Living benthic foraminifera in sediments influenced by gas hydrates at the Cascadia convergent margin, NE Pacific

Heinz, P., Sommer, Stefan, Pfannkuche, Olaf and Hemleben, C. (2005) Living benthic foraminifera in sediments influenced by gas hydrates at the Cascadia convergent margin, NE Pacific Marine Ecology Progress Series, 304 . pp. 77-89. DOI 10.3354/meps304077.

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Living (Rose Bengal stained) foraminifera in gas-hydrate-influenced sediments at the Cascadia convergent margin were investigated. Foraminiferal assemblages from the southern Hydrate Ridge and neighboring basins were compared in terms of abundances, vertical distribution, diversity, and species composition. At Hydrate Ridge, the presence of shallow gas hydrates and increased porewater sulfide concentrations was indicated by extensive bacterial mats of Beggiatoa sp. and clam beds of the bivalve mollusk Calyptogena sp., generating different biological zones. Living foraminifera were found in all biological zones, in sediment layers down to 5 cm. They showed highly variable densities within all zones. The average abundance of benthic foraminifera at Hydrate Ridge differs from neighboring basins. Average species diversities are comparable between biological zones, while the average number of species increases from bacterial mats to clam fields and surrounding sediments. Foraminifera can be characterized by 5 principal component communities which explain 97.3% of the variance of the live assemblages at the southern Hydrate Ridge and neighboring basins. At Hydrate Ridge, 2 foraminiferal zones can be distinguished: (1) an Uvigerina peregrina community which characterizes sediments covered with bacterial mats and clam fields; (2) a ?Spiroplectammina biformis community in the surrounding non-seep sediments. Foraminiferal assemblages in the neighboring Western and Eastern Basin differ from the Hydrate Ridge stations.

Document Type: Article
Keywords: Gas hydrates; Benthic foraminifera; Methane hydrate; Gas seeps; Hydrate Ridge; Cascadia subduction zone
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
Refereed: Yes
DOI etc.: 10.3354/meps304077
ISSN: 0171-8630
Date Deposited: 03 Dec 2008 16:51
Last Modified: 06 Jul 2012 14:53

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