Abstract
The primary production of different size fractions of plankton from six stations in Oslofjorden, Norway, was studied by means of laboratory and in situ incubations. Ultraplankton (passing 5 μm nylon gauze) contributed 15–89 %, while nanoplankton in all (passing 45 μm nylon gauze) contributed 50–100 % to the total primary production. The in situ measurements (production per unit water surface) varied by a factor of 100 through the year in the outer part, 300 in the inner part of the fjord. In the inner part the highest recorded primary production values were five times greater than in the outer part. In summer daily production was 2.8 g G/m2 in the inner fjord and 0.6 g C/m2 in the outer part.
