Dynamic Characteristics of Periphytic Algae Communities on Different Substrates and the Host Response in Subtropical-Urban-Landscape Lakes

Outbreaks of periphytic algae, including filamentous algae, have been observed after submerged macrophyte restoration and are common in early stages. Dynamic changes in the periphytic algae community on Vallisneria natans and artificial V. natans were investigated in situ, and their characteristics were compared on the two substrates. The results showed that more periphytic algae species occurred on V. natans (77 taxa) than on artificial V. natans (66 taxa) (F = 2.089, p = 0.047). The cell density and chlorophyll a (Chl. a) content of periphytic algae were 3.42-202.62-fold and 2.07-15.50-fold higher on the artificial substrate than on V. natans, respectively. Except for Lyngbya perelagans (i.e., the only common dominant periphytic algae species on the two substrates), the dominant species on V. natans were Cocconeis placentula and Ulothrix tenerrima, while those on the artificial substrate were Stigeoclonium aestrivale, Oscillatoria tenuis and Achnanthes minutissima. The cell density of periphytic algae was significantly affected by the total phosphorus (TP) and NO3--N and electric conductivity on V. natans, and by TP and NH4+-N on artificial V. natans. The malondialdehyde content of V. natans was significantly correlated with the periphytic algae biomass. V. natans was more affected by periphytic algae during its slow-growing period, and the contribution order of stress to V. natans was diatoms > cyanobacteria > green algae. Our findings might contribute to the understanding the effect of substrate specificity on periphytic algae communities, and have important implications for the restoration of submerged plants in eutrophic lakes.