High marsh is a tidal marsh zone located above the Mean Highwater Mark (MHW) which, in contrast to the low marsh zone, is inundated infrequently during periods of extreme high tide and storm surge associated with coastal storms. This zone is impacted by spring tides, which is a bi-monthly lunar occurrence where the high marsh experiences higher inundation levels. The high marsh is the intermittent zone between the low marsh and the uplands, an entirely terrestrial area rarely flooded during events of extreme tidal action caused by severe coastal storms. The high marsh is distinguished from the low marsh by its sandy soil and higher elevation. The elevation of the high marsh allows this zone to be covered by the high tide for no more than an hour a day. With the soil exposed to air for long periods of time, evaporation occurs, leading to high salinity levels, up to four times that of sea water. Areas of extremely high salinity prohibit plant growth altogether. These barren sandy areas are known as "salt pans". Some cordgrass plants do survive here, but are stunted and do not reach their full size.
The high marsh depends on regular tidal activity and inundation to deposit sediments. [1] Sediment deposition facilitates mineral and organic matter buildup and sediment accretion. The minerals and organic matter promote vegetation growth and the sediment accretion promotes heightened elevation growth. [2]
The high marsh is also important to many habitat specialists such as the Saltmarsh Sparrow, Black Rail, American Black Duck, saltmarsh spike-grass, and salt-hay. These specialists rely on the high marsh ecosystem to provide for their biological needs to ensure stable productivity and abundance. [3] [4] Among these biological needs are foraging, mating, nesting, incubation, and brooding.
The Clean Water Act of 1972 was the first act to protect these ecosystems but, due to the absence of protection, many wetlands were converted into farmland and residential land.
Saltmarshes are found in at least 99 countries, as mapped by scientists Mcowen et al. in 2017. [5] Similarly, in 43 countries/territories there are 5,495,089 mapped hectares of saltmarsh. [5] The coterminous United States has many estimates for original wetland content, spanning from 211 to 217 million acres total. [6] Alaska has the highest amount of wetlands, with an estimated 165 million acres originally. [6] The U.S. Department of Interior and the U.S. Fish and Wildlife Service estimate that colonial United States had approximately 392 million acres, with 221 million in the 48 states, 170 million acres in Alaska, and 59,000 acres in Hawaii. [7]
Thomas Dahl reports in Wetlands that from 1780 to 1980 there was a “53-percent loss from the original [wetland] acreage total." [7] Further, United States wetlands experienced a net loss of approximately 60,000 acres per year spanning from 1998 to 2004. This increased to 80,000 acres per year between 2004 and 2009. [7]
The high marsh is one of the most threatened features of wetlands. On average, the United States' coastal areas support high per capita communities. Due to this, these areas face the pressure of development and overdevelopment.
The United States Fish and Wildlife Service (FWS) summarizes data from the Cape Cod National Seashore (CCNS) and states that “there has been a documented shift in the high marsh to low marsh boundary by 100 m (328 ft) upslope between 1984 and 2000 in the ‘Gut’ at Wellfleet, and a loss of 46 percent of the high marsh between 1947 and 2005." [8] This high marsh loss is evident throughout the United States. [7]
Overall, the high marsh is particularly vulnerable to the impacts of climate change and anthropogenic actions, as follows.
This coastal development near marshes may increase the nitrogen and phosphorus concentration leached into waterways, particularly from sewage treatment and systems. [9] Further, due to farmlands, lawns, and golf courses, nitrogen concentrations may also be increased. [10] When the high marsh plants are exposed to a higher concentration of nitrogen and phosphorus, the underground biomass decreases and the aboveground increases, making the ecosystem susceptible to widening and erosion. [8] These higher nutrient concentrations may also lead to eutrophication and fish kills. [11]
Certain tidal restricting infrastructure—such as roadways, dikes, and floodgates—disrupt the natural tidal flow. These restrictions prevent the sediment accretion and nutrient deposition that the high marsh relies on for elevation growth and vegetation health. [2]
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environments and are an example of an ecotone. Estuaries are subject both to marine influences such as tides, waves, and the influx of saline water, and to fluvial influences such as flows of freshwater and sediment. The mixing of seawater and freshwater provides high levels of nutrients both in the water column and in sediment, making estuaries among the most productive natural habitats in the world.
