As a result of regional differences in soil, climate, water chemistry, and other factors, the variety of wetlands is unmatched. Wetlands are found on every continent except Antarctica, stretching from the tropical regions to the barren tundra.

Currently, scientists recognize five major wetland systems: marine, estuarine, lacustrine, riverine, and palustrine. These are grouped into two general categories: Coastal (marine and estuarine) and Inland (lacustrine, riverine, and palustrine).

1. COASTAL
1. Marine(near the ocean) - water levels rise and fall with the daily tides
• Bays
• Sounds
• Coastline
2. Estuarine(coastal wetland where fresh and saltwater mix)
• Tidal salt marsh
• Tidal freshwater marshes
• Mangrove swamps
  

1. Palustrine (standing or very slowly flowing water)
• Non-tidal marshes
• Bogs (peatlands)
2. Riverine (flowing water) - see Rivers of Alabama
• Drainage basins along freshwater rivers, streams, and creeks
• Swamps
• Forested swamps
• Shrub swamps
3. Lacustrine (shallow water)
• Low-lying areas surrounding lakes, ponds, and reservoirs
• Wet meadows

Special wetlands: fens, prairie potholes, vernal pools, and pocosins.

Fens – groundwater-fed peat-forming wetlands covered by grasses, sedges, reeds, and wildflowers. Fens typically tend to occur in the Northern U.S. Similar to a bog, they differ in the fact that fens are less acidic and have higher nutrient levels. This enables them to support a more diverse plant and animal community.
(http://www.epa.gov/owow/wetlands/types/fen.html)

Prairie Potholes – develop when snowmelt and rain fill the holes left on the landscape by glaciers. Prairie Potholes also tend to occur in the Northern U.S. and Canada.
(http://www.epa.gov/owow/wetlands/types/pothole.html)

Vernal Pools – spring pools that fill up in spring and dry up in summertime. They are small, temporary and isolated from other wetlands, having either bedrock or a hard clay layer in the soil that helps keep water in the pool. Vernal pools are mainly found out West.
(http://www.epa.gov/owow/wetlands/types/vernal.html)

Pocosins – boggy shrub wetlands that occur along the coastal plain from Virginia to northern Florida. Pocosins are found on waterlogged , nutrient poor, acidic soils, which are maintained by a shallow water table that leaves the soil saturated for the majority of the year.
(http://www.epa.gov/owow/wetlands/types/bog.html#pocosins)

Swamp – Swamps are frequently waterlogged during the growing season, retaining approximately 6 to 12 inches of water. Groundwater is the primary source of water for swamps. This water is either free-standing or slowly moving, occurring mostly along sluggish streams, on flood plains, or in very shallow lake basins. Swamps can further be divided into two types depending on the type of vegetation present: Forested Swamps – when dominated by large hardwood trees such as red maple and ashes or by softwood trees such as cedars and spruce. In the South/Southeast, many swamps contain cypress tress and are often referred to as bottomland hardwood forests.

Shrub Swamps – when dominated by willows, alders, dogwoods, buttonbush, or swamp rose. Many times often found in conjunction with or adjacent to a forested swamp.

Marsh – Marshes are also frequently or continually flooded wetlands that contain water levels from between two inches to two or three feet, but they are distinguished from swamps in that they predominantly contain herbaceous vegetation such as grasses, sedges, worts, or cattails. They frequently occur in poorly drained depressions along streams, in floodplains, and along the boundaries of rivers and lakes. Marshes can also be grouped into two categories:

Salt Marshes – occur along coasts near river mouths, coastal plains, or around protected lagoons. Usually found with estuaries, they consist of salt-tolerant grasses and water levels that fluctuate with the tides. Freshwater Marshes – the most prevalent and widely distributed wetlands in North America. They differ from salt marshes only in their water source, which comes from runoff water from streams, ponds, and lakes instead of from the ocean. Freshwater marshes constitute the best breeding habitat in the country, and they are also important feeding places for many animals.

Marshes often have mineral soils, with coarser soils containing sand in coastal marshes where the waves flow in, while others are made of silt, clay, and dead plant matter.

Bog – not as commonly seen in the South as swamps and marshes are, bogs are sometimes referred to as “peatlands” which lack an overlying layer of mineral soil. Peat is accumulated dead plant matter that decomposes very slowly, making the soil and water highly acidic. Moreover, bogs receive most if not all of their water from precipitation (which lacks the nutrients found in groundwater or runoff), further increasing the acidity in the water and soil. Obviously only plants and animals adapted to these types of conditions are found in a bog, most notably the carnivorous plants. To understand a bog more clearly, a closer look must be taken at how peat forms. There are two primary ways that a bog develops: they can form as sphagnum moss grows over a lake or pond and slowly fills it (called “terrestrialization”), or bogs can form as sphagnum moss blankets dry land and prevents water from leaving the surface (called “paludification”).