Sargassum is a genus of large brown algae that includes over 300 species. Two prevalent species in the Atlantic Sargassum natans and Sargassum fluitans, are found in free-floating mats, held afloat by gas-filled bladders.

Hawksbill turtle, one of the critically endangered animals that uses Sargassum as habitat  ( Photo : Amy Cox )

This floating habitat provides food and protection for fishes, mammals, marine birds, crabs, and more. It serves as a critical habitat for threatened loggerhead sea turtles and as a nursery area for a variety of commercially important fishes such as mahi mahi, jacks, and amberjacks.

Various marine life above and below the water rely on floating mats of Sargassum (NOAA 2014).

Starting in 2011, floating Sargassum began to impact coastal communities around the Atlantic.

Sargassum distribution in the Atlantic Ocean 2011-2018 (Wang et al. 2019)

Once confined to the Sargasso Sea, recent studies suggest that changing wind patterns has caused Sargassum to proliferate across the tropical Atlantic (Johns et al. 2020). Thousands of tons of Sargassum end up on beaches in the Caribbean, Americas, and West Africa. It releases gas that smells like rotten eggs, which attracts flies, deters tourists, and causes respiratory problems. Mounds of algae on beaches and dense mats in the ocean harm marine ecosystems and disrupt recreation and fishing, costing local communities millions of dollars. Removal and containment efforts are often expensive and puts marine life at risk.

Sargassum transport throughout the Atlantic Ocean after the 2009-2010 North Atlantic Oscillation (NAO) anomaly (Johns et al. 2020)

Research on other mechanisms behind the Sargassum spread is ongoing.
This is a social, economic, and ecological challenge that requires a multi-disciplinary approach to manage current and future Sargassum beachings.