Coastal Wetland Examples

Coastal wetland is used broadly here to identify areas where wetland plants inhabit the coastal zone, in either freshwater or saltwater environments of the coastal zone. For this reason, along the continental U.S. coastal zones, it includes vegetated environments such as salt marshes, fresh marshes, bottomland hardwood swamps, and mangrove swamps. In the United States, coastal wetlands extend across nearly 40 million acres and constitute approximately 38% of the total wetlands in the conterminous U.S.

• Marsh: A marsh is a type of wetland that consists of herbaceous plants (plants with leaves and stems) (Figure 3.40). Typically, there is a period of annual dieback or at least a resting period from growth, and the system can be either salt or fresh water in nature.
• Salt Marsh: True salt marsh is strongly affected by the tides of a given area on a daily basis because they are located within the intertidal window of elevation. Along the coast of the U.S., all salt marsh experiences a severe to slight dieback during the winter, but begins growing strongly the following year with the return of warmer temperatures. Typical salt marsh structure includes tidal creeks through the marsh platform, and localized ponds that may hold some water even during very low tides (Figure 3.40, Figure 3.41).
• Fresh Water Marsh: On a global basis, the distribution of coastal-zone fresh water marsh is mostly closely tied to river systems that enter into coastal zones. The steady influx of freshwater into coastal rivers provides an opportunity for fresh-water vegetation to dominate and prevents the incursion of flora that requires some level of salinity (Figure 3.42). The Florida Everglades of Florida in the U.S. represent some of the largest, and perhaps the largest, freshwater marsh in the world.
• Swamp: Forested wetlands with little circulation to nearly stagnant conditions are characteristic of swamps. Freshwater, brackish, and saline water are all possible environmental conditions in a swamp.
• Bottomland Hardwood swamps: In the coastal zone, bottomland hardwood forests are closely linked to the availability of freshwater (Figure 3.42). As a result, most extensive bottomland hardwood swamps are in low lying river flood plains. Occasional flooding of these environments provides sediment to help anchor the vegetation and nutrients that are critical to growth. Excessive flooding or the introduction of saline waters can have serious effects on the health of such systems (Figure 3.43).
• Mangrove Swamps and Forests:Mangrove swamps are distributed through tropical and subtropical regions. There are numerous species of mangroves, but they all represent a plant that is halophytic or salt loving and are associated with other trees and plants that grow within brackish to saline tidal waters. As shown in Figure 3.44, they may consist of a very complicated maze of woody roots and limbs. Depending upon the species of mangrove, very complicated interwoven root structures (Figure 3.45) can develop and provide a significant buffer against erosion and inland progressing waves and storm surges during high energy events. Across the U.S., they are restricted to low-latitude environments because of the species intolerance for cold temperatures.Three different species exist from south Florida along to the Texas Gulf Coast (Figure 3.40),and, in fact, one of the largest mangrove swamps in the world is on Florida's southwest coast where Red Mangrove form structurally resilient coastal environments because of their interlocking woody growth patterns (Figure 3.46).

Figure 3.40: Spartina alterniflora otherwise known as Saltmarsh Cordgrass is widely distributed in salt water marshes along the U.S. Gulf of Mexico and eastern U.S. coast. Excessive periods of either drought or inundation can cause death, and a major concern right now is whether salt water marshes will be able to maintain their necessary elevations during periods of relative sea level rise.
Credit: "Spartina alterniflora". Public domain via Wikimedia Commons

Figure 3.41: Low-lying coastal salt marsh bordered by more upland forest at Lake Clark National Park and Preserve in Alaska, U.S.A. Note the numerous ponds on the interior of the marsh as well the tidal creeks that allow water to rise into and fall out of the marsh through the tidal cycle.
Credit: http://www.fs.fed.us/database/feis/fire_regimes/AK_coastal/all.html NPS/K. Jalone

Figure 3.42: Low-lying fresh water marsh typical of the Gulf Coast and Atlantic States.

Figure 3.43: Poorly drained areas of freshwater environments on the coast can be host to extensive Bottomland hardwood forests. Species within this environment can occasionally be flooded without repercussions for forest health. As with so many other coastal environments, rising sea level also threatens this environment because rising sea level would mean the greater landward incursion of saline-rich marine waters that these species cannot tolerate. Moreover, tree species in these environments are only tolerant of occasional flooding; even excessive periods of major freshwater flooding can damage these ecosystems.

Figure 3.44: Cypress-Tupelo Swamp, a typical bottomland hardwood forest along areas of the northern Gulf Coast and southern Atlantic States of the U.S., although variations in species composition do exist for the mid-Atlantic states. Areas such as this remain partially flooded to fully flooded through the year and may experience periods of higher water levels, as well. There is little to no movement of water, although these environments do have slight daily fluctuations because of tidal influence on their waters. Salt water is, however, not present because of their upslope, inland locations.

Figure 3.45: A very thickly wooded mangrove forest in Palawan, Philippines. Notice the large root structures and muddy substrate into which the mangroves are rooting.
Credit: "Hunting For Worms" by Ceratocentron

Figure 3.46: Picture along the edge of a mangrove shoreline that shows the dense interwoven network of roots. The roots provide support in sometimes very soft substrates and can also help to trap sediment that aids in the stabilization of the plant.
Credit: https://commons.wikimedia.org/wiki/Mangrove#/media/File:Mangroves.jpg