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MEPS 231:121-138 (2002)
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Abstract
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Macrofaunal community structure and sulfide flux at gas hydrate deposits from the Cascadia convergent margin, NE Pacific
Heiko Sahling1,*, Dirk Rickert1, Raymond W. Lee2, Peter Linke1, Erwin Suess1
1GEOMAR Forschungszentrum für Marine Geowissenschaften, Wischhofstraße 1-3, 24148 Kiel, Germany
2School of Biological Sciences, Washington State University, Pullman, Washington 99164-4236, USA
*E-mail: hsahling@geomar.de
ABSTRACT: Gas hydrates occur at the sediment surface on the southern summit of Hydrate Ridge, Cascadia convergent margin. The hydrates are found in mounds several meters in diameter and up to 2 m high, and are covered by sediment and mats of the
filamentous sulfur-oxidizing bacteria Beggiatoa. The mounds are surrounded by vesicomyid clams (Calyptogena pacifica, C. kilmeri), which in turn are encircled by solemyid bivalves (Acharax sp.). The zonation pattern of 3
species (Calyptogena spp. and Acharax sp., which harbor chemoautotrophic bacteria in their gills, and the chemoautotrophic Beggiatoa), is also reflected in a change in the entire community structure. Beggiatoa,
Calyptogena spp. and Acharax sp. are shown to be characteristic species for the different communities. The Beggiatoa community directly overlaying the gas hydrates consists of seep endemic species in high densities: gastropods
(Provanna laevis, P. lomana, Pyropelta corymba, Hyalogyrina sp. nov.), bivalves (Nuculana sp. nov.) and polychaetes (Ampharetidae, Polynoidae, Dorvilleidae). Based on pooled samples, the rarefaction curves show a
decrease in species diversity in the Beggiatoa and Calyptogena communities. The hydrogen sulfide gradients in the porewater of sediments below the different communities dominated by either Beggiatoa, Calyptogena spp. or
Acharax sp. vary by 3 orders of magnitude. The diffusive sulfide flux based on the measured sulfide concentration gradients is highest in Beggiatoa sp. communities (23 ± 13 mol m-2 yr-1), slightly less in
Calyptogena communities (6.6 ± 2.4 mol m-2 yr-1), and low in Acharax communities (0.05 ± 0.05 mol m-2 yr-1). The difference in the sulfide environment is a factor influencing the distribution
patterns of the chemoautotrophy-dependant and heterotrophic species at the deep-sea sediments containing gas hydrate.
KEY WORDS: Gas hydrate · Community structure · Biomass · Diversity · Sulfide · Chemoautotrophy · Cold seep
Full text in pdf format
Published in MEPS Vol.
231
(2002) on April 23
Print ISSN: 0171-8630; Online ISSN: 1616-1599.
Copyright © Inter-Research, Oldendorf/Luhe, 2002
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