Planting after shoreline cleanup treatment improves salt marsh vegetation recovery following the Deepwater Horizon oil spill

The Deepwater Horizon oil spill (2010) resulted in similar to 100 km of heavily oiled salt marsh shorelines with severe marsh vegetation impacts. Approximately 27 km of these shorelines had marsh cleanup treatments aimed at limiting oil spread and facilitating ecological recovery. Heavy oiling impacts and disturbance from intensive cleanup treatments left marsh shorelines largely bare of live vegetation. Following operational-scale shoreline cleanup and experimental planting of Spartina alterniflora, we compared oiling degree and vegetation recovery among three types of heavily oiled salt marsh plots over three years: oiled control (no cleanup treatment, no planting); mechanical cleanup treatment (unplanted); and mechanical treatment coupled with planting. Nearby reference plots were used to define recovery targets and determine recovery progress. Mechanical treatment with planting showed the most improvement in oiling conditions and was most effective in re-establishing vegetation cover and dominant plant species composition approaching reference conditions. In contrast, the oiled controls and mechanical treatment plots without planting were similar and showed much slower recovery trends. Vegetation planting should be considered as a shoreline treatment or restoration approach for heavily oiled salt marshes, especially where oil impacted areas are left largely unvegetated, natural recovery is delayed, marsh shorelines are at risk of erosion, and as a possible condition for the use of intensive cleanup treatments. Vegetation planting following oil spills could be incorporated into shoreline treatment operations during emergency response as shoreline stabilization and for oil removal via phytoremediation, or as emergency restoration under the Natural Resources Damage Assessment (NRDA) process, to limit the degree and duration of natural resource impacts.

Automated summary

The study found that mechanical treatment coupled with vegetation planting in heavily oiled salt marshes showed the most improvement in oiling conditions and vegetation recovery compared to untreated areas or those with mechanical treatment only. This approach was most effective in re-establishing vegetation cover and dominant plant species composition approaching reference conditions.