Stillman Jonathon H, Paganini Adam W
Romberg Tiburon Center, Department of Biology, San Francisco State University, Tiburon, CA 94920, USA Department of Integrative Biology, University of California Berkeley, Berkeley, CA 94709, USA
Romberg Tiburon Center, Department of Biology, San Francisco State University, Tiburon, CA 94920, USA.
J Exp Biol. 2015 Jun;218(Pt 12):1946-55. doi: 10.1242/jeb.115584.
The change in oceanic carbonate chemistry due to increased atmospheric PCO2 has caused pH to decline in marine surface waters, a phenomenon known as ocean acidification (OA). The effects of OA on organisms have been shown to be widespread among diverse taxa from a wide range of habitats. The majority of studies of organismal response to OA are in short-term exposures to future levels of PCO2 . From such studies, much information has been gathered on plastic responses organisms may make in the future that are beneficial or harmful to fitness. Relatively few studies have examined whether organisms can adapt to negative-fitness consequences of plastic responses to OA. We outline major approaches that have been used to study the adaptive potential for organisms to OA, which include comparative studies and experimental evolution. Organisms that inhabit a range of pH environments (e.g. pH gradients at volcanic CO2 seeps or in upwelling zones) have great potential for studies that identify adaptive shifts that have occurred through evolution. Comparative studies have advanced our understanding of adaptation to OA by linking whole-organism responses with cellular mechanisms. Such optimization of function provides a link between genetic variation and adaptive evolution in tuning optimal function of rate-limiting cellular processes in different pH conditions. For example, in experimental evolution studies of organisms with short generation times (e.g. phytoplankton), hundreds of generations of growth under future conditions has resulted in fixed differences in gene expression related to acid-base regulation. However, biochemical mechanisms for adaptive responses to OA have yet to be fully characterized, and are likely to be more complex than simply changes in gene expression or protein modification. Finally, we present a hypothesis regarding an unexplored area for biochemical adaptation to ocean acidification. In this hypothesis, proteins and membranes exposed to the external environment, such as epithelial tissues, may be susceptible to changes in external pH. Such biochemical systems could be adapted to a reduced pH environment by adjustment of weak bonds in an analogous fashion to biochemical adaptation to temperature. Whether such biochemical adaptation to OA exists remains to be discovered.
由于大气中二氧化碳分压（PCO₂）升高导致的海洋碳酸盐化学变化，已致使海洋表层水的pH值下降，这一现象被称为海洋酸化（OA）。海洋酸化对生物的影响已在来自广泛栖息地的不同分类群中广泛显现。大多数关于生物对海洋酸化反应的研究都是短期暴露于未来的二氧化碳分压水平。通过这类研究，已收集到许多关于生物未来可能做出的可塑性反应的信息，这些反应对其适应性可能有益或有害。相对较少的研究探讨了生物是否能够适应对海洋酸化的可塑性反应所带来的负面适应性后果。我们概述了用于研究生物对海洋酸化适应性潜力的主要方法，其中包括比较研究和实验进化。栖息于一系列pH环境中的生物（例如火山二氧化碳渗漏处或上升流区域的pH梯度环境），在识别通过进化发生的适应性变化的研究中具有巨大潜力。比较研究通过将整体生物反应与细胞机制联系起来，增进了我们对适应海洋酸化的理解。这种功能优化在调节不同pH条件下限速细胞过程的最佳功能时，提供了遗传变异与适应性进化之间的联系。例如，在对世代时间较短的生物（如浮游植物）进行的实验进化研究中，在未来条件下数百代的生长导致了与酸碱调节相关的基因表达出现固定差异。然而，对海洋酸化适应性反应的生化机制尚未得到充分表征，并且可能比基因表达或蛋白质修饰的简单变化更为复杂。最后，我们提出了一个关于海洋酸化生化适应未探索领域的假设。在这个假设中，暴露于外部环境的蛋白质和膜，如上皮组织，可能易受外部pH变化的影响。这样的生化系统可能通过以类似于对温度的生化适应方式调整弱键，来适应pH降低的环境。这种对海洋酸化的生化适应是否存在仍有待发现。
