Richard A. Jahnke

Skidaway Institute of Oceanography

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Steven Emerson

University of Washington

D. B. Craven

Skidaway Institute of Oceanography

Clare E. Reimers

Oregon State University

Alexandra Rao

Université du Québec à Rimouski

James W. Ammerman

Stony Brook University

Philip N. Froelich

Duke University

Deborah Jahnke

Skidaway Institute of Oceanography

Jeffrey D. Schuffert

Brown University

Jean‐François Gaillard

Northwestern University

James R. Nelson

Minnesota Department of Transportation

Cooperative Institutions

Scripps Institution of Oceanography

University of California, San Diego

Centre National de la Recherche Scientifique

Skidaway Institute of Oceanography

Woods Hole Oceanographic Institution

University of Washington

Florida State University

University of Rhode Island

Oregon State University

Sorbonne Université

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A model of oxygen reduction, denitrification, and organic matter mineralization in marine sediments1

Limnology and Oceanography (1982)

Richard A. Jahnke Steven Emerson James W. Murray

Porewater nutrient profiles are sensitive indicators of organic matter degradation in sediments. To interpret these data, we have derived a kinetic model of oxygen reduction, nitrification, and denitrification which quantitatively relates the rates of oxygen reduction and denitrification to the depth separating these processes and the carbon oxidation rate. We have compared model profiles with porewater profiles of the sum of NO 2 − , NO 3 − , and NH 4 + (∑N) from both Atlantic and Pacific Ocean stations. Calculated rates of oxygen reduction and denitrification vary proportionally at these stations. Extrapolation along this relationship predicts a maximum in NO 3 − even where the nitrification zone is so thin that only a decrease from bottom water samples is measured with a 1–2‐cm sampling interval. The model also predicts that the maximum amount of organic matter that can be oxidized by denitrification is only 30% of that oxidized by oxygen respiration in the Pacific and only 13% in the Atlantic Ocean.

Simultaneous nitrification-denitrification

10.4319/lo.1982.27.4.0610

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Citations (170)

Carbonate-ion substitution in francolite: A new equation

Geochimica et Cosmochimica Acta (1990)

Jeffrey D. Schuffert Miriam Kastner Guy Emanuele Richard A. Jahnke

Fluorapatite

10.1016/0016-7037(90)90058-s

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Citations (75)

Organic carbon deposition on the North Carolina continental slope off Cape Hatteras (USA)

Deep Sea Research Part II Topical Studies in Oceanography (2002)

Carrie Thomas Neal E. Blair Marc J. Alperin Dave DeMaster Richard A. Jahnke

Deposition

Biogeochemistry

Carbon fibers

Seabed

Cape

10.1016/s0967-0645(02)00135-2

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Citations (42)

Coupling mercury methylation rates to sulfate reduction rates in marine sediments

Environmental Toxicology and Chemistry (1999)

Jeffrey King F. Michael Saunders Richard F. Lee Richard A. Jahnke

Abstract Anoxic slurry incubations were performed to examine the relationship between mercury methylation rates (MMR) and sulfate reduction rates (SRR) in salt marsh sediments from the southeastern United States. The MMR and SRR were similarly affected by temperature, addition of low-weight molecular organics, and microbial inhibitors. The MMR was at a maximum in the 12 h after inorganic mercury addition. Initial rates of Hg methylation are correlated with SRR. A significantly slower MMR observed after the initial 12 h following inorganic mercury addition suggested that sorption or precipitation reduced the availability of mercury for methylation. The MMR results for various concentrations of inorganic mercury indicate that saturation kinetics occur. Using this kinetic framework, a model for MMR based on SRR and inorganic Hg concentration was developed. This model was then used to predict the MMR reported in temperature and substrate/inhibitor experiments. The model provided a reasonable estimate of MMR observed in the initial 12 h of the slurry incubations. However, the sequestering of inorganic mercury into less reactive pools by sorption to surfaces or incorporation into other phases alters the amount of bioavailable Hg and hence MMR. Future models that assess the bioavailibility of Hg in the sediments must be developed to extend these observations to field sites.

Mercury

Methylmercury

Congener

10.1002/etc.5620180704

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Citations (182)

A free-vehicle benthic chamber instrument for sea floor studies

Deep Sea Research Part A Oceanographic Research Papers (1989)

Richard A. Jahnke Matthew B. Christiansen

Seabed

SCOOP

Vacuum chamber

10.1016/0198-0149(89)90011-3

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Citations (75)

Aquatic Geochemistry (2002)

Luís Felipe Hax Niencheski Richard A. Jahnke

10.1023/a:1024207220266

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Citations (38)

Evidence for enhanced phosphorus regeneration from marine sediments overlain by oxygen depleted waters

Geochimica et Cosmochimica Acta (1994)

Ellery D. Ingall Richard A. Jahnke

Continental Margin

10.1016/0016-7037(94)90033-7

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Citations (482)

Organic Carbon Preservation in the Present-Day Ocean: ABSTRACT

AAPG Bulletin (1996)

Richard A. Jahnke

Present day

Carbon fibers

10.1306/522b2f9d-1727-11d7-8645000102c1865d

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The flux and recycling of bioactive substances in the surface sediments of the deep basins off southern California

Richard A. Jahnke

We have used pore water gradients and in situ benthic flux chamber measurements to assess the total and down-core variations in the organic carbon remineralization rate. To augment standard pore water extractions, we developed techniques to extract pore water samples at 2mm sampling intervals, greatly improving our assessment of near- surface vertical gradients. In addition, much emphasis was placed on directly measuring the exchange of chemicals between the bottom waters and sediment pore waters via in situ benthic flux chamber incubations. The latter were performed with the MANOP bottom lander, and in later expeditions, the Benthic Experimental chamber Instrument (BECI). Results from these measurements were used to assess the several aspects of seafloor organic matter diagenesis.

Seafloor Spreading

Sediment–water interface

10.2172/7037149

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The fate of nitrogen and phosphorus at the land-sea margin of the North Atlantic Ocean

Biogeochemistry (1996)

S. W. Nixon James W. Ammerman Larry P. Atkinson V. M. Berounsky Gilles Billen

Continental Margin

10.1007/bf02179826

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Citations (712)