The sublethal effects of crude oil exposure on red drum (Sciaenops ocellatus)

It is well established that oil exposure induces a suite of cardiac impairments, or cardiotoxicity. Cardiotoxicity is characterized by morphological and physiological impairments in larval fish and reduced performance and aerobic scope (ASc) in juveniles and adults, which is predicted to interfere with ecological performance, though it is currently unknown. To address this, my thesis focused on the cardiotoxic impacts and downstream ecological significance of crude oil exposure on a recreationally important estuarine species, red drum (Sciaenops ocellatus). In embryonic exposures, red drum sustained sublethal effects at significantly lower concentrations of oil than pelagic species, however, they had comparable 50% lethal concentrations. This was the first study to measure reduced cardiac output performance in marine larvae following oil exposure. Subsequent studies explored the ecological implications of cardiotoxicity on a variety of performance measures. In species where social dominance is influenced by ASc, I hypothesized that oil-induced impaired ASc would predispose individuals to social subordination. When competing with unexposed conspecifics, oil exposed fish were more likely to become subordinate. To expand on this, long-term impacts of oil exposure on group competition were investigated. Groups of juveniles exposed to control or varying oil doses were housed together in either resource-rich or resource-limited environments; survival, growth, and social subordination were monitored for 8 weeks. In resource-rich environments, oil exposed fish demonstrated normal growth and resource competition. In resource-limited environments, oil exposed fish experienced reductions in growth rate and standard metabolic rate, indicating oil exposed fish were unable to compete with unexposed conspecifics when competition was high. To assess the role of impaired ASc on predation risk, fingerling groups were placed into a predator-avoidance assay. Oil groups experienced a significant reduction in time to 50% mortality compared to controls, which was accompanied by elevated hyperactivity, but not impaired swim performance or ASc. Therefore, while cardiotoxicity clearly carry ecological consequences, novel modes of toxicity may be of equal or greater importance for ecological function. Overall my thesis highlights the impacts of oil exposure on cardiac performance in larval fish, the effects of cardiotoxicity on individual and group competitions, and the ecological consequences of behavioral impairments