HYPOXIC TOLERANCE OF MARINE BENTHIC FAUNA

In stratified coastal marine waters hypoxia is a growing problem affecting bottom-dwelling animals. Earlier studies suggest oxygen concentrations of about 2 ml l-1 (Rosenberg 1980) as the lower tolerance limit for many benthic species in coastal areas. We exposed several conspicuous infaunal species on the NE Atlantic continental shelf, contained within their sediment habitat, to gradually reduced oxygen concentrations. Tolerance to hypoxia for the 8 species examined was in the range of 0.5 to 1.0 ml l-1 (8 to 15% saturation), which they could tolerate for several days to weeks. The ophiuroid Amphiura filiformis left its protected position in the sediment at an oxygen concentration of 0.85 ml l-1 (13% sat.), whereas A. chiajei emerged from the sediment at 0.54 ml l-1 (8% sat.).