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.

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The People of Louisiana’s Coastal Wetlands

The Coastal Wetlands Planning, Protection and Restoration Act leads the fight against Louisiana’s disappearing coast. The native people of coastal Louisiana are greatly worried about losing their homes, sources of livelihood, and culture if the lands they live on continue to disappear. Saltwater intrusion, marshes becoming open water, and the disappearance of barrier islands and protective wetlands are a few of the challenges facing coastal communities. For centuries, marshes have served as home to numerous people: American Indian tribes, Vietnamese, Croatian Americans, and other groups. All of these coastal residents are familiar with the hardship of living in an area frequented by natural disasters. Most coastal residents have chosen to stay on their lands to defend and protect the ecosystem despite the extreme risks. Without the hard work and effort of diligent landowners and organizations like CWPPRA, coastal Louisiana would be vanishing at a much faster rate.

You can read Watermarks #48 People of the Coastal Wetlands to learn more about this topic.

Louisiana’s State Reptile – The American Alligator

The American alligator (Alligator mississippiensis), the largest reptile in North America, is also known as the state reptile of Louisiana. Ancestors of the American alligator appeared nearly 160 million years ago. Alligators are cold-blooded, and their body temperature is regulated by the environment around them. There are approximately 2 million wild alligators in the state of Louisiana. Alligators can be spotted in ponds, lakes, bayous, rivers, swamps, and even occasionally swimming pools near these coastal areas in the dry months. The highest populations of alligators within Louisiana are found in coastal marshes. Coastal marshes account for about 3 million acres of alligator habitat in Louisiana.

Alligators are predators in the wetland ecosystem. Young alligators typically feed on small animals such as crawfish, insects, small fish, and frogs. An adult alligator’s diet consists of crabs, turtles, nutria, large birds, and sometimes deer. Alligators assist in population control and support diversity in the environment.  During nest construction, alligators dig burrows with their tails in peat, a boggy type of soil, which often facilitates plant growth. The burrows become “alligator holes”, or wetland depressions, which serve as a breeding area to many species other than alligators during dry periods. Alligators are key contributors to the diversity and productivity of coastal wetlands.

American-Alligator-Photos

Sabine Refuge Marsh Creation Cycle I

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The project is intended to strategically create marsh in large,
open water areas to block wind-induced saltwater
introduction and freshwater loss. In addition, it will increase
nourishment in adjacent marshes while reducing open water
fetch (distance a wave can travel) and the erosion of marsh
fringe.

Cycle I constructed 214 acres of marsh within the shallow,
open water area within retention dikes. The perimeter of the
created marsh was planted with smooth cordgrass. Dredged
slurry obtained from the Army Corps of Engineers’ dredging
of the Calcasieu River Ship Channel was placed in the
containment area.

Upon consolidation of the dredged material, the southern
containment dike was degraded and breached to allow for
water movement and restore the area to more natural
conditions. Prior to the placement of dredged material,
trenasses (small, man-made bayous) were constructed in the
project area. These trenasses facilitate natural conditions and
allow estuarine organisms to access the created marsh. This
project is part of five cycles over a 10-year period with each
cycle requiring individual construction approval.

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The Sabine Refuge Marsh Creation Project is located in the
Sabine National Wildlife Refuge, west of LA Highway 27, in
large, open water areas north and northwest of Brown’s Lake
in Cameron Parish, Louisiana.

Priority Project List 8 funded $5.9 million to complete
construction of a permanent pipeline and one cycle of marsh
creation. Engineering analyses at the time indicated that the
construction of a temporary pipeline would be more cost
effective. Therefore, a temporary pipeline was utilized for
Cycle I. However, further analysis determined that a
permanent pipeline would be advantageous. In 2004,
additional funds for engineering and design and construction
were approved for Cycles II and III. Funds for Cycle II
include the construction of a permanent dredged material
pipeline.

Construction of the Cycle I site was completed on February
26, 2002.

This project is on Priority Project List (PPL) 8.

The Sabine Refuge Marsh Creation Cycle I’s three sponsors include:

View more data on the CS-28-1 project or other projects on CWPPRA’s website.

