1. Differential manganese and iron recycling and transport in continental margin sediments of the Northern Gulf of Mexico
- Author
-
Laurie Bréthous, Bruno Bombled, Jordon S. Beckler, Martial Taillefert, Bruno Lansard, Shannon M. Owings, Anthony D. Boever, Eryn M. Eitel, Edouard Metzger, Benjamin P. Fields, Christophe Rabouille, School of Earth and Atmospheric Sciences [Atlanta], Georgia Institute of Technology [Atlanta], Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Harbor Branch Oceanographic Institute [Fort Pierce], Florida Atlantic University [Boca Raton], Océan et Interfaces (OCEANIS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Laboratoire de Planétologie et Géodynamique [UMR 6112] (LPG), Université d'Angers (UA)-Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), National Science Foundation, NSF: OCE-1438648 Office for Science and Technology of the Embassy of France in the United States, OST 2000007281, We would like to thank the captain and crew of the RV Savannah as well as Emily Buckley, Julien Richirt, and Andrew Stancil for help with sample collection and/or analysis. This research was supported by the National Science Foundation ( OCE-1438648 ) to M. Taillefert, EC2CO-DRIL MissRhoDia project to C. Rabouille, National Academies of Science, Engineering, and Medicine Gulf Research Program (Early Career Grant 2000007281 ) to J. Beckler, and the Chateaubriand Fellowship of the Office for Science & Technology of the Embassy of France in the United States awarded to S. Owings. Finally, we thank the editor and two anonymous reviewers for their insightful comments and suggestions which helped improve this paper significantly., Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
- Subjects
0106 biological sciences ,Anaerobic respiration ,010504 meteorology & atmospheric sciences ,Nepheloid layer ,chemistry.chemical_element ,Diagenetic processes ,Manganese ,Oceanography ,01 natural sciences ,River-dominated margins ,Continental slope sediments ,Continental margin ,Manganese and iron cycling ,River mouth ,Environmental Chemistry ,Mississippi delta ,Reduction ,0105 earth and related environmental sciences ,Water Science and Technology ,[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere ,geography ,geography.geographical_feature_category ,Continental shelf ,010604 marine biology & hydrobiology ,Sediment ,General Chemistry ,Sedimentation ,Sulfate ,Northern Gulf of Mexico ,chemistry ,13. Climate action ,Environmental chemistry ,Environmental science - Abstract
International audience; Pore water and solid phase geochemical profiles of sediment cores collected along two transects on the western and eastern sides of the Mississippi River mouth in the northern Gulf of Mexico were incorporated into a reactive transport model to determine the role of manganese and iron in the remineralization of carbon. Reactive transport model calculations indicate that sedimentation rates control the intensity of anaerobic carbon remineralization and select for the dominant anaerobic carbon remineralization pathways. Although sulfate reduction dominates the shelf station (65 m water depth), denitrification and microbial manganese reduction appear equally significant anaerobic respiration processes along the continental slope the closest to the Mississippi River, whereas microbial iron reduction does not represent an important process in these sediments. These findings suggest that the differential kinetics of manganese and iron redox transformations influence carbon remineralization processes on the continental slope. The fast kinetics of Fe2+ oxidation near the sediment-water interface and high sedimentation rates maintain Fe under the form of Fe(III) oxides and thermodynamically prevent sulfate reduction from dominating carbon remineralization processes on the slope, whereas the much slower Mn2+ oxygenation kinetics allows diffusion of Mn2+ across the sediment-water interface of the shelf station closest to the river mouth. Exposure to oxygenated bottom waters and entrainment within mobile muds typical of deltaic sediments during high riverine discharge likely promote the formation and downslope transport of Mn(III/IV) oxides within the nepheloid layer. This phenomenon appears to form a manganese ‘conveyor belt’ that selectively enriches Mn(III/IV) oxides relative to Fe(III) oxides in the deep sediment. In contrast, the intensity of anaerobic carbon remineralization processes along the eastern continental slope the farthest from the Mississippi River plume is much lower due to the low organic and lithogenic inputs, and denitrification dominates anaerobic respiration. Overall, these findings suggest that manganese cycling and its role in carbon remineralization processes in continental slope sediments exposed to large riverine inputs may be more important than previously considered.
- Published
- 2021