smooth cordgrass (spartina alterniflora
TRANSCRIPT
Smooth Cordgrass (Spartina alterniflora)
Thomas Pham
Fish 423
Aquatic Invasion Ecology
Final Report: Fall 2011
Diagnostic information
Scientific name
Order: Poales
Family: Poaceae
Genus: Spartina
Species: alterniflora
Common names: Smooth cordgrass, saltmarsh
cordgrass, saltwater cordgrass, Atlantic
cordgrass, oystergrass
Basic identification key
Using the Key to West Coast Spartina
Species’ dichotomous key one can properly
identify Spartina alterniflora among the other
Spartina species. According to the key S.
alterniflora has leaf blades when fresh,
internodes that are fleshy, a leaf width that is at
most 25mm, reddish streaks or red pigment
often present at the base of young and healthy
shoots. Additionally, the USDA Natural
Resources Conservation service describes S.
alterniflora as a grass with long hollow
rhizomes. It ranges from 2 to 7 feet tall and has
leaf blades that are around 12-20 inches long.
Lastly, during the months of September and
October, seedheads are present that are around
12 inches in length and can carry spikes that
carry 12-15 spikelet seeds.
Life-history and basic ecology
Life cycle, environmental optima and tolerances
Spartina alterniflora is a perennial rhizomatous
grass that grows in intertidal zones (Subudhi et
al. 2009). In specific it grows in salt marsh, mud
flat, and sand flat habitats. It prefers habitats
with low or moderate wave action. Furthermore,
this plant is highly adapted to grow in very high
salinity concentrations and can grow in water
salinities up to 60‰ (Bertness 1991). It can
grow in a variety of substrates including: sand,
silt, cobble, clay, and gravel. S. alterniflora is a
Figure 1. Spartina alterniflora at a salt marsh in East
Sandwich, Massachusetts. Nelson DeBarros @
USDA-NRCS PLANTS Database
particularly persistent species that tolerate a
varying degree of abiotic conditions. It can
survive in complete submersion of water for up
to 12 hours and in water with pH levels ranging
from 4.5 to 8.5 (Landin 1991). Nutrient supply
is a limiting factor for S. alterniflora. Bursesh et
al. (1980) found that nitrogen is an important
determining factor for growth and productivity
for S. alterniflora in Louisiana salt marshes.
Additionally, they observed a greater influence
of nitrogen added to inland meadows compared
to streamside meadow.
Reproductive strategies
Spartina alterniflora has three methods
of reproduction that involve both sexual and
clonal processes. It reproduces by seed, rhizome,
or vegetative fragmentation (Daehler and Strong
1994). It produces inflorescences containing
spikelets which hold
seeds that generally
develop in July through
October. Pollination is
achieved by wind and
seeds are dispersed
primarily dispersed by
water which can carry the
seeds long distances due
to tides and currents.
Vegetative fragmentation
is the process in which
segments of the plant
break off and form a new
plant but is genetically
identical to the original.
Lastly, S. alterniflora can also spread clonally
by rhizomes. When pieces of rhizome root break
off, they can sometimes regrow into a new plant
that is also a genetic clone to the original.
Current geographic distribution
Distribution in the United States
According to the United States
Department of Agriculture Natural Resources
Conservation Service Spartina alterniflora
currently resides among 21 different states
including: Alabama, California, Connecticut,
Delaware, Florida, Georgia, Louisiana,
Massachusetts, Maryland, Maine, Mississippi,
North Carolina, New Hampshire, New Jersey,
New York, Oregon, Rhode Island, South
Carolina, Texas, Virginia, and Washington.
Figure 2. An inundated Spartina alterniflora marsh
Figure 3. Current distribution of Spartina alterniflora across the United States (USGS)
History of invasiveness
Spartina alterniflora is a rhizomatous
grass native to the Atlantic and Gulf coast
marshes of North America (Xiao et al. 2011). It
dominates the marshes in its native range. S.
alterniflora has been introduced to new regions
both intentionally and unintentionally. It has
been introduced to the west coast of the United
States, Great Britain, the Atlantic coast of
Europe, and New Zealand (Marchant et al 1970;
Partridge et al 1987; Hitchcock et al. 1969).
