engleski

When do phytoplankton blooms cause the most intense hypoxia in the northern Adriatic Sea?

Eutrophication of the northern Adriatic Sea was investigated using data on dissolved oxygen (DO) from 1911 to 1982. Beginning in the period 1955-1965, DO concentrations increased in the surface layer and decreased close to the bottom in all seasons except winter. These changes are attributed to an increase of the anthropogenic nutrient inflow. The occurrence of hypoxia near the bottom and its disappearance were investigated using the vertical distribution of DO on the transect from the Po delta to Rovinj during 1973. Horizontal distributions of DO close to the surface and near the bottom show prominent gradients from the Po delta towards the middle of the northern Adriatic Sea. Application of a simple box model indicates that phytoplankton blooms which occur in July cause the lowest DO concentrations near the bottom. For DO concentrations near the bottom to increase, anthropogenic nutrient inflow into the northern Adriatic Sea must be significantly reduced.

hypoxia; phytoplankton bloom; nutrients; eutrophication; Adriatic Sea; organic carbon; anoxia

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