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8/3/2019 Maryland; Large-Scale Restoration of Eelgrass (Zostera marina) in the Patuxent and Potomac Rivers
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Large-Scale Restoration of Eelgrass (Zostera marina) in thePatuxent and Potomac Rivers, Maryland
Submitted by:
Kathryn Busch
Rebecca Raves Golden
Maryland Department of Natural ResourcesTawes State Office Building, D-2
580 Taylor AvenueAnnapolis, MD 21401
March 31, 2009
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Introduction
Submerged aquatic vegetation (SAV) in the Chesapeake Bay has experienced
several dramatic population declines beginning in the 1930s with the decline ofZostera
marina (eelgrass) (Orth & Moore 1984). During the 1960s and 1970s, all species
declined baywide coincident with regional water quality degradation and Hurricane
Agnes in 1972 (Kemp et al. 1983; Orth & Moore 1983a; Orth & Moore 1984). While
tidal freshwater SAV populations have recovered substantially, mesohaline reaches of the
lower bay have not recovered (Orth et al. 2008). Numerous areas in the bay, the Patuxent
and Potomac Rivers in particular, were densely vegetated with eelgrass. However,
distribution is now restricted to Tangier Sound on the lower Eastern Shore of Maryland, a
geographic shift of over 50 miles since the 1970s (Orth et al. 2008).
Because of the functions SAV serve in maintaining a healthy estuarine ecosystem,
SAV restoration has become an important component of Chesapeake Bay restoration.
The Chesapeake Bay Program created a Strategy to Accelerate the Protection and
Restoration of Submerged Aquatic Vegetation in the Chesapeake Bay. The Strategy, the
result of more than a year-long effort among Chesapeake Bay SAV researchers and
managers, identifies a variety of actions necessary to increase SAV populations in the
Bay. The actions fall into four major categories:
1. improve water clarity sufficient for supporting healthy SAV populations,
2. protect existing beds from impacts by anthroprogenic sources and exotic species,
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When the Chesapeake Bay Program and its partners created the Strategy, attention
was given to the need for SAV restoration on a large-scale and eelgrass was identified in
the Strategy as one of two species with great potential for large-scale restoration in the
Chesapeake Bay. Early planting and reseeding efforts in Maryland and Virginia
demonstrated the potential for using eelgrass in restoration projects, but development and
refinement of large-scale restoration techniques was necessary.
Early eelgrass restoration efforts involved manually transplanting whole adult
eelgrass plants in the form of sods, cores or bareroot plants from healthy source beds to
restoration locations (Davis & Short 1997; Fonseca et al. 1982; 1994; Orth et al. 1999).
Limitations of these methods include the availability and location of donor beds, impacts
of harvesting on the donor beds and expense due to the labor and time intensive nature.
Attempts have been made to automate this method by utilizing a mechanized planting
boat and underwater harvesting and planting machines to accommodate large-scale
projects (Fishman et al. 2004; Paling et al. 2001a; Paling et al 2001b).
While transplanting adult plants is still utilized as a restoration method, there has
been increasing evidence that eelgrass seed dispersal can be a viable option for large-
scale restoration projects (Granger et al. 2002; Harwell & Orth 1999; Orth et al. 1994;
2003). Seed broadcasting appears to be a more efficient and cost effective technique for
SAV restoration (Orth et al. 2000) with the added benefit of not having to remove adult
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plantings and water quality monitoring) outlined as a requirement of the strategy for large
scale restoration locations. Prior to the decline of SAV beds in Chesapeake Bay between
the 1960s and 1970s, the Patuxent River supported populations of SAV including
Zannichellia palistris,Ruppia maritima, and Potamogeton perfoliatus (Brush and Davis
1984). Both stratigraphic records and groundtruthing evidence suggests the presence of
Z. marina, eelgrass, historically throughout the mesohaline portion of the Patuxent and
Potomac Rivers (Pfitzenmeyer & Drobeck 1963; Haramis & Carter 1983; Orth & Moore
1983a; Brush & Davis 1984; Brush & Hilgartner 2000).
A resurgence of SAV in the tidal freshwater reach and oligohaline portion of the
Patuxent River since 1993 has been attributed to significant reductions in pollutant loads
and resulting improvements in water clarity. When this project began, the 2004 aerial
survey recorded 220 acres of SAV in the tidal fresh portion, 107% of the 205-acre goal
for this portion of the river, and 106 acres in the oligohaline region, 92% of the 115-acre
goal for that area (Maryland Department of Natural Resources 2005). However, SAV
populations remain sparse in the mesohaline region of the Patuxent River. Only 42 acres
were mapped in 2004, far below the 1,634 acre goal for this portion of the river
(Maryland Department of Natural Resources 2005).
In 2004, SAV coverage in the Potomac River had increased somewhat since 1984
but acreage was still far short of acreage goals in some regions. The 2004 aerial survey
recorded 1,256 acres of SAV in the tidal fresh portion, 59% of the 2,142-acre goal
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7,088-acre goal for that portion of the river (Maryland Department of Natural Resources
2005).
In this multi-year investigation, we conducted and examined outcomes of large-
scale eelgrass seed restoration efforts in two Maryland river systems from 2004 to 2008.
Multiple seed collection, processing, storage and seed dispersal techniques were designed
and compared. The efficiency of manual eelgrass seed collection (snorkeling and
SCUBA) was compared to mechanical harvest. Several seed storage conditions and
processing techniques were investigated in order to maximize viable seed yield for fall
seed broadcast activities. The associated costs for two seed dispersal techniques, fall
seed broadcast and spring seed bag methods, were also compared. In addition to methods
development and refinement, this investigation analyzes the influence of site-specific
SAV habitat conditions on eelgrass seedling establishment and long-term survival, as
well as evaluates the relative success of this multi-year large-scale eelgrass restoration
project.
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Methods
Study Sites
Locations for large-scale restoration activity were determined using a
geographical information system (GIS) based SAV Restoration Targeting System
(Parham & Karrh 1998). The model incorporates seven layers of habitat data (light
attenuation, seston, chlorophyll a, dissolved inorganic nitrogen and phosphorous,
bathymetry and salinity) to evaluate the potential of a particular area to support SAV
populations. Habitat data from three years (2000-2003) prior to the start of the project
was incorporated into the model and updated in subsequent years of the project as data
became available.
