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Summary
Zooplankton distribution has been studied in lake Øvre Heimdalsvann, an IBP/PF site in Norway, for the purpose of obtaining reasonably good estimates of standing crop for zooplankton measurements. A calculation method for standing crop estimates is introduced.
In winter, the distribution in vertical direction seems to be related to distance from surface not from bottom. With the mixing currents in summer it is difficult to distinguish between the effect of distance from surface and distance from bottom. In horizontal direction the different species showed various capabilities to act against currents. The effect of the currents seems to be that the distribution becomes more homogeneous. Outlet water brought less animals than mean density in the lake water except for the rotifers Kellicottia longispina (Kellicott) and Polyarthra vulgaris Carlin.
Cyclops scutifer Sars has a one year cycle. During winter, the density in lake water decreases, but just before icebreak there is a rapid increase and the additional animals might possibly have been distributed in the sediment some months.