Biogeochemical transformations and potential polyaromatic hydrocarbon degradation in macrofaunal burrow sediments

Abstract

ABSTRACT-A variety of polyaromatic hydrocarbons (PAH) includmg naphthalene, phenanthrene, acenaphthene, and dibenzothiophene were degraded with little or no lag in oxic slurries of marine sedi m e n t~ 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 sedirnents; relative rates of degradation varied among the burrow wall sediments depending on the PAH assayed. Comparisons of the effects of available electron acceptors (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.

Relative importance of macrofaunal burrows for the microbial mineralization of pyrene in marine sediments: impact of macrofaunal species and organic matter quality

“…2). These results are consistent with the established view of microbial PAH degradation being highly favored by the presence of molecular oxygen (Cerniglia & Heitkamp 1989), and also with results from Chung & King (1999) and Coates et al (1996) who found no correlation between PAH mineralization and the availability of other electron acceptors such as nitrate, sulfate and ferric iron in moderately polluted field-collected sediment.…”

“…The intensity of the macrofaunal impact on biogeochemical processes has, however, been shown to be highly species-specific and particularly attributed to differences in macrofaunal behavior (Aller & Yingst 1985, Andersen & Kristensen 1991. Since most studies apply whole sediment or 2-compartment models when studying contaminant fate, the relative importance of macrofaunal burrows, compared to surface and bulk sediments, for the microbial degradation of PAHs and other contaminants in marine sediment is yet highly unexplored with, to our knowledge, only 2 published studies (Chung & King 1999.…”

Effects of the polychaetes Arenicola marina and Nereis diversicolor on microbial pyrene mineralization

“…Burrows may, thus, be considered extensions of the oxic surface layer with respect to pyrene degradation. These observations are in accordance with Chung & King (1999) and Granberg et al (2005), who also found that mineralization rates in burrow sediments were much higher than in the surrounding sediment, and in a few cases even higher than mineralization rates in surface sediment. Aerobic bacteria able to grow solely on pyrene were found in burrow sediment from both polychaetes at the same or slightly higher abundances than in surface sediments (Fig.…”

“…The similarities in pyrene degradation between burrow and surface sediments suggest that the oscillating oxygen concentration in ventilated burrows is sufficient to maintain a PAH-degrading capacity similar to the sediment surface with more constant oxygen concentrations. Since PAH degradation rates seem to depend on oxygen exposure time (Chung & King 1999), the actual in situ mineralization rates are probably lower in burrows compared with surface sediments because oxygen is not always present in the burrow (Timmermann et al 2006). Given the high potential for PAH mineralization in the burrows, we expect pyrene degradation to occur whenever oxygen is provided by ventilation.…”

“…Irrigated burrows often show enhanced activity of biogeochemical processes (Kristensen et al 1985, Mayer et al 1995, Papaspyrou et al 2006) and both bacteria and meiofauna are often more abundant in burrows and tubes compared with the surrounding sediment (Reise 1981, Papaspyrou et al 2006. The significance of burrow structures as sites of enhanced capacity for microbial PAH mineralization have also been documented (Chung & King 1999, Granberg et al 2005.…”