Zooplankton entrainment at Swedish nuclear power plants

Studies on zooplankton entrainment with the cooling-water at four Swedish nuclear power plants demonstrated that mortality of crustaceans caused by mechanical damage and temperature elevation was low. Chlorination against fouling organisms, however, occasionally caused raised mortality. The greatest effect found on the zooplankton communities was caused by filter feeders attached to the walls of the cooling-water systems. Up to about 50% of the plankton was filtered off, and the effect was positively related to the lengths of the cooling-water tunnels. Delayed mortality was low in most taxonomical groups except in the cladocerans. As the volumes of water passing through the cooling-water systems are very large, the effect on the zooplankton community was considered as severe. At one of the plants the estimated yearly average loss of crustacean zooplankton was some hundred tons.