Identification of transport processes in bioirrigated muddy sediments by [18F]fluoride PET (Positron Emission Tomography)

Roskosch, Andrea; Lewandowski, Jörg; Bergmann, Ralf; Wilke, Florian; Brenner, Winfried; Buchert, Ralph

doi:10.1016/j.apradiso.2010.02.004

Cited by 6 publications

(20 citation statements)

References 8 publications

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“…Our model study has shown that the pumping activity of macrofauna such as C. plumosus in U‐shaped, open ended burrows can indeed induce pore water advection in the surrounding sediments and therefore corroborates the laboratory observations reported recently [ Roskosch et al ., ]. Roskosch et al .…”

Section: Discussionmentioning

confidence: 99%

“…Roskosch et al . [] reported an average expansion of the tracer front around the burrow by approximately 0.0078 m at the inlet and 0.009 m at the outlet in 10 h, resulting in a difference of 0.0012 m between both branches. Our model runs with the inert tracer shows a similar quantitative behavior.…”

Section: Discussionmentioning

confidence: 99%

“…A more in‐depth analysis of the experiment performed by Roskosch et al . [] using numerical models including intermittency of pumping and potential gradients in conductivity with an exact representation of burrow geometry is part of our ongoing research.…”

Section: Discussionmentioning

confidence: 99%

“…[6] Only recently, evidence was found that advective solute transport in the sediment may also occur around U-shaped burrows. Roskosch et al [2010b] performed a tracer study using 18-F fluoride positron emission tomography (PET) to investigate the influence of the pumping activity on the spreading of an inert tracer in the sediment surrounding a burrow inhabited by C. plumosus. It was found that the expansion of the tracer plume at the outlet branch of the burrow was faster than at the inlet branch.…”

Section: Introductionmentioning

confidence: 99%

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Advection around ventilated U‐shaped burrows: A model study

Brand

Lewandowski

Hamann

et al. 2013

Water Resources Research

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[1] Advective transport in the porous matrix of sediments surrounding burrows formed by fauna such as Chironomus plumosus has been generally neglected. A positron emission tomography study recently revealed that the pumping activity of the midge larvae can indeed induce fluid flow in the sediment. We present a numerical model study which explores the conditions at which advective transport in the sediment becomes relevant. A 0.15 m deep U-shaped burrow with a diameter of 0.002 m within the sediment was represented in a 3-D domain. Fluid flow in the burrow was calculated using the NavierStokes equation for incompressible laminar flow in the burrow, and flow in the sediment was described by Darcy's law. Nonreactive and reactive transport scenarios were simulated considering diffusion and advection. The pumping activity of the model larva results in considerable advective flow in the sediment at reasonable high permeabilities with flow velocities of up to 7.0 Â 10 À6 m s À1 close to the larva for a permeability of 3 Â 10 À12 m 2 . At permeabilities below 7 Â 10 À13 m 2 advection is negligible compared to diffusion. Reactive transport simulations using first-order kinetics for oxygen revealed that advective flux into the sediment downstream of the pumping larva enhances sedimentary uptake, while the advective flux into the burrow upstream of the larvae inhibits diffusive sedimentary uptake. Despite the fact that both effects cancel each other with respect to total solute uptake, the advection-induced asymmetry in concentration distribution can lead to a heterogeneous solute and redox distribution in the sediment relevant to complex reaction networks.Citation: Brand, A., J. Lewandowski, E. Hamann, and G. N€ utzmann (2013), Advection around ventilated U-shaped burrows: A model study, Water Resour.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Advection around ventilated U‐shaped burrows: A model study

Brand

Lewandowski

Hamann

et al. 2013

Water Resources Research

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“…However, in muddy sediments, advection has been neglected so far (e.g., Kristensen et al 2012). Roskosch et al (2010a) provided first indications that advection may be relevant close to U-shaped burrows of C. plumosus in muddy sediment. By using a three-dimensional model of a chironomid burrow, Brand et al (2013) showed that this effect indeed plays a role in moderately permeable sediments.…”

Section: Tube Modellingmentioning

confidence: 99%

Tube‐dwelling invertebrates: tiny ecosystem engineers have large effects in lake ecosystems

Hölker

Vanni

Kuiper

et al. 2015

Ecological Monographs

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136

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Abstract. There is ample evidence that tube-dwelling invertebrates such as chironomids significantly alter multiple important ecosystem functions, particularly in shallow lakes. Chironomids pump large water volumes, and associated suspended and dissolved substances, through the sediment and thereby compete with pelagic filter feeders for particulate organic matter. This can exert a high grazing pressure on phytoplankton, microorganisms, and perhaps small zooplankton and thus strengthen benthic-pelagic coupling. Furthermore, intermittent pumping by tube-dwelling invertebrates oxygenates sediments and creates a dynamic, three-dimensional mosaic of redox conditions. This shapes microbial community composition and spatial distribution, and alters microbe-mediated biogeochemical functions, which often depend on redox potential. As a result, extended hotspots of element cycling occur at the oxic-anoxic interfaces, controlling the fate of organic matter and nutrients as well as fluxes of nutrients between sediments and water. Surprisingly, the mechanisms and magnitude of interactions mediated by these organisms are still poorly understood. To provide a synthesis of the importance of tube-dwelling invertebrates, we review existing research and integrate previously disregarded functional traits into an ecosystem model. Based on existing research and our models, we conclude that tube-dwelling invertebrates play a central role in controlling water column nutrient pools, and hence water quality and trophic state. Furthermore, these tiny ecosystem engineers can influence the thresholds that determine shifts between alternate clear and turbid states of shallow lakes. The large effects stand in contrast to the conventional limnological paradigm emphasizing predominantly pelagic food webs. Given the vast number of shallow lakes worldwide, benthic invertebrates are likely to be relevant drivers of biogeochemical processes at regional and global scales, thereby mediating feedback mechanisms linked to climate change.

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