Spartina alterniflora
Encyclopedia
Spartina alterniflora (Smooth Cordgrass or Saltmarsh Cordgrass) is a perennial deciduous grass which is found in intertidal wetlands, especially estuarine salt marsh
es. It grows 1-1.5 m tall, and has smooth, hollow stems which bear leaves up to 20-60 cm long and 1.5 cm wide at their base, which are sharply tapered and bend down at their tips. Like its relative Saltmeadow Cordgrass S. patens, it produces flower
s and seed
s on only one side of the stalk. The flowers are a yellowish-green, turning brown by the winter. It has rhizoidial roots, which, when broken off, can result in vegetative asexual growth. The root
s are an important food resource for Snow Geese
.
S. alterniflora is noted for its capacity to act as an environmental engineer. It grows out into the water at the seaward edge of a salt marsh, and accumulates sediment and enables other habitat-engineering species, such as mussels, to settle. This accumulation of sediment and other substrate-building species gradually builds up the level of the land at the seaward edge, and other, higher-marsh species move onto the new land. As the marsh accretes, S. alterniflora moves still further out to form a new edge. S. alterniflora grows in tallest forms at the outermost edge of a given marsh, displaying shorter morphologies up onto the landward side of the Spartina belt.
S. alterniflora is native to the Atlantic coast of the Americas
from Newfoundland, Canada
south to northern Argentina
, where it forms a dominant part of brackish coast
al saltmarshes.
. S. anglica is a fertile polyploid derived from the hybrid S.alterniflora × townsendii (S. alterniflora × S. maritima
), first found when American S. alterniflora was introduced to southern England
in about 1870 and came into contact with the local native S. maritima. S. anglica has a variety of traits that allow it to outcompete native plants, including a high saline tolerance and the ability to perform photosynthesis
at lower temperatures more productively than other similar plants. It can grow on a wider range of sediments than other species of Spartina, and can survive inundation in salt water
for longer periods of time. S. anglica has since spread throughout northwest Europe, and (following introduction for erosion control) eastern North America.
In Willapa Bay
of Washington state, Spartina alterniflora was probably an accidental introduction during oyster transplants during the nineteenth century. Presently, it covers 6,000-10,000 ha (15 to 25 thousand acres) of land, according to a 1999 estimate. In contrast, in the 1950’s, under 160 ha (400 acres) of Spartina alterniflora were present. It is also making inroads into Puget Sound
and Grays Harbor in Washington. The grass can hinder water circulation and drainage
or block boating channels. Meadows of S. alterniflora can crowd out native species, reducing biodiversity
and altering the environment; as a result of S. alterniflora's growth, invertebrates that live in mud flats disappear as their habitat
is overgrown, and in turn, food sources shrink for birds who feed on those invertebrates.
In California
, four species of exotic Spartina (S. alterniflora, S. densiflora
, S. patens
, and S. anglica) have been introduced to the San Francisco Bay region. Spartina alterniflora is well established in San Francisco Bay, and has had the greatest impact of all the cordgrasses in San Francisco Bay (Ayres et al., 2004). It was introduced in 1973 by the Army Corps of Engineers in an attempt to reclaim marshland, and was spread and replanted around the bay in further restoration projects. It demonstrated an ability to outcompete the native S. foliosa
, and to potentially eliminate it from San Francisco Bay (Callaway and Josselyn, 1992).
Spartina alterniflora has also been found to hybridize with S. foliosa, producing offspring that may be an even greater threat than S. alterniflora by itself (Anttila et al., 2000). The hybrid can physically modify the environment to the detriment of native species (Ayres et al., 1999), and the hybrid populations have spread into creeks
, bay
s, and more remote coastal locations. The hybrids produce enormous amounts of pollen, which swamp the stigmas of the native S. foliosa flowers to produce even larger numbers of hybrid offspring, leaving the native Spartina little chance to grow as a pure strain. The hybrids also produce much larger numbers of fertile seeds than the native Spartina, and are producing a hybrid population that is not only increasing in numbers, but increasing in its rate of population growth (Ayres et al., 2004). The hybrids may also be able to fertilize themselves, which the native Spartina cannot do, and which increases the spread of the hybrid swarm even further.
Several means of control and eradication have been employed against Spartina alterniflora where it has become a pest. Hand pulling is effective, but only when done thoroughly and carefully, lest the plant's seed
s spread to infest other areas. Glyphosate, an herbicide
, is approved in Washington to kill it. In Willapa Bay, leafhopper bugs (Prokelisia marginata) have been employed to kill the plants, which threaten the oyster
industry there. Surveys, by air, land, and sea are conducted in infested and threatened areas near San Francisco to determine Spartina's spread.
