scholarly journals Evidence for methane production by marine algae (<i>Emiliana huxleyi</i>) and its implication for the methane paradox in oxic waters

2015 ◽  
Vol 12 (24) ◽  
pp. 20323-20360 ◽  
Author(s):  
K. Lenhart ◽  
T. Klintzsch ◽  
G. Langer ◽  
G. Nehrke ◽  
M. Bunge ◽  
...  
Keyword(s):  
Surface Waters ◽  
Marine Algae ◽  
Methanogenic Archaea ◽  
Emiliania Huxleyi ◽  
Algal Culture ◽  
Radiation Balance ◽  
Surface Mixed Layer ◽  
Large Lakes ◽  
Isotope Label ◽  
Ch4 Production

Abstract. Methane (CH4), an important greenhouse gas that affects radiation balance and consequently the earth's climate, still has uncertainties in its sinks and sources. The world's oceans are considered to be a source of CH4 to the atmosphere, although the biogeochemical processes involved in its formation are not fully understood. Several recent studies provided strong evidence of CH4 production in oxic marine and freshwaters but its source is still a topic of debate. Studies of CH4 dynamics in surface waters of oceans and large lakes have concluded that pelagic CH4 supersaturation cannot be sustained either by lateral inputs from littoral or benthic inputs alone. However, frequently regional and temporal oversaturation of surface waters occurs. This comprises the observation of a CH4 oversaturating state within the surface mixed layer, sometimes also termed the "oceanic methane paradox". In this study we considered marine algae as a possible direct source of CH4. Therefore, the coccolithophore Emiliania huxleyi was grown under controlled laboratory conditions and supplemented with two 13C-labelled carbon substrates, namely bicarbonate and a position-specific 13C-labelled methionine (R-S-13CH3). The CH4 production was 0.7 μg POC g−1 d−1, or 30 ng g−1 POC h−1. After supplementation of the cultures with the 13C labelled substrate, the isotope label was observed in headspace-CH4. Moreover, the absence of methanogenic archaea within the algal culture and the oxic conditions during CH4 formation suggest that marine algae such as Emiliania huxleyi contribute to the observed spatial and temporal restricted CH4 oversaturation in ocean surface waters.

scholarly journals Evidence for methane production by the marine algae <i>Emiliania huxleyi</i>

2016 ◽  
Vol 13 (10) ◽  
pp. 3163-3174 ◽  
Author(s):  
Katharina Lenhart ◽  
Thomas Klintzsch ◽  
Gerald Langer ◽  
Gernot Nehrke ◽  
Michael Bunge ◽  
...  
Keyword(s):  
Surface Waters ◽  
Marine Algae ◽  
Methanogenic Archaea ◽  
Emiliania Huxleyi ◽  
Algal Culture ◽  
Radiation Balance ◽  
Surface Mixed Layer ◽  
Large Lakes ◽  
Isotope Label ◽  
Ch4 Production

Abstract. Methane (CH4), an important greenhouse gas that affects radiation balance and consequently the earth's climate, still has uncertainties in its sinks and sources. The world's oceans are considered to be a source of CH4 to the atmosphere, although the biogeochemical processes involved in its formation are not fully understood. Several recent studies provided strong evidence of CH4 production in oxic marine and freshwaters, but its source is still a topic of debate. Studies of CH4 dynamics in surface waters of oceans and large lakes have concluded that pelagic CH4 supersaturation cannot be sustained either by lateral inputs from littoral or benthic inputs alone. However, regional and temporal oversaturation of surface waters occurs frequently. This comprises the observation of a CH4 oversaturating state within the surface mixed layer, sometimes also termed the "oceanic methane paradox". In this study we considered marine algae as a possible direct source of CH4. Therefore, the coccolithophore Emiliania huxleyi was grown under controlled laboratory conditions and supplemented with two 13C-labeled carbon substrates, namely bicarbonate and a position-specific 13C-labeled methionine (R-S-13CH3). The CH4 production was 0.7 µg particular organic carbon (POC) g−1 d−1, or 30 ng g−1 POC h−1. After supplementation of the cultures with the 13C-labeled substrate, the isotope label was observed in headspace CH4. Moreover, the absence of methanogenic archaea within the algal culture and the oxic conditions during CH4 formation suggest that the widespread marine algae Emiliania huxleyi might contribute to the observed spatially and temporally restricted CH4 oversaturation in ocean surface waters.

scholarly journals Methane paradox in tropical lakes? Sedimentary fluxes rather than water column production in oxic waters sustain methanotrophy and emissions to the atmosphere

