Authorities have found "red tide" -- an accumulation of bacteria whose dense concentration turns the affected water a reddish brown color -- in New York Harbor and also in the Long Island Sound near Jones Beach inlet.
The algae concentration is moving from north to south, slowly drifting down the harbor and out to sea. The naturally occurring algae bloom is a common event in coastal waters throughout the world, the Coast Guard said in a release.
The red tide stretches down the Hudson from the USS Interepid Museum in Manhattan to Hoffman Island off Staten Island, some 9.5 miles, officials said.
This phenomenon is a potential health hazard to boaters and swimmers if they ingest tainted water. The concentrated algae also can deplete oxygen in affected waters resulting in fish kills.
The New Jersey Department of Environmental Protection and the Hudson Regional Health Commission recommends boaters and swimmers avoid the red tide and thoroughly wash all articles that come into contact.