/pdf/photosynthesis-driven-methane-production-in-oxic-lake-water-2gtxng6lu9.pdf

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

Methane production in oxic seawater of the western North Pacific and its marginal seas

 Methane ( CH4 ) emissions from reservoirs are
responsible for most of the atmospheric climatic forcing of these aquatic
ecosystems, comparable to emissions from paddies or biomass burning
Primarily, CH4 is produced during the anaerobic mineralization of
organic carbon in anoxic sediments by methanogenic archaea However, the
origin of the recurrent and ubiquitous CH4 supersaturation in oxic
waters (ie, the methane paradox) is still controversial Here, we
determined the dissolved CH4 concentration in the water column of
12 reservoirs during summer stratification and winter mixing to explore
 CH4 sources in oxic waters Reservoir sizes ranged from 118 to 2613 km 2  We found that dissolved CH4 in the water column varied
by up to 4 orders of magnitude (002–21364  µ mol L −1 ), and all oxic depths
were consistently supersaturated in both periods Phytoplanktonic sources
appear to determine the concentration of CH4 in these reservoirs
primarily In anoxic waters, the depth-cumulative chlorophyll  a 
concentration, a proxy for the phytoplanktonic biomass exported to
sediments, was correlated to CH4 concentration In oxic waters, the
photosynthetic picoeukaryotes' abundance was significantly correlated to the
dissolved CH4 concentration during both the stratification and the
mixing The mean depth of the reservoirs, as a surrogate of the vertical
 CH4 transport from sediment to the oxic waters, also contributed
notably to the CH4 concentration in oxic waters Our findings suggest
that photosynthetic picoeukaryotes can play a significant role in
determining CH4 concentration in oxic waters, although their role as
 CH4 sources to explain the methane paradox has been poorly explored

/pdf/dissolved-ch-4-coupled-to-photosynthetic-picoeukaryotes-in-r5f1mosops.pdf

Dissolved CH 4 coupled to photosynthetic picoeukaryotes in oxic waters and to cumulative chlorophyll a in anoxic waters of reservoirs

/pdf/microbial-methane-from-methylphosphonate-isotopically-1czk1200s3.pdf

Microbial Methane From Methylphosphonate Isotopically Records Source

Methane (CH4) from aquatic ecosystems contributes to about half of total global CH4 emissions to the atmosphere. Until recently, aquatic biogenic CH4 production was exclusively attributed to methanogenic archaea living under anoxic or suboxic conditions in sediments, bottom waters, and wetlands. However, evidence for oxic CH4 production (OMP) in freshwater, brackish, and marine habitats is increasing. Possible sources were found to be driven by various planktonic organisms supporting different OMP mechanisms. Surprisingly, submerged macrophytes have been fully ignored in studies on OMP, yet they are key components of littoral zones of ponds, lakes, and coastal systems. High CH4 concentrations in these zones have been attributed to organic substrate production promoting classic methanogenesis in the absence of oxygen. Here, we review existing studies and argue that, similar to terrestrial plants and phytoplankton, macroalgae and submerged macrophytes may directly or indirectly contribute to CH4 formation in oxic waters. We propose several potential direct and indirect mechanisms: (1) direct production of CH4; (2) production of CH4 precursors and facilitation of their bacterial breakdown or chemical conversion; (3) facilitation of classic methanogenesis; and (4) facilitation of CH4 ebullition. As submerged macrophytes occur in many freshwater and marine habitats, they are important in global carbon budgets and can strongly vary in their abundance due to seasonal and boom‐bust dynamics. Knowledge on their contribution to OMP is therefore essential to gain a better understanding of spatial and temporal dynamics of CH4 emissions and thus to substantially reduce current uncertainties when estimating global CH4 emissions from aquatic ecosystems.

https://archive-ouverte.unige.ch/unige:166965/ATTACHMENT01

Ai Kobayashi

Papers

Aerobic methane production by planktonic microbes in lakes

Aerobic methane production in oxygenated water column of a lake ecosystem