Brominated metabolites and reduced numbers of meiofauna organisms in the burrow wall lining of the deep-sea enteropneust Stereobalanus canadensis

The burrowing enteropneust Stereobalanus canadensis from the deep-sea benthos in the Norwegian Sea was investigated for halogenated metabolites in its body tissues and in its burrow wall lining; the latter was also searched for meiofauna organisms and bacteria. Homogenates of the enteropneust revealed the presence of three brominated metabolites, one of which was identified as 2,4,6-tribromophenol, varying in concentrations from 0.5 to 7 μg g⁻¹ WW. The two other metabolites were tentatively identified as a mono- and dibromo-derivative of a n-hexylhydroquinonemonomethylether and found in concentrations varying from 10 to 50 μg g⁻¹ WW. The bromohydroquinones were also found in burrow wall sediment at a concentration 10³−10⁴ times lower than in animal tissues, but not in adjacent sediment layers. No benthic metazoans were found in the burrow wall lining made by S. canadensis; only a slightly higherabundance of bacteria and a small foraminifer Lagena sp. was evident. These biotic results are in contrast to those obtained from the burrow wall lining made by a co-occurring echiuran. The depletion of a benthic metazoan fauna in the burrow wall lining from S. canadensis is possibly caused by the presence of toxic brominated metabolites excreted by the enteropneust.