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<p>Ponds are a large source of atmospheric methane (CH<sub>4</sub>), a potent greenhouse gas, resulting from the net balance between input from sedimentary methanogenesis and removal by CH<sub>4</sub> oxidation (MOX). Here, we test whether methanogenesis pathways (acetoclastic or hydrogenotrophic) and MOX might differ between clear-water (macrophyte-dominated) and turbid-water (phytoplankton-dominated) ponds. We measured the <sup>13</sup>C/<sup>12</sup>C ratio of CH<sub>4</sub> (δ<sup>13</sup>C-CH<sub>4</sub>) from gas trapped in bubble traps, from bubbles deliberately released by the perturbing sediments, and in dissolved CH<sub>4</sub> in the water column in four urban ponds in Brussels, Belgium (Leybeek, Pêcheries, Tenreuken, Silex). In summer, the δ<sup>13</sup>C-CH<sub>4</sub> values of sediment bubbles indicated that the hydrogenotrophic methanogenesis pathway appeared to be more important in clear-water (macrophyte-dominated) ponds (Leybeek and Pêcheries), whereas the acetoclastic methanogenesis pathway appeared to be more important in turbid-water (phytoplankton-dominated) ponds (Tenreuken and Silex). The δ<sup>13</sup>C-CH<sub>4</sub> values from bubble traps indicated a seasonal shift from acetoclastic methanogenesis pathway in spring–summer to hydrogenotrophic methanogenesis in fall. The δ<sup>13</sup>C-CH<sub>4</sub> of dissolved CH<sub>4</sub> indicated higher rates of MOX in turbid-water ponds (Leybeek and Pêcheries) compared to clear-water ponds (Tenreuken and Silex), with an overall positive relation with total suspended matter and chlorophyll-a concentrations. The presence of suspended particles likely enhanced MOX by reducing light inhibition of MOX and/or by serving as substrates in the water column for attached methanotrophic bacteria. MOX represented ~ 80% of the total dissolved CH<sub>4</sub> removal from the water column (MOX plus diffusive emission to the atmosphere) in the turbid-water ponds (Leybeek and Pêcheries) and &lt; 60% in the clear-water ponds (Tenreuken and Silex). Our results suggest that shifts from clear- to turbid-water ecological states due to eutrophication may change CH<sub>4</sub> production pathways (with a higher contribution of acetoclastic versus hydrogenotrophic methanogenesis) and enhance dissolved CH<sub>4</sub> removal by MOX in the water column.</p>

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Methanogenesis pathways and methane oxidation in two clear-water and two turbid-water urban ponds in Brussels (Belgium)

  • 期刊论文

  • 发表日期：

    2026年1月20日

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  • Alberto V. Borges,
  • Nathalie Gypens,
  • Thomas Bauduin

摘要

Ponds are a large source of atmospheric methane (CH4), a potent greenhouse gas, resulting from the net balance between input from sedimentary methanogenesis and removal by CH4 oxidation (MOX). Here, we test whether methanogenesis pathways (acetoclastic or hydrogenotrophic) and MOX might differ between clear-water (macrophyte-dominated) and turbid-water (phytoplankton-dominated) ponds. We measured the 13C/12C ratio of CH4 (δ13C-CH4) from gas trapped in bubble traps, from bubbles deliberately released by the perturbing sediments, and in dissolved CH4 in the water column in four urban ponds in Brussels, Belgium (Leybeek, Pêcheries, Tenreuken, Silex). In summer, the δ13C-CH4 values of sediment bubbles indicated that the hydrogenotrophic methanogenesis pathway appeared to be more important in clear-water (macrophyte-dominated) ponds (Leybeek and Pêcheries), whereas the acetoclastic methanogenesis pathway appeared to be more important in turbid-water (phytoplankton-dominated) ponds (Tenreuken and Silex). The δ13C-CH4 values from bubble traps indicated a seasonal shift from acetoclastic methanogenesis pathway in spring–summer to hydrogenotrophic methanogenesis in fall. The δ13C-CH4 of dissolved CH4 indicated higher rates of MOX in turbid-water ponds (Leybeek and Pêcheries) compared to clear-water ponds (Tenreuken and Silex), with an overall positive relation with total suspended matter and chlorophyll-a concentrations. The presence of suspended particles likely enhanced MOX by reducing light inhibition of MOX and/or by serving as substrates in the water column for attached methanotrophic bacteria. MOX represented ~ 80% of the total dissolved CH4 removal from the water column (MOX plus diffusive emission to the atmosphere) in the turbid-water ponds (Leybeek and Pêcheries) and < 60% in the clear-water ponds (Tenreuken and Silex). Our results suggest that shifts from clear- to turbid-water ecological states due to eutrophication may change CH4 production pathways (with a higher contribution of acetoclastic versus hydrogenotrophic methanogenesis) and enhance dissolved CH4 removal by MOX in the water column.