The Role of Protozoa in the Carbon Cycle of a Subterranean Estuary

伊丽莎白B。Kujawinski -伍兹霍尔海洋研究所含水层系统中的碳循环，特别是原核和真核微生物的作用，知之甚少。 海洋和淡水系统中的大量工作表明，原生动物等真核生物在所有水生环境中的碳和营养循环中发挥着重要作用-从营养丰富的沿海系统到营养贫乏的海洋环流。 然而，只有相对较少的研究探讨了原生动物在含水层系统中的作用。 考虑到这些生物在其他水生环境中发挥的关键作用，可以合理地假设它们在地下的碳和营养循环中发挥着重要作用。 现在是时候调查哪些原生动物物种存在，它们吃草的细菌以及原生动物吃草对地下水中碳和营养循环的影响。 这项工作的目标是利用稳定同位素结合地球化学和微生物的方法来研究原生动物的营养再生率和碳矿化在科德角MA的地下河口的影响。 这项工作将使用13 C标记的底物，如醋酸盐，以跟踪活跃的细菌和原生动物群落。 沉积物将从地下河口的淡水和盐水端元收集，并将用于建立流通柱。 这些柱子将与从河口适当地点抽取的地下水一起培养，以保持原位盐度和离子组成。 地下水将用13 C-基质进行修正。 将通过无机碳（含水CO2物质）、大量有机碳（TOC / DOC）和小有机分子（挥发性有机酸和氨基酸）的同位素比质谱法监测同位素标记从底物到有机物的移动。 将通过检查同位素标记的核酸和磷脂脂肪酸（PLFA）来评估标记物与微生物生物量的结合。 活性细菌和原生动物种属将通过其同位素标记的rDNA或rRNA序列进行鉴定。 原生动物和细菌的相对作用将通过与1.0 um过滤和未过滤地下水平行的柱孵育进行评估。据我们所知，这项拟议中的工作是第一项研究，直接将原生动物群落组成与淡水和咸水层中的营养再生和碳矿化联系起来。 这组微生物是大大研究不足，这项研究的结果有可能阐明回收过程以外的含水层沉积物中的微生物活动的当前范例。 此外，这里开发的方法可以普遍适用于许多环境中的生态和地球化学研究，从淡水系统到海洋沉积物。

EAR-0525166Elizabeth B. Kujawinski - Woods Hole Oceanographic InstitutionThe carbon cycle in aquifer systems, and particularly the role of prokaryotic and eukaryotic microbes, is poorly understood. A large body of work in marine and freshwater systems has indicated that eukaryotes such as protozoa play fundamental roles in the carbon and nutrient cycles in all aquatic environments - ranging from nutrient-rich coastal systems to nutrient-poor mid-ocean gyres. Nevertheless, the role of protozoa in aquifer systems has been examined by a relatively small number of studies. Given the pivotal role these organisms play in other aquatic environments, it is reasonable to assume that they play fundamental roles in the carbon and nutrient cycles of the subsurface. It is time to investigate which protozoan species are present, which bacteria they graze upon and the impact of protozoan grazing on the carbon and nutrient cycles in groundwater. The goal of this work is to utilize stable isotopes in combination with geochemical and microbial methods to study the effect of protozoa on nutrient regeneration rates and carbon remineralization in a subterranean estuary on Cape Cod MA. This work will use 13C-labeled substrates such as acetate to track the active bacterial and protozoan community. Sediment will be collected from the freshwater and saline end-members of the subterranean estuary and will be used to establish flow-through columns. These columns will be incubated with groundwater pumped from the appropriate site in the estuary to maintain the in situ salinity and ion composition. Groundwater will be amended with 13C-substrates. The movement of the isotopic label from substrate to organic matter will be monitored by isotope-ratio mass spectrometry of inorganic carbon (aqueous CO2 species), bulk organic carbon (TOC / DOC) and small organic molecules (volatile organic acids and amino acids). Incorporation of the label into microbial biomass will be assessed by examination of isotopically-labeled nucleic acids and phospholipid fatty acids (PLFAs). Active bacterial and protozoan species will be identified by their isotopically-labeled rDNA or rRNA sequence. The relative roles of protozoa and bacteria will be assessed by parallel column incubations with 1.0-um filtered and non-filtered groundwater. The proposed work is the first study, to our knowledge, that directly links protozoan community composition to nutrient regeneration and carbon remineralization in fresh and saline aquifers. This group of microbes is vastly under-studied and the results of this study have the potential to elucidate recycling processes outside the current paradigm of microbial activity in aquifer sediments. Furthermore, the methods developed here can be generally applied to ecological and biogeochemical studies in numerous environments, ranging from freshwater systems to marine sediments.