- Salt Marsh - Anadromous
A number of geomorphic, hydrologic, and biotic factors should be
considered during the design phase of a salt marsh restoration project.
Consideration of nearby seed sources (wind or waterborne) and adequate
excavation depths (to eliminate regrowth from buried rhizomes and
runners) are critical factors to consider in the elimination of
invasive plant species. Care must be taken to ensure that replacement
soils do not contain seed banks or rhizome material. Revegetation
with desired intertidal vegetation (e.g., Spartina alterniflora)
should follow established techniques for propagation and planting,
such as those developed by the U.S. Army Corps of Engineer's (USACE) Dredged Material Research
Program (DMRP; Broome et al. 1974; Woodhouse et al. 1974; Seneca
et al. 1975, 1976; Barko et al. 1977; Garbisch 1977; Garbisch et
al. 1975). Local or regional sources of donor plantings or seedlings
are preferable for use in revegetation efforts and are available
from commercial nurseries in the northeast (Broome et al 1974, Seneca
et al. 1985).
Tidal channel morphology and the natural dendritic patterns of
creeks and channels are important considerations in designing a
salt marsh. Tidal creeks and ponds provide "edge" habitat,
which is important in maintaining adequate drainage, facilitating
nutrient exchange between groundwater and surface waters. Tidal
creeks are the pathways for predatory fish to gain access
to abundant forage resources within the marsh. Depositional edges
of tidal creeks provide access points for smaller finfish and crustaceans,
which move on and off the flooded marsh surface to forage and
avoid predators (Minello et al. 1994). Channel size and sinuosity
can be matched to that observed in reference wetlands. A GIS application can
be a powerful tool in identifying appropriate reference areas, and
in determining the appropriate amount of edge to be incorporated
into a restoration project design. The Salt
Marsh Site Selection Tool in development for Rhode Island can be used
to identify reference areas.
Potential Obstacles to Restoration
| Equipment Sources and Contacts
Potential Obstacles to Restoration
Phragmites is notoriously persistent and resistant
to many eradication techniques. Tidal flushing, mowing, prescribed
burning, and application of chemical herbicides have all been attempted
at various locations in the northeast, often with less than desirable
results. Manual cutting, although labor intensive, has been effective
in removing Phragmites in conjunction with herbicide application.
The herbicide Rodeo, in combination with an organic surfactant has
been used successfully to eradicate Phragmites in southern
New Jersey. In many cases, burning invigorates existing stands by
removing standing dead biomass. Burning in conjunction with herbicide
applications appears to be more successful than prescribed burns
alone in controlling Phragmites.
Often the most successful attempts involve multiple control strategies,
such as repeated harvesting, with burning to remove accumulated
litter. Chemical control typically requires multiple applications
over several growing seasons and careful monitoring in order to
identify and control reinvasion.
|Typha, a freshwater invasive species.
Courtesy: U.S. Army Corps of Engineers
Sometimes, the duration of tidal flooding necessary for Phragmites
control can also result in elimination of desirable salt marsh vegetation.
For example, in a restored marsh in Stonington, CT, Phragmites
coverage increased following reintroduction of tidal flooding
(Sinicrope et al. 1990). This was attributed to the elimination
of a freshwater invasive species, Typha, which reduced
competition, allowing Phragmites to expand aggressively.
Ideally, reestablishment of tidal hydrodynamics should be gradual
and controlled, in order to avoid subsidence and permanent flooding.
Many intertidal wetlands in the northeast contain contaminated
sediments. Toxic constituents of note include heavy metals, Polychlorinated
Biphenyls (PCB), Polycyclic Aromatic Hydrocarbons (PAH),
and dioxin. Excavation and removal or disposal of these sediments in
an environmentally acceptable and economically feasible manner requires
careful planning and coordination. Disposal of contaminated sediments
can be very expensive, and suitable land or water-based repositories
are scarce in the Northeast. Large-scale sediment decontamination
technologies are currently unavailable or so expensive as to be
cost-prohibitive. Clean substrates are needed to cap contaminated
areas. Sources of clean soil with suitable grain size and organic
matter content need to be identified, and an economically feasible
means of obtaining such material would need to be determined prior
to project implementation.
