Effects of Nitrogen Pollution on Periphyton Distribution, Elemental Composition and Assemblage Shifts in River Ecosystems

摘要

Ecological stoichiometry (ES) can provide a good insight and predictive power for environmental research. For some years, it has been suggested that ES should be used in river ecosystem studies. This study applied this method to a river system of Hai River Basin (HRB), to identify which pollutants affect periphyton distribution and how pollutants affect periphyton stoichiometry. In rivers with different levels of nitrogen (N) pollution, periphyton could be classified into three groups based on typologies as follows: attached diatoms (AD), filamentous algae (FA), and filamentous algae with epiphyte (FE). AD represented clean ambient water, FE indicated slight pollution, and FA showed that water had been contaminated by N. Ammonium nitrogen (NH4+-N) was the main factor of periphyton distribution and assemblage shifts. The carbon/N ratio differed significantly between the groups, and values were 14 for AD, 12 for FE, and ten for FA. The N/phosphorus (P) ratios for AD, FE, and FA were 47, 24, and 19, respectively. NH4+-N and total P (TP) controlled the N/P ratio of AD, NOx--N (nitrite and nitrate-nitrogen) controlled the N/P ratio of FE and TP controlled the N/P ratio of FA. Based on the changes observed in periphyton assemblages in the HRB, managing and controlling N pollution in freshwater, especially from NH4+-N, should be prioritized.