To analyze the structural characteristics of zooplankton functional groups (ZFGs) and their correlation with environmental physicochemical factors in the Chaohu Lake Basin, water samples were collected from October 2019 to July 2020, and the zooplankton species and ZFGs were investigated. A total of 250 species, including 88 protozoa, 115 rotifers, 28 cladocerans, and 19 copepod species, were detected and divided into 16 ZFGs. The ZFGs exhibited obvious spatiotemporal heterogeneity. ZFGs in the Chaohu Lake were notably different from those in rivers and were different between the rivers. In the ecosystem, network analysis showed that protozoan algae/protozoan bacteria (PA/PB), rotifer particle filter (RF), and rotifer small predator (RSG) were important in the spring, summer, and autumn that and small zooplankton filter (SCF) was important in spring, autumn, and winter, while the importance of other ZFGs changed with seasons. Redundancy analysis showed that the environmental factors with a strong correlation between the ZFG compositions differed in each season. Different ZFGs exhibited different correlations with environmental factors. This study showed that ZFGs were closely related to environmental factors and that functional traits can reflect responses to changes in the water environment.

Fish gut microbiota were potentially influenced by habitat changes. However, the fish gut has been shown to have a filtering effect on habitat microorganisms. Here, we hypothesized that the filtering of fish gut microbiota could counteract the effect of dam construction on the gut microbiota composition. To test this hypothesis, we collected water and Rhinogobio cylindricus individuals from four sampling sites located upstream of the Three Gorges Dam (TGD) and analyzed the microbiota composition in the water samples (n = 48) and R. cylindricus gut samples (n = 89) by high-throughput sequencing of the 16S rRNA gene. A total of 6,772,720 (49,435.91 ± 3762.80) high-quality sequences were obtained from 137 samples. The microbiota in the water environment was significantly more diverse than that in the gut of R. cylindricus. The β-diversity of microbiota in the water was significantly lower than that in the gut of R. cylindricus. The water microbiota composition varied greatly according to the distribution of the sampling sites upstream of the TGD, but the gut microbiota of R. cylindricus did not show the same pattern. Rather, the gut microbiota of R. cylindricus were not significantly affected by the TGD. This consistency in the internal tract of R. cylindricus is presumedly a result of a filtering effect on the water microorganisms. Our study furthers our understanding of the stabilization mechanism of the gut microbiota composition of fish and the impact of dams on river ecosystems.

In the present study, the biological effect of TiO2 nanoparticles on cyanobacteria cells was studied using Microcystis aeruginosa (M. aeruginosa) as a model. Nano-TiO2 as a photo-catalysts agent used for water treatment may pose a risk to ecosystems, especially for the water organisms such as cyanobacteria. Scanning electron microscope (SEM) images provided that with the increasing of photocatalytic time, slime layer on the cell surface was damaged and sunk. Attenuated total reflectance fourier transform infrared (ATR-FTIR) spectroscopy revealed that the vibration peaks of C-C, C-H, C=O, P=O weakened within 12 h. According to the dynamic analysis of the infrared peaks, the damage on the cell groups under nano-TiO2 photocatalysis with different time periods was analyzed. The concentrations of K(+), Ca(2+), Mg(2+) released from the cells were measured, which indicated that nano-TiO2 photocatalysis have changed the cell membrane permeability and fluidity of M. aeruginosa.