Wave energy is a major driver for coastal processes, such as erosion, sediment transport, and hydrodynamics. For this reason, it is important for wave energy to be considered in the process of site selection, design, and implementation of conservation and restoration projects. In areas influenced by boat wakes, no-wake, or idle speed only, zones have been established to protect sensitive shorelines. These zones are primarily marked with moored buoys, which are routinely stopped at abruptly by approaching boaters or accelerated out of at the end of one of these zones. An abrupt stop or start by a vessel can produce a type of wave, known as a self-reinforcing wave, that propagates above the current mean water level. The atypically large structure of these waves can lead to negative impacts on sensitive shorelines and this has been observed, anecdotally, where areas at the edge of no-wake zones have disproportionately more erosion. To explore the relationship between proximity to no-wake zones and erosion, a field experiment was performed in summer 2020 where the waves impacting the shorelines from multiple vessel approaches were evaluated. Vessel approaches consisted of 5 replicates each of 1) cruising parallel, 2) stopping parallel, 3) stopping perpendicular, 4) stopping at a 45-degree angle, and 5) accelerating parallel to shore. Waves were measured using DIY wave gauges spread across a 160m stretch of shoreline. Results indicated that wave heights impacted the shoreline were twice as high within the first 40m of accelerating out of a stop and that there was no difference in wave heights for any of the stopping treatments or cruising treatment within the first 40m. Beyond 40m, cruising and accelerating wave heights were higher than the other treatments.

Since January 2019, the Saint Stanislaus (SSC) Marine Science program has worked with the Mission-Aransas National Estuarine Research Reserve, University of Texas at Austin, in a global citizen scientist research project. The project focuses on the pollution epidemic regarding microplastics, specifically nurdles. Nurdles are small pieces of plastic that are the raw materials for larger plastics. Nurdles are often found washed up on the shores in the Gulf of Mexico region, as well as the rest of the world. Marine organisms mistake nurdles for food resulting in the absorbtion of toxic chemicals which can biomagnify through the food chain. The purpose of this research project is to bring awareness of this environmental issue, pinpoint their locations, and to prevent their spread throughout the Gulf of Mexico. SSC focuses on the beaches of Bay St. Louis, Mississippi. Marine Science classes conduct surveys on a regular basis, spending 10 - 20 minutes searching for and picking up nurdles in the strandline. After each survey, nurdles are counted and the data is submitted monthly to the Nurdle Patrol website. This data is then utilized at the state and national level in hopes to prevent further spread of nurdle pollution and to hold those manufacturers accountable for loss of these pollutants. Daily counts of nurdles found on our beaches have ranged anywhere from 20 nurdles per class to over 1,500. At the beginning of last school year, our total was 14,791 nurdles. Today, it is over 35,000 nurdles. Although a large number, it is only a fraction of the number of nurdles being spilled around the world. A recent spill in the Mississippi River near New Orleans contained 743 million nurdles. SSC is monitoring this to further understand the rate at which nurdles spread throughout the Gulf region.

Submerged aquatic vegetation (SAV) in estuaries are known to provide many ecosystem services. However, anthropogenic stressors such as development, dredging, boat traffic, and excess nutrient loading are rapidly causing declines in SAV. The actions of waterfront property owners can directly lead to the impairment of SAV and consequently hamper many of the ecosystem services that attracted them to reside along the coast. Back Bay, Mississippi is poorly understood, but is known to have SAV beds that are dominated by Vallisneria americana. Additionally, over 60% of privately owned shorelines along the Bay are currently hardened with either a seawall, wooden, or vinyl bulkhead. To better understand the spatial extent of SAV in Back Bay and possible associations with shoreline type (e.g., hardened or natural), we collected high-resolution aerial imagery in October 2019 with a UAS around the entire perimeter of Back Bay, MS that was then processed and analyzed. Specifically, shorelines were classified as either hardened or natural and the distribution of SAV patches was mapped using the collected aerial imagery. The extent of SAV in Back Bay was found to be over 30 hectares with the majority of it clustered in the lower salinity western region of the Bay. Within that western region, identified natural and hardened shoreline segments were analyzed through ArcMap to determine the length of natural shorelines and bulkheads that included a patch of seagrass within 10 meters of the shore. Results showed that ~50% of the observed natural shorelines were associated with a seagrass patch within 10 meters while only ~23% of bulkheads had the same association. Further research is needed, but this work could suggest that the maintenance of natural shorelines supports SAV more effectively than hardened shorelines in Back Bay.

