RAPID: Enhancing Biodegradation of Deepwater Horizon Contaminant Hydrocarbons in Louisiana Salt Marsh Using High Layer Charge Montmorillonites

该项目的目的是立即实地测试粘土矿物增强受墨西哥湾持续漏油影响的沿海沼泽地石油烃有氧和厌氧微生物降解的功效。该项目将测试两个具体的假设。首先，高层电荷，高表面积层状硅酸盐增强沿海盐沼环境中石油烃的好氧生物降解。第二，这种增强也可以在厌氧沼泽环境中观察到。为了检验这些假设，将在三个25平方米的实验沼泽地中播种0.5厘米的蒙脱石粘土层，相邻的对照地块不变。项目人员将立即开始并在一年内对这些地块进行取样，监测石油碳氢化合物总量、碳氢化合物族组成、粘土矿物学和地球化学、土壤阳离子交换能力、主要水溶质组成、流体和固体中的重金属以及微生物群落组成。将利用沉积物和石油的实地样品，通过实验性微观世界模拟地下环境;将以与实地相同的方式监测厌氧微观世界，并对已知氧化石油碳氢化合物的厌氧硫酸盐还原剂的功能分子遗传学进行额外监测。该项目将汇集一套全面的分析技术，以获取所需数据。为该项目组建的多学科研究小组拥有土壤和粘土矿物学、分子和环境微生物学、分析地球化学、遥感和路易斯安那州沿海盐沼地貌学方面的专业知识。这种跨学科的合作是解决这一问题的有力途径，这将为水-矿物-生物系统的地球化学的长期研究奠定基础。本项目提出的假设检验解决了水-矿物-生物相互作用和环境微生物学中的几个基本问题。首先，它第一次在现场调查是否充电的微环境附近的矿物细胞壁界面的石油烃消费者提高代谢效率。这是基于以前的实验室研究假设的，但确切的机制知之甚少，该过程从未在该领域进行过研究。其次，该项目解决了厌氧微生物群落消耗石油烃的潜力这一关键问题。虽然这一直受到怀疑，但最近的证据表明，硫酸盐还原微生物群落可以发挥重要作用。如果在好氧微生物群落中观察到的粘土矿物增强过程在厌氧环境中具有相似的功能，则将揭示沉积物矿物学对微生物生态系统功能的影响的基本方面，这项调查将导致改进的方法来增强盐沼中污染物石油烃的自然衰减。除了应对海湾目前的危机外，这还将有助于解决沿海沼泽地石油污染这一长期的世界性问题。这项调查的结果将广泛传播给每年大约400名参加由PI教授的入门级和更高级别的环境相关课程的学生。两名博士生（一名地球科学，一名生物学）将为该项目的实验室工作做出贡献，一名女博士生（地球科学）将得到直接支持。这也将为三名初级教师提供与国家重大事件相关的研究经验。

The purpose of this project is to immediately field-test the efficacy of clay mineral enhancement of both aerobic and anaerobic microbial degradation of petroleum hydrocarbons in coastal marshes impacted by the ongoing oil spill in the Gulf of Mexico. The project will test two specific hypotheses. First, that high-layer charge, high surface area phyllosilicates enhance aerobic biodegradation of petroleum hydrocarbons in coastal salt marsh settings. And second, that such enhancement can also be observed in anaerobic marsh environments. To test these hypotheses, three 25m2 experimental marsh plots will be seeded with a 0.5cm layer of montmorillonite clay, with adjacent unchanged control plots. Starting immediately, and proceeding over the course of one year, project personnel will sample these plots and monitor total petroleum hydrocarbon, hydrocarbon group composition, clay mineralogy and geochemistry, soil cation exchange capacity, aqueous major solute composition, heavy metals in fluid and solid phases, and microbial community composition. The subsurface environment will be simulated by an experimental microcosm using field samples of sediment and oil; anaerobic microcosms will be monitored in the same manner as the field sites, with the additional monitoring of functional molecular genetics of anaerobic sulfate-reducers known to oxidize petroleum hydrocarbons. The project will bring together a comprehensive suite of analytical techniques to acquire the needed data. The multidisciplinary research team assembled for this project has expertise in soils and clay mineralogy, molecular and environmental microbiology, analytical geochemistry, remote sensing, and geomorphology of Louisiana coastal salt marshes. Such crossdisciplinary collaboration is a powerful approach to the problem, and this will lay the groundwork for continued long-term research on the biogeochemistry of water-mineral-biota systems.The hypothesis-testing proposed for this project addresses several fundamental questions in water-mineral-biota interactions and environmental microbiology. First, for the first time it investigates in the field whether the charged microenvironment near the mineral-cell wall interface of petroleum hydrocarbon consumers enhances metabolic efficiency. This has been hypothesized based on previous laboratory studies, but the precise mechanisms are poorly known and the process has never been studied in the field. Second, this project addresses the critical question of the potential for anaerobic microbial communities to consume petroleum hydrocarbons. Although this has been doubted, recent evidence suggests that sulfate reducing microbial communities can play a significant role. If the clay mineral enhancement process observed in aerobic microbial communities functions similarly in anaerobic environments, it will shed light on fundamental aspects of the impact of sediment mineralogy on microbial ecosystem function.This investigation will lead to improved methods to enhance natural attenuation of contaminant petroleum hydrocarbons in salt marshes. In addition to responding to the current crisis in the Gulf, this will also help address the chronic worldwide problem of oil contamination in coastal marshes. The results of this investigation will be widely disseminated to the approximate 400 students per year enrolled in environment-related courses taught by the PI's at introductory and higher levels. Two PhD students (one Geosciences, one Biology) will contribute to the laboratory work for this project, and one female PhD student (Geosciences) will be directly supported. This will also provide three junior faculty with research experience related to an event of national significance.