Abstract
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.
