Aid from the ocean

Until two weeks ago Georgica Pond was open and exchanging with the Atlantic Ocean bringing in high salinity water.  While this salty water has not deterred the macroalgae that are presently overgrowing parts of Georgica Pond, it may discourage the other, more dangerous type of algae in the Pond, blue-green algae.  Blue-green algae are microscopic, but more dangerous than macroalgae as they synthesize biotoxins that can poison animals including pets and even humans.

In perhaps some good news, these blue-green algae have a love of freshwater and are generally found in freshwater lakes and ponds.  In 2014, blue-green algae emerged in Georgica Pond only once the salinity dropped to 7 grams per kilogram of water (See figure below).  One year ago today, when the Pond had been closed for months, the salinity was less than 9 (See figure below).  Today, after months of being open, the salinity in Georgica Pond is 20 (See figure below). As a point of reference, ocean salinity is about 31.  The salinity will drop further in the coming weeks as natural groundwater and stream flow slowly fills the Pond.  The questions will be, how long will that take and how low will the salinity get?  Because there are no prior salinity records of the Pond being opened as long as it has been in 2015, we are entering some uncharted territory.  We can eagerly watch the buoy in the coming weeks to see what happens:

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