| Abstract | Saline-alkaline lakes of the East African Rift are known to have an extremely high primary production supporting a potent carbon cycle. To date, a full description of carbon pools in these lakes is still missing. More specifically, there is not detailed information on the quality of dissolved organic matter (DOM), the main carbon energy source for heterotrophs prokaryotes. We report the first exhaustive description of DOM molecular properties in the water column of a meromictic saline-alkaline lake of the East African Rift. DOM availability, fate and origin were studied either quantitatively, in terms of dissolved organic carbon (DOC) and nitrogen (DON) or qualitatively, in terms of optical properties (absorbance) and molecular characterization of solid-phase extracted DOM (SPE-DOM) through negative electrospray ionization Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). DOM availability was high (DOC ~ 8.1 mM in surface waters) and meromixis imprinted a severe quantitative and qualitative change on DOM pool. At the surface, DOM was rich in aliphatic and moderately in aromatic molecules and thus mirroring autochthonous microbial production together with photodegradation. At the bottom changes were extreme: DOC increased up to 5 times (up to 50 mM) and, molecular signature drifted to saturated, reduced and non-aromatic DOM suggesting intense microbial activity within organic sediments. At the chemocline, DOC was retained indicating that this interface is a highly reactive layer in terms of DOM processing. These findings underline that saline-alkaline lakes of the East African Rift are carbon processing hot spots and their investigation may broaden our understanding of carbon cycling in inland waters at large. |
| Authors | Butturini A.[1], Herzsprung P.[2], Lechtenfeld O.J.[3], Venturi S.[7,8], Amalfitano S.[4], Vazquez E.[9], Pacini N.[6], Harper D.M.[5], Tassi F.[7,8], Fazi S.[4] |
| Text | 419624 2020 10.1016/j.watres.2020.115532 Scopus 2 s2.0 85079132510 African soda lake; CDOM; dissolved organic carbon; FT ICR MS; Meromixis Dissolved organic matter in a tropical saline alkaline lake of the East African Rift Valley. Butturini A. 1 , Herzsprung P. 2 , Lechtenfeld O.J. 3 , Venturi S. 7,8 , Amalfitano S. 4 , Vazquez E. 9 , Pacini N. 6 , Harper D.M. 5 , Tassi F. 7,8 , Fazi S. 4 1 Department de Biologia Evolutiva, Ecologia y Ciencies Ambientals, Universitat de Barcelona, Catalonia, Spain; 2 Department Lake Research, Helmholtz Centre for Environmental Research UFZ , Magdeburg, Germany; 3 Department Analytical Chemistry, Research Group BioGeoOmics, Helmholtz Centre for Environmental Research UFZ , Leipzig, Germany; 4 CNR e IRSA Water Research Institute, Via Salaria km 29.300 e CP10, 00015, Monterotondo, Rome, Italy; 5 Aquatic Ecosystem Services, Ltd., Drabblegate, Aylsham, Norfolk, United Kingdom; 6 Department of Environmental and Chemical Engineering, University of Calabria, Rende, Cosenza, Italy; 7 Department of Earth Sciences, University of Florence, Via G. La Pira 4, 50121, Florence, Italy; 8 CNR e IGG Institute of Geosciences and Earth Resources, Via G. La Pira 4, 50121, Florence, Italy; 9 INS Valeria Pujol, Premi a de Dalt, Barcelona, Spain Saline alkaline lakes of the East African Rift are known to have an extremely high primary production supporting a potent carbon cycle. To date, a full description of carbon pools in these lakes is still missing. More specifically, there is not detailed information on the quality of dissolved organic matter DOM , the main carbon energy source for heterotrophs prokaryotes. We report the first exhaustive description of DOM molecular properties in the water column of a meromictic saline alkaline lake of the East African Rift. DOM availability, fate and origin were studied either quantitatively, in terms of dissolved organic carbon DOC and nitrogen DON or qualitatively, in terms of optical properties absorbance and molecular characterization of solid phase extracted DOM SPE DOM through negative electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry FT ICR MS . DOM availability was high DOC 8.1 mM in surface waters and meromixis imprinted a severe quantitative and qualitative change on DOM pool. At the surface, DOM was rich in aliphatic and moderately in aromatic molecules and thus mirroring autochthonous microbial production together with photodegradation. At the bottom changes were extreme DOC increased up to 5 times up to 50 mM and, molecular signature drifted to saturated, reduced and non aromatic DOM suggesting intense microbial activity within organic sediments. At the chemocline, DOC was retained indicating that this interface is a highly reactive layer in terms of DOM processing. These findings underline that saline alkaline lakes of the East African Rift are carbon processing hot spots and their investigation may broaden our understanding of carbon cycling in inland waters at large. 173 Published version https //www.journals.elsevier.com/water research Dissolved organic matter in a tropical saline alkaline lake of the East African Rift Valley. BUTTURINI_pdf.pdf Articolo in rivista Pergamon Press. 0043 1354 Water research Oxf. Water research Oxf. Water res. Oxf. Water research. Oxf. francotassi TASSI FRANCO stefano.fazi FAZI STEFANO stefano.amalfitano AMALFITANO STEFANO |
