MEPS 182:187-199 (1999)  -  doi:10.3354/meps182187

Importance of bioturbation and feeding by the polychaete Capitella sp. I in the degradation of di(2-ethylhexyl)phthalate (DEHP)

Rikke Hansen1,*, Thomas L. Forbes1,**, Peter Westermann2

1Department of Marine Ecology & Microbiology, National Environmental Research Institute, PO Box 358, Frederiksborgvej 399, DK-4000 Roskilde, Denmark
2Department of General Microbiology, University of Copenhagen, Sølvgade 83H, DK-1307 Copenhagen K, Denmark
*Present address: Darling Marine Center, University of Maine, Walpole, Maine 04573, USA
**Addressee for correspondence. E-mail:

ABSTRACT: A microcosm study of the effect of Capitella sp. I (Polychaeta) population density on the mineralization of a pulse addition of the plasticizer DEHP (di[2-ethylhexyl]phthalate) demonstrated a 2-fold increase in mineralization (cumulative 14CO2 production) when worms were present. An additional experiment investigated the fate of ingested particle-bound 14C-DEHP and measured the loss of ingested 14C-DEHP into 14CO2, DO14C and PO14C pools. Less than 1% of 14C consumed during a 1 h ingestion period was ultimately respired as 14CO2, while 10% was excreted as DO14C and 89% as PO14C. Approximately 1% of ingested 14C was retained in worm tissue 20 h after ingestion. Assuming density-independent feeding rates, worm respiration could account for 4.5% to 19.1% of the total microcosm 14CO2 production, suggesting that microbial respiration to 14CO2 was the dominant process. Pre-exposure of worms to DEHP (10 µg g-1 sediment dry wt) for 1 wk had no effect on the fate of ingested DEHP and distribution into the respective pools. Worms exerted a strong effect on ultimate DEHP degradation (14CO2 production) but the effect was manifest at the lowest worm density and did not increase with increasing population size. The lack of an increased effect at greater population densities may be due to population density-dependent factors acting to decrease such important parameters as individual worm ventilation and feeding rates. A density-dependent decrease in feeding rate is supported by the observation that measured 14C body burdens were highest at lowest worm densities.

KEY WORDS: Bioturbation · Capitella sp. I. · Phthalate esters · Sediment · Microbial degradation · Metabolism

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