Variations in Plankton Community Structure Between Freshwater and Saline-Alkaline Waters and Their Correlation with...

Essential amino acids and unsaturated fatty acids are key nutritional indicators. The human body preferentially absorbs these compounds, which have beneficial effects on health. In aquatic ecosystems, plankton communities serve as the primary food source for aquatic organisms, playing a crucial role in shaping their nutritional composition. In this study, we collected populations of Macrobrachium nipponense and corresponding water samples from ten distinct geographical locations across China. These sites included five freshwater resources and five saline-alkaline water resources. This study measured the ionic composition and plankton community structure of water samples, and analyzed the nutritional components of M. nipponense, aiming to identify indicator taxa linked to the nutritional value in this species. The results show significant differences in both nutritional components and plankton community structures between freshwater and saline-alkaline environments. This suggests a correlation between specific plankton taxa and the nutritional value of M. nipponense. Using relative sequence abundance data from metabarcoding, linear discriminant analysis effect size (LEfSe) analysis identified six plankton indicator taxa at the genus level. Their abundance differed significantly between the two habitat types. The saline-alkaline region had three associated taxa: Cyclotella, Brachionus, and Chaetoceros. In contrast, Arctodiaptomus, Cryptomonas, and Limnoithona were identified as indicator taxa for freshwater regions. Redundancy analysis (RDA) and Pearson correlation analysis revealed that, with the exception of the SY site, the abundance of Chaetoceros and Brachionus in saline-alkaline waters tracked with levels of K⁺, Ca²⁺, and HCO₃^-. Meanwhile, at the SZ site, plankton community richness rose with CO₃^2-. Furthermore, the potential correlations between plankton indicator taxa and the formation of specific nutritional components in M. nipponense were explored. These findings highlight the complex interactions among ionic composition, plankton indicator taxa, and nutritional value in M. nipponense. Ultimately, this study can support the development of artificial techniques to regulate the nutritional components of this commercially important species.