Conserving and Restoring Critical Habitats

Coastal erosion impacts ecosystems worldwide. For instance, the State of Louisiana loses nearly a football field worth of land every 100 minutes, which has resulted in thousands of miles of lost coastline over the last 100 years. This drastic loss of coastal land highlights the dire need for coastal restoration across the Northern Gulf Coast. An unexpected solution to this sediment loss may solve two major environmental issues at once. Millions of tons of glass waste enter America's landfills each year. Rather than routing glass to a landfill, it can be crushed to create sand and gravel for coastal restoration sediment. Our goal is to determine whether glass sand is a viable option for coastal restoration by testing the impact on a critical indicator organism in coastal dune ecosystems, the Atlantic Ghost Crab, Ocypode quadrata. Ghost crabs were live-trapped from Dauphin Island, Alabama and reared in sand environments containing full beach sand, half beach sand and half glass sand, and full glass sand for 8 weeks. In order to compare the stress responses of each treatment, the crab's initial and final stress hormone levels (Crustacean Hyperglycemic Hormone), carapace widths, weights, and claw dimensions were collected. There were no significant differences in mortality (F=2,30=0.7585, p=0.4771), carapace widths (F2,14=0.4131, p=0.67), weights (F2,14=2.8286, p=0.09362), and claw dimensions (dominant F2,14=3.5073, p=0.05824 and non-dominant F2,14=0.2404, p=0.7895). Overall, our preliminary growth and survival data indicate that ghost crabs were similarly stressed in glass sand and beach sand. Although preliminary, our results suggest that glass sand is a viable option for large-scale restoration efforts both locally and globally.

Coastal restoration efforts are increasingly challenged by the shortage of natural sand, a finite resource that has been severely depleted due to overexploitation for construction and other purposes. In response to this issue, biopolymers-biodegradable polymers derived from natural sources-present a promising alternative as binders for recycled materials. This study investigates the potential of biopolymers as an alternative binder in conjunction with recycled glass sand for use in coastal restoration. Specifically, the research examined the effects of curing conditions, initial mixing moisture content, and biopolymer concentration on the mechanical behavior of biopolymer-treated recycled glass sand (BRGS). The mechanical properties were assessed using unconfined compressive strength (UCS), consolidated and drained triaxial tests, and pocket erodometer tests (PET). The findings demonstrated that mixing moisture content, biopolymer concentration, and curing conditions significantly influence soil strength. Notably, the strength of BRGS increased with dehydration, although excessive biopolymer concentration could lead to a reduction in strength. Optimal performance was observed in samples cured at higher temperatures, with BRGS cured at 105°C for 30 days exhibiting a sixfold increase in strength compared to those cured at room temperature. Additionally, BRGS showed a slight reduction in the friction angle but a significant increase in cohesion. PET results further indicated a marked improvement in the erosion resistance of BRGS samples. These findings suggested that biopolymer-treated recycled glass sand is a viable material for coastal restoration, offering enhanced mechanical properties and erosion resistance.

The Gulf of Mexico's Dead Zone is significantly impacted by nutrient pollution from fertilizers and industrial runoff, which leads to harmful algal blooms and low oxygen levels. Freshwater runoff from agriculture and industries also contributes to heavy metal contamination, including Chromium (Cr) and Nickel (Ni), in the Gulf region. This study investigates the use of Vetiver grass for phytoremediation to address the heavy metal contamination in this critical region. In this study vetiver grass was initially grown in freshwater and then transplanted into sandy soil planters-four with Vetiver and one control without plants. Following a month of growth, 2 liters of landfill leachate, known for high concentrations of Cr and Ni were introduced. After another month, the plants were harvested and analyzed. ICP-OES analysis demonstrated significant metal accumulation in Vetiver roots, with Cr concentrations reaching 277.51 mg/kg and Ni at 157.68 mg/kg, while the shoots contained lower concentrations. Soil analysis using SEM/EDX at different stages showed a notable reduction in metal levels in soil with Vetiver. SEM analysis also revealed structural differences in Vetiver roots grown in sandy versus clayey soils, potentially influencing metal uptake efficiency. The study calculated the Translocation Factor (TF) and Bioaccumulation Factor (BCF), highlighting Vetiver's effectiveness in metal uptake and translocation. These findings suggest that Vetiver grass is effective at removing heavy metals from contaminated soil. This can help improve the health of the Gulf of Mexico's Dead Zone and support efforts to reduce pollution.

West Back Bay in Biloxi, Mississippi is an oligohaline estuary. Salt-tolerant submerged aquatic vegetation (SAV) and saltmarsh grasses are found ubiquitously throughout this estuary with Vallisneria americana and Juncus roemerianus being the dominant SAV and saltmarsh vegetation. No studies have directly evaluated the role of these vegetation species in the food web. Carbon and sulfur stable isotope analyses were used to identify primary source contributions to fishes Menidia beryllina, Fundulus grandis, and Lepomis macrochirus. Isotopic niche overlap was compared between fishes and basal carbon sources bimonthly from May 2021 through May 2022. Fishes had greater than 50% isotopic niche overlap with SAV compared to fringing saltmarsh. Overlap was less than 23% for Juncus roemerianus and negligible for other saltmarsh species. These results suggest that Vallisneria americana in Back Bay is a primary driver of these fishes' diets and should be a focus of habitat conservation efforts in oligohaline ecosystems.