sargassum weed

Sargassum is a genus of over 350 species of brown algae. These algae can be found attached to rocks in temperate, subtropical, and tropical coastal areas, or as free-floating masses in the open sea. The Sargasso Sea in the Atlantic Ocean is named for these floating Sargassum species.1

Physically, Sargassum has a branched, bushy body with numerous hollow, berry-like floats called pneumatocysts that aid buoyancy. Its fronds are typically small and oval-shaped with toothed edges. While most species attach to substrates, some, like Sargassum natans and S. fluitans, live their entire lives floating freely and reproduce by fragmentation.1

Floating Sargassum mats create unique open-ocean habitats, supporting diverse marine life by providing food and shelter. However, when large quantities wash ashore, they can negatively impact tourism due to decomposition odors and can harm coastal ecosystems and marine life. Some Sargassum species are also used for food, medicine, and agriculture, and research is exploring their potential in various industries. Unusually large blooms, like the Great Atlantic Sargassum Belt, are linked to factors including nutrient input and climate change.1