[Influence and Driving of Environmental Heterogeneity on the Epilithic Diatom Community in Xiangxi River, a Tributary of the Three Gorges Reservoir Area].

Environmental heterogeneity can not only increase species diversity to some extent but also affect the stability of terrestrial communities. However, how environmental heterogeneity affects species diversity of epilithic diatom communities in aquatic ecosystems is rarely reported. In this study, therefore, epilithic diatoms and their roles in driving species diversity were explored by quantifying and comparing the environmental heterogeneity in Xiangxi River, a tributary of the Three Gorges Reservoir Area (TGR), on a time scale. The results showed that environmental heterogeneity, taxonomic -diversity, and functional -diversity in non-impoundment periods were significantly higher than those in impoundment periods. Moreover, the turnover components in the two hydrological periods showed the highest contribution to -diversity. However, the taxonomic -diversity in impoundment periods was significantly higher than that in non-impoundment periods. In addition, functional richness in functional -diversity was significantly higher in non-impoundment periods than that in impoundment periods, whereas there was no significant difference in other functional -diversity, i.e., functional dispersion and functional evenness, found between the two periods. Multiple regression on (dis)similarity matrices (MRM) analysis indicated that ammonium nitrogen (NH-N) and silicate (SiO-Si) were the key environmental heterogeneous factors affecting the epilithic diatom community in Xiangxi River during the non-impoundment periods, whereas the key heterogeneous factors were ammonium nitrogen (NH-N), silicate (SiO-Si), and total phosphorus (TP) during the impoundment periods. These results suggested that the environmental heterogeneity during different hydrological periods in TGR can significantly affect the community structure of epilithic diatoms, resulting in the differentiation of species within the community and even affecting the stability of aquatic ecosystems.