Hypoxia-Induced Physiological and Immune System Effects in Atlantic Croaker from Chesapeake Bay

Hypoxia, low dissolved oxygen (DO), is an increasingly common problem during the summer months in the Chesapeake Bay due to natural and anthropogenic factors. In this study the physiological and immune system responses of Atlantic croaker to sublethal hypoxia were evaluated in the laboratory and the field using a suite of biomarkers. Acute (24-48 h) and chronic (96-144 h) exposures to hypoxia (DO = 2.0 mg/L) were determined under laboratory conditions and field samples of Atlantic croaker were collected by hook-and-line from a reference and a hypoxic site in the Bay from May to September in 2012 and 2013. Blood and tissue samples were collected to assess overall health, reproductive, endocrine, and immune responses. Histopathology, vitellogenin, gonadotropin releasing hormone (GnRH), and phagocytosis analyses were performed. Organ damage, hyperglycemia, decreased vitellogenin and GnRH levels, and lowered phagocytic activity were observed in hypoxic fish in the lab and the field. Overall, croaker health and immune function were impaired due to hypoxic exposure. Improved information on immune response and croaker hypoxia biomarkers were key results from this project.