Collaborative Research: Megaripples as biocatalytical filters

该项目侧重于大型水下沙层在营养物质和有机物质循环中的作用，特别是在河口。“巨型藻类”是海底水流湍急的海洋沉积物的常见特征。在墨西哥湾东北部，这些类似沙丘的地物高达半米，波长可达20米。研究人员提出，巨型藻类充当大型过滤系统，迅速将溶解和固体有机物转化为无机碳和营养物质，从而影响沿海水域的生物生产力。他们计划使用墨西哥湾东北部乔塔瓦奇湾入口处一公里长的巨型田地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，以较小规模调查过滤过程。该项目通过编制有关巨噬细胞功能的数据，解决了对我们对沿海水域物质循环的理解有影响的知识差距。该项目为研究生和本科生提供学习最先进技术的机会。学生们将在高频数据采集和大数据分析方面获得经验。为了加强宣传，研究人员将开发和教授两门课程，即可渗透沉积物生物地球化学和佛罗里达州立大学提供的周六海上水生涡流协方差研究课程。结果将通过科学期刊、会议报告和公开讲座传播，并直接分发给阿巴拉契科拉国家河口研究保护区(NERR)，后者将向其他28个国家河口研究保护区提供这些成果。项目的两个主要目标是：1)展示巨型藻类作为生物催化过滤器的一般功能，2)展示普通进口巨型藻类有助于沿海海湾的养分保持。位于墨西哥湾东北部乔塔瓦奇湾(波长：~20米，幅度：20-40厘米)入口处的一块长1公里的巨型田野将被用作现场实验室。测量将描述巨型地形和流经它们的水的特征。盐度和悬浮颗粒被用作天然示踪剂，以定量溶质和颗粒夹带到大颗粒中。该项目将部署配备新开发的坚固传感器的非侵入性水涡协方差仪器，以量化冲刷过的巨型岩床中的沉积再矿化作用。这项技术综合了巨型磁场大片区域内的海底氧通量，同时包含了电流和光的自然动力学。使用船载流动分析仪进行实时水柱测量，可以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，该实验将通过冲洗的巨型沙子中的有机碳矿化来量化营养物质的再动员。乔塔瓦奇湾入海口的巨型油田很容易从海岸和小船到达，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数量上的理解，即巨型细胞是天然的生物催化过滤器。由于巨型藻类的运输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有关巨型藻类一般生物地球化学功能的信息。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.