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

Congo Basin lakes Mai Ndombe and Tumba are major CO 2 sources. Here we show that their dissolved inorganic carbon is some 2,170–3,515 14 C 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 CO 2 is transported to the lakes and outgassed, linking these immense ancient stores to the modern carbon cycle.