Is reduction of the benthivorous fish an important cause of high transparency following biomanipulation in shallow lakes? |
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Authors: | Meijer M -L de Haan M W Breukelaar A W Buiteveld H |
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Institution: | (1) Institute for Inland Water Management and Waste Water Treatment, P.O. Box 17, 8200 AA Lelystad, The Netherlands |
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Abstract: | Experimental reduction of the fish stock in two shallow lakes in The Netherlands shows that such a biomanipulation can lead
to a substantial increase in transparency, which is caused not only by a decrease in algal biomass, but also by a decrease
in resuspended sediment and detritus. A model was developed to describe transparency in relation to chlorophyll-a and inorganic, suspended solids (resuspended sediment). With the use of this model it is shown that more than 50% of the
turbidity in these shallow lakes before biomanipulation was determined by the sediment resuspension, mainly caused by benthivorous
fish.
Another analysis reveals that the concentration of inorganic suspended solids and the biomass of benthivorous fish are positively
correlated, and that even in the absence of algae a benthivorous fish biomass of 600 kg ha−1 can reduce the Secchi depth to 0.4 m in shallow lakes. In addition, it is argued that algal biomass is also indirectly reduced
by removal of benthivorous fish. Reduction of benthivorous fish is necessary to get macrophytes and macrophytes seem to be
necessary to keep the algal biomass low in nutrient-rich shallow lakes. It is concluded that the impact of benthivorous fish
on the turbidity can be large, especially in shallow lakes. |
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Keywords: | benthivorous fish biomanipulation resuspension turbidity sediment |
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