Parasite communities in the red mullet, Mullus barbatus L., respond to small-scale variation in the levels of polychlorinated biphenyls in the Western Mediterranean

► A study on parasite populations and communities in Mullus barbatus at a small-scale PCB gradient. ► Differentiation of the samples along the increasing PCB levels in the sediments. ► Decrease in abundance of both ectoparasites and endoparasites with increase in PCB levels. ► Significant differences in infracommunity structure and decreased predictability at increased PCB levels. ► Parasite responses to pollution validated by both chemical monitoring and effect biomarkers.