Conserving and Restoring Critical Habitats

Woody encroachment into herbaceous ecosystems represents a major threat to global biodiversity. Terrestrial wet prairies adjacent to the Gulf of Mexico coastline in the Florida panhandle are among the many ecosystems in the United States experiencing woody encroachment. These plant communities have been described for decades as an ecosystem worth our attention due to high plant species diversity and endemism. Direct loss of these species-rich ecosystems is often a result of coastal development. Degradation to remaining isolated wet prairies on protected public lands is primarily caused by fire suppression, ultimately leading to hardwood encroachment. Research related to reliable and efficient restoration strategies to return these systems to their natural herbaceous state, as well as understanding the ecological benefits of doing so, are essential for their continued existence.
In 2019, a partnership was formed between the Atlanta Botanical Garden and the University of Florida with funding from the U.S. EPA to assess novel restoration approaches such as mechanical removal of accumulated organic matter and diaspore transfer alongside conventional restoration methods. Methods were assessed through the evaluation of shifts in groundcover vegetation, groundwater dynamics, and soil physical and chemical properties. Thus far, a pre-restoration seed bank evaluation revealed the accumulated organic layer of degraded sites contains many viable seeds of dominant encroaching woody species, cold stratification of soil samples increased emergence of forb and graminoid species, and duration of seed bank emergence studies are important for determining recovery potential from the seed bank. Preliminary groundwater data collection revealed greater groundwater chloride, sodium, potassium, sulfate, and magnesium ion concentrations in woody encroached wet prairies compared to reference wet prairies. This interdisciplinary approach has led to insights regarding considerations for restoration action and potential consequences of inaction. Findings related to post-restoration groundcover vegetation and soil conditions will be presented. 

Decades of fire suppression, habitat fragmentation, and development have negatively impacted the quality and quantity of pine savanna and flatwoods habitats in the Gulf Coastal Plain. In 2018, The Grand Bay Land Acquisition and Habitat Management project was implemented. This project includes a combination of acquisition and habitat management within the Grand Bay National Wildlife Refuge, Grand Bay National Estuarine Research Reserve, and Grand Bay Savanna Coastal Preserve boundaries in Jackson County, Mississippi and was designed to implement well-established habitat management techniques to restore the structure and function of target habitats within the project boundary. Long-term vegetation monitoring plots were established in 2019 along a gradient of site conditions including areas with a well-established fire regime to those that have been fire suppressed for decades. Collected data are being used to inform land management activities and observe changes in plant communities over time as restoration efforts occur. Vegetation communities are surveyed each spring and fall to capture data on the flora of each season. Preliminary analyses have shown that vegetation communities are changing in response to chemical, mechanical, and fire treatments. Analyses have also shown which species are associated with fire-maintained versus fire suppressed pine flatwoods and savannas. Long-term monitoring, especially in pre- and post-treatment studies, is an important tool in conservation and the information generated from this study can be used to inform similar coastal savanna restoration efforts in the region.

Plant morphological features such as shoot density, thickness, and height are often static features in coastal models examining marsh habitat responses to varying hydrodynamic forces (e.g., SLAMM). However, a growing body of literature demonstrates that these features vary in different wave environments. In one such study in Mobile Bay, researchers found that the thickness of shoots for two coastal marsh grasses (Spartina alterniflora and Juncus romerianus) declined with increasing exposure to larger waves – even as the density, height, and biomass of those shoots was similar to the thicker shoots observed within calmer waters. It was hypothesized that this relationship could be a function of two converging processes: wave action effects on soil oxygenation and the development of arenchyma in plant tissues. Specifically, wave turbulence increases air entrainment which could impact the availability of oxygen in the water column and, subsequently within marsh soils. Likewise, arenchyma development in plants situated within oxygen rich environments could be limited as a result since these tissues are often related to soil oxygen availability. Still, this potential mechanism remains untested. To begin to understand the processes underlying this potential mechanism, University of South Alabama researchers will explore the relationship between wave exposure and dissolved oxygen in the water column at six sites within Mobile Bay and Mississippi Sound. This pilot study will leverage and augment existing wave, water level, and dissolved oxygen loggers deployed as part of a larger field campaign in this area. Relationships between collected wave and dissolved oxygen data will be explored using regression techniques. Results from this study could improve our understanding of coastal processes that influence plant-driven wave attenuation and other ecosystem services provided by marsh habitats.

