Investigating the effects of salinization in peat soils of the southwestern Everglades: implications for carbon fluxes and soil collapse during sea level rise

While debate still exists surrounding projections for sea level rise over the next century, there is a general scientific consensus that even the most conservative estimates will have detrimental effects on Florida's coastal wetlands. The effects on freshwater habitats in the Everglades will also be particularly destructive as saltwater penetrates previously freshwater marshes, accelerating soil decomposition, altering carbon storage and biogeochemical cycling in the soil, and inducing peat collapse. Recent research has concentrated on understanding these processes; however, uncertainties remain regarding how salinization may alter the carbon cycle in peat soils, and how peat soils respond (at the matrix level) to increases in salinity. This research investigated the effect of salinization in peat soils by using an array of hydrogeophysical measurements (both at the laboratory and field scales) within a fluid conductivity gradient (i.e. from saline to freshwater conditions) in the southwestern Everglades. Specifically, we investigated how salinization affects peat soils in relation to: 1) changes in the production, accumulation and release of biogenic gases within peat soil monoliths at the laboratory scale, and fixed platforms at three locations distributed across a landscape-scale salinization gradient; and 2) changes in their physical properties (i.e. porosity, hydraulic conductivity) leading to pore dilation, and its relevance for peat matrix deformation in peat soil monoliths at the laboratory scale. Imaging of peat collapse areas at the field scale using hydrogeophysical methods were also conducted to infer potential lithological controls and changes in peat properties that may lead to the peat collapse.