Integrative Ecophysiology, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, 27570, Bremerhaven, Germany.
Department of Biology/Chemistry, University of Bremen, 28334, Bremen, Germany.
J Comp Physiol B. 2018 Sep;188(5):749-764. doi: 10.1007/s00360-018-1162-5. Epub 2018 May 23.
Ocean acidification causes an accumulation of CO in marine organisms and leads to shifts in acid-base parameters. Acid-base regulation in gill breathers involves a net increase of internal bicarbonate levels through transmembrane ion exchange with the surrounding water. Successful maintenance of body fluid pH depends on the functional capacity of ion-exchange mechanisms and associated energy budget. For a detailed understanding of the dependence of acid-base regulation on water parameters, we investigated the physiological responses of the shore crab Carcinus maenas to 4 weeks of ocean acidification [OA, P(CO) = 1800 µatm], at variable water bicarbonate levels, paralleled by changes in water pH. Cardiovascular performance was determined together with extra-(pH) and intracellular pH (pH), oxygen consumption, haemolymph CO parameters, and ion composition. High water P(CO) caused haemolymph P(CO) to rise, but pH and pH remained constant due to increased haemolymph and cellular [HCO]. This process was effective even under reduced seawater pH and bicarbonate concentrations. While extracellular cation concentrations increased throughout, anion levels remained constant or decreased. Despite similar levels of haemolymph pH and ion concentrations under OA, metabolic rates, and haemolymph flow were significantly depressed by 40 and 30%, respectively, when OA was combined with reduced seawater [HCO] and pH. Our findings suggest an influence of water bicarbonate levels on metabolic rates as well as on correlations between blood flow and pH. This previously unknown phenomenon should direct attention to pathways of acid-base regulation and their potential feedback on whole-animal energy demand, in relation with changing seawater carbonate parameters.
海洋酸化导致二氧化碳在海洋生物体内积累，导致酸碱参数发生变化。在呼吸鳃中，酸碱调节涉及通过与周围水的跨膜离子交换，使内部碳酸氢盐水平净增加。成功维持体液 pH 值取决于离子交换机制的功能能力和相关的能量预算。为了详细了解酸碱调节对水参数的依赖关系，我们研究了滨蟹（Carcinus maenas）在 4 周的海洋酸化[OA，P(CO) = 1800 µatm]期间对水碳酸氢盐水平变化的生理反应，同时 pH 值也发生了变化。心血管性能与（pH）和细胞内 pH（pH）、耗氧量、血淋巴 CO 参数以及离子组成一起被测定。高水 P(CO)导致血淋巴 P(CO)升高，但由于血淋巴和细胞内[HCO]的增加，pH 值和 pH 值保持不变。即使在降低的海水 pH 值和碳酸氢盐浓度下，这个过程也是有效的。虽然细胞外阳离子浓度一直在增加，但阴离子水平保持不变或下降。尽管 OA 下血淋巴 pH 值和离子浓度相似，但代谢率和血淋巴流量分别降低了 40%和 30%，当 OA 与降低的海水[HCO]和 pH 值结合时。我们的发现表明，水碳酸氢盐水平对代谢率以及血液流量与 pH 值之间的相关性有影响。这种以前未知的现象应该引起人们对酸碱调节途径及其对与海水碳酸盐参数变化相关的整个动物能量需求的潜在反馈的关注。
