Contribution of Doñana Wetlands to Carbon Sequestration

Abstract

Related Digital.CSIC items: http://hdl.handle.net/10261/72209; http://hdl.handle.net/10261/63554.-- The data used for this article is here: http://hdl.handle.net/10261/77418Inland and transitional aquatic systems play an important role in global carbon (C) cycling. Yet, the C dynamics of wetlands and floodplains are poorly defined and field data is scarce. Air-water CO2 fluxes in the wetlands of Doñana Natural Area (SW Spain) were examined by measuring alkalinity, pH and other physiochemical parameters in a range of water bodies during 2010–2011. Areal fluxes were calculated and, using remote sensing, an estimate of the contribution of aquatic habitats to gaseous CO2 transport was derived. Semi-permanent ponds adjacent to the large Guadalquivir estuary acted as mild sinks, whilst temporal wetlands were strong sources of CO2 (−0.8 and 36.3 mmolCO2 m-2 d-1). Fluxes in semi-permanent streams and ponds changed seasonally; acting as sources in spring-winter and mild sinks in autumn (16.7 and −1.2 mmolCO2 m-2 d-1). Overall, Doñana's water bodies were a net annual source of CO2 (5.2 molc m-2 y-1). Up–scaling clarified the overwhelming contribution of seasonal flooding and allochthonous organic matter inputs in determining regional air-water gaseous CO2 transport (13.1 Ggc y-1). Nevertheless, this estimate is about 6 times < local marsh net primary production, suggesting the system acts as an annual net CO2 sink. Initial indications suggest longer hydroperiods may favour autochthonous C capture by phytoplankton. Direct anthropogenic impacts have reduced the hydroperiod in Doñana and this maybe exacerbated by climate change (less rainfall and more evaporation), suggesting potential for the modification of C sequestration.This research was supported by the projects P09–RNM–4744 and 049/2010 funded by the Regional Government of Andalucia and the Spanish Ministry for Agriculture, Food and Environment, respectively. EPM and SF are supported by a JAE DOCTORES 2010 contract and JAE PREDOCTORAL scholarship, respectively, part-funded by the European Union (European Social Fund, ESF2007-2013) and the Spanish Ministry for Economy and Competitiveness.Peer reviewe