Virginia Institute of Marine Science
Restoration of Seagrasses in Virginia's Seaside Bays - Year 6
Project Description as Proposed:
Seagrasses, primarily eelgrass, Zostera marina, were once very abundant in Virginia's coastal bays, covering most of the subaqueous bottom. In the 1930s eelgrass underwent a massive decline attributed to a wasting disease pathogen, Labyrinthula sp. The decline was pandemic, affecting not only populations in the coastal bays but also populations on both sides of the Atlantic. In August 1933, this region was affected by one of the most destructive hurricanes to influence the area in the twentieth century, contributing to the decimation of seagrasses in the bays. Natural recovery of seagrasses since that time has been limited primarily to Chincoteague, Sinepuxent, Isle of Wight and Assawoman bays with no recovery in the Virginia coastal bays south of Chincoteague Bay. VIMS ongoing eelgrass seed ecology research has pointed to limited propagule supply as the most likely reason for no eelgrass recovery here. Today, the Virginia coastal bays are primarily salt marsh and macroalgal dominated, although recent efforts at restoring eelgrass in the coastal bays has had remarkable success since 1999. The project objectives for year 6 of the SHP builds upon restoration success of previous years and will continue the large scale efforts at locations deemed suitable for further seed enhancements. The program in Year 6 has six tasks:
1. Monitor success of established seagrass areas (15%)
2. Collect seeds for 2008 restoration efforts (10%)
3. Collect water quality with dataflow in areas with existing eelgrass and adjacent unvegetated areas (45%)
4. Large scale seagrass restoration (20%)
5. Mapping of seagrass from aerial photographs (5%)
6. Preparation of Coastal GEMS data layer and final report (5%)
Tasks 1-5 listed above represent 95% of the budget.
The program in Year 6 has five tasks, building on success of similar tasks in the previous 5 years:
1. MONITOR SUCCESS OF ESTABLISHED SEAGRASS AREAS
The most critical aspect of this project is to monitor both the established seagrass areas planted since 1998. Seagrass plots planted between 1998 and 2006 will be monitored with a combination of on-site field checks and low level remote sensing techniques.
2. COLLECT SEEDS FOR 2008 RESTORATION EFFORTS
Our previous work with harvesting seeds has shown that there is generally a 3-4 week window to harvest mature reproductive shoots with ripe seeds, usually from the first week of May to the first of June. Depending upon flower abundance in 2008, we may continue with hand collections unless flowering shoot densities are high. If so, we would return to using the VIMS mechanical harvester built and deployed for seed harvesting in 2005.
Harvested reproductive shoots are returned to the VIMS laboratory and placed in large seawater holding tanks at the SAV greenhouse. These are monitored for seed release and when completed, seeds are separated from all detritus and plant material and held until the period when seeds are broadcast.
3. COLLECT WATER QUALITY WITH DATAFLOW IN AREAS WITH EXISTING EELGRASS AND ADJACENT UNVEGETATED AREAS.
Our previous developmental work in several Chesapeake Bay tributaries has allowed us to map water quality over large shallow water areas using Dataflow techniques. Discreet measurements are taken at 2-3 second intervals as water is passed through a flow-through measuring chamber while the vessel is traversing the study area. Concurrent with the sensor measurements (including turbidity, chlorophyll fluorescence, temperature, salinity, pH, dissolved oxygen) GPS and depth information are recorded. This information is then analyzed using GIS techniques and data layers of water quality constituents can be quantified and displayed for the vessel path or interpolated for the entire study area. Fixed stations using similar sensor arrays are deployed for two week or longer intervals so that this high frequency spatial record can be integrated with the high frequency temporal record for the region. During 2008 our goal for this task will be to conduct Dataflow cruises at monthly intervals throughout the SAV growing season and to deploy the fixed stations for a minimum of 14-day intervals bi-monthly throughout this same period. This effort will cover all seagrass restored areas in South, Cobb, Spider Crab and Hog Island bays.
4. LARGE SCALE SEAGRASS RESTORATION
Our previous work in the coastal bays between 1999 and 2006 has shown that broadcasting eelgrass seeds has proven to be a very effective technique for restoring eelgrass on larger scales than a few square meters. In 1999 and 2000, experiments were conducted in small plots of 4 and 100 m2 with seed densities ranging from 2.5 to 1250 seeds m-2. In 2001, we broadcast approximately 4.4 million seeds into 36 one-acre plots in South, Cobb and Magothy bays at two seed densities 100,000 and 200,000 per acre (25 and 50 seeds m-2, respectively). In 2002, we broadcast seeds to 24 one acre plots at two seed densities: 50,000 seeds (12.5 seeds m-2) in 12 acres and 100,000 seeds (25 seeds m-2) in 12 acres. In the fall, 2003, we broadcast seeds into 0.5 acre circular plots with seeds placed either in a 1-2 meter ring (the circumference) or in the entire circle. We broadcast seeds into 37 0.5 acre rings (12 filled circles and 25 rings). In 2004, we placed approx 7 million seeds into 35 acres using seed bags with flowering shoots deployed in the spring and broadcast approximately 600,000 seeds into 4 acres in the fall. In 2005, we used the fall broadcast method only and spread 1.5 million seeds in the fall into 22 -0.5 acre plots in Spider Crab and South bays. In 2006 we established 28 plots in Hog Island Bay, each covering either 0.5 or 1.0 acres and receiving either 50,000 or 100,000 seeds per acre. A total of 1.6 million seeds were broadcast by hand across a total area of 21 acres. Plots were spaced across the High Shoal Marsh set-aside in a pattern that spread the various size and density combinations across shallow, medium, and deep sites, allowing future evaluation of optimal density and size for each depth zone. The total number of acres where seeds will be broadcast in 2008 will be a function of how many seeds are harvested in 2008, and a specific design chosen based on our continuing analysis of how previously planted plots are spreading. Plots will be concentrated in the Gull Marsh/Hog Island Bay area, and none in South Bay as eelgrass in South Bay is rapidly spreading naturally well beyond our set aside area.
