The influence of eutrophication on methane production and its potential as a carbon source for zooplankton

Methane constitutes a minor part in entire greenhouses emission, nevertheless its global warming potential is 20-30 times higher than carbon dioxide. Moreover, methane production and emission increases with eutrophication, and it has been demonstrated to serve as a carbon source for pelagic food webs. The methane oxidising bacteria (MOB) are the only group, which is able to utilize methane, as their sole source of carbon and energy and make a link between methane producers and higher food chain levels. However, the environmental controls of this alternative carbon source for plankton community in lakes with different trophic statuses are still poorly understood. Here we evaluated differences in fluxes of CH4 and its potential as a carbon source for zooplankton in relation to the trophy state of two lakes. For this purpose two morphologically similar lakes with different trophy levels were investigated to determine methane efflux as well as zooplankton community structure and carbon stable isotope ratios in order to determine sources (C/C). The results revealed that C-CH4 is incorporated into zooplankton through MOB community. Based on literature C-CH4 has lower share of total carbon built into zooplankton in environments with higher trophy. However, our result showed that this process is more sophisticated and depends on food selectivity and vertical distribution of zooplankton members. This research was funded by National Science Centre in Poland, project no. UMO-2015-18/M/NZ8/00119.