Duxbury, Kingston, and Plymouth Bays have experienced severe declines in eelgrass coverage over the last several decades (Fig 1). Since 2017 NSRWA, MassBays, MA DMF, and MA DEP have launched a targeted sampling program to evaluate eelgrass health and contributing factors in the decline. We collect this data using a drop camera to measure eelgrass percent cover at 119 sites throughout the bays. The sites are also grouped into 10 ‘clusters’ representing geographic portions of the bays. We also selectively collect and measure eelgrass shoots and assess them for wasting disease and growth of organisms on the eelgrass blade.
Fig 1. Eelgrass loss from 1995 to 2017 (MA DEP)
The 2024 eelgrass surveys in Duxbury, Kingston, and Plymouth bays were highly successful with sampling conducted at all 119 of our target sites. The sampling took place across eight survey events in a three week period between July 23rd and August 13th. The work was conducted by a mix of staff, interns, and volunteers. An extra special thanks goes out to our six amazing boat captains who volunteered their time, boats, and skills to make these surveys safe, efficient, and fun. We literally couldn’t have done it without you!
Step 1: Camera goes over the side
Step 2: Camera takes photo of the seafloor.
Hopefully we see a healthy eelgrass meadow!
Step 3: The science crew determines eelgrass coverage and enters data into the database.
There was Some Good News and Some Bad News in the 2024 Results
The good news was a slight increase in eelgrass since last year. Fifty two of the 119 sites sampled had eelgrass. As compared to 2023: 41 individual sites had an increase in eelgrass coverage, 17 sites had a decrease, and 61 sites remained the same. Across the ten geographic clusters: 6 clusters had an overall increase and 4 had a decrease. The largest gain was 11% in Cluster B just inside Plymouth’s Long Beach. The largest loss was 10% in Cluster G between Clark’s Island and Saquish. There was a total 1.7% increase in eelgrass coverage across the overall sampling area. Figures 2 and 4 show the 2023-2024 comparison.
The bad news is that the longer-term trend still appears to be negative. While there was still a mix of gains and losses across this five year span, the losses were much more substantial. For example losses near Clark’s Island at Clusters G and J both exceeded 21%. Figure 3 shows the 2019-2024 comparison.
Figure 2. Percent change in eelgrass from 2023 to 2024
Figure 3. Percent change in eelgrass from 2023 to 2024
Figure 4. Map of 2023-2024 eelgrass change at clusters and individual stations.
The results reported here are preliminary and are just a subset of the overall data collected. This winter we will further evaluate sediment type, water clarity, eelgrass blade size, and eelgrass disease presence. We look forward to sharing all of those results when they are ready. Stay tuned for ways to get involved in the 2025 surveys!
