Responding to Oil Spills in Louisiana's Coastal Floating Marshes: Ecology, Oil Impact, and Response Alternatives

Freshwater marshes cover 4000 square kilometers of the Louisiana coastal zone and are the most abundant marsh habitat type. Many of these marshes actually float as organic mats on underlying water. Some estimates suggest as much as 70% of Louisiana's coastal freshwater marsh are of the floating variety. The slow flow of water characteristic of these environments generally transports very little sediment. As a result, the marsh substrate is composed of primarily live and dead organic matter (peat formation) rather than mineral sediments. Since floating marshes are structurally different than intertidal marsh habitats, many traditional oil spill response options are ineffective or inappropriate. Access to the marsh is often limited since there is no open water ingress and the marsh structure cannot support the weight of equipment. Oil spill response options are further complicated when the source of the oil is a pipeline leak located below the floating marsh mat; spilled oil is free to travel at the interface of the underlying water and mat. Protection booming is impossible. Oil impacts often result in the death of all the living plants that are integral to the formation and sustainability of the habitat. This paper reports on two oil spills in a floating marsh near Paradis, Louisiana that occurred eight years apart. Both spills were spatially close to each other, which provided an excellent comparison for assessing potential long-term impact from oil spills in floating marshes. During both oil spill responses, unique response techniques were developed to recover spilled oil and enhance marsh recovery. An effective technique was to rake away and remove the dead oil-contaminated surface plant debris from the site and employ sorbent recovery. Lessons learned from these responses were used to develop mitigation guidance for future responses.