Changes in summer diatom composition and water quality in urban lakes within a metropolitan area in central China

Urbanization is altering water quality and biotic communities of lake ecosystems worldwide, especially in developing regions. In this study, the diatom community structure and water quality of the epilimnion were analyzed in 38 lakes (40 sampling sites) in Wuhan City (central China) to assess the impacts of urbanization on lake ecosystems. Diatom communities displayed clear variation along the urban-to-rural gradient, with blooms of eutrophic species found in urban lakes in contrast to higher abundances of mesotrophic or oligotrophic taxa in rural lakes. Redundancy analyses revealed that the diatom community recognition to species, genus, and ecological guild level were all significantly correlated with Chl a, Si, and secchi depth, indicating that the changes in diatom communities were mainly explained by differences in nutrient concentrations and light condition. Considering the rapid urbanization and population expansion, it is important to carry out effective measures for the protection of these lake ecosystems, especially by reducing sewage discharge. The high consistency found between diatom community classification and water quality status highlights the applicability of diatoms for bioindication of shallow urban lakes, especially in rapidly developing cities. Even the taxonomic determination at the level of genera or ecological guilds can enable rapid water-quality assessment.