Coupling of carbonate cycling and redox reactions in the bioturbated zone of marine sediments

沉积物的顶部一米被称为生物扰动带，受到海底发生的各种生物活动的影响。海洋动物，如蠕虫或植物状生物，通常分别在沉积物中挖洞和挖洞，或在沉积物中生根。正因为如此，生物扰动带是一个深水和表层沉积物不断交换的区域。海床上每一厘米的沉积物与它上面和下面的沉积物都有独特的化学性质，但在生物扰动区，海洋动物的活动混合了这些层。通常，海洋学家希望研究海洋过去的化学性质，就会使用沉积物的化学性质，因为如果知道一厘米的沉积物沉积在海底的速度，那么在一定深度的一块沉积物就对应着过去的某个时间；然而，在生物扰动带，这是不可能的，因为非常古老的（深层）沉积物可能被海洋动物向上转移，与新沉积的（浅层）沉积物混合。正因为如此，在过去的海洋化学研究中，生物扰动带的研究较少，而且通常被忽视，这意味着过去几十年海洋过程的信息很少，如果有的话。该项目的研究人员计划通过实地测量、进行实验室实验和开发新的传感器技术来改变这一现状，以提高我们对生物扰动带对沉积物化学影响的理解。对于那些希望了解近50年来海洋化学的化学海洋学家和地质学家来说，这将是一个重大的进步。此外，这些研究人员开发的传感器将成为海洋学家的一个奇妙的新工具，这些研究人员还致力于通过指导来自各种不同背景的学生来支持扩大海洋科学的参与。来自纽约州立大学石溪分校的科学家们建议提高海洋学家的技术能力和模拟生物扰动区内氧化还原和酸碱反应的能力。他们计划确定生物扰动对碳酸盐矿物溶解、沉淀和埋藏的影响，并确定沉积物-水界面的净碱度通量。在过去的研究中，该团队开发了光学传感器来获得表面沉积物特性的定性二维图像。随着他们工作的进展，研究人员计划开发基于他们过去工作的传感器来创建3d图像。通过开发这种三维成像能力，进行广泛的现场测量和实验室实验，他们将能够使用他们的数据来定量分析传感器产生的图像。这将提高海洋学家模拟生物扰动对表层沉积物碳循环影响的能力，这反过来又将大大限制海洋无机碳通量中缺失的组成部分。

The top meter of sediment, called the bioturbation zone, is impacted by the variety of biological activities that occur on the seafloor. Marine animals such as worms or plant-like creatures often burrow in and out of, or grow roots into sediment, respectively. Because of this, the bioturbation zone is an area of constant sediment exchange between deep water and surface sediment. Every centimeter of sediment on the ocean floor can have unique chemical properties from the centimeter of sediment above and below it, but in the bioturbation zone, the activity of marine animals mixes these layers. Usually, oceanographers hoping to study what the past chemistry of the ocean was use the chemistry of sediment because, if one knows how fast it takes a centimeter of sediment to settle on part of the seafloor, then a piece of sediment at a defined depth corresponds to a time in the past; however, in the bioturbation zone this is impossible because very old (deep) sediment may have been transferred by a marine animal upward to be mixed in with newly settled (shallow) sediment. Because of this, the bioturbation zone is less studied and generally disregarded in studies of past ocean chemistry, which means there is little, if any, information on ocean processes from the last few decades. The researchers of this project plan to change that by making field measurements, performing laboratory experiments, and developing new sensor technology to advance our understanding of bioturbation zone effects on sediment chemistry. This will be a significant advancement for chemical oceanographers and geologists who hope to understand the ocean chemistry of approximately the last 50 years. Also, the sensors developed by these investigators will be a fantastic new tool for oceanographers, and these researchers are also dedicated to supporting broadening participation in ocean sciences by mentoring students from a wide variety of diverse backgrounds.Scientists from the State University of New York, Stony Brook propose to advance oceanographers' technical capabilities and abilities to model redox and acid-base reactions within the bioturbation zone. They plan to determine the impact of bioturbation on the dissolution, precipitation, and burial of carbonate minerals, as well as determine net alkalinity fluxes at the sediment-water interface. In past research, this team has developed optical sensors to get qualitative, 2-D images of surface sediment properties. With the progression of their work, the investigators plan to develop sensors that build on their past work to create 3-D images. By developing this 3-D image capability and making extensive field measurements and conducting laboratory experiments, they will be able to use their data to analyze the images created by the sensors quantitatively. This will advance oceanographers' ability to model the effects of bioturbation on carbon cycling in surface sediment, which will, in turn, significantly constrain a missing component of the oceanic flux of inorganic carbon.