• Atlantic Ocean beach at Cape Cod National Seashore

    Cape Cod

    National Seashore Massachusetts

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  • Access at seashore locations

    The stairs at Nauset Light Beach in Eastham are closed due to storm damage. Herring Cove North Lot in Provincetown sustained damage resulting in closure of multiple parking spaces. The Nauset Marsh Trail bridge was destroyed in a 2012 storm. More »

Hatches Harbor Tidal Restoration Project

Hatches Harbor

An aerial view of Hatches Harbor

NPS Image

Hatches Harbor was once home to a 400-acre undisturbed salt marsh. The wetland area southwest of the dike remains natural, undisturbed salt marsh. Its uniform appearance indicates the presence of just a few species of salt-tolerant grasses and seaweeds. Despite the lack of plant diversity, salt marsh plant communities are among the most efficient in the world in converting solar and tidal energy into food for animals, rivaling tropical rain forests in the amount of plant material (biomass) produced each year.

In contrast with the small number of plant species, the diversity of marine and estuarine animals that find food and shelter here is very high. Marine fish, shellfish, crabs and lobsters rely on salt marsh habitats at critical life stages.

Until 1930, the wetland northeast of the dike was part of this productive salt marsh. The installation of the dike caused dramatic changes in plant and animal communities. The blockage of saltwater and the addition of freshwater from rainfall and groundwater inflow allowed freshwater-adapted plants to move in and crowd out those adapted to saltwater. Invasive plants, such as the common reed (Phragmites australis) thrived. Also, the lowered water level and lack of tides made it impossible for estuarine fish to reach and feed on the wetland surface. One result was that important predators to mosquito larvae, especially killifish, could not reach mosquito breeding sites in high marsh pools.

In 1987, following extensive research, the National Park Service (NPS) initiated a program to restore the marsh. The first step was to remove a tide gate that had prevented seawater from passing through a small culvert between the two wetlands. Saltwater flow was restored, and fish gained access to the marsh. In 1999 four 7' X 3' box culverts replaced the small culvert. These culverts have been opened incrementally since then, causing tide heights and salinities to again approach those of the natural marsh area. NPS scientists monitoring the project are noticing significant changes. The invasive common reed is dying. Shellfish have re-colonized the area and estuarine fish are again foraging in tidal creeks and on the marsh surface. With each new high tide this marsh is being revitalized. We invite you to return again to witness this dynamic process.

Did You Know?

Wellfleet kettle ponds

Although the kettle ponds within Cape Cod National Seashore are within 2.5 km of the ocean and have been subjected to thousands of years of salt spray, they remain low in dissolved salts. Ponds are flushed out by inflowing and outflowing groundwater, which prevents salts from accumulating.