Observations of phytoplankton dynamics in Lake Ontario using ATSR-2 imagery

ATSR-2 gridded brightness temperature data have been used to estimate chlorophyll concentrations in Lake Ontario, North America. Lake truth data were collected during July and October 1995 as part of the Lake Ontario Trophic Transfer (LOTT) project. Epilimnetic chlorophyll a concentration was estimated using in situ fluorometer apparatus and traditional solvent extraction techniques. Nadir and forward looking pixel data were used to derive a chlorophyll estimation algorithm based on a multiple regression of 555, 670, 870 nm and 1.6 μm wavelengths and fluorometer values (r 2 >0.87, p<0.01). ATSR-2 scenes from July 1995 were processed using the algorithm to derive lake wide chlorophyll concentration and distribution. Phytoplankton production generally followed the pattern of surface current circulation, with the highest levels recorded in the south western part of the lake. Images showed chlorophyll distributions changing more rapidly than could be detected by the tri-annual LOTT cruises. Further work incorporating ATSR-2 lake surface temperature maps is planned.