Launched in 2018, the Cayuga Lake Harmful Algal Blooms (HABs) Monitoring Program is a collaborative initiative uniting local and state agencies, nonprofit partners, and community members. Together, participants collect actionable data on cyanobacterial blooms to protect public health and ensure timely, transparent communication of bloom conditions and test results.
Harmful Algal Bloom Monitoring on Cayuga Lake
Cayuga Lake Harmful Algal Bloom Monitoring Program
Have you observed a suspected Harmful Algal Bloom on Cayuga Lake?
If you observe a harmful algal bloom (HAB) on Cayuga Lake and are not one of CSI’s trained volunteers, you can submit a report using the 2026 Cayuga Lake Community HABs Report Form (the form will go live in spring/summer 2026).
Because HABs can form and dissipate rapidly, we encourage you to take several photos and submit your report the same day the bloom is observed, whenever possible. If you’d have additional questions or concerns, please send an email to HABsHotline@gmail.com.
What are Harmful Algal Blooms?
Despite the name “harmful algal blooms” (HABs) or “blue-green algae,” cyanobacterial blooms are not actually algae. They are bacteria—an ancient group of organisms that first appeared approximately 3.5 billion years ago, when Earth’s atmosphere contained little to no oxygen. As the planet’s first photosynthetic organisms and the ancestors of modern plants, cyanobacteria produced oxygen as a byproduct of photosynthesis. Over roughly 3.5 billion years, this process transformed Earth’s atmosphere and made it possible for oxygen-dependent life, including humans, to evolve.
Cyanobacteria are a highly diverse group with a wide range of forms and adaptations. Some genera can fix nitrogen, while others possess gas vacuoles that allow them to move vertically through the water column in search of favorable conditions. Many species also produce natural chemical compounds whose functions are not fully understood. A small subset of these compounds—known as cyanotoxins—are toxic to humans and other animals. The presence of these toxins is what makes certain cyanobacterial blooms harmful.
Under the right environmental conditions, freshwater cyanobacteria can grow rapidly, multiplying until they form visible blooms. In Cayuga Lake, three common bloom-forming groups are Microcystis, Dolichospermum, and Oscillatoriales. While these groups can be distinguished under a microscope, their blooms are indistinguishable to the naked eye. There is also no visual cue indicating whether toxins are present.
Cyanobacterial blooms can take many forms, ranging from green streaks or clumps on the water’s surface to a spilled-paint or pea-soup appearance; however, many non-harmful natural materials can look similar, making visual identification alone unreliable (see identification cards below, click to enlargen).
The Community Behind the HABs Monitoring Program – The HABs Harriers & Carriers
This program would not be possible without the dedication and collaboration of our volunteers, community members, and partners—Cayuga Lake Watershed Network, Discover Cayuga Lake, Nicholas Leonard Dronography, Cayuga County Health Department, Seneca County Health Department, Tompkins County Whole Health, and the New York State Office of Parks, Recreation and Historic Preservation—whose support made the 2025 season possible. Through your collective vigilance and commitment, we are learning not only when blooms occur, but how they behave—and how, together, we can continue to better understand and protect Cayuga Lake.
For more information about the 2025 season, please read the article “Reports vs. Reality: Refining How We Read Cayuga Lake’s Harmful Algal Blooms“ which is included in CSI’s 2025 Water Bulletin Newsletter.
Resources for Community Members, Residents, and Visitors
- 2025 Community Member Cayuga Lake HABs Report Form
- CSI Cayuga Lake HABs Database
- Subscribe to Cayuga Lake Watershed Network’s Weekly HABs Updates
- NYHABs Map
- NYSPark Beach Results Map
- Dogs & Harmful Algal Blooms -New York Sea Grant
- NYSDEC HABs Information Page
- Harmful Blue-green Algae Blooms: Understanding the Risks of Piping Surface Water into Your Home
- HABs Identification Training Video
- Harmful Algal Bloom Action Plan Cayuga Lake
We need your help!
In an effort to increase community participation and Cayuga Lakes shoreline monitoring coverage as the program continues to grow, we recruit new volunteers on an annual basis.
Interested in becoming a new volunteer?
Please fill this brief form out to get started!
Analyzing Harmful Algal Bloom Samples for Cyanobacteria
CSI Analyses: The CSI lab is equipped to perform three analyses on suspicious blooms: microscopy, total chlorophyll a, and microcystin. If initial inspection under the microscope confirms the presence of cyanobacteria, then chlorophyll a and microcystin analyses are performed.
- Microscopy: All samples received by the CSI lab are first assessed by microscopy, carefully looking at samples under the microscope, to characterize general bloom composition and determine if cyanobacteria are present in the bloom.
- Total Chlorophyll-a: If cyanobacteria are present, total chlorophyll a is used to estimate the biomass of the cyanobacteria bloom. Total Chlorophyll a is determined using spectrophotometry and results are reported in units of parts per billion (ppb) or micrograms/liter (ug/L).
- Microcystin: Cyanobacteria produce a variety of natural chemicals, a few of which are harmful to other species, including humans. The most common harmful chemical found in New York is microcystin.
- Detailed toxicity studies have not been performed, and there is not yet a consensus on acceptable exposure levels. The New York State Department of Health (NYSDOH) has set safe limits for public drinking water supplies at 0.3 ug/L and for public swimming beaches at 4.0 ug/L (EPA, 2017). The New York State Department of Environmental Conservation (NYSDEC) defines a “bloom with high toxin” as 20 ug/L near the shore and 10 ug/L in open water (NYSDEC HABs Program Guide, Section 3).
- Microcystin toxin is measured using EPA Method 546 which is an enzyme-linked immunosorbent assay (ELISA). CSI reports results down to the drinking water standard of 0.3 ppb (EPA, 2015).
