Seneca Lake and Cyanobacteria Blooms

During the months of August and September, volunteers monitor the shorelines of Seneca Lake for cyanobacteria blooms.

The laboratory analysis of CyanaoHABs blooms, collected at the north end of Seneca Lake during the month of September 2019 contained alarming levels of microcystin.  Microcystin is produced by several genera of cyanobacteria and may cause skin irritations, allergic reactions or gastrointestinal illnesses.

Are cyanobacteria regulated contaminants in drinking water or in recreational water bodies?

No, cyanobacteria and the cyanotoxins they may produce are not currently regulated by the federal government or New York State. However, the US Environmental Protection Agency (US EPA) has issued guidance for issuing Health Advisories due to potential health concerns.  It is important to realize that these guidance levels are not enforceable regulations.

EPA Drinking Water Health Advisory:

EPA Draft Recreational Ambient Water Quality Criteria for Swimming Advisories for Microcystin

Reducing CyanoHABS:

According to the NYSDEC website:

The public and lake residents can do their part to reduce the likelihood of algae blooms by reducing the addition of nutrients (phosphorus and nitrogen) to waterbodies. The amount of nutrients can be decreased by:

  • Limiting lawn fertilization
  • Maintaining septic tanks
  • Installing and maintaining shoreline buffers
  • Reducing erosion and stormwater runoff
  • Improving water movement

2018 HABs Summary

Water Samples collected from Suspicious Blooms
and submitted to lab for analysis
Confirmed Blooms:
test results exceed 25 µg/L Bluegreen Chlorophyll 
Confirmed Blooms with High Toxins:
test results exceed test results exceed of 20 µg/L Microcystin

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