2020 ◽  
Author(s):  
Cédric Morana ◽  
Steven Bouillon ◽  
Vimac Nolla-Ardèvol ◽  
Fleur A. E. Roland ◽  
William Okello ◽  
...  
Keyword(s):  
Surface Waters ◽  
Tropical Lakes ◽  
Large Lakes ◽  
Ch4 Flux ◽  
Ch4 Emissions ◽  
Isotope Tracer ◽  
Ch4 Production ◽  
Elevated Water ◽  
Lake Size ◽  
Sunlight Intensity

Abstract. Despite growing evidence that methane (CH4) formation could also occur in well-oxygenated surface freshwaters, its significance at the ecosystem scale is uncertain. Empirical models based on data gathered at high latitude predict that the contribution of oxic CH4 increases with lake size and should represent the majority of CH4 emissions in large lakes. However, such predictive models could not directly apply to tropical lakes which differ from their temperate counterparts in some fundamental characteristics, such as year-round elevated water temperature. We conducted stable isotope tracer experiments which revealed that oxic CH4 production is closely related to phytoplankton metabolism, and is a common feature in five contrasting African lakes. Nevertheless, methanotrophic activity in surface waters and CH4 emissions to the atmosphere were predominantly fuelled by CH4 generated in sediments and physically transported to the surface. Indeed, measured CH4 bubble dissolution flux and diffusive benthic CH4 flux were several orders of magnitude higher than CH4 production in surface waters. Microbial CH4 consumption dramatically decreased with increasing sunlight intensity, suggesting that the freshwater CH4 paradox might be also partly explained by photo-inhibition of CH4 oxidizers in the illuminated zone. Sunlight appeared as an overlooked but important factor determining the CH4 dynamics in surface waters, directly affecting its production by photoautotrophs and consumption by methanotrophs.

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

2019 ◽  
Author(s):  
Thomas Klintzsch ◽  
Gerald Langer ◽  
Gernot Nehrke ◽  
Anna Wieland ◽  
Katharina Lenhart ◽  
...  
Keyword(s):  
Marine Algae ◽  
Dimethyl Sulfide ◽  
Stable Carbon Isotope ◽  
Methionine Sulfoxide ◽  
Emiliania Huxleyi ◽  
Marine Phytoplankton ◽  
Sulphur Compounds ◽  
Ch4 Production ◽  
Hydrogen Carbonate ◽  
A Minor

Abstract. The world’s oceans are considered to be a minor source of methane (CH4) to the atmosphere although the magnitude of total net emissions is highly uncertain. In recent years the origin of the frequently observed in situ CH4 production in the ocean mixed layer has received much attention. Marine algae might contribute to the observed CH4 oversaturation in oxic waters, but so far direct evidence for CH4 production by marine algae has only been provided for the coccolithophore Emiliania huxleyi. In the present study we investigated, next to Emiliania huxleyi, other widespread haptophytes, i.e. Phaeocystis globosa and Chrysochromulina sp. for CH4 formation. Our results of CH4 production and stable carbon isotope measurements provide unambiguous evidence that all three investigated marine algae produce CH4 per se under oxic conditions and at rates ranging from 1.6 ± 0.5 to 2.7 ± 0.7 µg CH4 per g POC (particulate organic carbon) d−1 at a temperature of 20 °C with Chrysochromulina sp. and E. huxleyi showing the lowest and highest rates, respectively. In cultures that were treated with 13C-labelled hydrogen carbonate δ13CH4 values increased with incubation time, clearly resulting from the conversion of 13C-hydrogen carbonate to 13CH4. The addition of 13C labelled dimethyl sulfide, dimethyl sulfoxide and methionine sulfoxide – known algal metabolites that are ubiquitous in marine surface layers - enabled us to clearly monitor the occurrence of 13C-enriched CH4 in cultures of Emiliania huxleyi clearly indicating that methylated sulphur compounds are also precursors of CH4. We propose that CH4 production could be a common process among marine haptophytes likely contributing to CH4 oversaturation in oxic waters.

scholarly journals Methane paradox in tropical lakes? Sedimentary fluxes rather than pelagic production in oxic conditions sustain methanotrophy and emissions to the atmosphere

2020 ◽  
Vol 17 (20) ◽  
pp. 5209-5221
Author(s):  
Cédric Morana ◽  
Steven Bouillon ◽  
Vimac Nolla-Ardèvol ◽  
Fleur A. E. Roland ◽  
William Okello ◽  
...  
Keyword(s):  
Surface Waters ◽  
Tropical Lakes ◽  
Large Lakes ◽  
Ch4 Flux ◽  
Ch4 Emissions ◽  
Isotope Tracer ◽  
Ch4 Production ◽  
Elevated Water ◽  
Lake Size ◽  
Sunlight Intensity

