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 .
Figure 1. An example used by scientists to start the process for wetland delineation.
the gradient or degree of flooding or soil saturation across a landscape .
plants adapted to grow in water or in a soil that is occasionally oxygen deficient due to saturation by water .
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 .
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.
You 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. CWPPRAprojects 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!
As April passes into May, many migratory birds leave the tropics of Central and South America in search of bountiful summer resources in the sub-tropical United States. Among them, the very charismatic Prothonotary Warbler flies from the northern tropics to the hospitable habitats of the United States. Prothonotary warblers live in forests near bodies of slow-moving water where they can hunt for insects and nest in cavities in trees. The cypress swamps of Louisiana are about as good as it gets for a prothonotary warbler, and they stay from April to August.  If you get out into the swamp during the summer, look for their bright yellow figures darting through low-lying foliage.
Prothonotary warblers have experienced a population decline in recent years that experts attributed to the destruction of their wintering habitat in the tropics. To improve breeding success and survivorship, the Audubon Society and other ornithological enthusiasts have encouraged people to install nest boxes that help to protect warbler nests from failing. Many natural threats exist in swamps for warblers, including a variety of snakes, birds of prey, and mammals. Since brown-headed cowbirds will use prothonotary nests to lay their eggs in when given the chance, nest boxes are suggested to have a 1¼“ hole to prevent larger birds from entering the box but still allow the warblers to enter. Boxes are not left on the ground, and are often mounted on poles. Some predators can climb, so many boxes have a skirt/collar that prevents snakes, raccoons, and cats from climbing the poles into the nests. More guidelines for a good nest box can be found at https://nestwatch.org/learn/all-about-birdhouses/features-of-a-good-birdhouse/.
 Petit, L. J. (1999). Prothonotary Warbler (Protonotaria citrea), version 2.0. In The Birds of North America (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.408
The marsh within this area has been suffering from excessive water levels within the lakes subbasin that kills vegetation, prevents growth of desirable annual plant species, and contributes to shoreline erosion. Black Bayou offers a unique location in the basin where the water in the lakes subbasin and the outer, tidal waters are separated by only a narrow highway corridor.
Project components include installing ten 10 foot by 10 foot concrete box culverts in Black Bayou at the intersection of Louisiana Highway 384. The structure discharge will be in addition to the discharges provided by Calcasieu Locks, Schooner Bayou, and Catfish Point water control structures.
The project features are located in southern Calcasieu Parish, Louisiana. The majority of the project area is located east of Calcasieu Lake and includes areas north of the Gulf Intracoastal Waterway and west of Grand Lake in Cameron Parish, Louisiana.
Wetland inhabitants must also deal with flooding stress. All parts of a plant must have oxygen, which causes problems when a plant is rooted in hypoxic soils and it is flooded. Gases diffuse about 10,000 times more slowly through water than through air, and wetland soils are often inundated and hypoxic. This poses an issue for supplying roots with enough oxygen since they don’t have any around them. Some root systems will have adventitious roots, which means they extend above the surface of the water or soil to allow gas exchange with the atmosphere. Red mangroves have prop roots, black mangroves have pneumatophores, and both supply oxygen directly to the root system rather than relying on transport all the way from the leaves to the roots.
Hypoxia can be caused by eutrophication and decomposition. Hypoxia and anoxia are dangerous to most plants and animals because most cannot live only with anaerobic (without oxygen) respiration. Bacteria can sometimes live in anoxic conditions by using different electron receptors that are more plentiful in wetland soils like sulfates. Plants can sometimes cope with hypoxia thanks to adaptations like aerenchyma development in their roots. Aerenchymous tissues are much more porous to allow gases to diffuse up to 30 times more easily through a plant! In animals, lungs can allow some fish, mammals, and aquatic gastropods (snails) to live in hypoxic waters, but many fish have gills that are not adapted to hypoxia. The Gulf of Mexico along Louisiana’s coast boasts one of the largest hypoxic zones in the world with a peak area of over 8,500 square miles in 2017, where many commercial fisheries have seen a large decline in fish catch. 
 “Gulf of Mexico ‘Dead Zone’ Is the Largest Ever Measured.” Gulf of Mexico ‘Dead Zone’ Is the Largest Ever Measured | National Oceanic and Atmospheric Administration, web.archive.org/web/20170802173757/http:/www.noaa.gov/media-release/gulf-of-mexico-dead-zone-is-largest-ever-measured.
Featured image is of Rhizophora mangle (red mangrove) from Flickr by barloventomagico
Living in any habitat comes with hurdles that make it harder for plants and animals to thrive. We call these hurdles “stress”. Coastal wetlands demonstrate several kinds of stresses to both plants and animals. Through many years of evolution, plants and animals have adapted to living with these stresses, also called being “stress tolerant”. Adaptations can be in physical structure changes or on the smaller scale (cellular). Some stresses that come with living in coastal wetlands include salinity (the amount of salt or ions in the water), inundation (flooding at least above the ground, sometimes even higher than the whole plant), and hypoxia (low dissolved oxygen in the water). 
Salt water intrusion has been increased by dredging navigation channels among other impacts. Saltwater intrusion makes fresh bodies of water more saline than they usually are. The problem with this is that the plants that live in such places are adapted to live in fresh water and generally cannot deal with increases in salinity more than 1 or 2 parts per thousand (ppt). For reference, the Gulf of Mexico’s average salinity is approximately 36ppt. Some plants, though, can live in full-strength sea water. For example, the black mangrove (Avicennia germinans) has several adaptations that let it keep its cells safe from high salinity. Like smooth cordgrass (Spartina alterniflora), black mangroves excrete salt onto their leaves to get it out of their systems. Some fish have similar adaptations in their gills that allow them to keep their internal salt concentrations at safe levels.