RUI-Collaborative Research: Reduction in riverine silica transport due to human-induced vegetation change to riparian vegetation

该项目将评估河岸植被在通过河流将生物可利用形式的二氧化硅（Si）从陆地转移到海洋中的作用。植物从水中吸收溶解的二氧化硅（DSi），并将其转化为无定形颗粒（ASi），在土壤中积累。因此，改变河流中Si通量的一个因素是活跃河床植被覆盖的变化。河岸植被的变化可能导致河流硅输运的显著减少，原因有二。首先，植物通过将DSi转化为ASi来隔离Si。其次，植被降低了河流流速，增加了悬浮物的沉积，包括ASi。内布拉斯加州的普拉特河（Platte River）和犹他州的格林河（Green River）这两条受到严重影响的河流将作为案例研究，以量化河岸植被，尤其是芦苇（Phragmites australis）的入侵物种对硅向海洋运输的影响。三池ASi的测量？在河岸沉积物、河岸植被和河流中的悬浮沉积物中？和河流中的DSi将用于确定植被效应的大小。该项目将考虑硅地球化学，植物鉴定和表征，以及颗粒运输和沉积，以全面了解控制河流硅运输的物理-生物-生物地球化学相互作用。河流是沿海海洋生态系统硅的主要来源，它通常是重要浮游植物群的限制性营养物质。一系列人类活动减少了硅从陆地向海洋的输送，这对已经受到各种环境变化压力的海洋生态系统来说是一个重大问题。人类对河流流量的改变可能导致有利于河岸植被扩张的条件，这可能会减少河流输送的Si。我们的研究将首次分离出河岸植被对河流输送硅的影响，并测量美国西部两条典型河流的总硅通量。因此，这项工作将提高我们对陆地-河流-海洋连续体的理解，并可能为有关河流和沿海海洋资源管理的政策决定提供信息。这个合作项目汇集了PI和来自Gustavus Adolphus学院的六名本科生研究人员以及来自犹他州立大学和艾克斯-马赛大学的联合PI的专业知识。本科生研究人员将参与项目的各个方面，最终包括通过出版物、会议报告和学院博物馆展览的发展传播结果。

This project will evaluate the role of riparian (riverbank) vegetation in the transfer of bioavailable forms of silica (Si) from land to sea via rivers. Plants absorb dissolved silica (DSi) from water and transform it into amorphous particles (ASi) that accumulate in soils. Therefore, one factor that can alter the flux of Si in rivers is a change in vegetation cover in the active riverbed. Changes in riparian vegetation may cause significant reductions in riverine Si transport for two reasons. First, plants sequester Si by transforming DSi into ASi. Second, vegetation leads to reduced river flow velocity and increased deposition of suspended sediment, including ASi. Two highly-impacted rivers, the Platte River in Nebraska and the Green River in Utah, will serve as case studies to quantify the effect that riparian vegetation in general, and the invasive species of grass Phragmites australis in particular, have on Si transport to the ocean. Measurement of three pools of ASi ? in riparian sediment, riparian vegetation, and suspended sediment in the river ? and DSi in the river will be used to determine the magnitude of the vegetation effect. This project will consider silicon geochemistry, plant identification and characterization, and particle transport and deposition to develop a holistic understanding of the physical-biological-biogeochemical interactions controlling riverine Si transport.Rivers are the primary source of silicon to coastal ocean ecosystems, where it is often a limiting nutrient for important groups of phytoplankton. An array of human activities has decreased the delivery of Si from land to sea, which is a significant concern for marine ecosystems already under pressure from a variety of environmental changes. Human modifications to river flows may lead to conditions favoring the expansion of riparian vegetation, which may reduce Si transported by the river. Our research will be the first isolate the effects of riparian vegetation on Si transported by rivers, and to measure the total Si flux in two typical western U.S. rivers. Therefore, the work will improve our understanding of the land-river-sea continuum, and may inform policy decisions regarding rivers and coastal ocean resource management. This collaborative project brings together the expertise of the PI and six undergraduate researchers from Gustavus Adolphus College, a primarily undergraduate institution, and the co-PIs from Utah State University and the University of Aix-Marseille. The undergraduate researchers will be involved in all aspects of the project, ultimately including dissemination of results via publications, conference presentations and development of a college museum exhibit.