Efficiency and adaptability of the benthic methane filter at Quepos Slide cold seeps, offshore Costa Rica.

Steeb, Philip, Krause, Stefan, Linke, Peter , Hensen, Christian, Dale, Andrew W. , Nuzzo, Marianne and Treude, Tina (2015) Efficiency and adaptability of the benthic methane filter at Quepos Slide cold seeps, offshore Costa Rica. Open Access Biogeosciences (BG), 12 . pp. 6687-6706. DOI 10.5194/bg-12-6687-2015.

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Abstract

Large amounts of methane are delivered by fluids through the erosive forearc of the convergent margin offshore Costa Rica and lead to the formation of cold seeps at the sediment surface. Besides mud extrusion, numerous cold seeps are created by landslides induced by seamount subduction or fluid migration along major faults. Most of the dissolved methane reaching the seafloor at cold seeps is oxidized within the benthic microbial methane filter by anaerobic oxidation of methane (AOM). Measurements of AOM and sulfate reduction as well as numerical modeling of porewater profiles revealed a highly active and efficient benthic methane filter at Quepos Slide site; a landslide on the continental slope between the Nicoya and Osa Peninsula. Integrated areal rates of AOM ranged from 12.9 ± 6.0 to 45.2 ± 11.5 mmol m-2 d-1, with only 1 to 2.5% of the upward methane flux being released into the water column.

Additionally, two parallel sediment cores from Quepos Slide were used for in vitro experiments in a recently developed Sediment-F low-Through (SLOT) system to simulate an increased fluid and methane flux from the bottom of the sediment core. The benthic methane filter revealed a high adaptability whereby the methane oxidation efficiency responded to the increased fluid flow within 150–170 days. To our knowledge, this study provides the first estimation of the natural biogeochemical response of seep sediments to changes in fluid flow.

Document Type: Article
Keywords: Cold seeps, AOM, organoclastic sulfate reduction, sulfide oxidation, sediment-flow-through-system, Costa Rica
Research affiliation: OceanRep > The Future Ocean - Cluster of Excellence > FO-R07
OceanRep > The Future Ocean - Cluster of Excellence > FO-R09
OceanRep > SFB 574
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > The Future Ocean - Cluster of Excellence
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.5194/bg-12-6687-2015
ISSN: 1726-4170
Projects: Future Ocean
Expeditions/Models/Experiments:
Date Deposited: 03 Nov 2014 10:00
Last Modified: 19 Dec 2017 12:51
URI: http://oceanrep.geomar.de/id/eprint/25929

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