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Harmful Algal Bloom Updates

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  • 08/01/2021 2:40 PM | Kaitlin Fello

    We will provide some photos in each Bloom Watch to help everyone better identify blooms.

    This week, we contrast blooms with another phenomenon. The photo on the left was taken this year in a small tributary that was blocked from entering Keuka Lake. It is NOT a cyanobacteria bloom. The green splotches are a macro algae, commonly seen in stagnant water such as ditches.  The photo on the right is a cyanobacteria bloom (HAB) from Seneca Lake last year.


    Key differences are:

    • Macro algae is 3-dimensional, that is it can be puffed above the surface and dangle below the surface. HABs are usually very 2-dimensional and appear flat.
    • Macro algae is a heavy mass and sticks together. HABs are very easy to break apart (with a stick, not hands). 
    Do not put your hands in a bloom. Blooms are most often mainly green, but can take on some other colors. They can appear as streaks, blotches, dots, or scum.
  • 08/01/2021 2:33 PM | Kaitlin Fello


    Observation Dates: Thru 7/29/2021
    % Zones Monitored: NA
    Suspicious Blooms:  0
    Confirmed Blooms:  0

    Our 120+ volunteers are finishing up training and ready to start the season. Volunteers are monitoring the lake now, but the “official” monitoring period does not start until August 2nd. This year the official monitoring will run through October 10th, although many volunteers will continue searching and reporting until October 31st.

    Pure Waters has updated its HAB website ( for 2021. There is a real-time bloom scorecard that tabulates the number of reported blooms on the lake “today”, “this week”, and “last week”. The 2021 map is also up. As always, there is background information and links for more details.

    In early July, Pure Waters received a few inquiries concerning dead fish in the water. Fish die off every year, but sometimes there are more than normal. Based on the information received, the situation seemed normal for Seneca Lake. However, Canandaigua Lake saw a bigger die off, so our partners, the Canandaigua Lake Watershed Association (CLWA), contacted the NYS Department of Environmental Conservation (DEC). The next article was a summary the CLWA sent in a recent communication (reprinted with permission).

    Fish Die Off Events

    CLWA and the Canandaigua Lake Watershed Council fielded several calls from early to mid-June regarding increased numbers of dead fish found along shorelines. While we typically might see some die off in late spring brought on by factors such as post-spawning stress, rapidly increasing water temperatures, and ecological changes in the food web, this spring’s die off was more sustained. DEC Region 8 Fisheries staff was contacted to investigate and samples were collected and brought to Cornell Veterinary School for analysis.

    DEC Region 8 Fisheries provided the following update:

    DEC investigated recent reports of a fish die-off affecting rock bass, sunfish, smallmouth bass, and white sucker in Canandaigua Lake. Samples were obtained from impacted white sucker and smallmouth bass for analysis at the Cornell Veterinary School.

    Results came back showing an infection of the bacteria Aeromonas. Aeromonas is commonly found in water and by themselves, are not a concern. DEC suspects that the warmwater fish in Canandaigua Lake became stressed from spawning, temperature swings, or some other stressor. This resulted in their immunity being lowered and allowed the bacteria to infect the fish. Aeromonas does not pose a threat to humans or pets utilizing Canandaigua Lake.

    As always, people should not drink unfiltered lake water and obviously sick fish should be avoided. If stressed or dead fish are handled, people should wear gloves or wash their hands with soap and water after. With proper preparation, healthy fish are safe to eat. People should continue to report large numbers of dead fish to DEC at 585-226-5343 or

  • 07/16/2021 9:25 PM | Kaitlin Fello

    Exposure to any cyanobacteria HABs can cause health effects in people and animals when water with blooms is touched, swallowed, or when airborne droplets are inhaled. This is true regardless of toxin levels; some blue-green algae produce toxins, while others do not. Exposure to blooms and toxins can cause symptoms such as diarrhea, nausea or vomiting; skin, eye or throat irritation and allergic reactions or breathing difficulties.
    Because blue-green algal bloom conditions change rapidly over time, the best prevention is to take steps to avoid waters with visible blooms: 

