The structure and function of wetland biological communities are closely tied to and have a heavy influence on other
wetland processes (Marani et al., 2007). Primary production
by marsh vegetation directly or indirectly influences
a variety of food webs including wetlands, estuarine, oceanic, and terrestrial-based ones. Vegetation, together with
wetland physiographic features such as tidal creeks and elevation discontinuities, provides critical habitat for a wide
variety of terrestrial and aquatic organisms. Ecological
interactions such as competition and predation are also crucial in modifying community structure. Belowground bacterial activity has important effects upon biogeochemical
cycles. Wetland chemistry and hydrology directly influence
plant and animal communities, but biological activity, for
example, the burrowing of fiddler crabs (McCraith et al.,
2003) or emergent plant metabolism (Gribsholt et al.,
2003; Gribsholt and Kristensen, 2003), can have important
consequences for wetland hydrology and chemistry.
Importance of coastal wetlands
Coastal wetlands have great ecological importance
because of their biodiversity (Gopal and Junk, 2013) and
productivity. They are often critical habitats for protected
and endangered species and for species of commercial or
recreational fishery value. Wetlands are integral components of coastal hydrological processes and function in
flood control and in retention, transport, and storage of
carbon, sediments, nutrients, and pollutants. Wetlands
often filter contaminants originating higher up in the
watershed and act as sinks for excess nutrients, thus contributing to the maintenance of estuarine and nearshore
oceanic water quality. Wetlands often provide erosion protection and sediment stabilization. Wetlands also have
high recreational and aesthetic values that make these
areas desirable for human habitation. Additionally, the
coastal zone in general is highly valuable economically,
with many important facilities such as ports and airports
and the industrial/commercial development that they
attract often situated there. As a result, more than 40 %
of the US population lives in coastal counties (NOAA,
2013), and over 44 % of the world’s population lives
within 150 km of the coast (UN, 2013).
General distribution of coastal wetlands
Below is a very general outline of coastal wetland distribution throughout the world. It only offers broad descriptions,
and individual localized sites may depart significantly from
regional norms.
Polar coastal wetlands
High-latitude coastal wetlands consist of salt and brackish
water marshes and laida (wetlands inundated by both salt
water during storms and freshwater during snowmelt).
They occur along most coasts in the Northern Hemisphere, with some of the more extensive ones occurring
along Hudson and James Bays and along the coastal
plains of Alaska and the Yukon (Martini et al., 2013).
Large wetlands also occur along the Russian coast and in
major river deltas of the region. Similar wetlands do not
occur in the Southern Hemisphere because of a dearth of
ice-free substrate (Martini et al., 2013).
North America
Farther south, between New Brunswick and Nova Scotia
in the Gulf of Maine, the Bay of Fundy wetlands occur
at the approximate subarctic-temperate transition zone.
This area has one of the largest tides in the world, with
spring tidal ranges of close to 15 m. Extensive low
marshes are populated almost exclusively by
S. alterniflora, whereas in the high marsh S. patens is most
widespread and Phragmites australis and Iva frutescens
occur along the upper edge. Within New England,
regional differences associated with climate and human
impacts exist, but in general, marshes standing on marine
peat have similar vegetative composition as above. Juncus
gerardii is common as an upland fringe, and in areas with
substantial freshwater inputs, a brackish community
consisting of Scirpus americanus, several Typha species,
Zizania aquatica, and Phragmites australis occurs
(Nixon and Oviatt, 1973; Pratolongo et al., 2013).
From New England south to northern Florida, marshes
develop behind protective barrier island complexes.
Throughout this area, S. alterniflora dominates the low
marsh, with a tall form occurring in areas with longer
flooding periods and a short form where daily tidal inundation lasts only for a short time. In the high marsh,
S. patens or Juncus roemerianus may form monospecific
stands or the two species may codominate, often forming
complex spatial patchworks. As in New England, transitional brackish areas exist which in this case are dominated by Spartina cynosuroides.
In Florida, south of 30
N latitude, mangroves gradually
replace salt marshes, but narrow bands of salt marsh can
be found throughout the state. Three mangrove species
occur in Florida: the red mangrove (Rhizophora mangle),
the black mangrove (Avicennia germinans), and the white
mangrove (Laguncularia racemosa). A variety of herbaceous halophytes often occupy the mangrove understory;
examples include S. alterniflora, Batis maritima, and
Salicornia virginica.
East of the Mississippi deltaic wetlands, along the
northern Gulf Coast of North America, grass/rush marshes
can be found usually directly in front of the open ocean
due to the low tidal energy in the region. Clearly delimited
low marsh and high marsh plant zones are often evident,
but convoluted plant community mixtures can be just as
common (Montague and Wiegert, 1990). Generally,
S. alterniflora forms relatively narrow bands along the
shoreline and is then replaced by black needle rush
(Juncus roemerianus), but both species can also form
extensive monocultures (Kurz and Wagner, 1957; Rey
et al., 2012a).
