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2006 SOUTHEASTERN NATURALIST 5(4):747–756
Baseline Mapping of Phragmites australis (Common Reed)
in Three Coastal Mississippi Estuarine Basins
Mark S. Peterson1,* and Melissa L. Partyka2
Abstract - Over the last two decades, the northern Gulf of Mexico has undergone
tremendous growth and development that has resulted in extensive and ongoing
habitat modification. We had the opportunity to survey the main channels and
bayous of three coastal estuarine basins for the presence and coverage of the
invasive Phragmites australis (common reed). The occurrence and area of P.
australis was highly variable among the lower Pascagoula River, Back Bay of
Biloxi, and St. Louis Bay basins, with the largest amount of coverage (0.489 km2)
found within the lower Pascagoula River basin and the smallest in Back Bay of
Biloxi (0.0056 km2). Monospecific-stand coverage (47.2%) dominated both
mixed-tree (27.2%) and mixed-marsh (26.6%) coverages in the lower Pascagoula
River basin, whereas in the Back Bay of Biloxi, mixed-marsh coverage (71.4%)
was greater than monospecific-stand (25.0%) and mixed-tree (3.6%) coverages.
The only portion of St. Louis Bay containing P. australis (0.069 km2) was near
the mouth of the Jourdan River, with monospecific-stand (62.3%) dominating the
mixed-marsh (36.2%) and mixed-tree (1.5%) coverages. Although we were not
able to survey all possible areas of each estuarine basin, the information gained in
this study provides baseline data on the occurrence of this invasive species in the
three main Mississippi coastal basins. Future monitoring of the spread of common
reed, especially in the light of continued coastal development, is necessary if
resource managers are to make informed decisions about which management action
(water diversions and restoration scenarios) might positively influence this
highly invasive native species.
Like many coastal regions in the US over the last decade, the northern
Gulf of Mexico (GOM) has undergone tremendous growth and development,
resulting in extensive and ongoing habitat modification. Worldwide, invasive
species have had direct and indirect effects on native coastal biota. In
New England, Phragmites australis (Cav.) Trin ex Steud. (common reed),
has been shown to quickly replace Spartina alterniflora Loisel. (smooth
cordgrass) and Juncus spp. (needlerush) and ultimately form dense monoculture
stands (Able et al. 2003).
Common reed is typically associated with disturbed marsh areas
(modified plant communities, hydrology, or topography) altered by
storms or humans (Marks et al. 1994, Roman et al. 1984, White et al.
1Department of Coastal Sciences, 703 East Beach Drive, The University of Southern
Mississippi, Ocean Springs, MS 39564. 2University of North Carolina-Wilmington,
Center for Marine Science, 5600 Marvin Moss Lane, Wilmington, NC 28409. *Corresponding
author - email@example.com.
748 Southeastern Naturalist Vol. 5, No. 4
2004). In fact, Burdick and Konisky (2003) showed common reed had the
highest growth in low salinity/high elevation sites (mean = 14 practical
salinity units [psu] and above mean high tide) compared to mid- (mean
high tide) or low (below mean high tide) elevation sites in mean salinities
of 18 psu and 23 psu, respectively. Common reed has the ability to germinate
in salinities up to 20 psu and water depths to 5 cm (Marks et al.
1994), but germination increases as salinity decreases, and is not affected
at salinities below 10 psu. Finally, once established, P. australis can
modify the area into conditions highly conducive to its further propagation
and establishment (Bart and Hartman 2000).
Common reed historically has occurred in North America (Saltonstall
2002), but the 11 native haplotypes once common across North America
have been replaced in a number of areas with a European haplotype
(Saltonstall 2003) that is competitively superior. The Gulf coast region has
a distinguishable haplotype, which differs from all other North American
types, and it has yet to be resolved if it is native to the region (Saltonstall
2002, 2003). Saltonstall (2003) and White et al. (2004) noted some morphological
differences among clones of this population in Louisiana that
Modification of estuarine habitat leads to an increase of monospecific
stands of common reed at the expense of other salt marsh vegetation
(Havens et al. 2003). Establishment and spread of common reed in some
regions directly or indirectly influence community structure and habitat
use by a myriad of estuarine species (Marks et al. 1994, Warren et al.
2001, Bart and Hartman 2002, Hanson et al. 2002, Raichel et al. 2003).
Finally, disturbance in the form of experimentally increased nutrients and
alteration of the surrounding brackish and salt marsh vegetation matrix
enhanced the expansion of common reed in Rhode Island (Minchinton
and Bertness 2003). Although there has been much research recently,
scientific uncertainties remain, and we do not have a clear understanding
of the short- and long-term impacts of common reed on salt marshes and
In the north-central GOM, common reed is present and appears to be
expanding in areas of altered marsh and riverine habitat. This is particularly
true for Louisiana and Alabama (M.S. Peterson, pers. observ.); however,
in coastal Mississippi we do not know its status nor do we know
how rapidly it is spreading into disturbed areas. Thus, the primary objective
of this research was to develop a set of base maps of common reed
distribution and coverage in representative systems in all three Mississippi
coastal counties using GIS technology. These maps may serve as a
baseline to track future changes in common reed distribution and abundance,
allow wise management decisions on impacts to critical fishery
nursery habitat, and allow resource agencies to make informed decisions
about which management action (water diversions and restoration
2006 M.S. Peterson and M.L. Partyka 749
scenarios) might positively influence this highly invasive native species
(sensu Occhipinti-Ambrogi and Galil 2004).
