MEPS 162:1-10 (1998)  -  doi:10.3354/meps162001

Black pools of death: hypoxic, brine-filled ice gouge depressions become lethal traps for benthic organisms in a shallow Arctic embayment

R. G. Kvitek1,*, K. E. Conlan2, P. J. Iampietro3

1Institute for Earth System Sciences & Policy, California State University Monterey Bay, Seaside, California 95039, USA
2Canadian Museum of Nature, PO Box 3443, Station D, Ottawa, Ontario, Canada K1P 6P4
3Moss Landing Marine Labs, Moss Landing, California 95039, USA

Numerous small (9 ± 7 m2, mean ± SD) depressions filled with dark water were found covering 14% of the shallow (<10 m) sea floor of Resolute Bay, NWT, Canada, on July 28, 1995. The water in these black pools was hypoxic, warmer, and more saline and sulfide rich than surrounding bottom water. These pools also contained high numbers of dead epibenthic species, including: shrimps, amphipods, mysids, bivalves, gastropods, sea cucumbers, and fishes. Infaunal abundance and biomass, as well as benthic chlorophyll concentrations, were significantly lower inside the black pools than in the surrounding sediments. The pools persisted until the first strong wind to occur after annual sea-ice break-up. A year later (July 1996), sulfide-rich black saline pools were again found in the same depressions as well as in new depressions formed by grounding ice during the previous summer. We hypothesize that the pools form annually, as the sea ice expels dense brine, which sinks and collects in previously formed ice gouge depressions on the shallow slopes of Resolute Bay. Benthic respiration would be sufficient to drive the stratified water in the pools to anoxia in the absence of currents and turnover, resulting in microbial production of highly toxic sulfides. Once established, the pools persist as lethal traps for benthic and demersal organisms until dispersed by wind or waves after breakup of the annual ice cover.

Brine pools · Ice scour · Anoxia · Arctic · Benthos · Disturbance · Mortality · Polar

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