Duxbury, Plymouth and Kingston Bays (Three Bays)
August 10 & 11th, 2021
I couldn’t be more excited to be invited out into the field for the 4th Annual Eelgrass Blitz with the North and South Rivers Watershed Association (NSRWA), MassBays, and Massachusetts Division of Marine Fisheries. Thank you Sara Grady from NSRWA for keeping me involved! On my last survey in the summer of 2019, we visited eighteen sites and found only one site had eelgrass. This was the first time I had discovered what seagrass depletion meant. In the past, I had only harvested and planted eelgrass, not really seen what loss meant. For the last several decades the percent coverage of eelgrass has been on an unfortunate declining trend. The goal of this citizen scientist project is to monitor the changes in eelgrass health and overall coverage within the embayment and find out what is driving these losses. As our team leader Olivia Freud from Saint Michael’s College explains
“ Eelgrass beds are ecologically valuable in several ways, including their ability to trap atmospheric carbon, hold sediment in place, and provide food and shelter for a variety of marine organisms. “
On both these days, we collected data on turbidity measurements and eelgrass coverage. After a while we got into the rhythm of what we were doing and didn’t even have to talk much. I loved how everyone just collaborated and did their part in collecting the data that was needed. Our lead scientist Olivia was awesome too!
DAY 1 Plymouth Bay with Captain Bill, Shannon, and Olivia
On this fine August 10th morning, we had to start by figuring out which sites(stations) to visit. We located previous stations with GPS coordinates. We got as close as 10 m radius and anchored the boat. Once we got situated we took turbidity measurements with a Secchi disk.
Turbidity measurements
Turbidity relates to the amount of cloudiness of the water. We measured turbidity by lowering a Secchi disk into the water on both sides of the boat and measured the furthest distance at which the disk was visible to the human eye. In this image the black and white disk is still visible. Once it disappears we document the length of the string – how many meters of water clarity. We did this on both sides of the boat.
Olivia explains:
This assessment of water clarity is important when looking at eelgrass coverage, because as a true grass, eelgrass needs sunlight to grow, and high turbidity could negatively impact eelgrass density.
Eelgrass Coverage:
To measure the percent coverage of eelgrass, we used a drop frame with an attached underwater camera that was connected to a live camera feed we viewed from the boat where we could see the bottom, determine percent coverage and take a picture. We released the drop frame off of each of the four corners of the boat, and at the sites that were predetermined indicator stations, we completed a sample collection from each of the corners where eelgrass was seen.
It was like hitting the jackpot ! We found eelgrass at five sites and we started measuring length, width, and condition of the blades. All of this data was recorded and uploaded to the new iSeaGrass app developed by MassDMF. SO COOL!!!
DAY 2 Duxbury Bay with Captain John, Fiona, and Olivia
On the morning of August 11th, we motored off from Plymouth Bay to Duxbury Bay in Captain John’s boat. The same two measurements were being recorded for turbidity and percentage eelgrass coverage. Our goal was to see what we could find in 9 sites that previously had seagrass.
Turbidity Measurements:
Just like the previous day, we dropped a Secchi disk into the water and sectioned off the length of the rope where we could no longer see the disk. We then used a transect measuring tape to get the actual measurements of the rope and recorded it on the app!
Eelgrass Coverage:
We dropped the camera in four corners of the boat to get documentation of the seagrass. This was a bit tricky since we kept getting bubbles and apparently we lost a screw to keep the camera in place. With a bit of quick thinking and improvising we used zip ties to stabilize the position of the camera- phew! Getting correct alignment is important with the photos. These tripods are also a little heavy making them hard to pull out. However we had a committed team on board which made it even more fun. On this trip we only found two sites out of 9 with seagrass in Duxbury Bay.
Here is how we determined the percentage of coverage with the camera
If we found a lot of sand and a few blades it would be in the 1-10% range, if there was
little bits of sand showing through it was in the 75-100% range. Below are some photos to help explain:
Here is an image we recorded :
This was defiantly in the 75- 100% coverage!
As for recording data on the length and width, we used the measuring tape on the lid of the box. These were the longest seagrass blades I have ever seen. I think the longest one was 120 cm!
The widest width we found was 3mm.
We had collected three blades from each corner recorded to have any percentage of eelgrass. We measured the length and width, looked for wasting disease and epiphyte coverage, before photographing the samples and returning them back in the water. Here is a great example of an epiphyte we found:
Here is a great link to different type of epiphytes- I believe the one we found is a tunicate. They are planktonic organisms that settle on the seagrass blades.
http://www.seagrassli.org/ecology/fauna_flora/epiphytes.html
We also pulled out baby crabs twice- super cool watching them walk sideways (will have video footage up on YouTube soon). For now it’s cool to just see them!
In summary, we visited 21 sites and to my surprise found 5 sites with seagrass in Plymouth and 2 in Duxbury- so 7 out of 21 sites pretty cool! An improvement to what we found two years ago- almost nothing! I don’t have the official data from the scientists yet, but from what I hear we are finding 1/3rd coverage. I will be reporting details once they are finalized. For now I’m happy that we found more seagrass than last time we were out. For an extra bonus, we also saw small fish jumping around Captain John identified them as “Peanut Bunkers, a type of herring” so when they jump you see lots of birds flocking to the area, which we did! Another fantastic moment was seeing an Osprey with it’s lunch neatly tucked beneath it’s body- wings stretched way out and the Pogie fish was held together with it’s special non slip feet. I decided to just enjoy this fleeting moment rather than scrambling for the camera.
Seagrass habitats help feed and protect life beneath the water and also sustain life above the water. What better way to spend summer holidays than to measure and monitor seagrass!!!!
A big thank you to Sara Grady, Olivia Freud, the team at NSRWA, Captain Bill, Captain John, Shannon and Fiona who helped in our citizen scientist project!!!!
