Aquatic Sciences Meeting, Albuquerque 2001

SS03 Chemosynthetic Processes at Oxic-Anoxic Interfaces (Environmental Connections)

Date: Tuesday, February 13, 2001, Time: 4:00:00 PM

Location: Mesilla

Lapham, L, L, University of North Carolina at Chapel Hill, Chapel Hill, USA, llapham@email.unc.edu

Chanton, J, P, Florida State University, Tallahassee, USA, jchanton@mailer.fsu.edu

Martens, C, S, University of North Carolina at Chapel Hill, Chapel Hill, USA, cmartens@email.unc.edu

Albert, D, B, University of North Carolina at Chapel Hill, Chapel Hill, USA, dan_albert@unc.edu

MAJOR ION AND DISSOLVED GAS CHEMISTRY OF SEDIMENTS AT A GAS HYDRATE SITE IN THE GULF OF MEXICO

In situ probe and core samples collected by submersible were utilized to investigate the major ion and dissolved gas chemistry of sediment porewaters surrounding exposed gas hydrates at two sites (27°46.9'N, 91°30.4'W and 27°44.7'N, 91°13.3'W) at approximately 550 meters depth on the Texas-Louisiana Shelf. A box core collected from a nearby, non-hydrate site from a surface ship was used as a reference sediment core (27°44.90'N, 91°16.63'W). Degassing of sediment cores during retrieval by submersible revealed near-saturated methane concentrations in the vicinity of both hydrate sites, however, in situ probe data suggest extreme heterogeneity in light hydrocarbon concentration distributions over distances of several meters. Preliminary major ion data suggest that Cl- concentrations exhibit subsurface concentration maxima and may be elevated by up to 5% above overlying seawater in some cores. Sulfate reduction rates were also measured as a function of depth. The raw data suggests that microbial sulfate reduction is enhanced in hydrate areas compared to the reference site, however, heterogeneity within hydrate containing areas is evident.

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Aquatic Sciences Meeting, Albuquerque 2001

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