Spy Pond is a shallow body of water situated near the center of Arlington. The pond is fed by a combination of ground water and surface runoff from the surrounding area. Swimming in the pond is prohibited because it does not meet the Minimum Standards for Bathing Beaches (State Sanitary Code, Chapter II), however, it is used in some cases for recreational purposes (canoeing, kayaking, etc). The Town of Arlington does not test the water quality at the pond. In recent years the Massachusetts Department of Public Health (MDPH) was awarded grant funds by the Centers for
Disease Control (CDC) to conduct research on harmful algae blooms (HABs). Spy Pond is one of five bodies of water in the Commonwealth that was chosen as a weekly testing site by MDPH. For the past 3 years MDPH has been testing the water to monitor the presence of cyanobacteria (blue green algae).
Cyanobacteria are bacteria that grow naturally beneath or on the surface of many water bodies. Under certain conditions (warm weather and an abundance of nutrients in the water) the algae may undergo an explosive type of growth that results in dense, floating mats of algae. This is commonly referred to as an “algae bloom”. During an algae bloom, the amount of algae and toxin in the water can become elevated and exposure can be potentially harmful to people and animals.
During an algae bloom, the amount of algae and toxin in the water can become elevated and exposure can be potentially harmful to people and animals.
Contact with high levels of the cyanobacteria algae has been found to contribute to eye, ear, and skin irritation. Microcysstis is one type of cayobacteria that is capable of producing a toxin, microcystin, in the water. Ingestion of this toxin can cause more serious issues such as liver damage. While cyanobacteria can produce a number of other toxins, microcystin is the one that is most commonly found and tested for. It should be noted that high levels of cyanobacteria may indicate the presence of other cyanobacteria toxins. Therefore, contact with the water should be avoided during a bloom.
MDPH developed a protocol with guidelines for issuing advisories in response to HABs. Advisories are recommended when either a visible cyanobacteria scum or mat is present or the analyses of water samples for algae cells or toxin levels exceed guideline levels:
a. A cell count exceeds 70,000 cells/mL
b. A microcystin toxin level exceeds 14 ppb
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