Collaborative Research: Metabolic habitat barriers imposed on tropical diel vertical migrators

该项目旨在为面临不断变化的海洋条件的动物定义生理上可接近的栖息地。许多海洋动物每天从夜间温暖、含氧的表层水域迁移到白天寒冷、缺氧的深层水域，这种迁移在海洋生态和生物地球化学循环中起着至关重要的作用。在它们的深度范围内，迁徙者面临着非常不同的生态和环境需求，这可能导致独特的特征，进而影响它们对海洋变暖的反应，在海洋中，氧气最低带也在扩大。在加利福尼亚湾的两次探险中，这项研究结合了生态学和生理学的方法。研究人员正在测量多种海洋动物的代谢特征，这些动物表现出垂直迁移，以确定氧气和温度在引发垂直和纬度分布变化中的可能作用。他们还测量了物种分布与环境氧气和温度的关系，以确定与生态有关的环境耐受阈值。该项目包括对研究生和本科生的培训和体验式学习。此外，与教育专家和艺术家的接触将产生媒体和课程计划，以支持STEM教育和下一代科学标准。这些活动利用了百慕大海洋科学研究所的数据库和中大西洋机器人教育（MARINE）项目，旨在提高海洋素养和技术流畅性，并针对传统上在科学领域代表性不足的群体的学生。项目产品还包括一个视频游戏的新关卡，介绍了氧气最低区域如何影响动物分布的概念。气候变化正在推动海洋动物的分布向极地转移。这些物种栖息地范围的移动边缘通常被解释为氧气限制的表现，这是由于生理氧气供应和热力学驱动的氧气需求之间的不匹配而在高水温下发生的。然而，研究人员最近的工作表明，氧气供应已经进化到满足需求，而与温度无关。这些相反的观点预测了范围扩张的不同热阈值。在这项研究中，研究人员利用代谢特征之间的关系来推断热带diel垂直迁徙者独特的温度敏感性，并绘制出它们在东太平洋的代谢可用栖息地。具体来说，研究人员提出，氧气供应并不限制热带候鸟的新陈代谢，即使在氧气最少的区域也是如此。相反，他们认为，热带洄游动物的活跃代谢率对温度高度敏感，这对它们的活动范围扩大造成了障碍，因为在寒冷的水域中，生长和繁殖的有氧环境不足。这种温度敏感性也将允许候鸟在温和变暖后向极地扩展到新的栖息地，而不是简单地因过度变暖而从其原生的热带栖息地灭绝。这一假设如果得到支持，将改变我们对物种对气候变化反应的机制理解，修正我们对范围扩大的预测，并修改我们对未来变暖海洋中迁徙动物对海洋生物地球化学循环贡献的评估。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。

This project is seeking to define physiologically-accessible habitat for animals faced with changing ocean conditions. Many oceanic animals migrate daily from warm, oxygenated surface waters at night to deep, cold and hypoxic waters during the daytime, and these migrations play critical roles in oceanic ecology and biogeochemical cycles. Over their depth ranges, migrators face very different ecological and environmental demands that may lead to unique traits that in turn, influence how they respond to a warming ocean where oxygen minimum zones are also expanding. This study is combining ecological and physiological approaches during two expeditions to the Gulf of California. The investigators are measuring metabolic traits in a diverse suite of ocean animals that exhibit vertical migration to determine possible roles of oxygen and temperature in triggering changes in vertical and latitudinal distribution. They are also measuring species distributions in relation to environmental oxygen and temperature to determine ecologically-relevant thresholds of environmental tolerance. The project involves training and experiential learning for graduate and undergraduate students. In addition, engagement with educational experts and artists will generate media and lesson plans to support STEM education and Next Generation Science Standards. These activities leverage the Bermuda Institute of Ocean Sciences’ Databytes and Mid-Atlantic Robotics IN Education (MARINE) programs, designed to improve ocean literacy and technological fluency and targeting students from groups traditionally underrepresented in science. Project products also include a new level for a video game that introduces the concepts of how oxygen minimum zones influence animal distribution.Climate change is driving poleward shifts in the distributions of marine animals. These shifting edges of the range of species habitats are often interpreted as a manifestation of oxygen limitation that is presumed to occur at high water temperatures due to a mismatch between physiological oxygen supply and thermodynamically-driven oxygen demand. However, recent work by the investigators suggests that oxygen supply has evolved to meet demand regardless of temperature. These opposing views predict very different thermal thresholds for range expansion. In this study, the investigators are employing a relationship between metabolic traits to infer a unique temperature sensitivity in tropical diel vertical migrators and to map their metabolically-available habitat in the Eastern Pacific. Specifically, the investigators propose that oxygen supply does not limit metabolism in tropical migrators, even in the oxygen minimum zone. Instead, they contend that the active metabolic rate for tropical migrators is highly sensitive to temperature, and that this creates a barrier to range expansion where the aerobic scope for growth and reproduction is insufficient in cold waters. This temperature sensitivity will also allow migrators to expand poleward to newly available habitat following modest warming, rather than simply being extirpated from their native tropical habitat by excess warming. This hypothesis, if supported, would transform our mechanistic understanding of species’ responses to climate change, amend our predictions of range expansion, and modify our assessment of migrator contributions to oceanic biogeochemical cycles in a warmer future ocean.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.