The caterpillar
s of Aaron's Skipper
(Poanes aaroni) have only been found on this species to date.
Salt marsh
A salt marsh is an environment in the upper coastal intertidal zone between land and salt water or brackish water, it is dominated by dense stands of halophytic plants such as herbs, grasses, or low shrubs. These plants are terrestrial in origin and are essential to the stability of the salt marsh...
es. It grows 1-1.5 m tall, and has smooth, hollow stems which bear leaves up to 20-60 cm long and 1.5 cm wide at their base, which are sharply tapered and bend down at their tips. Like its relative Saltmeadow Cordgrass S. patens, it produces flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
s and seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...
s on only one side of the stalk. The flowers are a yellowish-green, turning brown by the winter. It has rhizoidial roots, which, when broken off, can result in vegetative asexual growth. The root
Root
In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...
s are an important food resource for Snow Geese
Snow Goose
The Snow Goose , also known as the Blue Goose, is a North American species of goose. Its name derives from the typically white plumage. The genus of this bird is disputed...
.
S. alterniflora is noted for its capacity to act as an environmental engineer. It grows out into the water at the seaward edge of a salt marsh, and accumulates sediment and enables other habitat-engineering species, such as mussels, to settle. This accumulation of sediment and other substrate-building species gradually builds up the level of the land at the seaward edge, and other, higher-marsh species move onto the new land. As the marsh accretes, S. alterniflora moves still further out to form a new edge. S. alterniflora grows in tallest forms at the outermost edge of a given marsh, displaying shorter morphologies up onto the landward side of the Spartina belt.
S. alterniflora is native to the Atlantic coast of the Americas
Americas
The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...
from Newfoundland, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
south to northern Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
, where it forms a dominant part of brackish coast
Coast
A coastline or seashore is the area where land meets the sea or ocean. A precise line that can be called a coastline cannot be determined due to the dynamic nature of tides. The term "coastal zone" can be used instead, which is a spatial zone where interaction of the sea and land processes occurs...
al saltmarshes.
Problems as an invasive species
Spartina alterniflora can become an invasive plant, either by itself or by hybridizing with native species and preventing propagation of the pure native strain. One example of an invasive Spartina alterniflora hybrid is that of S. anglicaSpartina anglica
Spartina anglica is a species of cordgrass that originated in southern England in about 1870. It is an allotetraploid species derived from the hybrid Spartina × townsendii, which arose when the European native cordgrass Spartina maritima hybridised with the introduced American Spartina...
. S. anglica is a fertile polyploid derived from the hybrid S.alterniflora × townsendii (S. alterniflora × S. maritima
Spartina maritima
Spartina maritima is a species of cordgrass native to the coasts of western and southern Europe and western Africa, from the Netherlands west across southern England to southern Ireland, and south along the Atlantic coast to Morocco and also on the Mediterranean Sea coasts...
), first found when American S. alterniflora was introduced to southern England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
in about 1870 and came into contact with the local native S. maritima. S. anglica has a variety of traits that allow it to outcompete native plants, including a high saline tolerance and the ability to perform photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
at lower temperatures more productively than other similar plants. It can grow on a wider range of sediments than other species of Spartina, and can survive inundation in salt water
Seawater
Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% . This means that every kilogram of seawater has approximately of dissolved salts . The average density of seawater at the ocean surface is 1.025 g/ml...
for longer periods of time. S. anglica has since spread throughout northwest Europe, and (following introduction for erosion control) eastern North America.
In Willapa Bay
Willapa Bay
Willapa Bay is a bay located on the southwest Pacific coast of Washington state in the United States. The Long Beach Peninsula separates Willapa Bay from the greater expanse of the Pacific Ocean. With over of water surface Willapa Bay is the second largest estuary on the United States Pacific coast...
of Washington state, Spartina alterniflora was probably an accidental introduction during oyster transplants during the nineteenth century. Presently, it covers 6,000-10,000 ha (15 to 25 thousand acres) of land, according to a 1999 estimate. In contrast, in the 1950’s, under 160 ha (400 acres) of Spartina alterniflora were present. It is also making inroads into Puget Sound
Puget Sound
Puget Sound is a sound in the U.S. state of Washington. It is a complex estuarine system of interconnected marine waterways and basins, with one major and one minor connection to the Strait of Juan de Fuca and the Pacific Ocean — Admiralty Inlet being the major connection and...
and Grays Harbor in Washington. The grass can hinder water circulation and drainage
Drainage
Drainage is the natural or artificial removal of surface and sub-surface water from an area. Many agricultural soils need drainage to improve production or to manage water supplies.-Early history:...
or block boating channels. Meadows of S. alterniflora can crowd out native species, reducing biodiversity
Biodiversity
Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...
and altering the environment; as a result of S. alterniflora's growth, invertebrates that live in mud flats disappear as their habitat
Habitat (ecology)
A habitat is an ecological or environmental area that is inhabited by a particular species of animal, plant or other type of organism...
is overgrown, and in turn, food sources shrink for birds who feed on those invertebrates.