The Pascagoula River Estuary contains one of the most expansive marsh ecosystems on the Mississippi Gulf Coast. The marsh provides essential economic and ecological services by supporting fisheries, filtering impurities and sediments from estuarine waters, and reducing storm surge impacts to upland areas. To assess spatial changes in marsh extent over the past two decades, we classified land cover at 3 meters GSD using four multispectral aerial image datasets collected between 1996 and 2018, with the goals of 1) quantifying changes in marsh extent, and 2) identifying areas of retreat and expansion at the lower marsh boundary. Using these classified maps, we measured changes in the areal extent of marsh, woodland, water, and unvegetated areas, and used linear regression to quantify land cover trends over time. We also measured movement of the marsh edge along channels, lakes, and the marine boundary of the marsh by calculating transect lengths at 50-meter intervals perpendicular to baselines derived from National Hydrography Dataset features. Linear regression indicated a total rate of marsh loss of 24.4 ha/yr (r^2=0.83), and a rate of 13.0 ha/yr (r^2=0.99) when only interactions between marsh and water or unvegetated areas were considered. Mean channel width increased by 5.1 m, and the marsh edge retreated by a mean 7.0 m along areas bordering the Mississippi Sound and a mean 7.0 m along lakes and other nonlinear hydrological features within the estuary, with positive and negative changes in transect length seen in each category. As conversion from marsh to woodland land cover has also resulted in net marsh loss, maintenance of the lower marsh boundary is one key factor in slowing future losses in marsh extent. These findings may be used to target areas for restoration and to examine the conditions which have allowed expansion to occur at the marsh edge.

Deer Island provides a buffer from storm and flood damage as well as shore-line stabilization to the mainland of Biloxi, MS. A third of the land has been lost since 1850, largely driven by tropical storm and hurricane impacts as well as sea level rise. The United States Army Corps of Engineers and Mississippi Department of Marine Resources have conducted restoration with beneficial use material, and two sites have since been planted with native vegetation. The sites are anticipated to function similarly to the Juncus roemerianus (Black Needlerush) dominated salt marshes natural to the northern Gulf of Mexico and provides a test case for the success of future salt marsh loss mitigation using J. roemerianus. This study assessed the vegetative health of the constructed sites using vascular plant community diversity and biomass, as well as relating these parameters to geomorphological characteristics of the area by measuring elevation and soil condition. Sampling in Spring and Fall 2017 through 2019 demonstrated establishment of planted salt marsh and naturally-recruited sand-berm vegetation. Planted J. roemerianus, however, failed to establish and exists sparsely on the marsh platform. The two constructed sites were found to have a diverse array of vegetation, but function of the salt marsh in terms of root production and sediment organic carbon deposition remained underdeveloped when compared to the natural reference site. Additionally, sea level rise was projected at the two constructed sites under three scenarios to assess the sites’ vulnerability to rising sea levels. All sites were found to be vulnerable to sea level rise except under the lowest sea level rise scenario. Further monitoring should be conducted to observe the development of ecological functions at these constructed marshes and evaluate their success in the long term.