A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently for years or decades or seasonally for a shorter periods. Flooding results in oxygen-free anoxic processes prevailing, especially in the soils. The primary factor that distinguishes wetlands from terrestrial land forms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique anoxic hydric soils. Wetlands are considered among the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal species. Methods for assessing wetland functions, wetland ecological health, and general wetland condition have been developed for many regions of the world. These methods have contributed to wetland conservation partly by raising public awareness of the functions some wetlands provide. Constructed wetlands are designed and built to treat municipal and industrial wastewater as well as to divert stormwater runoff. Constructed wetlands may also play a role in water-sensitive urban design.
A salt marsh, saltmarsh or salting, also known as a coastal salt marsh or a tidal marsh, is a coastal ecosystem in the upper coastal intertidal zone between land and open saltwater or brackish water that is regularly flooded by the tides. It is dominated by dense stands of salt-tolerant plants such as herbs, grasses, or low shrubs. These plants are terrestrial in origin and are essential to the stability of the salt marsh in trapping and binding sediments. Salt marshes play a large role in the aquatic food web and the delivery of nutrients to coastal waters. They also support terrestrial animals and provide coastal protection.
Zmudowski State Beach is located on Monterey Bay, in Moss Landing, Monterey County, northern California.
A tidal creek or tidal channel is a narrow inlet or estuary that is affected by the ebb and flow of ocean tides. Thus, it has variable salinity and electrical conductivity over the tidal cycle, and flushes salts from inland soils. Tidal creeks are characterized by slow water velocity, resulting in buildup of fine, organic sediment in wetlands. Creeks may often be a dry to muddy channel with little or no flow at low tide, but with significant depth of water at high tide. Due to the temporal variability of water quality parameters within the tidally influenced zone, there are unique biota associated with tidal creeks which are often specialised to such zones. Nutrients and organic matter are delivered downstream to habitats normally lacking these, while the creeks also provide access to inland habitat for salt-water organisms.
A tidal marsh is a marsh found along rivers, coasts and estuaries which floods and drains by the tidal movement of the adjacent estuary, sea or ocean. Tidal marshes experience many overlapping persistent cycles, including diurnal and semi-diurnal tides, day-night temperature fluctuations, spring-neap tides, seasonal vegetation growth and decay, upland runoff, decadal climate variations, and centennial to millennial trends in sea level and climate.
The Edwin B. Forsythe National Wildlife Refuge is a U.S. National Wildlife Refuge located in southern and south-central New Jersey, along the Atlantic coast, north of Atlantic City, in Atlantic and Ocean counties. The refuge was created in 1984 out of two existing refuge parcels created to protect tidal wetland and shallow bay habitat for migratory water birds. The Barnegat Division is located in Ocean County on the inland side of Barnegat Bay. The Brigantine Division is located approximately 10 miles (16 km) north of Atlantic City along the south bank of the mouth of the Mullica River. The two divisions are separated by approximately 20 miles (32 km). The refuge is located along most active flight paths of the Atlantic Flyway, making it an important link in the network of national wildlife refuges administered nationwide by the U.S. Fish and Wildlife Service. Forsythe Refuge is a part of the Hudson River/New York Bight Ecosystem and The New Jersey Coastal Heritage Trail Route. The refuge is named for Edwin B. Forsythe, conservationist Congressman from New Jersey. The refuge was named as a Ramsar Site of international importance in 1986.
An aquatic ecosystem is an ecosystem found in and around a body of water, in contrast to land-based terrestrial ecosystems. Aquatic ecosystems contain communities of organisms—aquatic life—that are dependent on each other and on their environment. The two main types of aquatic ecosystems are marine ecosystems and freshwater ecosystems. Freshwater ecosystems may be lentic ; lotic ; and wetlands.
The Goleta Slough is an area of estuary, tidal creeks, tidal marsh, and wetlands near Goleta, California, United States. It primarily consists of the filled and unfilled remnants of the historic inner Goleta Bay about 8 miles (13 km) west of Santa Barbara. The slough empties into the Pacific Ocean through an intermittently closed mouth at Goleta Beach County Park just east of the UCSB campus and Isla Vista. The slough drains the Goleta Valley and watershed, and receives the water of all of the major creeks in the Goleta area including the southern face of the Santa Ynez Mountains.
