Tidal coastal wetlands, common home to seagrasses and salt marshes, are relevant carbon sinks due to their high capacity to sequester and store organic carbon (OC) in their sediments. Recent studies demonstrated that the spatial variability of the OC stocks and sequestration rates within the same wetland system can be significant. Some of the environmental drivers of this spatial variability remain understudied and their specific importance can be site dependent. Here we investigated the role of bed elevation, hydrodynamics (e.g., current velocity), and vegetation habitat type (salt marshes and seagrasses) on the sedimentary OC stocks  at the mesotidal wetland of the Ria Formosa coastal lagoon, in South Portugal. Results showed that two vectors of spatial variation need to be considered to obtain accurate blue carbon maps: (1) the bed elevation that imposes a decrease of the hydroperiod and thus the zonation of vegetation species and habitats, and (2) the spatial variation along the channels of the lagoon, which imposes a gradient in the current flow velocity magnitude. This allowed us to create the first blue carbon map of the Ria Formosa lagoon by combining site-specific hydrodynamic datasets, wetland habitat distribution, and sediment geochemical data (OC stocks and sequestration rates) for intertidal seagrasses and saltmarshes. Our study emphasizes the importance of considering multiple environmental drivers and spatial variability for regional estimations of blue carbon stocks in wetlands.

Primary Presenter: Carmen Barrena de los Santos, Centre of Marine Sciences of Algarve (cbsantos@ualg.pt)

Authors:

Carmen B de los Santos, Centre of Marine Sciences of Algarve (CCMAR)  (cbsantos@ualg.pt)

Marcio Martins, Centre of Marine Sciences of Algarve (CCMAR)  (mfcmartins@ualg.pt)

Ana Rita Carrasco, University of Algarve  (azarcos@ualg.pt)

Paula Ito, Centre of Marine Sciences of Algarve (CCMAR)  (paito@ualg.pt)

Simon von Sachsen-Coburg und Gotha, Centre of Marine Sciences of Algarve (CCMAR)  (ssgotha@ualg.pt)

Aurora Ricart, Instituto de Ciencias del Mar - CSIC  (amricart@icm.csic.es)

Pere Masque, International Atomic Energy Agency (IAEA)  (p.masque-barri@iaea.org)

Rui Santos, Centre of Marine Sciences of Algarve (CCMAR)   (rosantos@ualg.pt)