The "widespread/lakewide" presence of high toxins in Prospect Park Lake from blue-green algae (BGA) blooms was confirmed by the New York State Department of Environmental Conservation through a lab sample on June 26th.
Blue-green algae is cyanobacteria. The bacteria can be harmful to people and to animals. Stay out of the lake, and keep children and pets out of it and away from it.
An undated announcement on the Prospect Park Alliance website states that
"Recent tests have indicated the presence of blooms near the Peninsula, but not at Dog Beach. Please continue to check this website for updates as environmental conditions may change the presence of algal blooms."
If people or animals are exposed to a bloom, wash the skin with soap and water or rinse thoroughly with clean water.
When the blooms are widespread, as they are in Prospect Park Lake, they can affect either the entire lake (as they're now doing), a large portion of the lake, or most to all of the shoreline.
A BGA bloom can make water look like pea soup or like green, blue, or red paint. Or, mats of blue or green pond scum can be floating on the water surface or might have accumulated along the shoreline.
Photos of the various appearances that the toxic blue-green algae blooms can have are posted on the New York State Department of Environmental Conservation (DEC) here.
The possible effects of the toxins on living creatures are nausea, vomiting, diarrhea, skin or throat irritation, allergic reactions, or breathing difficulties. The toxins can also affect the liver and nervous systems if a lot of water is swallowed.
Read more about this on the DEC's website.
If you believe you have been exposed to a bloom and are experiencing symptoms, get medical help immediately and contact the New York City Department of Health.