Shallow surface elevation changes in two tropical seagrass meadows

The ability of seagrass meadows to reduce surface erosion and maintain or increase surface elevation is recognised as an important ecological function, which is expected to help protect coastlines. However, much of the evidence supporting this expectation is limited to large, broad leaf, subtidal populations of seagrass from temperate regions. In this study, we examined the capacity of shorter-stature, intertidal seagrasses to influence sediment deposition and shallow surface elevation change compared to unvegetated surfaces at two locations in Singapore. At each location, sediment supply, sediment deposition and surface elevation change were measured over 270 days, a temporal period covering two monsoonal seasons. The levels of these factors were compared among locations and seasons. Overall, surface elevation in vegetated areas increased by 0.40 ± 0.26 cm, while surface elevation in unvegetated areas declined by 0.34 ± 0.31 cm. We also explored the influence of key meadow characteristics on sediment deposition and surface elevation change, and found that surface elevation increased with aboveground biomass, while sediment deposition increased with areal production, leaf turnover rate and belowground biomass. These results suggest that short-term sediment deposition and broader net surface elevation increases moderately in the presence of seagrass compared to unvegetated areas, and highlight the potential of intertidal, short-stature seagrasses such as Cymodocea rotundata to increase surface elevation.