Abstract. Despite growing evidence that methane (CH4) formation could also occur in well-oxygenated surface fresh waters, its significance at the ecosystem scale is uncertain. Empirical models based on data gathered at high latitude predict that the contribution of oxic CH4 increases with lake size and should represent the majority of CH4 emissions in large lakes. However, such predictive models could not directly apply to tropical lakes, which differ from their temperate counterparts in some fundamental characteristics, such as year-round elevated water temperature. We conducted stable-isotope tracer experiments, which revealed that oxic CH4 production is closely related to phytoplankton metabolism and is a common feature in five contrasting African lakes. Nevertheless, methanotrophic activity in surface waters and CH4 emissions to the atmosphere were predominantly fuelled by CH4 generated in sediments and physically transported to the surface. Indeed, CH4 bubble dissolution flux and diffusive benthic CH4 flux were several orders of magnitude higher than CH4 production in surface waters. Microbial CH4 consumption dramatically decreased with increasing sunlight intensity, suggesting that the freshwater “CH4 paradox” might be also partly explained by photo-inhibition of CH4 oxidizers in the illuminated zone. Sunlight appeared as an overlooked but important factor determining the CH4 dynamics in surface waters, directly affecting its production by photoautotrophs and consumption by methanotrophs.

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

2019 ◽  
Vol 16 (20) ◽  
pp. 4129-4144 ◽  
Author(s):  
Thomas Klintzsch ◽  
Gerald Langer ◽  
Gernot Nehrke ◽  
Anna Wieland ◽  
Katharina Lenhart ◽  
...  
Keyword(s):  
Marine Algae ◽  
Dimethyl Sulfide ◽  
Stable Carbon Isotope ◽  
Methionine Sulfoxide ◽  
Marine Phytoplankton ◽  
Production Rates ◽  
Ch4 Production ◽  
Hydrogen Carbonate ◽  
Marine Surface ◽  
Methylated Sulfur Compounds

Abstract. Methane (CH4) production within the oceanic mixed layer is a widespread phenomenon, but the underlying mechanisms are still under debate. Marine algae might contribute to the observed CH4 oversaturation in oxic waters, but so far direct evidence for CH4 production by marine algae has only been provided for the coccolithophore Emiliania huxleyi. In the present study we investigated, next to E. huxleyi, other widespread haptophytes, i.e., Phaeocystis globosa and Chrysochromulina sp. We performed CH4 production and stable carbon isotope measurements and provide unambiguous evidence that all three investigated marine algae are involved in the production of CH4 under oxic conditions. Rates ranged from 1.9±0.6 to 3.1±0.4 µg of CH4 per gram of POC (particulate organic carbon) per day, with Chrysochromulina sp. and E. huxleyi showing the lowest and highest rates, respectively. Cellular CH4 production rates ranged from 16.8±6.5 (P. globosa) to 62.3±6.4 ag CH4 cell−1 d−1 (E. huxleyi; ag = 10−18 g). In cultures that were treated with 13C-labeled hydrogen carbonate, δ13CH4 values increased with incubation time, resulting from the conversion of 13C–hydrogen carbonate to 13CH4. The addition of 13C-labeled dimethyl sulfide, dimethyl sulfoxide, and methionine sulfoxide – known algal metabolites that are ubiquitous in marine surface layers – resulted in the occurrence of 13C-enriched CH4 in cultures of E. huxleyi, clearly indicating that methylated sulfur compounds are also precursors of CH4. By comparing the algal CH4 production rates from our laboratory experiments with results previously reported in two field studies of the Pacific Ocean and the Baltic Sea, we might conclude that algae-mediated CH4 release is contributing to CH4 oversaturation in oxic waters. Therefore, we propose that haptophyte mediated CH4 production could be a common and important process in marine surface waters.

Formation and mosaicity of coccolith segment calcite of the marine algae Emiliania huxleyi

2017 ◽  
Vol 54 (1) ◽  
pp. 85-104 ◽  
Author(s):  
Xiaofei Yin ◽  
Andreas Ziegler ◽  
Klemens Kelm ◽  
Ramona Hoffmann ◽  
Philipp Watermeyer ◽  
...  
Keyword(s):  
Marine Algae ◽  
Emiliania Huxleyi

scholarly journals Ikaite crystals in melting sea ice – implications for <i>p</i>CO<sub>2</sub> and pH levels in Arctic surface waters

2012 ◽  
Vol 6 (2) ◽  
pp. 1015-1035 ◽  
Author(s):  
S. Rysgaard ◽  
R. N. Glud ◽  
K. Lennert ◽  
M. Cooper ◽  
N. Halden ◽  
...  
Keyword(s):  
Sea Ice ◽  
Surface Waters ◽  
Elevated Temperatures ◽  
Co2 Exchange ◽  
The Arctic ◽  
Co2 Uptake ◽  
Surface Mixed Layer ◽  
Chemical Transformations ◽  
X Ray Diffraction ◽  
Antarctic Sea Ice

