title: Response of salt marshes to oiling from the Deepwater Horizon spill: Implications for plant growth, soil surface-erosion, and shoreline stability.
abstract: We investigated the initial impacts and post spill recovery of salt marshes over a 3.5-year period along northern Barataria Bay, LA, USA exposed to varying degrees of Deepwater Horizon oiling to determine the effects on shoreline-stabilizing vegetation and soil processes. In moderately oiled marshes, surface soil total petroleum hydrocarbon concentrations were ~70mgg(-1) nine months after the spill. Though initial impacts of moderate oiling were evident, Spartina alterniflora and Juncus roemerianus aboveground biomass and total live belowground biomass were equivalent to reference marshes within 24-30months post spill. In contrast, heavily oiled marsh plants did not fully recover from oiling with surface soil total petroleum hydrocarbon concentrations that exceeded 500mgg(-1) nine months after oiling. Initially, heavy oiling resulted in near complete plant mortality, and subsequent recovery of live aboveground biomass was only 50% of reference marshes 42months after the spill. Heavy oiling also changed the vegetation structure of shoreline marshes from a mixed Spartina-Juncus community to predominantly Spartina; live Spartina aboveground biomass recovered within 2-3years, however, Juncus showed no recovery. In addition, live belowground biomass (0-12cm) in heavily oiled marshes was reduced by 76% three and a half years after the spill. Detrimental effects of heavy oiling on marsh plants also corresponded with significantly lower soil shear strength, lower sedimentation rates, and higher vertical soil-surface erosion rates, thus potentially affecting shoreline salt marsh stability.
authors.affiliation: Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA 70803, USA. Electronic address: comlin@lsu.edu.
authors.forename: Qianxin
authors.initials: Q
authors.lastname: Lin
authors.affiliation: Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
authors.forename: Irving A
authors.initials: IA
authors.lastname: Mendelssohn
authors.affiliation: Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA 70803, USA; Department of Biological Sciences, Nicholls State University, Thibodaux, LA 70310, USA.
authors.forename: Sean A
authors.initials: SA
authors.lastname: Graham
authors.affiliation: Department of Environmental Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
authors.forename: Aixin
authors.initials: A
authors.lastname: Hou
authors.affiliation: Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
authors.forename: John W
authors.initials: JW
authors.lastname: Fleeger
authors.affiliation: Atkins, Jacksonville, FL 32256, USA.
authors.forename: Donald R
authors.initials: DR
authors.lastname: Deis
mesh_terms: D017753:Ecosystem; D004784:Environmental Monitoring; D052918:Environmental Restoration and Remediation; D055593:Geological Phenomena; D060851:Gulf of America; D010578:Petroleum / Q000032:analysis*; D059392:Petroleum Pollution; D006109:Poaceae; D012987:Soil; D014874:Water Pollutants, Chemical / Q000032:analysis*; D053833:Wetlands
chemical_list: D010578:Petroleum; D012987:Soil; D014874:Water Pollutants, Chemical
keywords: Deepwater Horizon oil spill; Impacts and recovery; Juncus; Marshes; Shoreline stability; Spartina