FATE AND EFFECTS OF SEDIMENT-ASSOCIATED ACETYL CEDRENE IN SEDIMENTS INHABITED BY THE DEPOSIT FEEDER, CAPITELLA SP. I

摘要

The combined effects of Capitella sp. I density and sediment-associated fragrance material (acetyl cedrene, AC) were examined on population level for Capitella sp. I (i.e., biomass, mortality and reproduction) and on fate of sediment associated AC in sediments with different organic matter contents (4% and 2.7%). After 14 days exposure to sediment-associated AC at different concentrations, a loss of more than 95% and 85% AC was observed in sediments of high and low organic matter contents, respectively in the presence of worms, whereas the removal was less than 31% and 13% in systems without worms. So, the presence of worms significantly reduced the concentration of AC in the sediment compared to systems without worms. However, no difference in removal of sediment-associated AC was observed at higher worm density compared to lower density. The remaining AC was concentrated mainly in fecal pellets and this to a higher magnitude than in sediment (a factor of 11- 32). The AC concentration in overlying water was minimal, and no AC was detected in worm tissues of Capitella sp. I. The implication from the present study is that Capitella play a key role in the biotansformation of organic contaminants, like AC, in the aquatic environment. No interaction of density and AC exposure concentration were found on either individual wet weights or on population biomass (wet weights) at either organic matter contents. It was observed that the food availability of individuals was density dependent, and which was intense by decreasing the organic matter content in sediment. A negative density influence on Capitella sp. I reproduction was observed at high density regardless of organic matter contents which may infer that energy allocation between reproduction and growth is changed at low density when exposed to AC. An increase of both individual and population wet weights with increasing AC concentration may be caused by the utilization of AC as a carbon source. However, the exact mechanism was not clear from the results obtained in the present study. Capitella sp. I is one of the dominating organisms thriving in the organically enriched habitats just outside sewage outlets. Thus, since one of the most significant results from the present study is that worm presence affect the persistence of sediment-associated AC by increasing the removal (e.g., by biotransformation) severely, this may have implication for risk assessment of sediment-associated organic contaminants.