Shallow lakes under alternative states differ in the dominant greenhouse gas emission pathways

Abstract

Over the past decades, shallow lakes of the Pampean Plain, Argentina, have been shifting from clear vegetated to turbid phytoplanktonic states due to anthropic pressures. It is not clear, though, if this change in state also involves a change in the overall CO 2 and CH 4 balance of these lakes. Therefore, the main objective of this work was to assess potential differences in the C gas (CH 4 and CO 2 ) balance of shallow lakes under contrasting states-clear vegetated and turbid phytoplanktonic. We sampled two clear and two turbid shallow lakes in the Pampean region along an annual cycle and we measured all of the major C gas emission pathways: diffusive and ebullitive fluxes and also emissions from emergent vegetated habitats. CO 2 and CH 4 diffusive, ebullitive and vegetated habitat fluxes were comparable between states, but they differed in their relative contribution to the C gas balance because of differences in the coverage of the habitats associated to these pathways. Mean annual, area-weighted CO 2 and CH 4 fluxes of clear lakes were 41.9 AE 19.0 and 15.4 AE 18.5 mmol m À2 d À1 , respectively, and 7.7 AE 7.3 and 17.9 AE 19.8 mmol m À2 d À1 for CO 2 and CH 4 fluxes, respectively, for turbid lakes. Despite major differences in the relative contribution of the emission pathways between states, there was a remarkable convergence between states in total greenhouse gas emissions when expressed in terms of mean annual CO 2 equivalent greenhouse gas flux.

High Intra‐Seasonal Variability in Greenhouse Gas Emissions From Temperate Constructed Ponds

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Seasonal and spatial variations of greenhouse gas (CO2, CH4 and N2O) emissions from urban ponds in Brussels

“…Yet, the equilibrium between the prevalence of macrophytes and phytoplankton entails a gradual shift rather than an abrupt process and is influenced by additional factors other than nutrient levels (Van Nes et al, 2002;Davidson et al, 2023). It can be hypothesized that water bodies with a dominance of phytoplankton and a dominance of macrophytes should have different GHG dynamics, although this has seldom been tested (Harpenslager et al, 2022 ;Baliña et al, 2023).…”

Influence of wind strength and direction on diffusive methane fluxes and atmospheric methane concentrations above the North Sea

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