    • People, pets, and livestock should avoid areas with blooms or surface scums, or water that is noticeably discolored. 
    • Avoid blooms when swimming, boating, fishing, and don’t eat fish caught from areas of water with blooms.
    • If you or your pets are exposed to blue-green algal blooms, stop using the water and rinse off with clean water.
    • Consider medical attention for people and animals if symptoms such as diarrhea, nausea, or vomiting; skin, eye, or throat irritation; and allergic reactions or breathing difficulties occur after contact with surface waters with blooms.
    • Never drink untreated surface water. Even if you treat it in your home with water filtration, chlorine, ultraviolet (UV) light, or other treatment; it’s still not protected from blue-green algae and toxins.

    If you would like to see where HABs are occurring in NY State, visit the DEC Website at  Their map is here.

  • 07/16/2021 8:49 PM | Kaitlin Fello

    On a recent trip to the northwestern side of the lake, a familiar and unpleasant note was in the air; the smell of dying Cladophora, a nuisance algae. With the reign of the Cladophora at an end we now find ourselves in the season of the Cyanobacteria.

    The algal community is diverse. As the chemical, physical, and biological conditions in the lake change over time, the composition of this community changes as well. Some species thrive and multiply under specific conditions found at certain times of year while others struggle to survive. This ebb and flow is referred to as algal succession and is an important ecological characteristic of the lake.  

    Green algae such as Cladophora tend to thrive during the early summer period. These are proceeded by Cyanobacteria; also known as blue green algae (BGA). Cyanobacteria can produce harmful algal blooms (HABs), which are the focus of Bloom Watch. Both are natural and important components to the health of the lake. However, excessive amounts of either can negatively impair waterways as many of you are aware of.  

    Understanding the conditions that lead to this excessive growth is still a subject of research, but elevated nutrient levels and the presence of dreissenid (zebra and quagga) mussels, are commonly implicated as primary drivers for both Cladophoraand BGA. Addressing these drivers is an ongoing and long-term challenge made more complex by additional factors, yet we must rise to it and work towards the goal of a healthier Seneca Lake.

  • 07/16/2021 8:44 PM | Kaitlin Fello

    Observation Dates: Thru 7/15/2021
    % Zones Monitored: NA
    Suspicious Blooms:  0
    Confirmed Blooms:  0

    Our 120+ volunteers are finishing up training and ready to start the season. Volunteers are monitoring the lake now, but the “official” monitoring period does not start until August 2nd. This year it will run through October 10th, although many volunteers will continue to monitor until October 31st.

    Many of you will remember that we did not see many blooms on Seneca Lake last year. There were only 7 days where blooms were observed, and only one day when blooms were found in more than two locations (August 31st). The lack of blooms in September was particularly strange, since that is when we typically have the most blooms.

    While Seneca Lake had few blooms, nearby lakes had record years. Given that conditions were basically the same in all the lakes, e.g., dry, warm water, low water level, windy, etc., it is a mystery why Seneca Lake experienced so few blooms. We are confident that we didn’t miss many as our dock-mounted cameras did not detect blooms either. The cyanobacteria continue to surprise us, all the more reason we need to remain vigilant.

    Seneca Lake typically sees HABs starting in mid-August, peaking the first 3 weeks of September, then fading into late October as the water gets colder. There could be blooms earlier, but to date, they seem rare. Interestingly, the HABs tend to start just after the surface water temperature peaks.

    Pure Waters is updating its HAB website ( for 2021. There will be a real-time bloom scorecard that will tell you if there are reported blooms on the lake “today”, “this week”, or “last week”. The 2021 map will be up soon. As always, there is background information and links for more details.

    Now that the Cladophora is decaying and the water is clearing up, we can expect HABs to form. Please be alert. The follow up article titled "A change is in the Air", is a repeat from last year about this summertime change in the lake’s biology is from Ian Smith, our Seneca Lake Watershed Steward. 
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Seneca Lake Pure Waters Association

P.O. Box 247

Geneva, NY 14456


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