Short-term and seasonal variability of oxygen fluxes at the sediment–water interface in a riverine lake

Murniati, Erni; Geissler, Sebastian; Lorke, Andreas

doi:10.1007/s00027-014-0362-7

Cited by 19 publications

(19 citation statements)

References 53 publications

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“…In the absence of bioturbation, O2 transport into the sediment is limited by a DBL. The thickness of the DBL and, therefore the O2 flux, is 401 modulated by bottom boundary-layer turbulence driven by large-scale flows in the respective 402 aquatic system (Lorke et al 2003, Murniati et al 2015. The DBL thickness and 403 corresponding sediment-water fluxes of O2 observed in the control tank without chironomids FWS MS 17-049 19 (T0) were in the range of those values observed in a lake during periods of weak hydrodynamic forcing (Bryant et al 2010).…”

Section: Discussionmentioning

confidence: 83%

Effects of bioirrigation on the spatial and temporal dynamics of oxygen above the sediment–water interface

et al. 2017

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Burrow ventilation by tube-dwelling benthic animals affects solute exchange between sediments and water by 2 means. Drawing of O2-rich water into the burrow increases O2 availability in the sediment and stimulates biogeochemical and microbial processes, whereas flushing of the burrow creates a 3-dimensional flow field above the burrow, which induces mixing. Previous studies have revealed the role of the diffusive boundary layer (DBL) thickness on the exchange of solutes between the sediment and overlying water. Mapping the O2 gradient 24 within the DBL is a challenging task in the presence of benthic faunal activities. We used a novel 25 lifetime-based laser induced fluorescence (τLIF) technique that enables unobstructed 26 observations of spatial and temporal O2 dynamics above burrows inhabited by midge larvae 27 (Chironomus plumosus). We observed instantaneous plumes of O2-depleted water released from the outlet of the burrows and drawdown of O2-rich water above the inlet caused by peristaltic pumping of C. plumosus larvae. Vertical O2 gradients changed dynamically during burrow 30 ventilation relative to in a control tank without animals. The advective transport of O2 above the opening caused by burrow ventilation degraded the O2 concentration gradient. For a range of larvae densities that is frequently observed in ponds and lakes, the advective transport caused by burrow ventilation was the dominant transport mechanism.

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Section: Discussionmentioning

confidence: 83%

Effects of bioirrigation on the spatial and temporal dynamics of oxygen above the sediment–water interface

et al. 2017

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“…Clark-type oxygen microelectrodes used for eddy covariance typically have response times (t 90% ) of 0.2 to 0.5 s Attard et al, 2015;Donis et al, 2015). Newer optical sensors that have been developed in recent years have comparable or somewhat longer response times of 0.2 to 0.8 s (Chipman et al, 2012;Murniati et al, 2015;Berg et al, 2015). This means that the time series of the two key variables from which eddy fluxes are derived, the vertical velocity and oxygen concentration, are never perfectly aligned in time.…”

Section: Formulation Of Problemmentioning

confidence: 99%

Technical note: Time lag correction of aquatic eddy covariance data measured in the presence of waves

et al. 2015

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Abstract. Extracting benthic oxygen fluxes from eddy covariance time series measured in the presence of surface gravity waves requires careful consideration of the temporal alignment of the vertical velocity and the oxygen concentration. Using a model based on linear wave theory and measured eddy covariance data, we show that a substantial error in flux can arise if these two variables are not aligned correctly in time. We refer to this error in flux as the time lag bias. In one example, produced with the wave model, we found that an offset of 0.25 s between the oxygen and the velocity data produced a 2-fold overestimation of the flux. In another example, relying on nighttime data measured over a seagrass meadow, a similar offset reversed the flux from an uptake of −50 mmol m −2 d −1 to a release of 40 mmol m −2 d −1 . The bias is most acute for data measured at shallow-water sites with short-period waves and low current velocities. At moderate or higher current velocities (> 5-10 cm s −1 ), the bias is usually insignificant. The widely used traditional time shift correction for data measured in unidirectional flows, where the maximum numerical flux is sought, should not be applied in the presence of waves because it tends to maximize the time lag bias or give unrealistic flux estimates. Based on wave model predictions and measured data, we propose a new time lag correction that minimizes the time lag bias. The correction requires that the time series of both vertical velocity and oxygen concentration contain a clear periodic wave signal. Because wave motions are often evident in eddy covariance data measured at shallow-water sites, we encourage more work on identifying new time lag corrections.

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“…Turbulent mixing in the bottom-boundary layer, however, is more energetic and less affected by density stratification. Nevertheless, eddy correlation (EC) flux measurements have been increasingly used to estimate sediment-water fluxes of dissolved oxygen (DO) [e.g., Berg et al, 2003;Murniati et al, 2015;Reimers et al, 2012].…”

Section: Introductionmentioning

confidence: 99%

Mixing efficiency in the thermocline of lakes observed from eddy correlation flux measurements

Weck

Lorke

2017

JGR Oceans

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Vertical mixing in the thermocline of lakes is poorly understood and most of the current knowledge is based on ex situ methods like laboratory measurements and simulations. Here we used the eddy correlation technique (EC) to directly measure oxygen and buoyancy fluxes in the thermocline of two lakes (Lake Scharmützelsee and Lake Arendsee in 2012 and 2013, respectively). Additionally, sets of temperature microstructure profiles (SCAMP) were measured during the EC deployments. We used these data to quantify the mixing efficiency as well as the turbulent diffusivity. The derived turbulent diffusivities from EC for the Prandtl number of DO were one order of magnitude higher than predicted by commonly applied parameterization, while the diffusivities for the Prandtl number of heat confirmed the parameterization. The results from EC and SCAMP showed strong differences which we attribute to the fact that SCAMP measurements reflect snapshots of the instantaneous turbulence field while EC provides a temporal average of the prevailing turbulence. Finally, we discuss problems of the EC and the inertial dissipation method in a strongly stratified environment and propose how they could be improved to resolve the full temporal variability of mixing in thermoclines.

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Short-term and seasonal variability of oxygen fluxes at the sediment–water interface in a riverine lake

Cited by 19 publications

References 53 publications

Effects of bioirrigation on the spatial and temporal dynamics of oxygen above the sediment–water interface

Effects of bioirrigation on the spatial and temporal dynamics of oxygen above the sediment–water interface

Technical note: Time lag correction of aquatic eddy covariance data measured in the presence of waves

Mixing efficiency in the thermocline of lakes observed from eddy correlation flux measurements

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