INDUCIBLE METABOLISM OF FLUORANTHENE BY THE OPPORTUNISTIC POLYCHAETE CAPITELLA SP-I

The polychaete Capitella sp. I has been described as an enrichment opp ortunist and is one of very few species able to thrive in highly organ ic sediments heavily contaminated with polycyclic aromatic hydrocarbon s (PAH) and other organic pollutants. We examined 3 plausible explanat ions for the success of Capitella sp. I: (1) worms prevent uptake of P AH across body surfaces, (2) worms take up PAH but metabolize them eff ectively to excretable forms, and (3) worms utilize PAH as a carbon so urce. We examined the uptake and depuration of sediment-associated flu oranthene by Capitella sp. I and measured the metabolic loss of ingest ed 3-[C-14] fluoranthene into particulate (POC), dissolved (DOC) and C O2 pools. Our results show that Capitella sp. I accumulates fluoranthe ne from sediment in a concentration-dependent manner, but that body bu rdens begin to decrease after 2 d and are undetectable by 7 d despite continued exposure to sediment fluoranthene concentrations of up to 36 0 mu g (g dry wt sediment)(-1). Worms pre-exposed to PAH-contaminated sediment for 1 wk excreted substantially more ingested fluoranthene as DOC than control worms (37% vs 6% after 20 h), and retained significa ntly less fluoranthene in their tissues at the end of the experiment t han control worms (33% vs 56%). Our results are consistent with the hy pothesis that Capitella sp. I metabolize fluoranthene, but contrary to our Hypotheses 1 and 3, worms did take up fluoranthene and did not ap pear to use it as a carbon source.