Five sites in the lower mesohaline Patuxent River and five sites in the lower
mesohaline Potomac River, MD were identified as potential habitats for eelgrass
recolonization based on the results of Maryland DNRs SAV Restoration Targeting
System. The following sites were identified on the Patuxent River; Parrans Hollow (lat
38.4119N, long 76.5275W), Jefferson Patterson Park (lat 38.4073N, long 76.5211W),
Myrtle Point (lat 38.3293N, long 76.4916W), Hungerford Creek (lat 38.3496N, long
76.4720W), and Solomons Island (lat 38.3150N, long 76.4542W) (Figure 1). Five
sites on the Potomac were also identified; Cherryfield Point (lat 38.1303N, long
76.4596W), Piney Point (lat 38.1380N, long 76.5027W), Sage Point (lat 38.1167N,
long 76.4333W), St. George Island (lat 38.1333N, long 76.4833W), and Kitts Point
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not begin until at least 50% of the seeds within reproductive shoot spadices were mature
in order to ensure harvesting occurred during the peak of seed production. Reproductive
shoots were collected manually using SCUBA (Granger et al. 2002) or snorkeling in
2003 and 2006. Between 2004 and 2008, a mechanical harvest machine (Pristine Marine,
M J McCook & Associates, La Plata, Maryland) was utilized (Figure 4).
Immediately following collection, eelgrass reproductive material was manually
loaded into nylon mesh bags (113.5 L), secured at a nearby dock, and kept submerged in
ambient water until utilized for one of two seed dispersal methods.
Large-Scale Seed Dispersal Methods
Seeds were dispersed in large-scale plots, from 0.1 to 5 acres, at various sites on
the Patuxent and Potomac Rivers between 2003 and 2008 utilizing two methods. A
portion of the seed material collected was transported to the Piney Point Aquaculture
Facility (located in St. Marys County, Maryland) by boat or truck within 24 hours of
collection where the material underwent processing and storage procedures in order to
extract mature seeds for fall seed broadcast. The remainder of the harvested material was
transferred to seed bags for immediate spring deployment.
Fall Seed Broadcast: Processing, Storage and Broadcast
After collection, seed material was transferred from mesh bags into one of eight,
75,708 L (9.8 x 9.8 x 10.4-m) or one of sixteen 37,097 L (6.1 x 6.1 x 1.2-m) greenhouse
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levels to the seed collection areas (~14psu), each basin was augmented with aquaculture-
grade sea salts as necessary. For the first 3 years of the project (2003-2005) 208-L drums
filled with salt were placed directly below the water inlet in each individual basin to
rapidly dissolve the salt and increase salinity above ambient levels. From 2006 to 2008,
salinity was closely controlled using a concentrated brine solution added to the main
incoming water line feeding all basins. In addition, each basin was aerated with evenly
positioned air stones at a density of one per 1,700 L and maintained 5-6 mg/L dissolved
oxygen levels.
While in the basins, the eelgrass seeds slowly separated from the decomposing
reproductive shoots over the following 3 or 4 weeks. After all the seeds had been
released and settled to the bottom of the basins, the seed/reproductive shoot slurry was
pumped by a diaphragm pump into a series of stacked settling trays to allow the passive
accumulation of seeds while discarding the non-seed material. The seeds that were
separated from the bulk of the vegetative material were then transported to another filter
system and moved through a series of progressively smaller filters (2380 m, 1800 m
and 1000 m, respectively) to remove non-seed material.
Once separated from all other reproductive material, the seeds were held in a
9,464 L tank recirculating system. System water was aerated, held at ambient
temperature (18-28oC) and kept at 14psu until dispersal. Beginning in 2006, seeds were
stored in the same recirculating system however, salinity was increased to 18psu and
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replicate 5 ml samples of seed material. Viability was determined using a squeeze test
(R. Orth 2004, Virginia Institute of Marine Science, Gloucester Pt., VA, personal
communication).
Eelgrass seeds were broadcast manually (Orth et al. 1994) during the fall of 2003,
2006, 2007 and 2008. A mechanical seed sprayer (C& K Lord, Inc) was utilized to
broadcast seeds in the fall of 2004 and 2005. The seed sprayer was mounted to a boat,
capable of evenly dispersing seeds at suitable densities (100,000 to 300,000 seeds/acre) at
the rate of 10 minutes/acre (Figure 5). The flow of the seed sprayer was calibrated and
adjusted to distribute seeds uniformly at the desired density. Seeds were loaded into the
seed broadcast machine where the seeds were mixed with water and expelled into the
water column. All seed broadcasts took place in October before the ambient water
temperatures dropped below 15C, prior to eelgrass seed germination (Moore et al. 1993;
Orth & Moore 1983b).
Spring Seed Bag Method
A portion of collected eelgrass reproductive seed material was prepared for
immediate deployment following a buoy-deployed seeding system (BuDSS) developed
by Pickerell et al. (2005; 2006) with modifications. A known volume of reproductive
material was subsampled and the seeds enumerated. Based on the seed estimates, a
volume of reproductive seed material necessary to achieve the desired seeding density
was transferred to pre-measured, coarse (7 x 7-mm) mesh bags with buoys and attached
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apart. The goal seeding density at each location was approximately 37 seeds/m2 despite
varied plot size at each location.
Eelgrass Monitoring and Analysis
Adult plant monitoring
Adult eelgrass transplants were monitored for change in density one month, six
months and twelve months after transplant. In 2005 and 2006, additional monitoring was
performed monthly throughout the summer (May-August). If planting units were
observed twelve months after sampling, monitoring continued during the spring, summer
and fall of subsequent years. Transplant survival was calculated as the proportion of
planting units observed during each monitoring period divided by the number of initial
transplants. When individual planting units in each plot could not be distinguished due to
lateral expansion, survival for that plot was assumed to be 100%.
Seed plot monitoring
Seedling establishment was calculated as the proportion of initial seeds dispersed
that were observed as germinated seedlings the following spring. Eelgrass shoot density
was monitored along two to four non-destructive, 1 m2 belt transects (Burdick &
Kendrick 2001) in each of the seed dispersal plots. Initial eelgrass monitoring occurred
in the spring after seed dispersal with successive monitoring in the summer (three months
after initial monitoring) and fall (six months after initial monitoring). The survival of
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conductivity, pH, dissolved oxygen, turbidity and fluorescence data were collected every
four seconds by a shipboard YSI 6600 sonde (Yellow Springs, OH) (Michael et al. 2008).
Two YSI 6600 EDS sondes on the Patuxent River and three sondes on the
Potomac River were deployed during the monitoring period (2004-2007) to provide
temporally intensive habitat assessments of adjacent restoration study sites throughout the
SAV growing season (April-October). On the Patuxent River, stations were deployed at
the Chesapeake Biological Laboratory (lat 38.3167N, long 76.4526W) in 2004 and
2005 and Pin Oak (lat 38.4088N, long 76.5218W) in 2004 through 2007. On the
Potomac River, stations were deployed at Piney Point (lat 38.1377N, long 76.5058W)
from 2004 to 2007, near Sage Point (lat 38.1135N, long 76.4285W) in 2004 and 2005
and in St. George Creek (lat 38.1311N, long 76.4934W) in 2006 and 2007. Each sonde
collected water temperature, conductivity, pH, dissolved oxygen, turbidity and
fluorescence data every 15 minutes 0.5 meters above the bottom (Michael et al. 2008).
