Classifying Wetlands Part 1

When we think of wetlands, our mind may paint a picture of a swampy area with open water, and maybe a heron or alligator. Despite common perception, not all wetlands are the same. — These watery features come in all shapes, sizes, and locations along with a unique system of processes and purpose.

Wetlands are diverse and the difference between dry and wet environment lies along a gradient. Therfore, there cannot be one perfect definition to represent what a wetland is. Scientists have developed criteria to identify wetlands and aid in assessment, inventory, and management [1].

Figure 1. An example used by scientists to start the process for wetland delineation.

Criteria Definition
Wetland hydrology the gradient or degree of flooding or soil saturation across a landscape [2].
Hydrophytic vegetation plants adapted to grow in water or in a soil that is occasionally oxygen deficient due to saturation by water [2].
Hydric soils soils that are sufficiently wet in the upper root zone  and may develop anaerobic (oxygen lacking) conditions during the length of at least 1-2 growing seasons [2].

As seen below in Figure 2 and 3; some wetlands are flooded year-round while other  water levels fluctuate. The wetland hydrology differs depending on location and the geography of the landscape.

Figure 2: A simplified example of a wetland water gradient dependent on elevation and tidal ranges.

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Figure 3.

basic_gradientYou may not live close to a coastal marsh, but many water sources eventually connect to a wetland on the coast, making the streams, lakes, and swamps in your backyard an important link to the larger watershed. That’s why it’s important to support, respect, and appreciate the water systems and land of everyday life. CWPPRA projects restore and protect these systems to support the livelihood and cultures of Louisiana and to protect the land we value so dearly.

In next week’s edition of Wetland Wednesday, we’ll look at how scientist use vegetation and soils to classify wetlands!

 

Source:
[1] Fish and Wildlife Service. Classification of Wetlands and Deepwater Habitats of the United States. Available: https://www.fws.gov/wetlands/documents/Classification-of-Wetlands-and-Deepwater-Habitats-of-the-United-States-2013.pdf [August 27, 2018].
[2] Natural Resources Conservation Service. Hydric Soils Overview. Available: https://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/use/hydric/?cid=nrcs142p2_053985 [August 27, 2018].
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Mangroves in Winter

The recent cold weather in Louisiana may have been the end of the road for some plants as temperatures dipped into the teens and stayed below freezing for full days. The hibiscus in your garden may have survived because you gave it extra insulation, but what about marsh plants? Louisiana salt marshes are home to black mangroves (Avicennia germinans), but this represents the very northernmost part of their range. Of the three mangrove species found in the continental United States [red (Rhizophora mangle), black, and white (Laguncularia racemosa)], black mangroves are the most cold-hardy, but they are still sensitive to winter weather- they generally cannot establish above 28° N and S latitude because winters are too cold (a sliver of the Birdsfoot Delta is below 29° N, so we really are at their limit).

The three mangrove species are also different in their tolerances for other environmental conditions: red mangroves establish in the intertidal zone, while black and white mangroves are found at higher elevations, and white mangroves can colonize areas with little to no soil. In Florida where all three species occur, mangrove zones can be defined from the water extending inland and up in elevation .

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Red mangroves are found in the intertidal zone, while black and white mangroves establish at higher elevations. Graphic from the Florida Museum of Natural History at the University of Florida (https://www.floridamuseum.ufl.edu/southflorida/habitats/mangroves/zonation/)

Black mangroves are an important component of Louisiana salt marshes, providing habitat to a variety of species. The complex root systems trap and collect sediment, limiting erosion and maintaining land. Juvenile invertebrates and fish find shelter among the roots, while seabird chicks, such as brown pelicans and roseate spoonbills, are protected from high water events and predators up in the branches.

CWPPRA projects that nourish barrier islands and create new marsh habitat help maintain black mangrove populations by providing new land for the plants to colonize; in turn, the mangroves help the new land persist in the face of wind and wave energy.

South Grand Chenier Marsh Creation – Baker Tract

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Marshes within the Hog Bayou Watershed mapping unit are
stressed due to limited freshwater input and seasonal salinity
spikes exacerbated by construction of the Mermentau Ship
Channel. Other contributors to land loss in the area are
subsidence, compaction, and erosion of organic soils.
Currently, the project area is characterized as large, open
water with degraded areas of wetland vegetation and low
organic production. The dredging of the Mermentau Ship
Channel increased tidal amplitude and salt water intrusion
into the watershed.

The goal of the project is to create new wetland habitat,
restore degraded marsh, and reduce wave erosion of organic
soils. The project would promote the expansion of emergent
marsh and submerged aquatic vegetation throughout the
project area. Material dredged from the Gulf of Mexico will
be used to create and nourish approximately 420 acres of
marsh. Smooth cordgrass will be planted throughout the
area. To help facilitate estuarine fisheries access, constructed
retention levees will be degraded and approximately 11,756
linear feet of tidal creeks will be constructed.

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The project is located in planning Region 4, Mermentau
Basin in Cameron Parish within the Hog Bayou Watershed
Coast 2050 Mapping Unit. The mapping unit is bordered by
Lower Mud Lake to the west, the Gulf of Mexico to the
south, Rockefeller Refuge to the east, and Louisiana
Highway 82 to the north.

This project is on Priority Project List (PPL) 23.