5. MAPPING OF SEAGRASS FROM AERIAL PHOTOGRAPHS
The seaside coastal bays will be flown in 2008 to map existing stands of seagrass. Scanned aerial photographs will be georectified and orthographically corrected to produce a seamless series of aerial mosaics following the standard operating procedures used by the annual SAV monitoring program. ERDAS Orthobase image processing software will be used to orthographically correct the individual flight lines using a bundle block solution. Camera lens calibration data will be matched to the image location of fiducial points to define the interior camera model. Control points from USGS DOUG images will provide the exterior control, which is enhanced by a large number of image-matching tie points produced automatically by the software. The exterior and interior models are combined with a 30-meter resolution digital elevation model (DEM) from the USGS National Elevation Dataset (NED) to produce an orthophoto for each aerial photograph. The orthophotographs that cover each USGS 7.5 minute quadrangle area are then adjusted to approximately uniform brightness and contrast and will be mosaiced together using the ERDAS Imagine mosaic tool to produce a one-meter resolution quad-sized mosaic. Mapping of seagrass will follow protocols developed for SAV populations in Chesapeake Bay.
Robert J. Orth - (804) 684-7392; firstname.lastname@example.org
Project Open - 10/1/2007 - 9/30/2008; Project Completed
Final Product Received:
Seagrass Restoration on the Seaside of Virginia's Eastern Shore (October 2007 - December 2008) (PDF)
Project Summary Provided by Grantee:
The sixth and final year of seagrass restoration under the Seaside Heritage Program (October 2007 - December 2008) had 5 tasks: 1) monitor success of test and established seagrass areas - many of the areas planted with seeds in the early years of this restoration effort have survived, spread and become denser. In addition, in-situ monitoring has recorded numerous patches of eelgrass both adjacent to and distant from many of the established plots, suggesting movement of seeds from flowering shoots produced within these plots (see Task 5 for results of the aerial monitoring); 2) collect seeds for 2008 effort - 800,000 seeds were used for restoration efforts in Hog Island Bay and Spider Crab Bay; 3) surface mapping of water quality with dataflow - Cruises were conducted monthly throughout the seagrass growing season in 2008 on March 27, April 30, May 29, June 25, July 21, August 22, September 18, October 21 and November 20. A YSI 6600 was deployed at a fixed monitoring station at the Wreck Island restoration site in South Bay at bi-monthly intervals throughout the growing season over the following range of dates in 2007; March 29 to April 26, June 13 to July 29, August 13 to September 314 and October 10 to November 8. Water quality measurements were all within the ranges that support persistent eelgrass, which is what is occurring in these four seaside bays; 4) large scale seagrass restoration - in fall of 2008 we established 6 one acre plots in Hog Island Bay in the set aside area interspersed around the 2006 and 2007 plots, and receiving 100,000 seeds per acre. In addition, VIMS also broadcast 200,000 seeds into 4 one-half acre plots in Spider Crab Bay at 50,000 seeds per plot (100,000 seeds per acre); and 5) Aerial photographs -high level black and white images were collected in June and November 2008 and data will be available in May 2008 (http://web.vims.edu/bio/sav).
In conclusion, the success of the seagrass restoration program in the Virginia Seaside Bays (except for Chincoteague) is remarkable in size and magnitude of the restoration effort over the past six years. The spread of eelgrass, especially in South Bay, occurred at rates that far exceeded expectations. The expansion of eelgrass in each of the bays used as restoration sites, and where eelgrass has survived and expanded, stands in stark contrast to the patterns of eelgrass in Chesapeake Bay and Chincoteague Bay. Over the last decade, eelgrass populations in both of those bays have declined and are now at abundance levels similar to levels first mapped. These changes have been attributed to declining water quality in the respective bays as well as environmental conditions that have stressed the plants, e.g. the very hot summer of 2005. The unique perspective gained by comparing and contrasting eelgrass populations and the environmental conditions occurring on the Seaside have revealed interesting differences that influence the ultimate survival of the plant. With water quality declining in Chesapeake and Chincoteague bays, the lower Virginia Seaside Bays may provide a refuge for eelgrass populations.
Disclaimer: This project summary provides the federal dollars initially awarded to the grantee. Due to underexpenditure or reprogramming of grant funds, this figure may change. For more information on the allocation of coastal grant funds, please contact Laura McKay, Virginia Coastal Program Manager, at 804.698.4323 or email: Laura.McKay@deq.virginia.gov
A more detailed Scope of Work for this project is available. Please direct your request for a copy to Virginia.Witmer@deq.virginia.gov