The temperate coastal wetland dominated by salt-tolerant grasses is a salt marsh.
Salt marshes form along sheltered coastlines, estuaries, and tidal flats where seawater regularly floods low-lying land. Their plants must tolerate salt, waterlogging, shifting sediments, low oxygen in the mud, and periodic submersion. In many temperate marshes, cordgrass is especially important; in North America, smooth cordgrass commonly dominates the low marsh closest to tidal water.
Salt marsh vegetation is arranged in zones. Frequently flooded lower areas support the most salt-tolerant plants, while higher sections may contain salt hay, rushes, sedges, glassworts, and shrubs. Plant roots help stabilize mud and trap sediment, gradually building the marsh surface.
These wetlands are highly productive nurseries for fish and shellfish and provide feeding and nesting habitat for shorebirds. They also store organic carbon and help reduce coastal flooding and erosion. A salt marsh is distinct from a mangrove swamp, which is dominated by salt-tolerant trees and is most characteristic of tropical and subtropical shores. Coral reefs and seagrass beds are marine ecosystems, not grass-dominated tidal marshes.