Description of salt marshes and intertidal flats
Salt marshes and tidal flats are found in the intertidal zone, the area between the reach of the highest high tide and the lowest low tide, and are subject to varying amounts of flooding by seawater. The ratio of salt marsh to tidal flat in the intertidal zone can vary (Atkinson et al. , 2001) but together, they provide a variety of different habitats for wildlife, including benthic invertebrates, fish and birds. They also provide important ecosystem services to people through coastal protection, water purification, carbon sequestration, food production and recreation (Barbier et al. , 2011).
An example of a coastal system showing variation in habitat and species present across the tidal range [Credit: Petra Dankers. Adapted from: EcoShape].
Tidal flats are large expanses of temporarily exposed soft substrates (sand or mud) that form where sediment deposits, often at the edge of estuaries or in sheltered sections of coasts. A key feature of tidal flats is that they are regularly inundated with water (Healy et al. , 2002), have sufficiently high mud content for the sediment to exhibit cohesive properties (Dyer et al. , 2000) and have no vegetation cover other than occasional seagrass. The International Union for Conservation of Nature (IUCN) classifies tidal flats as shoreline systems within the marine- terrestrial biome (MT1.2; Bishop et al. , 2020). Salt marshes (also known as tidal marshes) are vegetated areas, typically found in the upper parts of the intertidal zone, experiencing less frequent flooding than tidal flats. Salt marshes naturally occur globally but are more well studied in temperate and northern regions. A key feature of salt marshes is the ‘zonation’ of the vegetation, whereby different plant communities establish in bands following bathymetric patterns, depending how tolerant they are of being submerged by saltwater (Davy, 2000). Vegetation is dominated by salt-tolerant forbs, grasses and shrubs, such as Phragmites spp . and Sueda spp . , but not seagrasses (Keith et al. , 2020a). The IUCN classifies salt marshes as brackish tidal systems within the marine-freshwater- terrestrial biome (MFT1.3; Keith et al. , 2020b).
10
Made with FlippingBook - professional solution for displaying marketing and sales documents online