Open access publications in the SLU publication database

The use of cooling water at Ringhals nuclear power plant affects the marine environment. The fish and shellfish community is affected in two steps. In the first step, fish eggs, larvae and larger fish that are transported into the nuclear power plant with the cooling water may face unnatural mortality. In the second step the heated water is released back into the sea, where the fish and shellfish are affected by the increase in temperature. The presence of heated water could also facilitate the establishment of nonindigenous invasive species in the coastal area. Reactors R1, R3 and R4 at Ringhals nuclear power plant produced electricity during the major part of 2016, with exceptions for the annual audits and shorter stops in production. Reactor R2 was closed for almost the entire year. Fish eggs and fish larvae are sampled in the incoming cooling water using a modified Bongo net to monitor losses in the nuclear power plant. The most abundant larvae are shorthorn sculpin larvae ( last 10 years but not during the entire sampling period, since 1981. The second most abundant larvae are European flounder ( gunnel ( Isaacs-Kidd midwater-trawl is used. This sampling is mainly focused on glass eels ( anguilla the 1980´s. This decline is mostly due to a general decrease in recruitment over larger regions and not to the local effect caused by the nuclear power plant. The effects of the cooling-water released into the sea are monitored by fykenet surveys in the recipient (Ringhals) as well as in a reference area (Vendelsö) in two seasons (April and August). The diversity of the fish community has developed differently in the two areas during the cold season, as Ringhals show a decrease in diversity and Vendelsö is stable. This is possibly an effect of the warm water emissions from the power plant. Species that prefer warm water have been observed to concentrate in the recipient area. Eel ( corkwing wrasse ( which show either stable or increasing catches in the area. Species that prefer cold water, such as shorthorn sculpin ( were less abundant in the recipient area. The European flounder showed an increasing trend in both Ringhals and Vendelsö. To investigate the presence of marine alien invasive species a scuba diving survey was conducted in five shallow areas in a gradient from the outlet of cooling water. Three species were found, Japanese oyster (Myoxocephalus scorpius) and its abundance has increased during thePlatichtys flesus). The third most abundant larvae, rockPholis gunnellus) has a decreasing trend since 1979. To sample juvenile fish a modifiedAnguilla). The abundance of glass eels has declined strongly since the beginning ofAnguilla anguilla),Symphodus melops) and shore crabs (Carcinus maenas) are three examples,Myoxocephalus scorpius) and eelpout (Zoarches viviparous)(Platichthys flesus)Crassostrea gigas), one species of red algae Dasya baillouviana and one brown algae, Japanese wireweed ( already established on the Swedish west coast. In the industrial area, a dive survey in one of the outlet ponds and one inspection of the cooling tunnel was conducted. Japanese oyster was found in both places. During the fyke net test fishing in April, one new invasive crab species was found, the Asian shore crab (Sargassum muticum). All these species areHemigrapsus sanguineus).