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Wetlands exist on every continent, except Antarctica. [3] The water in wetlands is either freshwater, brackish or saltwater. [2] The main types of wetland are defined based on the dominant plants and the source of the water. For example, marshes are wetlands dominated by emergent herbaceous vegetation such as reeds, cattails and sedges.
The wetlands are classified into three major classes: Marine/coastal wetlands; Inland wetlands; Human-made wetlands; These are further subdivided by the type of water: fresh / saline / brackish / alkaline; and may be further classified by the substrate type of other characteristics.
Fen, being a distinct type of wetland, shares many biogeochemical characteristics with other wetlands. [19] Like all wetlands, they play an important role in nutrient cycling because they are located at the interface of aerobic (oxic) and anaerobic (anoxic) environments. [11]
A wetland is a land area that is saturated with water, either permanently or seasonally, such that it takes on the characteristics of a distinct ecosystem.The primary factor that distinguishes wetlands from other land forms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique hydric soil.
[13] [14] However, there are characteristics common to all bogs that provide a broad definition: [7] Peat is present, usually thicker than 30 centimetres (12 in). The wetland receives most of its water and nutrients from precipitation (ombrotrophic) rather than surface or groundwater (minerotrophic). The wetland is nutrient-poor (oligotrophic).
There are three basic types of freshwater ecosystems: Lentic (slow moving water, including pools, ponds, and lakes), lotic (faster moving water, for example streams and rivers) and wetlands (areas where the soil is saturated or inundated for at least part of the time). [2] [1] Freshwater ecosystems contain 41% of the world's known fish species. [3]
Wetlands generally include swamps, marshes, bogs, and similar areas." [1] [2] [3] Wetlands can be valued in terms of their contributions to ecological, economic and social systems. Wetlands service these systems through multiple processes including water filtration, water storage and biological productivity. [4]
Chemical and nutrient dynamics may differ depending on a minerotrophic wetland’s hydrological setting, which could include water discharge dominated, recharge dominated, or some combination of both. [4] These characteristics also vary seasonally, as average groundwater levels increase and decrease at different times of the year. [8]