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Vertical accretion and relative sea level rise in the Ebro Delta wetlands (Catalonia, Spain)

Abstract:

The Ebro Delta in Catalonia, Spain is an ecologically and commercially important wetland system under threat from sea level rise and marsh subsidence. Our principal hypothesis was that a brackish marsh that receives inorganic sediments and fresh water amendments from the Ebro River would exhibit significantly higher rates of soil accretion, resulting in a greater resistance to subsidence and sea level rise compared to isolated salt marsh habitats with no river subsidy. Marsh sites representative of the wetland ecosystems found in the Ebro Delta were selected based on plant community type, porewater salinity, and landscape position. The results supported the research hypothesis, suggesting that a brackish marsh that receives river subsidies exhibited a significantly higher (F 3,4 = 31.6, P<0.01) rate of vertical accretion compared to more hydrologically-isolated salt marsh systems. Accretion data showed that only the riverineinfluenced brackish marsh site met the minimum pbkp_redicted rate of relative sea level rise (RSLR range of 5-8 mmyr -1) for the Ebro Delta. This research provides the first quantitative record of marsh subsidence and accretion dynamics in the Ebro Delta using Surface Elevation Tables (SET), marker horizons, and 210Pb techniques, and also illustrates the importance of sediment and fresh water subsidies in deltaic environments. © Society of Wetland Scientists 2010.