Marshes are wetland communities that are dominated by herbaceous plants and occasional shrubs. These communities are typically inundated nearly year-round, and have substrates with a thick organic mantle on the surface. Marshes are usually dominated by herbaceous species, but a marsh that is dominated by grasses or sedges may be considered a graminoid marsh. Grasses usually occur in areas with some part of the year without standing water, but related graminoids (grass-like plants) may be common in areas with prolonged hydroperiods. The graminoid that is probably most common in such areas is saw grass (Cladium jamaicense). Saw grass is a sedge (Cyperaceae) that is commonly found in wetlands with various depths to limestone, often with a significant organic peat layer covering the limestone. This organic layer is usually derived from sawgrass. Other similar communities that are dominated by different grass-like plants may also be graminoid marshes, and would be identified by the graminoid that is the dominant ground cover plant. Marshes are commonly dominated by broad-leafed plants, such as pickerel weed (Pontederia cordata), cat-tail (Typha domingensis or T. latifolia), or duck potato (Sagitaria spp.).
These wetlands have comparatively deep water (1.5 - 2.0 m) during the wet season, and persist as aquatic communities year-round or well into the dry season. These deeper areas provide refugia for fish during dry seasons, when few places are under water, and also tend to concentrate populations of fish and other aquatic animals as water levels decrease with dry weather. Many wading birds, such as wood storks (Mycteria americana) and American egrets (Casmerodius albus) depend on these concentrated prey populations, to find sufficient food for nesting and brood rearing. Soils in our area that commonly support marshes include: Holopaw and Okeelanta Soils, Depressional; Winder, Riviera, Limestone (Liudahl et al. 1998). Saline Marsh Marshes that occur in coastal areas and that are occasionally to frequently affected by marine systems are referenced as Saline Marshes. These communities are influenced by tidal fluctuations so that their soil salinities are higher than inland freshwater systems. Saline marshes that are far inland may be affected by marine waters only during extreme storm tides, such as those associated with hurricanes. This produces a change in salinity very infrequently, but the effects of this change may remain with the marsh community for several years. These communities are usually populated with plants that are typical of freshwater marshes, but that are able to tolerate small increases in salinity. Plants that inhabit these areas include cattail (Typha domingensis), pond apple (Anona glabra) or cord grass (Spartina bakeri). These areas, and other communities inland from coastal systems may be dominated by freshwater almost all of the time, but may still be frequently influenced by tidal changes in water level. In such areas, coastal tides may increase water depth, but the flow of inland fresh water maintains sufficient gradient to keep salt water from flowing inland. In this way, the tidal increase in water depth causes the coastal freshwater system to increase in depth with tide, but salt water itself does not flow far inland.
During the dry season, decreased flow of fresh water allows salt water to flow farther inland. Nearer the coast, tidal systems are more likely to dominate, so that mixing of freshwater and salt water becomes more common. When salt water becomes diluted by fresh water, brackish water results. Communities that are dominated most of the year by brackish water are likely to be dominated by saline marsh with occasional mangrove trees (see above: Mangrove Forests). These saline marshes are often populated by black rush (Juncus romerianus) salt marsh cord grass (Spartina spp), or salt grass (Distichlis spicata). Soils that commonly support saline marshes in our area include: Estero and Peckish Soils, Frequently Flooded; Kesson Muck, Frequently Flooded (Liudahl et al. 1998).