page_title: Everglades National Park
section_title: Freshwater sloughs and marl prairies
hierarchical_section_title: Everglades National Park / Ecosystems / Freshwater sloughs and marl prairies
caption_attribution_description: Alligator dans le parc national des Everglades
context_page_description: Everglades National Park is an American national park that protects the southern twenty percent of the original Everglades in Florida. The park is the largest tropical wilderness in the United States, and the largest wilderness of any kind east of the Mississippi River. An average of one million people visit the park each year. Everglades is the third-largest national park in the contiguous United States after Death Valley and Yellowstone. UNESCO declared the Everglades & Dry Tortugas Biosphere Reserve in 1976, and listed the park as a World Heritage Site in 1979, while the Ramsar Convention included the park on its list of Wetlands of International Importance in 1987. Everglades is one of only three locations in the world to appear on all three lists.
  Most national parks preserve unique geographic features; Everglades National Park was the first created to protect a fragile ecosystem. The Everglades are a network of wetlands and forests fed by a river flowing 0.25 miles per day out of Lake Okeechobee, southwest into Florida Bay.
context_section_description: Freshwater sloughs are perhaps the most common ecosystem associated with Everglades National Park. These drainage channels are characterized by low-lying areas covered in fresh water, flowing at an almost imperceptible 100 feet (30 m) per day. Shark River Slough and Taylor Slough are significant features of the park. Sawgrass growing to a height of 6 feet (1.8 m) or more, and broad-leafed marsh plants, are so prominent in this region that they gave the Everglades its nickname "River of Grass", cemented in the public imagination in the title for Marjory Stoneman Douglas's book (1947), which culminated years of her advocacy for considering the Everglades ecosystem as more than a "swamp". Excellent feeding locations for birds, sloughs in the Everglades attract a great variety of waders such as herons, egrets, roseate spoonbills (Platalea ajaja), ibises and brown pelicans (Pelecanus occidentalis), as well as limpkins (Aramus guarauna) and snail kites that eat apple snails, which in turn feed on the sawgrass. The sloughs' availability of fish, amphibians, and young birds attract a variety of freshwater turtles, alligator (Alligator mississippiensis), water moccasin (Agkistrodon piscivorus conanti), and eastern diamondback rattlesnake (Crotalus adamanteus).
  Freshwater marl prairies are similar to sloughs but lack the slow movement of surface water; instead, water seeps through a calcitic mud called marl. Algae and other microscopic organisms form periphyton, which attaches to limestone. When it dries it turns into a gray mud. Sawgrass and other water plants grow shorter in freshwater marl than they do in peat, the other type of soil in the Everglades which is found where water remains present longer throughout the year. Marl prairies are usually under water from three to seven months of the year, whereas sloughs may remain submerged for longer than nine months and sometimes remain under water from one year to the next. Sawgrass may dominate sloughs, creating a monoculture. Other grasses, such as muhly grass (Muhlenbergia filipes) and broad-leafed water plants can be found in marl prairies. Animals living in the freshwater sloughs also inhabit marl prairies. Marl prairies may go dry in some parts of the year; alligators play a vital role in maintaining life in remote parts of the Everglades by burrowing in the mud during the dry season, creating pools of water where fish and amphibians survive from one year to the next. Alligator holes also attract other animals who congregate to feed on smaller prey. When the region floods again during the wet season, the fish and amphibians which were sustained in the alligator holes then repopulate freshwater marl prairies.
caption: Alligators thrive in freshwater sloughs and marl prairies.
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