Radiocaesium in algae from Nordic coastal waters

The results are presented from surveys of radiocaesium concentrations (137Cs and 134Cs) in the brown alga Fucus vesiculosus from Nordic coastal waters (Finland, Sweden, Norway, Denmark, Iceland) and in epilithic diatom communities from the Swedish part of the Gulf of Bothnia in 1991. The Baltic Sea was significantly contaminated by the Chernobyl accident, and radiocaesium from the accident was still predominant in radiocaesium concentrations in the algae here after five years. The general fallout pattern was still reflected, with highest concentrations in the southern Bothnian Sea. Between 1987 and 1991 the radiocaesium concentrations decreased, except for the area between Sweden and Denmark at the outflow from the Baltic Sea, where increased concentrations were found at a number of sites. This may indicate that radiocaesium is being transported out of the Baltic Sea. F. vesiculosus is a good and often used indicator of radioactive discharges into Nordic coastal waters, but in the northern Baltic Sea it is absent because of the low salinity (< 5 permille). In this area we used instead epilithic diatom communities, which proved to be a good alternative to F. vesiculosus for monitoring radioactive discharges in areas with low salinities. (orig.)