Phytoplankton dynamics shaping the efficiency of phosphorus accumulation by periphyton in the eutrophic reservoir

Abstract

Significant demographic and industrial expansion led to the increasing demand for the continuous supply of safe and high-quality water. Much effort is put to resist the effects of extensive eutrophication in reservoirs caused by excessive phosphorus enrichment responsible for cyanobacterial blooms associated with ecosystem degradation and adverse health effects. The potential of an environmental-friendly biological method for phosphorus removal by periphyton developed on the transparent polyacrylic substrates was estimated in eutrophic reservoir for water supply. Weekly, monthly, and continuously (two-, three- and four-month) grown periphyton was sampled from June to October. Qualitative and quantitative analyses of phytoplankton sampled at the same time as periphyton were done. Orthophosphate and total phosphorus concentrations were measured in the water column during the experimental time. Total phosphorus (TP) content in periphyton was estimated spectrophotometrically by the stannous chloride method. It was found that three maximal phosphorus assimilations of 1695, 2897, and 6058 mg TP/m2 ePOSTER340 341 were achieved in one-, two-, and four-month grown periphyton, respectively, each harvested in October. The results of the study indicate that the competition between phytoplankton and periphyton communities was a key factor affecting the periphyton efficiency in phosphorus accumulation. Phytoplankton occurred to be competitively dominant over periphyton in phosphorus assimilation from the water column allowing periphyton to increase phosphorus accumulation only during the periods of very low phytoplankton abundance. If this method is potentially large-scale employed during the remediation process, the harvesting of substrates exposed during scarce phytoplankton biomass would be most effective.