Detrimental impact of hypoxia on the mortality, growth, reproduction, and enzyme activities of planktonic mysid Neomysis awatschensis

Abstract

In recent years, marine hypoxia has frequently occurred in global coastal and estuarine waters with detrimental impacts on marine fauna. In this work, we examined the impact of hypoxia on the mortality, growth, reproduction, and enzyme activities of the mysid Neomysis awatschensis. The mortality rate of adult mysids increased by 100% within 4 h under the hypoxia treatment (2 mg/L), while that of juveniles was 53.33 ± 5.77% after 96 h. The long-term low dissolved oxygen (DO) treatment (5 mg/L for 30 d) significantly reduced the fatty acid content of mysids. A significant reproductive inhibition was also observed: the total juvenile productions in the treatment with DO at 4, 5, and 6 mg/L were only 6.5%, 24%, and 60% of the control group (DO at 8.5 mg/L), respectively. The total superoxide dismutase activity increased significantly in low oxygen treatments. Catalase and lactate dehydrogenase activities first increased and then decreased with the dropping DO concentrations. These results suggest that hypoxia has multiple impacts on marine zooplankton. This may adversely affect higher trophic level organisms and the structure and function of marine ecosystems.