Non-parametric ANOVAs (Kruskal-Wallis) were performed on temporal water quality
data (April-October) to assess differences in locations for each year (2004-2007).
The data generated from the sondes and shipboard GPS were mapped in ArcGIS
(ESRI, Redlands, CA) for each monthly cruise. The data were then interpolated using the
Inverse Distance Weighted method to create a grid with a pixel dimension of 50 meters.
Mean grids for each parameter were generated for each river and overlaid with the seed
dispersal plot grids to yield water quality conditions directly above the restoration sites.
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Cost analyses
To compare the cost effectiveness of each dispersal method, the total cost of the
particular method was divided by the total number of viable seeds dispersed using that
method for each year of the project (2004-2008).
The total cost for seeding one acre was then calculated by multiplying the cost per
seed by the specified seeding density (200,000 seeds/acre). When determining the total
cost for each method, all costs associated with seed collection, processing, storage and
dispersal, such as staff and volunteer labor, harvesting equipment costs and expendable
supplies were included. However, these costs do not include additional one-time
equipment purchases, utilities, project management or monitoring.
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Results
Study Area
Five sites on the Patuxent River and five sites on the St. Marys River (Potomac River)
were identified as suitable habitats for eelgrass restoration activities between 2003 and
2008. All restoration efforts for this project took place on the Patuxent River between
2004 and 2006. However, due to the lack of success of seeding efforts as well as limited
bottom area for seeding, restoration efforts shifted to two of five previously identified
restoration locations on the Potomac River, St. George Island and Cherryfield Point from
2006 to 2008. For full comparison, data from all years on both rivers were included in
this report for analysis.
Eelgrass Seed Collection Comparison
The total volume of eelgrass reproductive material collected from 2003-2008 was
414,803 L. Annual collection rates were highly variable and dependent on collection
time and method (Table1). Collection rates ranged from 392 L/day in 2006 to 22,720
L/day in 2005, with a mean annual collection rate of 9,483 L/day. The mean mechanical
collection rate (9,529 L/day) was also six times greater than the mean manual collection
rate (1,515 L/day).
Eelgrass Seed Processing and Storage
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material collected, as well as the proportion of eelgrass reproductive material utilized in
spring seed bag dispersal and other restoration projects. The mean percentage of viable
eelgrass seeds remaining in the fall after processing and storage procedures was 35%
with a range of 7-87% (Table 1).
Eelgrass Seed Dispersal Methods Comparison
A total of 13,498,000 eelgrass seeds were dispersed from 2003 to 2008, with a
mean of 1,687,250 seeds each year of the project (Table 1). The portion of eelgrass seeds
dispersed through each method varied by year and was dependent on; 1)amount of
reproductive material collected 2)available shoal area for spring seed bag deployment and
3)amount of tank volume at the processing and storage facility. During the six years of
this project, one third of the eelgrass seeds were dispersed via the fall broadcast method
and the remaining two thirds were dispersed utilizing the spring seed bag method.
Eelgrass Monitoring and Analysis
Adult plant monitoring
All adult test plantings on the Patuxent River died within one year of planting
(Figure 7). Plantings at several sites on the Potomac River survived several years
including those planted in at St. George Island in 2004 and 2005 and at Cherryfield Point
in 2006. With the exception of a few signs of disruption, such as that of a ray, most adult
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planting and 10% twelve months after transplant. While there were significant
differences in adult transplant survival among sites one month and six months after
planting, adult transplant survival at twelve months was statistically similar (Tables 2 and
3). Transplant survival was significantly different between rivers twelve months after
transplant as no planting units were observed on the Patuxent River (Tables 2 and 3).
However, mean transplant survival at twelve months was 26% and 17% at St. George
Island and Cherryfield Point, respectively.
Seed plot monitoring
Eelgrass seeds were dispersed on the Potomac and Patuxent Rivers between 2003
and 2008. All seeding on the Patuxent River and 2006-2008 seeding on the Potomac
River were funded through this project. A total of 13,498,000 seeds were dispersed using
2 seeding methods in 41 discrete planting areas at 10 different locations, five on each
river (Tables 4 and 5).
Eelgrass seedlings were observed in a majority (69%) of the plots during initial
monitoring in the spring following seed dispersal. Seedling establishment, or the
percentage of seeds observed as seedlings, in restoration plots was highly variable and
ranged from 0 to 3.7% depending on site, dispersal method and year (Table 6).
Establishment was generally 1.5 times higher in fall seed broadcast plots than in spring
seed bag plots and twice as high for areas dispersed in 2007 than those dispersed in
previous years (Table 7). While seedling establishment was roughly equivalent for both
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Patterson Park on the Patuxent River. Several sites (Piney Point and Solomons Island)
had no observed seedling establishment regardless of dispersal method.
Eelgrass shoot density varied significantly with time, with increases in shoot
density observed during early summer monitoring, followed by decreased densities
observed in the fall (Figure 8). Shoot density was significantly higher in fall seed
dispersal plots than in spring seed bag plots (Table 8, Figure 8A). Density was also
significant for dispersal year (Table 8, Figure 8B). Both dispersal method and year had
significant interactions with time (Table 8). Univariate ANOVAs showed no significant
differences in eelgrass shoot density between dispersal method and year during initial
spring monitoring or fall monitoring (Table 9). However, eelgrass densities were
significantly different for dispersal method and year during summer monitoring (Table 9,
Figure 8A & Figure 8B).
Observed eelgrass density generally declined over the course of the first year of
monitoring (Tables 7 & 10). Mean plant survival, or the percentage of initial seedlings
observed as plants after one year, was higher on the Potomac River (37 60%) than on
the Patuxent River (0 0%). Plant survival was generally twice as high in fall seed
broadcast plots (36 54%) than in spring seed bag plots (15 49%) and higher in 2006,
compared to other dispersal years six months after initial monitoring.
Mean long-term survival (plants observed in the fall of 2008 as a percentage of
initial seedlings) was also greater on the Potomac (338 750%) than on Patuxent River
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Long-term survival was 0% at all sites except for St. George Island and Cherryfield Point
on the Potomac River, where the mean percent increase in eelgrass shoot density was 559
and 89%, respectively (Table 11).
Habitat Monitoring and Statistical Analyses
Two YSI 6600 EDS sondes on the Patuxent River and three sondes on the
Potomac River were deployed during the monitoring period (2004-2007) to provide
temporally intensive habitat assessments of adjacent restoration study sites throughout the
SAV growing season (April-October). All temporal data (water temperature, salinity,
dissolved oxygen, pH, fluorescence and turbidity) collected by the YSI 6600 EDS sondes
were highly significant among monitors for each year of the project (Table 12).
