Effects of low oxygen concentrations on aerobic methane oxidation in seasonally hypoxic coastal waters

Steinle, Lea; Maltby, Johanna; Treude, Tina; Kock, Annette; Bange, Hermann W.; Engbersen, Nadine; Zopfi, Jakob; Lehmann, Moritz F.; Niemann, Helge

doi:10.5194/bg-14-1631-2017

Cited by 82 publications

(91 citation statements)

References 65 publications

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“…In the North Sea, the stratification of the water column in the summer significantly reduces the diffusive methane flux, even at an active seep location . The values for a stratified fjord in the Baltic Sea are comparable to those of the North Sea (Steinle et al, 2017). However, in the southern North Sea, which has a mixed water column, very high methane fluxes (> 200 µmol m 2 d −1 ) are reported, which are mainly related to organic-rich sediments (Borges et al, 2016).…”

Section: Diffusive Methane Fluxmentioning

confidence: 53%

“…We measured an overall median MOX of 0. parts of the North Sea, respectively , 0.1 nmol L −1 d −1 at the surface of the central North Sea and 1 to 11 nmol L −1 d −1 for Eckernförde Bay in the Baltic Sea (Steinle et al, 2017). In polar waters, off the coast of Svalbard and unaffected by ebullition sites, values of 0.26 to 0.68 nmol L −1 d −1 (Mau et al, 2017) and 0.5 ± 1 nmol L −1 d −1 have been reported.…”

Section: Methanotrophic Activity and The Methanotrophic Populationmentioning

confidence: 94%

“…Another polar study conducted off the coast of Svalbard suggested that about 60 % of the methane in the bottom water is oxidised before it can mix with intermediate or surface water . For the coastal waters of the Baltic Sea, water column stratification is also crucial, much more methane is oxidised in a stratified water column compared to a mixed water column (Steinle et al, 2017). Our estimate of methane flux is a static one and does not take into account the currents and spreading of the freshwater plume.…”

Section: Role Of Microbial Methane Oxidation Vs Diffusive Methane Fluxmentioning

confidence: 99%

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Methane distribution and oxidation around the Lena Delta in summer 2013

et al. 2017

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Abstract. The Lena River is one of the largest Russian rivers draining into the Laptev Sea. The predicted increases in global temperatures are expected to cause the permafrost areas surrounding the Lena Delta to melt at increasing rates. This melting will result in high amounts of methane reaching the waters of the Lena and the adjacent Laptev Sea. The only biological sink that can lower methane concentrations within this system is methane oxidation by methanotrophic bacteria. However, the polar estuary of the Lena River, due to its strong fluctuations in salinity and temperature, is a challenging environment for bacteria. We determined the activity and abundance of aerobic methanotrophic bacteria by a tracer method and by the quantitative polymerase chain reaction. We described the methanotrophic population with a molecular fingerprinting method (monooxygenase intergenic spacer analysis), as well as the methane distribution (via a headspace method) and other abiotic parameters, in the Lena Delta in September 2013.The median methane concentrations were 22 nmol L −1 for riverine water (salinity (S) < 5), 19 nmol L −1 for mixed water (5 < S < 20) and 28 nmol L −1 for polar water (S > 20). The Lena River was not the source of methane in surface water, and the methane concentrations of the bottom water were mainly influenced by the methane concentration in surface sediments. However, the bacterial populations of the riverine and polar waters showed similar methane oxidation rates (0.419 and 0.400 nmol L −1 d −1 ), despite a higher relative abundance of methanotrophs and a higher estimated diversity in the riverine water than in the polar water. The methane turnover times ranged from 167 days in mixed water and 91 days in riverine water to only 36 days in polar water. The environmental parameters influencing the methane oxidation rate and the methanotrophic population also differed between the water masses. We postulate the presence of a riverine methanotrophic population that is limited by sub-optimal temperatures and substrate concentrations and a polar methanotrophic population that is well adapted to the cold and methane-poor polar environment but limited by a lack of nitrogen. The diffusive methane flux into the atmosphere ranged from 4 to 163 µmol m 2 d −1 (median 24). The diffusive methane flux accounted for a loss of 8 % of the total methane inventory of the investigated area, whereas the methanotrophic bacteria consumed only 1 % of this methane inventory. Our results underscore the importance of measuring the methane oxidation activities in polar estuaries, and they indicate a population-level differentiation between riverine and polar water methanotrophs.

