Collaborative Research: Megaripples as biocatalytical filters

该项目侧重于大型水下沙层的作用，特别是在河口，在营养物质和有机物质的循环。在海底水流湍急的海洋沉积物中，“巨型波纹”是常见的特征。在墨西哥湾东北部，这些沙丘状的特征高达半米高，波长达到20米。研究人员提出，巨虹膜作为一个大型过滤系统，可以迅速将溶解的固体有机物质转化为无机碳和营养物质，从而影响沿海水域的生物生产力。他们建议在墨西哥湾东北部的Chotawhatchee湾的入口使用一公里长的巨型水田，作为研究这些过程的天然实验室。此外，他们将进行实验室实验，以较小规模研究过滤过程。通过生成巨水波功能的数据，该项目解决了一个知识缺口，这对我们对沿海水域物质循环的理解产生了影响。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。为了加强外联，研究人员将为佛罗里达州立大学提供的海洋项目开发和教授两门课程，分别是渗透性沉积物生物地球化学和水生涡旋相关研究。研究结果将通过科学期刊、会议报告和公开演讲传播，并直接传播给阿巴拉契科拉-国家河口研究保护区（NERR），后者将把研究结果提供给其他28个NERR站点。两个主要的项目目标是：1)证明巨型水袋作为生物催化过滤器的一般功能，以及2)证明普通进口巨型水袋有助于沿海海湾的营养保留。在墨西哥湾东北部的Chotawhatchee湾（波长：~20米，振幅：20 ~ 40厘米）的入口，一个1公里长的巨型涟漪场将被用作现场实验室。测量将描绘巨涟波地形和流过它们的水。盐度和悬浮颗粒被用作天然示踪剂来量化溶质和颗粒夹带到巨微泡中的情况。该项目将部署非侵入性水生涡动相关仪器，配备新开发的强大传感器，以量化冲积巨涟床的沉积再矿化。这项技术整合了巨涟漪场大片区域的底栖氧气通量，同时还包括了电流和光的自然动态。实时水柱测量与船载流量通过分析仪允许快速定量的大水平梯度的关键水柱参数。现场测量将与实验室柱式反应器实验相结合，定量通过冲洗megariple砂中有机碳矿化的营养再动员。位于Chotawhatchee海湾入口的megaripple油田很容易从岸上和小船到达，这加快了仪器的部署和现场测量，同时降低了项目成本。综合所有的数据将产生一个概念和定量的理解，巨滴作为天然的生物催化过滤器。由于巨奶袋中的转运和反应受基本物理和生物地球化学过程的支配，这些结果将揭示迄今为止尚未获得的巨奶袋一般生物地球化学功能的信息。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.