Carbon Burial in Young Tropical Reservoirs Is Higher at Lower Latitudes*

Man-made environments such as tropical hydroelectric reservoirs alter the preexisting carbon (C) cycle and remove C from circulation through burial in sediments. Carbon burial (CB) was measured using the silica-tracer method during four field surveys in the less than six-year-old Belo Monte tropical reservoir. Fresh C sedimentation was also measured. Belo Monte’s CB median rate 276 (n = 84;min 0;max 352,625 mg C·m-2·d-1) is within the range (230 to 436 mg C·m-2·d-1) of CB rates measured further downstream at the Xingu Ria and higher than the averaged over 50 years oceanic rate 244 mg C·m-2·d-1 estimated for an increasingly deoxygenated ocean. Carbon burial median rates of tropical reservoirs with similar age and trophic state correlate inversely with latitude at a rate of 17.5 mg C·m-2·d-1 per degree. Carbon burial efficiency of these reservoirs correlates positively with latitude at a ratio of 0.22% per degree.