The response of benthic diatom community to anthropogenic eutrophication of a river basin under agricultural influence in NE China

Abstract Anthropogenic eutrophication has universally threatened river ecological health and has been a key issue in river conservation. Agricultural sewage, which leads to increased nutrient levels and results in the loss of ecological function and biodiversity, results from the growth of agricultural activity and human populations. Consequently, attention has increasingly been focused on developing a relevant tool to describe the relationship between the biotic communities and anthropogenic eutrophication. The benthic diatom community has been widely used as an effective tool for indicating the ecological status of river systems especially in the context of recent international Water Framework Directive policies (WFD). In this study, a statistical method consisting of trophic status index (TSI), Specific Polluosensitivity Index (IPS), Descy Index (DES), redundancy analysis (RDA), and the geographic information system (GIS) technique was conducted to explore the response of benthic diatom community to anthropogenic eutrophication. Initially, the TSI, IPS and DES were determined to differentiate the trophic gradient along a gradient in agricultural intensity. Subsequently, RDA was used to identify spatial distribution patterns of environmental parameters and benthic diatom communities. Finally, the RDA scores as calculated and spatially interpolated were applied to GIS technology to reveal the response of benthic diatom communities to anthropogenic impacts along the trophic gradient. Our results revealed that the studied basin mostly exceeded the eutrophic level. Two different patterns of diatom communities response to ecological gradient were identified based on RDA, one representing the agriculture eutrophication discharges in electrical conductivity (EC) and the other representing organic pollution as chemical oxygen demand (COD). The developed method in this study highlight that the EC was more effective than the nutrient indices in determining diatom distribution in a eutrophic agriculturally-influenced river system.