Vertical sediment dynamics in Spartina maritima restored, non-restored and preserved marshes

Abstract

Salt marsh restoration projects using cordgrasses are relatively cheap and viable alternatives to improve the environmental quality while stabilizing sediments. This work quantifies the vertical sediment dynamics along the tidal gradient in low marshes in an extensive salt marsh restoration project, 26 months after planting Spartina maritima, in comparison with adjacent non-restored and preserved marshes in the Odiel Marshes (southwest Iberian Peninsula). The vertical sediment dynamics was recorded using markers consisting of an iron structure with two vertical posts and a horizontal crossbar, measuring the distance from the middle point of the crossbar to the sediment surface periodically between March 2009 and March 2011. The sediment dynamics was independent of the marsh elevation, depending mainly on plant cover. Erosion was lower in the S. maritima zone (mean accretion rate between +10 and +27mmyr−1; mean accumulated erosion between +22 and +51mm after 2 yr) than in bare intertidal mudflats (−14 to +12mmyr−1; −36 to +37mm after 2 yr). At higher elevations colonized by Sarcocornia perennis, sediment dynamics changed markedly, depending on marsh type (−10 to 14mmyr−1; −31 to +29mm after 2 yr). Extensive salt marsh plantations using S. maritima behaved in a similar way to natural preserved marshes after ca. 2 yr with a relative cover of 62%, this being a useful tool to stabilize eroding areas in European marshes, since they reduced erosion and increased accretion.