The Effects on Inorganic Nutrients

FIGURE 10.15 Long-term variation of phosphate concentrations in the central Baltic deepwater. 

THE INFLOW OF HIGHLY SALINE WATER INTO THE BALTIC SEA 

The Bornholm Basin deepwater, which is frequently influenced by each baroclinic or weak barotropic inflow event (cf. Section 10.2), is renewed annually to a certain extent. Consequently, anoxic conditions cannot be observed as often and persistent as in the subsequent basins. The phosphate and nitrate concentrations mirror these frequent changes between oxic and anoxic conditions. The relatively low phosphate values in the 1960s suggest that oxic conditions prevailed during this period. 

Not all inflows are able to propagate into the central Baltic basins because the Bornholm Basin acts as a buffer (cf. Section 10.2). Moreover, the effects of MBls are reduced, and they proceed more slowly in the subsequent basins due to the increasing volume of deepwater. Therefore, reactions of the nutrient regime to MBls can be best studied in these basins. The changes in the nutrient distribution are thus described in detail more for the near-bottom water layer of the Eastern Gotland Basin (Fig. 10.18). 

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