In 2025, the Hudson River Estuary experienced a harmful algal bloom (HAB), likely driven by regional drought, warm water, calm conditions, and nutrients. As summer 2026 begins, we are reaching out to share information and help communities prepare in case of a HAB event.
HABs in freshwater (lakes, ponds, rivers, and streams) generally consist of visible patches of cyanobacteria, also called blue-green algae. Under certain conditions, cyanobacteria may multiply rapidly and form blooms that are visible on the surface of the affected waterbody. Several types of cyanobacteria can produce toxins and other harmful compounds that can pose health risks to people and animals through ingestion, skin contact, or inhalation.
When it comes to HABs, DEC encourages New Yorkers to “KNOW IT, AVOID IT, REPORT IT.”
KNOW IT – HABs vary in appearance, from scattered green dots in the water, to long, linear green streaks, pea soup or spilled green paint, to blue-green or white coloration.
AVOID IT – People, pets, and livestock should avoid contact with water that is discolored or has algal scums on the surface.
REPORT IT – If you suspect a HAB, report it through the NYHABs online reporting form available on DEC’s website. Symptoms or health concerns related to HABs should be reported to DOH at harmfulalgae@health.ny.gov.