Drivers of coral and reef-scale calcification in the North Atlantic

全世界数以百万计的人依赖珊瑚礁提供的生态系统服务，包括提供营养、捕鱼、旅游以及抵御风暴和海浪。这些服务的基础是基于珊瑚礁保持碳酸钙正向增加的基本原则，这是由珊瑚和其他海洋钙化物产生的碳酸钙促进的。在过去的几十年里，世界上许多珊瑚礁系统的珊瑚礁碳酸钙产量下降，主要是由于珊瑚白化、珊瑚疾病和水质差。目前的预测表明，由于未来海洋变暖和酸化，这种产量将继续下降。然而，我们对环境参数如何控制珊瑚和珊瑚礁尺度的原地钙化率的了解并不完整，并且限制了我们对珊瑚和珊瑚礁尺度碳酸钙生产过去和未来变化的潜在机制的理解。因此，这里提出的研究旨在量化珊瑚钙化率，通过对在百慕大收集的珊瑚核的图像分析确定，作为环境参数在空间和时间上的函数是如何变化的。这种分析之所以成为可能，是因为马尾藻海近海和收集珊瑚芯的近岸地区存在物理和化学参数的时间序列数据集。这些数据的结合将为珊瑚和珊瑚礁尺度钙化的环境控制提供新的见解。此外，调查人员将与圣地亚哥海洋发现研究所（ODI）一起参与教育领域和课堂活动。ODI的使命是通过对海洋和自然的科学探索，吸引、教育和激励来自不同背景的年轻人，并特别与来自服务欠缺社区的学生合作。这里进行的研究旨在了解珊瑚和珊瑚礁尺度钙化的不同环境驱动因素在季节到年际时间尺度上的相对重要性。为了实现这一目标，研究人员将利用计算机断层扫描（CT）技术，在百慕大珊瑚礁平台的五个不同地点，对从三种不同物种（迷路双孔虫、糙棘假双孔虫和franbicella）中提取的42个珊瑚芯的骨骼密度、延伸和钙化率进行表征。珊瑚骨骼参数的季节性测量将与每月原位分解的海水物理-生物地球化学参数的独特十年时间序列相结合进行分析。研究人员还将对珊瑚骨架进行稳定同位素和痕量金属地球化学分析（18O, 13C, Sr/Ca, Cd/Ca），以评估和构建珊瑚岩心持续时间内环境条件的额外代理记录。珊瑚生长、环境和地球化学数据集的结合提供了一个前所未有的机会来评估不同环境驱动因素对珊瑚和珊瑚礁尺度钙化率的相对重要性，以及沿近海梯度、季节性和年际时间尺度上三种主要珊瑚物种之间的钙化率。目前还没有这样的其他数据集存在，拟议的研究在几个领域具有促进科学进步的强大潜力。珊瑚钙化记录与地球化学代用物和每月的海水生物地球化学原位数据相结合，将有助于阐明珊瑚钙化与其环境驱动因素之间的因果关系，包括与北大西洋涛动有关的年际变率。此外，在约束良好的环境数据背景下，对痕量金属和同位素代用物的评价和验证有可能极大地帮助珊瑚古海洋学界对过去的环境条件进行更可靠的重建。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。

Millions of people around the world are dependent on the ecosystem services provided by coral reefs, which include the provision of nutrition, fishing, tourism, and protection from storms and waves. The foundation for these services is based on the basic principle that coral reefs maintain positive calcium carbonate accretion, which is facilitated by the production of calcium carbonate by corals and other marine calcifiers. For the past several decades, coral reef calcium carbonate production has declined in many reef systems throughout the world primarily due to coral bleaching, coral disease, and poor water quality. Current projections suggest that this production will continue to decline in response to future ocean warming and acidification. However, our knowledge of how environmental parameters control coral and reef-scale calcification rates in situ is not complete and limits our understanding of the underlying mechanisms for past and future changes in coral and reef-scale calcium carbonate production. Thus, the research proposed here seeks to quantify how coral calcification rates, determined from image analysis of coral cores collected in Bermuda, have varied as a function of environmental parameters across space and time. This analysis is made possible by the existence of time-series datasets of physical and chemical parameters offshore in the Sargasso Sea and inshore where the coral cores were collected. The combination of data will offer new insights to the environmental controls of coral and reef-scale calcification. Furthermore, the investigators will engage in educational field and classroom activities with Ocean Discovery Institute (ODI) in San Diego. ODI's mission is to engage, educate, and inspire youth from diverse backgrounds through scientific explorations of the ocean and nature, and specifically work with students from underserved communities. The research to be conducted here seeks to understand the relative importance of different environmental drivers of coral and reef-scale calcification on seasonal to interannual timescales. To accomplish this, the investigators will characterize the skeletal density, extension, and calcification rates of 42 coral cores extracted from three different species (Diploria labyrinthiformis, Pseudodiploria strigosa and Orbicella franksi) at five different sites from the Bermuda coral reef platform using computed tomography (CT) scanning techniques. Seasonal measurements of coral skeletal parameters will be analyzed in conjunction with a unique decadal time series of monthly resolved in situ seawater physical-biogeochemical parameters. The investigators will also conduct stable isotope and trace metal geochemical analyses (18O, 13C, Sr/Ca, Cd/Ca) of the coral skeleton to evaluate and construct additional proxy records of environmental conditions for the duration of the coral cores. This combination of coral growth, environmental, and geochemical datasets provides an unprecedented opportunity to evaluate the relative importance of different environmental drivers on coral and reef-scale calcification rates between three dominant coral species along inshore-offshore gradients and over seasonal and interannual timescales. No such other datasets currently exist and the proposed research has strong potential to contribute to scientific advancement in several areas. The coral calcification record coupled with the geochemical proxies and the monthly in situ seawater biogeochemistry data will help to elucidate causal links between coral calcification and its environmental drivers, including interannual variability linked to the North Atlantic Oscillation. In addition, evaluation and validation of the trace metals and isotopic proxies in the context of the well-constrained environmental data have the potential to greatly assist the coral paleoceanography community in generating more robust reconstructions of past environmental conditions.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.