Temporal data including minimum daily dissolved oxygen, maximum daily water
temperature, maximum daily turbidity and maximum daily chlorophyll at each of the five
stations are presented in Appendix A and discussed further in the discussion. Cumulative
frequency analysis of turbidity, chlorophyll, dissolved oxygen and temperature values
was performed and is graphically presented in Appendix B and discussed in the
discussion.
Spatially intensive water quality monitoring was conducted monthly during the
eelgrass growing season (March - November) throughout the lower mesohaline portion of
the Patuxent River from 2004 to 2006 and the lower mesohaline Potomac River (St.
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salinity values were significantly higher (t.05[1]
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Discussion
Harvesting of eelgrass seeds for restoration has traditionally involved hand
collection using SCUBA or snorkeling (Granger et al. 2002; Orth et al. 2006a). While
this can be effective for small-scale restoration, innovative techniques for enhanced seed
collection were needed in order to conduct eelgrass restoration on a larger (multi-acre)
scale. Eelgrass reproductive material collection was increased from approximately
22,796 L in 2003 using manual harvesting to approximately 89,918 and 204,482 L in
2004 and 2005, respectively. This was due primarily to the use of a mechanical harvester
in 2004 and 2005. The volume of material collected in 2006 decreased greatly due to
masseelgrassmortality in the late summer of 2005 (R. Orth 2005, Virginia Institute of
Marine Science, Gloucester Pt., VA, personal communication)., equipment problems and
adverse weather conditions. However, mechanical collection volumes and rates
improved in 2007 and 2008.
While manual collection allowed for a less destructive selection of eelgrass
reproductive material, the amount of material and the per man-hour collection rates were
unable to in provide enough eelgrass seeds for large-scale restoration. Mechanical
harvesting dramatically improved material collection rates and volumes. However, this
method was more expensive, logistically more difficult and is less selective in the plant
material collected. A greater amount of non-reproductive plant material is collected due
to the inefficient design of the harvesters cutting mechanism.
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mat and lower vegetative parts of the eelgrass plants. Harvesting also took place over a
large area (several acres) to assure that sufficient seeds remained for the maintenance of
the donor beds.
Following mechanical harvest, replicate haphazard 1m2 quadrats were surveyed in
harvested and adjacent unharvested areas to compare shoot height and density between
donor beds and nearby control beds. No substantial differences in plant height, shoot
density, or apparent vigor of the plants themselves existed between the harvested and
unharvested beds. In addition, low level (1:24,000) aerial photography taken shortly after
seed collection confirmed that the areas that were harvested in May were still densely
vegetated (MD DNR unpublished).
The lack of eelgrassseed physiology research made storing large numbers of
seeds under man-made conditions for 4-6 months very difficult. Seed viability was
greatly increased by changes made to storage conditions and procedures over the course
of the study. After much trial and error, it was ultimately determined that seeds stored at
18oC and 18-20 psu in filtered water resulted in the highest numbers of viable seeds. The
continued research and modification of seed storage protocols led to a drastic increase in
seed viability and subsequent increased quantities of seeds available for broadcast. This
dramatically affected the costs associated with this method over the years.
While fall seed broadcasting was more expensive, there are several advantages to
this method. Because eelgrass seeds are negatively buoyant they settle to the sediment
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germinate shortly after being dispersed. Since seeds germinate soon after dispersal, seed
predation, removal from the system through transport to unsuitable habitat areas and deep
burial are less likely. Seeds broadcast in the fall require less manpower than those
dispersed in the spring. Fall seed broadcast was simplified in 2006 using a manual seed
broadcasting system as we realized that the calibration of the mechanical seed sprayer
took more time than it saved.
A buoy-deployed seeding system (BuDSS) developed by Pickerell et al. (2005;
2006) was modified slightly and used as an alternative method to broadcast seeding in the
fall. Immediate deployment of reproductive material in the spring eliminates summer
seed storage, reducing the number of seeds lost to processing and decreasing the expense
and labor requirements associated with seed transport, processing, and storage.
Alleviating long-term seed storage can be a significant advantage if the infrastructure is
not present to house a seed storage operation thus reducing major capital investment and
therefore project costs.
There are several limitations to the spring seed bag dispersal method. While this
method mimics the floating and rafting of reproductive shoots during the natural
phenological schedule (Pickerel et al. 2005), seeds dispersed in the spring will remain in
the sediment for 4-5 months before germinating in mid-October when water temperatures
drop below 15oC (Moore et al. 1993). During this time, seeds are susceptible to
predation, deep burial, or transport out of the suitable growing area. Some species feed
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2004, only 7% of seeds collected were available for dispersal leading to significantly
higher costs than in 2005 when a larger seed harvest combined with 20% seed viability
resulted in much lower costs. Despite increased seed viabilities in 2006 and 2007 (87 and
21%, respectively), less significant seed harvest and a significant investment in supplies
to refine the seed processing and storage process resulted in much higher fall costs. In
2008, a similar number of seeds were harvested as in 2007, however, a 60% seed viability
after storage coupled with a decrease in supply costs to store seeds for the summer
resulted in a significant decrease in costs. Overall, the disparity in the cost per seed was
due to a combination of variations in the seed yield from collection and seed viability
after summer storage. In years with abundant seed harvest (>10 million seeds) and
optimal seed viability after summer storage (>20%), large-scale eelgrass seeding costs
can occur at reasonable costs ($2,702/acre, spring seed bags and $17,009/acre, fall seed
broadcast).
Observed eelgrass seedling establishment was highly variable, ranging from 0 to
3.7% of seeds dispersed. Germination rates in this study fell within range of previously
reported seedling establishment for natural eelgrass populations (< 10%) (Harrison 1993)
and in eelgrass seed restoration studies in the Chesapeake Bay region (0.6-39.8%) (Orth
et al. 1994, 2003, 2006a, 2006b, 2008b; Harwell & Orth 1999; Orth & Marion 2007).
Eelgrass seedling establishments ranging from 5 to 15% have been reported for the
Delmarva Coastal Bays, VA (Orth et al. 2006b), the Peconic Estuary, NY (Pickerell et al.
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of the project as seed dispersal efforts were concentrated in sites with previous seedling
establishment and survival. This suggests that site selection is a vital component of
eelgrass restoration as seedlings were never observed at two sites (Piney Point and
Solomons Island), others sites (Cherryfield Point, Hungerford Creek, Myrtle Point,
Parrans Hollow, Sage Point and Kitts Point) had mixed success and two sites (St. George
Island and Jefferson Patterson Park) consistently had eelgrass seedlings establish.
