Algal blooms caused by Microcystis aeruginosa are a common occurrence and pose significant threats to freshwater ecosystems. This study investigates the antialgal effects and underlying mechanisms of two plant-derived fatty acids, nonanoic acid and palmitic acid, on Microcystis aeruginosa. The results show that the inhibitory effects of both fatty acids on M. aeruginosa increase with higher concentrations. Algal recovery occurs when nonanoic acid concentrations are below 0.5 mg/L and palmitic acid concentrations are below 50 mg/L. Acute toxicity tests indicate that the safe concentrations of nonanoic acid and palmitic acid are below 1.87 mg/L and 263.3 mg/L, respectively. The inhibitory effect of nonanoic acid is more pronounced under conditions of pH 5.5, 15 °C temperature, 0.75 mg/L nitrogen, and 2 mg/L phosphorus, with inhibition efficiency remaining unaffected by increased light intensity. Both fatty acids exert their strongest inhibitory effects in the early stages of addition (0–8 days), causing cell death and the release of extracellular organic matter primarily consisting of aromatic compounds and proteins. Oxidative stress analysis reveals that high concentrations of fatty acids can cause irreversible damage to the algae’s antioxidant defense system. These findings provide valuable insights for the prevention and control of cyanobacterial blooms, which can help promote the sustainable development of freshwater ecosystems.

To elucidate the spatial distribution characteristics of algal communities and their correlation with environmental factors in the Heilongjiang River, algal surveys and water quality monitoring were carried out from May to October 2023. The results were as follows: (1) In total, 234 species from 95 genera belonging to seven phyla were detected, mainly Bacillariophyta, Chlorophyta, and Cyanophyta. (2) The most dominant species in the Heilongjiang River in summer and autumn were Pseudanabaena minima (G. S. An) Anagnostidis and Phormidium gelatinosum Woronichin. The dominant species in the middle niche in summer and the dominant species in the broad niche in autumn were Bacillariophyta. (3) Canonical Correlation Analysis results revealed that the environmental factors that significantly affected the distribution of the epiphytic algae during the summer were COD, F-, and WT, while EC, TN, BOD₅, and pH significantly influenced the distribution of epiphytic algae in autumn. (4) Significant correlation heatmaps revealed that the dominant species were significantly correlated with WT and TP in the Greater Khingan Mountains in summer, whereas the dominant species were significantly correlated with COD, NH₃-N, and TP in the Heihe region, Lesser Khingan Mountains, and Sanjiang Plain. There was a significant correlation between the dominant species and TN in the Greater Khingan Mountains in autumn. The spatial distribution characteristics of the algal communities and the correlations between the dominant species and water environmental factors can provide a theoretical reference for the assessment of the water ecological health status.

Lake Taihu, China’s third-largest freshwater lake, faces severe eutrophication challenges and therefore requires innovative ecological restoration strategies. This study systematically evaluates the ecological effects of aquatic vegetation restoration in Baimao Bay through comprehensive analysis of macrobenthic communities and environmental parameters, demonstrating significant water quality improvements including a 42.9% decrease in total phosphorus, a 69.4% decline in chl-a concentration, a 34.8% reduction in ammonium nitrogen, and a 81.2% increase in water transparency. Multivariate analysis revealed a fundamental ecological driver shift where post-restoration pH and transparency replaced nutrients as dominant factors, reducing total nitrogen/total phosphorus influence by 40–60%, while filter-feeding species (predominantly bivalves and gastropods) became the dominant macrobenthic biomass group (72.4%) with pollution-tolerant oligochaetes decreasing by 69.1% in abundance, alongside distinct spatial heterogeneity showing pH-regulated lakeshore communities (8.37 to 8.45), transparency-governed shallow-water communities (H′ = 1.35), and a residual nutrient-influenced deep-water area, with a shallow-water area (64 cm) and chlorophyll-a levels (<10 μg/L) for effective eutrophication reversal.