Plymouth, Duxbury, Kingston See Alarming Eelgrass Decline

Scup are just one of several species of food and game fish attracted to eelgrass beds. | Photo courtesy Cornell Cooperative Extension Marine Program.

On January 31, the North-South Rivers Watershed Association hosted a Waterwatch Lecture Series and workshop that focused on the importance eelgrass and a plan for monitoring eelgrass in the Duxbury, Kingston, and Plymouth Bay complex, which has witnessed a loss of 56% of its eelgrass acreage between 1995 and 2014. More recently, 29% of the remaining acreage was lost between 2014 and 2017. This alarming trend has prompted a monitoring program to detect additional eelgrass loss and try to connect it to possible causes.

The workshop brought together federal and state agencies, university researchers, town staff, and interested stakeholders such as oyster growers to discuss monitoring options and develop a plan. The end result was the use of multiple types of monitoring, some of which (mapping eelgrass using photos taken from planes and using sonar fishfinders from boats) are already happening. In addition to the photos taken from planes, which happens every few years and covers a large area with relatively low detail, the group also decided to monitor random points throughout the bays. These points will be chosen randomly using a grid of hexagons to make sure they are spread out. The sampling will include taking a photograph of the bottom using a camera attached to a frame and using that photograph to determine how much of that frame has eelgrass in it. The sonar mapping will collect similar information. Finally, divers will measure eelgrass plants in one small area to learn more about their health. The goal is to understand why the eelgrass is disappearing and see if it would be a good idea to try to restore it.

The monitoring will begin this spring.