Open access publications in the SLU publication database

The use of cooling water at the 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 contribute
to alien invasive species establishing in the coastal area.
Reactors R1, R2 and R4 at Ringhals nuclear power plant produced electricity
during the major part of the year 2013, with exceptions for the annual audits and
shorter stops in production. Reactor R3 had a longer revision during the summer.
Fish eggs and fish larvae are sampled in the incoming cooling water using a modified
Bongo net to monitor losses of eggs and larvae in the nuclear power plant. The
abundance of shorthorn sculpin larvae (Myoxocephalus scorpius) has decreased
since the sampling period started, although it is still the most abundant larvae. In
2013 more shorthorn sculpin larvae were caught than ever before in this survey.
The abundance of rock gunnel larvae (Pholis gunnellus) had increased between
2012 and 2013. To sample juvenile fish a modified Isaacs-Kidd midwater-trawl is
used. This sampling is mainly focused on glass eels (Anguilla anguilla). The abundance
of glass eels has declined strongly since the beginning of the 1980's. The decline of
the glass eel abundance is most probably due to a general decrease in recruitment
and not to a 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 as well as in a reference area. These areas are compared in two
seasons to reveal effects of the cooling water emissions. The diversity of the fish
community has developed differently in the two areas during the cold season, where
the recipient showed a decrease in diversity and the reference area was stable. This
Aqua reports 2014:2
Aqua reports 2014:2
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 and
shore crabs (Carcinus maenas) are two examples, which show either stable or increasing
catches in the area. Species that prefer cold water, such as shorthorn sculpin
(Myoxocephalus scorpius) and eelpout (Zoarches viviparous), were less abundant
in the recipient area.
To investigate the presence of marine alien invasive species a scuba diving survey
is conducted in five shallow areas in a gradient from the outlet of cooling water. No
new species were found in the 2013 survey, but three species already established on
the Swedish west coast were found. The species found were the japanese oyster
(Crassostrea gigas), one species of red algae Dasya baillouviana and one brown
algae, japanese wireweed (Sargassum muticum).