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Visitors to Tully Lake in Royalston should avoid contact with lake water due to high concentrations of algae

Published Nov. 5, 2014

CONCORD, Mass. – Visitors to Tully Lake in Royalston, Mass., are being cautioned to avoid contact with the lake water as recent tests indicate a cyanobacteria bloom at the lake, according to U.S. Army Corps of Engineers officials. The bloom started at the end of September and public notices were posted at the lake.  

Cyanobacteria naturally occur in New England waters and can be in any body of water. It is harmless when numbers are low, but when nutrient levels are high and conditions are right they multiply and form blooms that can be harmful to the environment, animals, and human health. Certain factors affect the likelihood of a cyanobacteria bloom. These include the amount of sunlight, nutrient availability (such as phosphorus), water temperature, pH levels, wind conditions, and water flow.

Visitors to the lake should ensure their animals avoid contact with the water as it can be harmful to them as well, according to Park Manager Jeff Mangum. The Corps will continue to monitor the situation and take additional tests as needed and post updates on its website when the situation changes.

Some species of cyanobacteria can release toxins which can cause health effects. The most common health effects reported for humans involve contact with the skin causing irritation and rash. Swallowing the water can cause more serious effects if in large quantities (depends on bloom concentration and toxin production). This is mainly a worry for dogs and wild animals. There have been reported deaths of animals due to cyanobacteria toxins.  Cyanobacteria can also kill fish due to depletion of dissolved oxygen levels and fluctuations of pH levels of the water. Toxins will not be removed by boiling or by hand held filtration devices often used by hikers and campers.

Laws vary from state to state on what should be done during a cyanobacteria bloom. Massachusetts guidance is that the water needs to be tested for algal species and cell counts. Once a bloom has been observed, the body of water needs to pass two water sample tests taken a week apart before it can be considered for re-opening for swimming. Cyanobacteria blooms can be seen in the water column; commonly if you look closely you can see tiny little green dots in the water column. When a scum occurs you will see a greenish film on the surface of the water (color may vary). In large quantities it can wash up on the shoreline as well. If you observe a bloom you should report it so the proper steps can be taken to ensure the water is safe.

For more information on Tully Lake recreation area call (978) 249-9150 or visit the website at:

Tim Dugan
Jeff Mangum

Release no. 2014-136