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Examining Variation in Response to No. 2 Fuel Oil Exposure Between Tall- and Short-Form Saltmarsh Cordgrass (Spartina alterniflora): Implications for Marsh Restoration After an Oil Spill

SessionSpill Impacts - Marshes

DescriptionSaltmarsh cordgrass, Spartina alterniflora, is a vital and ubiquitous component of many North American saltmarshes. Within saltmarshes, there are two genetically and phenotypically distinct forms of S. alterniflora: a tall-form (>1 m in height) that grows along the edge of tidal creeks and a short-form (<0.5 m) found further inland. Due to their locations, the two forms are exposed to different degrees of tidal inundation with tall-form plants in our research area (Charleston, SC, USA) experiencing two tidal cycles each day, while short-form plants experience immersive high tides less frequently. Marsh exposure to oil following a spill can inhibit growth and lead to eventual mortality of S. alterniflora. However, studies have yet to examine the impacts of oil on these two forms of S. alterniflora with a cyclical tidal exposure. This study used microcosm systems (12-gallon buckets with simulated tidal cycles) to examine the impact of No. 2 fuel oil on short-and tall-forms of S. alterniflora exposed to two tidal regimes. Half of the systems were dosed with No. 2 fuel oil to a 0.1 mm slick thickness, while half remained unoiled controls. Within each oiling condition, there were two different tidal simulations: 1) a daily simulation which received two high and two low tide events each day and 2) a weekly simulation with two high tides every Wednesday. Short- and tall-form plants were grown from seed to minimize environmental differences during development and placed into both tidal simulations. All treatments included four replicate microcosms resulting in 32 systems total. Measurements of plant growth, plant mortality, water quality, and water hydrocarbon concentrations were taken for up to three months following oil exposure. At the conclusion of the study, above- and below-ground S. alterniflora dry biomass was also measured. Results indicate that the fastest mortality rates among oiled treatments occurred for short-form plants exposed to weekly tides, while tall-form plants with daily tides exhibited the slowest mortality rates. This data elucidates the impact of No. 2 fuel oil spills on different areas of the marsh and may help inform future restoration efforts considering replanting short- or tall-forms in oil-contaminated environments post-spill.

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