Project Report:
Ocean Acidification Mitigation in Eelgrass Beds in Frenchman Bay
Purpose
- Investigates the causes of economic imbalances.
- Explores and develops market-based solutions.

Summary

Ocean acidification is of concern in the state of Maine, as it has the potential to negatively impact economically important marine resources such as softshell clams and mussels with 2013 landings values of $16,915,005 and $2,340,965, respectively. Maine has responded to the growing threat of ocean acidification by creating the nation’s first Ocean Acidification Task Force. The task force released a report in 2015 with several major goals. One of the goals is to “Increase Maine’s Capacity to Mitigate, Remediate, and Adapt to Impacts of Ocean Acidification” with recommendations to “preserve, enhance, and manage a sustainable harvest of kelp, rockweed, and native algae...and preserve and enhance eelgrass beds.” There are no available data for the state of Maine on carbon sequestration rates of eelgrass or its impacts on ocean pH. We plan to collect this information in 2016; our findings may help to inform decision making at the state level regarding conservation of eelgrass beds.

Sediment Coring Data
Carbon stock in areas around Frenchman Bay and Mt. Desert Island, Maine. Carbon stock varies among sites in both years, however there is no significant difference between 2015 and 2016 at any site. Hadley Point does have a significantly higher carbon stock in areas with than without eelgrass in 2016 (t-test, P=0.030).

Description

Funds from the Alex C. Walker Foundation and other sources, supported the addition of two summer research fellows to our scientific team at the Community Environmental Health Laboratory. One summer research fellow sampled pH inside and outside of eelgrass beds at Hadley Point in Frenchman Bay, Maine. Another research fellow retrieved sediment cores from different sites, which were analyzed for carbon content to determine the inter-annual carbon stock and carbon sequestration rate within eelgrass beds.

We have made significant progress in meeting the following goals that were outlined in the proposal for this project.

Goal #1: Determine the carbon sequestration rate and eelgrass density in eelgrass areas around Mt. Desert Island, Maine

Outcomes:

Outcome #1: We confirmed that carbon is sequestered in eelgrass areas in Maine. Carbon stocks are significantly higher in eelgrass areas than areas without eelgrass. Over two summers, there was no net gain or loss of carbon in these areas.

To determine the inter-annual carbon stock within eelgrass beds, three sediment cores were taken from each of six sites around Mount Desert Island and results were compared with those from 2015. In both years there was a significant difference between the carbon stock in areas where eelgrass is thriving (Wonderland, Ship Harbor, and Bar East) and areas with eelgrass loss (Bar West and Hadley Point). Although there was not a significant difference between 2015 and 2016 carbon levels at any site, the carbon stock in areas with eelgrass was significantly higher than areas without eelgrass at Hadley Point in 2016. This was not the case in 2015. This may be explained by the fact that there was a 32% increase in eelgrass coverage at Hadley Point from 2015 to 2016, from 2.498 acres in 2015 to 7.810 acres in 2016.

Outcome #2: We demonstrated the relationship between eelgrass density and total carbon stock. There is a significant positive correlation between eelgrass density and the amount of carbon that is sequestered in sediments.

In both 2015 and 2016, we determined eelgrass density at all sites by haphazardly tossing 25 cm x 25 cm quadrats in the same eelgrass areas that were being assessed for carbon levels and counting the total number of shoots. We found a significant and positive correlation between eelgrass density and carbon stock when data from the two years were combined (Pearson Correlation Coefficient: r = 0.715729, p = .009).

Goal #2: Identify and implement easiest and best methods for determining relative pH of sediments in eelgrass areas.

Outcomes:

Outcome #1: We have data on eelgrass density, carbon stock, and sediment pH, which we will share with stakeholders in order to influence action on protecting eelgrass in Maine.

We adapted methods being used elsewhere in the state of Maine to assess sediment acidity in clamflats. Sediment pH was measured using a Hannah sediment pH meter along 10 meter perpendicular transects inside three areas at Hadley Point: one that has naturally occurring eelgrass, one that has never had eelgrass, and one in a restored eelgrass bed, and at two depths: 2 cm and 5 cm. Average sediment pH was significantly higher along transects at naturally occurring and restored eelgrass sites than in areas with no eelgrass at a depth of 2 cm. Average sediment pH was significantly higher in naturally occurring eelgrass areas than areas with no eelgrass at a depth of 5 cm as well, however this was not true when comparing restored eelgrass areas and areas with no eelgrass at a depth of 5 cm. It may take some time for carbon to accumulate at greater depths after eelgrass restoration.
At depths of 2 cm and 5 cm there was no significant difference between average sediment pH in naturally occurring and restored areas, indicating that restored sites have essentially the same properties and capacity to sequester carbon as naturally occurring beds.

Outcome #2: We have been in contact with teachers and researchers from two communities in mid-coast Maine interested in eelgrass restoration in 2017. We will work with them to document sediment pH over time to determine if restored eelgrass has the capacity to mitigate near-shore ocean acidification across the region.


Goal #3: We plan to organize a second Maine and New Hampshire Eelgrass Working Group meeting in January 2017.

