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| NAS - Nonindigenous Aquatic Species |
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Common Name: Atlantic cordgrass, smooth cordgrass
Synonyms and Other Names: S. alterniflora var. glabra., S. alterniflora var. pilosa
Taxonomy: available through 
Identification: Emergent estuarine grass that tends to colonize in circular patches along muddy banks within the intertidal zone, ranging between 0.5 and 3 meters in height. Tough, white rhizomes are deep-seated in the substrate, with over 40% of rhizome biomass concentrated in the upper 5 cm and nearly 75% in the top 15 cm (Gallagher et al. 1984). Leaves are flat when fresh, smooth on both upper and lower surfaces, accuminate and 4-55 mm wide at the leaf base and up to 55 mm long. Inflorescences are inconspicuous compressed spikes, 10-40 cm long, more or less open, with branching spikes loosely overlapping, and loosely appressed or spreading (Hickman 1993, Barkworth 2004). Taller with larger and more ridged stems than the native California cordgrass, Spartina foliosa which has a dense, cylindric inflorescence with spikes closely overlapping and appressed.
Native Range:
Atlantic and Gulf Coasts of the United States, where it forms the dominant salt-marsh community in tidal waters. Also native along the east coast of South America, but not in Central America (Barkworth 2004).
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Interactive maps: Continental US, Alaska, Hawaii, Caribbean
Nonindigenous Occurrences: In California, found in multiple areas in the San Francisco Bay, mostly concentrated in the south bay area, including sites at Alameda Island, Hayward Marsh, the San Francisco Bay National Wildlife Refuge and San Bruno Slough (Callaway and Josselyn 1992, Cohen and Carlton 1995, Hoagle 2008). A small population of S. alterniflora was eradicated from Humbodlt Bay, where the invasive S. densiflora is currently the dominant salt marsh plant. Also reported from Bolinas Lagoon and small bays of the Point Reyes National Seashore (Drakes Estero and Estero de Limantour), north of San Francisco, where it has been tarped or dug out.
A small population was intentionally planted for erosion control during the 1970's in the Siuslaw River estuary, Oregon (Frenkel 1990); by the early 1990's it had grown to approximately 1 acre, was recognized as invasive and treated using a combination of digging and herbicide applications. After three years of no visible re-growth, this population was deemed eradicated 1997; however, in 2005 one small clone was found and removed manually. A small infestation was found at a wetland mitigation site in Coos Bay, Oregon near Charleston in 1995 although it was not correctly identified as S. alterniflora until 2005. Repeated manual removal has controlled this small infestation with no regrowth found in 2007 (C. Cornu, pers. comm.). Most recently (September 2008), a small single clone of S. alterniflora was found in the Columbia River estuary, near Warrenton (V. Howard, pers. comm.)
Established in Willapa Bay, Grays Harbor, the Copalis River Estuary, Padilla Bay and at Whidbey and Camano Island at the eastern end of the Strait of Juan de Fuca, Washington (Simenstad and Thom 1995). The initial infestation in Willapa Bay spread to a maximum of 8,500 net acres in 2003 approximately 100 years since its introduction; recent control efforts have notably reduced this population in the past two years (Murphy et al. 2007). Small populations were found in late 2007 along the northern Washington coastline at Waatch Creek and Sooes River mouths (Phillips et al. 2008).
Nonindigenous populations also documented in Australia, New Zealand, China, India, the United Kingdom, France and the Netherlands.
Means of Introduction: The initial date and mechanism disputed. According to Sayce (1988) originally introduced in 1894 to Willapa Bay, Washington, as discarded packing material in shipments of eastern oyster (Crassostera virginica). Cohen and Carlton (1995) argue that the earliest report of Spartina alterniflora occurred later, around 1911. They found no indication that packing was used in early oyster shipments and suggest solid ballast as the likeliest transport mechanism, occurring around 1907. Regardless of the initial means of introduction, S. alterniflora has spread by seeds and rhizomes carried on winter and spring tides (Simenstad and Thom 1995). San Francisco Bay populations were planted intentionally in the early 1970's, possibly for wetland mitigation. Subsequent transplants to other sites within the bay may have been made for shoreline stabilization or "restoration" (Cohen and Carlton 1995).