School’s in Session

Are you interested in learning more about coastal restoration in Louisiana? Perhaps, you are looking for a fun, easy way to educate on coastal restoration topics. Either way, the Coastal Wetlands Planning, Protection and Restoration Act has the tools for you. Visit our website to find a wetland curriculum for teachers, activity books for children, printed materials, interactive games, quizzes and more.

Click the links below to join in on the fun!

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Giant Salvinia

Giant Salvinia, or Salvinia adnata, often referred to as the green monster, poses a serious threat to wetland ecosystems. This highly invasive, aquatic plant species is native to Brazil. The floating aquatic fern has leaves covered with small hairs on the upper surface that become compressed into chains forming a dense, compiled mat-like structure. In the United States, it’s difficult to control Giant Salvinia due to the lack of legal herbicides that work efficiently to stop it from spreading. Giant Salvinia was first spotted in Chenier Plain Marshes in 2009; since then it has spread throughout.

This non-native plant species has an exceedingly rapid growth rate, and under the right conditions it can potentially take over a waterway causing catastrophic results. The mat blocks sunlight from penetrating into the water, ultimately killing phytoplankton and other aquatic plant species, as well as exhausting oxygen levels, which alters the area as a waterfowl habitat and degrades the water quality for fish. Giant Salvinia is unintentionally spread to new water bodies on boats and fishing gear. One way to prevent the expansion of Giant Salvinia is to properly clean boating equipment and vessels of any plant fragments. These plant fragments, garden, and aquarium plants should all be discarded properly in the trash and kept out of water bodies. It is important to properly control and dispose of the plant material in order to keep lakes, rivers, ponds and other freshwater wetlands functioning properly without the disturbance caused by Giant Salvinia.

Cyrtobagous salviniae, a species of weevil, is often referred to as the salvinia weevil due to being a biological pest control against the highly invasive Giant Salvinia. For more information on Giant Salvinia and CWPPRA’s efforts to control this invasive plant species visit the Coastwide Salvinia Weevil Propagation Facility (LA-284) Fact Sheet.

Lost Lake Marsh Creation and Hydrologic Restoration

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Significant marsh loss has occurred between Lake Pagie and
Bayou DeCade to the point that little structural framework
remains separating those two waterbodies. Northeast of Lost
Lake, interior marsh breakup has resulted in large, interior
ponds where wind/wave energy continues to result in marsh
loss. West of Lost Lake, interior breakup has occurred as
a result of ponding and the periodic entrapment of higher
salinity waters during storm events.

Approximately 465 acres of marsh will be created between
Lake Pagie and Bayou DeCade, north of Bayou DeCade,
and along the northwestern Lost Lake shoreline. Marsh
creation will restore/protect some key features of structural
framework (i.e., lake rim and bayou bank) within the area.
Borrow material will be taken from within Lost Lake and
pumped via a hydraulic dredge into the marsh creation sites.
Tidal creeks will be constructed within the marsh creation
cells to ensure tidal connectivity and prevent ponding within
the created marsh. In addition, 30,000 linear feet (22 acres)
of terraces will be constructed to reduce fetch in an area of
deteriorated marsh north of Bayou DeCade.
Two fixed-crest weirs along Carencro Bayou will be replaced
with variable-crest structures. At certain times of the year,
Carencro Bayou is an excellent source of fresh water and
sediments from the Atchafalaya River/Four League Bay
system. However, delivery of that water into the marshes
west of Lost Lake is limited by fixed-crest weirs which limit
water exchange. Installing structures with bays/gates will
increase freshwater and sediment delivery. In addition, two
fixed-crest weirs near Rice Bayou will be replaced with
variable-crest structures to provide flow-through conditions
in the system (i.e., water enters the system from Carencro
Bayou and exits through the structures near Rice Bayou).
A similar structure will be installed along Little Carencro
Bayou to increase freshwater and sediment delivery into the
marshes north of Lost Lake.

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The project is located in the Terrebonne Basin, Terrebonne
Parish, near the vicinity of Lost Lake.

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

The Lost Lake Marsh Creation and Hydrologic Restoration project sponsors include:

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