Biological traits and the transfer of persistent organic pollutants through river food webs

Freshwater organisms are still at risk from the legacy, bioaccumulation and biomagnification of persistent organic pollutants (POPs), but factors affecting their transfer through food webs are poorly understood. Here we investigate the transfer pathways of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and organochlorine (OCs) through a complex river food web, assessing the distribution and flux between basal resources (n = 3), macroinvertebrate taxa (n = 22) and fish (n = 1). We investigate the effects of biological traits on the observed patterns and use trait-based models to predict POP bioaccumulation. Transfer pathways differed among chemical groups, with PCBs apparently associated with detrital pathways, PBDEs with autochthony and herbivory (e.g. microbial biofilms), and OCs associated equally with both detrital and herbivorous transfer pathways. Biological traits such as habitat affinity, feeding behaviour and body size also explained some of the variation in pollutant burdens between organisms occupying similar trophic levels. Trait-based models indicated that relationships between contaminants, trophic transfers and traits were relatively well conserved across a wider array of river food webs. Although providing more consistent predictions of POP bioaccumulation than steady-state models, variability in POP bioaccumulation across food webs limited the accuracy of trait-based predictions. As some of the first data to illustrate how ecological processes alter the flux of persistent pollutants through river food webs, these results reveal important links between POPs and contrasting energetic pathways. These data also show the utility of models and trait-based methods in the assessment of persistent contaminants, but further field validations are required