![]() ![]() It is tall, sturdy, broad-leaved, and one of the main components of peat. Smooth cordgrass (Spartina alterniflora) dominates the low marsh all the way down to the estuary’s edge. Plants from one marsh zone are never found in the other. Those with higher tolerances are found in the low marsh, and those with lower tolerances to salt are found in the high marsh zones. Plants living in salt marshes have different tolerances to salt. The more often an area is flooded, the more saline it has. The high marsh usually floods about twice a month during very high tides associated with new and full moons. The difference in elevation between these two areas is usually only a few centimeters, but for the plants that inhabit each of these zones, a few centimeters makes a world of difference. Marshes are divided into distinct zones, the high marsh and the low marsh. However, these plants do not grow together in the same area. Salt marshes are covered with salt-tolerant plants, or halophytes, like salt hay, black rush, and smooth cordgrass. Hypoxia promotes the growth of bacteria which produce the rotten-egg smell that is attributed to marshes and mud flats. Because salt marshes are waterlogged and contain lots of decomposing plant material, oxygen levels in the peat are extremely low-a condition called hypoxia. Peat is waterlogged, root-filled, and very spongy. Peat is made of decomposing plant matter that is often several feet thick. They are marshy because their ground is composed of peat. Salt marshes are salty because they are flooded by seawater every day. Composed of fine silts and clays, mud flats harbor burrowing creatures including clams, mussels, oysters, fiddler crabs, sand shrimp, and bloodworms. ![]() Low-lying areas of the marsh are often covered with large, flat expanses of mud called mud flats. Salt-marsh snails and green crabs are some of the creatures found in pools scattered across the marsh. Pools are generally deeper than pannes, and retain water all year long. Glasswort, a plant tolerant to very high salt concentrations, is one of the only organisms able to survive in salt pannes. When the seawater evaporates, the salts remain and accumulate over many tidal cycles. Pannes retain seawater for very short periods of time. Salt pannes are shallow depressions that contain very high concentrations of salt. Between the levees and tidal creeks are marsh flats, which contain pools and salt pannes. Levees are areas of higher ground that border marsh creeks. West Coast, and one of only a few that is similar in size to those found on the East Coast. San Francisco Bay is one of the largest estuaries on the U.S. In these areas, estuaries with very little freshwater input often become hypersaline, or super salty.Īlong the Pacific Coast of the United States, from northern California to Alaska, coastal rivers flow quickly out of the mountains and into very small estuaries. Along the Texas coast, barrier islands protect estuaries that have formed narrow lagoons with small openings to the Gulf of Mexico. Along the southern coast of Florida and lining the Gulf of Mexico are extensive mazes of mangrove forests, also called mangals.įrom northwestern Florida to the Texas coast are long, narrow, sandy barrier islands and shallow estuaries lined with marshes. In this region, estuarine habitats cover large areas along tidal rivers, and salt marshes reach far inland. As one travels further south, the Atlantic Coast becomes much sandier, and barrier beaches enclose huge bays or sounds. ![]() In New England, salt-tolerant grasses fill salt marshes along the shores of tidal rivers. Animation shows low tide, medium tide, high tide, and very high tide.Įxamples of nearly every type of estuarine habitat exist along the coastline of the United States. ![]()
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