Collaborative Research: Experimental Investigations of Coral Biomineralization: Understanding the Biomineralization Response to Ocean Acidification

地球大气中二氧化碳（CO2）浓度的上升正在改变海洋的碳酸盐化学。模型表明，随着二氧化碳水平在下一个世纪继续上升，地表水碳酸盐离子浓度可能会下降近50%，相对于工业化前的水平。在实验室研究中，海洋钙化生物的多个分类群对海水碳酸盐浓度的变化表现出高度的敏感性。石珊瑚的反应特别有据可查：在受控的实验条件下，珊瑚钙化率随着海水碳酸盐离子浓度的降低而明显下降。 这些观测结果对珊瑚礁生态系统在全球变化中的健康和生存能力具有重大影响。然而，由于我们对珊瑚钙化的基本机制知之甚少，对珊瑚钙化对下世纪海水饱和状态变化的预测是有限的。例如，钙化对外部碳酸盐离子浓度变化的敏感性令人困惑，考虑到目前的珊瑚生物矿化模型。为了回答这个难题，来自迈阿密大学伍兹霍尔海洋研究所和罗森斯蒂尔海洋与大气科学学院的科学家们将解决两个关键问题：（1）晶体生长发生的内部钙化流体的饱和状态是什么，以及它如何响应外部海水碳酸盐浓度的变化？ (2)珊瑚钙化对海水碳酸盐的敏感性是否与藻类共生体有关？他们还将测试文石成核的假设，由蛋白质催化，并发生在附近的环境饱和度水平，是在珊瑚矿化周期的pH值敏感的步骤。研究人员将进行一系列实验室降水和珊瑚培养实验，旨在增加我们对珊瑚如何钙化的了解，并为预测珊瑚对海洋酸化的反应奠定基础。 他们将利用微米和纳米级晶体形态，以及由虫黄藻和偶氮黄藻珊瑚所附着的文石晶体的地球化学特征，来解释钙化空间内的条件。在更广泛的影响中，跨学科研究将通过阐明珊瑚礁形成的基本机制以及未来气候变化对具有巨大经济和科学重要性的生态系统的潜在影响而造福社会。 他们的发现也将对解释珊瑚和其他生物骨骼中的稳定同位素替代物（d18O，d11B）产生更广泛的影响。 PI还将指导学生并继续其广泛的推广计划

Rising concentrations of carbon dioxide (CO2) in Earth's atmosphere are changing the carbonate chemistry of the ocean. Models indicate that as CO2 levels continue to rise over the next century, surface water carbonate ion concentration may decrease by almost 50% relative to pre-industrial levels. In laboratory studies, multiple taxa of marine calcifying organisms exhibit high sensitivity to changes in seawater carbonate concentration. The response of scleractinian corals is particularly well documented: under controlled experimental conditions, coral calcification rates show a measurable decline with decreasing seawater carbonate ion concentration. These observations have significant implications for the health and survivability of coral reef ecosystems in the face of global change. Predictions of the response of coral calcification to changes in seawater saturation state expected over the next century are limited however, by how little we know of the fundamental mechanisms of coral calcification. For instance, that calcification displays any sensitivity at all to changes in external carbonate ion concentration is puzzling, given current models of coral biomineralization. To answer this puzzle, scientists from Woods Hole Oceanographic Institution and Rosenstiel School of Marine and Atmospheric Science at the University of Miami will address two key questions: (1) What is the saturation state(s) of the internal calcifying fluid in which crystal growth occurs and how does it respond to changes in external seawater concentrations of carbonate? (2) Are algal symbionts implicated in the sensitivity of coral calcification to seawater carbonate? They will also tests the hypothesis that aragonite nucleation, catalyzed by proteins, and occurring at near ambient saturation levels, is the pH-sensitive step in the coral mineralization cycle. The PIs will conduct a series of laboratory precipitation and coral culturing experiments designed to increase our understanding of how corals calcify, and to lay the groundwork for predictions of the coral response to ocean acidification. They will utilize micro- and nanoscale crystal morphology, and geochemical signatures of aragonite crystals accreted by zooxanthellate and azooxanthellate corals, to interpret conditions within the calcifying space. Among the broader impacts, the interdisciplinary research will benefit society by elucidating the fundamental mechanisms by which coral reefs are built and the potential impacts of future climate changes on ecosystems of enormous economic and scientific importance. Their findings also will have broader implications for interpretation of stable isotope proxies (d18O, d11B) in coral and other biogenic skeletons. The PIs will also mentor students and continue their extensive outreach programs