Director’s Note: The Great Atlantic Sargassum Belt and potential impacts to our region

There has been quite a bit of news lately about the Sargassum “blob” that is currently impacting portions of the Caribbean, the Florida Keys, and Florida’s east coast. To understand this in greater detail, it’s important to differentiate between the Sargasso Sea and the Great Atlantic Sargassum Belt. The graphic below can help you understand the differences between these two “centers of abundances” for this floating brown seaweed.

There are four major species of brown seaweeds within the genus Sargassum that are found in Florida. Two of them grow attached to the bottom and two of them are free-floating. The two free-floating species are the ones of concern here. Christopher Columbus and other early explorers documented an area of abundance of free-floating Sargassum in a gyre in the mid-Atlantic that was subsequently termed the Sargasso Sea. That is different from the Great Atlantic Sargassum Belt, which is the new center of abundance that is such a concern for us and our neighbors. About a decade ago, researchers believe that shifting winds and surface currents brought a large mass of this brown seaweed from the Sargasso Sea eastward to Gibraltar. Subsequent months moved this mass of seaweed southward along the Canary Current to the west coast of Africa.

The plants within the Sargasso Sea are physically isolated from most land-based nutrient loads, and while seaweed from the Sargasso Sea has always traveled to our coast via the Antilles Current, these were mostly not huge masses for us to deal with. Thirty years ago, while surfing and fishing and working on Florida’s east coast, I would find Sargassum all the time, but never at abundances that kept me or other beach goers out of the water. But the plants that are now growing in the Great Atlantic Sargassum Belt – these plants are being fertilized via coastal upwelling off the African coast, runoff from West African Rivers, and also runoff from South America’s Amazon and Orinoco Rivers. And then these masses of plants are carried into the Gulf of Mexico via the Caribbean and Yucatan Currents where they can furth