Maryland; Large-Scale Restoration of Eelgrass (Zostera marina) in the Patuxent and Potomac Rivers

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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Bigley, R.E. 1981. The population biology of two intertidal seagrasses,Zostera marina

andRuppia maritima, at Roberts Bank, British Columbia. Thesis. University of British

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Brush, G. S. and F. W. Davis. 1984. Stratigraphic evidence of human disturbance in an

estuary. Quaternary Research 22:91-108.

Brush, G. S. and W. B. Hilgartner. 2000. Paleoecology of submerged macrophytes in the

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Burdick, D.M. and G. A. Kendrick. 2001. Standards for seagrass collection,

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Churchill, A. C. 1992. Growth characteristics ofZostera marina seedlings under

anaerobic conditions. Aquatic Botany. 43:379-392.

Davis , R. C., and F. T. Short. 1997. Restoring eelgrass,Zostera marina L., habitat using


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Evans, A. S., K. L. Webb and P. A. Penhale. 1986. Photosynthetic temperature

acclimation in two coexisting seagrasses,Zostera marina L. andRuppia maritima L.

Aquatic Botany 24:185-197.

Fishman, J. R. and R. J. Orth. 1996. Effects of predation onZostera marina L. seed

abundance. Journal of Experimental Marine Biology and Ecology. 198:11-26.

Fishman, J. R., R. J. Orth, S. Marion and J. Bieri. 2004. A comparative test of

mechanized and manual transplanting of eelgrass,Zostera marina, in Chesapeake Bay.

Restoration Ecology 12:214-219.

Fonseca, M. S., W. J. Kenworthy, and G. W. Thayer. 1982. A low-cost planting

technique for eelgrass (Zostera marina L.). Technical Aid No. 82-6 submitted to U.S.

Army Corps of Engineers Coastal Engineering Research Center. U.S. Army Corps of

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planting in the southeastern United States: methods for accelerating habitat development.

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F M S W J K h d G W Th 1998 G id li f h


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Goodman, J. L., K. A. Moore and W. C. Dennison. 1993. Photosynthetic responses of

eelgrass (Zostera marina L.) to light and sediment sulfide in a shallow barrier island

lagoon. Aquatic Botany 50:37-47.

Granger, S., M. Traber, S.W. Nixon and R. Keyes. 2002. Part 1. Collection, processing

and storage. Pages 1-20 in M. Schwartz, editor. A practical guide for the use of seeds

in eelgrass (Zostera marina L.) restoration. Rhode Island Sea Grant, Narragansett R.I.

Greve, T. M, J. Borum and O. Pedersen. 2003. Meristematic oxygen variability in

eelgrass (Zostera marina). Limnology and Oceanography 48:210-216.

Greve, T. M., D. Krause-Jensen, M. B. Rasmussen and P. B. Christensen. 2005. Means of

rapid eelgrass (Zostera marina L) recolonisation in former dieback areas. Aquatic Botany

82:143-156.

Haramis, G. M. and V. Carter. l983. Distribution of submersed aquatic macrophytes in

the tidal Potomac River. Aquatic Botany l5:65-79.

Harrison, P. G. 1993. Variations in the demography ofZostera marina andZostera noltii


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Harwell, M.C., and R.J. Orth. 1999. Eelgrass (Zostera marina L.) seed protection for

field experiments and implications for large scale restoration. Aquatic Botany 64:51-61.

Holmer, M. and E. J. Bondgaard. 2001. Photosynthetic and growth response of eelgrass

to low oxygen and high sulfide concentrations during hypoxic events. Aquatic Botany

70:29-38.

Kemp W. M., W. R. Boynton, J. C. Stevenson, R. R. Twilley, and J. C. Means. 1983. The

decline of submerged vascular plants in upper Chesapeake Bay: Summary of results

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Kemp, W. M., P. Bergstrom, E. Koch, L. Murray, J. C. Stevenson, R. Bartleson, V.

Carter, N. B. Rybicki, J. M. Landwehr, C. Gallegos, L. Karrh, M. Naylor, D. Wilcox, K.

A. Moore and R. Batiuk. 2004. Habitat requirements for submerged aquatic vegetation

in Chesapeake Bay: water quality, light regime, and physical-chemical factors. Estuaries

27:363-377.

Landwehr, J. M., J. T. Reel, N. B. Rybicki, H. A. Ruhl and V. Carter. 1999. Chesapeake

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Marsh, J. A., W. C. Dennison and R. S. Alberte. 1986. Effects of temperature on

photosynthesis and respiration in eelgrass (Zostera marina L.). Journal of Experimental

Marine Ecology 101:257-267.

