Ankit Yadav, Muneer Wani, Gaye Birgit, Lahajnar Niko, Bhattacharya Sharmila, Bulbul Mehta, Jehangir Arshid, Anoop Ambili, Mishra Praveen K
Indian Institute of Science Education and Research, Mohali, 140306, India.
University of Kashmir, Srinagar, India.
Environ Res. 2022 Apr 1;205:112409. doi: 10.1016/j.envres.2021.112409. Epub 2021 Nov 26.
The sources and state of sedimentary organic matter (SOM) in fresh water aquatic systems are important to understand the carbon cycling in terrestrial environments. The composition of organic matter in the lake sediments demonstrates the physical and chemical condition of the lake ecosystems. However, the systematic and structured investigations focussed on to understand the source and fate of organic matters within eutrophic lakes is still far from clear. The present study is focusing on the implications of amino acids (AA), aliphatic hydrocarbons and bulk geochemical (C/N, δN) proxies to understand the distribution, sources and state of sedimentary organic matter in Ahansar Lake from Kashmir valley, India. The relatively low C/N ratios along with high AA contents indicate enhanced aquatic productivity in the lake system. Likewise, the dominance of the mid-chain monomethyl alkanes (MMAs), highly branched isoprenoids (HBIs), botryococcenes, steroids and triterpenoids suggest OM sourced from periphyton remains. Furthermore, the presence of C, C and C diagenetically altered steroids also reflects a major algal contribution. The spatial variability of P demonstrates their applicability as a proxy for the contribution of aquatic vegetation. The ratio of individual amino acids (oxic/anoxic ratio) and low Pr/Ph (pristane/phytane) values indicate anoxic nature of the current depositional environment. This also leads to significant organic matter preservation as revealed by amino acid indices (e.g., degradation index - DI and reactivity index - RI). These data collectively demonstrate the systematic investigation and comprehensive understanding of source of sedimentary organic matters and respective depositional condition via multiple indicators. Overall, understanding the OM molecular composition and its spatial heterogeneity in a lake system is important to better constrain the fate of organic carbon, and assess the pollution risks as well as adopt relevant management strategies.
淡水水生系统中沉积有机物质（SOM）的来源和状态对于理解陆地环境中的碳循环至关重要。湖泊沉积物中有机物质的组成反映了湖泊生态系统的物理和化学状况。然而，针对富营养化湖泊中有机物质的来源和归宿进行的系统且结构化的调查仍远未明晰。本研究聚焦于氨基酸（AA）、脂肪烃和整体地球化学（C/N、δN）指标，以了解印度克什米尔山谷阿汉萨尔湖沉积有机物质的分布、来源和状态。相对较低的C/N比值以及较高的AA含量表明湖泊系统中水生生产力增强。同样，中链单甲基烷烃（MMAs）、高度支链异戊二烯（HBIs）、葡萄藻烯、类固醇和三萜类化合物的主导地位表明有机物质源自周丛生物残体。此外，C、C和C经成岩作用改变的类固醇的存在也反映了藻类的主要贡献。P的空间变异性表明其作为水生植被贡献指标的适用性。单个氨基酸的比例（好氧/厌氧比例）和低Pr/Ph（姥鲛烷/植烷）值表明当前沉积环境具有缺氧性质。这也导致了如氨基酸指数（如降解指数-DI和反应性指数-RI）所揭示的显著有机物质保存。这些数据共同证明了通过多种指标对沉积有机物质来源和各自沉积条件进行的系统研究和全面理解。总体而言，了解湖泊系统中有机物质的分子组成及其空间异质性对于更好地限制有机碳的归宿、评估污染风险以及采取相关管理策略非常重要。
