Toxic bacteria in Hopkins Pond

By Larry Chase
Evidence of cyanobacteria presence in the pond indicated by its grayish color.

At 27 acres, Hopkins (or Adder) Pond is one of Andover’s smallest water bodies, but it has been the object of significant scrutiny in recent months, the result of citizen reports and New Hampshire Department of Environmental Resources (DES) tests that confirmed extremely high levels of toxic, tiny single-celled organisms known as cyanobacteria.

Warning sign at Hopkins Pond

While DES testing in November revealed that cell counts had dropped to below critical levels, earlier reports indicated counts far above that level. According to DES, it issues advisories for cyanobacteria when cell counts reach 70,000 per milliliter, and samples from Hopkins Pond were as high as 3.55 million per milliliter in early October. A milliliter is less than 1/25th of an ounce.

As a result, advisory signs like the one shown in the photo above were posted at the Hopkins Pond parking lot on Elbow Pond Road and the boat put-in area at the pond, but then removed when the cell count dropped.

As the advisory sign notes, “Exposure to blue-green algal scums may cause various symptoms, including nausea, vomiting, diarrhea, mild fever and general malaise.  Anyone who comes in contact with algal scum should rinse off with freshwater.”

The causes of the bloom have not been determined, according to DES Beach Program Coordinator Amanda McQuaid, so it is difficult to predict what the future holds.  Meanwhile, she says, “In any waterbody, always be wary of green turbid water or, in this case, clay-colored. If the water is not very clear, be wary.

“And if you see anything like this developing next year, please take a photo and call me at 603-848-8094 – the cyanobacteria hotline – and I’ll respond immediately.  And keep your dogs out of anything you are suspicious of.”