Estimating turbulent diffusion in a benthic boundary layer

Holtappels, Moritz; Lorke, Andreas

doi:10.4319/lom.2011.9.29

Cited by 27 publications

(29 citation statements)

References 25 publications

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“…Obviously, the loglaw overestimates D T under the present conditions of low current velocity and cannot be applied here. This agrees well with the results of Holtappels and Lorke (2010) who compared several approaches to determine D T under variable conditions in the BBL and found that the log-law overestimated D T up to 2 orders of magnitude.…”

Section: From Relative To Absolute Fluxessupporting

confidence: 81%

“…3 and 4 give a first impression of how the concentration gradients in the BBL are tied to the flow field. However, the applicability of the log-law in natural environments is problematic (Lorke et al 2002;Holtappels and Lorke 2010). Boundary layer flows in oceans and lakes can differ from those in laboratory flumes as they may exhibit density stratification and nonstationary flow that result in nonlinear behavior of D T (such as the gray dashed profile in Fig.…”

Section: Theoretical Considerationsmentioning

confidence: 99%

“…However, because the turbulent regime in the bottom water affects the solute transport in the turbulent boundary layer (Holtappels and Lorke 2010) as well as in the diffusive boundary layer (Lorke et al 2003), a transient turbulent flow can result in variable solute concentrations at the sediment surface and, in the case of oxygen, in variable oxygen penetration depths and oxygen uptake rates (Glud et al 2007). Nevertheless, it is reasonable to assume that the short-term variability of oxygen uptake and nutrient release is nearly proportional, thus minimizing the variability of their flux ratio.…”

Section: − −mentioning

confidence: 99%

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Measurement and interpretation of solute concentration gradients in the benthic boundary layer

Holtappels

Kuypers

Schlüter

et al. 2011

Limnology & Ocean Methods

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The coastal ocean is characterized by high exchange rates of organic matter, oxygen, and nutrients between the sediment and the water column. The solutes that are exchanged between the sediment and the overlying water column are transported across the benthic boundary layer (BBL) by means of turbulent diffusion. Thus, solute concentration gradients in the BBL contain valuable information about the respective fluxes. In this study, we present the instrumentation and sampling strategies to measure oxygen and nutrient concentration gradients in the BBL. We provide the theoretical background and the calculation procedure to derive ratios of nutrient and oxygen fluxes from these concentration gradients. The noninvasive approach is illustrated at two sampling sites in the western Baltic Sea where nutrient and oxygen concentration gradients of up to 5 and 30 µM m -1 , respectively, were measured. Nutrient and oxygen flux ratios were used to establish a nitrogen flux balance between sediment and water column indicating that 20% and 50% of the mineralized nitrogen left the sediment in form of N 2 (station A and B, respectively). The results are supported by sediment incubation experiments of intact sediment cores, measuring denitrification rates, and oxygen uptake. The presented flux ratio approach is applicable without knowledge of turbulent diffusivities in the BBL and is, therefore, unaffected by non-steady-state current velocities and diffusivities.*Corresponding author: E-mail: mholtapp@mpi-bremen.de AcknowledgmentWe thank Bernd Schneider and Anne Loeffler (Leibniz Institute for Baltic Sea Research, Warnemünde) who provided ship time on RV Professor Albrecht Penck; Gaute Lavik for assistance in mass spectrometry and data analysis, G. Klockgether, M. Meyer, and J. Schmidt for analytical assistance, F. Wenzhoefer, H. Roy, and P. Faerber for technical assistance and the crews of RV Heinke and RV Professor Albrecht Penck for excellent collaboration. This study was funded through DFG-Research Center/Excellence Cluster, "The Ocean in the Earth System," and the Max Planck Society. DOI 10.4319/lom.2011.9.1 Limnol. Oceanogr.: Methods 9, 2011Methods 9, , 1-13 © 2011, by the American Society of Limnology and Oceanography, Inc. LIMNOLOGY and OCEANOGRAPHY: METHODSespecially the bottom water flow (Tengberg et al. 2005). The incubated water needs to be mixed artificially to simulate the flow of the bottom water. However, the degree of stirring can change the concentration of suspended particulate matter, the behavior of the macrofauna, or the porewater flow in permeable sediments.In recent years increasing attention has been paid to the water layer just above the sediment-the so called benthic boundary layer (BBL)-which is characterized by turbulent boundary layer flow (Dade et al. 2001). As this layer intimately links the sediment to the water column, it is well-suited for the noninvasive observation and quantification of concentration gradients and fluxes between sediment and water column. So far, only a few studies (R...

