Methane production by three widespread marine phytoplankton species: release rates, precursor compounds, and relevance for the environment

Klintzsch, Thomas; Langer, Gerald; Nehrke, Gernot; Wieland, Anna; Lenhart, Katharina; Keppler, Frank

doi:10.5194/bg-2019-245

Cited by 10 publications

(10 citation statements)

References 58 publications

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“…Methane production has been reported during growth of coccolithophores 13 and other ubiquitous members of the prymnesiophyte class of marine phytoplankton 43 , which may contribute in part to the correlation we find between ∆CH 4 and NPP. However, a number of alternative pathways have been proposed for methanogenesis in surface ocean waters, which could give rise to the relationship indirectly.…”

Section: Discussionsupporting

confidence: 54%

Global ocean methane emissions dominated by shallow coastal waters

2019

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Oceanic emissions represent a highly uncertain term in the natural atmospheric methane (CH4) budget, due to the sparse sampling of dissolved CH4 in the marine environment. Here we overcome this limitation by training machine-learning models to map the surface distribution of methane disequilibrium (∆CH4). Our approach yields a global diffusive CH4 flux of 2–6TgCH4yr−1 from the ocean to the atmosphere, after propagating uncertainties in ∆CH4 and gas transfer velocity. Combined with constraints on bubble-driven ebullitive fluxes, we place total oceanic CH4 emissions between 6–12TgCH4yr−1, narrowing the range adopted by recent atmospheric budgets (5–25TgCH4yr−1) by a factor of three. The global flux is dominated by shallow near-shore environments, where CH4 released from the seafloor can escape to the atmosphere before oxidation. In the open ocean, our models reveal a significant relationship between ∆CH4 and primary production that is consistent with hypothesized pathways of in situ methane production during organic matter cycling.

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Section: Discussionsupporting

confidence: 54%

Global ocean methane emissions dominated by shallow coastal waters

2019

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“…Currently, there are two proposed pathways for oxic‐lake water CH 4 production: (1) Methane as a by‐product of methylphosphonate (MPN) decomposition, which is an alternative way of phosphorus acquisition when inorganic phosphorus is limited (Carini et al 2014; Yao et al 2016; Wang et al 2017); and (2) a pathway independent of MPN demethylation which is thought to be based on a Coenzyme‐M homologue (Tang et al 2016). Several studies have demonstrated the involvement of photoautotrophs in CH 4 formation in oxic water, both in the field (Grossart et al 2011; Bogard et al 2014; Hartmann et al 2020) and in the laboratory (Lenhart et al 2016; Klintzsch et al 2019; Bizic et al 2020; Hartmann et al 2020). The association of oxic CH 4 production to MPN degradation and autotrophic organisms suggests that phosphorus and light might be important factors driving oxic CH 4 production.…”

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confidence: 99%

Photosynthesis‐driven methane production in oxic lake water as an important contributor to methane emission

Günthel

Klawonn

Woodhouse

et al. 2020

Limnology & Oceanography

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Recent discovery of methane (CH4) production in oxic waters challenges the conventional understanding of strict anoxic requirement for biological CH4 production. High‐resolution field measurements in Lake Stechlin, as well as incubation experiments, suggested that oxic‐water CH4 production occurred throughout much of the water column and was associated with phytoplankton especially diatoms, cyanobacteria, green algae, and cryptophytes. In situ concentrations and δ13C values of CH4 in oxic water were negatively correlated with soluble reactive phosphorus concentrations. Using 13C‐labeling techniques, we showed that bicarbonate was converted to CH4, and the production exceeded oxidation at day, but was comparable at night. These experimental data, along with complementary field observations, indicate a clear link between photosynthesis and the CH4 production‐consumption balance in phosphorus‐limited epilimnic waters. Comparison between surface CH4 emission data and experimental CH4 production rates suggested that the oxic CH4 source significantly contributed to surface emission in Lake Stechlin. These findings call for re‐examination of the aquatic CH4 cycle and climate predictions.

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“…Recent experimental observations indicate that [FeFe]‐nitrogenase from Rhodopseudomonas palustris can release methane directly from bicarbonate (Zheng et al, ), though the flux would be small and these organisms are vastly outnumbered by SAR11 (Carlson et al, ). Finally, haptophyte algae and coccolithophores were shown to demethylate common methyl‐bearing compounds such as dimethyl sulfoxide, dimethyl sulfide, methionine sulfoxide, methionine, and dissolved inorganic carbon (Bizic‐Ionescu et al, ; Klintzsch et al, ; Lenhart et al, )—though each of these processes necessitates full isotopic characterization before it can be included or excluded in interpreting methane cycling in oxic waters, and it is not clear how large these fluxes would be in a system such as ALOHA given the more clear inorganic P‐limited scenario. Taken together, we infer that methane in surface waters at Station ALOHA reflects the carbon isotope delta values of MPn in HMWDOM and precursors in bulk organic matter, while the carbon isotopes of methane below the euphotic zone reflect a more complex life history.…”

Section: Resultsmentioning

confidence: 99%

“…Although MPn demethylation is a possible methane source in phosphate‐limited oxygen‐rich systems, directly linking methane to MPn has remained a challenge. Moreover, distinguishing MPn‐derived methane from other known and putative sources (cf Bizic‐Ionescu et al, , Klintzsch et al, , Zheng et al, ) requires each process generate unique fractionation patterns. The stable isotopes of carbon (C) and hydrogen (H) within the methane have been used to track biotic and abiotic sources across a diversity of environments and processes (Etiope & Sherwood Lollar, ; Whiticar et al, ).…”

Section: Introductionmentioning

confidence: 99%

Microbial Methane From Methylphosphonate Isotopically Records Source

Taenzer

Carini

Masterson

et al. 2020

Geophysical Research Letters

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Methane is a potent greenhouse gas commonly supersaturated in the oxic surfaces waters of oceans and lakes, yet canonical microbial methanogens are obligate anaerobes. One proposed methane production pathway involves microbial degradation of methylphosphonate (MPn), which can proceed in the presence of oxygen. Directly tracing dissolved methane to its source in oxic waters, however, remains a challenge. To address this knowledge gap, we quantified the carbon isotopic fractionation between substrate MPn and product methane (1.3‰) in lab experiments, which was 1 to 2 orders of magnitude smaller than canonical pathways of microbial methanogenesis (20 to 100‰). Together, these results indicated that microbial catabolism of MPn is a source of methane in surface oceans and lake waters, but to differentiate sources of MPn in nature a further accounting of all sources is necessary. Methane from this pathway must be considered in constraining the marine carbon cycle and methane budget.

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Methane production by three widespread marine phytoplankton species: release rates, precursor compounds, and relevance for the environment

Cited by 10 publications

References 58 publications

Global ocean methane emissions dominated by shallow coastal waters

Global ocean methane emissions dominated by shallow coastal waters

Photosynthesis‐driven methane production in oxic lake water as an important contributor to methane emission

Microbial Methane From Methylphosphonate Isotopically Records Source

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