The present study analysed potential adverse effects of discontinuous sources of contamination, namely the discharge of a combined sewer overflow (CSO) and of runoff in an urban area, the Bay of Santander (North Iberian Peninsula). Water samples and caged mussels were used to analyse concentrations of contaminants and biological responses. Mussels (Mytilus galloprovincialis) were transplanted to a marina receiving runoff from a petrol station and to a CSO discharge site. Samples were collected in synchrony with heavy rains along 62 days. Lysosomal membrane stability (LMS) and acyl-CoA oxidase (AOX) activity were measured as core biomarkers and were analysed at all sampling times. Histopathology of digestive gland and gonads, transcription levels of vitellogenin gene, volume density of black silver deposits and micronuclei formation were measured at initial and final stages of the transplant. Chemical analyses of metals, polycyclic aromatic hydrocarbons (PAHs) and endocrine disruptors were performed in water samples and mussel flesh. Mussels accumulated low concentrations of contaminants, which is in accordance with results obtained from exposure biomarkers. AOX activity decreased in all transplanted mussels after the first heavy rain, but this change seems to be related to the seasonal pattern of the enzyme activity. Mussels located close to the CSO discharge site showed a reduction in LMS after the first rain event, when compared to mussels before the transplant and to mussels from the reference location. However, this was attributable to natural environmental changes rather than to pollution. Values of the rest of analysed biomarkers were below threshold values reported for the study area.

本研究分析了不连续污染源的潜在不利影响，即下水道溢流（CSO）和市区桑坦德湾（北伊比利亚半岛）径流的排放。水样和笼养贻贝用于分析污染物的浓度和生物学响应。贻贝（Mytilus galloprovincialis）被移植到从加油站接收径流的码头和CSO排放站。在62天之内，与暴雨同步收集了样本。溶酶体膜稳定性（LMS）和酰基辅酶A氧化酶（AOX）活性被测量为核心生物标志物，并在所有采样时间进行了分析。在移植的最初和最后阶段，测量消化腺和性腺的组织病理学，卵黄蛋白原基因的转录水平，黑银沉积物的体积密度和微核形成。在水样和贻贝肉中进行了金属，多环芳烃（PAHs）和内分泌干扰物的化学分析。贻贝积聚了低浓度的污染物，这与从暴露生物标志物获得的结果一致。第一次大雨后，所有已移植的贻贝的AOX活性均下降，但这种变化似乎与酶活性的季节性变化有关。与移栽前的贻贝和参考地点的贻贝相比，靠近CSO排放点的贻贝在第一次降雨事件后的LMS降低。但是，这归因于自然的环境变化而不是污染。其余已分析生物标志物的值均低于研究区域报告的阈值。这归因于自然的环境变化而不是污染。其余已分析生物标志物的值均低于研究区域报告的阈值。这归因于自然的环境变化而不是污染。其余已分析生物标志物的值均低于研究区域报告的阈值。