Gulf Savers? Bag: A Sustainable Approach for Spartina alterniflora Marsh Restoration and Sediment Management

摘要

The use of the Gulf Savers? bag (bag) for Spartina alterniflora marsh restoration atPopcorn Beach at the Pass a Loutre WMA, Venice, Louisiana, demonstrates the effectivenessof this approach for marsh restoration. The bag is a sustainable, biodegradable,self-contained package of native plants with its own site-specific custom mixed supply ofnatural nutrients to support, feed, and protect the native vegetation. Each bag containedthree, one-year-old Spartina seedling plugs and are the size of a sandbag (45 cm). Thebag is a stability kit that jump-starts growth and survivability in the face of storm surge,wave action, and rapid erosion. Vegetative restoration of the Gulf Coast marshes is ofparamount importance to establish a living, growing barrier in the face of land loss andrising sea levels. In addition, Gulf Coast wetlands provide economic stimulus for coastalcommunities and the nation as a whole, from commercial fisheries to recreational activities,in the form of critical habitat for fish and wildlife.As one of the three principal outlets of the Mississippi River, the Pass a Loutre Site ischallenging to restore using traditional planting techniques due to the variable tidal range,high wave energy and substantial discharge rates on-site creating an obstacle to Spartinaplug establishment. In December 2010, 400 bags (1200 plugs) were placed on the northend of Popcorn Beach as a demonstration project. Half of the bags (200 bags) were distributedin cluster formation (2-3 bags) in a checkerboard pattern, in an approximately22 m by 25 m area adjacent to the beach, with 3 m between bag clusters. The remaininghalf (200 bags), were deployed as a continuous row along portions of the perimeter inorder to enhance sediment capture and to buffer interior bag groupings from high energytidal forces. In March of 2011, 50 additional bags of Spartina plugs in cluster formationswere deployed to reinforce the perimeter by arraying bags adjacent to the perimeter rowsdeployed in December 2010. The first monitoring event at the Site was conducted inDecember of 2011 at pre-surveyed, permanent 1 m by 1 m plots. The average percentcover of the Spartina was 78%, with an average canopy height of 93 cm in the bag area.A second monitoring was conducted at the same plot locations in April of 2012. Theaverage percent cover was 85% and the average canopy height was 119 cm in the bagarea. Of importance is the fact that the Spartina and sediment have completely filled inthe treatment area in a twelve month period. In addition, the initial linear formation ofSpartina along the perimeter had expanded outwards to a width of 8 m from the originalplanting in 17 months. The percent cover, average canopy height, and aerial extent of theSpartina, as well as the associated accumulation of sediment, demonstrate the effectivenessof the bags for use in marsh restoration in a sustainable manner.