Bacterial Production and Contamination Mineralization in Sediments of the Ala Wai Canal, Oahu, Hawaii

摘要

The Ala Wai canal is a small, man-made estuary that was dredged from August 2002 to October 2003 to increase water circulation and oxygen deficit in bottom waters. Rates of bacterial growth (heterotrophic production) and carbon metabolism (14C-substrate mineralization) were measured on surface sediments and core sections during three sampling events before, during, and after dredging. Heterotrophic production increased at all stations during the post- dredge sampling relative to the pre-dredge sampling. Lignin analysis indicated most of this organic matter was terrestrially derived (woody and non-woody angiosperms). Carbon substrate mineralization rates were typically highest between the confluence with the Manoa-Palalo outfall and the canal mouth, with overall rates decreasing for catechol >> 2,4,6-trinitrotoluene > phenanthrene > naphthalene > fluoranthene. Polycyclic aromatic hydrocarbon (PAH) mineralization was relatively low compared with other urbanized watersheds. Even with enhanced flow associated with the dredging operation, it is probably unlikely that significant amounts of PAHs are being exported from the canal to the adjacent coastal waters.