Microcystins (MCs) pose potential threat for both aquatic organisms and humans, whereas their occurrence in response to hydrodynamic alterations are not clearly understood. Here, spatiotemporal variations of dissolved MC-RR and MC-LR were evaluated monthly in 2016 in the Yulin River, a tributary of the Three Gorges Reservoir (TGR). The environmental factors that linked to MCs concentration were discussed. The results revealed that MC-RR maximumly reached 3.55 μg/L, and the maximum MC-LR concentration exceeded the threshold value of 1.0 μg/L recommended by the WHO. MCs concentrations were higher during the flood season and decreased from the estuary to the upstream reach of the Yulin River. Ecological risk assessment confirmed that MC-LR had significant adverse effects on the benthonic invertebrates Potamopyrgus antipodarum. MCs content in the sediment was 1.70- to 20-fold higher than that in suspended particulate matter (SPM). The impacts of environmental factors on the MCs profile differed between flood and dry seasons and the longitudinal differences of MCs were determined by the longitudinal profile of water velocity and SPM content, which were affected by TGR operations. This study suggested that the occurrence of MCs in the Yulin River were influenced by hydrologic regime in TGR.

微囊藻毒素（MCs）对水生生物和人类均构成潜在威胁，但是人们对它们对水动力变化的响应却未明确了解。在这里，2016年每月在三峡水库（TGR）的支流榆林河每月评估溶解的MC-RR和MC-LR的时空变化。讨论了与MCs浓度有关的环境因素。结果表明，MC-RR最大达到3.55μg/ L，最大MC-LR浓度超过了WHO推荐的1.0μg/ L阈值。在洪水季节，MCs浓度较高，而从河口到榆林河上游则有所降低。生态风险评估证实，MC-LR对底栖无脊椎动物Potamopyrgus antipodarum有明显的不利影响。沉积物中的MC含量比悬浮颗粒物（SPM）高1.70至20倍。在洪水季节和干旱季节，环境因素对MCs的影响有所不同，MCs的纵向差异取决于水速和SPM含量的纵向曲线，而TGR作业会影响MCs的纵向变化。这项研究表明，榆林河MCs的发生受TGR中水文条件的影响。