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Section: From Relative To Absolute Fluxessupporting

confidence: 81%

Section: Theoretical Considerationsmentioning

confidence: 99%

Section: − −mentioning

confidence: 99%

See 1 more Smart Citation

Measurement and interpretation of solute concentration gradients in the benthic boundary layer

Holtappels

Kuypers

Schlüter

et al. 2011

Limnology & Ocean Methods

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“…In principle, the measurement of mean O 2 concentration gradients in the benthic boundary layer (Holtappels et al, 2011a) in combination with the determination of the turbulent diffusion (Holtappels and Lorke, 2011b) allows estimating the O 2 uptake. However, low benthic O 2 uptakes as the ones measured in this study, result in small O 2 concentration gradients o5 Â 10 À 5 mmol m À 1 , which must be resolved during a long-term measurement.…”

Section: Final Remarksmentioning

confidence: 99%

Assessing benthic oxygen fluxes in oligotrophic deep sea sediments (HAUSGARTEN observatory)

Donis

Mcginnis

Holtappels

et al. 2016

Deep Sea Research Part I: Oceanographic Research Papers

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a b s t r a c tBenthic oxygen fluxes, an established proxy for total organic carbon mineralization, were investigated in oligotrophic deep sea sediments. We used three different in situ technologies to estimate the benthic oxygen fluxes at an Arctic deep sea site (2500 m depth, HAUSGARTEN observatory) with limiting conditions of low oxygen gradients and fluxes, low turbulence and low particle content in the benthic boundary layer. The resolved eddy covariance turbulent oxygen flux ( À 0. ). The agreement between these different techniques revealed that microbial-mediated oxygen consumption was dominant at this site. The average benthic flux equals a carbon mineralization rate of 4.3 g C m À 2 yr À 1 , which exceeds the annual sedimentation of particulate organic matter measured by sediment traps. The present study represents a detailed comparison of different in situ technologies for benthic flux measurements at different spatial scales in oligotrophic deep sea sediments. The use of eddy covariance, so far rarely used for deep sea investigations, is presented in detail.

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“…On one hand, the biofilm is diffusion-limited in its uptake of nutrients, and increased turbulence can reduce the thickness of the diffusive boundary layer. This can accelerate mass transfer from and toward the overlaying water column, 52,53 especially into and within biofilm voids. 54 This diffusion limitation may be one reason that very thick biofilm 54 or biofilm developing in waters with low flow velocity tends to develop filamentous structures called "streamers", which undulate to increase turbulence and thereby the transport rate of nutrients to the biofilm cells.…”

Section: Impact Of Hydrodynamic Regimementioning

confidence: 99%

The effect of light intensity and shear stress on microbial biostabilization and the community composition of natural biofilms

Schmidt¹,

Thom²,

Wieprecht³

et al. 2018

RRB

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Abstract:Biofilms constitute an important issue in microbial ecology, due to their high ecological and economic relevance, but the impact of abiotic conditions and microbial key players on the development and functionality of a natural biofilm is still little understood. This study investigated the effects of light intensity (LI) and bed shear stress (BSS) and the role of dominant microbes during the formation of natural biofilms and particularly the process microbial biostabilization. A comprehensive analysis of microbial biomass, extracellular polymeric substances produced, and the identification of dominant bacterial and algal species was correlated with assessment of biofilm adhesiveness/stability. LI and BSS impacted the biofilms in very different ways: biofilm adhesiveness significantly increased with LI and decreased with BSS. Moreover, microbial biomass and the functional organization of the bacterial community increased with LI, while the dynamics in the bacterial community increased with BSS. Most stable biofilms were dominated by sessile diatoms like Achnanthidium minutissimum or Fragilaria pararumpens and bacteria with either filamentous morphology, such as Pseudanabaena biceps, or a potential high capacity for extracellular polymeric-substance production, such as Rubrivivax gelatinosus. In contrast, microbes with high motility, such as Nitzschia fonticola, Pseudomonas fluorescens, and Caulobacter vibrioides, dominated the least adhesive biofilms. Their movement and potential antibiotic production could have had a disruptive impact on the biofilm matrix, which decreased its stability. This is the first study to unveil the link between abiotic conditions and resulting shifts in key microbial players to impact the ecosystem-service microbial biostabilization.

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Estimating turbulent diffusion in a benthic boundary layer

Cited by 27 publications

References 25 publications

Measurement and interpretation of solute concentration gradients in the benthic boundary layer

Measurement and interpretation of solute concentration gradients in the benthic boundary layer

Assessing benthic oxygen fluxes in oligotrophic deep sea sediments (HAUSGARTEN observatory)

The effect of light intensity and shear stress on microbial biostabilization and the community composition of natural biofilms

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