Early diagenesis in the sediments of the Congo deep-sea fan dominated by massive terrigenous deposits: Part III – Sulfate- and methane- based microbial processes
|Author(s)||Pastor Lucie1, Toffin Laurent2, 3, 4, Decker Carole1, Olu Karine1, Cathalot Cecile5, Lesongeur Francoise2, 3, 4, Caprais Jean-Claude1, Bessette Sandrine2, 3, 4, Brandily Christophe1, Taillefert M.6, Rabouille C.7, 8|
|Affiliation(s)||1 : IFREMER, Ctr Bretagne, Lab Environm Profond, REM EEP, F-29280 Plouzane, France.
2 : IFREMER, Ctr Bretagne, REM EEP, Lab Microbiol Environm Extremes, F-29280 Plouzane, France.
3 : Univ Bretagne Occidentale, Lab Microbiol Environm Extremes, UMR6197, Technopole Brest Iroise, Plouzane, France.
4 : CNRS, Lab Microbiol Environm Extremes, UMR6197, Technopole Brest Iroise, Plouzane, France.
5 : IFREMER, Ctr Bretagne, REM EEP, Lab Cycles Geochim & Ressources, F-29280 Plouzane, France.
6 : Georgia Inst Technol, Sch Earth & Atmospher Sci, Atlanta, GA 30332 USA.
7 : UMR 8212 CEA CNRS UVSQ, Lab Sci Climat & Environm, Av Terrasse, F-91190 Gif Sur Yvette, France.
8 : IPSL, Av Terrasse, F-91190 Gif Sur Yvette, France.
|Source||Deep-sea Research Part Ii-topical Studies In Oceanography (0967-0645) (Pergamon-elsevier Science Ltd), 2017-08 , Vol. 142 , P. 139-150|
|WOS© Times Cited||10|
|Abstract||Geochemical profiles (SO42-, H2S, CH4, δ13CH4) and phylogenetic diversity of Archaea and Bacteria from two oceanographic cruises dedicated to the lobes sediments of the Congo deep-sea fan are presented in this paper. In this area, organic-rich turbidites reach 5000 m and allow the establishment of patchy cold-seep-like habitats including microbial mats, reduced sediments, and vesicomyid bivalves assemblages. These bivalves live in endosymbiosis with sulfur-oxidizing bacteria and use sulfides to perform chemosynthesis. In these habitats, unlike classical abyssal sediments, anoxic processes are dominant. Total oxygen uptake fluxes and methane fluxes measured with benthic chambers are in the same range as those of active cold-seep environments, and oxygen is mainly used for reoxidation of reduced compounds, especially in bacterial mats and reduced sediments. High concentrations of methane and sulfate co-exist in the upper 20 cm of sediments, and evidence indicates that sulfate-reducing microorganisms and methanogens co-occur in the shallow layers of these sediments. Simultaneously, anaerobic oxidation of methane (AOM) with sulfate as the electron acceptor is evidenced by the presence of ANMEs (ANaerobic MEthanotroph). Dissolved sulfide produced through the reduction of sulfate is reoxidized through several pathways depending on the habitat. These pathways include vesicomyid bivalves uptake (adults or juveniles in the bacterial mats habitats), reoxidation by oxygen or iron phases within the reduced sediment, or reoxidation by microbial mats. Sulfide uptake rates by vesicomyids measured in sulfide-rich sea water (90 ± 18 mmol S m-2 d-1) were similar to sulfide production rates obtained by modelling the sulfate profile with different bioirrigation constants, highlighting the major control of vesicomyids on sulfur cycle in their habitats.|