Salinity

Freshwater salinization and expanding desertification threaten global agriculture. Promise lies in salt resistance genes found in Salicornia europaea, a halophyte that thrives in high-salt conditions partly due to protein action. We focused one of its genes, SeNN24. It enhanced salt resistance in yeast and shows promise in improving crop resilience. Our research introduced SeNN24 into tobacco via agrobacterial transformation, testing the plants under salt and drought conditions. The transformed tobacco showed superior tolerance of up to 400mM NaCl and drought, maintaining health and even flowering under stress. This suggests that SeNN24 could potentially confer significant salt and drought resistance to vital crops, protecting them from environmental challenges and enhancing agricultural sustainability.

Peatlands are areas with an accumulated layer of peat soil that are considered global stores of carbon, acting as a net sink of carbon dioxide and a net source of methane. Recent studies in coastal peatlands have shown how that a rise in sea level may contribute to the degradation of peat soils due to the inland progression of the saltwater interface, which may result in physical changes within the peat matrix that may eventually result in peat collapse. For example, earlier studies in boreal peat soils described the effect of pore dilation as a result of increased salinity in peat soils, while recent studies in Everglades peat soils showed specific salinity thresholds that may represent a permanent loss of the structural integrity of the peat matrix that may represent early stages of peat collapse. While most of these previous efforts have focused on drivers, recent work has also explored conceptual models to better understand the mechanisms inducing peat collapse. However, few datasets exists that consistently compare differences in physical properties under different in‐situ salinity conditions. In this study differences in the physical properties of peat soils across a salinity gradient along the western edge of Big Cypress National Preserve are investigated to test how differences in salinity may induce physical changes in the soil matrix. The physical properties targeted for this study include porosity, hydraulic conductivity, and carbon content. Measurements are conducted at the laboratory scale using peat cores and monoliths collected at selected locations to investigate: 1) how overall soil physical properties change spatially over a salinity gradient at the km scale moving from permanently saline to freshwater conditions; and 2) how physical properties change spatially at specific sites as dependant on vegetation boundaries and proximity to collapsed soils. This study has implications for better understanding the potential relation between physical changes of the soil matrix and the phenomena of peat collapse in the Everglades as saltwater intrusion progresses inward and alters freshwater ecosystems. Furthermore, a better mechanistic understanding of the peat collapse phenomenon can potentially help mitigate its occurrence.

Vibrio vulnificus is a marine pathogen of human health concern, capable of causing potentially fatal wound infections in a select group of the population. Previous studies have indicated this species’ strong negative correlation with salinity, not typically found above 30 ppt. This study assessed the ability of V. vulnificus to become Viable But Nonculturable in response to elevated salinity (35 ppt) as well as investigated novel methods for confirming their entrance into this state. Results showed a complete loss of culturability in both Environmental and Clinical strains of this bacterium by 9 days after inoculation. Using a High Content Imager, it was determined that these pathogens were not dying (< 10%) in response to the treatment and were partially becoming cocci (≈35%). This study indicates the importance of understanding the impact environmental parameters have on this human pathogen, and what it means for reliably detecting them.

Understanding and resolving the water quality problems that Florida Bay has
endured requires an understanding of its salinity drivers. Because salinity is the prime
factor that drives estuarine ecosystem, Florida Bay’s ecosystem health depends on the
correct salinity balance of the Bay. In this thesis, the Regional Oceanic Modeling System
- a hydrodynamic prognostic model -was implemented on Florida Bay and it was tailored
for shallow waters. Results show that the model captures most of the salinity spatial and
temporal variability of Florida Bay. Furthermore, it establishes the role of the major
drivers like evaporation, precipitation, and runoff on Florida Bay’s salinity. The model
resolves region specific salinity drivers in all four areas of Florida Bay characterized by
their own salinity regimes. The model was also able to reveal the impact of surface runoff
on salinity in the later part of the year when evaporation increases. A new technique was
developed to estimate the discharge and salinity of unmonitored small creeks north of
Florida Bay. Those data were estimated from the relationship between net freshwater flux, runoff, and salinity. Model results revealed the importance of accounting for these
small creeks to accurately simulate Florida Bay’s salinity.