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Project Goals

The goals of the salt marsh restoration project are to:

  • Decrease the height and vigor of the invasive reed
    Phragmites australis
  • Reestablish native high and low marsh community.

Introduction

Little Mussachuck Creek marsh consists of 25 acres of estuarine salt and brackish wetlands and approximately 10 acres of open water and mudflat habitats. The western edge of the marsh is bounded by Annawamscutt Beach, a relatively narrow barrier beach, separating the marsh from Narragansett Bay. The northern portion of the marsh was historically connected to Narragansett Bay by a tidal inlet which has since been closed off by longshore deposition in the early 1990s. Little Mussachuck Creek empties into Narragansett Bay at its southern end where it forms an expansive tidal delta. The pond in the northern marsh is less than 2 meters deep at its deepest point where salinity in 1998 ranged from 0 to 18 parts per thousand (‰). The pond receives tidal input only on extreme high tides (~20 tides/year) and maintains qualities more similar to a very small shallow coastal lagoon. The vegetative community of the northern portion of Little Mussachuck can be classified as estuarine brackish wetland while the southern portion of the marsh is representative of estuarine salt marsh. The brackish marsh harbors species of plants listed by the Rhode Island Natural Heritage Program as “Threatened” or “Species of Concern” in Rhode Island, such as Eleocharis rostellata, Scirpus maritima, and Scirpus robustus.


History of the Salt Marsh

The closure of the tidal inlet transformed the salt marsh in the early 1990’s from an apparently tidally influenced salt marsh into a fresh/brackish semi tidal pond which led to the colonization of the marsh by monotypic stands of the invasive plant, Phragmites australisPhragmites australis can out-compete native salt marsh vegetation in lower salinities. 


Restoration

Restoration of tidal flow to the upper marsh and pond was carried out in April 1998 by Save The Bay As part of this project, a new channel was excavated to connect the pond to the northern terminus of the existing tidal channel. The new channel was designed to maintain surface water in upper brackish pond, allow fresh surface water to drain out of the pond, and to convey tidal inputs into the marsh and the pond during spring high tides. 

On May 1, 2004 Save The Bay, the Barrington Land Conservation Trust, and a corps of volunteers increased the width of the creek dug in 1998 and cleared Phragmites out of the lower section of the creek. The salt marsh sod removed was transplanted in other areas in the marsh and Phragmites’ roots (rhizomes) were disposed of in a field disposal area. Smaller debris not removed by the Boy Scout troop was cleared out. These tasks will allow freshwater drainage from the pond and should allow tidal flow into the marsh during spring tides, increasing the average salinity of the pore water. The increased salinity may limit the expansion of Phragmites.

To additionally reduce the spread of Phragmites, the Barrington Land Conservation Trust has applied this spring to USDA Natural Resources Conservation Service for Wildlife Habitat Incentives Program (WHIP) funding. The funding would support cutting and removal of the Phragmites stands, as well as herbicide application. These tasks may need to be repeated to prevent the further spread of Phragmites. WHIP funding will also support continued monitoring by Save The Bay. Save The Bay will continue monitoring Phragmites lateral growth and soil salinity, as well as survey the percent cover of marsh plant species, and the height of Phragmites australis.

Several options exist for long term maintenance of Little Mussachuck Creek marsh. As mentioned above, cutting and spraying of Phragmites stands may have to be conducted over multiple years to combat the spread of Phragmites. More substantial alterations to the southern inlet could also be necessary.


Monitoring

To measure the expansion or contraction of Phragmites australis stands over time, stakes were installed at the outer edge of the Phragmites stands in 1998. In 1999, 2000, and 2003, the distance from each stake to the new edge of the Phragmites stands was measured, although not all of the original stakes could be located. Cumulative lateral change between 1998 and 2003 is shown. Locations where the stakes could not be found have no change. Phragmites stand expansion ranged from 0 to 10.5 meters with a mean of 1.5 meters. At most stake locations, Phragmites stands expanded into the marsh. The expansion was greatest in the salt marsh area. In the pond the Phragmites expansion was limited by the pond’s water level and along the creek the Phragmites expansion was limited by the salinity of the creek. In the salt marsh area, there was no limiting factor to the Phragmites growth and it was able to expand across the relatively dry salt marsh.

 

 
 
 
 
 
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