WATER QUALITY UPDATE October 8, 2021

Lakewide Bloom Event on Canandaigua Lake

Many areas around the lake impacted by harmful algae blooms


This week, we experienced a significant harmful algal bloom event on Canandaigua Lake. Blooms extended along the vast majority of the shoreline, as well as several areas mid-lake. Other nearby lakes also reported similar extensive bloom events the last few days, including Seneca, Keuka, and Cayuga.


As we reported earlier this week, thick concentrations of cyanobacteria (harmful algae blooms) were reported along the west side of the lake on Monday (10/4) and Tuesday (10/5). By Wednesday (10/6), volunteers, watershed staff, and lake residents were documenting extensive blooms along much of the 36 miles of shoreline. Heavy surface streaking of algae and “pea soup”-like conditions were observed, in some cases extending 100+ feet off the shoreline. Streaks were also documented in mid-lake areas extending up and down the lake. It was by far the most significant HAB event recorded this season, and was one of the more extensive bloom events we’ve observed since active HAB monitoring began in 2015. Please see the images and videos below.


However, overall clarity as measured by a secchi disk remains much better than what we were observing during the bloom events of 2015 and 2018. Clarity measurements are averaging about 6 meters in the lake this week. Whereas, during the bloom events of 2015 and 2018, clarity was in the 3 meter range. This is indicating that the overall biomass of cyanobacteria is less than the other major bloom years.


The late-season timing of this bloom event is a little surprising, given the recent cooler air and water temperatures and overcast skies, which are not typically favorable conditions under which HABs form. However, we did have very calm wind conditions for three straight days, which is a big factor in allowing cyanobacteria to multiply and concentrate at the surface. We also had a significant rain event Sunday 10/3 in the northern part of the watershed that does add nutrients to the system from the surrounding drainage areas. Finally, the natural ecosystem progression of the lake typically has cyanobacteria dominating the algal community at this time of year. As mentioned above- we were not alone in seeing significant blooms- several other Finger Lakes also experienced similar bloom events. We will continue to work with our state and local research partners to better understand these dynamics.


Although the Volunteer Shoreline HABs program officially ended on Sunday, many volunteers have been keeping a trained eye on the lake and using the online reporting system to keep us notified of blooms. 39 bloom reports were filed this week and 20 water samples collected. The first batch of results can be found below. Results for CyanoChlorophyll (measurement of blue-green algae) all showed very high levels. This further stresses the point - bloom areas need to be avoided as they have the potential to be harmful to both human and pet health.



Thanks to our many CLWA volunteers for their continued support and efforts to monitor the lake in this extended season. We also want to give a special shout out to Walton Point resident Martin (Marty) Gordon, who was able to get out during Wednesday’s bloom event to capture some incredible drone footage. Check out the videos below to get a bird’s eye view of both shoreline and offshore blooms around Walton Point, and the Canandaigua Yacht Club.


The forecast for the next 10 days looks like we may get a stretch of calm, sunny weather, so please continue to use your visual indicators and use extreme caution before recreating in the lake or letting pets swim.


As always, we encourage you to follow our reports on our websites, and on the Association's facebook page for further information.









Municipal Drinking Water Test Results


The City of Canandaigua, Town of Gorham, and the Village of Rushville had detectable levels of the microcystin toxin in the raw (untreated) water samples collected on Monday, 10/4. Samples collected of the finished drinking water (after treatment was applied) had non detectable levels of microcystin. Follow up sampling was performed on Thursday, 10/7 at the Gorham water treatment plant and results of raw and finished drinking water had non detectable levels of the microcystin toxin.


This sampling is part of the proactive routine microcystin testing that all six Canandaigua Lake water purveyors (the City of Canandaigua, the Village of Newark, the Village of Palmyra, the Village of Rushville, the Town of Gorham, and Bristol Harbour) participate in for testing of both raw (untreated) and finished (treated) drinking water. Weekly results are posted on the CLWA website.


For more information, check out the HABs and Drinking water page on the CLWA website

More Information on Blue Green Algae

Click below for our Harmful Algae Bloom brochure.

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