Benthic production, respiration and methane oxidation in Lobelia dortmanna lawns

Isoetid macrophytes such as Lobelia dortmanna and Littorella uniflora are engineering species with an extensive root system and high radial oxygen loss. Despite several studies on these macrophytes, the effect of their oxygenation on methane dynamics has never been investigated. In this study, we hypothesise that isoetids promote dissolved inorganic carbon fixation and methane oxidation in sandy sediments. Our whole-ecosystem approach study lasted 2 years (2013–2014) on two oligo-mesotrophic shallow lakes. Benthic chamber incubations confirmed that, as a result of primary production and methanotrophy, isoetid lawns had consistently lower benthic carbon fluxes than bare sediments. On a daily basis, vegetated areas acted as a carbon sink (−0.7 ± 0.4 g C m −2 days −1 , as DIC + CH 4 ), whereas bare sediments acted as a net source (0.6 ± 0.5 g C m −2 days −1 , as DIC + CH 4 ). Photosynthetic quotients of