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Harmful Algai Blooms

Most algae do not impact human health, however, certain types of blue green algae (such as Microcystis), are capable of producing toxins.  When concentrations of these algae are high enough, they can pose a risk to human, pet, and wildlife health. The health threat depends on the type of toxin produced and level of exposure, but can range from skin rashes to liver and neurological problems.

The Issue:

It is well understood that increased nutrient loading from the surrounding watershed directly impacts algae levels.  However, research around the country is trying to determine what conditions trigger the development and release of the toxins in these algae. Federal or NYS guidelines on safe concentrations of blue green algae have not yet been established, though they are underway.  In 2013 and in previous years, Canandaigua Lake has experienced increased algal concentrations dominated by blue- green algae.

In late August of 2013, Secchi disk water clarity readings dropped below 3 meters, raw water turbidity doubled (algae based) and samples analyzed by Dr. Bruce Gilman documented that Microcystis was dominant algae in the water. The increasing dominance of Quagga Mussels along with runoff events has created the conditions for blue-green algae to continue to dominate the algal bio-mass.  Minimizing phosphorus into the lake will be the only manageable way to curtail blue green algae levels.

Algae bloom observed at the north end of Canandaigua Lake in 2009.


What’s Being Done:

Long-term Monitoring: Testing for the presence of harmful blue-green algae such as Microcystis is one of the many components of the long-term water quality monitoring program that started in 1995. Further testing when an algae bloom is suspected and communication to the general public is important to minimize the risk of exposure and protect public health.

‘Take a Dip for Canandaigua Lake’ Volunteer Monitoring Program: The Watershed Council has partnered with the Canandaigua Lake Watershed Association to train volunteers to monitor water clarity in different locations throughout the lake, augmenting the monthly data collected in the long-term monitoring program with weekly data from volunteers.  Water clarity can be impacted by both sediment and the presence of algae; however, a rapid decrease in water clarity in the absence of storm events usually indicates the start of an algae bloom.  Further testing can then be performed.

“Take a Dip” volunteer taking a water clarity reading using a Secchi disk.


Pollution Prevention: Education is a key component in preventing lake conditions that can result in harmful algae blooms.  By educating homeowners, community members, business owners and farmers about the importance of preventing nutrient enrichment of our lake by managing storm water and runoff, we can all work towards the common goal of improving water quality in Canandaigua Lake.

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