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

该项目将评估河岸（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）积累在土壤中。因此，一个因素，可以改变硅在河流中的通量是在活跃的河床植被覆盖的变化。河岸植被的变化可能会导致河流硅运输显着减少有两个原因。首先，植物通过将DSi转化为ASi来螯合Si。其次，植被导致河流流速降低，悬浮泥沙沉积增加，包括ASi。两个高度受影响的河流，在内布拉斯加州的普拉特河和犹他州的绿色河，将作为案例研究，以量化的影响，河岸植被一般，特别是入侵物种的草芦苇，对硅运输到海洋。三个ASi池的测量？河岸沉积物、河岸植被和河流中的悬浮沉积物？和DSi的河流将被用来确定植被影响的大小。该项目将考虑硅的地球化学，植物鉴定和表征，以及粒子的传输和沉积，以全面了解控制河流硅传输的物理-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体的限制性营养素。一系列人类活动减少了从陆地到海洋的硅的输送，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。人类对河流流量的修改可能会导致有利于河岸植被扩张的条件，这可能会减少河流运输的硅。我们的研究将是第一个分离的河岸植被对硅的河流输送的影响，并测量在美国西部两个典型的河流的总硅通量。因此，这项工作将提高我们对陆地-河流-海洋连续体的认识，并可能为有关河流和沿海海洋资源管理的决策提供信息。这个合作项目汇集了PI和来自Gustavus Adolphus学院（主要是本科院校）的六名本科研究人员以及来自犹他州州立大学和艾克斯-马赛大学的共同PI的专业知识。本科研究人员将参与该项目的各个方面，最终包括通过出版物，会议演示和大学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.