While the spring seed bag method had a greater number of plots with seedling
germination, the mean establishment percentage of those plots was two times less than in
plots dispersed with seeds in the fall. While not statistically significant, the differences in
seedling establishment between seed dispersal methods suggest that eelgrass seeds
dispersed in the spring may be more susceptible to biotic and abiotic conditions prior to
germination. Eelgrass seeds utilized in the spring seed bag method are dispersed in late
May or early June and can remain in the sediment for up to six months before
environmental conditions (water temperature and sediment redox potential) cue
germination (Moore et al. 1993). Seeds are susceptible to predation (Wigand & Churchill
1988; Fishman & Orth 1996), entrapment by benthic invertebrates (Luckenbach & Orth
1999), deep burial (Bigley 1981; Churchill 1992), or transport out of the suitable growing
area due to near-bottom currents (Orth et al. 1994; Harwell & Orth 1999) before the
required conditions for germination are met.
However, eelgrass in spring seed bag plots persisted for as long as plants in fall
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seed bag deployments. Eelgrass at sites with average seedling establishment also
persisted for roughly the same, in some cases longer, periods of time when compared to
sites with relatively high seedling establishment. These observations suggest that
eelgrass persistence in restoration plots is not solely dependent on initial seedling
establishment or seed dispersal method.
Mean observed eelgrass shoot density was higher during the summer (July) than
in the fall (October). Shoot densities increased from the spring (April) monitoring to
summer (July) monitoring period, and then declined to below-spring densities in the fall
(October). The fluctuation of plant density over time was typical of eelgrass populations
in the Chesapeake Bay. Orth & Moore (1986) reported maximum eelgrass shoot
densities in June and July, minimum values in September following a summer defoliation
and the emergence of new shoots in October with shoot production continuing through
the winter and spring. Light limitation and temperature stress are thought to be the main
contributors to the late summer reductions in eelgrass shoot density (Evans et al. 1986;
Orth & Moore 1986; Moore et al. 1996).
Many of the seedlings were also clumped in groups and field observations
indicated that eelgrass plants were interspersed with areas of bare bottom. Therefore, our
reported mean plant densities include areas of higher density plants and unvegetated
areas. Observations from other studies have also reported similar seedling clumping
(Orth et al. 2003, 2008b). While densities of eelgrass in our restoration plots were
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shoot densities were comparable to eelgrass restoration areas in the lower York River,
VA (Orth & Marion 2007).
The consistent loss of eelgrass in restoration sites during the summer (July-
August) suggests that this is a critical time period for eelgrass survival. While eelgrass
was not observed in some plots the first summer and fall monitoring periods, plants were
seen in these areas during spring and summer monitoring in subsequent years.
Regardless of year, defoliation occurred during the summer (July-August). Additionally,
a summer die-off of eelgrass in summer of 2005 (Moore & Jarvis 2008) caused baywide
declines in natural populations, and the impact of this die-off can be seen in our
monitoring results. Adult transplants planted in the fall of 2004 only survived the 2005
summer conditions at St. George Island. Eelgrass plants grown from seeds dispersed in
2005 (germinated after summer die-off) were 38 times denser than plants established in
2004 (germinated prior to summer die-off), suggesting that the 2005 summer conditions
had major impacts on plant densities in our restoration sites.
Our results demonstrate that adult transplant survival is indicative of the survival
of eelgrass grown from seed in restoration areas. Sites where transplants persisted longer
than 12 months also had long-term survival of eelgrass plants grown from seed. The
percentage of surviving transplants declined over time and only two sites on the Potomac
River had transplants survive past one year. Eelgrass plants transplanted in 2005 and
2006 at Cherryfield Point persisted 20 (33% survival) and 19 months (10% survival),
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Island site persisted 31 months, with survival of 1.5% and 33%, respectively. No
planting units were observed during the following fall monitoring period (24 or 36
months after transplant) for either location. Additional monthly monitoring during the
summer of 2005 and 2006 (May-September) revealed that transplant density decreased
drastically between July and August and above-ground biomass was absent by September
or October, indicating that the summer conditions affecting seedling survival also impact
adult transplant survival as well.
The lack of long-term survival of eelgrass on the Patuxent River and the
consistent defoliation of eelgrass during the summer suggests that eelgrass survival is
dependent on site-and season-specific environmental conditions not utilized in the initial
restoration site selection process. Water temperatures greater than 25oC (Rasmussen
1977; Nejrup & Pedersen 2008) can stress eelgrass, and when temperatures exceed 30oC,
eelgrass die-backs have been reported (Orth & Moore 1986; Moore & Jarvis 2008). High
water temperatures can disrupt eelgrass photosynthetic and metabolic processes (Evans et
al. 1986; Marsh et al. 1986; Zimmerman et al. 1989; Nejrup & Pedersen 2008). High
temperatures and decreased photosynthetic rates also affect the internal oxygen balance
of eelgrass (Greve et al. 2003), leading to sulfide intrusion of the rhizome and
meristematic tissues (Pederson et al. 2004) and increases in anaerobic metabolites
(Pregnall et al. 1984; Smith et al. 1988), ultimately affecting eelgrass photosynthetic
rates, growth and survival (Goodman et al. 1993; Holmer & Bondgaard 2001). Several
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It is possible that similar stressful conditions (high temperatures and low
dissolved oxygen) contributed to the observed summer eelgrass declines in our
restoration sites. Summer (July-August) water temperatures exceeded 30oC more
frequently on the Patuxent River in all years of the project. Annual differences in the
frequency of extreme water quality conditions were also evident during the four years of
the project, particularly during the summer of 2005. On the Patuxent River, water
temperatures exceeded 30oC 27% of the time during July and August of 2005, with a
maximum temperature of 35C. Water temperatures reached 32C in the summer of
2005 on the Potomac River and exceeded 30C 22% of the time. Dissolved oxygen
concentrations below 2.5 mg/L were observed 2% of the time on both rivers during the
summer of 2005. The frequency of high temperature events was greatly reduced in all
other years of the project. Frequent drops in dissolved oxygen were measured on the
Potomac River in 2006, however, these observations were collected from one monitor
adjacent to a restoration site with similar summer eelgrass declines, suggesting that
periods of low summer dissolved oxygen affected eelgrass survival. Moore and Jarvis
(2008) reported similar vegetative eelgrass die-offs and increases in the frequency of
extreme environmental stressors during the same timeframe of our project. Concurrent
losses of eelgrass in our restoration plots suggest that even short-term exposure to the
combination of multiple stressors can severely hinder eelgrass restoration, regardless of
previous restoration success.
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and plant densities than with the spring seed buoy method, and should be utilized if
funding and facilities exist for long-term seed storage. Because restoration site selection
is critical, refinement of SAV habitat criteria for restored populations ofZ. marina is
needed. More research on how habitat criteria differ for restored eelgrass in relation to
established populations, and the inclusion of additional parameters, such as sediment
characteristics and wave exposure, are necessary in order to enhance restoration site
selection. The role of long-term trends and regional events or extremes in SAV habitat
conditions must be considered in restoration projects. Monitoring frequency and scale
should be considered when planning restoration projects as it is crucial to provide
sufficient resolution in order to explain observed changes in Z. marina shoot density and
long-term survival. The ecological function of restoredZ. marina beds should be
considered when defining restoration success.
