Contaminants, benthic communities, and bioturbation: potential for PAH mobilisation in Arctic sediments

Marine benthic fauna and biological mixing were studied in relation to sediment organic enrichment and polyaromatic hydrocarbons (PAHs) in bottom sediments of Svalbard. We investigated how organic enrichment may affect the fate and chemical composition of deposited contaminants by impacting biological reworking by faunal communities. Samples were collected near active coal mines at Barentsburg and at the mouth of Grønfjord. PAH sources in both areas were coal particles and pyrolytic compounds from coal-driven power stations. The results from a bioturbation experiment were consistent with the hypothesis that fauna enhance the vertical transport of PAHs within the sediment. Faunal community composition was similar at the two sites, with polychaete worms comprising>85% of the fauna. Abundances and taxon richness were eight and ten times higher in the organically enriched sediments near Barentsburg, and total PAH concentrations were up to three times higher in Barentsburg. Unlike expectations derived from models developed for temperate regions, organic enrichment in oligotrophic areas, such as this Arctic site, enhanced the biomass and bioturbation potential of benthic communities. Hence, new insights into the relationships among enrichment, benthic communities and the fate of contaminants must be considered in management and regulatory efforts in these areas.