Is Black Lake safe? Toxic algae status
St. Lawrence County, New York. Harmful algal bloom (blue-green algae) reports from the New York State Department of Environmental Conservation (DEC).
Data checked 24 October 2026. New York data is published as a yearly summary; the current season is shown on the NYHABS map.
13 of 14
years on the state's bloom list (2012–2025)
4
years with a confirmed high-toxin bloom (recorded 2012–2018)
2012
first year a bloom was listed
Year by year
Each year the lake appeared on the state bloom list, with its highest status.
Reports at Black Lake are most often logged in April, July and August.
Recent reports
| Date | Result |
|---|---|
| 10 July 2025 – 23 September 2025 | Confirmed bloom |
| 21 July 2024 – 10 September 2024 | Confirmed bloom |
| 16 July 2023 – 25 August 2023 | Confirmed bloom |
| 7 July 2022 – 12 September 2022 | Confirmed bloom |
| 17 June 2021 – 17 September 2021 | Confirmed bloom |
| 1 July 2020 – 22 August 2020 | Confirmed bloom |
| 16 August 2019 | Confirmed bloom |
| 8 April 2017 – 13 October 2017 | Confirmed bloom |
| 15 July 2016 – 27 October 2016 | Confirmed bloom |
| 21 August 2015 – 2 October 2015 | Confirmed bloom |
| 29 July 2014 – 20 October 2014 | Confirmed bloom, high toxins |
| 11 July 2013 – 8 August 2013 | Confirmed bloom, high toxins |
What the results mean
Reported to the state but not yet confirmed as blue-green algae.
State staff confirmed a blue-green algae bloom from photos or samples. Avoid contact with the water where the bloom is.
Toxin levels high enough to be a health concern. Recorded separately in the 2012–2018 data.
Dogs and toxic algae
Dogs face the greatest risk because they swallow water and lick algae off their fur. If a bloom has been reported, keep dogs out of the water and away from scum on the shore. If your dog swims in water that might have algae, rinse it with clean water straight away and call a vet if it seems unwell.
Common questions
Is Black Lake safe to swim in?
The most recent entry in New York's published data is from 10 July 2025: confirmed bloom. Blooms have been recorded at Black Lake in 13 different years, so treat green, scummy or discoloured water with caution. For current conditions, check the NYHABS map and posted signs.
When does Black Lake get algae blooms?
In the state's records, reports are most often logged in April, July and August. Blooms are most likely in warm, calm weather, but they can appear at other times of year.
Source: New York State Department of Environmental Conservation (DEC), official data. This page is independent and not affiliated with the State of New York.