Effect of Sediment Gas Voids and Ebullition on Benthic Solute Exchange

Flury, Sabine; Glud, Ronnie N.; Premke, Katrin; Mcginnis, Daniel Frank

doi:10.1021/acs.est.5b01967

Cited by 30 publications

(26 citation statements)

References 37 publications

(96 reference statements)

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“…A large number of porewater profile measurements at different depths and seasons are thus required to reliably quantify average diffusive CH 4 fluxes. This might be facilitated by novel measurement techniques such as porewater sampling by capillary electrophoresis (Torres et al ), but especially in bubbling sediments, the determination of diffusive fluxes remains a difficult task (Flury et al ; Tyroller et al ).…”

Section: Discussionmentioning

confidence: 99%

Role of gas ebullition in the methane budget of a deep subtropical lake: What can we learn from process‐based modeling?

Schmid

Ostrovsky

Mcginnis

2017

Limnology & Oceanography

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We analyzed the processes affecting the methane (CH 4 ) budget in Lake Kinneret, a deep subtropical lake, using a suite of three models: (1) a bubble model to determine the fate of CH 4 bubbles released from the sediment; (2) the one-dimensional physical lake model Simstrat to calculate the mixing dynamics; and (3) a biogeochemical model implemented in Aquasim to quantify the CH 4 sources and sinks. The key pathways modeled include diffusive and bubble release of CH 4 from the sediment, aerobic CH 4 oxidation, and atmospheric gas exchange. The temporal and spatial dynamics of dissolved CH 4 concentrations observed in the lake during 3 years could be well represented by the combined models. Remarkably, the relative contributions of ebullition and diffusive transport to the accumulation of CH 4 in the hypolimnion during the stratified period could not be accurately constrained based only on the observed evolution of CH 4 concentrations in the water column. Importantly, however, our analysis showed that most ($99%) of the CH 4 supplied to the water column by bubble dissolution and diffusive transport from the sediment is aerobically oxidized, whereas a substantial fraction ($60%) of the sediment-released bubble CH 4 is directly transported to the atmosphere. Ebullition is thus responsible for the bulk of the emissions from Lake Kinneret to the atmosphere. Therefore, as in all freshwaters, ebullition quantification is crucial for accurately assessing CH 4 emissions to the atmosphere. This task remains challenging due to high spatio-temporal variability, but combining in situ measurements with a process-based modeling can help to better constrain flux estimates.

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Section: Discussionmentioning

confidence: 99%

Role of gas ebullition in the methane budget of a deep subtropical lake: What can we learn from process‐based modeling?

Schmid

Ostrovsky

Mcginnis

2017

Limnology & Oceanography

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“…While bubbles in cohesive sediment due to methane actually inhibit diffusion of other solutes to the water32, it is suggested that Chaoborus spp. can, through bioturbation, significantly enhance solute flux from sediment to the water column and subsequently increase lake internal loading3.…”

Section: Discussionmentioning

confidence: 99%

Porewater methane transport within the gas vesicles of diurnally migrating Chaoborus spp.: An energetic advantage

Mcginnis

Flury

Tang

et al. 2017

Sci Rep

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Diurnally-migrating Chaoborus spp. reach populations of up to 130,000 individuals m−2 in lakes up to 70 meters deep on all continents except Antarctica. Linked to eutrophication, migrating Chaoborus spp. dwell in the anoxic sediment during daytime and feed in the oxic surface layer at night. Our experiments show that by burrowing into the sediment, Chaoborus spp. utilize the high dissolved gas partial pressure of sediment methane to inflate their tracheal sacs. This mechanism provides a significant energetic advantage that allows the larvae to migrate via passive buoyancy rather than more energy-costly swimming. The Chaoborus spp. larvae, in addition to potentially releasing sediment methane bubbles twice a day by entering and leaving the sediment, also transport porewater methane within their gas vesicles into the water column, resulting in a flux of 0.01–2 mol m−2 yr−1 depending on population density and water depth. Chaoborus spp. emerging annually as flies also result in 0.1–6 mol m−2 yr−1 of carbon export from the system. Finding the tipping point in lake eutrophication enabling this methane-powered migration mechanism is crucial for ultimately reconstructing the geographical expansion of Chaoborus spp., and the corresponding shifts in the lake’s biogeochemistry, carbon cycling and food web structure.

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“…Furthermore, ebullition could also partially explain the stochastic nature of the water column CH 4 concentrations observed in the archipelago in this study. Not only does ebullition commonly display high spatiotemporal variability (e.g., Scandella et al 2016), it also has been shown to enhance diffusive sedimentary fluxes by making the sediment more porous (Flury et al 2015).…”

Section: Potential Role Of Ebullitionmentioning

confidence: 99%

Legacy Effects of Eutrophication on Modern Methane Dynamics in a Boreal Estuary

Myllykangas

Hietanen

Jilbert

2019

Estuaries and Coasts

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Estuaries are important conduits between terrestrial and marine aquatic systems and function as hot spots in the aquatic methane cycle. Eutrophication and climate change may accelerate methane emissions from estuaries, causing positive feedbacks with global warming. Boreal regions will warm rapidly in the coming decades, increasing the need to understand methane cycling in these systems. In this 3-year study, we investigated seasonal and spatial variability of methane dynamics in a eutrophied boreal estuary, both in the water column and underlying sediments. The estuary and the connected archipelago were consistently a source of methane to the atmosphere, although the origin of emitted methane varied with distance offshore. In the estuary, the river was the primary source of atmospheric methane. In contrast, in the adjacent archipelago, sedimentary methanogenesis fueled by eutrophication over previous decades was the main source. Methane emissions to the atmosphere from the study area were highly variable and dependent on local hydrodynamics and environmental conditions. Despite evidence of highly active methanogenesis in the studied sediments, the vast majority of the upwards diffusive flux of methane was removed before it could escape to the atmosphere, indicating that oxidative filters are presently still functioning regardless of previous eutrophication and ongoing climate change.

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Effect of Sediment Gas Voids and Ebullition on Benthic Solute Exchange

Cited by 30 publications

References 37 publications

Role of gas ebullition in the methane budget of a deep subtropical lake: What can we learn from process‐based modeling?

Role of gas ebullition in the methane budget of a deep subtropical lake: What can we learn from process‐based modeling?

Porewater methane transport within the gas vesicles of diurnally migrating Chaoborus spp.: An energetic advantage

Legacy Effects of Eutrophication on Modern Methane Dynamics in a Boreal Estuary

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