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Section: Diffusive Methane Fluxmentioning

confidence: 53%

Section: Methanotrophic Activity and The Methanotrophic Populationmentioning

confidence: 94%

Section: Role Of Microbial Methane Oxidation Vs Diffusive Methane Fluxmentioning

confidence: 99%

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Methane distribution and oxidation around the Lena Delta in summer 2013

et al. 2017

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“…(Preisler et al, 2007). Seasonally hypoxic (dissolved oxygen < 63 µM) and anoxic (dissolved oxygen = 0 µM) events in the bottom water of Eckernförde Bay (Lennartz et al, 2014;Steinle et al, 2017) provide ideal conditions for anaerobic processes at the sediment surface.…”

Section: Introductionmentioning

confidence: 99%

Microbial methanogenesis in the sulfate-reducing zone of sediments in the Eckernförde Bay, SW Baltic Sea

et al. 2018

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Abstract. Benthic microbial methanogenesis is a known source of methane in marine systems. In most sediments, the majority of methanogenesis is located below the sulfatereducing zone, as sulfate reducers outcompete methanogens for the major substrates hydrogen and acetate. The coexistence of methanogenesis and sulfate reduction has been shown before and is possible through the usage of noncompetitive substrates by methanogens such as methanol or methylated amines. However, knowledge about the magnitude, seasonality, and environmental controls of this noncompetitive methane production is sparse. In the present study, the presence of methanogenesis within the sulfate reduction zone (SRZ methanogenesis) was investigated in sediments (0-30 cm below seafloor, cm b.s.f.) of the seasonally hypoxic Eckernförde

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“…In addition, water column stratification hampers upward transportation of subsurface CH 4 , affecting the biogeochemical cycling of CH 4 in the Baltic Sea and Black Sea (e.g., Schmale et al, 2010a,b). Also, the DO concentration plays an important role in modulating methanogen and methanotroph activities (e.g., Reeburgh, 2007;Steinle et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

Exploring Sources and Biogeochemical Dynamics of Dissolved Methane in the Central Bohai Sea in Summer

2020

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To clarify the sources and biogeochemical dynamics of dissolved methane (CH 4 ) in shallow-water coastal oceans, we investigated the concentrations, sea-to-air fluxes, and net cycling rate of CH 4 in the central Bohai Sea in summer 2018. During the survey, both summertime stratification and dissolved oxygen (DO) deficit were observed. In the surface layer, CH 4 concentration ([CH 4 ]) ranged from 3.08 to 10.27 nmol kg −1 . The average sea-to-air flux was estimated at 6.46 ± 3.32 µmol m −2 d −1 , indicating that the Bohai Sea serves as a source of atmospheric CH 4 . In the bottom layer, [CH 4 ] ranged from 4.29 to 31.04 nmol kg −1 . The downward increase in [CH 4 ] within the water column indicated substantial sources of CH 4 in the seafloor. Based on the complex relationship between the saturation ratio of CH 4 and DO, three types of CH 4 release from the seafloor were identified, including diagenesis of buried organic matter, natural leakage from geological settings, and anthropogenic release from offshore oil/gas development. The saturation ratios of CH 4 in bottom waters were positively correlated with the degree of stratification of the water column. Using a two-layer box model, sedimentary CH 4 release rates at two oxygen-deficient stations were estimated to be 56.0-60.8 µmol m −2 d −1 , which was much higher than the sea-to-air fluxes. The modeling results also indicated that the majority of seafloor released CH 4 (>90%) was consumed in the water column of this shallow-water coastal sea. This is the first comprehensive study on CH 4 cycling in the Bohai Sea. This work shows the indicative role of DO in identifying multiple CH 4 sources and highlights the dominance of water stratification and microbial consumption in local CH 4 dynamics. KEY POINTS -Dissolved CH 4 exhibited complex relations with oxygen in the Bohai Sea. -Three types of CH 4 sources from seafloor were identified. -Stratification hampered the upward transport of dissolved CH 4 . -Strengths of CH 4 cycling terms are quantified.

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Effects of low oxygen concentrations on aerobic methane oxidation in seasonally hypoxic coastal waters

Cited by 82 publications

References 65 publications

Methane distribution and oxidation around the Lena Delta in summer 2013

Methane distribution and oxidation around the Lena Delta in summer 2013

Microbial methanogenesis in the sulfate-reducing zone of sediments in the Eckernförde Bay, SW Baltic Sea

Exploring Sources and Biogeochemical Dynamics of Dissolved Methane in the Central Bohai Sea in Summer

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