Distribution in Washington State
Spartina alterniflora is non-native to the state of
Washington. There are three main regions of
Washington State that S. alterniflora has
established populations: Puget Sound, Grays
Harbor, and Willapa Bay. It is believed that it
was introduced by accident into Willapa Bay
around the late nineteenth century as a
hitchhiker with oysters shipped from the
Atlantic coast (Dennis et al. 2011). Seeds of S.
alterniflora likely were inadvertently brought
into the same barrels that the oysters were being
shipped in. Furthermore, Stiller and Denton
(1995) performed random amplified
polymorphic DNA (RAPD) analysis to
determine the genetic history of the S.
alterniflora populations in Willapa. Their data
suggests that the entire S. alterniflora population
inhabiting the Willapa Bay region descended
from a single introduced clonal colony. The
establishment of this population was spread
primarily by seed dispersal. Rhizome and
vegetative fragmentation contributed little to the
spread in this region (Civille et al. 2005). S.
alterniflora was recognized as a pest weed in
Willapa Bay and was placed on Washington
State’s noxious weed list in 1989. The
Washington State Noxious Weed Control Board
defines a noxious weed as “the traditional, legal
term for any invasive, non-native plant that
threatens agricultural crops, local ecosystems of
fish and wildlife habitat”. It is currently
classified as a Class A noxious weed meaning
that eradication of this plant is required by law.
Unlike the populations in Willapa Bay, S.
alterniflora was intentionally introduced into
Puget Sound by landowners. It was introduced
into Padilla Bay sometime between 1940 and
1946 by the Dike Island Gun Club in order to
stabilize the land that the gun club was on
(Parker and Aberle 1979). A hybrid species
Spartina anglica is able to hybridize with S.
alterniflora and was introduced to Puget Sound
in 1961 (Hacker et al. 2001).
Populations of S. alterniflora also exist in Grays
Harbor. However, the pathway of introduction
of it is not known for this particular region. In
addition to S. alterniflora, Spartina densiflora is
also found here.
Distribution in Oregon
S. alterniflora is also present in the State
of Oregon, although at much lower densities
than observed in Washington State. As of now
three infestations of S. alterniflora have been
observed in Oregon. One of the colonization’s
took place in the Siuslaw River in Florence,
Oregon. It was intentionally planted around the
1970’s at the Port of Siuslaw (Frenkel 1990,
Strong and Ayres 2009).
S. alterniflora was also detected in Coos Bay in
2005 at a dredge material disposal site (Oregon
Response Plan 2007). It is believed that
unintentional transplantation was the vector for
the introduction of it into Coos Bay.
Figure 4. Distribution of Spartina alterniflora sites in
Washington State 2010 (WSDA)
Finally, the third and most recent infestation of
S. alterniflora in Oregon was discovered in 2008
at Youngs Bay (ODA Plant Division Annual
Report 2010). However, early detection found
the patch to be only 800 square feet in size and
was dealt with quickly. As of 2010 no new
plants have been found in Youngs Bay.
Invasion process
Pathways, vectors and routes of introduction
Spartina alterniflora historically has
invaded the Pacific Northwest by both
intentional and unintentional introductions. The
initial pathway that has led to S. alterniflora’s
invasion into Washington has been through
aquaculture, in particular the stocking of oysters.
S. alterniflora was introduced into Willapa Bay
in the late nineteenth century as part of the
oyster cultivation efforts (Dennis et al. 2011). S.
alterniflora seeds hitchhiked along with oyster
shipments by train from Atlantic marshes where
its native region lay.
In addition to unintentional introductions, there
have also been intentional introductions of S.
alterniflora. In its native range, S. alterniflora is
valued for its ability to alleviate erosion
(Simenstad and Thom. 1995). The very same
properties have led to intentional introduction
into Washington and Oregon. Furthermore, it
has the ability to trap sediment very well. It has
been introduced into New Zealand because of
this property as a tool for estuary restoration
(Partridge 1987).
Factors influencing establishment and spread
There are a number of factors that influence the
establishment of Spartina alterniflora. One
factor that actually slowed the rate of invasion of
it into the Pacific Northwest was Allee effects
which is “a positive relationship between any
component of fitness of a species and density of
conspecifics” (Stephens et al. 1999). Davis et al.
(2004) conducted an experiment and discovered
that pollen limitations can cause an Allee effect
on S. alterniflora meaning that it can slow its
rate of colonization. Additionally, without Allee
effects S. alterniflora would have spread across
Willapa Bay at a much higher rate (Taylor et al.
2004) and likely would have covered the entire
bay a long time ago (Strong and Ayres 2009).
