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Comparison of Replanting Tactics after a Simulated Marine Diesel Fuel Spill in Estuarine Mesocosms
DescriptionCoastal marshlands are ecologically critical areas that provide essential food, refuge, and nursery habitat. They are highly sensitive to oil spills and exceedingly difficult to clean up. Many of the techniques used to clean oiled shorelines can cause additional damage in marshlands and are not viable treatment options in these sensitive environments. During the Deepwater Horizon oil spill, NOAA investigated a wide variety of clean-up tactics in the most heavily impacted coastal marshes of Louisiana, USA. Subsequent monitoring revealed that one of the most beneficial tactics employed was to replant native grasses in the impacted areas. The objective of this study is to determine what combination of marsh grass (Spartina alterniflora, smooth cordgrass) replanting tactics produces the best outcome for a diesel fuel oiled-marsh in a controlled setting. The study consisted of 20 oiled mesocosms (approximately 450 L tanks with simulated tidal flux) with four treatments (control mesocosms with no replanting, oiled mesocosms with no replanting, oiled mesocosms replanted with field transplants, and oiled mesocosms replanted with nursery-raised plants). Each treatment had 5 replicate mesocosms. Replanting tactics tested also include containerized/plug plantings vs. bare-root plantings. The dead/oiled vegetation was cut and removed from the mesocosms that later received replanted S. alterniflora. Marsh replanting success was followed over an extended period (9 months). Data presented include oil effects on the original marsh prior to replanting, hydrocarbon residues in water and sediments over time, and measurements of the growth of the replanted grasses (stem density, shoot height, above-ground biomass, and below-ground biomass). An initial replanting effort was attempted 2 months after the oiling event. All of the replanted S. alterniflora from that event died because hydrocarbon levels were still too high in sediments. A second replanting effort occurred 8 months after the oiling event and was more successful. Preliminary results indicate that field transplants had greater increases in shoot height than nursery raised replants. Conversely, nursery raised plants had greater increases in stem densities after 9 months than the field transplants. Containerized/plug plantings out performed bare-root plantings. Comparisons of above-ground and below-ground biomass for each of the different replanting tactics will be presented. This data will help inform future response and restoration efforts that are considering using replanting as a tactic in an oil-contaminated salt-marsh.
Event Type
Paper
TimeThursday, May 16th12:30pm - 12:50pm CDT
Location291-292
Tags
Restoration