RECENT INCREASE OF THE CALCIUM CONCENTRATIONS IN BALTIC SEA WATERS

The Baltic Sea is a large brackish water-system with an annual river i nput of similar to 480 km(3) or similar to 2.2% of the Baltic Sea volu me. Systematic studies on the chemical composition of Baltic Sea water s achieved some decades ago proved significant anomalies for most of t he major constituents when compared with ionic ratios in ocean waters. We compare a present-day (1994/95) analysis of the calcium concentrat ions with our 'historical' data set from 1968-1970. The finding shows a mean Ca concentration increase of about 4% (compared to the analytic al precision of +/-0.08%) which corresponds to an increase of the over all average Ca flux via the freshwater from 3.1 to 4.5 g m(-2) yr(-1) within the past similar to 25 years. The results suggest that this tem poral change is man-induced and has an acidic character. The study sho ws that even the major chemical composition of large water bodies such as the Baltic Sea can be disturbed within a few decades when 'global' perturbations are effective in the drainage area. (C) 1997 Elsevier S cience Ltd.