Collaborative Research: Constraining the sources, ages and alteration of dissolved and particulate lipids in estuarine and coastal organic matter

溶解有机碳（DOC）和颗粒有机碳（POC）生化分类的碳-14研究结果表明，碳水化合物和蛋白质来源于最近固定在有机物中的二氧化碳（即现代），而脂质部分是DOC和POC中最古老的成分（~103-104年BP）。脂质部分的年龄较长被认为是由于有机物来源、停留时间和/或反应性的差异。然而，脂质组分的年龄及其对海洋DOC和POC平均年龄的贡献还有待进一步研究。出于这个原因，来自威廉玛丽弗吉尼亚海洋科学学院的一位科学家和她来自俄亥俄州立大学的合作者计划研究特拉华湾陆海边界及其邻近沿海水域亲脂性有机物的来源（即陆源、海洋、自然、人为）、转化和命运。为了实现他们的目标，研究人员将对不同有机成分（即散装DOC和POC及其脂质成分）的保守与非保守行为及其同位素（delta14C和del13C）特征作为盐度的函数进行地球化学评估。这将在整个河口的尺度上提供每个组成部分的总体平均输入和汇的信息。此外，将在与河口混合和停留时间相关的时间尺度上进行对照培养实验，评估DOC、POC和脂质组分的光化学和微生物反应性。预计本研究将为研究亲脂性有机物对河口和沿海水域DOC和POC的年龄、反应性和循环的影响提供新的见解。就更广泛的影响而言，来自威廉玛丽弗吉尼亚学院海洋科学研究所的科学家计划让来自里约热内卢州立大学的研究生参与研究项目，从而在美国和巴西科学家之间建立合作关系。威廉和玛丽弗吉尼亚学院海洋科学研究所的一名研究生和俄亥俄州立大学的一名研究生将作为该项目的一部分得到支持和培训。

Results from carbon-14 studies of biochemical classes of dissolved organic carbon (DOC) and particulate organic carbon (POC) have shown that carbohydrate and protein derive from carbon dioxide that has been recently fixed into organic matter (i.e., modern in age), whereas the lipid fraction is the most highly aged (~103-104 yrs BP) component of both DOC and POC. The older age of the lipid fraction is believed to be due to differences in organic matter sources, residence times, and/or reactivity. However, more studies are needed to understand the age of the lipid fraction and its contribution to the average age of oceanic DOC and POC. For this reason, a scientist from the College of William and Mary Virginia Institute of Marine Science and her collaborator from Ohio State University plan to examine the sources (i.e., terrigenous, marine, natural, anthropogenic), transformations, and fate of lipophilic organic matter across the land-ocean boundary of Delaware Bay and its adjacent coastal waters. To attain their goal, the researcher will carry out a geochemical evaluation of the conservative vs. non-conservative behavior of different organic constituents (i.e., bulk DOC and POC and their lipid components) and their isotopic (delta14C and del13C) signatures as a function of salinity. This will provide information on the overall mean inputs and sinks of each constituent on the scale of the entire estuary. In addition, the photochemical and microbial reactivity of DOC, POC and lipid components will be evaluated in controlled incubation experiments on timescales relevant to estuarine mixing and residence times.It is anticipated that this study will provide new insights on how the lipophilic organic matter contributes to the age, reactivity, and cycling of DOC and POC in estuarine and coastal waters.In terms of the broader impacts, at no cost to the project, the scientist from the College of William and Mary Virginia Institute of Marine Science plans to involve graduate students from the Universidade do Estado do Rio de Janeiro in the research project, thereby building a collaboration between U.S. and Brazilian scientists. One graduate student from the College of William and Mary Virginia Institute of Marine Science and one graduate student from Ohio State University would be supported and trained as part of this project.