Millennial-aged peat carbon outgassed by large humic lakes in the Congo Basin

Congo Basin lakes Mai Ndombe and Tumba are major CO2 sources. Here we show that their dissolved inorganic carbon is some 2,170–3,515 14C years old and partially (39–40%) originates from the surrounding peatlands. This implies a loss pathway for peat carbon, in which microbes respire old carbon within the peat and the resulting CO2 is transported to the lakes and outgassed, linking these immense ancient stores to the modern carbon cycle.