The Nature Conservancy (TNC) and Barnstable County
Cooperative Extension Marine Program recently completed eelgrass restoration
trials on Cape Cod. The project was designed to evaluate sites
with potential for full-scale restoration in the region. The work included identification of potential
sites, evaluating the sites for suitability, choosing the top 2 to 3 ranked
sites, performing transplant trials at these sites, and monitoring for one year
post-planting.
Site selection was done using a modification of the Short et
al. (2002) method, with modifications based on available site specific data. In
addition, consultation with an advisory team including local natural resource
officers, representatives from State and Federal agencies, and the research
community were consulted for their ideas on site suitability. Using the site data and comments from the
advisory team, sites were ranked and the top three were chosen for transplant
trials: Phinney’s Harbor in Bourne, Nauset/Town Cove in Orleans,
and Cape Cod Bay
in Truro.
Plantings
were done in September 2010 using both the clump transplant method and the
horizontal rhizome method. Monitoring
was conducted at four different times:
- 2 weeks post-planting in October 2010 to check planting density and evaluate short-term survival,
- 8 months post-planting in May 2011 to evaluate winter survival,
- 10 months post-planting in July 2011 to evaluate survival and growth over the early part of the growing season, and
- 1 year post-planting in September 2011 to evaluate survival over the first full growing season
Donor
beds were monitored in August 2010, July 2011, and September 2011 to evaluate
any effect of removing plants for transplanting, and to compare donor bed
plants with the transplants.
Transplant
success at the test sites was variable until the end of the study, when all
three
sites
had almost no surviving plants. Initially survival was almost 100% at Phinney’s
Harbor and Truro,
while the Nauset site almost no plants survived. At 8 months post-transplant the Phinney’s
Harbor site was becoming established, with survival at over 100%. The Truro
site lost many plants, and Nauset showed virtually no surviving plants. At 10 months post-transplant the Phinney’s
Harbor site was dramatically reduced, likely due to high turbidity and low
light levels. At the 1-year mark almost
no plants were left at any location (Figure 1).
 |
| Figure 1. Eelgrass Transplant % Survival |
Reasons for the lack of success differed for all three sites. Nauset appeared to have been overrun by bioturbators; the Truro site was highly dynamic, with evidence of both scour and burial among plants, grid markers and buoy anchors. Phinney’s Harbor, despite initial success, declined due to a mid-summer water quality decline, characterized by high turbidity and reduced light at the transplant site.
 |
| Truro 9-23-2010 |
 |
| Truro 10-13-2010 |
 |
| Truro 5-31-2011 |
 |
| Truro 7-19-2011 |
 |
| Truro 10-7-2011 |
Lastly, we include a short video clip taken at the Nauset donor bed in early August, 2011, which very nicely illustrates active photosynthesis - showing plants releasing O2 bubbles within the water column.
