Eutrophication in the Neva Estuary (Baltic Sea): response to temperature and precipitation patterns

Estuaries provide valuable ecosystem services but are threatened by eutrophication caused by increasing nutrient concentrations and climatic factors. We tested the hypothesis that cool and rainy weather in midsummer has a stronger stimulatory effect on indicators of eutrophication in the Neva Estuary than warm weather. The analysis showed that the concentration of total phosphorus in the estuary was positively correlated with the amount of precipitation and the number of rainy days in the region. Significant positive relationships were found between precipitation in midsummer and chlorophyll concentrations and plankton primary production in the upper part of the estuary. Chlorophyll concentrations and plankton primary production were higher in years with a rainy and cool July than in years with warm and dry July. Such conditions could negate existing measures to improve water quality in the Neva Estuary, meaning that greater effort will be needed.