IMPACT OF BIOTURBATION BY ARENICOLA-MARINA ON THE FATE OF PARTICLE-BOUND FLUORANTHENE

The fate of particle-bound C-14-fluoranthene deposited at the sediment -water interface in microcosms with different densities (0 to 300 m(2) ) of Arenicola marina was followed for 28 d. Worms had a pronounced ef fect on the degradation rate of fluoranthene. Defecated material quick ly buried the surface layer of C-14-fluoranthene into deeper layers of the sediment, where degradation of fluoranthene was much slower than at the more reactive surface sediment in microcosms without A. marina. Only 0.3 and 2.9% of C-14-fluoranthene was mineralised to (CO2)-C-14 after 28 d in treatments with and without A. marina, respectively. The re was no significant difference between degradation rates among diffe rent densities of A. marina, although the mixing of fluoranthene into deeper sediment layers was enhanced at higher worm densities. The (DOC )-C-14 and (POC)-C-14 (particulate and dissolved organic C-14) in the overlying water were negatively related with worm density. The ventila ting currents of A. marina may have repositioned C-14-activity from th e water into deeper sediment layers, which then acted to filter both d issolved and bound fluoranthene. C-14-activity was high in worms after 28 d, approximately an order of magnitude higher than that mineralise d to (CO2)-C-14 during this period. The removal of deposited organic c ontaminants on sediment surfaces through degradation at the highly rea ctive sediment-water interface or through local transport by currents or wave action can be reduced as a result of burial of contaminants by bioturbating organisms. Contaminants may thus persist longer in the s ediment environment and will be released from the sediment over a prol onged period of time. Enhanced biological transport of contaminants to depth can lead to increased exposure of infauna.