Long-term effects of nutrient changes on rotifer communities in a subtropical lake

Abstract

External nutrient loading has a major influence on the abundance, composition and diversity of zooplankton communities. To clarify how the reduction of nutrient loading during lake restoration interacts with other abiotic and biotic factors and how the interactive factors affect long-term changes in rotifer communities, we analyzed the relationships between the rotifer communities and environmental factors using a 17-year dataset. After the reduction of nutrients, both the abundance and biomass of rotifers declined, and the dominant rotifers changed from eutrophic-tolerant species to less tolerant ones. The lower TN:TP ratio that was caused by the imbalanced decrease in TN and TP after restoration promoted cyanobacteria, which negatively related to the resource-use efficiency of rotifers. Moreover, seasonal differences in the Shannon–Wiener index–TN relationships and the decrease in the Pielou index with the increase in water temperature implied there were interactive effects of water temperature and nutrients on species diversity. The study concluded that changes in rotifer abundance and community composition were mainly related to TN, but the changes in species diversity were mainly related to the interactive effects of the TN:TP ratio, water temperature and food quality. Our findings highlighted the effects caused by imbalanced nutrient changes on species diversity.