Year-round CO2 emissions from the drawdown area of a tropical reservoir: Strong seasonal and spatial variation
Ícaro Barbosa,
José R. Paranaíba,
Sebastian Sobek,
Sarian Kosten,
Rafael M. Almeida,
Vitor Duque,
Natália Mendonça,
Nathan Barros,
Raquel Mendonça
Affiliations
Ícaro Barbosa
Aquatic Ecology Laboratory, Biology Department, Federal University of Juiz de Fora, Brazil; Department of Aquatic Ecology and Environmental Biology, Radboud Institute for Biological and Environmental Sciences, Radboud University, Nijmegen, Netherlands; Corresponding author at: Aquatic Ecology Laboratory, Biology Department, Federal University of Juiz de Fora, Brazil.
José R. Paranaíba
Aquatic Ecology Laboratory, Biology Department, Federal University of Juiz de Fora, Brazil; Department of Aquatic Ecology and Environmental Biology, Radboud Institute for Biological and Environmental Sciences, Radboud University, Nijmegen, Netherlands
Sebastian Sobek
Department of Ecology and Genetics, Limnology, Uppsala University, Sweden
Sarian Kosten
Department of Aquatic Ecology and Environmental Biology, Radboud Institute for Biological and Environmental Sciences, Radboud University, Nijmegen, Netherlands
Rafael M. Almeida
School of Earth, Environmental, and Marine Sciences, The University of Texas Rio Grande Valley, Edinburg, TX, USA
Vitor Duque
Aquatic Ecology Laboratory, Biology Department, Federal University of Juiz de Fora, Brazil
Natália Mendonça
Aquatic Ecology Laboratory, Biology Department, Federal University of Juiz de Fora, Brazil
Nathan Barros
Aquatic Ecology Laboratory, Biology Department, Federal University of Juiz de Fora, Brazil
Raquel Mendonça
Aquatic Ecology Laboratory, Biology Department, Federal University of Juiz de Fora, Brazil
A growing body of literature points to drawdown areas as important sources of atmospheric CO2 within reservoirs. Yet seasonal and temporal patterns of CO2 flux from periodically exposed sediments in drawdown areas remain poorly understood. Here we evaluate the annual and diel (24-hour cycle) variations in CO2 emissions from sediments periodically exposed to the atmosphere. We sampled sediments in the drawdown area of a tropical reservoir, which encompassed two primary adjacent land covers—grassland and forestland—in the watershed of a reservoir located in southeastern Brazil. We also experimentally assessed the effect of rewetting on CO2 emissions from exposed sediments. We found large variations in emissions during all hydrological periods (from 10 to 10116 mg C/m−2(−|-) d-1), except for the late rainy period. Land use and how distant dry sediments were from the open water significantly affected drawdown CO2 emissions, with higher emissions occurring in areas surrounded by forest than those adjacent to grassland. Our diel-cycle analysis did not show significant variation of emissions over daily cycles. Furthermore, a rewetting experiment indicated a significant increase in emissions 30 min after the onset of the rewetting event. Although drawdown areas only cover 20 % of the reservoir’s area, they account for 80 % of the reservoir’s total CO2 emissions. Ultimately, single-time measurements can lead to considerable underestimation (up to 52 %) or overestimation (up to 190 %) of whole-reservoir CO2 emissions.
