Eelgrass (Zostera marina) is a flowering marine plant that essentially defines the coast of Maine. It grows in thick beds that provide shelter to commercially important fish and shellfish species and other organisms that make up near-shore food webs. The underground stems and roots of the plant help to stabilize bottom sediments, thus preventing erosion and promoting water clarity.
On January 22, eelgrass scientists and others interested in eelgrass conservation in Maine and New Hampshire came together to share work in progress and discuss future directions for eelgrass research and restoration in Maine. Six presenters covered topics ranging from eelgrass loss in Frenchman Bay, Casco Bay, Lamprey Bay, and Great Bay, to what archaeological flounder bones can tell us about past eelgrass habitats. Attendees discussed possible next steps, including eelgrass restoration in Casco Bay with assistance from the MDI Biological Laboratory and partners. Read the full summary here.
The Community Environmental Health Laboratory (CEHL) tried four new methods of restoring eelgrass this past summer. The season began with the tried and true method of tying eelgrass plants onto wooden, biodegradable grids strung with twine. The up front time required to construct the grids with string and make ties from floral tape prompted the development of further prototypes. We next tried weaving plants through pieces of burlap stretched across the same biodegradable grids. We quickly realized the time required to weave eelgrass into the burlap on shore was too much. At the scale CEHL hoped to restore, both the string and the burlap grid methods necessitated too much time and effort.
Students in the Young Environmental Leaders Program created a burlap “restoration runner” weighted with sandbags. Eelgrass was woven into the seven foot long runners. Another method involved tying eelgrass onto metal washers, which were dropped from the boat into the water at the restoration site. In an effort to move away from the potential environmental impact of metal washers and decrease the cost of restoration, CEHL tried using rocks instead of washers.
To date, we have used frames with eelgrass tied to strings, frames with eelgrass woven into burlap, burlap without frames with eelgrass woven in, eelgrass tied to washers, and eelgrass tied to rocks. We are working on a seeding method. Seeding plants have been collected and are maturing in a flow-through seawater tank. Eelgrass restoration methods will continue to evolve as different challenges arise.
Mary Badger, Smith College
Abstract: In 2013, there was a devastating loss of eelgrass (Zoestra marina) in upper Frenchman Bay, Mount Desert Island, Maine. This study examined the relationship between the most recent invasion of novel haplotypes of the European Green Crab (Carnicus maneas) and the decline of eelgrass in upper Frenchman Bay. While C. maneas is an invasive species that has been present in the Gulf of Maine for over 100 years, a second invasion of C. maneas in Nova Scotia occurred during the 1980s and 1990s, bringing novel haplotypes of the species that have been cited to be more cold tolerant and voracious as compared to other haplotypes. The presence of these new haplotypes has been hypothesized to be a contributing factor to habitat destruction along the Maine coast. In 2013, northern haplotypes of green crab were documented in upper Frenchman Bay where the eelgrass had disappeared. In order to assess this relationship, the cytochrome oxidase I (COI) haplotype of the crabs at sites around Mount Desert Island was determined as well as the abundance of the eelgrass at corresponding study sites. The study did not find a significant correlation between the presence of northern green crab haplotypes and eelgrass abundance at the study sites. This indicates that the status of eelgrass health is not dependent on the genetic composition of green crabs that are present. It is more likely that factors such as green crab abundance or water quality are contributing to the declining health of eelgrass beds along the Maine coast.
Alden Dirks, Swarthmore College
Abstract: Eelgrass (Zostera marina L.) supplies myriad ecosystem services that make it an indispensable cornerstone of coastal environments. The complete disappearance of eelgrass in upper Frenchman Bay, Mt. Desert Island (MDI), Maine, in 2013 matched a precipitous drop in the concentration of dissolved silica (DSi). Eelgrass in outer Frenchman Bay and other locations around MDI appeared to be intact; however there were no DSi data to compare with upper Frenchman Bay locations. To investigate the relationship between eelgrass health and DSi, we determined eelgrass abundance and biomass at six locations around MDI. Furthermore, we measured dissolved nutrient concentrations in the water column as well as tensile strength and nutrient composition of tissue samples. We found a positive relationship between eelgrass abundance and biomass, and a positive relationship between biomass and the concentration of nitrite and nitrate. In addition, tensile strength was significantly different across the six sample sites. However, neither abundance nor tensile strength was significantly correlated with nutrient composition of the plants or water quality. These results reveal a deeper complexity to the issue of eelgrass abundance and tensile strength that requires further nuanced investigation into other factors such as local geography, oceanographic currents, and sediment type as they relate to eelgrass viability.
