Green filamentous algae is blooming in Edgartown Great Pond:

Great Pond Foundation scientific staff noticed several isolated floating patches of bright green algae on Thursday July 12th, in Edgartown Great Pond. These clumps appear to be green filamentous algae and were noticed along the barrier beach, just west of Crackatuxet Cove.  With the help of drone pilot and photographer David Welch, we were able to get an aerial perspective to understand the scope of the problem.  There are small isolated patches along the barrier beach as see below.

Clumps of green algae on the delta of sand just north of the barrier beach, west of Crackatuxet Cove. Photo courtesy of David Welch.

When we flew eastward, we found the most dense bloom lining the southeast corner of the Pond by the sluiceway.  The algal bloom appears to spread from the corner of the Pond closest to Crackatuxet Cove along the eastern shoreline of the EGP towards and into Slough Cove.   Small patches of green algae have been spotted as far away as Boldwater Landing, but the thickest and deepest algal mats appear to be isolated to the SE corner of the Pond.

Algal bloom is most concentrated in the SE corner of the Pond near Cracktuxet Cove. Photo courtesy of David Welch.

Great Pond Foundation is taking a 3-phased approach to this bloom:

  • Monitoring the scope, distribution, identity, and rate growth of the bloom
  • Increasing water sampling around the bloom to monitor Pond health and nutrient load
  • Exploring management options to deal with the current bloom and to reduce the risk of a reoccurrence

We took an algal sample to WHOI scientists this afternoon for a species identification.  Here are photos from the collection site:

The potential impacts to the water quality and ecosystem health of Edgartown Great Pond are serious. The algal bloom is spreading through eelgrass meadows that have been making a rebound in recent years.  As is our mission, we are working in conjunction with the Town of Edgartown to protect and preserve Edgartown Great Pond.  As we learn more, we will keep you posted.


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