Ocean Acidification: Implications for Respiratory Gas Exchange and Acid-Base Balance in Estuarine Fish

人为的二氧化碳释放正在引起海洋碳酸盐系统（二氧化碳分压、pH值和碱度）发生前所未有的变化，如果目前的趋势继续下去，海洋二氧化碳分压可能在本世纪末之前达到1000µatm。这种预测的海洋化学变化已被证明会以多种方式影响海洋鱼类，从感觉和行为障碍到生长和生存的减少。据估计，这些累积影响将深刻影响全球鱼类种群；然而，要真正理解海洋酸化对种群水平的影响，了解影响个体的潜在生理机制至关重要。呼吸是控制体内二氧化碳分压水平和酸碱状态的关键生理过程，因此在考虑海洋酸化的影响时尤为重要。最近的研究表明，海洋酸化会损害鱼类的二氧化碳排泄，导致代偿性呼吸性酸中毒，并伴有与肠道水分平衡相关的下游生理影响。本研究将重点关注河口红鼓，在先前工作的基础上，继续研究海洋酸化对呼吸和酸碱的影响，以及对环境变化的生理适应潜力。更具体地说，这项工作将研究与海洋酸化的呼吸气体交换和酸碱影响相关的三个特定领域：1)河口鱼类对海洋酸化的通气反应，2)海洋酸化响应中呼吸气体交换途径的适应能力，以及3)酸碱调节的个体发生及其在决定幼虫对海洋酸化敏感性中的作用。这些研究将结合分子生物学、生物化学和整个动物生理学，对内在的综合过程进行深入研究。此外，这项工作不仅将寻求提供海洋酸化的最坏情况，而且还将研究应对这种前所未有的环境变化的生理适应的可能途径。这些研究活动将培养多名本科生和研究生，以及一名博士后研究员。这项工作的发现也将用于各种推广计划，旨在告知公众海洋酸化对鱼类种群的影响。

Anthropogenic carbon dioxide release is causing unprecedented change in the oceanic carbonate system (partial pressure of CO2, pH and alkalinity), and if current trends continue ocean PCO2 could reach 1,000 µatm before the end of the century. This predicted change in ocean chemistry has been shown to impact marine fish in a number of ways, from sensory and behavioral disturbances to reduced growth and survival. These cumulative impacts are estimated to profoundly affect global fish populations; however, to truly comprehend the population level consequences of ocean acidification, it is crucial to understand the underlying physiological mechanisms that impact individuals. Respiration is the key physiological process governing internal PCO2 levels and acid-base status, and therefore is particularly important when considering the impacts of ocean acidification. Recent work has shown ocean acidification to impair CO2 excretion in fish, resulting in a compensated respiratory acidosis with downstream physiological implications related to intestinal water balance. This research will focus on the estuarine red drum to build upon previous work through continued investigation of the respiratory and acid-base consequences of ocean acidification, as well as the potential for physiological adaptations in response to environmental change. More specifically this work will examine three specific areas related to respiratory gas exchange and acid-base implications of ocean acidification: 1) the ventilatory responses to ocean acidification in estuarine fish, 2) the adaptive capacity of respiratory gas exchange pathways in response to ocean acidification, and 3) the ontogeny of acid-base regulation and its role in determining larval sensitivity to ocean acidification. These studies will provide an in-depth examination of an inherently integrative process, using a combination of molecular biology, biochemistry and whole animal physiology. Furthermore, this work will not only seek to provide a worst-case scenario for ocean acidification, but also investigate possible routes of physiological adaptation in response to this unprecedented environmental change. These research activities will train multiple undergraduate and graduate students, as well as one post-doctoral researcher. The findings of this work will also be used in a variety of outreach programs intended to inform the public about the impacts of ocean acidification on fish populations.