Several aspects of the effects and interactions between oxygen concentration and organic enrichment, water flow velocity, and 'sublethal predation' are studied in laboratory experiments on the common infaunal brittle stars Amphiura filiformis and A. chiajei. At slightly higher oxygen saturations (about 10% oxygen saturation) than those resulting in mortality, a change was noted in the brittle star behaviour. They left their burrow systems and elevated their central disk some cm above the sediment surface standing on their arms. No such behavioural change, compared to control, was observed during exposure to moderate hypoxia (18 to 30% oxygen saturation). However, it was noted during exposure to moderate hypoxia that both arm regeneration rate and disk growth was reduced in A. filiformis. No such response in arm regeneration rate was observed for A. chiajei. Both species responded positively to increased organic enrichment. The fact that the arm regeneration rate of A. filiformis exposed to high organic enrichment and moderate hypoxia was similar to the control suggests that this response may depend on an increased ventilation demand due to increased sulphide concentration in the sediment. An increased arm regeneration rate was observed in moderate water flow velocity (0.5 cm s-1) compared to low flow velocity (0.1 cm s-1) in moderate hypoxia (18% oxygen saturation). However, no differences in arm regeneration rates were observed in normoxia between water flows, indicating that under conditions of low oxygen, growth is affected by water flow. The hypoxic response of two marine soft-bottom communities were studied in a manipulative microcosm experiment in three levels of oxygen concentration (6 to 7%, 12% and >80% oxygen saturation). In both communities significant reductions in both abundance and species richness were observed at 6-7% oxygen saturation. However, when exposed to 12% oxygen saturation the response differed between communities. In the community collected at a site with an oxidised top sediment the diversity decreased, but not the total abundance. However, the community taken at an organic loaded site, and characterised by a more reduced sediment, both abundance and diversity decreased at 12% oxygen saturation.