Bioturbation-Driven Release of Organic Contaminants from Baltic Sea Sediments Mediated by the Invading Polychaete Marenzelleria neglecta

Abstract

Baltic Sea sediments are among the world's most polluted regarding eutrophication and contamination. Eutrophication-induced hypoxia has caused depletion of bioturbating macrofauna in vast areas, producing laminated sediments. We investigated if reoxygenation and colonization by the invading deep-burrowing polychaete Marenzelleria neglecta may cause an augmented contaminant release from Baltic Sea sediments. Intact laminated sediment cores were exposed either to in situ hypoxia, reoxygenation, or reoxygenation combined with bioturbating M. neglecta. The release fluxes of particle-associated (N(Pat)) and dissolved (N(Diss)) PCBs and chlorinated pesticide residues (POPs) were quantified (GC-ECD) after 85 d along with contaminant concentrations in sediment and biota. Lavoisier-based mass transfer coefficients (Kf) were calculated from N(Diss). Sediment contaminant concentrations were high (sigmaPCB7: 42-52 ng g(sediment)(-1) dw) due to emissions from Stockholm. N(Diss) always exceeded N(Part) by an order of magnitude. Bioturbation enhanced N(Diss) and Kf from hypoxic sediments 0.7-3 times while reoxygenation alone had no significant effect. M. neglecta accumulated low amounts of contaminants but significantly stimulated aquatic release of bioavailable sequestered contaminants. Bioturbation should be included in aquatic contaminant fate models. We advise to consider quiescent pollutant sources and possible ecological shifts when aiming to restore eutrophicated aquatic environments.

The impact of sediment bioturbation by secondary organisms on metal bioavailability, bioaccumulation and toxicity to target organisms in benthic bioassays: Implications for sediment quality assessment

“…The bioturbation of sediments by large benthic invertebrates alters sediment redox chemistry by mixing pre-stratified zones in the sediment, and increasing the penetration of electron acceptors such as dissolved O 2 , NO 3 -and SO 4 2-into anoxic sediments (Aller et al, 2001;Granéli, 1979;Matisoff et al, 1985;Pischedda et al, 2008; Volkenborn et al, 2010). Redox changes can alter metal binding affinities between the solid and dissolved phases, significantly modifying the speciation and bioavailability of most metals in sediments (De Jonge et al, 2012;Doyle and Otte, 1997;Granberg et al, 2008). The concentration of AVS has a major influence on metal bioavailability, and for sediments containing a molar excess of acid volatile sulfide (AVS) over simultaneously extractable metals (SEM, ΣCd, Cu, Ni, Pb, Zn), it is predicted that the porewater concentrations of these metals will be negligible and should not cause direct toxicity to benthic organisms Hansen et al, 2005;Lawrence et al, 1982).…”

Recent advances in the field measurement of the diffusion flux of hydrophobic organic chemicals at the sediment-water interface

“…To obtain sufficient detection sensitivity, the cross-section area of a sorbent phase must be large enough to induce large amounts of chemicals to be released from sediment. In addition, although the benthic chamber approach has not been found to influence ebullition-facilitated flux [47], the vitality of benthic organisms inside the chamber may decrease after a few days under anaerobic conditions, thereby leading to a reduction in the bioturbation-driven release of chemicals [48]. …”

Consequences of artificial deepwater ventilation in the Bornholm Basin for oxygen conditions, cod reproduction and benthic biomass – a model study

“…The great capacity of Marenzelleria-bioturbated sediments to store phosphorus was demonstrated by the fact that twice as much was bound annually to the present-day oxic sediments in the Stockholm archipelago as annually could be removed by the sewage treatment plants in Stockholm. Another possibility is that changed redox conditions in the sediment and activity of Marenzelleria spp. could increase the flux of contaminants such as PCBs compared to if the sediment remains anoxic (Granberg et al, 2008). showed that contaminants and cadmium could be either buried or remobilized in the sediment because of the activity of different infaunal species.…”