Eutrophication and the Ecosystem -- Daphnid Grazing Ecology -- Toxic Reduction of Daphnid Grazing Effectiveness -- Field Observations of Daphnid Grazing -- New Perspectives for Eutrophication Management. Eutrophication of surface waters is generally recognised as a matter for envir- mental concern. Eutrophication is characterised by increased algal growth, with an increased incidence of toxic cyanobacteria blooms and a decrease in the ab- dance of species. Some of the manifest problems brought about by prolific algal biomass include: turbid waters; anoxic conditions; bad smell and chironomid and Culex midge plagues (Vollenweider 1990; Moss et al. 1996a; Carpenter et al. 1998). Such - trophication problems ("eutrophication" sensu lato) are generally considered to be the consequence of enhanced nutrient loadings ("eutrophication" sensu stricto) (Likens 1972; Vollenweider 1990; Reynolds 1992; Moss et al. 1996a; Carpenter et al. 1998). Therefore, the management of eutrophicated water bodies is usually primarily focused on the reduction of nutrient loading, supported by a policy of reduced environmental releases of phosphorus from laundry detergents, sewage and agriculture. However, it became apparent over the past decade, that reduced grazing of - gae by daphnids can be a crucial factor determining whether or not nutrient - richment will lead to eutrophication problems (Moss et al. 1991; Moss et al. 1996b; Reynolds 1994). Biomanipulation of eutrophicated shallow water bodies, thereby improving ecological conditions for daphnids, became a regular tool - plied in eutrophication management practice (Benndorf 1990; McQueen 1998; Harper et al. 1999). Biomanipulation is mainly focussed on the improvement of biological con- tions leading to a higher survival rate for daphnids as part of the aquatic foodweb.