Changes in survival rates of harpacticoid copepods with increases in dissolved CO2 in seawater

Abstract

Recently, many studies are carried out on the effect of increased dissolved carbon dioxide in seawater and reduced seawater pH (ocean acidification) that corresponds to the increasing atmospheric CO2. For our studies, as part of growing need to ascertain the effects of ocean acidification on marine ecosystem and organisms, harpacticoid copepods, one of the most abundant meiofaunal groups were subjected to laboratory experiments. The purpose of this study was to evaluate physiological and ecological responses of harpacticoid copepods to the various concentrations of dissolved CO2 which might be observed in the future. First, we examined the changes in survival rates of harpacticoid copepods with different CO2 concentrations in seawater. Each test was performed using different exposure methods to determine the most efficient method which best results in clear species responses to various concentrations of dissolved CO2 in seawater. Survival rates of harpacticoid copepods collected from the tidal flat were 35% in control groups exposed to 400 ppm and 30% in treatment groups exposed to 1000 ppm for 48 hours. Survival rates from the experiments using the CO2-addition experimental system at the Seto Marine Biological Laboratory, Kyoto University, were 63.3% in control groups exposed to 400 ppm, 55% and 55.4% in treatment groups exposed to 600 and 1000 ppm for 24 hours. Specific survival rate