Several Palm Beach County, Florida beaches have been closed due to high bacteria, seen here on Delray Beach on Wednesday (August 31), ahead of the significant Labor Day holiday.

The county health department has ordered lifeguards to hoist the red no-swimming flag at the beaches, which won't reopen to swimming until they receive a positive test that the bacteria count has returned to acceptable levels. High bacteria counts can be caused by many factors including sewage leaks and spills, runoff after heavy rains and wildlife. For most of the summer, South Florida beaches have also been plagued by wide and thick layers of sargassum seaweed.

Experts say a warming sea and excess nutrient run-off from the land have contributed to the sargassum mega bloom. For more information, contact the Palm Beach County Health Department at 561-671-4014. The county website also has a news release regarding the beach closures.

Here's a sign no one wants to see just before the Labor Day Holiday: Beach Closed Due to High Bacteria Count. But that's exactly the status of six beaches -- including Delray Beach, which is shown in this video -- tested for bacteria in Palm Beach County, Florida. The county health department has ordered lifeguards to hoist the red no-swimming flag at the beaches, which won't reopen to swimming until they receive a positive test that the bacteria count has returned to acceptable levels. High bacteria counts can be caused by many factors including sewage leaks and spills, runoff after heavy rains and wildlife. For most of the summer, South Florida beaches have also been plagued by wide and thick layers of sargassum seaweed. Experts say a warming sea and excess nutrient run-off from the land has contributed to the sargassum megabloom. For more information, contact the Palm Beach County Health Department at 561-671-4014. The county website also has a news release regarding the beach closures.