Freshwater Ecosystems Crucial in Global Emissions of Greenhouse Gases

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Research on freshwater ecosystems has identified the crucial role they play in the global emissions of greenhouse gases (GHGs). Macrophytes, including algae and submerged plants, are the main suppliers of organic matter to freshwater sediments, controlling the production of GHGs such as methane (CH). However, species-specific differences in detritus transformation into CH and eutrophication can affect GHG production, indicating a complex relationship between macrophyte detritus quality and GHG emissions. A recent study published in the Journal of Environmental Sciences assessed the CH and CO production and changes in detritus quality in a 64-day microcosm experiment involving seven phylogenetically different macrophytes under two trophic conditions and with/without sediment.

Key Takeaways:

  • Macrophytes are the primary organic matter suppliers to freshwater sediments, controlling the production of greenhouse gases (GHGs) such as methane (CH).
  • Species-specific differences in detritus transformation into CH can determine contrasting patterns of GHG production.
  • Eutrophication can affect the degradation of detritus and subsequent GHG production.
  • A 64-day microcosm experiment involving seven phylogenetically different macrophytes under two trophic conditions and with/without sediment showed significant variations in CH and CO production.
  • The ranking in mean cumulative CH production was: Chara hispida > Nitella hyalina > Najas marina > Teucrium scordium > Stuckenia pectinata > Myriophyllum spicatum > filamentous algae.
  • GHGs maximum production rates ranged from 1.2 to 1.6 mmol CH/(g OC·day) and 1.5 to 1.7 mmol CO/(g OC·day).
  • The CO:CH ratio was initially biased toward CO but fell to approximately 1 for all macrophyte species and treatments after 10 days.
  • Sediment favored detritus decomposition, increasing GHG production.

Statistics:

  • 64 days: duration of the microcosm experiment
  • 7 phylogenetically different macrophytes: involved in the experiment
  • 2 trophic conditions: oligo- versus eutrophic
  • 2 sediment conditions: with/without sediment
  • 1.2-1.6 mmol CH/(g OC·day) and 1.5-1.7 mmol CO/(g OC·day): GHGs maximum production rates
  • 200: initial CO:CH ratio after 10 days
  • 1: CO:CH ratio after 10 days for all macrophyte species and treatments

Sources:

  • Freshwater macrophyte type (macroalgae versus phanerogams) mainly determines detritus-derived greenhouse gases production: A microcosm experiment. Journal of Environmental Sciences, 2025;157:674-689.
  • Science Press, 16 Donghuangchenggen North St, Beijing 100717, Peoples R China.
  • Eric Puche, Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia, Paterna 46980, Spain.
  • Belen Roger, Mariana Vargas-Sanchez, Salvador Sanchez-Carrillo, and Maria A. Rodrigo (co-authors).
  • NewsRx LLC. University of Valencia Reports Findings in Science [Freshwater macrophyte type (macroalgae versus phanerogams) mainly determines detritus-derived greenhouse gases production: A microcosm experiment]. Global Warming Focus. July 14, 2025; p 367.