Three common floating bed plants, Eichhornia crassipes, Pistia stratiotes, and Ipomoea aquatica, were selected in the present study to investigate their inhibitory effects on toxic Microcystis aeruginosa. The results showed that all three types of floating-bed plants could considerably inhibit the growth of M. aeruginosa and effectively remove the microcystins (MCs) from water systems, among which, E. crassipes and P. stratiotes were more effective in resisting M. aeruginosa, and the removal rate of the intracellular MCs could be up to 100%. In addition, the roots and leaves of the three plants were enriched with a large number of MCs and demonstrated significant antioxidant responses, as evidenced by the increase in the content of catalase (CAT), glutathione peroxidase (GSH-PX), superoxide dismutase (SOD), and malondialdehyde (MDA) in the roots, stems, and leaves of the plants. Furthermore, this study also showed that Proteobacteria, Bacteroidota, Myxococcota, Verrucomicrobiota, and Actinobacteriota dominated the root microorganisms of the three plants. Moreover, a variety of MC-degrading bacteria, including Sphingomonas, Acinetobacter, Novosphingobium, and Pseudomonas, were found at the genus level, which further provides important basic data for the regulation of eutrophic water bodies and the removal of MCs.

The growth and photosynthetic responses of microcystin (MC)- and non-MC-producing Microcystis to the submerged macrophyte Myriophyllum spicatum were investigated under plant-Microcystis co-culture conditions (PMC + , PMC−), in comparison with their corresponding mono-culture controls (SMC + , SMC-). The OJIP chlorophyll a fluorescence transient was recorded and analyzed using JIP-test parameters. In comparison with the corresponding mono-culture controls, the quantum efficiencies of the electron transport chain expressed as parameters Ψo and φEo decreased by more than 25% in the PMC− group, much higher than those in the PMC+ group (p < 0.05). The decreasing extent of the electron transport flux ratio ETo/RC was significantly larger in the PMC− group than in the PMC+ group (p < 0.05). The performance index (PIABS) decreased by 26.98% in the PMC− group and by 16.25% in the PMC+ group. These results indicated that the non-MC-producing Microcystis was more sensitive than the MC-producing strain when co-cultured with M. spicatum, and the efficiency and energy flux of electron transport might be the main targets of Photosystem II. Future research should focus on the intraspecific composition and toxigenic levels of Microcystis populations interacting with submerged macrophytes to guide the use of submerged vegetation restoration.

Phytoplankton communities play a crucial role in riverine ecosystems, yet their assembly mechanisms in high-silt environments remain poorly understood. This study investigated seasonal variations in phytoplankton community structure and assembly mechanisms in a riverine environment with high silt loads. Phytoplankton and physicochemical water quality factors were analyzed in the middle and lower reaches of the Yellow River during two seasons: November 2023 (autumn) and April 2024 (spring). A total of 110 algal species from seven phyla were identified, with Chlorophyta being predominant in species richness and Cyanophyta in cell density. Both species richness and abundance were lower in autumn than in spring. The α-diversity analysis revealed that the Pielou’s eveness index was significantly higher in spring compared to autumn. Non-metric multidimensional scaling (NMDS) based on Bray–Curtis distances showed significant seasonal differences in phytoplankton community composition. Furthermore, β-diversity decomposition analysis revealed that turnover was the dominant component in both seasons, but the proportion of nestedness was significantly higher in spring compared to autumn (p < 0.05). Based on the analyses of the dispersal–niche continuum index (DNCI) and the modified stochasticity ratio (MST), this study demonstrates pronounced seasonal variations in the assembly mechanisms governing phytoplankton communities in the middle and lower reaches of the Yellow River. In autumn, stochastic processes, primarily driven by dispersal, accounting for 58.85% of the community assembly. In contrast, deterministic processes, largely shaped by niche selection, contributing 65.05% to the community assembly in spring. The community structure of phytoplankton in this region is shaped by the combined effects of geographical factors, elevation, and environmental variables, with particularly pronounced seasonal variations in environmental drivers—total nitrogen (TN) emerges as the primary factor influencing autumn community assembly, while spring community structure is mainly regulated by silica (SiO₂) and pH. This study deepens the understanding of phytoplankton assembly mechanisms in sediment-rich rivers and provides fundamental data for phytoplankton construction mechanisms and aquatic biodiversity conservation in the middle and lower reaches of the Yellow River.

Cyanobacterial blooms (CYBs) have become a global environmental issue, posing risks to edible bivalves. Toxic cyanobacteria and thermal stress represent the two key co-occurring stressors to bivalves experiencing CYBs. To investigate the combined effects of these stressors on the edible bivalve Corbicula fluminea, the responses to oxidative stress and the molecular mechanisms of physiological adaptations in C. fluminea were examined under co-exposure to toxic Microcystis aeruginosa and thermal stress. The activity of antioxidant enzymes, including GST, SOD, CAT, GPx and GR, was significantly influenced by the interaction between temperature and M. aeruginosa (p < 0.05). A positive correlation was observed between toxic M. aeruginosa exposure and elevated SOD and GPx activities at 30 °C, demonstrating that SOD and GPx may help C. fluminea defend effectively against MCs under thermal stress. Furthermore, significant interactive effects between toxic M. aeruginosa and temperature were also observed in ROS and MDA (p < 0.05). The results of the PCA and IBR index also evidenced the apparent influence of toxic M. aeruginosa and thermal stress on oxidative stress responses of C. fluminea. The eggNOG and GO annotations confirmed that a substantial portion of differentially expressed genes (DEGs) exhibited associations with responses to oxidative stress and transporter activity. Additionally, KEGG analysis revealed that abundant DEGs were involved in pathways related to inflammatory responses, immune functions and metabolic functions. These findings improve our understanding of the mechanism of the physiological adaptation in bivalves in response to cyanotoxins under thermal conditions, potentially enabling the evaluation of the viability of using bivalves as a bioremediation tool to manage CYBs in eutrophic waters.