Assessment of the effects of discontinuous sources of contamination through biomarker analyses on caged mussels A. De los Ríos a , B. Echavarri-Erasun a , M.-H. Dévier b,c , K. Le Menach b,c , H. Budzinski b,c , M. Ortiz-Zarragoitia d,e , A. Orbea d,e , J.A. Juanes a , M.P. Cajaraville d,e, ⁎ a Environmental Hydraulics Institute “IH Cantabria”, University of Cantabria, c/ Isabel Torres no 15, 39011 Santander, Spain b Univ. Bordeaux, EPOC, UMR 5805, LPTC unit, 351 crs de la Libération, F-33400 Talence, France c CNRS, EPOC, UMR 5805, LPTC unit, F-33400 Talence, France d Laboratory of Cell Biology and Histology, Department of Zoology and Animal Cell Biology, Faculty of Science and Technology, University of the Basque Country (UPV/EHU), Sarriena z/g, E-48940 Leioa, Basque Country, Spain e Research Centre for Experimental Marine Biology and Biotechnology PIE, University of the Basque Country (UPV/EHU), Areatza z/g, E-48620 Plentzia, Basque Country, Spain HIGHLIGHTS • Heavy rains favor the discharge of con- taminants from discontinuous sources. • Chemical analyses succeeded in track- ing contamination from discontinuous sources. • Measured contaminants did not reach levels affecting mussels health. • Changes in food availability provoked by rains may have affected mussels health. GRAPHICAL ABSTRACT abstract article info Article history: Received 25 January 2018 Received in revised form 23 March 2018 Accepted 24 March 2018 Available online xxxx Editor: D. Barcelo The present study analysed potential adverse effects of discontinuous sources of contamination, namely the dis- charge 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 biolog- ical 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. Lyso- somal 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 vitel- logenin 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 endo- crine 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 Keywords: Combined sewer overflow Runoff Caged mussels Bioaccumulation Biomarkers Science of the Total Environment 634 (2018) 116–126 ⁎ Corresponding author at: Laboratory of Cell Biology and Histology, Science and Technology Faculty, University of the Basque Country, Sarriena z/g, 48940 Leioa, Basque Country, Spain. E-mail address: mirenp.cajaraville@ehu.eus. (M.P. Cajaraville). https://doi.org/10.1016/j.scitotenv.2018.03.297 0048-9697/© 2018 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv