Ocean Acidification-Category 1: Collaborative Research: An Investigation of the Role of Nutrition in the Coral Calcification Response to Ocean Acidification

知识价值：在本世纪的过程中，所有热带珊瑚礁生态系统，无论是在人口密集的海岸线边缘还是在偏远的岛屿和环礁上，都面临着大气中二氧化碳水平上升造成的海洋酸化的前所未有的威胁。在迄今为止进行的许多实验室实验中，硬核珊瑚（石质）的碳酸钙产量（钙化）与海水饱和状态omega - aar呈负相关，无论omega - aar是由酸还是二氧化碳添加来控制的。根据这些数据，预测到本世纪末，珊瑚钙化率可能会下降到现代数值的80%。然而，越来越多的新实验数据表明，珊瑚钙化对海洋酸化的反应可能比以前认识到的更不直接，也更多变。在最近的至少10项实验中，包括我们自己的实验，8种不同的热带和温带物种在营养充足但显著升高的CO2条件下（780-1200 ppm, OMEAGar ~1.5-2），继续以与环境CO2下饲养的同种动物相当的速度钙化。这些实验结果与在东太平洋和阿曼南部的珊瑚礁上收集的初步现场数据一致，在这些珊瑚礁上，今天的珊瑚在相当于工业化前二氧化碳浓度2倍和3倍的条件下生活和积累骨骼。在这些高二氧化碳、高营养的珊瑚礁上（硝酸盐浓度通常超过2.5微摩尔），珊瑚的生长速度与低二氧化碳、少营养珊瑚礁环境中的同种珊瑚的生长速度相当，有时甚至超过。研究人员提出，珊瑚的能量状态与无机营养物质和/或食物的可用性密切相关，是二氧化碳引起的海洋酸化导致钙化反应的关键因素。他们的假设，如果得到这里提出的实验室和实地调查的证实，意味着在本世纪的过程中，由于气候对海洋分层的影响和沿海地区人类活动的增加，沿海和开阔海洋营养物质浓度的预测变化可能在加剧和在某些地区调节珊瑚礁对海洋酸化的反应方面发挥关键作用。这项研究计划建立在调查人员的初步结果和观察的基础上。这个结合了实验室和现场的项目将检验以下假设：珊瑚钙化对海洋酸化的反应与珊瑚宿主的能量状态有关。共生光合作用和异养摄食对珊瑚能量状态的相对贡献因物种而异。在高CO2环境下饲养的珊瑚，通过用无机营养物刺激光合作用或通过宿主的直接异养喂养来增强其能量状态，可降低钙化对海水OMEGAar减少的敏感性。2. 存在一个物种特有的二氧化碳阈值，超过这个阈值，增强的能量状态就不能再补偿外部海水中omega - aar的减少。同样，我们将测试这样一个假设，即存在一个营养阈值，超过这个阈值，即使在高二氧化碳条件下，营养物质也会对钙化有害。3. 温度引起的共生藻类减少是一种压力源，可以减少珊瑚宿主的能量储备，加剧海洋酸化的钙化反应。4. 如今，海洋酸化对钙化反应的营养调节已经在珊瑚礁上发生，这使得天然高OMEGA/低营养珊瑚礁上的珊瑚与天然低OMEGA/高营养条件下的珊瑚生长速度一样快。更广泛的影响：研究者的初步发现强调了能量状态在珊瑚钙化对海洋酸化反应中的关键重要性。在实验室和自然现场验证这些发现，并确定一系列物种的营养物质和二氧化碳阈值，将对高二氧化碳世界中珊瑚礁恢复能力的预测产生直接影响。我们的项目汇集了珊瑚生物地球化学、化学海洋学、分子生物学和珊瑚生殖生态学方面的各种专业知识，专注于一个具有巨大社会、经济和保护意义的问题。除了支持4个pi的实验室外，它还通过普林斯顿- bios学生暑期实习计划资助一名研究生研究员、一名博士后研究员和本科生培训。所有研究都将在国家和国际会议和讲习班上提出，并通过生物和化学海洋学数据管理处的出版物和档案及时散发数据。

Intellectual Merit: Over the course of this century, all tropical coral reef ecosystems, whether fringing heavily populated coastlines or lining remote islands and atolls, face unprecedented threat from ocean acidification caused by rising levels of atmospheric CO2. In many laboratory experiments conducted to date, calcium carbonate production (calcification) by scleractinian (stony) corals showed an inverse correlation to seawater saturation state OMEGAar), whether OMEGAar was manipulated by acid or CO2 addition. Based on these data, it is predicted that coral calcification rates could decline by up to 80% of modern values by the end of this century. A growing body of new experimental data however, suggests that the coral calcification response to ocean acidification may be less straightforward and a lot more variable than previously recognized. In at least 10 recent experiments including our own, 8 different tropical and temperate species reared under nutritionally-replete but significantly elevated CO2 conditions (780-1200 ppm, OMEAGar ~1.5-2), continued to calcify at rates comparable to conspecifics reared under ambient CO2. These experimental results are consistent with initial field data collected on reefs in the eastern Pacific and southern Oman, where corals today live and accrete their skeletons under conditions equivalent to 2X and 3X pre-industrial CO2. On these high CO2, high nutrient reefs (where nitrate concentrations typically exceed 2.5 micro-molar), coral growth rates rival, and sometimes even exceed, those of conspecifics in low CO2, oligotrophic reef environments.The investigators propose that a coral's energetic status, tightly coupled to the availability of inorganic nutrients and/or food, is a key factor in the calcification response to CO2-induced ocean acidification. Their hypothesis, if confirmed by the laboratory and field investigations proposed here, implies that predicted changes in coastal and open ocean nutrient concentrations over the course of this century, driven by both climate impacts on ocean stratification and by increased human activity in coastal regions, could play a critical role in exacerbating and in some areas, modulating the coral reef response to ocean acidification. This research program builds on the investigators initial results and observations. This combined laboratory and field program will test the hypothesis that: 1. The coral calcification response to ocean acidification is linked to the energetic status of the coral host. The relative contribution of symbiont photosynthesis and heterotrophic feeding to a coral's energetic status varies amongst species. Enhancing the energetic status of corals reared under high CO2, either by stimulating photosynthesis with inorganic nutrients or by direct heterotrophic feeding of the host lowers the sensitivity of calcification to decreased seawater OMEGAar. 2. A species-specific threshold CO2 level exists over which enhanced energetic status can no longer compensate for decreased OMEGAar of the external seawater. Similarly, we will test the hypothesis that a nutrient threshold exists over which nutrients become detrimental for calcification even under high CO2 conditions. 3. Temperature-induced reduction of algal symbionts is one stressor that can reduce the energetic reserve of the coral host and exacerbate the calcification response to ocean acidification. 4. Nutrient modulation of the calcification response to ocean acidification already occurs on reefs today and enables corals on naturally high OMEGA/low nutrient reefs to grow as fast as conspecifics on reefs with naturally low OMEGA/high nutrient conditions.Broader Impacts: The investigator's initial findings highlight the critical importance of energetic status in the coral calcification response to ocean acidification. Verification of these findings in the laboratory and at natural field sites, and identification of nutrient and CO2thresholds for a range of species will have immediate, direct impact on predictions of reef resilience in a high CO2 world. Our project brings together a diverse group of expertise in coral biogeochemistry, chemical oceanography, molecular biology and coral reproductive ecology to focus on a problem that has enormous societal, economic and conservation relevance. In addition to supporting the labs of 4 PIs, it funds a graduate research fellow, a post-doctoral investigator and undergraduate training through the Princeton-BIOS Student Summer Internship Program. All research will be presented at national and international meetings and workshops and data disseminated in a timely manner through publications and archiving in the Biological and Chemical Oceanographic Data Management office.