Collaborative Research: A metabolic index to predict the consequences of climate change for midwater ecosystems

随着气候变化，海洋温度预计将上升，这反过来将减少海洋生物的氧气供应，增加新陈代谢氧气需求。调查人员将对各种海洋生物进行船上生理实验，并确定它们在东太平洋氧气最小区域(OMZ)内的环境条件下的分布情况。目标将是模拟和绘制新陈代谢指数(MI)，以预测这些物种的垂直和水平分布在未来世界海洋中可能发生的变化。MI定义为环境供氧量与温度相关需氧量之间的比率。氧气供应既包括栖息地范围内的环境氧气浓度，也包括促进氧气吸收的生物体的生理特征，如鳃和循环系统。因此，MI将把测量的耐受性和低氧环境暴露与环境数据结合起来。研究人员将测量对低氧的耐受性，重点是研究不足的生物体，包括温度和生物体大小的影响。他们将沿着东太平洋加利福尼亚州洋流以南氧气含量的自然梯度进行采样。科学团队和一名录像师将利用基于网络和视频技术开发一个关于深海生物和气候变化的博客。四名研究生将在这个项目上获得资助，结合最近开发的一门远洋生态学课程，几名本科生将有机会参与海洋研究。这项研究填补了对一种基于生理学的测量方法的迫切需求，这种测量方法可以用来预测随着海洋变暖和缺氧区的扩大而变化的海洋群落。现代海洋保护区范围广泛，以深水(300-800米)氧气分压为特征，对大多数海洋生物来说是致命的，但那里存在着蓬勃发展的群落。据预测，气候变化将进一步耗尽氧气。研究人员将对不同海洋物种的新陈代谢指数(MI)进行建模和绘制地图，以帮助预测物种在垂直和水平分布上可能如何在未来整个世界海洋中发生变化。MI将根据已公布和计划的单个物种暴露于的最低环境氧气分压的测量(基于它们在水柱中的分布)和支持常规有氧代谢需求的最低要求(来自船上对个人的呼吸测量)得出氧气供需数据。在东太平洋沿OMZ强度梯度进行的研究巡航期间，调查人员将在船上进行生理测量，以确定未被研究的中浮游动物和胶状类群的代谢需求，并确定不同物种纳入MI的大小和温度依赖关系。垂直分层净采样和现场摄影将识别和描述OMZ独特的群落特征，例如一些OMZ中存在较低的氧跃层生物量峰值，以及垂直迁徙物种的昼夜栖息地深度对氧气的依赖。将使用气候学数据绘制MI图，以测试和生成有关海洋群落对气候变化的反应的假设。在初步分析中，MI表明在MI为~2时存在代谢限制，这可能会限制垂直和水平栖息地范围。

With climate change, ocean temperatures are expected to increase which in turn will reduce oxygen availability and increase metabolic oxygen demand in marine organisms. The investigators will conduct shipboard physiological experiments for various marine organisms and determine their distributions in relation to environmental conditions within an oxygen minimum zone (OMZ) in the Eastern Pacific Ocean. The goal will be to model and map a Metabolic Index (MI) to predict how vertical and horizontal distributions for these species might change throughout the world's oceans in the future. The MI is defined as the ratio between environmental oxygen supply and temperature-dependent oxygen demand. Oxygen supply includes both the environmental oxygen concentration across a habitat range and the physiological features of organisms that facilitate oxygen uptake, such as gills and circulatory systems. Thus, the MI will integrate measured tolerance and environmental exposure to low oxygen with environmental data. The investigators will measure tolerance to low oxygen, focusing on under-studied organisms, including the effect of temperature and organism size. They will sample along a natural gradient in oxygen content south of the California Current in the Eastern Pacific. The science team and a videographer will develop a blog about deep-sea biology and climate change using web-based and video technologies. Four graduate students will be funded on this project, and in conjunction with a recently developed course in pelagic ecology, several undergraduates will have the opportunity to participate in seagoing research.This research fills a critical need for a physiology-based metric that can be used to predict changing marine communities as the oceans warm and hypoxic zones expand. Modern OMZs are extensive and characterized by deep-water (300-800 m) oxygen partial pressures lethal to most marine organisms, yet thriving communities exist there. Climate change is predicted to further deplete oxygen. The investigators will model and map a Metabolic Index (MI) for diverse marine species to help predict how in vertical and horizontal distributions of species may change throughout the world's oceans in the future. The MI will derive oxygen supply and demand data from published and planned measurements of the minimum environmental partial pressure of oxygen to which individual species are exposed (based on their distributions in the water column) and the minimum requirements to support routine aerobic metabolic demand (from shipboard respiration measurements of individuals). During research cruises in the Eastern Pacific along a gradient of OMZ intensity, the investigators will conduct shipboard physiological measurements to determine metabolic demand for understudied mesozooplankton and gelatinous taxa and determine the size- and temperature dependence for diverse species for incorporation into the MI. Vertically-stratified net sampling and in situ photography will identify and characterize unique OMZ community features, such as the lower oxycline biomass peak present in some OMZs and the oxygen-dependence of day and night habitat depths for vertically-migrating species. The MI will be mapped using climatological data to both test and generate hypotheses about the response of oceanic communities to climate change. In preliminary analysis, the MI suggests a metabolic constraint at a MI of ~2 that may act to limit vertical and horizontal habitat ranges.