Contribution of Doñana Wetlands to Carbon Sequestration

Edward P Morris,Eduardo Costas,Javier Ruiz,Jordi Figuerola,Pablo Rodriguez,Susana Flecha,Emma Huertas,Gabriel Navarro,Tomoya Iwata

doi:10.1371/journal.pone.0071456

Abstract

Inland 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 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 transport was derived. Semi-permanent ponds adjacent to the large Guadalquivir estuary acted as mild sinks, whilst temporal wetlands were strong sources of (−0.8 and 36.3 ). 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 ). Overall, Doñana's water bodies were a net annual source of (5.2 ). Up–scaling clarified the overwhelming contribution of seasonal flooding and allochthonous organic matter inputs in determining regional air-water gaseous transport (13.1 ). Nevertheless, this estimate is about 6 times < local marsh net primary production, suggesting the system acts as an annual net 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.

Highlights

IntroductionInland and transitional (i.e., neither fully open coastal nor enclosed or flowing freshwater) aquatic systems are hotspots for biogeochemical transformations, and in particular play an important, previously under appreciated, role in global carbon (C) cycling [1,2,3,4]
Inland and transitional aquatic systems are hotspots for biogeochemical transformations, and in particular play an important, previously under appreciated, role in global carbon (C) cycling [1,2,3,4]
The total terrestrial organic carbon (OC) imported to inland waters is in the order of 2.9 Pg y{1, which is comparable in magnitude to the terrestrial C sink for anthropogenic emissions [1] and terrestrial net ecosystem production [5]

Summary

Introduction

Inland and transitional (i.e., neither fully open coastal nor enclosed or flowing freshwater) aquatic systems are hotspots for biogeochemical transformations, and in particular play an important, previously under appreciated, role in global carbon (C) cycling [1,2,3,4]. Current estimates suggest that lakes, reservoirs, rivers, estuaries, ponds, streams and wetlands make a substantial contribution to global air-water C fluxes, long-term C accumulation in sediments and may play a role in regulating the climate [5,6,7]. Lakes [8,9,10], reservoirs [11], rivers [12], estuaries [13,14] and streams [15] make up the majority of these estimates, with each aquatic component contributing between 10 to 30% of the present total inlandtransitional air-water CO2 flux [5,6]. Recent studies suggest strong scale–dependence of fluxes [4,18], reinforcing the need for detailed data coverage

Methods

Results

Conclusion