Saltmarshes can contribute to climate change mitigation and adaptation against sea level rise in coastal areas thanks to their sediment and organic carbon (C_org) accretion capacity. Yet, vast areas of estuarine saltmarshes have been totally or partially transformed during the last century due to human interventions (e.g. tidal restriction and land reclamation), leading to changes in both the community structure and the ecological functions. Within the scope of the European project LIFE ADAPTA BLUES, we retrospectively assessed the impact of tidal restriction and/or land reclamation in estuarine saltmarshes carbon sinks and soil accretion rates. We do so by examining differences in soil accumulation rates, and organic carbon sequestration rates during the last century across saltmarshes under different levels of human transformation in the north of Spain. Soil and C_org accumulation rates since 1960 across saltmarshes examined ranged from 0.09 to 0.29 cm y^-1 and from 6 to 109 g C_org m^-2 y^-1, respectively. The results found show that tidal restriction impacted C_org storage and the capacity of saltmarshes to adapt to sea level rise by reducing between 70 and 95 % the C_org accumulation rates and between 75 and 81% the sediment accretion rates of transformed saltmarshes, compared to non-transformed ones. This study showcases the benefits of tidal reintroduction in drained estuarine settings for climate change mitigation and adaptation, while providing baseline data for the implementation of Blue Carbon restoration projects.

Primary Presenter: Inés Mazarrasa, IHCantabria (mazarrasai@unican.es)

Authors:

Óscar Serrano, Center of Advanced Studies of Blanes, CEAB-CSIC  (oserrano@ceab.csic.es)

Araceli Puente, Environmental Hydraulics Institute of the University of Cantabria, IHCantabria  (araceli.puente@unican.es)

María Recio, Environmental Hydraulics Institute of the University of Cantabria, IHCantabria  (maria.recio@unican.es)

Pere Masqué, Marine Environment Laboratories, International Atomic Energy  (pere.masque@uab.cat)

José Juanes, Environmental Hydraulics Institute of the University of Cantabria, IHCantabria  (antonio.juanes@unican.es)