The Sargasso Sea is located entirely within the Atlantic Ocean and characterized by the presence of holopelagic Sargassum. Holopelagic Sargassum is free-floating algae that remains in the open ocean for its entire life cycle. No other marine region, anywhere in the world, is known to support a community of holopelagic algae.

The Sargasso Sea lies within the Northern Atlantic Subtropical Gyre where ocean currents define the Sargasso’s boundaries. The Gulf Stream establishes the Sargasso Sea’s western boundary, while the Sea is further defined to the north by the North Atlantic Current, to the east by the Canary Current, and to the south by the North Atlantic Equatorial Current.

The self-sustaining Sargassum serves a variety of functions for a diverse range of marine species throughout the Sargasso Sea. Turtles use Sargassum mats as nurseries where hatchlings have food and shelter. Sargassum also provides essential habitat for marine species, such as shrimp, crab, and fish, that have adapted specifically to this floating algae. The Sargasso Sea is a spawning site for threatened and endangered eels, as well as white marlin and dolphinfish. Humpback whales annually migrate through the Sargasso Sea. Commercial fish, such as tuna, and birds also migrate through the Sargasso Sea and depend on it for food.

The Sargasso Sea faces potential harm from a variety of sources. These sources include pollution from ship– and land-based sources and the harvesting of Sargassum for use as fertilizer and biofuels. The Sargasso Sea ecosystem also may be vulnerable to global threats such as climate change and ocean acidification.

The open-ocean ecosystem of the Sargasso Sea generally lies beyond the jurisdiction of any country. One exception is the portion of the Sargasso Sea surrounding Bermuda. Although Bermuda is undertaking various steps to protect the sea within its jurisdiction, improved protection of the Sargasso Sea requires international coordination. Such coordination is being pursued under international instruments such as the International Commission for the Conservation of Atlantic Tunas (ICCAT) offsite link and through organizations such as the Sargasso Sea Alliance offsite link.

The Sargasso Sea Alliance offsite link is an initiative to secure international recognition of and protection for the Sargasso Sea through the use of existing legal mechanisms and the support of governments and international organizations. This effort is led by the Government of Bermuda offsite link in coordination with scientists, international marine conservation groups and private donors. Four objectives guide the Alliance. These are:

• To build an international partnership that will secure recognition of the ecological significance of the Sargasso Sea and the threats that it faces,
• To use existing regional, sectoral and international organizations to secure a range of protective measures for all or parts of the Sargasso Sea to address key threats,
• To establish a management regime for the Sargasso Sea, and
• To use the process as an example of what can and cannot be delivered through existing institutions in areas beyond national jurisdiction.

Additional reference information: 

U.S. Resources

• South Atlantic Fishery Management Council, Fishery Management Plan for Pelagic Sargassum Habitat of the South Atlantic Region (2002)
• Rule to Implement Fishery Management Plan for Pelagic Sargassum Habitat of the South Atlantic Region, 68 Fed. Reg. 57375 (Oct. 3, 2003)
• NOAA Ocean Explorer, Sargassum: A Complex ’Island’ Community at Sea
• Partnership Between NOAA’s Stellwagen Bank National Marine Sanctuary and the Bermudian Government to Protect Humpback Whales in the North Atlantic

International resources

• Sargasso Sea Alliance offsite link
• International Commission for the Conservation of Atlantic Tunas (ICCAT) Resolution on Pelagic Sargassum

 Last updated September 8, 2020