Harmful Algal Bloom on Lake George

Lake George recorded a Harmful Algal Bloom in November 2020.

The emergence of this late-season Harmful Algal Bloom is more than a curiosity. It is a serious problem for Lake George and one that requires serious work for all of us.

You can see our most recent news releases on the HAB here: https://www.lakegeorgeassociation.org/category/harmful-algal-blooms/

The identification by Kristen Wilde, Director of Education for the LGA, of the late fall HAB is an alarm bell for us all. We knew it was possible, and now we have scientific evidence that it has happened.

LGA Director of Education Kristen Wilde samples the HAB in Harris Bay in the fall of 2020.

While the New York State DEC and the scientists at the Jefferson Project have identified the type of cyanobacteria that caused the HAB – a type of Dolichospermum – the cause has not yet been identified yet.

The cyanobacteria Dolichospermum, pictured, came from the water samples taken by the LGA in Harris Bay. The photo was also taken on an LGA office microscope.

The Dolichospermum pictured came from the water samples taken by the LGA in Harris Bay on Nov. 9, 2020. The photo was taken on an LGA office microscope.

Dolichospermum is a common cyanobacteria that can produce toxins that can affect nerves, liver, and irritate skin.

Limit Nutrients

While the investigation continues into the cause, what we know for sure is that Harmful Algal Blooms – and algae in general – need nutrients in the water in order to survive and grow.

And stopping nutrients from getting into the water will help keep all algae from getting out of control.

A little about Harmful Algal Blooms.

A Harmful Algal Bloom (HAB) is an overgrowth of algae in a water body that could affect water quality and aquatic life.

HABs are typically made up of blue-green algae called cyanobacteria. Some HABs produced by cyanobacteria can create toxins that may also harm people, animals, and the local environment.

Evidence of the late fall Harmful Algal Bloom in Lake George as seen in Harris Bay.

Cyanobacteria are highly specialized and competitive ancient microscopic bacteria that have been in the Lake for centuries. Cyanobacteria are naturally present in virtually all water bodies. In our water quality reports, information on blue-green algae began to be included in 2017 — and those tests have picked up low levels of cyanobacteria in all of the areas where we test.

Cyanobacteria can cause health effects whether or not toxins are present.

When cyanobacteria reproduce exponentially, they can produce cyanotoxins in high concentrations, which the US Centers For Disease Control and Prevention says are among the most powerful poisons known.

Specific triggers are not clear, but HABs occur more often under certain conditions:

  • Slow moving or still water
  • Sunlight
  • Abundance of nutrients

Of the three ingredients, the only thing that we can control on Lake George is the amount of nutrients being added to the Lake. We all need to stop allowing nutrients to flow into the Lake in order to protect the Lake’s water quality and, hopefully, prevent another HAB from forming.

In the meantime, we encourage residents to follow the DEC’s guidance (on.ny.gov/hab) to Know it. Avoid it. Report It.


HABs vary in appearance, and may not necessarily be deep green. Colors can include shades of green, blue-green, yellow, brown, red, or white. It can appear as anything from scattered dots or clumps in the water to long, linear streaks on the water’s surface, pea soup or spilled paint. The bloom is made more evident as it concentrates on the surface of the Lake as a scum or a mat.


It is hard to tell a harmful algal bloom from a non-harmful bloom, so it is best to avoid swimming, boating, fishing or other recreation in discolored water that looks like it might have a bloom. Avoid eating fish caught from areas with a bloom. Never drink, prepare food, cook, or make ice with untreated surface water, even if there is no visible bloom.


If you suspect a HAB on Lake George, please report it to the LGA and through the NYHABS online reporting form available on DEC’s HABs web page at on.ny.gov/hab.

Questions & Answers

Q: What happened?

A: Harmful Algal Bloom was recorded in November 2020 as having formed on Lake George for the first time.

Q: What does that mean?

A: Lake George historically has never had a HAB. It means that for the first time, the conditions were right (slow moving or still water, sunlight, abundance of nutrients) for natural cyanobacteria in the Lake, identified as Dolichospermum, to have bloomed. DEC calls Dolichospermum a common cyanobacteria found in HABS in other Lakes in New York State.

Q: Lake George has cyanobacteria?

A: Yes. Because Lake George is a natural lake, it has various forms of microscopic life, including cyanobacteria. Our water quality monitoring program shows the extent of it in recent years.

Q: What was the extent of the bloom? Where was it located?

The LGA staff first saw a Harmful Algal Bloom along the shoreline on the east side of Assembly Point and in Harris Bay — DEC has confirmed the bloom there. Additional blooms appeared in Harris, Sandy & Warner Bay and near shore waters off of Lake George Village. Photo evidence sent to the LGA shows that Lake George also experienced a Harmful Algal Bloom confirmed by DEC) at Clay Island in late October.

Q: What is the LGA doing?

A: We will continue our lakewide observations with our partners, working with the state DEC and have revised our action plans and project plans for 2021 and beyond to ensure we are doing everything we can to stop nutrients from polluted stormwater and elsewhere from getting into the Lake.

Q: What can I do?

There are a number of easy steps that anyone can do (or in some cases, not do) to prevent nutrients from getting into the Lake.

  • Don’t blow or rake leaves into the Lake or streams
  • Stop using fertilizer in the watershed
  • Get your septic system inspected, fix it if it is failing
  • Plan to install a rain garden or shoreline buffer to capture polluted stormwater
  • Keep storm drains clear of debris
  • Join us or renew your membership: membership support allows us to protect the Lake

We’ve all got to act now if we want to protect the water quality of our Lake.

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All the money raised by the Lake George Association goes to projects and programs that benefit the Lake and the watershed, protecting Lake George water quality now and in the future.
Lake George Association

Lake George Association