Wetlands 2: Types of Wetlands in the Top End
WETLANDS 2: Types of Wetlands in the Top End
White Snowflake Lillies (Nymphoides indica), Anbangbang Billabong, Kakadu National Park (Ian Morris)
Desert lakes and watercourses
In Australia's arid interior rainfall anywhere in the large catchment areas causes water to flow down the main channels of intermittent watercourses. These may divide into a number of channels and in places become wider and deeper, forming a chain of connected waterholes and billabongs. Heavy rains cause the waters to spill out into surrounding floodplains where clay pans and salt lakes fill up and cause a population explosion of aquatic invertebrates and small fish species. This in turn attracts waterbirds from other parts of the continent.
Marine wetlands and mangroves
Marine wetlands occur along the coastline in areas of low elevation. They include subtidal seagrass beds, permanent shallow waters less than 6 m at low tide, coral reefs, estuaries, and mangrove communities. The mangroves are of immense scientific importance because of their unique ability to live in a saline environment that would kill most other types of plants. Mangrove communities are mostly found on tidal flats that are protected from wave action, along the banks of tidal rivers, and in sheltered bays and lagoons. They provide high levels of nutrients for offshore ecosystems and are nurseries for many invertebrate and fish species.
Inland river systems
The inland rivers of Australia are part of an ancient, weathered and mostly flat landscape. The main river is often hard to see from the air, because it twists and turns amongst billabongs that mark older courses of the river.
Coastal lagoons and marshes
Paperbarks (Melaleuca spp.), reeds and sedges are the main plants found in the shallow coastal wetlands that may occur in a variety of landforms. Some are adjacent to coastal streams and estuaries whilst other lagoons are located behind coastal dunes. Many are fed by the high water tables often associated with coastal terrain. They vary greatly in salinity, even when adjacent to each other. The waters are usually slow or still, conditions which suit fish such as the Blue-spot Goby () and the Smallmouthed Hardyhead ().
Large storage dams, farm dams, aquaculture ponds, disused quarries and mine workings, wastewater treatment plants, irrigated land, and canals are all included in this category. Research has shown that the diversity of aquatic life in artificial wetlands is far less than that of natural wetlands.
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