The Mississippi deltaic plain region supports extensive
wetland complexes (approximately 7,250 km
2
) in six
COASTAL WETLANDS
161
wetland processes (Marani et al., 2007). Primary production
by marsh vegetation directly or indirectly influences
a variety of food webs including wetlands, estuarine, oceanic, and terrestrial-based ones. Vegetation, together with
wetland physiographic features such as tidal creeks and elevation discontinuities, provides critical habitat for a wide
variety of terrestrial and aquatic organisms. Ecological
interactions such as competition and predation are also crucial in modifying community structure. Belowground bacterial activity has important effects upon biogeochemical
cycles. Wetland chemistry and hydrology directly influence
plant and animal communities, but biological activity, for
example, the burrowing of fiddler crabs (McCraith et al.,
2003) or emergent plant metabolism (Gribsholt et al.,
2003; Gribsholt and Kristensen, 2003), can have important
consequences for wetland hydrology and chemistry.
Importance of coastal wetlands
Coastal wetlands have great ecological importance
because of their biodiversity (Gopal and Junk, 2013) and
productivity. They are often critical habitats for protected
and endangered species and for species of commercial or
recreational fishery value. Wetlands are integral components of coastal hydrological processes and function in
flood control and in retention, transport, and storage of
carbon, sediments, nutrients, and pollutants. Wetlands
often filter contaminants originating higher up in the
watershed and act as sinks for excess nutrients, thus contributing to the maintenance of estuarine and nearshore
oceanic water quality. Wetlands often provide erosion protection and sediment stabilization. Wetlands also have
high recreational and aesthetic values that make these
areas desirable for human habitation. Additionally, the
coastal zone in general is highly valuable economically,
with many important facilities such as ports and airports
and the industrial/commercial development that they
attract often situated there. As a result, more than 40 %
of the US population lives in coastal counties (NOAA,
2013), and over 44 % of the world’s population lives
within 150 km of the coast (UN, 2013).
General distribution of coastal wetlands
Below is a very general outline of coastal wetland distribution throughout the world. It only offers broad descriptions,
and individual localized sites may depart significantly from
regional norms.
Polar coastal wetlands
High-latitude coastal wetlands consist of salt and brackish
water marshes and laida (wetlands inundated by both salt
water during storms and freshwater during snowmelt).
They occur along most coasts in the Northern Hemisphere, with some of the more extensive ones occurring
along Hudson and James Bays and along the coastal
plains of Alaska and the Yukon (Martini et al., 2013).
Large wetlands also occur along the Russian coast and in
major river deltas of the region. Similar wetlands do not
occur in the Southern Hemisphere because of a dearth of
ice-free substrate (Martini et al., 2013).
North America
Farther south, between New Brunswick and Nova Scotia
in the Gulf of Maine, the Bay of Fundy wetlands occur
at the approximate subarctic-temperate transition zone.
This area has one of the largest tides in the world, with
spring tidal ranges of close to 15 m. Extensive low
marshes are populated almost exclusively by
S. alterniflora, whereas in the high marsh S. patens is most
widespread and Phragmites australis and Iva frutescens
occur along the upper edge. Within New England,
regional differences associated with climate and human
impacts exist, but in general, marshes standing on marine
peat have similar vegetative composition as above. Juncus
gerardii is common as an upland fringe, and in areas with
substantial freshwater inputs, a brackish community
consisting of Scirpus americanus, several Typha species,
Zizania aquatica, and Phragmites australis occurs
(Nixon and Oviatt, 1973; Pratolongo et al., 2013).
From New England south to northern Florida, marshes
develop behind protective barrier island complexes.
Throughout this area, S. alterniflora dominates the low
marsh, with a tall form occurring in areas with longer
flooding periods and a short form where daily tidal inundation lasts only for a short time. In the high marsh,
S. patens or Juncus roemerianus may form monospecific
stands or the two species may codominate, often forming
complex spatial patchworks. As in New England, transitional brackish areas exist which in this case are dominated by Spartina cynosuroides.
In Florida, south of 30
N latitude, mangroves gradually
replace salt marshes, but narrow bands of salt marsh can
be found throughout the state. Three mangrove species
occur in Florida: the red mangrove (Rhizophora mangle),
the black mangrove (Avicennia germinans), and the white
mangrove (Laguncularia racemosa). A variety of herbaceous halophytes often occupy the mangrove understory;
examples include S. alterniflora, Batis maritima, and
Salicornia virginica.
East of the Mississippi deltaic wetlands, along the
northern Gulf Coast of North America, grass/rush marshes
can be found usually directly in front of the open ocean
due to the low tidal energy in the region. Clearly delimited
low marsh and high marsh plant zones are often evident,
but convoluted plant community mixtures can be just as
common (Montague and Wiegert, 1990). Generally,
S. alterniflora forms relatively narrow bands along the
shoreline and is then replaced by black needle rush
(Juncus roemerianus), but both species can also form
extensive monocultures (Kurz and Wagner, 1957; Rey
et al., 2012a).
The Mississippi deltaic plain region supports extensive
wetland complexes (approximately 7,250 km
2
) in six
COASTAL WETLANDS
161