Saharan dust can fuel conditions for red tide

Is there a Saharan dust — Trichodesmium — red tide connection?

According to the Florida Fish and Wildlife Research Institute, reports of a bloom of Trichodesmium have been reported in Southwest Florida. FWRI biologists verified a bloom offshore of Pinellas County on Monday, June 22. Trichodesmium is a marine cyanobacterium (blue-green algae) found in tropical and subtropical waters that blooms every year off the coast of Southwest Florida, forming miles-long patches visible from satellite imagery.

The offshore waters of the Gulf of Mexico are known to be poor in nutrients, such as nitrogen, which is essential for plant growth. A survival strategy of Trichodesmium is that it can fix atmospheric nitrogen and use it to grow. This process can be stimulated by iron availability.

Typically, between June and August, iron-rich dust blows from the Sahara Desert across the Atlantic and settles in the Gulf of Mexico, fueling Trichodesmium blooms during these months.

Reports of Trichodesmium blooms date back to the 1700s, when Capt. James Cook of the British Royal Navy wrote about large, brown patches on the surface of the water that resembled sandbars.

During late summer or fall, red tide (Karenia brevis) blooms begin developing 10 to 40 miles offshore.

Red tide cells use nutrients generated by Trichodesmium blooms for their own growth, but complex atmospheric and oceanic circulation patterns make predictions difficult.

As expected during this time of year, current red tide monitoring shows “Not present/Background” levels of red tide cells in collected water samples.

Follow the FWC Research Institute red tide monitoring efforts by checking the daily sample map, online at

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