Prediction of Bioavailability of Riverine Dissolved Organic Matter from Bulk Measures of Geochemical Composition Accross Landscape and Continental Gradients

9816130全球范围内，土地利用变化、城市发展和气候变化正在改变河流向海岸带和海洋输入的有机质和无机营养物的数量和性质。河流输入的这种长期且可能不可逆转的变化，预计会引发全球和沿海碳收支以及沿海食物网、富营养化、缺氧和物种多样性的相应变化。对这些变化的机械理解需要我们在定量处理河流运输过程中有机物转化的能力上有实质性的提高。在我们之前的单独研究中，我们发现南部河流中DOM的生物利用度与DOM的脂肪碳含量有关，这是由其平均元素组成表明的。我们进一步通过生物能量模型发现，许多简单有机底物被氧化并并入微生物生物量的速率和效率与这些底物的还原程度密切相关，这是由它们的元素组成推断的。初步的联合研究表明，DOM的生物利用度的这两个预测因子是密切相关的（正如理论所期望的那样），并且几乎同样成功。我们计划解决3个研究问题：1。河流DOM的生物利用度在溪流和河流中如何变化？我们可以通过简单的体积组成来预测DOM的生物利用度吗？DOM的生物利用度可以通过简单的化学需氧量测量来预测吗？通过使用微生物生长的生物能量模型和技术来描述不稳定和大块DOM池的底物减少程度，我们将研究大块和大块DOM池的组成和利用之间的关系。我们的目标是测试我们为已知的不稳定DOM池开发的模型，通过对大块DOM池组成的简单测量来预测大块有机物的利用率和微生物的生长速度。这是一个成功的有机物利用模型，在简单的化学成分测量的基础上，提供了对微生物过程的因果机制理解。到目前为止，我们的工作是初步的，因为DOM样本只从几个地点收集，没有采用系统的方法来调查DOM来源的光谱，并且执行实验的技术以及关于生物利用度的理论当时还在开发中。我们现在能够严格地测试我们的模型，并建议在特征截然不同的溪流和河流中进行实验。我们将测量有机物组成（脂肪族、芳香族和过量碳以及底物还原程度）和生物利用度（微生物生长、生长效率和有机物氧化）。根据我们的模型，DOM的生物利用度与脂肪族C含量和DOM的底物还原程度之间存在很强的相关性。该提案已提交给EGB计划，并由以下机构共同资助：OCE - (Rice)事业部债务部-（北区）

9816130Perdue Land-use change, urban development, and climate change are altering the magnitude and nature of riverine inputs of organic matter and inorganic nutrients to the coastal zone and oceans throughout the world. Such long-term, and probably irreversible, changes in riverine inputs can be expected to trigger corresponding changes in both global and coastal carbon budgets and in coastal food webs, eutrophication, and anoxia and species diversity. A mechanistic understanding of these changes requires a substantial improvement in our ability to treat quantitatively the transformation of organic matter during riverine transport. In our prior separate research, we found that the bioavailability of DOM in a southern river is related to the aliphatic carbon content of the DOM, as indicated by its average elemental composition. We further found with a bioenergetic model that the rate and efficiency at which many simple organic substrates are oxidized and incorporated into microbial biomass are closely related to the degree of reduction of those substrates, as deduced from their elemental composition. Preliminary joint research showed that these two predictors of bioavailability of DOM are strongly correlated (as expected from theory) and about equally successful.We plan to address 3 research questions:1. How does the bioavailability of riverine DOM vary in stream and rivers?2. Can we predict the bioavailability of DOM from simple measures of bulk composition?3. Can bioavailability of DOM be predicted from a simple measurement of chemical oxygen demand?With the use of our bioenergetic model of microbial growth and techniques to describe the degree of substrate reduction of labile and bulk DOM pools, we will examine relationships between the composition and utilization of bulk and labile pools. Our goal is to test our model that was developed for known labile DOM pools to predict the rates of bulk organic matter utilization and microbial growth from simple measurements of the composition of the bulk DOM pool. This is a successful model of organic matter utilization that provides a causal, mechanistic understanding microbial processes on the basis of simple measures of chemical composition. Our work to date is preliminary since DOM samples were collected from only a few sites, a systematic approach to investigate a spectrum of DOM sources was not employed, and the techniques to perform the experiments as well as the theories regarding bioavailability were under development at the time. We are now in a position to rigorously test our models and propose to do so by conducting experiments in streams and rivers of greatly contrasting characteristics. We will measure organic matter composition (aliphatic, aromatic and excess carbon and degree of substrate reduction) and bioavailability (microbial growth, growth efficiency and organic matter oxidation). Based on our models, a strong correlation should be observed between DOM bioavailability and aliphatic C content and degree of substrate reduction of the DOM. This proposal was submitted to the EGB Program, and is being jointly funded by:1. Division of OCE - (Rice)2. Division of DEB - (Firth)