Butturini A, Herzsprung P, Lechtenfeld O J, Alcorlo P, Benaiges-Fernandez R, Berlanga M, Boadella J, Freixinos Campillo Z, Gomez R M, Sanchez-Montoya M M, Urmeneta J, Romaní A M
Department de Biologia Evolutiva, Ecologia y Ciencies Ambientals, Universitat de Barcelona, Diagonal 643, Barcelona, Catalonia 08028, Spain.
Department of Lake Research, Helmholtz Centre for Environmental Research (UZF), Magdeburg, Germany.
Water Res. 2022 Aug 1;221:118727. doi: 10.1016/j.watres.2022.118727. Epub 2022 Jun 8.
Hypersaline endorheic aquatic systems (H-SEAS) are lakes/shallow playas in arid and semiarid regions that undergo extreme oscillations in salinity and severe drought episodes. Although their geochemical uniqueness and microbiome have been deeply studied, very little is known about the availability and quality of dissolved organic matter (DOM) in the water column.. A H-SEAS from the Monegros Desert (Zaragoza, NE Spain) was studied during a hydrological wetting-drying-rewetting cycle. DOM analysis included: (i) a dissolved organic carbon (DOC) mass balance; (ii) spectroscopy (absorbance and fluorescence) and (iii) a molecular characterization with Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). The studied system stored a large amount of DOC and under the highest salinity conditions, salt-saturated waters (i.e., brines with salinity > 30%) accumulated a disproportionate quantity of DOC, indicating a significant in-situ net DOM production. Simultaneously, during the hydrological transition from wet to dry, the DOM pool showed strong alterations of it molecular composition. Spectroscopic methods indicated that aromatic and degraded DOM was rapidly replaced by fresher, relatively small, microbial-derived moieties with a large C/N ratio. FT-ICR-MS highlighted the accumulation of small, saturated and oxidized molecules (molecular O/C > 0.5), with a remarkable increase in the relative contribution of highly oxygenated (molecular O/C>0.9) compounds and a decrease of aliphatic and carboxyl-rich alicyclic moleculesThese results indicated that H-SEAS are extremely active in accumulating and processing DOM, with the notable release of organic solutes probably originated from decaying microplankton under large osmotic stress at extremely high salinities.
高盐内陆水系（H - SEAS）是干旱和半干旱地区的湖泊/浅洼地，其盐度会经历极端波动且会出现严重干旱期。尽管它们的地球化学独特性和微生物群落已得到深入研究，但对于水柱中溶解有机物（DOM）的可用性和质量却知之甚少。对来自西班牙东北部萨拉戈萨省莫内格罗斯沙漠的一个高盐内陆水系在一次水文湿润 - 干燥 - 再湿润循环期间进行了研究。DOM分析包括：（i）溶解有机碳（DOC）质量平衡；（ii）光谱分析（吸光度和荧光）以及（iii）利用傅里叶变换离子回旋共振质谱（FT - ICR - MS）进行分子表征。所研究的系统储存了大量的DOC，在盐度最高的条件下，盐饱和水体（即盐度>30%的卤水）积累了不成比例数量的DOC，表明存在显著的原位净DOM生成。同时，在从湿润到干燥的水文转变过程中，DOM库的分子组成发生了强烈变化。光谱方法表明，芳香族和降解的DOM迅速被更新鲜、相对较小、源自微生物且碳氮比大的部分所取代。FT - ICR - MS突出显示了小的、饱和的和氧化的分子（分子O/C>0.5）的积累，高度氧化（分子O/C>0.9）化合物的相对贡献显著增加，而富含脂肪族和羧基的脂环族分子减少。这些结果表明，高盐内陆水系在积累和处理DOM方面极其活跃，在极高盐度下的大渗透胁迫下，可能源自腐烂微浮游生物的有机溶质会大量释放。