In California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, four species of exotic Spartina (S. alterniflora, S. densiflora
Spartina densiflora
Spartina densiflora is a species of grass known by the common name dense-flowered cordgrass. It is native to the coastline of southern South America, where it is a resident of salt marshes. It is also known on the west coast of the United States and parts of the Mediterranean coast as an introduced...
, S. patens
Spartina patens
Spartina patens , also known as salt marsh hay, is a species of cordgrass native to the Atlantic coast of the Americas, from Newfoundland south along the eastern United States to the Caribbean and northeast Mexico...
, and S. anglica) have been introduced to the San Francisco Bay region. Spartina alterniflora is well established in San Francisco Bay, and has had the greatest impact of all the cordgrasses in San Francisco Bay (Ayres et al., 2004). It was introduced in 1973 by the Army Corps of Engineers in an attempt to reclaim marshland, and was spread and replanted around the bay in further restoration projects. It demonstrated an ability to outcompete the native S. foliosa
Spartina foliosa
Spartina foliosa is a species of grass known by the common name California cordgrass. It is native to the salt marshes and mudflats of coastal California and Baja California, especially San Francisco Bay. It is a perennial grass growing from short rhizomes. It produces single stems or clumps of...
, and to potentially eliminate it from San Francisco Bay (Callaway and Josselyn, 1992).
Spartina alterniflora has also been found to hybridize with S. foliosa, producing offspring that may be an even greater threat than S. alterniflora by itself (Anttila et al., 2000). The hybrid can physically modify the environment to the detriment of native species (Ayres et al., 1999), and the hybrid populations have spread into creeks
Creek (tidal)
A tidal creek, tidal channel, or estuary is the portion of a stream that is affected by ebb and flow of ocean tides, in the case that the subject stream discharges to an ocean, sea or strait. Thus this portion of the stream has variable salinity and electrical conductivity over the tidal cycle...
, bay
Bay
A bay is an area of water mostly surrounded by land. Bays generally have calmer waters than the surrounding sea, due to the surrounding land blocking some waves and often reducing winds. Bays also exist as an inlet in a lake or pond. A large bay may be called a gulf, a sea, a sound, or a bight...
s, and more remote coastal locations. The hybrids produce enormous amounts of pollen, which swamp the stigmas of the native S. foliosa flowers to produce even larger numbers of hybrid offspring, leaving the native Spartina little chance to grow as a pure strain. The hybrids also produce much larger numbers of fertile seeds than the native Spartina, and are producing a hybrid population that is not only increasing in numbers, but increasing in its rate of population growth (Ayres et al., 2004). The hybrids may also be able to fertilize themselves, which the native Spartina cannot do, and which increases the spread of the hybrid swarm even further.
Several means of control and eradication have been employed against Spartina alterniflora where it has become a pest. Hand pulling is effective, but only when done thoroughly and carefully, lest the plant's seed
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...
s spread to infest other areas. Glyphosate, an herbicide
Herbicide
Herbicides, also commonly known as weedkillers, are pesticides used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant...
, is approved in Washington to kill it. In Willapa Bay, leafhopper bugs (Prokelisia marginata) have been employed to kill the plants, which threaten the oyster
Oyster
The word oyster is used as a common name for a number of distinct groups of bivalve molluscs which live in marine or brackish habitats. The valves are highly calcified....
industry there. Surveys, by air, land, and sea are conducted in infested and threatened areas near San Francisco to determine Spartina's spread.
The caterpillar
Caterpillar
Caterpillars are the larval form of members of the order Lepidoptera . They are mostly herbivorous in food habit, although some species are insectivorous. Caterpillars are voracious feeders and many of them are considered to be pests in agriculture...
s of Aaron's Skipper
Aaron's Skipper
Poanes aaroni, the Saffron Skipper, is a North American butterfly from the skipper family which occurs in salt marshes along the Atlantic coast.The upper side of the wings are vivid orange, with broad black borders...
(Poanes aaroni) have only been found on this species to date.