Abstract. A major issue of Arctic marine science is to understand whether the Arctic Ocean is, or will be, a source or sink for air-sea CO2 exchange. This has been complicated by the recent discoveries of ikaite (CaCO3·6H2O) in Arctic and Antarctic sea ice, which indicate that multiple chemical transformations occur in sea ice with a possible effect on CO2 and pH conditions in surface waters. Here we report on biogeochemical conditions, microscopic examinations and x-ray diffraction analysis of single crystals from an actively melting 1.7 km2 (0.5–1 m thick) drifting ice floe in the Fram Strait during summer. Our findings show that ikaite crystals are present throughout the sea ice but with larger crystals appearing in the upper ice layers. Ikaite crystals placed at elevated temperatures gradually disintegrated into smaller crystallites and dissolved. During our field campaign in late June, melt reduced the ice flow thickness by ca. 0.2 m per week and resulted in an estimated 1.6 ppm decrease of pCO2 in the ocean surface mixed layer. This corresponds to an air-sea CO2 uptake of 11 mmol m−2 sea ice d−1 or to 3.5 ton km−2 ice floe week−1.

scholarly journals Validation of the Thorpe scale-derived vertical diffusivities against microstructure measurements in the Kerguelen region

2014 ◽  
Vol 11 (8) ◽  
pp. 12137-12157 ◽  
Author(s):  
Y.-H. Park ◽  
J.-H. Lee ◽  
I. Durand ◽  
C.-S. Hong
Keyword(s):  
Surface Waters ◽  
Water Layer ◽  
Polar Front ◽  
Surface Mixed Layer ◽  
Kerguelen Islands ◽  
Seasonal Thermocline ◽  
Thorpe Scale ◽  
Microstructure Measurements ◽  
High Degree ◽  
O 10

Abstract. The Thorpe scale is an energy containing vertical overturning scale of large eddies associated with shear generated turbulence. We make here indirect estimates of vertical diffusivities from the Thorpe scale method in the Polar Front region east of the Kerguelen Islands based on fine scale density profiles gathered during the 2011 KEOPS2 cruise. These are validated in comparison with diffusivities estimated from the turbulence dissipation rate directly measured via a TurboMAP microprofiler. The results are sensitive to the choice of the diffusivity parameterization and the Gargett and Garner's (2008) overturn ratio Ro, with the optimal results showing an agreement within a factor of 4, on average, having been obtained from the parameterization by Shih et al. (2005) and the Ro = 0.25 criterion. The Thorpe scale-derived diffusivities in the KEOPS2 region show a high degree of spatial variability, ranging from a canonical value of O(10−5 m2 s−1) in the Winter Water layer and in the Subantarctic surface waters immediately north of the Polar Front to a high value of O(10−4 m2 s−1) in the seasonal thermocline just below the surface mixed layer. The latter values are found especially over the shallow plateau southeast of the Kerguelen Islands and in the Antarctic surface waters associated with the Polar Front attached to the escarpment northeast of the islands.

scholarly journals Straw application in paddy soil enhances methane production also from other carbon sources

2013 ◽  
Vol 10 (8) ◽  
pp. 14169-14193 ◽  
Author(s):  
Q. Yuan ◽  
J. Pump ◽  
R. Conrad
Keyword(s):  
Priming Effect ◽  
Carbon Sources ◽  
Methanogenic Archaea ◽  
Rice Fields ◽  
Soil Environment ◽  
Traditional Management ◽  
Positive Priming ◽  
Hydrogenotrophic Methanogenesis ◽  
Ch4 Production ◽  
Straw Application

Abstract. Flooded rice fields are an important source of the greenhouse gas methane. Methane is produced from rice straw (RS), soil organic matter (SOM), and rice root organic carbon (ROC). Addition of RS is widely used for ameliorating soil fertility. However, this practice provides additional substrate for CH4 production and results in increased CH4 emission. Here, we found that decomposing RS is not only a substrate of CH4 production, but in addition stimulates CH4 production from SOM and ROC. Apart from accelerating the creation of reduced conditions in the soil environment, RS decomposition exerted a positive priming effect on SOM-derived CH4 production. In particular, hydrogenotrophic methanogenesis from SOM-derived CO2 was stimulated, presumably by H2 released from RS decomposition. On the other hand, the positive priming effect of RS on ROC-derived CH4 production was probably caused by the significant increase of the abundance of methanogenic archaea in the RS treatment compared with the untreated control. Our results show that traditional management of rice residues exerts a positive feedback on CH4 production from rice fields, thus exacerbating its effect on the global CH4 budget.

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