Gutzmann, E.

Pfannkuche, Olaf

Schnell, J.

Sommer, Stefan

English

OceanRep

Geophysical Research Abstracts, Vol. 9, 06361, 2007SRef-ID: 1607-7962/gra/EGU2007-A-06361© European Geosciences Union 2007Sediments hosting gas hydrates – oases for metazoanmeiofauna?S. Sommer, E. Gutzmann, J. Schnell, O. PfannkucheLeibniz Institute of Marine Sciences, IFM –GEOMAR, Germanyssommer@ifm-geomar.de / Fax: +49 431-6002911 / Phone: +49 431-6002119The effect of methane seepage from sediments hosting shallow gas hydrates on stand-ing stocks, distribution patterns and 13/12C/15/14N isotopic composition of meioben-thic organisms, with particular respect to nematoda and rotifera, was studied at about800 m water depth at Hydrate Ridge, Cascadia subduction zone, off Oregon. Thepresence of shallow gas hydrates, buried only a few tens of centimetres below thesediment surface was indicated by extensive bacterial mats of chemosynthetic Beg-giatoa sp. and clam fields of the bivalve mollusk Calyptogena sp. Mean abundancesof meiobenthic organisms integrated over the upper 10 cm of the sediment were high-est (1294 ind10cm−2) at clam fields, closely followed by control sediments least af-fected by gas hydrates (1199 ind10cm−2) and lowest in sediments covered with bac-terial mats (762 ind10cm−2). Average meiobenthic biomass was highest at the clamfield site (262.2 µgC 10cm−2), 210.4 µgC 10cm−2 at the control siteand very lowin sediments covered with bacterial mats (61.4 µgC 10cm−2). The dominant taxa ofmeiobenthic organisms at the investigated sites were nematodes and, unexpectedly,rotifera that are almost unknown from the deep marine habitat. In terms of abundance,it is a rotifera dominated meiobenthic community in gas hydrate influenced sedimentswhereas a nematode dominated community prevails in control sediments. The spa-tial distribution of nematodes and rotifers is likely to be determined by competitionand/or predation, and by the high adaptive capability of rotifers to highly sulphidic andanoxic conditions. The stable C isotopic composition of nematodes clearly indicatesthe contribution of chemosynthetically produced organic carbon to their nutrition atthe hydrate sites. However, estimates of the nematode population carbon turnover inrelation to the bulk organic carbon supply indicate that in contrast to nematode com-munities in other cold seep environments the meiobenthos in the studied gas hydratecontaining sediments do not benefit from the excess availability of organic carbonvia the chemoautotrophic food web. The tolerance to withstand severely deleteriousenvironmental conditions caused by reduced oxygen availability and extremely highsulphide fluxes might be exhausted in nematodes and other meiobenthic organismsexcept rotifers.

Sediments hosting gas hydrates - oases for metazoan meiofauna?

Abstract

Similar works

Full text

Available Versions

OceanRep