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Holmer, M. and E. J. Bondgaard. 2001. Photosynthetic and growth response of eelgrass
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macrophyte: implications for colonization and restoration. Ecology 75:1927-1939.
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transplanting eelgrass using single, unanchored shoots. Aquatic Botany 64:77-85.
Orth, R. J., M. C. Harwell, E. M. Bailey, A. Bartholomew, J. T. Jawad, A. V. Lombana,
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SAV-06-2. U.S. Army Corps of Engineers, Vicksburg, MS. Available from:
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recolonisation after anoxia-induced full mortality. Aquatic Botany 77:121-134.
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ofZostera marina (eelgrass) to diurnal periods of root anoxia. Marine Biology 83: 141-
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Figure 3.Zostera marina seed collection locations (2003-2008) and the Piney Point
Aquaculture Facility, St. Marys County, Maryland where seed processing, sorting and
storage took place.
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Figure 4. Mechanical harvest machine used for collection ofZostera marina seeds
(Pristine Marine, M J McCook & Associates, La Plata, MD).
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Figure 5. Mechanical seed spraying apparatus (C& K Lord, Inc.) used for fall seed
dispersal. Seeds were broadcast using the sprayer in 2004 and 2005. Subsequent
broadcasts were accomplished using manual dispersal due to the large amount of time
needed to utilize the seed sprayer.
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Figure 6. A) Maryland Department of Natural Resources staff assembling spring seed
bags, B) Spring seed bag with attached cinderblock, C) Spring seed bag deployment, and
D) Spring seed bag floating freely after deployment.
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0
20
40
60
80
100
Oct
Feb
Jun
Oct
Feb
Jun
Oct
Feb
Jun
Oct
Feb
Jun
Oct
PercentSurviva
l CP-04
SP-04
SGI-04
CP-05
SP-05
SGI-05
SGI-06
SGI-S-06
CP-06
A2005 2006 2007 2008
0
20
40
60
80
100
Oct
Jan
Apr
Jul
Oct
Jan
Apr
Jul
Oct
Jan
Apr
Jul
PercentSurvival
HC-04
PH-04
SI-04
HC-05
MP-05
PH-05
PH-06
2005 2006 2007 B
Figure 7. Mean percent survival of adult test plantings. A) Potomac River: CP
Cherryfield Point, SP Sage Point, SGI St. George Island, SGI-S St. George Island
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0
0.5
1
1.5
2
2.5
Sp 05 Su 05 Fa 05 Sp 06 Su 06 Fa 06 Sp 07 Su 07 Fa 07 Sp 08 Su 08 Fa 08
Time
mean
shootdensity(shootsm-2)
Fall Broadcast
Spring Seed Bag
A
0.5
1
1.5
2
2.5
3
3.5
4
4.5
mea
nshootdensity(shootsm-2)
2004
2005
2006
2007
B
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0
0.5
1
1.5
2
2.5
Sp 05 Su 05 Fa 05 Sp 06 Su 06 Fa 06 Sp 07 Su 07 Fa 07 Sp 08 Su 08 Fa 08
meanshootdensity(shootsm-2)
Patuxent
Potomac
C
Figure 8. Comparison of meanZ. marina shoot densities observed during monitoring
events throughout the project. A)Z. marina shoot densities by seed dispersal method (fall
broadcast and spring seed bag) B)Z. marina shoot densities by seed dispersal year (2004-
2007) C)Z. marina shoot densities by river (Patuxent and Potomac). The number of
plots monitored increased each year (n = 16, 29, 33 and 36 for 2005, 2006, 2007 and
2008, respectively) as new seed dispersal plots were established.
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Table 1. Annual comparison ofZostera marina seed collection, processing, storage and dispersal methods.
2003 2004 2005 2006 2007 2008
Collection
Collection method Manual Mechanical Mechanical Manual Mechanical Total Mechanical Mechanical
No. of collection days 8 9 9 8 4 10 7 6
Z. marina yield (L) 22796 89918 204482 1451 2467 3918 54510 39179Collection rate (L/day) 2849 9991 22720 181 617 392 7787 6530
Processing and StorageVolume of Z. marina seeds processed (L) N/A 71.9 109.8 32.5 48.8 70.3Viable Z. marina seeds remaining after storage (no. and (% of total)) 345000 (16) 1058400 (7) 2527000 (20) 349888 (87) 540867 (21) 961567 (60)
Dispersal
Seeds dispersed through spring seed bag method (%) 0 92 71 38 6 0
Seeds dispersed through fall broadcast method (%) 100 8 29 62 94 100
52
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Table 4. Compilation of all eelgrass restoration efforts in the Patuxent River by restoration site (2003-2006)
Restoration Site Year Broadcast Method Size (Acres) Number of Seeds Seeds/Acre
Parrans Hollow 2004 Fall Seed Broadcast 0.25 37,500 150,000
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Spring Seed Bag 5 605,000 121,000
1 245,000 245,000
Total Acres Total Number of Seeds 6.25 887,500
Fall Seed Broadcast 0.1 87,500 875,0002006
Spring Seed Bag 0.07 56,000 800,000
2 534,000 267,0002005 Fall Seed Broadcast
3 201,000 67,000
2004 Spring Seed Bag 1 150,000 150,000
2003 Fall Seed Broadcast 3 300,000 100,000
Total Acres Total Number of Seeds
9.17 1,328,500
Jefferson Patterson Park
Hungerford Creek 2005 Fall Seed Broadcast 2 534,000 267,000
2004 Fall Seed Broadcast 0.25 37,500 150,000
Total Acres Total Number of Seeds
2.25 571,500
Myrtle Point 2005 Fall Seed Broadcast 0.5 133,500 267,000
2004 Spring Seed Bag 2.5 300,000 120,000
Total Acres Total Number of Seeds
3 433,500
Solomons Island 2004 Fall Seed Broadcast 0.25 37,500 150,000Spring Seed Bag 5 605,000 212,000
Total Acres Total Number of Seeds
5.25 642,500
Total Acres Total Number of SeedsGrand totals of seeding on Patuxent River as of 2006
25.92 3,863,500
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Table 5. Compilation of all eelgrass restoration efforts in the Potomac River by restoration site (2003-2008)
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55
p g y ( )
Restoration Site Year Broadcast Method Size (Acres) Number of Seeds Seeds/Acre
Piney Point 2004 Fall Seed Broadcast 0.50 150,000 300,000
2003 Fall Seed Broadcast 3.00 300,000 100,000
Total Acres Total Number of Seeds
3.50 450,000
1.0 400,000 400,000
0.67 134,000 200,000
2008 Fall Seed Broadcast
0.66 132,000 200,000
Fall Seed Broadcast 1.0 270,000 270,0002007Spring Seed Bag 0.34 35,000 105,000
Fall Seed Broadcast 0.25 262,000 1,050,0002006
Spring Seed Bag 0.2 160,000 800,000
Spring Seed Bag 1.25 275,000 220,0002005
Fall Seed Broadcast 1.00 200,000 200,000
Spring Seed Bag 5.00 605,000 121,0002004
Fall Seed Broadcast 0.25 75,000 300,000Total Acres Total Number of Seeds
11.62 2,548,000
St. George Island
2008 Fall Seed Broadcast 0.67 134,000 200,000
2007 Fall Seed Broadcast 1.0 270,000 270,000
Spring Seed Bag 2.50 1,210,000 484,0002005
Fall Seed Broadcast 0.50 100,000 200,000
2.50 275,000 110,000Spring Seed Bag
2.50 275,000 110,000
2004
Fall Seed Broadcast 0.25 37,500 150,000
Total Acres Total Number of Seeds
9.92 2,301,500
Cherryfield Point
Sage Point 5.00 605,000 121,0002004 Spring Seed Bag
5.00 605,000 121,000
Total Acres Total Number of Seeds
10.00 1,210,000
Kitts Point 2005 Fall Seed Broadcast 0.50 100,000 200,000
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Kitts Point 2005 Fall Seed Broadcast 0.50 100,000 200,000
2.50 605,000 242,000
2.50 1,210,000 484,000
Spring Seed Bag
2.50 1,210,000 484,000Total Acres Total Number of Seeds
8.00 3,125,000
Total Acres Total Number of SeedsGrand totals of seeding on Potomac River as of 2008
43.04 9,634,500
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Table 6. Mean eelgrass seeds observed as seedlings (% SD) at each restoration site.