Status: Large populations still present in Willapa Bay, Washington and San Francisco Bay in California. Substantial improvements in efficacy of control programs has come with use of the herbicide Imazapyr and improved GIS maps allowing improved drying times.
Impact of Introduction: Due to its higher seed production and germination rate, Spartina alterniflora establishes new colonies faster than California cordgrass (S. foliosa), which is native from Bodega Bay, CA south to Baja Mexico. Once established, S. alterniflora out-competes the native vegetatively, growing 6 to 7 times faster (Callaway and Josselyn 1992). Observations have found other plant communities, including pickleweed (Salicornia virginica), seaside arrow-grass (Triclochin maritimum), fleshy jaumea (Jaumea carnosa) and the alga, Fucus distinchus to be vulnerable to its overgrowth (Siemenstad and Thom 1995). Unvegetated mudflats of shallow estuaries are especially susceptible to invasion. At the height of the infestation in Willapa Bay approximately 9,000 acres (20% of the total 47,000 acre intertidal habitat) were colonized by S. alterniflora, transforming open areas into islands and meadows of cordgrass; (Howard et al. 2007, Murphy et al. 2007). Large scale loss of mudflat habitat may be expected to result in major ecosystem changes that will impact important natural resources. Juvenile chum salmon (Oncorhynchus keta) and English sole (Pleuronectes vetulus) depend on mud-flat habitat as prey rich nurseries. Populations of Dungeness crab (Cancer magister) will also be affected (Simenstad and Thom 1995). Currently commercial oyster (Crassostrea gigas) production is threatened as mudflat culture beds are invaded in Willapa Bay. In 1992, Callaway and Josselyn predicted the impacts of S. alterniflora invasion in San Francisco Bay to include the displacement of native fora, changes in sedimentation, decreases in benthic invertebrate and algae populations, disturbance to the upper marsh and the loss of foraging sites for shorebirds and other animals.
Remarks:
References
Callaway, J.C. and M.N. Josselyn. 1992. The introduction and spread of smoth cordgrass (Spartina alterniflora) in South San Francisco Bay. Estuaries 15(2):218-226.
Cohen, A.N. and J.T. Carlton. 1995. Nonindigenous Aquatic Species In A United States Estuary: A Case Study Of The Biological Invasions Of The San Francisco Bay And Delta. Report for the US Fish and Wildlife Service, Washington D.C. and The National Sea Grant College Program, Connecticut Sea Grant.
Frenkel, R. E. 1990. Spartina in Oregon. Spartina Workshop, Seattle.
Gallagher, John L.; Wolf, Paul L.; Pfeiffer, William J. 1984. Rhizome and root growth rates and cycles in protein and carbohydrate concentrations in Georgia Spartina alterniflora Loisel. plants. American Journal of Botany. 71(2): 165-169.
Hickman, C. (editor) 1993. The Jepson Manual: Higher Plants of California, University of California Press, CA.
Murphy, K.C., R.R. Taylor and C.H. Phillips. 2007. Progress of the 2006 Spartina eradication program. Olympia, Washington. Washington State Department of Agriculture. <http://agr.wa.gov/PlantsInsects/Weeds/Spartina/docs/SpartinaReport2006.pdf>
Sayce, K. 1988. Introduced cordgrass, Spartina alterniflora Loisel. in saltmarshes and tidelands of Willapa Bay, Washington. Report to US Fish and Wildlife Service, Willapa National Wildlife Refuge.
Simenstad, C.A. and R.M. Thom. 1995. Spartina alterniflora (smooth cordgrass) as an invasive halophyte in Pacific Northwest estuaries. Hortus Northwest 6(1):9-40.
Other Resources:
Author: V. Howard
Revision Date: 10/31/2008 Citation for this information:
V. Howard. 2010. Spartina alterniflora. USGS Nonindigenous Aquatic Species Database, Gainesville, FL.
<http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=1125> Revision Date: 10/31/2008
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