Phyto-Zooplankton Community in Coastal Waters of Western Sweden — An Ecosystem Off Balance?

A baseline study of the phyto- und zooplankton community was carried out from 1978 to 1981 in, what was supposed to be, a relatively undisturbed fjord on the west coast of Sweden. Heavy phytoplankton blooms were found during spring and autumn. Chlorophyll a and cell numbers were far above normal. Extremely low zooplankton biomass during the spring bloom and high abundance of scyphomedusae (which preyed on zooplankton during the summer) resulted in low grazing pressure and probably led to increased sedimentation of organic matter. Oxygen deficit has occurred in bottom waters of the fjord in the absence of adequate exchange. It was not possible to determine whether this series of events is due to natural fluctuations or man-made influences.