Lake Apopka is the fourth largest lake in the U.S. state of Florida. It is located 15 miles (24 km) northwest of Orlando, mostly within the bounds of Orange County, although the western part is in Lake County. Fed by a natural spring, rainfall and stormwater runoff, water from Lake Apopka flows through the Apopka-Beauclair Canal and into Lakes Beauclair and Dora. From Lake Dora, water flows into Lake Eustis, then into Lake Griffin and then northward into the Ocklawaha River, which flows into the St. Johns River. Multiple parks or nature trails are present around the lake including Magnolia Park, Lake Apopka Wildlife Drive, Ferndale Preserve, Oakland Nature Preserve, Dr. Bradford Memorial Park, and Newton Park, named for A. B. Newton.
The Seal Beach National Wildlife Refuge is a wildlife refuge encompassing 965 acres (3.91 km2) located in the California coastal community of Seal Beach. Although it is located in Orange County it is included as part of the San Diego National Wildlife Refuge Complex. It was established in 1972.
The Rachel Carson National Wildlife Refuge is a 9,125-acre (37 km2) National Wildlife Refuge made up of several parcels of land along 50 miles (80 km) of Maine's southern coast. Created in 1966, it is named for environmentalist and author Rachel Carson, whose book Silent Spring raised public awareness of the effects of DDT on migratory songbirds, and of other environmental issues.
The John H. Chafee National Wildlife Refuge is a national wildlife refuge of the United States, located along the Narrow River on the southern coast of Rhode Island.
Low marsh is a tidal marsh zone located below the Mean Highwater Mark (MHM). Based on elevation, frequency of submersion, soil characteristics, vegetation, microbial community, and other metrics, salt marshes can be divided to into three distinct areas: low marsh, middle marsh/high marsh, and the upland zone. Low marsh is characterized as being flooded daily with each high tide, while remaining exposed during low tides.
The William T. Davis Wildlife Refuge (WTDWR) is an 814-acre (3.29 km2) wildlife refuge straddling the New Springville and Travis sections of Staten Island. The park was named in honor of Staten Island native William T. Davis, a renowned naturalist and entomologist who along with the Audubon Society started the refuge with an original acquisition of 52 acres (210,000 m2). Additional acreage was acquired in increments and the park is today 814 acres (3.29 km2). Beginning in 2010, the adjacent 223-acre (0.90 km2) North Park section of Freshkills Park has undergone preparation to serve as an expansion of the wildlife refuge.
The saltmarsh sparrow is a small New World sparrow found in salt marshes along the Atlantic coast of the United States. At one time, this bird and the Nelson's sparrow were thought to be a single species, the sharp-tailed sparrow. Because of this, the species was briefly known as the "saltmarsh sharp-tailed sparrow." Saltmarsh sparrow numbers are declining due to habitat loss largely attributed to human activity.
Salt marsh die-off is a term that has been used in the US and UK to describe the death of salt marsh cordgrass leading to subsequent degradation of habitat, specifically in the low marsh zones of salt marshes on the coasts of the Western Atlantic. Cordgrass normally anchors sediment in salt marshes; its loss leads to decreased substrate hardness, increased erosion, and collapse of creek banks into the water, ultimately resulting in decreased marsh health and productivity.
The Kendall-Frost Mission Bay Marsh Reserve is a 20-acre University of California Natural Reserve System reserve on the northern shore of Mission Bay in San Diego County, California. Administered by UC San Diego, the site is owned by the University of California and managed for teaching and research.
Wetland chemistry is largely affected by dredging, which can be done for a variety of purposes. Wetlands are areas within floodplains with both terrestrial and aquatic characteristics, including marshes, swamps, bogs, and others. It has been estimated that they occupy around 2.8x106 km2, about 2.2% of the Earth’s surface, but other estimates are even higher. It has also been estimated to have a worth of $14.9 trillion and are responsible for 75% of commercial and 90% of recreational harvest of fish and shellfish in the United States. Wetlands also hold an important role in water purification, storm protection, industry, travel, research, education, and tourism. Being heavily used and traveled through, dredging is common and leads to continuation of long-term damage of the ecosystem and land loss, and ultimately a loss in industry, homes, and protection.
The marsh organ is a collection of plastic pipes attached to a wooden framework that is placed in marshes to measure the effects of inundation time and flood frequency on the productivity of marsh vegetation. The information is used for scientific research purposes.