Spatial and Temporal Variability of Dissolved Organic Matter Molecular Composition in a Stratified Eutrophic Lake
Spatial and Temporal Variability of Dissolved Organic Matter Molecular Composition in a Stratified Eutrophic Lake
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DOI：
10.1029/2021jg006550
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发表时间：
2021-12
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通讯作者：
Stephanie M. Berg;Benjamin D. Peterson;K. McMahon;Christina K. Remucal
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作者：
Stephanie M. Berg;Benjamin D. Peterson;K. McMahon;Christina K. Remucal
溶解有机物（DOM）是初级生产者形成的有机碳和呼吸产生的二氧化碳（CO2）之间的中间体，使其成为水生生态系统碳循环的关键组成部分。它的组成影响矿化的途径。在这里，我们评估DOM组成的时间和深度的函数在湖门多塔，一个高产的富营养化湖泊，分层在温暖的月份，位于威斯康星州，麦迪逊。溶解有机碳的浓度和光学特性的73个样品收集在一个单一的位置在不同的深度内的水柱从6月至11月。通过傅里叶变换离子回旋共振质谱（FT-ICR MS）分析样品的子集，以在分子水平上研究DOM组成。从时间上看，在上层和下层都观察到更多氧化配方的增加。在表层，DOM公式与叶绿素浓度和光照强度之间的相关性表明，光化学反应有助于DOM的氧化。在浅水层，氧化还原条件和与沉积物的相互作用可能会影响时间的组成变化。我们的研究结果表明，DOM组成随深度而变化，在水柱中确定了更深的高度氧化的公式。然而，DOM组成的变化时间比水柱内的位置。这项工作对气候变化有影响，因为湖泊中的DOM光氧化代表了未充分研究的CO2向大气的通量。此外，湖泊富营养化正在增加，由于变暖的温度和这个数据集产生详细的分子信息DOM组成和处理在这样的湖泊。
Dissolved organic matter (DOM) is an intermediate between organic carbon formed by primary producers and carbon dioxide (CO2) produced through respiration, making it a key component of the carbon cycle in aquatic ecosystems. Its composition influences the routes of mineralization. Here, we evaluate DOM composition as a function of time and depth in Lake Mendota, a highly productive eutrophic lake that stratifies in warm months and is located in Madison, Wisconsin, USA. Dissolved organic carbon concentrations and optical properties are presented for 73 samples collected at a single location at varying depths within the water column from June to November. A subset of samples is analyzed by Fourier transform‐ion cyclotron resonance mass spectrometry (FT‐ICR MS) to investigate DOM composition at the molecular level. Temporally, increases in more oxidized formulas are observed in both the epilimnion and hypolimnion. At the surface, correlations between DOM formulas and both chlorophyll concentrations and light intensity show that photochemical reactions contribute to DOM oxidation. In the hypolimnion, redox conditions and interactions with sediments likely influence temporal compositional change. Our results show DOM composition varies with depth with more highly oxidized formulas identified deeper in the water column. However, DOM composition varies more temporally than by location within the water column. This work has implications for climate change as DOM photooxidation in lakes represents an understudied flux of CO2 to the atmosphere. Additionally, lake eutrophication is increasing due to warming temperatures and this data set yields detailed molecular information about DOM composition and processing in such lakes.