Our Response to the Lake George HAB Event

Download our press release: PDF iconJefferson Project Deploys State-of–the-Art Science and Technology to Understand Lake George’s FIRST Harmful Algal Bloom



Joining together world-class scientists and engineers, lake surveys, advanced sensors, and computer models to document the event and understand the underlying causes.


What was observed?

During a period of warm, calm days from November 7-9, a surface film of algae appeared in four locations in the lake:  Harris Bay, Sandy Bay, Warner Bay, and near Lake George Village. The “suspicious blooms” were visually identified by a citizen scientist who alerted the Lake George Association (LGA), which contacted the NY Department of Environmental Conservation (DEC) to determine if the blooms could be categorized as “confirmed blooms” (HABs).


A water sample was collected at each location for testing by DEC, and the Jefferson Project team collected a water sample from the algal bloom at Harris Bay and sent it to a national laboratory for testing.


Research Scientist Joel Harrison measuring water temperature, oxygen, pH, and algae           View from the DFWI dock on Tuesday, November 10th   

Laboratory tests are done to confirm:

  • which algal species is dominant in the bloom,
  • whether the concentration of the algae is high enough to be categorized by DEC as a “confirmed bloom,” and,
  • whether there are toxins present and, if so, whether the toxins are at a concentration that poses a risk, which is categorized by DEC as a “confirmed bloom with high toxins.”


Deploying a vertical profiler on Tuesday, November 10th                                         Research Specialist Candace Schermerhorn driving back to DFWI


How is the Jefferson Project research team helping?


In seven years of monitoring the lake, the Jefferson Project has built a comprehensive dataset that tracks the weather, runoff, and circulation of water in the Lake George basin, and the species of plants, animals, and algae that live in it. With the discovery of the HABs in Lake George on Monday, November 9, the Jefferson Project immediately assembled its team of more than 20 researchers to develop and execute a research plan aimed at understanding the cause of the HAB. This JP Research Plan comprises five major research activities:

  1. Deploy an advanced sensor platform to Middle Bay (just north of Harris Bay, Sandy Bay, and Warner Bay) to monitor changes in the water column.
  2. Deploy a second sensor platform to Calves Pen, to monitor changes in the water column at a deeper site.
  3. Conduct lake surveys at 37 sites around the south basin to monitor physical parameters, algal abundance, algal composition, and nutrient abundance (i.e. phosphorus, nitrogen), and algae.
  4. Run computer models to understand the roles of weather and lake circulation may have played in causing the HABs.
  5. Conduct analyses comparing current versus past lake conditions.

              Bottles prepped to collect surface phytoplankton samples                                         Phytoplankton sample from the DFWI dock on Monday, November 9th

What do we know so far?

Saturday, Nov. 7: 

Suspicious Bloom first noticed in Harris Bay. It dissipated later that day. The Lake George Association first reported the bloom to DEC based on the assessment of a staff member who had been trained in HAB identification as part of the DEC’s Citizens Statewide Lake Assessment Program.


Monday, Nov. 9:

Suspicious Blooms observed in Harris Bay, Sandy Bay, Warner Bay, and at the southern end of the lake near Lake George Village. LGA and JP staff collected water samples. All blooms dissipated later that day.


Thursday, Nov. 12: 

NYS DEC confirms the dominant algae is in the genus Dolichospermum.

JP sample (Greenwater Labs) confirms the dominant algae is the species Dolichospermum fuscum.


Friday, Nov. 13: 

NYS DEC announces a Confirmed Bloom in Harris Bay with no detectable toxins. DEC tests found toxin levels safely below the Environmental Protection Agency’s 10-day drinking water health advisory level of 0.30 micrograms per liter.

No confirmation of a HAB in Sandy Bay, Warner Bay, and Lake George Village.


Wednesday, Nov. 18:

JP water sample was tested for four known toxins produced by the dominant algae and found them to be “non-detectable.”



What are the Jefferson Project’s next steps?

To understand the underlying causes of the confirmed and suspicious HABs, the Jefferson Project team is addressing two overarching questions:

  1. Were the confirmed and suspicious HABs that were observed in various locations produced in those locations or transported by surface currents to those locations?
  2. Was this an unusual natural event and/or was it somehow connected to human activities?


To answer these questions, the Jefferson Project research team is rapidly moving forward on the following research efforts:

  1. Completing our nutrient testing of more than 70 water samples from three surveys around the south basin conducted immediately after the confirmed HAB event
  2. Identifying algal composition of more than 70 water samples from three surveys around the south basin conducted immediately after the confirmed HAB event
  3. Assessing any changes in nutrient concentrations and algal composition across the three surveys in the south basin after the confirmed HAB event
  4. Continuing analysis of vertical profiler data on physical measurements (i.e. water-column profilers of temperature, dissolved oxygen, pH, turbidity, etc.)
  5. Assessing the history of algal dynamics during the fall based on JP monitoring to total chlorophyll and phycocyanin (i.e. a measure of cyanobacteria) levels
  6. Assessing historic Dolichospermum fuscum (the species of cyanobacteria of the confirmed HAB) abundance in the lake, going back several decades
  7. Identifying eight years of algal samples (2013-2020) to determine the typical populations of Dolichospermum in the lake during the fall
  8. Improving and validating the JP circulation model in the areas where the HABs occurred to determine how surface currents may have moved the algae
  9. Assessing historic weather conditions to characterize weather conditions at or around the time of the HAB events (e.g. to quantify the rarity of the calm, warm weather that occurred during the HAB event)
  10. Examining satellite images of the region before, during, and after the HABs using remote sensing
  11. Designing a plan for assaying sediment nutrients and akinetes (cyanobacteria resting stages).


The multi-faceted approach of the Jefferson Project research team is intended to understand the underlying causes of the confirmed and suspicious HABs on Lake George. This holistic approach requires a large number of researchers and several months to acquire and analyze all of the data, but this approach will allow us to provide the most complete understanding of the event.


The Jefferson Project is committed to sharing its discoveries with the public.


What is a harmful algal bloom?

A harmful algal bloom (HAB) is a dense concentration of cyanobacteria (also known as blue-green algae) in the water that can be considered harmful due to toxins and aesthetic, economic, or ecological impacts. HABs are typically identified by a dense film of floating algae on the surface of the water.



Photo from the Lake George Association, distributed after their discovery on Monday, November 9th


Some species of cyanobacteria produce toxins under some conditions. However, it remains unclear to scientific experts when and why the cyanobacteria produce these toxins. As a result, any given HAB may or may not cause toxins to be in the water. The toxins span a wide range of chemicals, including liver toxins, nerve toxins, and skin irritants. More information on the toxins can be found on the CDC website.


The NYS DEC has three categories for HABs: 

  • Suspicious Bloom – Visual observation of an algal bloom by a trained observer
  • Confirmed Bloom – Cyanobacteria concentration exceeds 25 ug/L
  • Confirmed Bloom with High Toxins– Cyanobacteria concentration exceeds 25 ug/L and a concentration of toxins above a given threshold

You can learn much more about HABs at the NYS DEC website.