Diatom Taxonomic Composition as a Biological Indicator of the Ecological Health and Status of a River Basin under Agricultural Influence

The Lalin River Basin (LLRB) is a major drainage basin in northeastern China, that has been significantly influenced by agricultural activities. This study focused on exploring diatom taxonomic composition linked to environmental factors at the taxonomic levels of genus and species during ice-covered periods. Nine sampling stations were divided into three groups based on trophic state index (TSI). hierarchical cluster analysis (HCA) and redundancy analysis (RDA) were performed to identify diatom distribution patterns and their relationships to environmental factors. Diatom richness, composition and distribution were analyzed at the levels of genus and species. Our results showed the epipelagic diatomMelosira varianswas very abundant at most stations. Benthic diatomsAchnanthidium minutissimum,Encyonema minutumandGomphonema parvulumwere dominant in group-3, which had the highest trophic states. HCA showed the similarity of diatom taxonomic composition spatial distribution patterns between genus and species levels. RDA revealed that the key factors related to genus level distributions are COD, TP and EC, while TP was the key factor in structuring diatom taxonomic composition at the level of species. These results suggest identification of diatoms at genus level can be used as a potential indicator to assess ecological health status of agricultural-influenced rivers during ice cover periods. Further research is necessary to explore the utility of genus level diatom composition as a biological indicator in rivers.