Feedback of threshold via estimating sources and composition of sedimentary organic matter across trophic gradients in freshwater lakes.
Feedback of threshold via estimating sources and composition of sedimentary organic matter across trophic gradients in freshwater lakes.
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DOI：
10.1016/j.scitotenv.2014.08.113
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发表时间：
2014-12
期刊：
影响因子：
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通讯作者：
Xiaoguang Xu;Wei Li;Megumu Fujibayashi;M. Nomura;T. Sakamaki;O. Nishimura;Xianning Li
中科院分区：
文献类型：
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作者：
Xiaoguang Xu;Wei Li;Megumu Fujibayashi;M. Nomura;T. Sakamaki;O. Nishimura;Xianning Li
沉积有机质（SOM）的数量和质量的物质和能量流是至关重要的了解湖泊系统的现状和未来的发展，然而，表征有机质的来源和评估其相对贡献在不同的营养状态的湖泊所造成的人为影响是鲜为人知的。为了获得关于有机质来源及其沿着不同营养梯度的组成多样性的信息，采用脂肪酸生物标志物对中国和日本的4个淡水湖泊共31个采样点的有机质进行了分子水平分析。结果表明，根据脂肪酸谱，这些湖泊中的有机质由微藻、水生植物、陆生植物和细菌来源的有机物组成。散点图矩阵表现出这些来源之间的相关性，但是，只有陆生植物来源的有机碳是一个很好的预测沉积物TOC强，时空动态。冗余度分析表明，湖泊营养状态对土壤有机质的来源和组成有明显的影响。此外，湖泊营养状态的增强导致水生有机质对有机质库的贡献相对高于陆源，营养状态指数[TSI（TP）]与陆源/水生脂肪酸比值（TARFAratio）之间存在显著相关性。然而，这种变化趋势随着营养状态的升高而变得更加平缓，并通过TARFAratio的阈值（0.683）阻止了从外来优势状态到本地优势状态的状态转换。提出了一个概念图，该图突出了淡水湖泊中外来物源的普遍状态，并暗示了沉积有机物在淡水湖泊地球化学循环中的作用。
The quantity and quality of sedimentary organic matter (SOM) in relation to material and energy flows are crucial for understanding the current state and future development of lake systems, yet, characterization of organic matter sources and assessment of their relative contributions in different trophic-state lakes caused by anthropogenic impacts are scarcely known. In this study, for obtaining information concerning the source of SOM and its compositional diversity along different trophic gradients, a total of thirty-one sampling sites from four freshwater lakes located in China and Japan were performed by the molecular level analysis using source-specific fatty acid biomarkers. Results indicated that SOM in these lakes was composed of microalgae-, aquatic plant-, terrestrial plant- and bacteria-derived organic matters based on their fatty acid profiles. The scatter plot matrix exhibited correlations between these sources, however, only terrestrial plant-derived organic carbon was a well predictor for sediment TOC with strong, spatiotemporal dynamics. The source and composition of SOM were evidently influenced by lake trophic state with redundancy analysis. Moreover, increase of lake trophic state led to the relatively higher contribution of aquatic organic matter sources to SOM pool compared with terrigenous sources, as evidenced by significant correlations between the trophic state index [TSI (TP)] and the ratio of terrigenous to aquatic fatty acids (TARFAratio). Yet, this changing trend became more gradual with higher trophic state and prevented the occurrence of regime shift from allochthonous to autochthonous dominant state by a threshold (0.683) of TARFAratio. Together, a conceptual diagram was proposed, which highlighted the prevailing state of allochthonous source and implicated sedimentary organics in biogeochemistry cycle within freshwater lakes.