ABSTRACT

Lake sediments are the physical remnants of past allochthonous and autochthonous carbon and mineral inputs and therefore have the potential to illuminate both past terrestrial carbon cycling and within-lake biological productivity. However, there are currently no robust, rapid, and inexpensive methods to chemically characterise the organic matter (OM) components in lake sediments, which limits their utility for reconstructing past soil carbon export trends or trophic status. This study explores the use of 3D excitation–emission matrix (EEM) fluorescence spectroscopy of water extractable dissolved organic matter (WEDOM) from lake sediments as a method for reconstructing past soil dissolved organic matter (DOM) export and past lake water quality. Using contemporary lake sediments from 11 New Zealand lakes, we demonstrate that both overall WEDOM fluorescence and protein-like fluorescence intensity are strong functions of trophic status across lakes. We also demonstrate that protein-like fluorescence is a function of sedimentary total nitrogen concentrations in palaeo-sediments from a pristine, high-altitude lake (Adelaide Tarn). This approach has applications in the evaluation of the trophic status of infrequently monitored lakes and in palaeolimnology.

摘要

湖泊沉积物是过去外地和本土碳和矿物输入的物理残余物，因此有可能阐明过去的陆地碳循环和湖内生物生产力。然而，目前还没有可靠、快速和廉价的方法来化学表征湖泊沉积物中的有机物 (OM) 成分，这限制了它们在重建过去土壤碳输出趋势或营养状态方面的效用。本研究探讨了使用 3D 激发-发射矩阵 (EEM) 荧光光谱法对湖泊沉积物中的水可提取溶解有机物 (WEDOM) 作为重建过去土壤溶解有机物 (DOM) 输出和过去湖泊水质的方法。使用来自新西兰 11 个湖泊的当代湖泊沉积物，我们证明了整体 WEDOM 荧光和类蛋白质荧光强度都是跨湖泊营养状态的强函数。我们还证明蛋白质样荧光是来自原始高海拔湖泊（阿德莱德湖）的古沉积物中沉积物总氮浓度的函数。这种方法可用于评估不经常监测的湖泊的营养状况和古湖沼学。