Effects of the polychaetes Nereis diversicolor and Arenicola marina on the fate and distribution of pyrene in sediments

Effects of the polychaetes Nereis diversicolor and Arenicola marina on the distribution, metabolism and removal of [C-14-4,5,9, 10]-pyrene in sediment microcosms were studied over 42 and 53 d, respectively. Unmetabolized pyrene, water- and organic-soluble pyrene metabolites were quantified in sediment, interstitial water and overlying water, and (CO2)-C-14 production was also assessed. Both N. diversicolor and A. marina enhanced fluxes of sediment-associated pyrene and metabolites into overlying water but to different extents. The major pathway of pyrene removal from sediments with N. diversicolor was release of water-soluble metabolites, probably formed by metabolism in N. diversicolor. In contrast, flushing of unmetabolized pyrene due to bioturbation was the major removal route from sediments with A. marina. Additionally, increased (CO2)-C-14 production and concentrations of water-soluble metabolites were also observed in overlying water indicating that A. marina also stimulated the metabolism of pyrene. The high production of water-soluble metabolites was probably due to endogenous metabolism in the lugworm itself, whereas the increased (CO2)-C-14 production indicated a stimulation of microbial metabolism. After 42 d, only 75 % of the originally added amount of pyrene remained associated to sediment particles in microcosms inhabited by N. diversicolor, whereas no significant reduction was observed in microcosms with A. marina due to the necessity of using large amounts of sediment in the lugworm experiment. The actual flux of pyrene and metabolites to overlying water was higher in microcosms with A. marina than with N. diversicolor. Both A. marina and N. diversicolor significantly enhanced the removal pyrene from the sediment, but differences in feeding and life strategies resulted in different removal paths and extents.