal and interannual signal. These variations could be related to changes in the balance between wind and buoyancy forcing on the circulation