Collaborative Research: Controls on Delivery and Fate of Water, Nitrogen, and Calcium in a Spring-Fed Karst River

智力优势：河流系统的水文、地貌和地球化学动力学在从几小时到几千年的时间尺度上相互耦合。集水输入和流径特性通过对水和溶质输送动力学的影响来影响地貌和地球化学过程。同时，河流生物群的代谢过程对水文、形态和生态地球化学具有相互控制的作用。这些耦合的生物-非生物相互作用导致复杂的非线性响应，需要高时空密度的数据来理解。在泉源岩溶河流，强烈的生物-非生物相互作用，预计由于高植物产量和低流速，并假设控制N和DO动态，具有重要的生态系统后果，也与影响矿物溶解，从而岩溶通道的发展河水pH值。生物控制溶质输送的幅度，并链接到流通道溶解，知之甚少。因此，该建议解决了3个问题，连接生物和非生物处理的泉岩溶通道：1）地下流动路径如何随气候和流动状态而变化，以及它们如何控制泉水输送的大小，以及水的溶质化学？2)水文和地貌对河流氮素处理的控制作用是什么？3)在低起伏岩溶河流中，生物和水文对河道溶解的控制作用是什么？研究地点是佛罗里达北部的Ichetucknee河，多个测量的泉水合并形成一条8公里长的河流，该河流也在泉水下游5公里处测量。工作计划包括：1）在战略性选择的泉水喷口和河流地点利用最先进的传感器连续测量水化学，2）对不连续测量或在非传感器地点的分析物进行天气水采样，以及3）分析Ichetucknee和其他区域重要泉水的档案数据，以更普遍地测试假设。连续记录传感器，测量DO浓度，T，阶段，比电导率和pH值，将部署在两个弹簧，代表两个水化学组的Ichetucknee复杂。这些传感器，连同连续的NO3和浊度传感器，沿着也将部署在下游的三个地点。连续测量的数据将被用来评估交付的变化和流中处理的N（如同化吸收与异化损失）在昼夜，情节，季节和年际时间尺度。每月天气采样将把生物过程与碳酸盐饱和状态和溶解联系起来。对该地区泉水的档案数据进行分析，将允许对跨越大量泉水的流量与化学关系进行统计分析（自相关/互相关）。的温泉是重要的区域文化，经济和生态资源;观察到的生态衰退，使弹簧目前的监管考虑的主题，重点是N污染。由于监管方案的辩论，穷人的机械理解如何弹簧过程N限制了能力，提出建议，如何管理他们。多个地方和州监管机构和利益相关者团体（例如，Ichetucknee Springs Basin Working Group，佛罗里达环境保护部，佛罗里达Springs Task Force）允许将科学知识转化为政策和公共教育。这项拟议工作的结果将定期在公共和机构会议上提交给利益攸关方。研究的很大一部分将在少数民族服务机构（佛罗里达国际大学）进行;代表性不足的群体将被招募为学生和博士后候选人。将这项工作与沃茨试验台的位置放在一起，将扩大在初步研究期间获得的关于传感器网络和数据基础设施的专业知识。这项工作将为建立传感平台提供额外的技术进步，允许在过程和管理相关的时间尺度上收集有关河流系统的关键信息。

Intellectual Merit: Hydrologic, geomorphic and biogeochemical dynamics of river systems are coupled over time scales ranging from hours to millennia. Catchment inputs and flowpath properties influence geomorphic and biogeochemical processes through effects on water and solute delivery dynamics. Simultaneously, metabolic processes of river biota can exert reciprocal control on hydrology, morphology, and biogeochemistry. These coupled biotic-abiotic interactions lead to complex, non-linear responses that require high spatiotemporal density of data to understand. In spring-fed karst rivers, strong biotic-abiotic interactions are expected due to high plant production and low flow velocity, and are hypothesized to control both N and DO dynamics, with important ecosystem consequences, and also river water pH with implications for mineral dissolution and thus karst channel development. The magnitude of biotic controls on solute delivery, and links to stream channel dissolution, are poorly understood. Consequently, this proposal addresses 3 questions that link biotic and abiotic processing of spring-fed karst channels: 1) How do sub-surface flow paths vary with climate and flow regime, and how do they control the magnitude of spring water delivery, and the solute chemistry of the water? 2) What are the hydrologic and geomorphic controls on riverine N processing? 3) What are the biotic and hydrologic controls on channel dissolution in low-relief karst rivers?The study site is the Ichetucknee River in north Florida where multiple gauged springs merge to form an 8-km long river, which is also gauged 5 km downstream of the springs. The work plan includes: 1) continuous measurements of water chemistry, utilizing state-of-the-art sensors at strategically selected spring vent and river sites, 2) synoptic water sampling for analytes not continuously measured or at non-sensor sites, and 3) analysis of archival data at Ichetucknee and other regionally important springs to test hypotheses more generally. Continuously recording sensors, that measure DO concentrations, T, stage, specific conductivity, and pH, will be deployed at two springs, representing two hydrochemical groupings of the Ichetucknee complex. These, along with continuous NO3 and turbidity sensors, will also be deployed at three locations downstream. The continuously measured data will be used to assess delivery variability and in-stream processing of N (e.g. assimilatory uptake versus dissimilatory loss) at diel, episodic, seasonal, and inter-annual time scales. Monthly synoptic sampling will link the biological processes to carbonate saturation state and dissolution. Analyses of archival data from springs across the region, will allow statistical analyses (auto/cross-correlation) of discharge vs. chemistry relationships spanning a larger population of springs.Broader Impacts: Florida?s springs are significant regional cultural, economic, and ecological resources; observed ecological declines have made springs the subject of current regulatory consideration, with a focus on N pollution. As regulatory options are debated, poor mechanistic understanding of how springs process N limits the ability to make recommendations for how to manage them. Multiple local and state regulatory agencies and stakeholder groups (e.g., Ichetucknee Springs Basin Working Group, Florida Department of Environmental Protection, Florida Springs Task Force) allow translation of scientific knowledge into policy and public education. Results from this proposed work will be presented regularly to stakeholders at public and agency meetings. A significant portion of the research will be conducted at a minority serving institution (Florida International University); under-represented groups will be recruited to work as students and post-doctoral candidates. Co-locating this work with a WATERS test-bed location will expand the expertise gained about sensor networks and data infrastructure during the preliminary studies. This work will provide additional technological advances toward building sensing platforms, allowing critical information about river systems to be collected across process and management relevant time-scales.