Restoration of a Spartina alterniflorasalt marsh following a fuel oil spill, New York City, NY

In the seven years since 2.5 million liters of No. 2 fuel oil spilled into the Arthur Kill, the Salt Marsh Restoration Team of New York City Parks has restored Spartina alterniflora (Salt Marsh Cordgrass) to 2.43 ha of shoreline, planting seedlings and transplants in areas of low salt marsh severely impacted by oil. Restoration was undertaken to halt surface erosion and the loss of surviving vegetation and remnant peat. Biomass, stem density, flower density, height of plants, rhizome spread, basal area and plant cover were monitored for a minimum of three years between 1993 and 1997. Unplanted Severely Impacted (USI) reference sites and Existing Vegetation (EV) in the severe impact zone were also monitored. Ninety-five percent of the surface area denuded of vegetation by oil at USI reference sites remained unvegetated seven years after the spill. Sediment Total Petroleum Hydrocarbon (TPH) content was measured before and after plantings and these results indicated a high level of persistent contamination. Residual oil was not the determining factor in the survival or loss of Spartina alterniflora seedlings and transplants at planting sites. Instead, plant spacing, shoreline morphology, wave energy generated by passing vessels, and predation by Branta canadensis (Canada Goose) were the most critical factors. Three years after planting, the above ground biomass at two of the three restoration sites was comparable to the biomass at existing and restored eastern North American salt marshes. Seedlings spaced 30 cm apart provided rapid cover at two of three sites and contributed to overall survival. Where initial survival was high, goose predation was low. Where initial survival was low, shoreline morphology and wave energy were the primary causes of mortality, with goose predation an important secondary cause. Bedforms at one planting site indicated a high energy shoreline as did sediment texture results for all sites. The fetch along the Arthur Kill is not long enough to generate such high-wave energy, but passing vessels do generate plunging and surging breakers on a regular basis. A reduction in the frequency of oil spills since 1990 has been beneficial to the salt marshes along the Arthur Kill. A reduction in other anthropogenic stresses would further enhance the planted and existing vegetation.