Investigation of the Effects of CACO3 Saturation State & Temperature on the Calcification Rate & Skeletal Properties of Benthic Marine Calcifiers

知识专长：人为造成的大气二氧化碳分压升高增加了海洋的酸度，从而降低了海水中碳酸钙（CaCO 3）的饱和状态。越来越令人担忧的是这些变化对钙化生物形成外壳和骨骼的能力的潜在影响。最近的研究，包括PI Ries和他的同事们对一套底栖海洋钙化物进行的试点工作，涵盖了广泛的分类学，矿物学和生态学范围，表明海洋生物对CO2引起的海洋酸化表现出广泛的钙化反应，包括积极的，消极的，抛物线，阈值和中性反应。海洋钙化者从各种形式（多晶型）的CaCO 3中构建其外壳和骨骼，最常见的是文石，高镁方解石和低镁方解石。这些多晶型物在海水中的溶解度差异很大，因此，它们对CO2引起的海洋酸化的潜在反应也不同。在试点研究中调查的生物体分泌的贝壳的X射线衍射分析表明，方解石（CaCO 3的不太可溶的形式），文石（更可溶的形式）在其壳内的比例增加pCO 2升高，而镁：钙比的方解石下降。这些观察结果表明，一些海洋钙化可能部分适应下降的碳酸钙饱和状态，增加了更大比例的不太可溶的形式的碳酸钙（低镁方解石）的费用更可溶的形式（文石，高镁方解石）。然而，海洋生物的外壳和骨骼的矿物学和成分变化可能会改变其结构和生物力学特性。该项目旨在建立在试点研究的结果，通过饲养一套底栖海洋钙化者在过去（280 ppm），现在（385 ppm）和预测的未来（540，840 ppm）pCO_2和三种不同温度下，研究（1）钙化率和线性延伸率的变化;（2）壳/骨架内各种CaCO 3多晶型物的相对丰度和微米级分布;（3）壳/骨架的超微结构和晶体形态;（4）它们的生物力学性质。该研究还将建立在试点实验的基础上，利用更彻底的重复研究设计，更精确地限制实验海水处理的化学参数，调查3种不同温度制度下的钙化反应，并采用“工业化前”pCO 2水平（280 ppm）。拟议的研究结果应该推进我们的理解，底栖海洋钙化应如何应对未来的CO2引起的海水温度和CaCO 3饱和状态的变化。并通过调查的范围内的大气pCO 2发生自晚古生代的生物体的反应，这项研究应该告知我们的理解的假定联系大气pCO 2，大规模灭绝事件，以及长期变化的多晶型矿物学的海洋钙化在整个地质时期。最后，将观察到的生物对pCO 2-T变化的反应与已经建立的非生物成因碳酸盐的反应进行比较，将促进我们对海洋钙化物构建其外壳和骨骼的机制的理解。拟议研究的结果将为政策制定者和立法者的决策提供信息，这些决策者和立法者致力于通过建立pCO 2-一系列海洋钙化物的T公差。拟议研究的结果将通过同行评审的出版物、会议介绍、公共宣传、PI网站和主流媒体渠道广泛传播。PI Ries是一位早期的职业科学家，他的研究计划将通过研究提供的资源和活动得到实质性的加强。这项研究还将促进研究生Ann Mooney（太平洋岛民）和Isaac韦斯特菲尔德以及博士后研究员Karl Castillo（非洲裔伯利兹人）的教育，培训和专业发展，其中两人属于海洋科学代表性不足的少数群体。最后，建议的研究将创造宝贵的培训和教育经验，为几个本科生进行研究下PI。

INTELLECTUAL MERIT: Anthropogenic elevation of atmospheric pCO2 is increasing the acidity of the oceans, thereby reducing the saturation state of seawater with respect to calcium carbonate (CaCO3). Of mounting concern is the potential impact of these changes on the ability of calcifying organisms to form their shells and skeletons. Recent studies, including pilot work conducted by PI Ries and his colleagues on a suite of benthic marine calcifiers spanning broad taxonomic, mineralogical, and ecological ranges, have revealed that marine organisms exhibit a wide range of calcification responses to CO2-induced ocean acidification, including positive, negative, parabolic, threshold, and neutral responses. Marine calcifiers build their shells and skeletons from various forms (polymorphs) of CaCO3, most commonly aragonite, high-Mg calcite, and low-Mg calcite. These polymorphs differ greatly in their solubility in seawater and, therefore, in their potential response to CO2-induced ocean acidification. X-ray diffraction analysis of shells secreted by the organisms investigated in the pilot study reveals that the proportion of calcite (the less soluble form of CaCO3) to aragonite (the more soluble form) within their shells increases under elevated pCO2, while the Mg:Ca ratio of their calcite declines. These observations suggested that some marine calcifiers may partially adapt to a declining CaCO3 saturation state by accreting a greater proportion of the less-soluble form of CaCO3 (low-Mg calcite) at the expense of the more soluble forms (aragonite, high-Mg calcite). However, it is likely that such mineralogical and compositional changes in the shells and skeletons of marine organisms would alter their structural and biomechanical properties. The project seeks to build upon the results of the pilot study by rearing a suite of benthic marine calcifiers under past (280 ppm), present (385 ppm), and predicted future (540, 840 ppm) pCO2 and under three distinct temperatures to investigate changes in: (1) their rates of calcification and linear extension; (2) the relative abundance and micron-scale distribution of the various CaCO3 polymorphs within their shells/skeletons; (3) the ultrastructure and crystal morphology of their shells/skeletons; and (4) their biomechanical properties. The research would also build upon the pilot experiments by utilizing a more thoroughly replicated study design, by more precisely constraining the chemical parameters of the experimental seawater treatments, by investigating calcification responses under 3 different temperature regimes, and by employing a "pre-industrial" pCO2 level (280 ppm). The results of the proposed research should advance our understanding of how benthic marine calcifiers shall respond to future CO2-induced changes in seawater temperature and CaCO3 saturation state. And by investigating the response of organisms over the range of atmospheric pCO2 that has occurred since late Paleozoic time, this research should inform our understanding of the putative links atmospheric pCO2, mass extinction events, and secular variation in the polymorph mineralogy of marine calcifiers throughout geologic time. Finally, comparison of the observed biological responses to variable pCO2-T scenarios with that already established for abiogenic carbonates will advance our understanding of the very mechanisms by which marine calcifiers build their shells and skeletons.BROADER IMPACTS: The results of the proposed research will inform the decisions of policy makers and legislators working to mitigate the impacts of CO2-induced warming and ocean acidification by establishing pCO2-T tolerances for a range of marine calcifiers. Results of the proposed research would be widely disseminated through peer-reviewed publication, conference presentations, public outreach, the PI's website, and mainstream media outlets. PI Ries is an early career scientist whose developing research program would be materially enhanced by the resources and activities afforded via the research. This research would also promote the education, training, and professional development of graduate students Ann Mooney (a native Pacific Islander) and Isaac Westfield, and postdoctoral fellow Karl Castillo (a native Belizean of African descent), two of whom belong to minority groups that are underrepresented in the marine sciences. Finally, the proposed research would create valuable training and educational experiences for several undergraduates conducting research under the PI.