Why do the Great Sargassum Seaweed mats stay afloat in the Atlantic Ocean?

Sargassum is a free-floating brown seaweed that does not need to attach to the seafloor. Tiny air-filled sacs called pneumatocysts keep the algae buoyant at the surface, where it can receive light for photosynthesis. Large accumulations form the Sargasso Sea region of the North Atlantic, a unique habitat shaped by circulating currents. These floating mats support fish, turtles, crabs, and many other organisms that use them as shelter and feeding grounds. Sargassum blooms have attracted attention in recent years because currents and nutrient inputs can influence how much reaches coastal areas.