Rising levels of atmospheric carbon dioxide could be curbed by large-scale sequestration of CO 2 in the deep sea. Such a solution requires prior assessment of the impact of hypercapnic, acidic seawater on deep-sea fauna. Laboratory studies were conducted to assess the short-term hypercapnic tolerance of the deep-sea Tanner crab Chionoecetes tanneri, collected from 1000 m depth in Monterey Canyon off the coast of central California, USA. Hemolymph acidbase parameters were monitored over 24 h of exposure to seawater equilibrated with ~1% CO 2 (seawater P CO 2 6 torr or 0.8 kPa, pH 7.1), and compared with those of the shallow-living Dungeness crab Cancer magister. Short-term hypercapnia-induced acidosis in the hemolymph of Chionoecetes tanneri was almost uncompensated, with a net 24 h pH reduction of 0.32 units and a net bicarbonate accumulation of only 3 mM. Under simultaneous hypercapnia and hypoxia, short-term extracellular acidosis in Chionoecetes tanneri was completely uncompensated. In contrast, Cancer magister fully recovered its hemolymph pH over 24 h of hypercapnic exposure by net accumulation of 12 mM bicarbonate from the surrounding medium. The data support the hypothesis that deep-sea animals, which are adapted to a stable environment and exhibit reduced metabolic rates, lack the short-term acid -base regulatory capacity to cope with the acute hypercapnic stress that would accompany large-scale CO 2 sequestration. Additionally, the data indicate that sequestration in oxygen-poor areas of the ocean would be even more detrimental to deep-sea fauna.KEY WORDS: CO 2 · Deep sea · Physiology · Decapod crustacea · Acid-base regulation ·Chionoecetes tanneri · Cancer magister
Resale or republication not permitted without written consent of the publisherThe ocean's large-scale absorption, as well as possible future anthropogenic sequestration of atmospheric CO 2 , will result in long-term acidification of the water. The deep-sea crab Chionoecetes tanneri (collected from Monterey Canyon at 1000 m depth) is unable to regulate extracellular pH during short-term CO 2 exposure. The results of Pane & Barry support the hypothesis that hypercapnia will have a profound physiological impact on deep-sea organisms.