Abstract
In situ primary production, chlorophyll a and the quantitative and semiqualitative composition of phytoplankton were studied from March to Nov. in 2 basins in a Norwegian land-locked fjord, which receives sewage effluent from 400 individual facilities. The seasonal production was 60-70 mg C/m2, and the annual production was estimated at 90-100 mg C/m2. The occurrence of phytoplankton was similar to what was reported from unpolluted Norwegian waters and the chlorophyll a concentrations were small after the spring bloom. Average assimilation numbers were 5.3 and 5.5. The highest assimilation numbers, 13.9 and 18.0, occurred in July, at the time of the smallest biomass. No correlation was found with temperature, light, or nutrients and a correlation with the phytoplankton composition is suggested. The 2 basins were in most respects alike, and it is concluded that the effects of the sewage effluent on primary production was negligible.