Carbon emission along a eutrophication gradient in temperate riverine wetlands: effect of primary productivity and plant community composition

Abstract

International audience1. Eutrophication increases primary productivity and favours the predominance of floating vegetation in wetlands. Carbon (C) fluxes in wetlands are strongly driven by primary productivity and can differ by vegetation type. However, to the best of our knowledge, the role of eutrophication in C fluxes has rarely been assessed. 2. Consequently, we aimed to measure the seasonal variation in carbon dioxide (CO2) and methane (CH4) fluxes at six aquatic sites in four temperate wetlands, ranging along a gradient of sediment total phosphorus content, and determine whether C fluxes correlate with above-ground net primary productivity (ANPP) and plant community composition along this eutrophication gradient. 3. Daytime CO2 emissions were significantly and negatively correlated with wetland net primary productivity as a result of the greater C fixation by photosynthesis during the peak of production. Conversely, CH4 emissions were significantly and positively correlated with wetland ANPP, possibly due to higher litter production and anaerobic decomposition. 4. The highest CH4 emissions were observed above floating vegetation, which favoured hypoxic conditions in the water column. CH4 emissions including ebullition were higher above macroalgal belts than above vascular plants with floating leaves. CH4 emissions without ebullition (i.e. resulting from plant transport and diffusion) better correlated with the abundance of macroalgae than with the abundance of vascular plants with floating leaves. 5. Our results suggest that eutrophication may greatly modify CO2 and CH4 emissions from wetlands through changes in vegetation type and productivity

Assessment of methane and carbon dioxide emissions in two sub‐basins of a small acidic bog lake artificially divided 30 years ago

“…() suggested such a method as a tool for assessing diffusion and ebullition, while Grasset et al. () was one of the first studies to include ebullition data from these newer gas analysers.…”

“…Therefore, when no linear regression trend was observed to determine the flux, we used the initial and end points to determine the sum of diffusive and ebullitive CH 4 fluxes, as discussed by Goodrich, Varner, Frolking, Duncan, and Crill (2011), Zhao et al (2015) and Grasset, Abril, Guillard, Delolme, and Bornette (2016). We acknowledge that our sampling procedure may not accurately measure diel gas emissions, as previous studies have found large variations in diel CH 4 and CO 2 fluxes (Liu et al, 2016;Natchimuthu, Selvam, & Bastviken, 2014;Natchimuthu et al, 2016).…”

“…Newer gas analysers and the combination with established techniques may help to determine CH 4 diffusion and ebullition in freshwater ecosystems. Zhao et al (2015) suggested such a method as a tool for assessing diffusion and ebullition, while Grasset et al (2016) was one of the first studies to include ebullition data from these newer gas analysers.…”

Sediment type rules the response of aquatic plant communities to dewatering in wetlands

“…; Grasset et al. ). Among the changes that affect wetlands, increasing use of water resources, together with climate change, is leading to periodic or chronic water deficits and, consequently, to large seasonal variations in water levels (Arnell ; Lehner et al.…”

Regime shift in the littoral ecosystem of volcanic Lake Atitlán in Central America: combined role of stochastic event and invasive plant species

“…Invasive macrophytes are typically faster growing and produce more biomass than native species (Herb & Stefan, 2006;Kennedy, Horth, & Carr, 2009). Macrophyte productivity impacts carbon (C) budgets of freshwater lakes directly via photosynthesis and autotrophic respiration and indirectly due to the degradation of plant litter (Carmichael, Bernhardt, Brauer, & Smith, 2014;Grasset, Abril, Guillard, Delolme, & Bornette, 2016). Therefore, significant changes in life forms of primary producers, such as those resulting from plant invasions, have the potential to change the net C flux of a lake (Attermeyer et al, 2016).…”