Variable sediment oxygen uptake in response to dynamic forcing.

Bryant, Lee D., Lorrai, Claudia, McGinnis, Daniel, Brand, Andreas, Wüest, Alfred and Little, John C. (2010) Variable sediment oxygen uptake in response to dynamic forcing. Open Access Limnology and Oceanography, 55 (2). pp. 950-964. DOI 10.4319/lo.2010.55.2.0950.

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Abstract

Seiche-induced turbulence and the vertical distribution of dissolved oxygen above and within the sediment were analyzed to evaluate the sediment oxygen uptake rate (JO2), diffusive boundary layer thickness (δDBL), and sediment oxic zone depth (zmax) in situ. High temporal-resolution microprofiles across the sediment-water interface and current velocity data within the bottom boundary layer in a medium-sized mesotrophic lake were obtained during a 12-h field study. We resolved the dynamic forcing of a full 8-h seiche cycle and evaluated JO2 from both sides of the sediment-water interface. Turbulence (characterized by the energy dissipation rate, ε), the vertical distribution of dissolved oxygen across the sediment-water interface (characterized by δDBL and zmax), JO2, and the sediment oxygen consumption rate (RO2) are all strongly correlated in our freshwater system. Seiche-induced turbulence shifted from relatively active (ε = 1.2 × 10-8 W kg-1) to inactive (ε = 7.8 × 10-12 W kg-1). In response to this dynamic forcing, δDBL increased from 1.0 mm to the point of becoming undefined, zmax decreased from 2.2 to 0.3 mm as oxygen was depleted from the sediment, and JO2 decreased from 7.0 to 1.1 mmol m-2 d-1 over a time span of hours. JO2 and oxygen consumption were found to be almost equivalent (within ~ 5% and thus close to steady state), with RO2 adjusting rapidly to changes in JO2. Our results reveal the transient nature of sediment oxygen uptake and the importance of accurately characterizing turbulence when estimating JO2.

Document Type: Article
Research affiliation: OceanRep > GEOMAR > Applied R&D > Energy and CO₂ Sequestration Projects
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.4319/lo.2010.55.2.0950
ISSN: 0024-3590
Date Deposited: 24 Feb 2010 15:48
Last Modified: 23 Sep 2019 22:28
URI: http://oceanrep.geomar.de/id/eprint/7359

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