Respiratory Acclimation of Marine Fish to Ocean Deoxygenation

包括气候变化在内的人为因素正在增加世界各地海洋中低氧区（即海洋脱氧）的普遍性，这在墨西哥湾北部尤其如此，那里普遍存在较大的季节性最低氧区。沿海水域的缺氧对海洋生物，包括这些地区特有的具有重要经济和生态意义的鱼类具有严重影响。据推测，在这种类型的环境变化下，物种的长期生存部分取决于它们通过改变生理来适应环境的能力，这一概念被称为表型可塑性。该提案将结合分子生物学、生物化学和全动物生理学来探索一种经济上重要的鱼类——红鼓鱼（Sciaenops ocellatus）在长时间暴露于氧气供应减少后提高呼吸氧气吸收量的能力。这项工作的成果将纳入针对K-12学生的公共教育计划。这些努力的目标将是提高青年和一般公众的科学素养，重点是了解海洋健康、气候变化的核心原则，以及健康的海洋和鱼类种群对沿海社区的重要性。此外，将为几名本科生和研究生以及一名博士后提供综合生理学的指导研究培训。本研究的主要目的是探讨具有代表性的海洋鱼类红鼓鱼在长期缺氧环境下呼吸可塑性的生理机制和生态意义。这些暴露将发生在该物种的临界氧气阈值之上，并且将评估红鼓鱼最大限度地增加有氧范围的能力，这将增加重要生态活动的能力。这项工作首先利用基因表达和生物化学技术探索红细胞、心脏和红肌肉的可塑性，然后测量全动物的性能，从而整合了多个组织水平。该项目提出了以下与缺氧暴露有关的假设：1)鱼类将表现出血红蛋白表达模式的改变，与红细胞和血浆可接近的碳酸酐酶升高相一致，这将协同工作以增强心脏和肌肉的氧气卸载；2)心脏和肌肉会减少线粒体质子泄漏，从而产生更多的单位氧能量；3)在机体水平上，驯化将导致游泳性能和有氧范围的增加；4)在生命早期暴露于低氧水平的红鼓将表现出刚性的表型可塑性，从而导致生命后期表型的改变。这项综合评估将为海洋鱼类抵消海洋脱氧对呼吸性能的有害影响的能力提供宝贵的见解。这些活动还将有助于研究生、本科生和博士后的培训，结果将纳入公共教育倡议，重点关注气候变化和海洋脱氧对海洋生物的影响。该奖项由海洋科学地理学部生物海洋学项目和生物学部综合有机体系统生理机制和生物力学项目共同资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Anthropogenic factors, including climate change, are increasing the prevalence of low-oxygen zones in oceans around the world (i.e., ocean deoxygenation), and this is especially true in the northern Gulf of Mexico where large seasonal oxygen minimum zones are common. Deoxygenation of coastal waters has serious implications for marine life, including the economically and ecologically important fish species endemic to these regions. It is hypothesized that the long-term survival of species subjected to this type of environmental change depend in part on their ability to acclimate by altering their physiology, a concept known as phenotypic plasticity. This proposal will use a combination of molecular biology, biochemistry, and whole-animal physiology to explore the ability of an economically important fish species, the red drum (Sciaenops ocellatus), to enhance respiratory oxygen uptake following exposure to prolonged periods of reduced oxygen availability. Results of this work will be incorporated into public education initiatives targeting K-12 students. The goal of these efforts will be to increase the scientific literacy of youth and the general public with an emphasis on understanding the core principles of ocean health, climate change, and the importance of healthy oceans and fish populations for coastal communities. In addition, mentored research training in integrative physiology will be provided for several undergraduate and graduate students and a post-doctoral fellow. The primary objective of this work is to explore the physiological mechanisms and ecological significance of respiratory plasticity in a representative marine fish, the red drum, exposed to prolonged environmental hypoxia. These exposures will occur above the critical oxygen threshold for the species, and the capacity of red drum to maximize aerobic scope, which would increase the capacity for ecologically important activities, will be assessed. This work integrates across multiple levels of organization by first exploring plasticity in the red blood cells, heart and red muscle using gene expression and biochemistry, after which whole-animal performance will be measured. The project addresses the following hypotheses related to hypoxia exposure: 1) fish will exhibit an altered pattern of hemoglobin expression coincident with elevated red blood cell and plasma accessible carbonic anhydrase that will work cooperatively to enhance oxygen offloading in the heart and muscle; 2) the heart and muscle will exhibit reduced mitochondrial proton leak, thereby generating more energy per unit oxygen; 3) acclimation will result in increased swimming performance and aerobic scope at the organismal level; 4) red drum exposed to reduced oxygen levels at early life stages will exhibit rigid phenotypic plasticity that results in altered phenotypes later in life. This comprehensive evaluation will provide invaluable insight into the ability of marine fishes to offset the deleterious effects of ocean deoxygenation on respiratory performance. These activities will also contribute to graduate and undergraduate student and post-doctoral training, and results will be integrated into public education initiatives focused on implications of climate change and ocean deoxygenation on marine life. This award was co-funded by the GEO-Division of Ocean Sciences Biological Oceanography Program and the BIO-Division of Integrative Organismal Systems Physiological Mechanisms and Biomechanics Program.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.