Effects of low dissolved oxygen on survival and asexual reproduction of scyphozoan polyps (Chrysaora quinquecirrha)

Hypoxic conditions are common in many coastal environments such as Chesapea ke Bay. While medusae appear to be quite tolerant of low dissolved oxygen ( DO) concentrations, the effects of hypoxia on the benthic polyp stages are unknown. Chrysaora quinquecirrha (DeSor) polyps, and were subjected to 5 DO treatments (air-saturated [control], 3.5, 2.5, 1.5 and 0.5 mg l(-1)) in th e laboratory. Polyp survival and development were documented over 24 d. Vir tually no mortality occurred in any treatment during the first 5 d. Total p olyp mortality after 24 d was 59.3% at the lowest DO concentration, whereas <3% mortality was observed in the air-saturated treatment. Formation of st olons and strobilae occurred in all treatments, however, the proportions of polyps undergoing stolonation and strobilation were significantly greater in all DO concentrations above 0.5 mg l(-1). Polyp encystment was not obser ved in any treatment over the course of the 24 d experiment. These results indicate that polyps can survive and asexually propagate even during prolon ged exposure to hypoxic conditions.