There have been observations along the Hudson River of late regarding harmful algal blooms. The Daily Freeman reported in today's edition (9/17/2025) about these occurences. The picture at the bottom of this page, of such a bloom in the Esopus Creek in Saugerties, comes from that article.
The following is from an email from Joe Ritchie, Advocacy and Policy Coordinator, Riverkeeper, September 15, 2026 ... with helpful advice.
Riverkeeper and a network of partners are currently monitoring and collecting data on a large, widespread harmful algal bloom (HAB) in the Hudson River Estuary. Based on observations to date, this appears to be the most extensive HAB in the estuary in living memory.
HABs can produce toxins that pose health risks to people, pets, and wildlife via ingestion, inhalation, or skin contact. The most common symptoms that may occur from exposure include skin rashes or stomach upset. Exposure to high concentrations of the more potent and rare toxins can damage the liver or neurological system. Dogs that swim in waters affected by HABs have died.
This HAB appears to be centered in the Hudson River in the vicinity of the Kingston-Rhinecliff Bridge. Recent reports suggest that the HAB has affected an area stretching from roughly Catskill/Hudson in the North, to Garrison/West Point in the south, including tidal portions of tributaries like the Rondout and Esopus creeks.. Not all areas within this reach may be affected, or affected to the same degree, and it is unknown how long the condition may persist.
What you can do:
- Pay attention to signs at all public waterfront access points. When in doubt, and in the presence of any visible algae in the water you are near, err on the side of caution at this time.
- Register for a virtual briefing on Friday, September 19th at 11:30AM to get critical updates from Riverkeeper experts on the current status of the HAB. Find out what Riverkeeper and our partners are doing to understand this event and prevent future HABs, and ask questions to a panel of experts.
- Avoid water contact on shorelines where a suspected HAB is present.
- Report any HAP obeservations to the NYHABS portal here, where you can also find information about HABS and a map of recent observations.
We thank you for your cooperation and please do not hesitate to reach out to Dan Shapley (dshapley@riverkeeper.org) for any questions.
From the 9/17/2025 Daily Freeman.