What are Salt Marshes?
Salt marshes are coastal wetlands that are flooded and drained by salt water brought in by the tides. They are marshy because the soil may be composed of deep mud and peat. Peat is made of decomposing plant matter that is often several feet thick. Peat is waterlogged, root-filled, and very spongy. Because salt marshes are frequently submerged by the tides and contain a lot of decomposing plant material, oxygen levels in the peat can be extremely low—a condition called hypoxia. Hypoxia is caused by the growth of bacteria which produce the sulfurous rotten-egg smell that is often associated with marshes and mud flats. Salt marshes occur worldwide, particularly in middle to high latitudes. Thriving along protected shorelines, they are a common habitat in estuaries. In the U.S., salt marshes can be found on every coast. Approximately half of the nation's salt marshes are located along the Gulf Coast. These intertidal habitats are essential for healthy fisheries, coastlines, and communities—and they are an integral part of our economy and culture. They also provide essential food, refuge, or nursery habitat for more than 75 percent of fisheries species, including shrimp, blue crab, and many finfish. Salt marshes also protect shorelines from erosion by buffering wave action and trapping sediments. They reduce flooding by slowing and absorbing rainwater and protect water quality by filtering runoff, and by metabolizing excess nutrients.
Our Salt Marshes are Valuable
Salt marshes are too often considered to be worthless, however. Salt marshes provide nursery areas for fishes, shellfish, and crustaceans. These plants have extensive root systems which enable them to withstand brief storm surges, buffering the impact on upland areas. Salt marshes also act as filters. Tidal creeks meander through the marshes transporting valuable nutrients as well as pollutants from upland development. Salt marshes can absorb, or trap, some of these pollutants, reducing the pollutant load entering estuaries. Salt marshes also prevent sediments from washing offshore, often creating more land on which salt marshes can grow.
Salt Marsh Losses in Florida
Salt marsh systems are dynamic, constantly changing. Society, however, emphasizes stability and permanence. As a result, salt marshes have been drained or filled with silt, sand, or refuse to an elevation at which they can no longer survive. It is estimated that in Florida at least 60,000 acres, or 8 percent, of estuarine habitat has been lost to permitted dredge and fill activities. The Florida Marine Research Institute is studying changes in Florida's coastal habitats. Scientists can evaluate changes by comparing aerial photographs of the coast in the 1940's, 1950's, and 1980's. Too frequently, the changes observed show loss of fisheries habitats. Salt marsh loss has occurred in Florida's five northeast counties, which contain 11 percent of the State's total salt marsh acreage. The primary loss in Nassau County occurred because of dredging for the Intracoastal Waterway. Duval County has been impacted even more severely by human activity. Extending 3.5 miles on either side of St. John's Inlet and 10 miles up the St. John's River, analysis indicated a 36 percent loss of marsh habitat. The loss is primarily due to dredge and fill of marsh habitat since 1943.
At the posted coordinates you will find a beautiful example of a salt marsh. You will also see an informational sign.
Acording to the informational sign:
1. What geological aspects of the salt marsh limit the biodiversity of plants within the marsh?
2. What type of soil are the berms created out of?
3. Do you see any evidence of soil erosion or accumulation today?
4. Describe the soil at your feet.