Sediment cores were collected inside and outside of a bed of a bromophenol-producing marine polychaete, Notomastus lobatus, and examined for impact of the bromophenols on sediment microflora and meiofauna around N. lobatus burrows. No significant differences were found between microbial parameters measured inside and outside of the N. lobatus bed. Integrated 6 cm cores taken adjacent to N. lobatus burrows contained 1.2 x 10' bacteria ml-l. Cell numbers were similar at control sites within the bed, but away from burrows, and not significantly different from cell numbers (1.0 X log cells ml-l) at a nearby site. 13H]-acetate net assimilation rates were 12.7 + 5.0 pm01 ml-l h-' adjacent to burrows and 11.9 * 1.4 pm01 ml-' h-' in non-burrow control cores. Microalgal biomass was 20.1 2 1.2 mg chl a m-2 adjacent to burrows and 24.3 + 1.0 mg chl a m-2 in non-burrow control cores. Microalgal production was 4.17 L 0.31 mm01 O2 m-2 h-' near burrows and 5.84 + 0.97 mm01 O 2 m-' h-' in nonburrow controls. Distribution of bacteria, microalgae, and meiofauna showed no consistent effects of proximity to the worm burrows. These data indicate that the concentrations of bromophenols found inside of the N. lobatus worm bed are not inhibitory to sediment microflora and that the microbial populations found there are adapted to exposure to these toxic compounds.

An anaerobic 2,4,6-tribromophenol debrominating bacterium, strain DSL-1, was isolated from enrichment cultures inoculated with sediment from the burrows of the bromoaromatic-producing marine hemichordates Balanoglossus aurantiacus and Saccoglossus kowalewskyi. DSL-1 preferentially removed ortho-position bromines, resulting in the transient appearance of 2,4-dibromophenol and accumulation of 4-bromophenol. Cell-free extracts and partially purified reductive debrominase preparations from DSL-1 also debrominated 2,4,6-tribromophenol, yielding 2,4-dibromophenol and 4-bromophenol. Both NADH and NADPH stimulated 2,4,6-tribromophenol reduction by partially purified debrominase. These data are consistent with a reductive debromination mechanism. The organic cosubstrate(s) and specific electron donors used by DSL-1 in vivo are currently unknown.Key words: dehalogenation, bromometabolites, bromophenols, hemichordates.

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ABSTRACT. Many marine infaunal hemichordates and polychaetes produce volatile halogenated secondary metabolites, including several brominated aromatic compounds. These compounds have been suggested to have antimicrobial activity. However, the impact of added bromometabol~tes on microbial activities in undisturbed sediments has not been assessed. This study examines the effects of a common bromometabolite, 4-bromophenol, on substrate respiration and assimilation by undisturbed sediment bacterial communities. Intact sediment cores were collected from a site inhabited by the bromophenol producing capitellid polychaete Notomastus lobatus and from a similar site having no bromometabolite producing infauna. These cores were injected with a radiolabeled suhstrate (acetate or glucose) and varying levels of 4-bromophenol, then incubated at ~n situ temperature. Rates of respiration and assimilation of the substrates at levels of 4-bromophenol ranging from ambient to 10 pg g-' (dry weight) sediment were determined. No significant inhibition of respiration or assimilation of either substrate was observed in samples from either location, even at 4-bromophenol levels lOOx the ambient concentration in wormbed sediments. These data show that this naturally occurring bromoaromatic compound has no significant effect on community activity of sediment bacteria.

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