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g g
Dispersal Year and Method2004 2005 2006 2007
River Site
Spring
Seed Bag
Fall
Seed
Broadcast
Spring
Seed Bag
Fall
Seed
Broadcast
Spring
Seed Bag
Fall
Seed
Broadcast
Spring
Seed Bag
Fall
Seed
Broadcast
Patuxent Hungerford Creek 0 0.3
Jefferson Patterson Park 0.1 0.1 0 2.8+0.3 0.2
Myrtle Point 0.03 0
Parrans Hollow 0.08 0 0
Solomons Island 0 0
Potomac Cherryfield Point 0.2+0.3 0 0 0 0
Kitt's Point 0.03+.2
0.06 0
Piney Point 0Sage Point 0.3+0.2
St. George Island 0.5 0.2 2.6 1.1 0.2 0.9 3.7 1.7
Table 7. Summary of mean ( SD) eelgrass seedling establishment, first year survival and long-term
survival for River, Dispersal method, and Dispersal year. First year survival is calculated as the
percentage of initial seedlings observed as shoots after one year of monitoring. Long-term survival is
calculated as the mean number of shoots observed as a percentage of initial seedlings established.
Variable
meanseedling
establishment
mean1st yearsurvival
meanlong-termsurvival
RiverPatuxent 0.611.1 00 00Potomac 0.600.97 3760 338750
Dispersal MethodSpring Seed Bag 0.461.0 1549 42108
Table 8. Results of repeated measures ANOVAs testing the effects of seed dispersal year and method
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on eelgrass shoot density over three monitoring events (spring, summer, fall).
Variable Num df/Den df F pYear 3/32 3.49 0.0268Time 2/60 3.90 0.0256
Year * Time 5/60 4.07 0.0030
Method 1/34 4.48 0.0417
Time 2/63 6.58 0.0025Method*Time 2/63 4.71 0.0124
Table 9. Univariate ANOVA results at each monitoring period for seed dispersal year and method
following a significant interaction with time.
Time(Monitoring Period) Variable df effect MS effect df error MS error F p
spring Year 3 0.5161 5.4683 0.1326 3.03 0.1232summer Year 2 18.6793 7.2759 3.6765 10.36 0.0074fall Year 3 0.0598 5.4557 0.0284 1.75 0.2640
spring Method 1 0.2098 26.479 0.1661 1.21 0.2808summer Method 1 18.4669 16.538 4.1674 4.19 0.0569fall Method 1 0.0083 32.660 0.0318 0.26 0.6117
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Table 12. Results of Kruskal-Wallis ANOVAs for temporal water quality measurements for each year
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of the project (April-October).
Year Variable H statistic DF p
2004 Temperature 6607 3
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Totalannual
costs
No. of viableseeds
dispersed
Cost perseed
dispersed
Costper
Acre
Spring seed bag
2004 $48,194 2,155,000 $0.02 $4,473
2005 $30,464 2,255,000 $0.01 $2,702
2006 $21,413 108000 $0.20 $39,654
2007 $2,850 17500 $0.16 $32,571
Fall seedbroadcast2004 $125,616 374,500 $0.34 $67,085
2005 $153,294 1,802,500 $0.09 $17,009
2006 $110,056 349,500 $0.31 $62,979
2007 $142,718 540,000 $0.26 $52,859
2008 $117,708 961,567 $0.12 $24,483
A seeding density of 200,000 seeds per acre was used to calculate annual costs per acre.
APPENDIX A Continuous Monitor Data
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0
2
4
6
8
10
12
14
4/1 4/15 4/29 5/13 5/27 6/10 6/24 7/8 7/22 8/5 8/19 9/2 9/16 9/30 10/14 10/28
dailyminimumd
iss
olvedoxygen(g/L)
2004
2005
2006
2007
A
4
6
8
10
12
14
Dailyminimumd
issolvedoxygen(g/L)
2004
2005
B
14
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0
2
4
6
8
10
12
4/1 4/15 4/29 5/13 5/27 6/10 6/24 7/8 7/22 8/5 8/19 9/2 9/16 9/30 10/14 10/28
dailyminimum
dissolvedoxygen(g/L)
2004
2005
A
4
6
8
10
12
14
dailyminim
umd
issolvedoxygen(g/L)
2004
2005
2006
2007
B
14
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0
2
4
6
8
10
12
4/1 4/15 4/29 5/13 5/27 6/10 6/24 7/8 7/22 8/5 8/19 9/2 9/16 9/30 10/14 10/28
dailyminimumd
issolvedoxygen(mg/L)
2006
2007
C
Figure 2. Daily minimum dissolved oxygen levels at continuous monitor stations A)Sage Point B) Piney Point and C) St. George Creek on the Potomac River throughout theproject.
