Biological investigations off the Oskarshamn nuclear power station during the 1980's

The Oscarshamn power station consists of three nuclear reactors, of which the first came into production in 1972 and the last in 1985. The power station uses large volumes of cooling-water; altogether 100 m3/s is heated 10 degrees C. During the 1970's, the investigations of the ecological effects of the use of cooling-water had a wide coverage, whereas during the 1980's, the years treated here, the investigations have mainly been concentrated on fish and bottom fauna. The temperature increase stimulates growth of many organisms and causes attraction. The cooling-water plume and the counter-currents it causes increase the transports of nutrients. The concentration of nutrients in different ways contributes to increased production further up in the food chains and strengthens the attraction of fish. The losses of fish in the cooling system have been relatively small. The parasitization frequency of eels in the receiving bay is extremely high, but otherwise there have been no abnormal disease or parasite attacks. Disturbances to the reproduction of fish in the heated water are present. The importance of this, particularly for surrounding areas, should be investigated within the continued monitoring. (authors)