Lethality of increasing CO2 levels on deep-sea copepods in the western North Pacific

The first CO2 exposure experiments on several species of pelagic copepods inhabiting surface and deep layers in the western North Pacific were conducted. Living organisms were collected from two layers between the surface and 1,500 m between latitudes of 11 and 44 degrees N, and they were exposed aboard ship to various pCO(2) up to about 98,000 mu atm. Mortality of copepods from both shallow and deep layers in subarctic to subtropical regions increased with increasing pCO(2) and exposure time. Deep-living copepods showed higher tolerance to pCO(2) than shallow-living copepods. Furthermore, deep-living copepods from subarctic and transitional regions had higher tolerances than the subtropical copepods. The higher tolerances of the deep-living copepods from subarctic and transitional regions may be due to the adaptation to the natural pCO(2) conditions in the subarctic ocean.