Outcomes:

Outcome #1: Our carbon stock and pH findings will be shared across the various sectors that participate in our working group. Some other groups in Maine have done similar work on sediment pH and carbon stocks and we will discuss our cumulative findings.

Outcome #2: We will prepare a report on our collective findings and share with the Maine Ocean and Coastal Acidification Coalition and state legislators. The Coalition is interested in addressing the issue of acidic muds in order to enhance clam spat settlement and improve clam harvests in Maine.

Goal #4: We plan to participate on regular basis in meetings of the Maine Ocean and Coastal Acidification Coalition meetings and in conversations on their google listserv.

Outcomes:

Outcome #1: We are staying up-to-date on what actions are being proposed in the state to mitigate ocean acidification.

Outcome #2: We will bring our findings to bear on state-level conversations on ocean acidification. We will be attending the next meeting in Augusta, Maine on November 15, 2016.

Purpose

Investigate Causes of Economic Imbalances: Economic imbalances exist in Frenchman Bay and elsewhere in the state of Maine where the impacts of ocean acidification have the potential to destroy a nearly seventeen-million-dollar softshell clam industry and over two-million-dollar blue mussel industry.
Explore and Develop Market-Based Solutions: We plan to collect carbon sequestration and pH data that may help to build the case for protection of eelgrass in Maine. If we are able to effectively connect the dots between eelgrass carbon sequestration rates, mitigation of ocean acidification, and healthy softshell clam populations, we may be able to conserve eelgrass areas that provide a plethora of other highly valued ecosystem services such as nursery habitat, nutrient uptake, sediment stabilization, and absorption of wave energy.



Scope

We propose a scientific study to elucidate the relationship between eelgrass and carbon sequestration and the potential off-set of ocean acidification. We will share our process and results with our Maine and New Hampshire Eelgrass Working Group and the Maine Ocean and Coastal Acidification Coalition (a group that emerged from the Maine Ocean Acidification Task Force). The two groups have goals that align with conservation and restoration of eelgrass. The groups have representatives from the scientific community, non-profit groups (for example, The Nature Conservancy, Maine Coast Heritage Trust and Island Institute), coalition groups (for example, Frenchman Bay Partners and Casco Bay Estuary Partnership), state agencies, and state and local legislators. By considering the economic impact of ocean acidification together with potential for eelgrass to sequester carbon and mitigate effects of rising pH, we may move forward a process to protect eelgrass in Maine and beyond.

Information Dissemination

A press release by the MDI Biological Laboratory in 2016, "The Disappearance of Maine’s Eelgrass Meadows", called on the public to continue sharing their observations on our citizen science data portal at Anecdata.org. Our “Eelgrass in Maine Project” is on-going and is helping us track eelgrass throughout the area. The Maine Public Broadcasting Network (MPBN) wrote an article, "Maine Lab Seeks Citizens’ Help to Determine Why Eelgrass is Disappearing", detailing why it’s important to engage citizen scientists in collecting eelgrass data. A segment on the local news, "Missing Eelgrass Is Raising Concerns for Scientists", showed students and members of the Community Environmental Health Laboratory collecting density data at Ship Harbor and mentioned Anecdata.org.

Overall, we had a productive summer. We have discovered more about the capacity of naturally occurring and restored eelgrass to modulate sediment pH and to sequester carbon. We presented posters at the Acadia National Park Science Symposium on October 5th, 2016 and plan to publish the carbon stock data later this year and repeat the pH studies next year in more areas.

Amount Approved
$20,000.00 on 5/31/2016 (Check sent: 6/7/2016)


  Related Organizations
Mt. Desert Island Biological Laboratory  

Data coring horizontal
Summer Research Fellow, Dakota Holmes, from Mercyhurst University in Erie, PA, collects a sediment core from an eelgrass area at Hadley Point, Maine.

Posted 3/21/2016 5:12 PM
Updated   10/19/2016 3:15 PM

  • Nonprofit


Sampling Sites around Mt. Desert Island, Maine
Carbon Stocks were assessed at multiple sites around Mt. Desert Island, Maine.

Eelgrass Distribution at Hadley Point in Frenchman Bay, Maine
Eelgrass coverage at Hadley Point in Frenchman Bay, Maine. There was a 32% increase in eelgrass coverage from 2.498 acres in 2015 to 7.810 acres in 2016, in part due to restoration efforts. The carbon stock (MgC/ha) also significantly increased at Hadley Point between 2015 and 2016.

Correlation Between Eelgrass Density and Carbon
There is a significant and positive correlation between eelgrass density and carbon stock when data from 2015 and 2016 are combined.

Average Sediment pH in Eelgrass Areas at Hadley Point
There is a significant difference in average sediment pH between areas with no eelgrass and areas with naturally occurring (t-test, P = .0299) or restored eelgrass (t-test, P = .0065) at a depth of 2 cm. There is also a significant difference between average pH of sediments from naturally occurring eelgrass areas and areas with no eelgrass at a depth of 5 cm (t-test, P = 0.0083). However, areas with restored eelgrass did not have significantly higher pH than areas with no eelgrass at a depth of 5 cm. It may take some time for carbon to accumulate at greater depths after eelgrass restoration.

 
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