The ocean may be toxic off NC beach town, officials say. What’s behind warning?
UPDATE: The Atlantic Beach swim advisory was lifted Sept. 5 when the algae blooms moved away from the beach. “Swimmers and visitors are encouraged to still exercise general safety precautions. Avoid discolored water or areas with unusual odor,” city officials wrote in a news release.
The original story is below.
One of North Carolina’s most popular beach destinations is telling people to avoid the ocean, due to a foul smelling “brown sheen” that can be toxic.
Atlantic Beach on the state’s Crystal Coast issued a swim advisory Thursday, Sept. 4, after an investigation revealed the substance is made up of microscopic creatures known as called Trichodesmium.
The repulsive slicks formed by colonies of bacteria are sometimes referred to as “sea sawdust,” town officials wrote in a Facebook post.
“While Trichodesmium is an essential component of marine ecosystems, it is not suitable for human consumption. Ingesting or touching Trichodesmium colonies can cause skin irritation and, in some cases, lead to respiratory problems due to the release of certain toxins and irritants. It is advised to avoid direct contact,” the town said.
“A swimming advisory remains in effect for Atlantic Beach until these blooms have cleared the area. As a general safety precaution, avoid discolored water or areas with unusual odor. Rinse thoroughly with fresh water if contact occurs”
The advisory includes a warning to keep pets away from the slicks near the shoreline.
The blooms are known to “cover stretches of ocean surface” when conditions are right, including calm seas, low wind speeds, and warm water temperatures, officials said.
Atlantic Beach began posting alerts Sept. 4, after learning of “a brown sheen with a foul smell” was makings swimmers ill, including “minor eye and/or skin irritation,” officials said.
At that time, the mat was about a quarter of a mile long and extended out a mile off the beach, officials said.
Atlantic Beach is about a 150-mile drive southeast from Raleigh.
This story was originally published September 5, 2025 at 7:19 AM.