Pyrite Formation in the Coastal Everglades: Can a Fool’s Gold Indicate Sea-Level Rise?.

The formation of pyrite in soils is controlled by both oxidation-reduction conditions, available reactive iron (Fe), and free sulfide (S^-2) mediated by microbial and landscape scale processes. Soil and surface water data collected at 17 monitoring locations in Everglades National Park (ENP) along four transects were used to evaluate the degree of pyritization and surface and porewater characteristics within ENP. This study contrasts drastically different regions along an ecosystem gradient with respect to soil characteristics and water quality, including Shark River Slough (SRS), Taylor Slough (TS), Panhandle (Ph) and Florida Bay (FB), spanning freshwater, ecotone and estuarine continuum. The objectives of this research were to characterize Fe-S interactions via pyrite formation within the Everglades ecosystem, evaluate trends in the degree of pyritization (DOP) along regional transects, and investigate DOP response due to sea-level rise within sites in ecotone regions of each transect.

The degree of pyritization observed in soils along these transects can vary from very low, as observed in TS and Ph regions (0.45 and 0.46, respectively) to very high as observed in SRS (0.73). Intrinsic characteristics such as freshwater flow volumes, soil attributes and biogeochemistry of each region result in varying levels of pyrite formation. Freshwater inputs and distance from water management features significantly influence pyrite formation by driving anaerobic/reducing biogeochemical reactions, especially in freshwater portions of each transect. Based on relative concentrations of Fe and S^-2 in conjunction with results from prior studies, pyrite formation is sulfate-limited in SRS, Fe-limited in FB, and organic matter-limited in TS and Ph.