Materials and Methods
The presence and area of coverage by common reed was mapped within
the main channels and bayous of the three major coastal basins along the
Mississippi coast: the lower Pascagoula River basin, Biloxi’s Back Bay, and
St. Louis Bay. Smaller creeks and bayous of each basin were not mapped due
to reduced access by our boats and limited funding. Quick Bird® false-color
infrared satellite imagery (1.7-m resolution) taken in July 2002 was obtained,
and images were combined to create composites of each basin. The
occurrence and area covered by common reed was determined in situ using
these composites as base maps. Patches were classified into three categories:
1) monospecific stands; 2) mixed marsh, or patches with an understory of
other marsh species; and 3) mixed trees, or patches where the canopy was
taller than the common reed. A general description of habitat conditions and
alterations of each basin is provided in Table 1.
Due to the low band number (4 bands) and large spatial coverage of the
imagery, full extraction of pixels containing common reed was impossible.
Accuracy assessments of the above method revealed large discrepancies,
and, consequently, a combination of field sampling and image analysis
proved to be the most accurate method of mapping this species. The
imagery initially was analyzed using ERDAS Imagine® 8.6 software to
distinguish pixels most likely to contain common reed based on information
obtained a priori. Unsupervised classifications were performed and
non-target pixels masked out through an iterative process until the closest
approximation of field conditions was obtained. The resulting image was
Table 1. Summary of the general habitat modifications within the three Mississippi basins
evaluated in this study.
Basin Subsystem Modifications
Pascagoula River East Lower portion of river from immediately north of
Highway 90 south to Mississippi Sound, there are
significant bulkheads and rip-rap, marinas, ship
building, and the Navy homeport facility. Salinity
wedge moves markedly upestuary due to channelization.
West Mainly housing developments and associated piers,
docks and bulkheading.
Back Bay of East-West Mainly marinas, bulkheading, causeway construction,
Biloxi piers, and docks.
West All of the above plus a power plant and industrial park
St. Louis Bay Jourdan River Well developed with homes, filled and bulkheaded marsh,
piers, and docks.
Wolf River Mainly natural and state-protected system.
750 Southeastern Naturalist Vol. 5, No. 4
converted into a vector file and exported as arc-interchange files (.eoo).
This format then was used as the baseline from which shape files of each
patch category were created.
The actual mapping of common reed patches was carried out using
ESRITM ArcInfo® 8.3. The composite base-map images were overlain with
the .eoo files for visual reference. Using the editor, new polygon shape files
were created for each patch category by tracing the .eoo files pixel by pixel
to match what was seen in the field. The areas of each polygon for each
category were calculated once all patches had been rendered and confirmed
against the field data.
Results and Discussion
The occurrence and area of common reed was highly variable among
the three study basins, with the largest amount of coverage (0.489 km2)
found within the lower Pascagoula River basin (Fig. 1). Monospecificstand
coverage (47.2%) dominated both mixed-tree (27.2%) and mixedmarsh
(26.6%) coverages in this basin. The east and west distributaries of
the lower Pascagoula River basin are markedly different in terms of development,
with the east distributary being more developed by heavy industry
and light development compared to mainly housing development in the
west distributary (Table 1). The entire basin has a gradual and prominent
salinity gradient (range from 0.0 to 11.7 psu upstream up to 30 psu near
the mouth depending on discharge; Christmas 1973) along its length, but
because of the channelization in the east distributary for shipping, the salt
wedge moves markedly farther up-estuary than in the natural west distributary
(Christmas 1973; Peterson et al., in press). Much of common
reed occurrence in the east distributary is on higher elevation ground near
the highly modified, more saline habitat. Conversely, it can be found
throughout the west distributary, but mainly up-estuary in low salinity
reaches of the basin. This pattern documented in the lower Pascagoula
River estuarine basin is common elsewhere. For example, common reed
invades natural and altered estuarine environments (Marks et al. 1994,
Bart and Hartman 2002), and it is a particularly aggressive colonizer of
disturbed sites (Havens et al. 2003). This is particularly true when the
surrounding brackish and salt marsh vegetation matrix has been altered,
further enhancing expansion (Minchinton and Bertness 2003). Typically,
common reed colonizes freshwater and oligohaline marshes without site
preference; however, in higher salinity sites, common reed preferentially
colonizes creek bank levees and disturbed upland borders with greater
elevation compared to natural salt marsh (Warren et al. 2001). Clearly,
hydrologic modification (e.g., tidal restriction, increased freshwater input
Figure 1 (opposite page). Map of Phragmites australis throughout the lower
Pascagoula River basin with a comparison of area coverage by monospecific stands,
stands mixed with trees, and stands mixed with salt marsh grass.
