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<p>Agricultural surface water pollution in farmland cultivation areas poses significant risks to water safety in reservoirs and threatens both environmental and human health. This study aims to evaluate the water quality and ecological risks in surface water reservoirs in Daqing City, Heilongjiang Province, China, by assessing the relationships between nutrient concentrations (e.g., total phosphorus (TP), total nitrogen (TN)) and microbial community diversity. We hypothesize that elevated nutrient levels (TP and TN) drive microbial community shifts and increase ecological risk in agricultural reservoirs. Water quality was assessed using the Trophic Level Index (TLI), Water Quality Index (WQI), and Integrated Water Quality Index (IWQI). The diversity of aquatic microbial communities was analyzed through 18S rRNA gene sequencing, and organic phosphorus levels were quantified by gas chromatography (GC). Results showed that total phosphorus (TP) concentrations exceeded standards, while total nitrogen (TN) approached eutrophication thresholds. Microbial analysis revealed 1887 operational taxonomic units (OTUs) and 367 genera, with species diversity higher in sediment than in water. Environmental factors influencing water samples were ranked as TP &gt; TN &gt; nitrate nitrogen (NO<sub>3</sub>-N) &gt; chemical oxygen demand (CODcr) &gt; dissolved oxygen (DO), while sediment samples were mainly influenced by TP &gt; CODcr &gt; DO &gt; TN &gt; NH<sub>3</sub>-N. Gas chromatography detected Ethoprophos (0.018&#xa0;µg/L) and Merphos (0.046&#xa0;µg/L) in a sediment sample from Dongcheng Reservoir. Ecological structure–activity relationships (ECOSAR) analysis and Risk Quotient (RQ) analyses indicated that the concentrations of both chemicals were below the half-maximal lethal concentration (LC50) toxicity limits for aquatic organisms, with low acute toxicity and minimal chronic toxicity. These findings support the hypothesis that nutrient concentrations are linked to microbial diversity and ecological risks. The study provides insights into the critical water quality challenges faced by agricultural water reservoirs and offers a basis for developing monitoring indicators and protection measures to improve water safety and support ecological health in these reservoirs.</p>

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Microbial dynamics and ecological risk assessment of water reservoirs in agricultural areas of Daqing, China

  • 期刊论文

  • 发表日期：

    2025年7月25日

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  • Ran Wang,
  • Shang Yang,
  • Wei Zhao

摘要

Agricultural surface water pollution in farmland cultivation areas poses significant risks to water safety in reservoirs and threatens both environmental and human health. This study aims to evaluate the water quality and ecological risks in surface water reservoirs in Daqing City, Heilongjiang Province, China, by assessing the relationships between nutrient concentrations (e.g., total phosphorus (TP), total nitrogen (TN)) and microbial community diversity. We hypothesize that elevated nutrient levels (TP and TN) drive microbial community shifts and increase ecological risk in agricultural reservoirs. Water quality was assessed using the Trophic Level Index (TLI), Water Quality Index (WQI), and Integrated Water Quality Index (IWQI). The diversity of aquatic microbial communities was analyzed through 18S rRNA gene sequencing, and organic phosphorus levels were quantified by gas chromatography (GC). Results showed that total phosphorus (TP) concentrations exceeded standards, while total nitrogen (TN) approached eutrophication thresholds. Microbial analysis revealed 1887 operational taxonomic units (OTUs) and 367 genera, with species diversity higher in sediment than in water. Environmental factors influencing water samples were ranked as TP > TN > nitrate nitrogen (NO3-N) > chemical oxygen demand (CODcr) > dissolved oxygen (DO), while sediment samples were mainly influenced by TP > CODcr > DO > TN > NH3-N. Gas chromatography detected Ethoprophos (0.018 µg/L) and Merphos (0.046 µg/L) in a sediment sample from Dongcheng Reservoir. Ecological structure–activity relationships (ECOSAR) analysis and Risk Quotient (RQ) analyses indicated that the concentrations of both chemicals were below the half-maximal lethal concentration (LC50) toxicity limits for aquatic organisms, with low acute toxicity and minimal chronic toxicity. These findings support the hypothesis that nutrient concentrations are linked to microbial diversity and ecological risks. The study provides insights into the critical water quality challenges faced by agricultural water reservoirs and offers a basis for developing monitoring indicators and protection measures to improve water safety and support ecological health in these reservoirs.