Abstract
As a part of studies on the effect of the warm water effluent from nuclear power plant on marine organisms, the distribution of acorn barnacles which are representative fouling organisms in Uchiura Bay in relation to the effluent from Takahama Nuclear Power Plant was investigated during the one-year period beginning with late May 1978.
The experiments were carried out at three fixed stations in the bay: black celluloid plates (25×18.5cm) and poly vininyl chloride plates of the same colour and size were suspended at 1, 3 and 7 meters depth for 1 or 2 months (Fig. 1), and the species and number of barnacles settled on each plate were checked every month, together with hydrographic observations. As the results, more than five species of barnacles were identified. The most dominant species at each station was Balanus trigonus, followed by B. eburneus and B. improvisus. The latter two were regarded as recent invaders into this locality from foreign countries by cargo boats.
The three species cited above were often most abundant at station 1 located about 500 meters apart from the end of the discharge canal (Figs. 6-11). The water temperature at the station was usually 3°C or more higher than under the natural condition, especially in the layers less than 5 meters in depth (Figs. 2 and 3).
Therefore, it may be suggested from the results that the warm water effluent offers suitable condition for the settlement and breeding of these dominant barnacles.
