Periphyton response to nitrogen and phosphorus enrichment in a eutrophic shallow aquatic ecosystem

We examined changes in biomass and species dominance of periphyton in response to nitrogen (N) and phosphorus (P) enrichment in 12 mesocosms representing eutrophic aquatic ecosystems. The 100-L mesocosms consisted of lake water and pond sediment, and N and P were applied weekly. Periphyton samples were taken to assess the biomass (as estimated by the concentration of chlorophyll a (chl a)) and to determine which species were dominant. The mean periphyton biomass (chl a) in the P-enriched treatment did not differ from that in the control group, but increased with N enrichment. Compared with that in the control group, the chl a concentration increased with N+P enrichment in the early stages of the experiment, but decreased in the later stages. The decline in periphyton biomass at the later stages of the experiment was due to limited light availability, which resulted from the increased phytoplankton density in the experiment. The nutrient enrichment treatments resulted in changes in the dominant algal species in the periphyton, suggesting that various algal species showed different responses to different nutrients. The results of this study have implications for nutrient management in aquatic ecosystems.