Response of Colonization and Community Succession of Epiphytic Algae on Potamogeton Crispus L.to Ammonia Loads

To better understand colonization process and community succession of epiphytic algae during the water eutrophication,a static incubation experiment and macroscopic counting method were used to investigate the effects of increasing ammonia loads on epiphytic algae attaching to common submerged macrophyte Potamogeton Crispus L.of Taihu.The results showed that colonization process and community composition of epiphytic algae varied with ammonia levels.The climax succession showed that Bacillariophyta was dominated at low ammonia concentrations and Chlorophyta prevalent at high ammonia concentrations in epiphytic algae assembly.In addition,some dominant species of epiphytic algae only appeared in specific ammonia concentrations.For example,Closterium of Chlorophyta appeared as dominant species only at ammonia concentrations of 1.5 mg·L-1and 5.0 mg·L-1,while Synedra of Bacillariophyta appeared only at ammonia concentration of 2.5 mg·L-1.The epiphytic algae biomass also showed variation with ammonia loads.When ammonia concentrations were lower(≤1.5 mg·L-1),epiphytic algae biomass increased with increasing ammonia concentrations,but was inhibited when the concentrations were higher(≥5 mg·L-1).The maximum biomass and highest species richness of epiphytic algae were observed at the medium ammonia concentration( 2.5 mg·L-1,group C).The results indicate that ammonia concentrations have significant effects on the community colonization and succession of epiphytic algae and epiphytic algae may cause the decline of submerged macrophyte.