Michael, B., M. Trice and C. Trumbauer. 2008. Quality Assurance Project Planfor the

Maryland Department of Natural Resources Chesapeake BayShallow Water Quality

Monitoring Program for the period July 1, 2008 - June 30, 2009.Prepared by Maryland

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Moore, K.A., R. J. Orth, and J. F. Nowak. 1993. Environmental regulation of seed

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Moore, K. A. and J. C. Jarvis. 2008. Environmental factors affecting recent summertime

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Orth, R.J. and K.A. Moore. 1983b. Seed germination and seedling growth ofZostera

marina L. (eelgrass) in the Chesapeake Bay. Aquatic Botany 15:117-131.

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vegetation in Chesapeake Bay: A historical perspective. Estuaries 7:531-540.

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Orth, R. J., M. L. Luckenbach, and K. A. Moore. 1994. Seed dispersal in a marine

macrophyte: implications for colonization and restoration. Ecology 75:1927-1939.

Orth, R. J., M. C. Harwell, and J. R. Fishman. 1999. A rapid and simple method for

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,

K. A. Moore, J. M. Rhode, and H. E. Woods. 2000. A review of issues of seagrass seed

dormancy and germination: implications for conservation and restoration. Marine

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Orth, R. J., J. R. Fishman, M. C. Harwell, and S. R. Marion. 2003. Seed density effects

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Army Corps of Engineers, Vicksburg, MS. Available from:

http://el.erdc.usace.army.mil/elpubs/pdf/sav07-2.pdf
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Agency, Chesapeake Bay Program, Annapolis, MD. Available from:

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Orth, R., S. Marion, S. Granger and M. Traber. 2008b. Restoring eelgrass (Zostera

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SAV-08-1. U.S. Army Corps of Engineers, Vicksburg, Mississippi. Available from:


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Pedersen, O., T. Binzer and J. Borum. 2004. Sulphide intrusion in eelgrass (Zostera
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shelled clams,Mya arenaria, in the lower Potomac River, Maryland. Chesapeake Science

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Pickerell, C. H., S. Schott, and S. Wyllie-Echerverria. 2005. Buoy-deployed seeding:

Demonstration of a new eelgrass (Zostera marina L.) planting method. Ecological

Engineering 25:127-136.

Pickerell, C., S. Schott, and S. Wyllie-Echeverria. 2006. Buoy-deployed seeding: A new

low-cost technique for restoration of submerged aquatic vegetation from seed. ERDC/TN

SAV-06-2. U.S. Army Corps of Engineers, Vicksburg, MS. Available from:


Plus, M., J-M. Deslous-Paoli and F. Dagault. 2003. Seagrass (Zostera marina L.) bed

recolonisation after anoxia-induced full mortality. Aquatic Botany 77:121-134.

Pregnall, A. M., R. D. Smith, T. A. Kursar and R. S. Alberte. 1984. Metabolic adaptation

ofZostera marina (eelgrass) to diurnal periods of root anoxia. Marine Biology 83: 141-

147.
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Shafer, D. J., and P. Bergstrom. 2008. Large-scale submerged aquatic vegetation

restoration in Chesapeake Bay. Status Report 2003-2006. ERDC/EL TR-08-20. U.S.

Army Corps of Engineers, Vicksburg, MS. Available from:

http://el.erdc.usace.army.mil/elpubs/pdf/trel08-20.pdf

Smith, R. D., A. M. Pregnall and R. S. Alberte. 1988. Effects of anaerobiosis on root

metabolism ofZostera marina (eelgrass)-implications for survival in reducing sediments.

Marine Biology 98:131-141.

Traber, M. S., S. Granger and S. Nixon. 2003. Mechanical seeder provides alternative

method for restoring eelgrass habitat (Rhode Island). Ecological Restoration 21:231-214.

Wigand, C. and A. C. Churchill. 1988. Laboratory studies on eelgrass seed and seedling

predation. Estuaries 11(3):180183.

Zimmerman, R. C., R. D. Smith and R. S. Alberte. 1989. Thermal acclimation and whole-

plant carbon balance inZostera marina L. (eelgrass). Journal of Experimental Marine

Ecology 130:93-109.
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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


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


3 433,500

Solomons Island 2004 Fall Seed Broadcast 0.25 37,500 150,000Spring Seed Bag 5 605,000 212,000


5.25 642,500

Total Acres Total Number of SeedsGrand totals of seeding on Patuxent River as of 2006

25.92 3,863,500

54

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



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


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



Spring Seed Bag 2.50 1,210,000 484,0002005


2.50 275,000 110,000Spring Seed Bag

2.50 275,000 110,000

2004



9.92 2,301,500

Cherryfield Point

Sage Point 5.00 605,000 121,0002004 Spring Seed Bag

5.00 605,000 121,000


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

56

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

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4

6

8

10

12

14

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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

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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

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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

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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


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


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

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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.

78

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.

80

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.

81


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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.

83

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

85

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.

86

Documents

Maryland; Large-Scale Restoration of Eelgrass (Zostera marina) in the Patuxent and Potomac Rivers