NSFOCE-BSF: Collaborative Research: The Role and Mechanisms of Nuclei-induced Calcium Carbonate Precipitation in the Coastal Carbon Cycle: A First In-depth Study

海水中碳酸钙(CaCO3)的形成是海洋碳循环的基本途径。碳酸钙的形成可通过生物生产(建造贝壳或骨骼材料的有机体的钙化)或非生物(非生物或化学)过程发生。尽管开阔水域和沿海水域的大多数表层海水都是碳酸钙过饱和的，但有几个因素抑制了碳酸钙的非生物生产。因此，目前的范式是，海水中碳酸钙的形成大多是生物形成的。然而，实验室实验已经证明，在过饱和海水中添加固相颗粒可以促进核诱导的碳酸钙沉淀(NICP)，因为它为沉淀提供了“种子”。在富含CaCO3的沉积物重新悬浮期间，小巴哈马群岛显示了NICP。直到最近，基本上没有证据表明，在悬浮粒子的CaCO3含量相对较低的典型海洋系统中会出现NICP。参与该项目的以色列合作伙伴最近的一项研究提供了证据，表明由于山洪暴发和潜在的空气扬尘造成的颗粒物的涌入，NICP可能在红海的碳预算中发挥重要作用。这一发现表明，NICP可能是海洋碳循环中被忽视的一条重要的CaCO3形成途径。该项目的目标是进行第一次全面、深入的研究，以评估国家海洋方案在海洋中的意义。该项目是美国和以色列科学家之间的国际合作，由美国国家科学基金会和美国-以色列双国科学基金会共同资助。一名博士后研究员，其博士工作构成了这项研究的基础，将通过该项目得到支持。该项目将为一名以色列硕士研究生和一名美国少数民族本科生实习生提供建议和培训。该项目将使用一种综合方法来评估可能导致NICP的不同机制，包括河流沉积物输入、通过山洪暴发的陆源颗粒输入、海底沉积物再悬浮和大气粉尘输入。实地调查将在一套沿海环境中进行：红海北部、密西西比河和萨宾河羽流以及墨西哥湾北部的加尔维斯顿湾，每一处都有大量富含非碳酸盐的沉积物。调查人员还将进行受控实验室实验，以核实和扩大实地观察。如果NICP被证明是重要的，这一发现可能会促进对碳循环重要部分的重新审查，以及海洋碳系统对持续扰动的反应。

The formation of calcium carbonate (CaCO3) in seawater is a fundamental pathway in the marine carbon cycle. Calcium carbonate formation may occur through biological production (calcification by organisms building shells or skeletal material) or through non-biological (abiotic, or chemical) processes. Although most surface seawater in both open and coastal waters is supersaturated in calcium carbonate, several factors inhibit the abiotic production of calcium carbonate. Therefore the current paradigm is that most calcium carbonate formation in seawater is biological. However, laboratory experiments have demonstrated that addition of solid-phase particles to supersaturated seawater promotes nuclei-induced CaCO3 precipitation (NICP) by providing "seeds" for precipitation. NICP has been demonstrated in the Little Bahama Banks during events of re-suspension of CaCO3-rich sediments. Until very recently, essentially no evidence has shown that NICP occurs in typical marine systems where suspended particles have relatively low CaCO3 content. A recent study by the Israeli partners in this project provides evidence that NICP may play a significant role in the carbon budget in the Red Sea, as a result of an influx of particulate material caused by flash floods and potentially airborne dusts. Such a finding suggests that NICP may be an important CaCO3 formation pathway that has been mostly ignored in the ocean carbon cycle. The goal of this project is to conduct the first comprehensive, in-depth study to evaluate the significance of NICP in the oceans. The project is an international collaboration between U.S. and Israeli scientists, jointly funded by NSF and the U.S.-Israel Binational Science Foundation. A postdoctoral researcher whose Ph.D. work forms the foundation for this study will be supported through this project. An Israeli masters-level student and one U.S. minority undergraduate intern will be advised and trained in this project.The project will use an integrated approach to assess different mechanisms that may result in NICP, including riverine sediment input, land-derived particle influx via flash floods, bottom sediment resuspension, and atmospheric dust input. Field investigations will be done in a suite of coastal environments: the northern Red Sea, the Mississippi and Sabine River plumes and Galveston Bay in the northern Gulf of Mexico, each of which receive significant quantities of non-carbonate rich sediments. The investigators will also conduct controlled laboratory experiments to verify and extend field observations. If NICP is shown to be significant, this finding could promote a reexamination of important parts of the carbon cycle and the response of the ocean carbon system to ongoing perturbations.