35
A
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0
5
10
15
20
25
30
4/1 4/15 4/29 5/13 5/27 6/10 6/24 7/8 7/22 8/5 8/19 9/2 9/16 9/30 10/14 10/28
Dailymaximumwatertemperature(degreesC)
2004
2005
2006
2007
A
10
15
20
25
30
35
Dailymaximu
mwatertemperature(degreesC)
2004
2005
B
35
A
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0
5
10
15
20
25
30
4/1 4/15 4/29 5/13 5/27 6/10 6/24 7/8 7/22 8/5 8/19 9/2 9/16 9/30 10/14 10/28
Dailymaximumwatertemperature(degreesC)
2004
2005
A
10
15
20
25
30
35
Dailymaximu
mwatertemperature(degreesC)
2004
2005
2006
2007
B
35
C
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0
5
10
15
20
25
30
4/1 4/15 4/29 5/13 5/27 6/10 6/24 7/8 7/22 8/5 8/19 9/2 9/16 9/30 10/14 10/28
Dailymaximumwatertemperature(degreesC)
2006
2007
C
Figure 4. Daily maximum water temperatures at continuous monitor stations A) SagePoint B) Piney Point and C) St. George Creek on the Potomac River throughout theproject.
150
A
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0
25
50
75
100
125
4/1 4/15 4/29 5/13 5/27 6/10 6/24 7/8 7/22 8/5 8/19 9/2 9/16 9/30 10/14 10/28
Dailymaximumturbidity(NTU)
2004
2005
2006
2007
A
10
15
20
25
30
35
40
45
50
Daily
maximumturbidity(NTU)
2004
2005
B
150
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0
25
50
75
100
125
4/1 4/15 4/29 5/13 5/27 6/10 6/24 7/8 7/22 8/5 8/19 9/2 9/16 9/30 10/14 10/28
Dailymax
imumturbidity(NTU)
2004
2005
25
50
75
100
125
150
Daily
maximumturbidity(NTU)
2004
2005
2006
2007
B
100
C
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0
10
20
30
40
50
60
70
80
90
4/1 4/15 4/29 5/13 5/27 6/10 6/24 7/8 7/22 8/5 8/19 9/2 9/16 9/30 10/14 10/28
Dailymax
imumturbidity(NTU)
2006
2007
Figure 6. Daily maximum turbidity at continuous monitor stations A) Sage Point B)Piney Point and C) St. George Creek on the Potomac River throughout the project.
250
A
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0
25
50
75
100
125
150
175
200
225
4/1 4/15 4/29 5/13 5/27 6/10 6/24 7/8 7/22 8/5 8/19 9/2 9/16 9/30 10/14 10/28
Dailymaxim
umc
hlorophyll(g/L)
2004
2005
2006
2007
50
75
100
125
150
175
Dailym
aximumc
hlorophyll(g/L)
2004
2005
B
150
A
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0
25
50
75
100
125
4/1 4/15 4/29 5/13 5/27 6/10 6/24 7/8 7/22 8/5 8/19 9/2 9/16 9/30 10/14 10/28
Dailymaxim
umc
hlorophyll(g/L)
2004
2005
50
75
100
125
150
175
Dailym
aximumc
hlorophyll(g/L)
2004
2005
2006
2007
B
125
C
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0
25
50
75
100
4/1 4/15 4/29 5/13 5/27 6/10 6/24 7/8 7/22 8/5 8/19 9/2 9/16 9/30 10/14 10/28
Dailymaxim
umc
hlorophyll(g/L)
2006
2007
Figure 8. Daily maximum chlorophyll at continuous monitor stations A) Sage Point B)Piney Point and C) St. George Creek on the Potomac River throughout the project.
APPENDIX B Cumulative Frequency Data (Derived from Continuous Monitor data)
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A B
C D
Figure 1. Cumulative frequency distribution of A) turbidity, B) chlorophyll, C) dissolved oxygen and D) temperaturerecorded at the Pin Oak continuous monitor station between July 1 to August 31 from 2004 to 2007.
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Figure 2. Cumulative frequency distribution of A) turbidity, B) chlorophyll, C) dissolved oxygen and D) temperaturerecorded at the Chesapeake Biological Laboratory continuous monitor station between July 1 to August 31 from 2004to 2005.
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Figure 3. Cumulative frequency distribution of A) turbidity, B) chlorophyll, C) dissolved oxygen and D) temperaturerecorded at the Piney Point continuous monitor station between July 1 to August 31 from 2004 to 2007.
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Figure 4. Cumulative frequency distribution of A) turbidity, B) chlorophyll, C) dissolved oxygen and D) temperaturerecorded at the Sage Point continuous monitor station between July 1 to August 31 from 2004 to 2005.
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Figure5. Cumulative frequency distribution of A) turbidity, B) chlorophyll, C) dissolved oxygen and D) temperaturerecorded at the St. George Creek continuous monitor station between July 1 to August 31 from 2006 to 2007.
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APPENDIX C Dataflow Data
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April May
12.5 +
10 - 12.5
7.5 - 10
5 - 7.5
2.5 - 5
0 - 2.5
Turbidity (NTU)
June July
August September October
Figure 1. Turbidity data (NTU) from DATAFLOW cruises from April to October 2003 on thePatuxent River.
79
April June JulyMarch May
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12.5 +
10 - 12.5
7.5 - 10
5 - 7.5
2.5 - 5
0 - 2.5
Turbidity (NTU)
y
August September October November
Figure 2. Turbidity data (NTU) from DATAFLOW cruises from March to November 2004 on the PatuxentRiver.
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April May June
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12.5 +
10 - 12.5
7.5 - 10
5 - 7.5
2.5 - 5
0 - 2.5
Turbidity (NTU)July August September
Figure 3. Turbidity data (NTU) from DATAFLOW cruises from April to September 2005on the Patuxent River.
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Figure 4. Turbidity (NTU) data from DATAFLOW cruises from April to November
2006 on the Patuxent River.
82
July August September OctoberJune
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Figure 5. Turbidity data (NTU) from DATAFLOW cruises from June to October 2004 on the
12.5 +
10 - 12.5
7.5 - 10
5 - 7.5
2.5 - 5
0 - 2.5
Turbidity (NTU)Potomac River.
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April May June July
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12.5 +
10 - 12.5
7.5 - 10
5 - 7.5
2.5 - 5
0 - 2.5
Turbidity (NTU)
August September
Figure 6. Turbidity data (NTU) from DATAFLOW cruises from April to September2005 on the Potomac River.
84
April May June July
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12.5 +
10 - 12.5
7.5 - 10
5 - 7.5
2.5 - 5
0 - 2.5
Turbidity (NTU)
August September
Figure 7. Turbidity data (NTU) from DATAFLOW cruises from April to Septemberver.2006 on the Potomac Ri
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April May June July
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August September
12.5 +
10 - 12.5
7.5 - 10
5 - 7.5
2.5 - 5
0 - 2.5
Turbidity (NTU)
Figure 8. Turbidity data (NTU) from DATAFLOW cruises from April to September2007 on the Potomac River.
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