Article

Methane Bubbling From Northern Lakes: Present and Future Contributions to the Global Methane Budget

Institute of Arctic Biology, University of Alaska, Fairbanks, AK 99775, USA.
Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences (Impact Factor: 2.15). 08/2007; 365(1856):1657-76. DOI: 10.1098/rsta.2007.2036
Source: PubMed

ABSTRACT

Large uncertainties in the budget of atmospheric methane (CH4) limit the accuracy of climate change projections. Here we describe and quantify an important source of CH4 -- point-source ebullition (bubbling) from northern lakes -- that has not been incorporated in previous regional or global methane budgets. Employing a method recently introduced to measure ebullition more accurately by taking into account its spatial patchiness in lakes, we estimate point-source ebullition for 16 lakes in Alaska and Siberia that represent several common northern lake types: glacial, alluvial floodplain, peatland and thermokarst (thaw) lakes. Extrapolation of measured fluxes from these 16 sites to all lakes north of 45 degrees N using circumpolar databases of lake and permafrost distributions suggests that northern lakes are a globally significant source of atmospheric CH4, emitting approximately 24.2+/-10.5Tg CH4yr(-1). Thermokarst lakes have particularly high emissions because they release CH4 produced from organic matter previously sequestered in permafrost. A carbon mass balance calculation of CH4 release from thermokarst lakes on the Siberian yedoma ice complex suggests that these lakes alone would emit as much as approximately 49000Tg CH4 if this ice complex was to thaw completely. Using a space-for-time substitution based on the current lake distributions in permafrost-dominated and permafrost-free terrains, we estimate that lake emissions would be reduced by approximately 12% in a more probable transitional permafrost scenario and by approximately 53% in a 'permafrost-free' Northern Hemisphere. Long-term decline in CH4 ebullition from lakes due to lake area loss and permafrost thaw would occur only after the large release of CH4 associated thermokarst lake development in the zone of continuous permafrost.

