Impact of Brazilian fish species at early developmental stages on plankton communities and water chemical parameters

摘要

Effect of larvae of Astyanax altiparanae (AA), Piaractus mesopotamicus (PM), Leporinus obtusidens (LO) and Prochilodus lineatus (PL) on plankton communities and wa ter quality were evaluated. Twenty 500 L tanks were used into a completely randomized de sign with five treatments and four replications, containing 350 individuals of each species per tank. One treatment cont rol had no larvae (CT). Every six days, were collected periphyton an d water to determine the concentr ations of chlorophyll and total phosphorus. Plankton samples (20 μ m mesh net) were taken every thr ee days. Fish affected plankton communities, which showed lower densities of total zooplankton in AA tanks than in LO tanks. Increased density of rotifers and reduced density of copepods were found in AA, PM and PL tanks in relation to the CT. Higher density of testate amoebae was observed in AA, PM and LO tanks. As to biovolume, higher values for total plankton were registered in the CT and LO tanks compared with AA, PM and PL tanks; higher values for rotifers were obse rved in PL tanks than in the CT. Copepod biovolume was higher in CT and LO tanks. Biovolume of cladoceran and testate amoebae were not affected. Plankton ?s chlorophyll concentration was higher in tanks wi th fish. Higher concentrations of dissolved oxygen were found in AA and PM tanks. It can be concluded that juveniles of these fish species differently affect the plankton community and chemical parameters of the water.