What is the influence on water quality in temperate eutrophic lakes of a reduction of planktivorous and benthivorous fish? A systematic review protocol
1 Mistra Council for Evidence-Based Environmental Management, Royal Swedish Academy of Sciences, SE-104 05 Stockholm, Sweden
2 University of Wisconsin Center for Limnology, 680 North Park Street, Madison, WI 53706-1492, USA
3 Department of Aquatic Resources, Swedish University of Agricultural Sciences, Skolgatan 6, Öregrund, SE-742 42, Sweden
4 School of Natural Sciences, Linnaeus University, Kalmar, SE-391 82, Sweden
5 Department of Ecology and Environmental Science, Umeå University, Umeå, SE-901 87, Sweden
6 DTU Aqua, National Institute of Aquatic Resources, Technical University of Denmark, Vejlsøvej 39, Silkeborg, DK-8600, Denmark
7 Department of Aquatic Ecology, Netherlands Institute of Ecology, P.O. Box 50, AB Wageningen, 6700, The Netherlands
Environmental Evidence 2013, 2:9 doi:10.1186/2047-2382-2-9Published: 10 May 2013
In lakes that have become eutrophic due to sewage discharges or nutrient runoff from land, problems such as algal blooms and oxygen deficiency often persist even when nutrient supplies have been reduced. One reason is that phosphorus stored in the sediments can exchange with the water. There are indications that the high abundance of phytoplankton, turbid water and lack of submerged vegetation seen in many eutrophic lakes may represent a semi-stable state. For that reason, a shift back to more natural clear-water conditions could be difficult to achieve.
In some cases, though, temporary mitigation of eutrophication-related problems has been accomplished through biomanipulation: stocks of zooplanktivorous fish have been reduced by intensive fishing, leading to increased populations of phytoplankton-feeding zooplankton. Moreover, reduction of benthivorous fish may result in lower phosphorus fluxes from the sediments. An alternative to reducing the dominance of planktivores and benthivores by fishing is to stock lakes with piscivorous fish. These two approaches have often been used in combination.
The implementation of the EU Water Framework Directive has recently led to more stringent demands for measures against eutrophication, and a systematic review could clarify whether biomanipulation is efficient as a measure of that kind.
The review will examine primary field studies of how large-scale biomanipulation has affected water quality and community structure in eutrophic lakes or reservoirs in temperate regions. Such studies can be based on comparison between conditions before and after manipulation, on comparison between treated and non-treated water bodies, or both. Relevant outcomes include Secchi depth, concentrations of oxygen, nutrients, suspended solids and chlorophyll, abundance and composition of phytoplankton, zooplankton and fish, and coverage of submerged macrophytes.