Potential ecological and/or economic impacts
Spartina alterniflora is an ecosystem
engineer. Jones et al. (1994) coined the term
ecosystem engineer and defined it as:
“organisms that directly or indirectly modulate
the availability of resources (other than
themselves) to other species, by causing physical
state changes in biotic or abiotic materials. In so
doing they modify, maintain and/or create
habitats”. S. alterniflora alters the ecosystem in
which it habitats by a number of different
means. It can change nutrient cycling,
hydrology, sediment deposition patterns, and
furthermore it can transform open intertidal
mudflats into elevated meadows filled with
nothing but S. alterniflora (Crooks 2002). These
impacts have led to significant change in the
landscape of estuaries and intertidal zones in the
Pacific Northwest. In the absence of S.
alterniflora estuaries in the Pacific Northwest
are generally gently sloped and shallow, bare
mudflats. However, the S. alterniflora can
transform them into steep and deep tidal
channels. Furthermore, the once bare mudflats
can become completely covered in meadows of
S. alterniflora. In addition, it has the ability to
increase sedimentation and decrease the effects
of wave action (Gleason et al. 1979) while also
causing increased flooding.
S. alterniflora not only affects the abiotic
structure of communities but can also have
impacts on native fauna and flora. It is a robust
invader and can out-compete other species such
as Zostera marina (eelgrass). Not only is this
detrimental to Z. marina but also to the species
that rely on it such various invertebrates
including juvenile Dungeness crab
(Metacarcinus magister) (McMillan et al. 1995).
The loss of Z. marina can also have negatively
cascading effects on Anas Americana (American
wigeon), Anas acuta (Northern Pintail), and
Branta bernicla (Brant) all of which rely on Z.
marina for forage (Oregon Response Plan 2007).
Furthermore, the large colonization of bare
mudflats of S. alterniflora greatly reduces the
open habitat for many different shorebirds and
waterfowl. It is currently listed as a threat to
birds by the American Bird Conservancy. The
disturbance that S. alterniflora can cause on its
habitat may even open up opportunities for other
invasive species. A study by Carr and Dumbauld
(2000) suggests that a non-native crab Carcinus
maenas are more concentrated in areas where
Spartina are found.
S. alterniflora also has the potential to cause
massive economic damage as well. Although it
has not occurred, it has the potential to cause
damage to oyster and commercial fisheries. If
they raise the elevation of the estuaries, they can
become unsuitable for oyster aquaculture.
Oyster farming is a large industry for both
Washington and Oregon State and S. alterniflora
has the potential to cause damage to these
markets by land alterations. Furthermore they
can reduce the prey resources for Oncorhynchus
keta (Chum) in its juvenile stage as well as
Parophrys vetulus (English sole) both of which
are important commercial fish for Washington
and Oregon (Noxious Weed Control Board). In
addition S. alterniflora can also can economic
damage by altering beaches which are important
to the tourism markets for Washington and
Oregon (Oregon Response Plan 2007).
Management strategies and control methods
A large amount of time, money, and
effort has been put into the control and
eradication of Spartina alterniflora in the Pacific
Northwest. In Washington State, management of
S. alterniflora began in the 1990’s (Hedge et al.
2003). In 1995, the WSDA was put in control of
its management. In 2003, the Portland State
University Center for Lakes and Reservoirs
created the Oregon Spartina Response Plan with
the goal of “prevent(ing) the establishment and
spread of any Spartina species in Oregon
estuaries and coastal wetlands”. A number of
different strategies have been used to control S.
alterniflora. Removal by hand has been used but
is limited in a number of ways. It is highly time
consuming to remove because care must be
taken to remove the entire plant. If residual
rhizomes are left behind, they have the potential
to grow back. This strategy has more
effectiveness in controlling younger infestations
than mature (Hedge et al. 2003). Another
method that has been used is mowing. Once
again however, this strategy is also limited. It
was found to be neither effective nor cheap as
sites had to be mowed multiple times to
effectively eliminate it. In addition, herbicides
have also been used. The only authorized
herbicide for control of S. alterniflora by the
Washington Aquatic Plant Management
Program Environmental Impact Statement is
Rodeo whose main active ingredient is
glyphosate. There have been large variations in
its effectiveness ranging from no effect to
complete elimination. The most effective
method of control in Washington has been a
combination of mowing followed up by Rodeo
application after it has regrown to 30-45cm,
although it has been found to be highly costly
(Hedge et al. 2003). One last control method that
has been used is a biological control with the
species Prokelisia marginata (Homopteran plant
hopper). This particular species feeds on
Spartina species, specifically its vascular fluids.
