Benthic fluxes and porewater concentration profiles of dissolved organic carbon in sediments from the North Carolina continental slope

Journal Article · Mon Feb 01 04:00:00 EST 1999 · Geochimica et Cosmochimica Acta

DOI:https://doi.org/10.1016/S0016-7037(99)00032-0· OSTI ID:355667

Alperin, M J; Martens, C S; Albert, D B; Suayah, I B; Benninger, L K ^[1]; Blair, N E ^[2]; Jahnke, R A ^[3]

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1. Univ. of North Carolina, Chapel Hill, NC (United States)
2. North Carolina State Univ., Raleigh, NC (United States). Dept. of Marine, Earth, and Atmospheric Sciences
3. Skidaway Inst. of Oceanography, Savannah, GA (United States)

Numerous studies of marine environments show that dissolved organic carbon (DOC) concentrations in sediments are typically tenfold higher than in the overlying water. Large concentration gradients near the sediment-water interface suggest that there may be a significant flux of organic carbon from sediments to the water column. Furthermore, accumulation of DOC in the porewater may influence the burial and preservation of organic matter by promoting geopolymerization and/or adsorption reactions. The authors measured DOC concentration profiles (for porewater collected by centrifugation and sipping) and benthic fluxes (with in situ and shipboard chambers) at two sites on the North Carolina continental slope to better understand the controls on porewater DOC concentrations and quantify sediment-water exchange rates. The authors also measured a suite of sediment properties (e.g., sediment accumulation and bioturbation rates, organic carbon content, and mineral surface area) that allow us to examine the relationship between porewater DOC concentrations and organic carbon preservation. Sediment depth-distributions of DOC from a downslope transect (300--1000 m water depth) follow a trend consistent with other porewater constituents ({summation}CO{sub 2} and SO{sub 4}{sup 2{minus}}) and a tracer of modern, fine-grained sediment, suggesting that DOC levels are regulated by organic matter remineralization. However, remineralization rates appear to be relatively uniform across the sediment transect. A simple diagenetic model illustrates that variations in DOC profiles at this site may be due to differences in the depth of the active remineralization zone, which in turn is largely controlled by the intensity of bioturbation. Comparison of porewater DOC concentrations, organic carbon burial efficiency, and organic matter sorption suggest that DOC levels are not a major factor in promoting organic matter preservation or loading on grain surfaces. The DOC benthic fluxes are difficult to detect, but suggest that only 2% of the dissolved organic carbon escapes remineralization in the sediments by transport across the sediment-water interface.

• Sponsoring Organization: National Science Foundation, Washington, DC (United States); USDOE, Washington, DC (United States)
• DOE Contract Number: FG02-95ER62073; FG02-92ER61413; FG02-95ER62036
• OSTI ID: 355667
• Journal Information: Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: 3-4 Vol. 63; ISSN 0016-7037; ISSN GCACAK
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
CONTINENTAL SLOPE
DIAGENESIS
DIFFUSION
DISSOLUTION
ECOLOGICAL CONCENTRATION
INTERFACES
INTERSTITIAL WATER
MATHEMATICAL MODELS
MINERALIZATION
NORTH CAROLINA
ORGANIC MATTER
SEDIMENTS
SURFACE WATERS