Temperate reservoirs are large carbon sinks and small CO2 sources: Results from high‐resolution carbon budgets. Issue 1 (27th January 2013)

• Record Type: Journal Article
• Authors: Knoll, Lesley B.; Vanni, Michael J.; Renwick, William H.; Dittman, Elizabeth K.; Gephart, Jessica A.
• Is Part Of: Global biogeochemical cycles. Volume 27:Issue 1(2013)
• Page Start: 52
• Page End: 64
• Publication Date: 2013-01-27
• Subjects: Biogeochemical cycles -- Periodicals; Electronic journals; 577.1405
• DOI: 10.1002/gbc.20020
• Languages: English
• ISSNs: 0886-6236

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <p id="gbc20020-para-0001">[1] Sediment organic carbon (C) burial and CO<sub>2</sub> fluxes in inland waters are quantitatively important in regional and global carbon budgets. Estimates of C fluxes from inland waters are typically based on limited temporal resolution despite potential large variations with season and weather events. Further, most freshwater C budget studies have focused on natural soft‐water lakes, while reservoirs and hard‐water systems are globally numerous. Our study quantifies C fluxes in two hard‐water, human constructed reservoirs (Ohio, USA) of contrasting watershed land use (agriculture vs. forest) using high‐resolution mass balance budgets. We show that during a dry summer, C retention and export via the dam were reduced compared to a wet summer. Both reservoirs were net CO<sub>2</sub> sources during a wet summer, but CO<sub>2</sub> sinks during a dry summer. Despite weather‐related summer differences, annual C fluxes within each reservoir were similar between years. Both reservoirs appear to be net autotrophic despite often being CO<sub>2</sub> sources based on budgets. This is likely because CO<sub>2</sub> fluxes in our hard‐water reservoirs were more strongly associated with DIC than DOC. Using our C fluxes and statewide watershed land use, we determined the regional importance of Ohio reservoirs in OC burial and CO<sub>2</sub> emissions. We estimate that Ohio reservoirs bury up to 4 times more OC, but emit <25% of CO<sub>2</sub>, than predicted based on their area and recent global mean estimates in lentic ecosystems. Our results provide evidence that moderately old (~50 years), temperate hard‐water reservoirs are important OC sinks but contribute little to CO<sub>2</sub> emissions.</p> </abstract>