Effects of filter-feeding bivalves in benthic and pelagic habitats on plankton community and water quality in shallow systems: implications for lake rehabilitation

Abstract

Filter-feeding bivalves have strong effects on ecosystem processes and functions. Bivalves may be used for the rehabilitation of eutrophic waters, either by being placed suspended in cages or on chains in pelagic habitats or stocked in benthic habitats. However, the effects of bivalves on the ecosystem may differ between the two habitats. A 5-week mesocosm experiment with bivalves (Sinanodonta woodiana Lea 1834) was conducted to test if filter-feeding bivalves suspended in pelagic habitats would improve water quality more efficiently than stocked bivalves in benthic habitats. Nutrients, suspended solids, light intensity, biomass of phytoplankton in different size fractions, and zooplankton were measured. Bivalves reduced the biomasses of total phytoplankton and nanophytoplankton and decreased the total phosphorus, total suspended solids, and organic suspended solids in both the benthic and the pelagic habitats. Bivalves also increased the light intensity and the biomass of periphyton and benthic algae. However, we found significantly higher ammonium nitrogen concentrations and higher periphyton biomass in the suspended bivalve treatment than in the benthic bivalve treatment. In both habitats, bivalve introduction reduced the abundance of cladocerans, increased the abundance of copepods but had no effect on the abundance of rotifers. The abundances of total zooplankton, cladocerans, copepods, and rotifers were similar in the treatments with suspended and benthic bivalves. These results confirm the strong effect of filter-feeding bivalves on plankton communities and their potential for the improvement of water quality whether suspended or occurring in the sediment, they indicate a potential of using filter-feeding bivalves in lake rehabilitation.