Everyone has been hearing a lot about green crabs and their destructive nature these days. Frenchman Bay definitely has its share of them. Green crabs are an invasive species from Europe that were unintentionally introduced to the Eastern shores of America in the 1800s. Their numbers have been increasing ever since.
Maine Sea Grant sponsored a Green Crab Summit at University of Maine in December 2013. Many Frenchman Bay Partners were in attendance. The presentations provided a lot of detail about green crabs, their life history, and their impacts on shellfish populations and as well as salt marshes and seagrass beds. They can be viewed at http://www.seagrant.umaine.edu/green-crab-summit. Several Frenchman Bay Partners, including representatives of the Bar Harbor Shellfish Committee, MDI Bio Lab, and Frenchman Bay Regional Shellfish Committee participated in a one-day, state-wide survey of green crabs last summer, focusing their sampling efforts in Bar Harbor, Lamoine, Trenton, Sorrento and Sullivan. The results of the survey can be found on the Maine DMR website . The report concludes that green crabs are present throughout the state and in numbers that represent a detrimental impact to bivalve shellfish.
Click here to access an academic poster by Bates College student Camilla Nivison, and advisors Larissa Williams and William Ambrose detailing the population genetics of invasive green crab, Carcinus maenas, in the Gulf of Maine.
One of the most successful marine invaders, Carcinus maenas has established populations on all temperate coasts. The past few years have seen a surge in the abundance of C. maenas and their impacts on coastal communities from Long Island to Nova Scotia, which may reflect a new strain of C. maenas introduced into the region from Northern Europe. As a marker of genetic diversity and gene flow between populations, I studied haplotypes caused by silent mutations of the mitochondrial cytochrome c oxidase I (COI) gene. I found the highest genetic diversity in the northern sites (NS: h=0.7619). Pairwise comparisons show Nova Scotia and Mt. Desert populations are genetically more differentiated from the other populations (NS: FST=0.4201 , MDI: FST=0.1448) likely caused by the recent invasion to Nova Scotia, which has subsequently spread south.
The U.S. Army Corps of Engineers has awarded the Mount Desert Island Bio Lab a grant of $239,000 for eelgrass restoration in Frenchman Bay. The grant will enable the Lab and its partners to restore an additional 214 acres of subtidal habitat off Lamoine, Bar Harbor, and Trenton over the next two years.
The grant is the first to be awarded in Maine under the Estuary Habitat Restoration Act of 2000 and one of only two to have ever been awarded in New England. The Army Corps grant will fund two years of restoration and research activity in Frenchman Bay and two AmeriCorps positions at MDIBL.
“With the Army Corps’ support, we will be able to ramp up our research and restoration efforts substantially,” said Jane Disney, director of the Community Environmental Health Laboratory at MDIBL and president of Frenchman Bay Partners. “Our goal is a productive and sustainable future for Frenchman Bay. By restoring eelgrass, we will improve the bay’s economic productivity as well as its biodiversity.”
The Frenchman Bay Partners’ plan of restoring an additional 228 acres of eelgrass this summer had to be put on hold when it became clear that eelgrass was not coming back in the restoration areas that had been thriving for years. Not only that, many formerly healthy beds that had been growing at least since mapping began in 1996 were also lost this year. MDIBL’s Community Environmental Health Lab (CEHL) had to quickly change gears to begin studies on possible causes of the loss. Scientists and interns looked into the possibilities of “wasting disease” (the pathogen Labyrinthula zosterae) which caused devastation to the plant in the 1930s, nutrient deficiency in the sediment, temperature changes, and invasive green crabs. Continue reading