Oceanologia (Mar 2003)
Seasonal dynamics of phytoplankton in the inner Neva Estuary in the 1980s and 1990s
Abstract
The phytoplankton in the inner Neva Estuary is described from data obtained from 1996 to 2000. The seasonal dynamics of the phytoplankton biomass are characterized by a bimodal curve with a summer maximum. The average seasonal biomass was approximately3 mg l-1, the maximum biomass was 8-11 mg l-1. The species composition and quantitative parameters were compared to those observed in the 1980s. A notable, nearly 1.5-2 fold, increase in the biomass in the summer-autumn period and the predominance of Oscillatoria species among the blue-greenalgae were observed. A decline in the nutrient load in the water body at the end of the 1990s appeared to be insufficient to bringabout a decrease in the proportion of Oscillatoria algae in the total species composition or a decline in the biomass ofthe entire phytoplankton community. In 2000 a certain change in the structural composition of the phytoplankton complex was noted. Species that had been predominantin the 1980s and had lost their advantage in the early 1990s, regained their earlier status.
