Annual variability of phytoplankton primary production in the western basin of Lake Erie (2002-2003)

Carbon fixation regulates the biological production capacity of lakes. To assess the phytoplankton production capacity of western Lake Erie, primary production was monitored in situ every other week at Middle Sister Island from spring to early autumn in the years 2002 and 2003. Physical parameters (light penetration, temperature, and dissolved oxygen), chlorophyll a, and major nutrients (total phosphorus and nitrate) were also measured. A decrease in primary production, based on monthly weighted means, was observed in summer 2003 (0.04-0.78 g C(.)m(-2.)d(-1)) when compared to 2002 (0.65-2.06 g C(.)m(-2.)d(-1)), correlating well with a reduced and more variable depth of the euphotic zone. Chlorophyll a and total phosphorus concentration, however, were higher in 2003. These data demonstrated that changes in carbon fixation are regulated by short and long term variability in the underwater light climate of the western basin of Lake Erie that are associated with wind events.