OCE-PRF: Impacts of endolithic microbial sulfur cycling on coral holobiont ecophysiology, biomineralization, and geochemistry

造礁珊瑚构成骨骼，建造整个珊瑚礁生态系统所依赖的复杂结构。一组不同的微生物，被称为内石层，生活在珊瑚骨架中，与珊瑚宿主非常接近。这些石器内微生物中的一些可以通过改变pH和碱度来影响珊瑚的钙化，也可能为珊瑚宿主提供营养。然而，人们对栖息在珊瑚骨架上的微生物知之甚少。我们对珊瑚内石层的有限了解在我们对珊瑚生理学的理解上留下了很大的差距。如果没有对珊瑚生理学的充分了解，就很难预测珊瑚及其创造的结构将如何应对气候变化。这项工作将调查珊瑚骨骼中微生物的多样性和活动，重点是可能影响珊瑚钙化的微生物。此外，由于珊瑚骨架经常被用来重建过去的气候，这项工作将确定这些微生物如何影响珊瑚骨架的化学特征和气候代理解释。通过海洋生物实验室的研究计划，高中生和本科生将参与实验室分析和水族馆实验。结果和产品将在开放获取出版物、开放获取数据和代码储存库以及通过地方和国家(虚拟)公共外联活动共享。通过提高我们对珊瑚骨骼中微生物多样性和活动的了解，这项研究将提高我们对珊瑚如何响应环境变化的理解，使我们能够更好地保护珊瑚礁生态系统及其提供的重要经济服务。尽管对珊瑚生物学和生物矿化的研究已有数十年，但许多珊瑚生长和生理的基本机制仍然在文献中存在争议，包括生物学在珊瑚钙化中的作用。众所周知，珊瑚生物影响钙化，骨骼微生物群落可能在珊瑚内的钙化、生物侵蚀和营养循环中发挥作用。通过结合微生物生理学、生物地球化学和地球化学技术，本研究将采取综合和跨学科的方法来了解珊瑚骨骼微生物群落及其对珊瑚生理和钙化的影响。将测量珊瑚骨骼中的微生物硫循环速率，并通过扩增和元基因组测序相结合的方法进行分类鉴定。关键的微生物分类群将使用荧光原位杂交和共聚焦显微镜进行定位。将特别关注骨骼内特定官能团的空间分布，包括执行缺氧光合作用和硫酸盐还原的类群，这两个已知的途径会影响pH和碱度。微传感器和同位素示踪实验将被用来量化微生物的活动，以及任何可能的营养在内岩层之间或从内岩层到珊瑚组织的转移。在限制了这些微生物的多样性、分布和活动之后，包含已知的石器时代群落的珊瑚骨骼的地球化学特征将被用来研究内岩对珊瑚古气候指标的影响。这项工作可以通过限制内岩层驱动的pH、碱度和碳循环的变化如何改变钙化和骨骼地球化学，来开发新的环境指标或现有指标的校正系数。通过提供对珊瑚石器时代微生物的更深入和更全面的了解，这项工作的发现将提高我们对珊瑚及其创造结构、循环营养物质和支持生态和经济关键生态系统的能力的理解，以及我们对适应极端栖息地的微生物的理解。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Reef-building corals construct skeletons and build complex structures upon which entire reef ecosystems depend. A diverse group of microbes, known as endoliths, live in coral skeletons and are in close proximity to the coral host. Some of these endolithic microbes could influence coral calcification, by changing pH and alkalinity, and may also provide nutrients to the coral host. However, little is known about the microbes inhabiting coral skeletons. Our limited knowledge about coral endoliths leaves a large gap in our understanding of coral physiology. Without a full understanding of coral physiology, it is difficult to make predictions of how corals and the structure they create will respond to climate change. This work will investigate diversity and activity of microbes in coral skeletons, with a focus on microbes that could affect coral calcification. In addition, as coral skeletons are often used to reconstruct past climate, this work will determine how these microbes impact the chemical signatures of coral skeletons and climate proxy interpretation. Through research programs at the Marine Biological Laboratory, high school and undergraduate level students will be involved in laboratory analysis and aquarium-based experiments. Findings and products will be shared in open-access publications, open-access data and code repositories, and through local and national (virtual) public outreach events. By improving our understanding of microbial diversity and activity in coral skeletons, this research will improve our understanding how corals will respond to environmental change, allowing us to better preserve coral reef ecosystems and the important economic services that they provide.Despite decades of research on coral biology and biomineralization, many basic mechanisms of coral growth and physiology remain debated in the literature, including the role of biology in coral calcification. Coral biology is known to affect calcification, and the skeletal microbial community likely plays a role in calcification, bioerosion, and nutrient cycling within the coral. By combining microbial physiology, biogeochemistry, and geochemistry techniques, this research will take an integrative and interdisciplinary approach towards understanding the coral skeletal microbial community and its influence on coral physiology and calcification. Microbial sulfur cycling rates in coral skeletons will be measured and paired with taxonomic identification through a combination of amplicon and metagenomic sequencing approaches. Key microbial taxa will be localized using fluorescence in situ hybridization and confocal microscopy. Particular focus will be given to the spatial distribution of specific functional groups within the skeleton, including taxa performing anoxygenic photosynthesis and sulfate reduction, two pathways known to affect pH and alkalinity. Microsensor and isotope tracer experiments will be used to quantify microbial activity, as well as any potential transfer of nutrients between endoliths or from endoliths to the coral tissue. After constraining the diversity, distribution, and activity of these microbes, geochemical signatures of coral skeletons containing known endolithic communities will be used to study the effect of endoliths on coral paleoclimate proxies. This work could lead to the development of new environmental proxies or correction factors for existing proxies, by constraining how endolith-driven changes in pH, alkalinity, and carbon cycling alter calcification and skeletal geochemistry. By providing a deeper and more holistic understanding of coral endolithic microbes, findings from this work will improve our understanding of corals and their ability to create structure, recycle nutrients, and support ecologically and economically critical ecosystems, as well as our understanding of microbes adapted to extreme habitats.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.