Some animals are known to be highly destructive in their grazing
to recently established salt marsh plants. Snow geese, which graze
on the soft shoots and rhizomes of smooth cordgrass (Spartina
alterniflora), can decimate large areas of newly established
marsh within days. On a much smaller spatial scale, muskrat burrowing
and feeding activity can also damage newly restored salt marshes.
Fences, and grids of narrow stakes, which prevent birds from landing
in the vicinity of a newly planted or restored area, are often used
to prevent snow geese and other animals from disturbing a newly
Restoration practitioners must be sure that a project does not
conflict with existing land uses such as industrial or commercial facilities
in the area, parks and recreational facilities, or existing residential
developments. Ideally, these issues are to be resolved in the reconnaissance
and planning phase, long before project construction takes place.
Hydrologic restoration projects are particularly subject to landowner
concerns about increased flooding of adjacent coastal properties
Equipment Sources and Contacts
There are a variety of sources and professional contacts to assist
restoration practitioners in gathering information and forming partnerships.
Salt marsh plantings can be obtained from local and regional nurseries
that specialize in products for wetland restoration and creation projects.
Several comprehensive literature reviews
and guidebooks are available from various agencies and other
organizations involved in salt marsh restoration.
Local experts can be accessed at federal and state environmental
resource agencies, non-profit organizations, and at academic research
institutions. Many of these include the National Marine Fisheries
Service Restoration Center, Narragansett Bay National Estuarine
Research Reserve, DEM Narragansett Bay Estuary Program, Coastal
Resources Management Council, Save The Bay, and the University of
Rhode Island. Contacts for these
groups and others are available from this Web site.
Many companies specialize
in the manufacture and sale of environmental monitoring equipment
used in conducting restoration and data collection in salt marshes.
Supplies and equipment includes marsh plants, seine nets, tide gauges,
sediment sampling tools, and water quality monitoring supplies.
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Barko, J.W., R.M. Smart, C.R. Lee, M.C. Landin, T.C. Sturgis, and
R.N. Gordon. 1977. Establishment and growth of selected freshwater
and coastal marsh plants in relation to characteristics of dredged
sediments. Technical Report D-77-2, U.S. Army Engineer Waterways
Experiment Station, Vicksburg, Mississippi.
Broome, S.W., E.D. Seneca, and W.W. Woodhouse, Jr. 1988. Tidal
salt marsh restoration. Aquatic Botany 32:1-22.
Garbisch, E.W., Jr. 1977. Recent and planned marsh establishment
work throughout the contiguous United States: A survey and basic
guidelines. Contract Report D-77-3, U.S. Army Engineer Waterways
Experiment Station, Vicksburg, Mississippi.
Garbisch, E.W., Jr., P.B. Woller, and R.J. McCallum. 1975. Salt
marsh establishment and development. Technical Memorandum 52, U.S.
Army Corps of Engineers, Coastal Engineering Research Center, Fort
Minello, T.J., R.J. Zimmerman and R. Medina. 1994. The importance
of edge for natant macrofauna in a created salt marsh. Wetlands
Seneca, E.D., W.W. Woodhouse, Jr., and S.W. Broome. 1975. Salt-water
marsh creation. pp. 427-437 in: L.E. Cronin, (Ed.), Estuarine
Research Volume II: Geology and Engineering, Academic Press,
New York, New York.
Seneca, E.D., S.W. Broome, W.W. Woodhouse, Jr., L.M. Cammen, and
J.T. Lyon, III. 1976. Establishing Spartina alterniflora
marsh in North Carolina. Environmental Conservation 3:185-188.
Steinke, T.J. 1988. Restoration of degraded salt marshes in Pine
Creek, Fairfield, Connecticut, pp. 19-33. In: M.W. Lefor and W.C.
Kennard, (eds.), Proceedings of the Fourth Wetlands Conference:
Wetlands Creation and Restoration, November 15, 1986, Report No. 34, Connecticut Institute
of Water Resources, University of Connecticut, Storrs, Connecticut.
Woodhouse, W.W., Jr., E.D. Seneca, and S.W. Broome. 1974. Propagation
of Spartina alterniflora for substrate stabilization and
salt marsh development. Technical Memorandum 46, U.S. Army Corps
of Engineers, Coastal Engineering Research Center, Fort Belvoir,
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