Abstract
Coastal systems in Southwest Florida (SWFL) are increasingly vulnerable to hydrocarbon contamination from anthropogenic activities and extreme weather events. Polycyclic aromatic hydrocarbons (PAHs) and n-alkanes are hydrocarbons of particular concern because many are toxic, carcinogenic, mutagenic, persistent, and capable of bioaccumulating in marine food webs. Due to their low aqueous solubility and strong affinity for particles, these compounds readily sorb to suspended sediments and accumulate on the seafloor, making estuarine and coastal sediments important contaminant reservoirs. Hurricanes, which frequently impact SWFL, can resuspend and redistribute these sediment-bound hydrocarbons through storm surge, sediment transport, and stormwater runoff, potentially altering their bioavailability and biological exposure. However, the effects of major storms on hydrocarbon redistribution and bioaccumulation in SWFL coastal ecosystems remain poorly understood.In this thesis, I addressed this knowledge gap through two complementary studies conducted following Hurricane Ian. The first study evaluated the spatial and temporal distribution, composition, and potential sources of hydrocarbons in coastal sediments across Southwest Florida. Surface sediments were collected from 20 nearshore sites between October 2022 and October 2023 and analyzed for 27 PAHs (ΣPAH27) and 21 n-alkanes (ΣAlk21) using Gas Chromatography–Tandem Mass Spectrometry (GC–MS/MS). The concentrations of hydrocarbons in sediments ranged from 0.01 to 13.42 ng·g⁻¹ for ΣPAH27 and from 0.37 to 3012.56 ng·g⁻¹ for ΣAlk21. Hydrocarbon concentrations exhibited substantial spatial and temporal variability, with elevated concentrations occurring only at a limited number of sites. Diagnostic ratios and hydrocarbon composition indicated mixed pyrogenic, petrogenic, and biogenic sources with limited evidence of widespread petroleum contamination, suggesting that Hurricane Ian redistributed hydrocarbons unevenly across the region rather than producing a uniform contamination signal.The second study investigated bioaccumulation of hydrocarbons in Eastern oysters (Crassostrea virginica) collected from two reefs in Estero Bay before (September 2022) and after Hurricane Ian (October and November 2022). Oyster tissues were analyzed for ΣPAH27 and ΣAlk21 using GC–MS/MS to evaluate changes in biological exposure associated with hurricane disturbance. The concentration of hydrocarbons in tissue ranged from 0.01 to 38.55 ng·g⁻¹ for ΣPAH27 and from 0.62 to 7255.32 ng·g⁻¹ for ΣAlk21. Temporal differences in hydrocarbon concentrations between pre- and post-hurricane sampling demonstrated that Hurricane Ian altered hydrocarbon exposure in oysters, reflecting changes in contaminant availability following storm-driven sediment redistribution. These findings highlight Eastern oysters as effective bioindicators of hydrocarbon exposure in estuarine ecosystems following major storm events.Together, these studies provide the first post-Hurricane Ian assessment integrating hydrocarbon contamination in marine sediments with biological exposure in coastal Southwest Florida. Although hydrocarbon responses differed between sediments and oysters, both studies indicate that hurricane-driven contaminant redistribution was spatially heterogeneous and influenced contaminant availability rather than producing widespread petroleum contamination. Integrating sediment chemistry with oyster biomonitoring provides a more comprehensive understanding of hydrocarbon transport and exposure pathways following major hurricanes and improves our ability to assess contaminant dynamics in vulnerable coastal ecosystems as storm intensity and frequency are projected to increase under a changing climate.