Origin, accumulation and fate of dissolved organic matter in an extreme hypersaline shallow lake

• DOI: 10.1016/j.watres.2022.118727
• Publication Date: 2022-06-08T00:30:11Z
• Authors: A. Butturini; P. Herzsprung; O.J. Lechtenfeld; P. Alcorlo; R. Benaiges-Ferna...; M. Berlanga; J. Boadella; Z. Freixinos Camp...; R.M. Gomez; M.M. Sanchez-Montoya; J. Urmeneta; A.M. Romaní
• Keywords: Biogeochemical Cycle

Hypersaline endorheic aquatic systems (H-SEAS) are lakes/shallow playas in arid and semiarid regions that undergo extreme oscillations salinity severe drought episodes. Although their geochemical uniqueness microbiome have been deeply studied, very little is known about the availability quality of dissolved organic matter (DOM) water column.. A H-SEAS from Monegros Desert (Zaragoza, NE Spain) was studied during a hydrological wetting-drying-rewetting cycle. DOM analysis included: (i) carbon (DOC) mass balance; (ii) spectroscopy (absorbance fluorescence) (iii) molecular characterization with Fourier-transform ion cyclotron resonance spectrometry (FT-ICR-MS). The system stored large amount DOC under highest conditions, salt-saturated waters (i.e., brines > 30%) accumulated disproportionate quantity DOC, indicating significant in-situ net production. Simultaneously, transition wet to dry, pool showed strong alterations it composition. Spectroscopic methods indicated aromatic degraded rapidly replaced by fresher, relatively small, microbial-derived moieties C/N ratio. FT-ICR-MS highlighted accumulation saturated oxidized molecules (molecular O/C 0.5), remarkable increase relative contribution highly oxygenated O/C>0.9) compounds decrease aliphatic carboxyl-rich alicyclic moleculesThese results extremely active accumulating processing DOM, notable release solutes probably originated decaying microplankton osmotic stress at high salinities.