A nearly 10-mile-long ribbon of "red tide" has been spotted on Monday in New York harbor, the National Broadcasting Company (NBC) reported on Monday.

The "red tide" -- an accumulation of bacteria whose dense concentration turns the affected water a reddish brown color -- was found early Monday in New York Harbor and also in the Long Island Sound near Jones Beach inlet, according to the NBC report.

The algae concentration is moving from north to south, slowly drifting down the harbor and out to sea. The red tide stretches down the Hudson from the USS Interepid Museum in Manhattan to Hoffman Island off Staten Island.

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 recommend boaters and swimmers avoid the red tide and thoroughly wash all articles that come into contact.