Studies On The Filter-feeding Pressure Of Perna Viridis To Phytoplankton

The filtration rhythIn of Perna viridis (L.) was examined and effects of lightintensity temperature, salinity, algal cell density, algal cell size and bivalve bodysize on the filtration rates of Perna viridis to phytoplankton were studied underlaboratory conditions.The filtration rates of Perna viridis had no significant differences througholltthe diamal period at the natural light intensity of 0~570lx, as well as at the lightintensity of 0~l0000lx. While temperature, salinity, algal cell density, algal cellsize and bivalve body size affected filtration rates significanly. Results alsoshowed that filtration rates were concurrently affected by temperature andsalinity. They increased with temperature and so did with salinity at fixed salinityor temperature, especially at low salinity of l6 and at low temperature of 16c.There were marked interactions between temperature and algal cell density andbetween temperature and bivalve body size. The filtration rates of Perna viridisincreased with the increase of algal cell density and the decrease of bivalve bodysize, especially at high temperature. Temperature also affected filtration ratessignificanly at high algal cell density and small bivalve body size. Under thesame conceIltration of algal cells, filtration rates showed significant differencesbetween various algal species due to the differences of cell sizes. Howeverfiltration were positively related to algal density at the same conceniration of theorganic materials.Results of our experiment suggest that Perna viridis could adaPt to wideenvironmelltal conditions and have high filtration rates to phytoplankon in thecoastal waters of Guangdong province through year round. It seems feasible touse Perna viridis to reduce the biomass of phytoplankton in subtropic coasts, andthus, control the eutfophication of coastal waters and improve water quality.