The end of the boardwalk at Kenilworth gives visitors a great look at the freshwater tidal marsh.
Tim Ervin
A marsh is a type of wetland, an area of land where water covers ground for long periods of time. Unlike swamps, which are dominated by trees, marshes are usually treeless and dominated by grasses and other herbaceous plants. In marshes, the high levels of rainfall and runoff lead to high nutrient levels and oxygen availability. This results in a high rate of plant growth and decomposition, which supports a diverse range of aquatic and terrestrial species. However, marshes are also vulnerable to flooding, which can cause erosion and nutrient loss.
There are three types of marshes: tidal salt marshes, tidal freshwater marshes, and inland freshwater marshes. Marshes are also common in deltas, where rivers empty into a larger body of water. Although all are waterlogged and dominated by herbaceous plants, they each have a unique ecosystem.
Saltwater Marshes are found along the coasts.
NPS Photo
Tidal Salt MarshesTidal salt marshes form a grassy fringe near river mouths and bays and along coastlines protected from the open ocean. Ocean tides fill the marsh with salty water and cause the water level to rise and fall twice a day. The marsh is deeper at high tide and shallower at low tide. Plants such as sawgrass and pickleweed can tolerate fluctuating tidal waters, which are too salty for most trees and bushes. Salt marshes maintain biodiversity by providing essential habitats for many organisms, they protect shorelines against storms, and also act as natural pollution filters. Salt marshes are a so-called “blue carbon” ecosystem because they are carbon sinks, sequestering greenhouse gases and playing a role in offsetting climate change. A variety of bird species ranging from raptors to songbirds, survive on the salt marsh grasses and the fish and insects that live there. Some include the osprey, bald eagle, black duck, great blue heron, and belted kingfisher.
The marsh at Kenilworth has a three foot tide come and go all day, everyday.
Tim Ervin
Tidal Freshwater MarshesTidal freshwater marshes lie farther inland than salt marshes but are close enough to the coast to be affected by tidal fluctuations. Like in salt marshes, the water level rises and falls twice every day along with the tides. Tidal freshwater marshes are fed by freshwater streams and do not have a large salt content. They are common boundaries between forests and rivers. Herbaceous plants called sedges dominate the tidal freshwater marsh ecosystem. Sedges include water chestnut and papyrus. For example, Dyke Marsh at George Washington Memorial Parkway near Washington, D.C. has more than 360 different plant species, including water lilies, wild rice, and arrowheads.
Great egrets are often seen in the tidal marsh.
Tim Ervin
Inland MarshesInland freshwater marshes are found along the fringes of lakes and rivers where the water table, the upper surface of underground water, is very high. Vegetation in freshwater marshes depends on the presence of water. Plants establish seeds on a yearly basis and only bloom with annual or biannual flooding of the meadow. Inland salt marshes are threatened by development run-off (agriculture, residential, commercial, roads), habitat alteration (pollution and dumping), and recreational overuse. Inland salt marshes are threatened by invasive species, such as reed grass and purple loosestrife.
