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

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 14 CO 2 production) when worms were present. An additional experiment investigated the fate of ingested particle-bound 14 C-DEHP and measured the loss of ingested 14 C-DEHP into 14 CO 2 , DO 14 C and PO 14 C pools. Less than 1% of 14 C consumed during a 1 h ingestion period was ultimately respired as 14 CO 2 , while 10% was excreted as DO 14 C and 89% as PO 14 C, Approximately 1% of ingested 14 C 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 14 CO 2 production, suggesting that microbial respiration to 14 CO 2 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 ( 14 CO 2 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 14 C body burdens were highest at lowest worm densities.