Oxidative Stress and Biomarker Responses in the Atlantic Halibut After Long Term Exposure to Elevated CO2and a Range of Temperatures

Oceans are warming and pH levels are decreasing as a consequence of increasing levels of dissolved CO 2 concentrations. The CO 2 emissions are predicted to be produce in greater and faster changes in the ocean than any other event in geological and historical records over the past 300 million years. Marine organisms will need to respond to multiple stressors but the potential consequences of global change-related effects in fish are not fully understood. Since fish are affected by many biotic and abiotic environmental variables, including temperature and CO 2 fluctuations, it is critical to investigate how these variables may affect physiological and biochemical processes. We investigated the effects of elevated CO 2 levels (pH of 8.0, which served as a control, or 7.6, which is predicted for the year 2100) combined with exposure to different temperatures (5, 10, 12, 14, 16, and 18 °C) in the Atlantic halibut ( Hippoglossus hippoglossus ) during a three month experiment. We assessed effects on antioxidant and cholinesterase enzymes (AChE and BChE), and CYP1A enzyme activities (EROD). The treatments resulted in oxidative stress, and damage was evident in the form of protein carbonyls which were consistently higher in the elevated CO 2 -treated fish at all temperatures. Analyses of antioxidant enzymes did not show the same results, suggesting that the exposure to elevated CO 2 increased ROS formation but not defences. The antioxidant defence system was insufficient, and the resulting oxidative damage could impact physiological function of the halibut on a cellular level.