Increasingly, coastal wetland restoration is utilized to offset wetland loss and degradation and to recover ecosystem services, making it important to evaluate the relative effectiveness and times to functional equivalence of different restoration strategies. Two critically important services provided by coastal wetlands are carbon storage and nitrogen removal. By restoring or creating wetlands, it is possible to recover these functions and services, thereby promoting more resilient coastal watersheds. As part of a new Mississippi-Alabama Sea Grant project, we will evaluate ecosystem structure and function in habitat restoration and creation projects of different ages. Our objectives are to compare structural and functional attributes in restored coastal wetlands of different ages to reference wetlands, to estimate recovery trajectories and times to equivalency for these attributes, and to evaluate the relative effectiveness of different habitat restoration projects. We will inventory plant community structure, plant biomass, soil carbon storage, and nitrogen removal capacity via denitrification in 16 coastal wetlands, including 12 created or restored wetlands ranging in age from 4 to 33 years. Preliminary results from one reference and two 33-year-old created marshes revealed that plant biomass stocks, soil organic matter, and litter decomposition rates were greater in the reference marsh than two constructed marshes, with the natural marsh storing approximately ten times more carbon than constructed marshes. Further, denitrification was two times greater in the natural marsh than one of the two constructed marshes. Through similar analyses at all sites, we will assess the relative effectiveness of different habitat restoration projects along the Mississippi-Alabama Gulf Coast, which will be used to inform restoration practices. Thus, this project will provide important baseline information about restoration activities, while also assessing the structural and functional outcomes of projects that used different approaches for wetland restoration or creation.

The Grand Bay National Estuarine Research Reserve is working with partners from the United States Geological Survey and Mississippi State University to comprehensively monitor constructed reefs in the Grand Bay Estuary. Reef construction, scheduled to occur in fall of 2020, is funded by the Natural Resource Damage Assessment Phase IV Early Restoration Project: Restoring Living Shorelines and Reefs in Mississippi Estuaries. The portion of the project slated for Grand Bay includes construction of 6.5 acres of subtidal reefs in Point Aux Chenes Bay and 3 acres of intertidal reefs in Bangs Bayou. The objectives of this project include reductions in shoreline erosion and increases in secondary productivity. Pre-construction monitoring of wave energy, shoreline erosion, vegetation communities, and sediment accretion on the marsh platform began in 2018. Monitoring of fish communities, which includes two functional groups of fish, began with gill netting in 2019 and also utilizes Breder trap deployments (began in 2020). Additional monitoring of epifaunal communities is scheduled to occur in early fall of 2020. Data from these monitoring efforts, and subsequent post-construction monitoring will be compared with data collected after the reefs are constructed in a before-after-control-impact design (BACI). This effort will be critical in guiding future reef emplacement in the Grand Bay estuary and is expected to demonstrate the ability of constructed reefs to provide functional habitat and reduce wave energy, thereby increasing productivity and slowing marsh loss.

Salt marshes exist in shallow-gradient landscapes where microtopographic changes on the order of centimeters to decimeters can drastically alter plant species composition. Thus, salt marshes are highly vulnerable to the effects of relative sea level rise and altered sediment supply. Of increasing importance within these systems is understanding the precise elevation and topographic gradient at which ecotonal transitions occur between lower-intermediate salt marsh platforms and upland wooded ecological communities. These narrow ecotones exist where subtle environmental changes result in dramatic changes in plant species composition and dominance. Thus, they potentially may be used to quantify and predict marsh transgression. The goal of this research was to use field surveys to quantify the elevation at which marsh-upland ecotone transitions occur within Mississippi’s coastal salt marshes. Elevation and slope was measured using parallel line transects (n = 33) extending from the intermediate marsh platform through marsh-upland ecotones sampled at ~1 m intervals using high precision integrated GNSS and traditional surveying methods at 12 sites located among 5 coastal preserves on the Mississippi Gulf Coast. Ecotones occurred in narrow elevation ranges across all combined sites (mean = 0.475 m, interquartile range (IQR) = .099 m) and individual coastal preserve sites Biloxi (mean = 0.424 m, IQR = .124 m), Grand Bay (mean = 0.544 m, IQR = .098 m), Hancock (mean = 0.468 m, IQR = .075 m), Pascagoula (mean = 0.357 m, IQR = .025 m), and Wolf (mean = 0.475 m, IQR = .082 m) respectively. Initial analysis suggests local maxima along first-derivative topographic profiles and rates of change (second-derivative) may prove useful in identifying and modeling ecotones. Defining the highly precise elevation thresholds at which marsh-upland ecotones occurs will assist in predicting marsh sustainability and upland transgression under continued relative sea level rise.