Purpose

Cyanobacterial blooms pose a serious threat to aquatic environmental health and have emerged as a primary issue in the recovery of eutrophic lakes. In order to comprehensively establish the effects of cyanobacterial blooms on nutrients in the aquatic environment, nutrient migration and transformation were studied in freshwater and sediments during cyanobacterial bloom decomposition.

Materials and methods

Cyanobacteria and sediments were collected from Zhushan Bay, in Taihu Lake, and the process of cyanobacterial decomposition was simulated in the laboratory. The focus of this research was to assess the effects of cyanobacterial decomposition on physicochemical parameters and nutrient concentrations in water, the vertical distribution of nutrients in sediments. We also determined the moisture content (ΔC_w) and organic matter content (ΔOM) in surface sediments. Correlations were assessed between cyanobacterial decomposition and nutrient concentrations in water, with ΔC_w and ΔOM in surface sediments simultaneously analyzed.

Results and discussion

In the water column, electric conductivity (Ec) was found to significantly increase, while dissolved oxygen (DO) and oxidation reduction potential (ORP) rapidly reduced. In addition, pH initially decreased and then increased, while ultraviolet light (UV₂₅₄) exhibited an opposite trend, which was related to the release and degradation of organic matter during the decomposition of cyanobacteria. Other nutrient concentrations were found to increase gradually with time, with the exception of nitrate nitrogen (NO₃⁻–N), indicating that nutrients undergo temporal transitions between forms during cyanobacterial decomposition. Cyanobacterial decomposition causes ΔOM and ΔC_w to increase in surface sediment layers, affecting the vertical distribution of nutrient species in the sediment. The water-sediment interface nutrient flux intensity was ranked in the order total nitrogen (TN) > ammonia nitrogen (NH₄⁺–N) > NO₃⁻–N > total phosphorus (TP), which was related to the settlement of cyanobacterial debris during cyanobacterial decomposition. Good binomial relationships (R² > 0.90, p < 0.05) were found between cyanobacterial density and nutrient concentrations in the waterbody, as well as between cyanobacterial density and ΔOM or ΔC_w in the surface sediment.

Conclusions

Cyanobacterial decomposition affected various water quality parameters, leading to nutrient migration and transformation in the water-sediment interface, providing nutrients to drive cyanobacterial bloom development.

中文翻译：

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蓝细菌的积累和分解对水和沉积物微环境的影响

目的

蓝藻水华对水生环境健康构成严重威胁，并已成为富营养化湖泊恢复中的主要问题。为了全面建立蓝藻水华对水生环境中养分的影响，研究了蓝藻水华在分解过程中在淡水和沉积物中的养分迁移和转化。

材料和方法

收集太湖竹山湾的蓝细菌和沉积物，并在实验室模拟了蓝细菌的分解过程。这项研究的重点是评估蓝细菌分解对理化参数和水中养分浓度，沉积物中养分的垂直分布的影响。我们还确定水分含量（Δ Ç_瓦特在表面沉积物）和有机物含量（ΔOM）。评估了蓝细菌分解与水中营养物浓度之间的相关性，同时分析了表面沉积物中的ΔC _w和ΔOM。

结果和讨论

在水柱中，发现电导率（Ec）显着增加，而溶解氧（DO）和氧化还原电位（ORP）迅速降低。此外，pH值先降低后升高，而紫外线（UV ₂₅₄）则呈现相反的趋势，这与蓝细菌分解过程中有机物的释放和降解有关。除硝酸盐氮（NO ₃ ^-- N）以外，其他养分浓度也随时间逐渐增加，这表明在蓝细菌分解过程中，养分经历了形态之间的时间转换。蓝藻分解导致ΔOM和Δ Ç_瓦特增加地表沉积物层，影响沉积物中营养物质的垂直分布。水-沉积物界面养分通量强度按总氮（TN）>氨氮（NH ₄ ⁺ -N）> NO ₃ ^-- N>总磷（TP）的顺序排列，这与蓝藻碎片的沉降有关在蓝细菌分解过程中。好二项式关系（- [R ²  > 0.90，p  <0.05）的蓝藻密度和营养物浓度在水体，以及间蓝藻密度和ΔOM或Δ之间发现Ç_瓦特在表面沉积物。

结论

蓝细菌的分解影响了各种水质参数，导致营养物在水-沉积物界面中迁移和转化，从而提供了驱动蓝藻水华发展的养分。