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The importance and problems of nutrient flux measurements to study eutrophication of the northern Adriatic

The knowledge of nutrient budgets is the basic step in the study of the relative importance of the processes controlling the biogeochemical cycles of major plant nutrients. This knowledge is particularly important in regions in which anthropogenic eutrophication is significant. Preliminary nutrient budget calculations suggested that the northern Adriatic ecosystem may be especially sensitive to seasonal and long-term variations of external nutrient loads. More recent data were used to verify this assumption and to propose research activities for the future. Several parameters related to eutrophication (salinity, dissolved oxygen, nutrients, and photosynthetic activity) were monitored in the period 1980-1992 at six stations in the open northern Adriatic along a profile between Rovinj and the Po River delta. The sampling and analyses were performed by methods widely used in oceanographic research. During the eighties the orthophosphate concentration in the northern Adriatic decreased in response to a reduction of the Po River load. This reduction was reflected to the primary production rate in the region, but could not explain the changes observed in the dissolved oxygen cycle during the eighties. In fact, a reduction of water exchange rate, due to unusual meteorological conditions, was probably the primary cause of near-anoxia events, which occurred with an increasing frequency in the late eighties.

nutrient flux ; eutrophication ; northern Adriatic Sea

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