Harmful Algal Blooms (HABs) - Prospect Park Alliance
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Harmful Algal Blooms (HABs)

Harmful Algal Blooms (HABs) are produced by naturally occurring cyanobacteria in lakes and ponds, including the Prospect Park Lake and other bodies of water in the NYC area. While they usually exist in low numbers, this type of algae can bloom during the summer months, which gives the water the appearance of pea soup, a green paint spill, or thin blue or green mats floating on the surface or along the shoreline. 

HABs can cause skin and eye irritation from external contact, asthma-like symptoms from inhaling water or spray, and gastrointestinal and neurologic symptoms from ingestion. Children and pets are more vulnerable to these effects. Because blooms can be hard to identify, park visitors must avoid contact with any algae and heed all posted signage.

Prospect Park Alliance is working closely with NYC Parks and the New York State Department of Environmental Conservation to test the biology of Prospect Park’s watercourse to monitor for blooms. Recent tests have indicated the presence of blooms in the Lake, but not at Dog Beach.

Recently, the Alliance received a grant to create a natural filtration system to stem the growth of algae blooms. Learn more about our plans to combat algae blooms.

Where can dogs swim?
To minimize the risk of exposure to blooms, the Lake has been closed to dog swimming, Dog Beach currently remains open and will be monitored on a weekly basis. Please continue to check this website for updates as environmental conditions may change the presence of algal blooms.

Where can you fish?
Fishing information, including permitted fishing locations, can be found on our Fishing page.

Tips to avoid Harmful Algal Blooms

  • Never drink, swim or wade in any the Prospect Park Lake and other waterbodies. 

  • Watch children at all times and do not allow them to enter or drink from lakes or ponds.

  • Keep pets on leashes. Do not allow them to enter or drink from lakes and ponds unless in areas specifically designated for such activities.

What to do if exposure occurs
If a person or pet is exposed to a blue-green algae bloom, rinse with clean water. Seek medical attention if symptoms such as skin, eye or throat irritation; allergic reactions or breathing difficulties; nausea, vomiting, diarrhea, dizziness, headache or fever occur. Please report the symptoms to the New York City Department of Health and Mental Hygiene by calling 311.

For more about algal blooms, visit the NYC Parks website.