Oxygen-minimum zone sediments in the northeastern Arabian Sea Sea off Pakistan: a habitat for the bacterium Thioploca

Schmaljohann, Ralf, Drews, Manuela, Walter, S., Linke, Peter, von Rad, U. and Imhoff, Johannes F. (2001) Oxygen-minimum zone sediments in the northeastern Arabian Sea Sea off Pakistan: a habitat for the bacterium Thioploca Marine Ecology Progress Series, 211 . pp. 27-42.

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Abstract

Filamentous sulfur-oxidizing bacteria and geochemical parameters of sediments at the Makran accretionary wedge in the northeastern Arabian Sea off Pakistan were studied. The upper continental slope between 350 and 850 m water depth, which is in the center of the oxygen-minimum zone, is characterized by numerous sites of small-scale seeps of methane- and sulfide-charged porewater. White bacterial mats with diameters <1 m were discovered at the surface of these sites using a photo-TV sled. Seep sediments, as well as non-seep sediments, in the vicinity were characterized by the occurrence of the bacterium Thioploca in near-surface layers between 0 and 13 cm depth. Thioploca bundles were up to 20 mm in length and contained up to 20 filaments of varying diameters, between 3 and 75 µm. Up to 169 ind. cm-2 were counted. Maximum numbers occurred in the top 9 cm of sediment, which contained very low concentrations of soluble sulfide (<0.2 µM) and high amounts of elemental sulfur (up to 10 µmol cm-3). Moderate sulfate reduction activity (between 20 and 190 nmol cm-3 d-1) was detected in the top 10 cm of these sediments, resulting in a gradual downcore decrease of sulfate concentrations. CO2 fixation rates had distinct maxima at the sediment surface and declined to background values below 5 cm depth. The nutritional implications of the distinct morphology of Thioploca and of the geochemical setting are discussed and compared to other sites containing Thioploca communities.

Document Type: Article
Keywords: Thioploca; Beggiatoa; Arabian Sea; Cold seeps; Oxygen-minimum zone sediments; Filamentous sulfur-oxidizing bacteria; Sulfate reduction rates; CO2 fixation rates
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > GEOMAR > FB3 Marine Ecology > FB3-MI Marine Microbiology
Refereed: Yes
ISSN: 0171-8630
Expeditions/Models:
Date Deposited: 10 Sep 2008 22:10
Last Modified: 20 Dec 2016 08:05
URI: http://eprints.uni-kiel.de/id/eprint/3388

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