Early Ecological Responses to Hydrologic Restoration of a Tidal Pond and Salt Marsh Complex in Narragansett Bay, Rhode Island

Abstract

Tidal exchange was restored to the flow-restricted, 2.3-ha Potter Pond salt marsh on Prudence Island in the Narragansett Bay National Estuarine Research Reserve in April 2003. Ecological monitoring was conducted for 1 year before and 2 years after restoration to quantify ecological changes. Simultaneous monitoring was conducted in a nearby marsh that served as an experimental control. Tidal restoration increased the tide range in Potter Pond from approximately 4 cm in 2000 to 120 cm in 2003. After 2 years of restoration, the height of Spartina alterniflora remained unchanged, and the same was true of the composition of the emergent marsh vegetation community. However, by 2004, the percent cover of live Phragmites australis decreased by 69%, and the average height of Phragmites decreased by 76 cm. Seven additional bird species were observed at Potter Pond after 1 year of restoration, and the number of birds observed increased from 6 to 85 per viewing effort, mostly due to large numbers of shorebirds using the newly exposed mud flats. Nekton density decreased from 100 m−2 to 38 m−2 after 1 year, probably because of the change from subtidal to mostly intertidal conditions and increased predation by birds. Initial results from monitoring demonstrate that restoration of the Potter Pond marsh complex improved tidal exchange, negatively impacted Phragmites, and increased bird use, resulting in an overall shift to a more natural functioning salt marsh system. This study also demonstrates that restoring even very small tide-restricted marshes can result in impressive ecological improvements.