High species diversity and abundance of the epibenthic community in an oxygen-deficient basin

Abstract

Oxygen-deficient basins are common features of the ocean¹. Studies of the response of benthic communities to low-oxygen conditions have previously been restricted to sediment infauna, and have reported mass mortalities during sudden oxygen depletion^2–4 and low species diversity during sustained oxygen deficiencies^5,6. The deep epibenthic fauna of a 220-m deep fjord in British Columbia experiences annual conditions of low oxygen (<1.0 ml l⁻¹). I have observed the reactions of the attached fauna to the changing oxygen levels during numerous dives in the submersible Pisces IV over 10 months, and report here that, despite records of the decimation of benthic invertebrate populations^2–5,7–9, this deep-water assemblage maintains a higher diversity and animal abundance than does much of the upper photic zone. The tolerance developed by this community for a wide range of oxygen conditions, including periods of anoxia, has interesting implications for physiology, behaviour and community evolution.