Tallinn Bay Gulf of Finland Latitude:   59.5370     Longitude:   24.6880 Associated Investigators: Arno Pollumae   Related Time Series: [ Pärnu Bay ]   [ Tallinn Bay ]   The Gulf of Finland is represented by one HELCOM sampling station located in the middle of Tallinn Bay at 59 32.2'N 24 41.3'E. Zooplankton were collected using vertical hauls of a Juday plankton net (0.38 m mouth opening, 90 µm mesh) up to ten times a year. Zooplankton in the Baltic Sea are typically smaller than elsewhere. The dominant copepod species in Estonian waters are Eurytemora affinis and Acartia bifilosa, the most abundant cladoceran is Bosmina coregoni, and rotifers also constitute a large proportion of the total zooplankton abundance. The maximum zooplankton biomass is usually observed in late summer, corresponding to the warmest water temperatures (Standard Co-sampled Variables Plot). In years with warmer winters, high abundance may be observed in spring, when a shorter period of ice cover causes more mixing and phosphorus release from the bottom, resulting in higher chlorophyll concentrations in spring and summer. This mechanism may also explain the corresponding increase in chlorophyll with temperature over time (Standard Co-sampled Variables Plot) and the slight increase in copepod abundance during the same period. In the long term, water temperatures at the sampling site have been warmer than the 100-year average since 1989 and are currently warmer than the 100-year maximum (Standard Long-term Comparison Plot, bottom, red dashed line).