Thermotolerance and the effects of hypercapnia on the metabolic rate of the ophiuroid Ophionereis schayeri: Inferences for survivorship in a changing ocean

► Temperature and hypercapnia/pH affect respiration in Ophionereis schayeri. ► Hypercapnia/low pH causes narcosis and mucus production in O. schayeri. ► Survivorship at 25 °C for 5 weeks is 85%; brittle stars did not cope with > 26 °C. ► O. schayeri is at its thermotolerance limits and may not survive further increases.