Collaborative Research: Megaripples as biocatalytical filters

该项目的重点是大型水下砂层的作用，特别是在河口，在营养物质和有机物质的循环。“巨型突起”是海底水流迅速的海洋沉积物的常见特征。在墨西哥湾东北部，这些沙丘状特征高达半米，波长达到20米。研究人员提出，巨型水团充当大型过滤系统，迅速将溶解和固体有机物转化为无机碳和营养物质，从而影响沿海沃茨的生物生产力。他们建议在墨西哥湾东北部的Chotawhatchee湾的入口处使用一公里长的megaripple场，作为研究这些过程的天然实验室。此外，他们还将进行实验室实验，以研究较小规模的过滤过程。该项目通过提供关于巨型粒子功能的数据，填补了一个知识空白，这对我们理解沿海沃茨的物质循环有影响。该项目为研究生和本科生提供了学习最先进技术的机会。学生将获得高频数据采集和“大数据”分析的工作经验。为了加强推广，研究人员将为佛罗里达州立大学提供的海洋星期六项目开发和教授两门关于可渗透沉积物生物地球化学和水生涡流协方差研究的课程。研究结果将通过科学期刊、会议报告和公开讲座传播，并直接发送给阿巴拉契科拉国家河口研究保护区（NERR），后者将向其他28个NERR站点提供研究结果。两个主要的项目目标是：1）展示megaripples作为生物催化过滤器的一般功能，2）展示常见的入口megaripples有助于沿海海湾的营养物质保留。 墨西哥湾东北部Chotawhatchee湾入口处的1公里长的巨波场（波长：~20米，振幅：20至40厘米）将用作原位实验室。测量将描述巨型地形和流过它们的水。盐度和悬浮颗粒被用作天然示踪剂，以量化溶质和颗粒夹带到megaripples。该项目将部署非侵入性水生涡动协方差仪器，配备新开发的强大传感器，以量化冲洗megaripple床中的沉积物矿化。这项技术综合了大部分巨型瀑布场的海底氧通量，同时包括水流和光线的自然动态。使用船载流通分析仪进行实时水柱测量，可快速量化关键水柱参数的大水平梯度。现场测量将与实验室柱反应器实验相结合，该实验室柱反应器实验通过冲洗的megaripple砂中的有机碳矿化来量化营养物的再动员。位于Chotahatchee湾入口处的megaripple场可以从海岸和小船轻松到达，加快了仪器部署和现场测量，同时降低了项目成本。所有数据的综合将产生一个概念和定量的理解megaripples作为天然生物催化过滤器。由于megaripples的传输和反应受基本物理和地球化学过程的控制，这些结果将揭示megaripples的一般地球化学功能的信息，到目前为止还没有。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

This project focuses on the role of large underwater sand formations, particularly at the mouths of estuaries, in the cycling of nutrients and organic materials. "Megaripples" are common features on marine sediments where bottom currents are rapid. In the northeastern Gulf of Mexico, these sand dune-like features are up to half a meter in height, with wavelengths reaching 20 meters. The investigators propose that megaripples act as large filter systems that rapidly convert dissolved and solid organic matter into inorganic carbon and nutrients, and thus influence the biological productivity of coastal waters. They propose to use a one-kilometer long megaripple field in the inlet of Chotawhatchee Bay, in the northeastern Gulf of Mexico, as a natural laboratory for studying these processes. In addition, they will conduct laboratory experiments to investigate the filter processes at a smaller scale. By producing data on the functioning of megaripples, the project addresses a knowledge gap that has implications on our understanding of the cycles of matter in coastal waters. The project offers opportunities for both graduate and undergraduate students in learning state-of-the-art techniques. The students will gain experience in working on high frequency data acquisition and analysis of 'big data'. To enhance outreach, the researchers will develop and teach two courses on Permeable Sediment Biogeochemistry and Aquatic Eddy Covariance Studies for the Saturday at the Sea program offered by Florida State University. Results will be disseminated via scientific journals, conference presentations and public lectures, and directly to the Apalachicola-National Estuarine Research Reserve (NERR), which will make the results available to the other 28 NERR sites. The two main project objectives are: 1) demonstrate the general function of megaripples as biocatalytical filters, and 2) demonstrate that common inlet megaripples contribute to nutrient retention in coastal bays. A 1 km long megaripple field in the inlet of Chotawhatchee Bay (wavelengths: ~20 m, amplitudes: 20 to 40 cm) in the northeastern Gulf of Mexico will be used as an in-situ laboratory. Measurements will characterize megaripple topography and the water flowing over them. Salinity and suspended particles are utilized as natural tracers to quantify solute and particle entrainment into the megaripples. This project will deploy non-invasive aquatic eddy covariance instruments equipped with newly developed robust sensors to quantify sedimentary remineralization in the flushed megaripple bed. This technique integrates the benthic oxygen flux over a large section of the megaripple field, while including the natural dynamics of currents and light. Real-time water column measurements with a boat-mounted flow-through analyzer permit rapid quantification of large horizontal gradients of key water column parameters. The in-situ measurements will be combined with laboratory column reactor experiments that quantify nutrient re-mobilization through organic carbon mineralization in flushed megaripple sand. The megaripple field in the inlet of Chotawhatchee Bay is easily accessible from shore and by small boat, expediting instrument deployments and in-situ measurements while reducing project costs. Synthesis of all data will produce a conceptual and quantitative understanding of megaripples as natural biocatalytical filters. Because transport and reaction in megaripples are governed by basic physical and biogeochemical processes, these results will reveal information on the general biogeochemical functioning of megaripples that so far is not available.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.