Measuring the role of seagrasses in regulating sediment surface elevation

Abstract

Seagrass meadows provide numerous ecosystem services and their rapid global loss may reduce human welfare as well as ecological integrity. In common with the other ‘blue carbon’ habitats (mangroves and tidal marshes) seagrasses are thought to provide coastal defence and encourage sediment stabilisation and surface elevation. A sophisticated understanding of sediment elevation dynamics in mangroves and tidal marshes has been gained by monitoring a wide range of different sites, located in varying hydrogeomorphological conditions over long periods. In contrast, similar evidence for seagrasses is sparse; the present study is a contribution towards filling this gap. Surface elevation change pins were deployed in four locations, Scotland, Kenya, Tanzania and Saudi Arabia, in both seagrass and unvegetated control plots in the low intertidal and shallow subtidal zone. The presence of seagrass had a highly significant, positive impact on surface elevation at all sites. Combined data from the current work and the literature show an average difference of 31 mm per year in elevation rates between vegetated and unvegetated areas, which emphasizes the important contribution of seagrass in facilitating sediment surface elevation and reducing erosion. This paper presents the first multi-site study for sediment surface elevation in seagrasses in different settings and species.

Blue Carbon Storage Capacity of Temperate Eelgrass (Zostera marina) Meadows

“…A recent study, encompassing both intertidal and subtidal and tropical and temperate seagrass ecosystems showed that presence of seagrass resulted in an average difference in surface elevation rate of 31 mm/year, compared to adjacent unvegetated sediments (Potouroglou et al, ). Furthermore, although not measured in this study, the structure of seagrass meadows can also be a potentially important predictor for the magnitude and source of seagrass C org stocks.…”

Reduced water motion enhances organic carbon stocks in temperate eelgrass meadows

“…). Relative water motion was characterized using the dissolution rates of Plaster of Paris chalk blocks, which integrates the effects of both tidal currents and waves (Potouroglou et al ). We attached preweighed (~ 130 g) plaster blocks to PVC stakes, which were inserted into the sediments such that the blocks were approximately mid‐canopy.…”

Seagrass Impact on Sediment Exchange Between Tidal Flats and Salt Marsh, and The Sediment Budget of Shallow Bays

“…Many studies have documented a decline in the extent of seagrasses for many areas worldwide (Cambridge et al, 1986;Campbell & McKenzie, 2004;Cardoso et al, 2004;Daby, 2003;Gonzalez et al, 2005;Hughes et al, 2004;Morris & Viknstein, 2004;Orth et al, 2006;Polte et al, 2005;Short & Burdick, 1996;Waycott et al, 2005). Seagrasses also impact system morphology due to their capacity to hold sediments and favor deposition (Ganthy et al, 2013;Harlin et al, 1982;Potouroglou et al, 2017). For instance, Ganthy et al (2013) studied sediment transport dynamics in tidal flats in the Arcachon lagoon, measured centimeter-scale accretion rates over seagrass meadow, and found that these were correlated with seasonal growth rates.…”