Anthropogenic impacts alter the hydrology and water quality throughout the Mobile Tensaw Delta (MTD), which results in changes to submerged aquatic vegetation (SAV) habitat. Vallisneria americana is a native SAV species that acts as a critical nursery habitat for juvenile faunal species and protects shoreline properties from erosion by stabilizing the sediment and decreasing wave energy. V. americana exhibits high phenotypic plasticity which changes its morphology, thus impacting its function and value as a habitat. This study investigates the phenotypic plasticity of V. americana spatially across the MTD. To do so, biomass cores were collected at 18 sites. Each site was chosen to capture different hydrological and environmental conditions across the MTD that may influence the morphology of V. americana. Abiotic factors, such as depth, light availability, temperature, dissolved oxygen, and salinity were also measured at each site. Core samples of V. americana were processed for morphometrics, such as height, number of leaves, blade thickness, rhizome thickness, shoot density, above and belowground biomass. This preliminary data will be used to determine variability in V. americana morphometrics across the MTD and provide a better understanding of the relationship between abiotic and hydrological differences and expressed morphometrics. This research explores phenotypic variability in V. americana to various abiotic and hydrologic conditions, with implications for the conservation of this critical habitat. Understanding which morphological traits are being expressed under certain conditions will provide useful indicators of historical environmental conditions and may influence habitat value, coastal infrastructure, and habitat stability. Thus, these findings have direct, practical applications for SAV conservation and restoration.

Marine debris discarded in or transported onto marshes can negatively impact vegetation and shoreline stability. Such loss of habitat is of concern to coastal areas in the northern Gulf of Mexico due to ongoing habitat degradation and erosion as well as receding shorelines resulting from sea-level rise. This study aims to quantify the loss of vegetation due to the presence of debris for variable intervals of time as well as the recovery rates of vegetation with and without restoration efforts after removal of debris. Two common types of debris items (wire crab pots and dense plastic squares intended to mimic opaque debris) were placed on 48 plots of 0.4 m2 black needlerush (Juncus roemerianus) vegetation in the Grand Bay National Estuarine Research Reserve at shoreline and high marsh locations. Monitoring of vegetation density, leaf height, canopy coverage, elevation, and sediment grain size were conducted to assess changes in marsh dynamics. Following removal, half of the plots were re-planted while the rest were left to recover without intervention. Results indicate different impacts relative to debris location, duration of exposure, and debris type, with shoreline plots showing the greatest impacts. Data from this project will provide useful spatial and temporal information for making critical decisions when prioritizing wetland cleanup sites and restoration efforts from ongoing litter accumulation and sudden debris spreading disturbances such as hurricanes.

The Chandeleur Islands, LA, support a diverse seagrass ecosystem and are the site for an upcoming large-scale restoration effort to mitigate island erosion and land loss. Investigating the connection between hydrologic flow and seagrass distribution and condition, is essential to understand ecosystem function and inform effective restoration and long-term monitoring. Nearshore current velocity and direction data were collected with Lowell Instruments Tilt Current Meters deployed at 12 locations across the back barrier of the Islands during September and October 2024, during the season of peak seagrass biomass. Tilt meters were spatially distributed within and outside monospecific beds of three dominant seagrass species: Halodule wrightii, Ruppia maritima, and Thalassia testudinum. Water velocity was variable across space and time, providing insight to the complex interactions between seagrass and hydrodynamic conditions. These data will contribute to establishing baseline environmental conditions in seagrass beds at the Chandeleur Islands and will be used to better understand seagrass resilience capacity and potential response to a suite of restoration scenarios.

The Chandeleur Islands are a remote chain of barrier islands located 20 miles south of Biloxi, MS. This island chain is part of Breton National Wildlife Refuge and is the only refuge that our conservation president, Theodore Roosevelt, ever visited. Unfortunately, 90% of the acreage of these islands has disappeared since Roosevelt's visit. With the decline of the islands, the marine seagrass meadows have likewise diminished. These islands are important habitats for colonial nesting water birds, sea turtles, marine mammals, and fisheries. They also serve as the first line of defense against storm surges from hurricanes for many communities in southeast Louisiana, including New Orleans.
Engineering and design are underway for the restoration of these islands. The project will target restoring nesting habitats for sea turtles, and birds and focus on preserving and enhancing the most diverse assemblage of seagrasses in the northern Gulf of Mexico. The project design incorporates the long-term effects of sea level rise, subsidence, and future hurricane scenarios. Features will be built that utilize natural processes to maintain the island chain for decades into the future. Once restored, the island and its seagrass meadows will continue to support an assemblage of wildlife and fisheries that is unique to the Gulf of Mexico. These resources travel throughout the Gulf of Mexico and to countries beyond the United States throughout their lifecycles.
Restoration of the Chandeleur Islands is a unique and rare opportunity to use nature based solutions to conduct entire ecosystem restoration.