Assimilation and dissimilation measurements on plankton of Helgoland waters

Abstract

1. Data obtained in field observations and laboratory experiments on phytoplankton production as well as on factors important for population dynamics in waters near Helgoland have been reported. All pertinent work was carried out between June 1965 and August 1966. 2. In winter, the rate of assimilation is strongly reduced by vertical circulation, low incoming radiation, and high seston content in the water. Between March and November, mass developments of several species have been recorded. 3. The high mean ratio between assimilation and standing stock of phytoplankton (4.5 : 1, in carbon units) indicates a good nutrient supply. Accordingly, gross primary production in Helgoland waters is estimated to be about 500 g C/m2 year. © 1967 Biologischen Anstalt Helgoland.