A Metabolically Active Transient Storage Model for Predicting Nutrient Retention in Streams

用于预测溪流中养分保留的代谢活跃瞬时存储模型

• 批准号: 0838338
• 负责人: Roy Haggerty
• 金额: $ 41.71万
• 依托单位: Oregon State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-10-01 至 2013-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0838338&HistoricalAwards=false
• 关键词: Metabolically; Active; Transient; Storage; Model

A Metabolically Active Transient Storage Modelfor Predicting Nutrient Retention in StreamsRoy Haggerty, Alba Argerich, David D. Myrold, Eugènia Martí & Nancy B. GrimmTransient storage has become one of the most important concepts in hydrology in the past 25 years,helping to predict solute and heat transport in streams, and it is one of the most frequently quantifiedprocesses in stream ecology. However, recent research shows that transient storage has minimalexplanatory power for nutrient retention in streams. This is a paradox because nutrient retention isclosely tied to aerobic metabolism, which in turn is very strongly tied to hyporheic exchange, a majorcomponent of transient storage. Further, other processes that retain nutrients (sorption of phosphorus,and anaerobic microbial processes) also should happen preferentially in transient storage zones.Consequently, it is surprising that transient storage has not been a better predictor for nutrientretention.We hypothesize that nutrient retention is mostly associated with transient storage that ismetabolically active. Metabolically active transient storage (MATS) is defined as water with velocitymuch slower than the mean in which there is significant primary production or respiration. Wepredict that MATS will include much of the hyporheic zone and some benthic areas of pools. Givenknown mechanistic relationships between nutrient transformations and metabolism, we predict thatMATS zones will also be hotspots for nutrient retention.We have done preliminary work to develop a MATS-sensitive tracer, resazurin. Resazurin quicklyreduces to resorufin in the presence of aerobic respiration. Our tests indicate that it is feasible to useresazurin in streams to measure MATS, and that a standardized methodology to measure MATS canbe adopted similar to what is commonly done with a conservative tracer (e.g., NaCl) to measuretransient storage.We will conduct a series of column and mesocosm experiments to relate nutrient retention tometabolism (focusing on respiration). We will also test the relationship between resazurin reductionand respiration in different substrates and multiple sediment samples, and further characterizeresazurin sorption, photodegradation, and degradation. We will then conduct field experiments,adding nutrients and resazurin in streams. These will primarily be conducted in heterotrophic, lownutrientstreams of Oregon, but a few experiments will also be conducted in Arizona and Spain toadd a gradient in metabolism and dissolved inorganic nitrogen to phosphorus (DIN:P) ratio.Injections will also be carried out at different times of the year encompassing a metabolism gradientwithin the Oregon streams, so that our interpretations are not limited to inter-stream variability.Streams will be surveyed and geomorphically characterized to help control for physical differences.A preliminary model of MATS is presented, and will be further developed during the study. Acomputer code will be updated and released that can model and do parameter estimation for reactivetransport in streams in the presence of MATS, where the timescales of exchange may be theconventional exponential distribution or another distribution.Broader impact: Correlation of nutrient retention with MATS would improve our understanding ofthe hydrologic component of nutrient retention and help us to predict transport of nutrients in streams.Resazurin reduction could prove a valuable tool for measuring MATS, and open the way for a tracerbasedquantification of respiration. Lastly, we will work with an elementary school to gauge a streamand collect stream nutrient data as part of their science curriculum. The data are important to theCity of Corvallis because of a proposal to use a large quantity of treated wastewater for irrigation inthe watershed that the stream drains, and there is no gauge.

roy Haggerty, Alba Argerich, David D. Myrold, eug<s:1> Martí & Nancy B. grim在过去的25年里，瞬时储存已经成为水文学中最重要的概念之一，它有助于预测河流中的溶质和热量输送，是河流生态学中最常被量化的过程之一。然而，最近的研究表明，瞬时储存对溪流中的营养物质保留的解释能力很小。这是一个悖论，因为营养保留与有氧代谢密切相关，而有氧代谢又与隐性交换密切相关，后者是瞬时储存的主要组成部分。此外，其他保留营养物质的过程（磷的吸收和厌氧微生物过程）也应优先在瞬态储存区进行。因此，令人惊讶的是，短暂储存并没有更好地预测营养倾向。我们假设营养保留主要与代谢活跃的短暂储存有关。代谢活性瞬时储存（MATS）被定义为速度比有显著初级生产或呼吸的平均速度慢得多的水。我们预测，垫将包括大部分的潜海区和一些底栖池区。鉴于已知的营养转化和代谢之间的机制关系，我们预测垫区也将是营养保留的热点。我们已经做了初步的工作来开发一种对mat敏感的示踪剂，reazurin。reazurin在有氧呼吸作用下迅速还原为再萘酚。我们的测试表明，使用流中的azurin来测量MATS是可行的，并且可以采用一种标准化的方法来测量MATS，类似于通常使用保守示踪剂（例如NaCl）来测量瞬态存储。我们将进行一系列的柱和中观实验，将营养保留与代谢（重点是呼吸）联系起来。我们还将测试不同底物和多种沉积物样品中蓝藻苷还原与呼吸之间的关系，并进一步表征蓝藻苷的吸附、光降解和降解。然后，我们将进行实地试验，在溪流中添加营养物和resazurin。这些实验将主要在俄勒冈州的异养、低营养的溪流中进行，但也将在亚利桑那州和西班牙进行一些实验，以增加代谢和溶解无机氮磷（DIN:P）比的梯度。注射也将在一年中的不同时间进行，包括俄勒冈溪流内的代谢梯度，因此我们的解释不限于溪流间的变化。将对溪流进行调查和地貌特征，以帮助控制物理差异。提出了一个初步的MATS模型，并将在研究中进一步发展。计算机代码将被更新和发布，可以对存在MATS的流中的反应性输运进行建模和参数估计，其中交换的时间尺度可能是传统的指数分布或另一种分布。更广泛的影响：营养物质保留与MATS的相关性将提高我们对营养物质保留的水文成分的理解，并帮助我们预测营养物质在河流中的运输。Resazurin还原可以证明是测量MATS的有价值的工具，并为基于示踪剂的呼吸定量开辟了道路。最后，我们将与一所小学合作，测量河流并收集河流营养数据，作为他们科学课程的一部分。这些数据对科瓦利斯市来说很重要，因为有一项建议是将大量处理过的废水用于河流排放的流域灌溉，而没有测量装置。