Wednesday, July 18, 2012

Toxic algae bloom reported in Eastham

"Town officials are warning swimmers and pet owners to avoid Molls Pond off Alston Avenue because of the growth of blue-green algae." The problem was noticed when a dog became sick, after drinking from the pond.

"Possible health effects range from rashes, hives or skin blisters to runny eyes and nose, sore throat, diarrhea and vomiting.  In rare cases, exposure can lead to neurological symptoms, including drooling, weakness, staggering, convulsions, and death in dogs.  Humans may experience dizziness, numb lips or tingling fingers. Source

Nearby dump may be a cause

Algae blooms are caused by excess nutrients, reaching the pond via overland runoff or through the groundwater.

The pond is surrounded by houses, so leaking septic systems could be part of the problem.

View Larger Map
The old dump is the smooth area, upper left.

A capped landfill is located about a thousand feet to the NW of the pond.  The direction of flow of groundwater is generally towards the pond.  So leachate from the landfill, laden with nutrients, may be reaching the pond.  Even if the landfill is properly constructed now, the nutrients may have escaped when the dump was young and unregulated, and only reaching the pond now.

Could algae become a problem at Hawksnest?

Hawksnest has the best water quality of any pond in Harwich, and has never experienced an algae bloom.

But keeping it that way depends on keeping all sources of nutrients away.  Because of the wide buffer of state  park around the pond, Hawksnest has a good chance of escaping a nutrient overload from septic systems.

But dog and human waste is rich in phosphorus, the nutrient that's the number one cause of algae blooms.  There are no restrooms at the pond, and some pet owners don't pick up after their pets.

Landscapers have been dumping yard waste along Round Cove Rd near the pond.  Erosion of the Round Cove parking area continues.  And the commercial area NE of Hawksnest continues to expand.  So the long-term prognosis for Hawksnest depends on how well we care for the pond, and the direction of flow of the goundwater.

Phosphorus moves slowly through the groundwater, so it's possible that the nutrients from development around Hawksnest haven't reached the pond yet.  The fact that the pond is still clean isn't a reason for doing nothing.  If anything, it means we still have a fighting chance to save the pond from the overabundance of nutrients that has damaged so many ponds on the Cape.

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