However, Gustafson et al. (2006) tested the
effects of P. marginata grazing on Spartina
biomass and found that it is does not exert strong
top-down control on S. alterniflora.
Literature Cited
Bertness MD (1991). Zonation of Spartina
Patens and Spartina Alterniflora in New
England Salt Marsh. Ecology 72: 138-148.
Buresh RJ, Delaune RD, Patrick WH (1980).
Nitrogen and Phosphorus Distribution and
Utilization by Spartina alterniflora in a
Louisiana Gulf Coast Marsh. Estuaries 3:
111-121.
Carr EM, Dumbauld BR (2000). Status of the
European green crab invasion in
Washington coastal estuaries: can
expansion be prevented? Journal of
Shellfish Research 19 : 629-630.
Civille JC, Sayce K, Smith SD, Strong DR
(2005). Reconstructing a century of
Spartina alterniflora invasion with historical
records and contemporary remote sensing.
Ecoscience 12: 330-338.
Crooks (2002). Characterizing Ecosystem-Level
Consequences of Biological Invasions: The
Role of Ecosystem Engineers. OIKOS 97:
153-166.
Daehler CC, Strong DR (1994). Variable
Reproductive Output Among Clones of
Spartina alterniflora (Poaceae) Invading
San Francisco Bay, California: The
Influence of Herbivory, Pollination, and
Establishment Site. American Journal of
Botany 81: 307-313.
Davis HG, Taylor CM, Lambrinos LG, Strong
DR, Mooney HA (2004). Pollen
Limitations Causes an Allee Effect in a
Wind-Pollinated Invasive Grass (Spartina
alterniflora). PNAS: 101: 13804-13807.
Dennis B, Civille JC, Strong DR (2011). Lateral
spread of invasive Spartina alterniflora in
uncrowded environments. Biological
Invasions 13: 401-411.
Gleason ML, Elmer DA, Pien NC, Fisher JS
(1979). Effects of Stem Density upon
Sediment Retention by Salt Marsh Cord
Grass, Spartina alterniflora Loisel.
Estuaries 2: 271-273.
Gustafson DJ, Kilheffer J, Silliman BR (2006).
Relative Effects of Littoraria irrorata and
Prokelisia marginata on Spartina
alterniflora. Estuaries and Coasts 29: 639-
644.
Hedge P, Kriwoken LK, Patten K (2003). A
Review of Spartina Management in
Washington State, US. Journal of Aquatic
Plant Management 41: 82-90.
Hitchcock CL, Cronquist A, Ownbey M (1969)
Vascular Plants of the Pacific Northwest.
Part 1: Vascular Cryptogams,
Gymnosperms, and Monocotyledons.
University of Washington Press, Seattle,
Washington
Jones CG, Lawton JH, Shachak M (1994).
Organisms as ecosystem engineers. OIKOS
69: 373-386.
Marchant CJ (1970). Evolution in Spartina
(Gramineae) IV. The cytology of S.
alterniflora Loisel. in North America.
Botanical Journal of the Linnean Society
63: 321-326.
McMillan RO, Armstrong DA, Dineel PA
(1995). Comparison of intertidal habitat
use and growth rates of two northern Puget
Sound cohorts of 0+ age Dungeness crab,
Cancer magister. Estuaries 18: 390-398.
Parker RC, Aberle B (1979). A situation report
on the Spartina infestation in northwest
Washington. Unpublished report to the
Washington State Department of game,
Mount Vernon
Partridge TR (1987). Spartina in New Zealand.
New Zealand Journal of Botany 25: 567-
575.
Simenstad CA, Thom RM (1995). Spartina
alterniflora (smooth cordgrass) as an
invasive halophyte in Pacific Northwest
estuaries. Hortus Northwest 6:9-12, 38-40.
Stiller JW, Denton AL (1995). One hundred
years of Spartina altemiflora (Poaceae) in
Willapa Bay, Washington: random
amplified polymorphic DNA analysis of an
invasive population. Molecular Ecology 4:
355-363.
Stephens PA, Sutherland WJ, Freckleton RP
(1999). What is the Allee effect? OIKOs
87: 185-190.
