Effects Of Filter-feeding Bivalves On Plankton Community And Water Quality

Filter-feeding bivalve is important component of aquatic ecosystem,which can filter on plankton and affect water quality.How does the animal affect plankton community to improve water quality?Mesocosm experiments?control,mussel treatment?were conducted to investigate the effect of Cristaria plicata on plankton community and water quality.Nutrient release by the animals was also conducted in aquarium.Results showed that:the biomass?measured as chlorophyll a?of nanoplankton?2?20?m?and picoplankton?<2?m?in the bivalve group were reduced significantly by 65%and 68%,respectively,compared with those in the control group.The proportion of microplankton?>20?m?in total plankton biomass from 28%in the control group increased to 68%in the mussel treatment.C.plicata decreased the total abundance of zooplankton and the abundance of rotifer by 81%and 87%,respectively,but the proportion of Cladocera in zooplankton increased?10 times.The mussel reduced the water TN and TSS concentrations and the phytoplankton biomass?chl a?,increased the water transparency,improved light conditions on sediment surface and enhanced the benthic algae growth.However,no significantly change of temperature?T?,pH,dissolve oxygen?DO?,conductivity?SPC?and total phosphorus?TP?was found between the treatments.Nutrients release of C.plicata increased the TN,TDN,NH₄⁺-N,TP and SRP concentrations in the aquarium experiment.Thus,the C.plicata can change the abundance and community structure of plankton by filtering on nanoplankton,picoplankton and rotifers.Though C.plicata can release nutrients to water,the animal can decrease TN and TP concentrations by filtration and biological deposition,reduce suspended particles,increase transparency and enhance the benthic algae growth,thereby improving the water quality.