Harmful Algal Blooms

The Issue
Cyanobacteria (blue green algae) have naturally been present in lakes for centuries. A combination of factors allow the algae to grow into blooms that can harmful to human health and  degrade our water quality:

  • Phosphorus and nitrogen inputs (nutrients) from the surrounding watershed feed the algae.
  • Hot, sunny, and calm weather creates ideal cyanobacteria growing conditions.
  • Zebra and quagga mussels don’t filter blue green algae out of the water.
  • Nutrients originate in the watershed and have many sources. Reducing nutrients from the watershed is the only strategy we have to help limit our impact.

What to look for:
BGA_9_18_Greg Talomie
Use visual cues to identify harmful algae blooms. They can appear like pea soup, spilled paint, globs, and parallel streaks. The color is typically blue-green to green to yellow, but can also be brown, red or purple.

Its important to remember: If you see a bloom, avoid it! Blooms can move up and down the water column, and can be pushed by wave and wind action. They can appear quickly in the lake when the conditions are just right. Please use your visual indicators before recreating in the water – stay safe and avoid it.

Shoreline Monitoring Program

To help us increase our understanding of the blue green algae dynamics in Canandaigua Lake, in 2018 CLWA launched a Volunteer Shoreline HABs Monitoring Program. Volunteers work closely with watershed staff to help monitor the lake’s condition and provide more “eyes on the watershed”.  Sixteen CLWA volunteers have been trained to perform weekly surveillance to look for and sample harmful algal blooms. Findings will be reported to the public on our website, facebook page and in our email blasts.

2018 Program Summary 
Volunteers and Watershed Staff collected samples for 10 weeks as part of the Shoreline HAB Monitoring Network. We thank each and every one of our 17 volunteers for all their efforts to help collect information on the algae dynamics in our watershed. Results are as follows:

Water samples collected by volunteers and watershed staff and submitted for lab analysis 54
DEC Confirmed Blooms
(results exceeded 25 ug/L Blue Green Chlorophyll a)
Confirmed with High Toxins
(results exceeded 20 ug/L of Microcystin)

A spreadsheet of results can be found here:  DEC HAB Results 2018

Weekly Reports can be found here:

Week one (July 29-31): No blooms Reported
Week two (Aug 5-7): No Blooms Reported
Week three (Aug 12-14): No Blooms Reported
Week four (Aug 19-21):  We started to see light streaking of Blue Green Algae (BGA) in a few isolated locations on both sides of the lake and we are also seeing visible dots in the water. Two samples were collected and DEC results confirmed microcystis.

Week Six (September 2-4): We have seen confirmed blooms at multiple locations around the lake beginning on 9/4.  We know based on past sampling efforts that blooms may be toxic so it is best to avoid these areas altogether. Volunteers and Watershed Staff collected 10 samples from around the lake on 9/4, which have been sent on to the State lab to be analyzed. See below map for locations.Week five (August 26-28):  The DEC confirmed confirmed the presence of cyanobacteria based on blue-green chlorophyll a levels of 181.24 µg/L (above the DEC Confirmed Bloom threshold of 25 µg/L). The site has been revisited each day since the bloom occurred and it has been clear.

Conditions on 9/5 and 9/6 improved, but we encourage you to continue to look for signs of active blooms before recreating in the lake.

Week seven (September 9 – 13): We received results from the DEC on fourteen samples that were collected over the last week, and all but two samples came back over the bloom criteria of 25 ug/L of Blue-Green Chlorophyll a. This is reinforcing that we need to continue to use extreme caution when coming in contact with the water. Blooms can come and go quickly, and some areas that are clear in the morning may experience blooms later in the day. Please use your visual indicators and always look for signs of a bloom before entering the lake or letting your pets swim.

Additionally,  Based on many of these photos coming from the southern half of the lake where there is no public water supply- we would highly suggest that if you have a PRIVATE water system and you draw water directly from the lake that you should consider using bottled water. Here is a link to a fact sheet from the Health Department that would be helpful in your decision making:   https://www.health.ny.gov/publications/6629.pdf

Week eight (September 16-18): Five samples were collected by shoreline volunteer this week, three of which came back above the DEC bloom threshold (25 ug/L). Many areas of the lake are clear, but it is hard to pinpoint where blooms may be occuring at any given moment, so please continue to use your visual indicators before swimming or letting pets enter the lake.

Week nine (September 22-24): Three samples were collected this week by shoreline volunteers – two of which came back above DEC bloom levels of 25 ug/L. Watershed staff received one additional call this week about suspicious bloom activity but it ended up being duckweed / watermeal. There may be isolated areas of the lake still experiencing blooms – we encourage you to look for signs of active blooms before recreating in the lake.

Week ten (September 29-October 2): No Blooms Reported. This marks the final week of the official volunteer shoreline monitoring program. Watershed Staff will continue monitoring and will respond to reports coming in. Several volunteers will remain active in their monitoring efforts as well.

Check out our Water Quality Update Page for more details.

Current HABs status
Hover over the icons for further details on samples collected. PLEASE NOTE: Water quality conditions can change daily, if not hourly. This map serves as a record of the samples collected this sampling week and may not indicate current lake conditions. Please continue to use your visual indicators and look for suspicious algal activity before recreating in the lake. If no blooms are observed during the sampling week, then no markers will appear.

Green markers – Tested and No Bloom shown
Yellow markers
Suspicious Bloom
Orange markers – Confirmed Bloom
Red markers – Confirmed with High Toxins

How you can report suspicious blooms
Help by collecting information on blooms:

  • Location (GPS coordinates, address, or geographic description of the area )
  • Photos
  • Description – Was it streaky, globby, threadlike, like spilled paint, like pea soup, scummy, silky, or have small leaves? What color was it?
  • How large of an area did it cover?
  • How long was it there?

Report Suspected Blooms to HABs@canandaigualakeassoc.org.  

Additional Resources:

hab brochure pic

HAB Brochure Canandaigua Lake

dogs and habs pic

 Dogs and HABs Fact Sheet


On October 20, 2015, the Canandaigua Lake Watershed Association and the Canandaigua Lake Watershed Council co-hosted a community discussion on the September blue green algae event.  A panel of experts each presented a powerpoint, followed by a question and answer session. The experts discussed the science behind blue green algae and the sequence of events on Canandaigua Lake. Video and presentations are below.

Kevin Olvany – Blue Green Algae presentation

Scott Kishbaugh – Canandaigua Presentation

Dr. Greg Boyer – Introduction to HABs

October 20, 2015 Canandaigua Lake Watershed Association – Blue Green Algae Presentation [HD] from Finger Lakes TV on Vimeo.