    • "They are prevalent in temperate and boreal peatlands of the northern hemisphere, often forming extensive complexes where their area may equal or exceed that of the intervening terrestrial area (Bragg and Tallis, 2001; Connolly et al., 2014). Pool areas are also rapidly expanding in a warming Arctic (Jorgenson et al., 2001; Vonk et al., 2015; Walter et al., 2007), and they are becoming a more commonplace feature in peatlands undergoing restoration as drains are blocked (Parry et al., 2014). Pools have previously been shown to be sources of CO 2 to the atmosphere and, particularly, hotspots of methane (CH 4 ) emission, a highly potent greenhouse gas (GHG) (Hamilton et al., 1994; Pelletier et al., 2014; Waddington and Roulet, 1996). "
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    ABSTRACT: Natural open-water pools are a common feature of northern peatlands and are known to be an important source of atmospheric methane (CH4). Pool environmental variables, particularly water chemistry, vegetation community and physical characteristics, have the potential to exert strong controls on carbon cycling in pools. A total of 66 peatland pools were studied across three regions of the UK (northern Scotland, south-west Scotland, and Northern Ireland). We found that within-region variability of pool water chemistry was low; however, for many pool variables measured there were significant differences between regions. PCA analysis showed that pools in SW Scotland were strongly associated with greater vegetative cover and shallower water depth which is likely to increase dissolved organic carbon (DOC) mineralisation rates, whereas pools in N Scotland were more open and deeper. Pool water DOC, particulate organic carbon and dissolved CH4 concentrations were significantly different between regions. Pools in Northern Ireland had the highest concentrations of DOC (mean=14.5mgL(-1)) and CH4 (mean=20.6μgCL(-1)). Chloride and sulphate concentrations were significantly higher in the pools in N Scotland (mean values 26.3 and 2.40mgL(-1), respectively) than elsewhere, due to a stronger marine influence. The ratio of UV absorbance at 465nm to absorbance at 665nm for pools in Northern Ireland indicated that DOC was sourced from poorly humified peat, potentially increasing the bioavailability and mineralisation of organic carbon in pools compared to the pools elsewhere. This study, which specifically aims to address a lack of basic biogeochemical knowledge about pool water chemistry, clearly shows that peatland pools are highly regionally variable. This is likely to be a reflection of significant regional-scale differences in peatland C cycling.
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    • "In some northern regions this has led to the expansion of permafrost thaw ponds and lakes (thermokarst systems; Grosse et al., 2013), whereas in other regions there has been a contraction and loss of these waterbodies (e.g., Andresen and Lougheed, 2015). These thermokarst systems are part of circumpolar and global biogeochemical cycles (Abnizova et al., 2012; Walter et al., 2007). Although some are carbon sinks (Walter Anthony et al., 2014), others are net sources of carbon dioxide (CO 2 ) and methane (CH 4 ) to the atmosphere (Walter et al., 2008). "
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    ABSTRACT: Permafrost thaw ponds and lakes are widespread across the northern landscape and may play a central role in global biogeochemical cycles, yet knowledge about their microbial ecology is limited. We sampled a set of thaw ponds and lakes as well as shallow rock-basin lakes that are located in distinct valleys along a north–south permafrost degradation gradient. We applied high-throughput sequencing of the 16S rRNA gene to determine co-occurrence patterns among bacterial taxa (operational taxonomic units, OTUs), and then analyzed these results relative to environmental variables to identify variables controlling bacterial community structure. Network analysis was applied to identify possible ecological linkages among the bacterial taxa and with abiotic and biotic variables. The results showed an overall high level of shared taxa among bacterial communities within each valley; however, the bacterial co-occurrence patterns were non-random, with evidence of habitat preferences. There were taxonomic differences in bacterial assemblages among the different valleys that were statistically related to dissolved organic carbon concentration, conductivity and phytoplankton biomass. Co-occurrence networks revealed complex interdependencies within the bacterioplankton communities and showed contrasting linkages to environmental conditions among the main bacterial phyla. The thaw pond networks were composed of a limited number of highly connected taxa. This “small world network” property would render the communities more robust to environmental change but vulnerable to the loss of microbial “keystone species”. These highly connected nodes (OTUs) in the network were not merely the numerically dominant taxa, and their loss would alter the organization of microbial consortia and ultimately the food web structure and functioning of these aquatic ecosystems.
    Full-text · Article · Jan 2016 · Biogeosciences
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    • "In some northern regions this has led to the expansion of permafrost thaw ponds and lakes (thermokarst systems; Grosse et al., 2013), whereas in other regions there has been a contraction and loss of these waterbodies (e.g., Andresen and Lougheed, 2015). These thermokarst systems are part of circumpolar and global biogeochemical cycles (Abnizova et al., 2012; Walter et al., 2007). Although some are carbon sinks (Walter Anthony et al., 2014), others are net sources of carbon dioxide (CO 2 ) and methane (CH 4 ) to the atmosphere (Walter et al., 2008). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Permafrost thaw ponds and lakes are widespread across the northern landscape and may play a central role in global biogeochemical cycles, yet knowledge about their microbial ecology is limited. We sampled a set of thaw ponds and lakes as well as shallow rock-basin lakes that are located in distinct valleys along a North-South permafrost degradation gradient. We applied high-throughput sequencing of the 16S rRNA gene to determine co-occurrence patterns among bacterial taxa (operational taxonomic units, OTUs), and then analyzed these results relative to environmental variables to identify variables controlling bacterial community structure. Network analysis was applied to identify possible ecological linkages among the bacterial taxa and with abiotic and biotic variables. The results showed an overall high level of shared taxa among bacterial communities within each valley, however the bacterial co-occurrence patterns were non-random, with evidence of habitat preferences. There were taxonomic differences in bacterial assemblages among the different valleys that were statistically related to dissolved organic carbon concentration, conductivity and phytoplankton biomass. Co-occurrence networks revealed complex interdependencies within the bacterioplankton communities and showed contrasting linkages to environmental conditions among the main bacterial phyla. The thaw pond networks were composed of a limited number of highly connected taxa. This ‘small world network’ property would render the communities more robust to environmental change but vulnerable to the loss of microbial ‘keystone species’. These highly connected nodes (OTUs) in the network were not merely the numerically dominant taxa, whose loss would greatly alter the organization of microbial consortia and ultimately the food web structure and functioning of these aquatic ecosystems.
    Full-text · Article · Jan 2016 · Biogeosciences Discussions
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