Acute physiological impacts of CO2 ocean sequestration on marine animals

The biological impacts of ocean carbon dioxide (CO2) sequestration must be carefully considered before it is implemented as a mitigation strategy. This paper presented details of a study investigating the effects of high CO2 concentrations on marine fish, lobster, and octopus. The influence of water temperature on the physiological effects of CO2 was also discussed. In the first part of the study, eggs and larvae of red seabream were exposed to both CO2 and HCI-acidified seawater at identical pH levels. Seabream in the CO2 group showed a much higher mortality rate than fish in the HCI group. Other tests showed that Japanese Flounder died after complete recovery of pH in seawater equilibrated with 5 per cent CO2. Cardiac output was rapidly depressed in Yellowtail fish without significant changes in blood oxygen concentrations. Lower temperatures resulted in higher mortality and delayed pH recovery during hypercapnia in all fish. Western rock lobsters were the most tolerant to CO2 among all species tested. The recovery of hemolymph pH was complete at exposure to CO2 concentrations of 1 per cent. Changes in hemolymph bicarbonate concentrations indicated that acid-based regulatory mechanisms differed between fish and lobsters. Mortality rates for octopus were significant at CO2 concentrations of 1 per cent. The results of all tests showed that aquatic animals are more susceptible to increases in ambient CO2 levels than terrestrial animals. It was concluded that even slight elevations in CO2 concentration levels adversely affected physiological functioning in the tested species. It was concluded that CO2 sequestration in deeper, colder waters will have a more pronounced effect on aquatic animals due to the interactions between CO2 and lower temperatures, as well as the fact that most deep-sea fish are less tolerant to environmental perturbations. 3 refs., 1 tab., 3 figs