Aquatic Sciences Meeting, Albuquerque 2001

SS06 Carbon Fluxes at Ocean and Large Lake Margins (Environmental Connections)

Date: Friday, February 16, 2001, Time: 11:30:00 AM

Location: Cochiti/Taos

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

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

Alperin, M, J, University of North Carolina, Chapel Hill, USA, alperin@marine.unc.edu

SULFATE REDUCTION RATES IN NORTH CAROLINA CONTINENTAL SLOPE SEDIMENTS

Over a timespan exceeding a decade, sulfate reduction measurements along a cross-slope transect off Cape Hatteras consistently yielded rates that decreased from about 1.2 mM/h near the interface to about 0.4 mM/h at 30 cm depth. Extension of these measurements to 2.5 m in 1993 showed that low, but measurable rates extend to these depths. On an areal basis, sulfate reduction rates of about 6 mmol/m2/d occur in the upper 30 cm of sediment while inclusion of the sediments to 2+ meters doubles this number. Other measures of organic carbon remineralization in these sediments (oxygen and carbon dioxide fluxes, carbon burial) are substantially lower than our integrated sulfate reduction rates. These discrepancies led us to the conclusion that there was a potential error in our rates due to a pressure effect from incubating samples on board rather than in situ. To test this, in 1996 we made in situ measurements utilizing an injection device deployed by submersible (Johnson Sea Link) for comparison with shipboard measurements. No significant differences were noted between the shipboard incubated samples and those incubated in situ at 750 m depth.

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Aquatic Sciences Meeting, Albuquerque 2001

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