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Volume 13, issue 11
Biogeosciences, 13, 3331–3342, 2016
https://doi.org/10.5194/bg-13-3331-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 13, 3331–3342, 2016
https://doi.org/10.5194/bg-13-3331-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 07 Jun 2016

Research article | 07 Jun 2016

Organic carbon burial efficiency in a subtropical hydroelectric reservoir

Raquel Mendonça1,2, Sarian Kosten3, Sebastian Sobek2, Simone Jaqueline Cardoso1, Marcos Paulo Figueiredo-Barros4, Carlos Henrique Duque Estrada1, and Fábio Roland1 Raquel Mendonça et al.
  • 1Laboratory of Aquatic Ecology, Department of Biology, Federal University of Juiz de Fora, Juiz de Fora, Brazil
  • 2Department of Ecology and Genetics, Limnology, Uppsala University, Uppsala, Sweden
  • 3Aquatic Ecology & Environmental Biology, Institute of Water and Wetland Research, Radboud University, Nijmegen, the Netherlands
  • 4Laboratório de Limnologia, Núcleo em Ecologia e Desenvolvimento Sócio Ambiental de Macaé (NUPEM), Universidade Federal do Rio de Janeiro, Macaé, Brazil

Abstract. Hydroelectric reservoirs bury significant amounts of organic carbon (OC) in their sediments. Many reservoirs are characterized by high sedimentation rates, low oxygen concentrations in bottom water and a high share of terrestrially derived OC, and all of these factors have been linked to a high efficiency of OC burial. However, investigations of OC burial efficiency (OCBE, i.e., the ratio between buried and deposited OC) in reservoirs are limited to a few studies, none of which include spatially resolved analyses. In this study we determined the spatial variation in OCBE in a large subtropical reservoir and related it to sediment characteristics. Our results show that the sediment accumulation rate explains up to 92 % of the spatial variability in OCBE, outweighing the effect of other variables, such as OC source and oxygen exposure time. OCBE at the pelagic sites varied from 48 to 86 % (mean 67 %) and decreased towards the dam. At the margins, OCBE was lower (9–17 %) due to the low sediment accumulation in shallow areas. Our data show that the variability in OCBE both along the rivers–dam and the margin–pelagic axes must be considered in whole-reservoir assessments. Combining these results with a spatially resolved assessment of sediment accumulation and OC burial in the studied reservoir, we estimated a spatially resolved mean OC burial efficiency of 57 %. Being the first assessment of OCBE with such a high spatial resolution in a reservoir, these results suggest that reservoirs may bury OC more efficiently than natural lakes.

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Hydroelectric reservoirs in the tropics emit greenhouse gases but also bury carbon in their sediments. We investigated the efficiency of organic carbon (OC) burial in a large tropical reservoir, using spatially resolved measurements of sediment accumulation, and found that more than half (~ 57 %) of the OC deposited onto the sediment is buried. This high efficiency in OC burial indicates that tropical reservoirs may bury OC more efficiently than natural lakes.
Hydroelectric reservoirs in the tropics emit greenhouse gases but also bury carbon in their...
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