2006 M.S. Peterson and M.L. Partyka 751
752 Southeastern Naturalist Vol. 5, No. 4
from developments) and increased filling of marsh upland habitats (e.g.,
road development, dredge maintenance) enhance invasion and expansion
of common reed into the lower reaches of coastal basins (Burdick and
The Back Bay of Biloxi had the lowest area of common reed (0.0056
km2) of the three estuarine basins (Fig. 2), with mixed-marsh coverage
(71.4%) being greater than monospecific stands (25.0%) and mixed trees
Figure 2. Map of Phragmites australis throughout Back Bay of Biloxi with a
comparison of area coverage for the entire Back Bay of Biloxi basin by monospecific
stands, stands mixed with trees, and stands mixed with salt marsh grass. Insets (A, B,
and C) are enlargements of specific areas where P. australis occurred.
2006 M.S. Peterson and M.L. Partyka 753
(3.6%). Common reed in Back Bay of Biloxi occurs in small patches in areas
of altered elevation mainly in the western portion where the Biloxi and
Tchoutacabouffa Rivers empty into the bay. Salinity in this region is typically
lower and more variable (1.4–10 psu) than in the east portion (up to
18.8 psu) of Back Bay of Biloxi, and salinity overall is higher here than in
the area of the lower Pascagoula River basin we examined, but varied with
discharge (Christmas 1973; M.S. Peterson, pers. observ.). The entire bay
system has moderate to severe alteration in addition to heavy industry in the
west portion of the bay (Table 1).
The only portion of St. Louis Bay containing the common reed (0.069 km2)
was near the mouth of the Jourdan River (Fig. 3), with monospecific-stand
Figure 3. Map of Phragmites australis associated with areas of Jourdan River and St.
Louis Bay, with a comparison of area coverage by monospecific stands, stands mixed
with trees, and stands mixed with salt marsh grass.
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(62.3%) dominating the mixed-marsh (36.2%) and mixed-tree (1.5%) coverage.
In addition to the Wolf River, which empties into the northeastern edge of
St. Louis Bay (7.2 km across St. Louis Bay), the Jourdan River is one of the
main freshwater sources for St. Louis Bay (salinity from 0.0 psu upstream to
up to 13.8 psu near mouth with St. Louis Bay depending on discharge;
Christmas 1973) and has well-developed housing complexes all along the
river channel and south of the terminus with St. Louis Bay. The areas in which
we found common reed were associated with higher elevations than the
surrounding marsh complex (Table 1), and large monospecific stands were
common in this area.
Although we were not able to survey all possible creeks and small
bayous of each estuarine basin as noted above, the information gained in
this study provides baseline data on the occurrence of this species in three
prominent Mississippi coastal basins. Though common reed is most probably
a native species of the Gulf Coast, it still possesses the capability of
expanding into large monospecific stands in habitats altered by development,
dredging and improper spoil deposition, or natural disaster
modifying natural areas. Modification of estuarine habitat leads to an
increase of monospecific stands of common reed at the expense of other
salt marsh vegetation (Havens et al. 2003). We predict as further development
occurs along the Gulf coast post-Katrina, common reed will spread
to areas of low salinity and to areas of higher salinity with higher elevations.
As documented by Burdick and Konisky (2003), common reed
dispersal and growth is coupled with mid- to low salinity environments
and co-varies with elevation such that short-term responses like
bulkheading and dredging to natural disasters like Hurricane Katrina
along the Mississippi Gulf coast may have long-term consequences such
as the enhancement of large monospecific stands of common reed. This
structural change in salt marsh and wetland habitats may have secondary
effects on the sustainability of the basin via direct and indirect influences
on community structure and habitat use by a myriad of estuarine species
(Bart and Hartman 2002, Hanson et al. 2002, Raichel et al. 2003, Warren
et al. 2001). Thus, future monitoring of the spread of common reed,
especially in the light of continued coastal development, is necessary if
resource managers are to make informed decisions about which management
action (water diversions and restoration scenarios) might positively
influence this highly invasive native species.
We wish to thank T. Wells, M. Weber, S.T. Ross, J. McDonald, B.H. Comyns, P.
Grammer, and B. Lezina for assistance in the field, as well as M. Foster for help with
initial GIS work. The Gulf Coast Geospatial Center of The University of Southern
Mississippi provided base maps and assistance with GIS applications. Funding for this
work was provided by the Coastal Impact and Assistance Program (CIAP) of NOAA,
2006 M.S. Peterson and M.L. Partyka 755
which was administered by the Mississippi Department of Environmental Quality. We
especially thank Elizabeth Barber of the CIAP for support of this project.
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