Seasonal eutrophication by wildfowl in basins isolating from the sea

Abstract

A new and very special course of events starts in a freshwater basin, just isolated from the sea. In NW Europe this is mainly caused by land uplift in Holocene times or by regression of the sea. It has been thoroughly documented by the gradual change in the composition of the fossil diatom floras. Attention is drawn to the possible impact of migrating birds, especially wildfowl, breeding, resting and moulting in those often shallow, sheltered lakes along the Scandinavian coastlines. The gregarious wildfowl species might seasonally increase the allochthonous input of nutrients in the lake ecosystems and cause marked changes in biotic interactions. A working hypothesis is suggested, that the wildfowl species in question were appreciably more numerous before the arrival of man. Consequently, their effect on seasonal eutrophication cannot be neglected in the paleolimnological context.