The South Grand Chenier Marsh Creation – Baker Tract sponsors include:

 

Wetland Marshes

Marsh is a type of wetland that is continuously flooded with water. Emergent-soft stemmed vegetation is present in marsh due to the saturated soil conditions. In Louisiana, there are four types of wetland marsh: freshwater, intermediate, brackish, and salt. Marshes are classified according to the salinity of the water. The location of Louisiana marshes in relation to the Gulf of Mexico often directly correlates to the level of salt content in the water. Salinity also changes based upon rainfall, drainage, soil texture, vegetation, depth of water table, and freshwater inflow.

The salinity range for each marsh type is as follows:

  • Freshwater – 0 ppt (parts per thousand)
  • Intermediate – 0-5 ppt
  • Brackish – 5-15 ppt
  • Salt – 15 or greater ppt

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A wide variety of animals such as nutria, turtles, and many bird species can be spotted in the freshwater and intermediate marshes of Louisiana, as well as species of special concern like Louisiana black bears and Calcasieu painted crawfish. The exchange between freshwater and salt water is frequent in the state of Louisiana due to its close proximity to the Gulf of Mexico. An estuary is characterized by this mixture of freshwater and salt forming brackish water where many wetland species spend their juvenile lives. The estuaries of coastal Louisiana support economically important fisheries and provide important wildlife habitat. Crabs, fish, and shrimp are a few of the animals found in Louisiana’s salt marsh, and birds like brown pelicans and reddish egrets often nest in the shrubby vegetation bordering salt marshes. Each of these marsh types play a significant role. It is vital to keep these marshes healthy for them to maintain their value and support the people, plants, and animals of Louisiana.

 

 

Wetland Vegetation

Wetland ecologists often refer to wetland vegetation as the foundation of coastal restoration. Native plants and vegetative plantings both provide significant benefits to wetlands. Wetland plants build and stabilize soil, create habitat, purify water, and shield infrastructure. These plants tend to accumulate the thick mud of marshes which prevents the soil from washing away. Animals that live in wetlands depend on plants or plant-eating animals for their food supply. Without wetland vegetation, the supply chain would self-destruct. By absorbing nutrients and chemicals from the water and sediment, plants reduce toxins and groundwater contamination. Wetland vegetation is key to preventing shoreline erosion and reducing storm surge which affects the coastal infrastructure.

The Coastal Wetlands Planning, Protection and Restoration Act funds a variety of wetland enhancement projects, such as vegetative planting. Vegetative planting is the process of planting by hand or aerial seeding to shore up eroding banks and jump-start plant colonization.

You can read more about CWPPRA Projects that use the vegetative planting restoration technique by clicking here.

Freshwater Wetlands

Freshwater habitats come in many forms ranging from glaciers to lakes, rivers, and wetlands. These freshwater ecosystems represent less than one percent of the planet’s surface while supporting over 100,000 species including but not limited to fish, frogs, worms, crawfish, and birds and mammals nesting and feeding in wetland vegetation. While serving as habitat for a large number of animals, freshwater wetlands are also home to a variety of plant types. Cattails are a common sight around freshwater lakes and marshes and help in maintaining a healthy ecosystem by filtering runoff as it flows into lakes and serving as a protectant against shoreline erosion. Floating plants, such as duckweed, are a favorite food for many ducks and geese that populate the area.

Freshwater wetlands may stay wet year-round or evaporate during the dry season. Freshwater habitats are some of the most endangered habitats in the world. Human development, agriculture, and pollution are leading factors that put the availability of freshwater at risk. Saltwater intrusion is another underlying factor interrupting the natural conditions of water quality. These impacts have extreme consequences for our freshwater biodiversity, economy, and our well-being. Louisiana’s freshwater wetlands along the coast and other areas are disappearing at a high rate. The Coastal Wetlands Planning, Protection, and Restoration Act implements projects in an effort to preserve freshwater ecosystems.

 

Cheniere Ronquille Barrier Island Restoration

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This area is undergoing shoreline erosion, interior wetland
loss, overwash, and breakup. The Gulf shoreline erosion rate
has doubled from 1988 to 2006. Project area marshes also
are being eroded at -11.8 ft/yr between 2003 to 2006 as well
as being converted to open water from internal breakup.

Restoration would expand the Gulf shoreline structural
integrity and associated protection by tying into two recently
constructed projects to the east and address one of the
remaining reaches of the Barataria/Plaquemines shoreline.
The design includes fill for a beach and dune plus 20-years
of advanced maintenance fill, as well as fill for marsh
creation/nourishment. The location of the type and amount
of sediment needed to construct this project already has been
identified under the East Grand Terre Project that is presently
under construction. Approximately 127 acres of beach/dune
fill would be constructed and approximately 259 acres of
marsh creation/nourishment would be constructed. Intensive
dune plantings would be conducted by seeding and installing
approved nursery stock. About half of the
marsh platform would be planted with cordgrass and
portions of the dune, swale, and marsh would be planted
with appropriate woody species. Containment dikes would
be breached no later than year three to allow tidal exchange
with the created marsh.

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The project is located in Region 2, within the Barataria Basin
portion of Plaquemines Parish.

This project is on Project Priority List (PPL) 19.

The Cheniere Ronquille Barrier Island Restoration project sponsors include:

Keep up with this project and other CWPPRA projects on the project page.