Biogeochemical transformations and potential polyaromatic hydrocarbon degradation in macrofaunal burrow sediments

A variety of polyaromatic hydrocarbons (PAH) including naphthalene, phenanthrene, acenaphthene, and dibenzothiophene were degraded with Little or no lag in oxic slurries of marine sediments from burrow walls constructed by benthic macrofauna. PAH degradation potentials of burrow sediments from the polychaetes Nereis virens and Clymenella torquata, the mollusc Mya arenaria and the enteropneust Saccoglossus bromophenolosus were generally greater than potentials for non-burrow sediments; relative rates of degradation varied among the burrow wall sediments depending on the PAH assayed. Comparisons of the effects of available electron accepters (oxygen, nitrate, ferric iron, sulfate) indicated that significant degradation of benzene, hexadecane and PAH occurred only in the presence of molecular oxygen. However, the capacity for oxic phenanthrene degradation was stable during incubations with alternating oxic and anoxic conditions, suggesting significant anoxia tolerance. Although burrow wall sediments were biogeochemically distinct with respect to rates of sulfate reduction, potential denitrification and potential ammonia oxidation, these patterns were not related to those of PAH degradation.