The influences of nitrogen and phosphorus availability on periphytic algae in eutrophic experimental mesocosm

ABSTRACT To investigate the influence of nitrogen (N) and phosphorus (P) availability on the periphytic algal biomass and assemblage composition (by pigment analysis) in the eutrophic lake, natural littoral intact sediment cores in a subtropical eutrophic lake (Lake Taihu) were collected, and subjected to three levels of water N and P loading (N-P [mg. L−1]: 1.5, 0.075; 2.5, 0.125; 3.5, 0.175) in the tanks, eighteen artificial substances (glass slides) were fixed at three water depths (1, 17, and 33 cm above the surface sediment) for development of periphytic algae in each tank, respectively. The results showed that the biomass of periphytic algae on artificial substance was significantly enhanced with increasing N and P levels in water column and water depth (p < 0.05), while sediment-associated periphytic algae did not significantly increase with increasing N and P levels in water column. The development of sediment-associated periphytic algae changed the phosphorus form, calcium-bound phosphorus and inorganic phosphorus in the sediments decreased slightly, and the total phosphorus and organic phosphorus in the sediments increased. Our results suggest that N and P availability is conducive to the development of periphytic algae in subtropical eutrophic shallow lakes in spring.