Strong DR, Ayres DA (2009) Spartina
Introductions and Consequences in Salt
Marshes. In: Silliman BR (ed), Grosholz
ED (ed), Bertness MD (ed) Human Impacts
on Salt Marshes: A Global Perspective, 1st
edn. University of California press,
Berkeley, CA.
Subudhi PK, Baisakh N (2011). Spartina
alterniflora Loisel., a halophyte grass model
to dissect salt stress tolerance. In Vitro
Cellular & Developmental Biology – Plant
47: 441-457.
Taylor CM, Davis HG, Civille JC, Grevstad FS,
Hastings A (2004). Consequences of an
Allee effect in the invasion of a pacific
estuary by Spartina alterniflora. Ecology
85: 3254-3266.
Xiao Y, Tang J, Qing H, Zhou C, An S (2011).
Effects of salinity and clonal integration on
growth and sexual reproduction of the
invasive grass Spartina alterniflora. Flora
206: 736-741.
Other key sources of information and
bibliographies
Written Findings of the Washington State
Noxious Weed Control Board (1995)
http://www.nwcb.wa.gov/siteFiles/Spartina_alter
niflora.pdf
Oregon Spartina Response Plan 2007
http://www.clr.pdx.edu/docs/OSRP.pdf
Spartina Eradication Program 2010 Progress
Report
http://agr.wa.gov/PlantsInsects/Weeds/Spartina/
docs/SpartinaReport2010.pdf
Oregon Department of Agriculture Plant
Division Annual Report 2010
http://www.oregon.gov/ODA/PLANT/docs/pdf/
plant_annual_report_2010.pdf?ga=t
West Coast Governors’ Agreement on Ocean
Health Spartina Eradication Action
Coordination Team Work Plan
http://westcoastoceans.gov/Docs/Spartina_Final
_Work_Plan.pdf
Expert contact information in PNW
Kathleen Sayce
P.O. Box 91
Nahcotta, WA 98637
Phone: (360) 665-5292 (H), (360) 642-1166 (W)
Vanessa Howard
Center for Lake and Reservoirs
Portland State University
P.O. Box 751
Portland, OR 97207-0751
Phone: (503) 725-9076
Fax: (503) 725-3834
Nancy Ness
Grays Harbor County
Noxious Weed Board Coordinator
P.O. Box R
Elma, WA 98541
Phone: (360) 482-2265
Fax: (360) 482-2662
Kyle Murphy
WSDA Spartina Coordinator
P.O. Box 42560
Olympia, WA 98504
Phone: (360) 902-1923
Current research and management efforts
The state of Washington has devoted a
large amount of time and resources to eradicate
Spartina alterniflora. Since 1995, the
Washington State Department of Agriculture has
spearheaded the eradication of Spartina species.
They have coordinated a number of stakeholders
and entities in working together to manage
Spartina. They have seen great success in
eliminating S. alterniflora as well as other
Spartina species in the state. From a record high
of 9,260 acres of Spartina spp. observed in
2003, the WSDA has reduced that amount to 27
acres as of 2010 (Spartina Eradication Program
2010 Progress Report). The effort continues
although they believe that the last few acres will
be the most difficult to remove. The WSDA
estimates that 7 solid acres of Spartina will
remain in Willapa Bay in 2011, less than 0.05
acres in Grays Harbor, and 5 acres in Puget
Figure 5. Solid acres of Spartina by year statewide based on WSDA estimates. The blue line represents historic
Spartina infestations since 2003. The red line indicates the projected Spartina infestation level through 2014.
Projection assumes continued funding.
Sound. Currently, they are continuing to use
integrated pest management techniques such as
mechanical, chemical, manual control, or a
combination of them as previously described,
although more effort is being put into shoreline
surveillance as the numbers of acres of Spartina
have been greatly reduced.
On September 18, 2006 the governors of
California, Oregon, and Washington announced
the West Coast Governors’ Agreement on Ocean
Health. Through this agreement they called for
collaboration to manage and protect the ocean
and coastal resources along the West Coast.
Through this agreement a Spartina eradication
program was developed with the goal of
eliminating non-native Spartina off of the West
Coast by 2018. This program created a
comprehensive work plan and outlined a number
of tasks in order to achieve the goal of complete
eradication. According to the work plan, they are
working on developing an internet based GIS
(geographic information system) to define the
areas in which Spartina has been eradication.
Overall this agreement has combined the efforts
of California, Oregon, and Washington in
eliminating Spartina spp. With the bulk of the
infestations managed, the remaining work is
synthesizing the collective efforts between
agencies and states.