March 10, 2021


Header image: An expanse of Sargassum. (c) The Nonsuch Expeditions, JP Rouja

By Teresa Mackey, Programme Manager, Sargasso Sea Commission

The Sargasso Sea, a two million square nautical mile expanse of the North Atlantic, has long been an area famed for mystery and intrigue. Although sometimes referenced in popular culture in connection with the mythical ‘Bermuda Triangle’, for scientists around the world it is an area of interest due to its oceanographic history and the biodiversity of the high seas ecosystem. 

One mystery of the Sargasso Sea that continues to perplex scientists is the life cycle of the endangered European eel (Anguilla anguilla) and American eel (Anguilla rostrata). There is good scientific evidence that their spawning occurs in the Sargasso Sea, although the exact location has never been observed by scientists. Eel larvae (leptocephali) hatch at sea and migrate to Europe and the Americas in search of freshwater rivers and streams, where they will live until adulthood. Adult eels journey thousands of miles back to the Sargasso Sea, where they will spawn and subsequently perish. According to the International Union for Conservation of Nature’s Red List, this migration is the longest and most oceanographically complex of all the Anguillid species. 



Like the voyage of the eel itself, the journey to protect the unique high seas ecosystem of the Sargasso Sea has been a long process that began in the open ocean. Unlike every other named sea in the world, the Sargasso Sea is not constrained by land borders. Rotating currents border an expanse of deep azure water, where drifting mats of golden Sargassum are a haven for a vibrant array of marine life. Dr Sylvia Earle has long highlighted the importance of the Sargasso Sea as the “golden floating rainforest of the Atlantic”.


Kristina Gjerde, President of the Sargasso Sea Project, Inc. Board, snorkeling in Sargassum


In 2010, Mission Blue convened the first conference-at-sea to bring together policymakers, marine conservationists, and philanthropists and encourage a commitment to a better future for the ocean. One notable initiative launched on this voyage was the germination of an idea to protect the Sargasso Sea, one of Mission Blue’s first Hope Spots. Participants at the 2010 Mission Blue conference-at-sea pledged to launch a plan to support efforts already being undertaken by the Government of Bermuda to conserve the Sargasso Sea, and work in tandem with discussions at the United Nations about conserving biodiversity beyond national jurisdiction. The Sargasso Sea Alliance, spearheaded by the Government of Bermuda, was composed of an elite group of scientists, international marine conservation groups and private donors. The Alliance convened approximately 50 collaborators representing 10 countries and 10 research institutions to develop a baseline summary case detailing the latest scientific information on the Sargasso Sea, which aimed to promote international recognition of the ecosystem.


Dr. Sylvia Earle celebrates the historic signing of the Hamilton Declaration on Collaboration for the Conservation of the Sargasso Sea


On March 11, 2014, the Sargasso Sea Commission was formally established to replace the Alliance. In the middle of the Sargasso Sea, five governments, including the Government of Bermuda, the Azores, the Principality of Monaco, the United States, and the United Kingdom, met in Bermuda to formally sign the Hamilton Declaration on Collaboration for the Conservation of the Sargasso Sea. Since then, the number of Signatory governments has doubled, and now includes the governments of The Bahamas, the British Virgin Islands, Canada, the Cayman Islands, and the Dominican Republic. Dr. David Freestone, the Executive Secretary of the Sargasso Sea Commission, announced at the historic signing of the Hamilton Declaration that “this is the first time an international partnership has been formed to develop protection measures for an iconic high seas ecosystem using existing international law frameworks.” The mandate of the Sargasso Sea Commission is to exercise a stewardship role for the Sargasso Sea and keep its health, productivity, and resilience under continual review. It is an international partnership that aims to secure global recognition of the ecological significance and threats facing the Sargasso Sea and to collaborate through existing organizations to secure protective measures and establish appropriate management.


A Humpback whale swims through Sargassum (c) Andrew Stevenson, WhalesBermuda


As the Hamilton Declaration celebrated its fifth anniversary in March 2019, the Sargasso Sea Commission has taken stock of the Commission’s achievements and the possibilities that lie ahead. Since the inception of the project almost a decade ago, the Sargasso Sea Commission has gained widespread recognition of the Sargasso Sea’s significance. The Sargasso Sea is the only ecosystem to merit an individual chapter in the first United Nations Ocean Assessment and frequent references in the annual United Nations Law of the Sea Composite Resolution. The Commission has regularly sent representatives to sectoral meetings to discuss topics including ecosystem-based fisheries management and seabed mining and established itself as a champion for the conservation of migratory species including humpback whales and, of course, European and American eels. The Corner Rise seamounts in the northern area of the Sargasso Sea were closed for bottom trawling and gear type restrictions until the end of 2020. 


The Sargasso Sea Commission and collaborating partners visit Nonsuch Island in Bermuda during the five year anniversary of the Commission. (c) The Nonsuch Expeditions, JP Rouja


The Commission has also shared the lessons learned from its work in support of the ongoing negotiation at the United Nations towards a treaty on the conservation of biodiversity beyond national jurisdiction. The Commission looks forward to the outcome of these negotiations as they reach their culmination. For the Commission, the next step will be to gather their collaborating partners to update the science case on the latest data and emerging threats facing the Sargasso Sea, which may include plastics, increased vessel traffic, and climate change. The Commission aims to use this information to conduct a full ecosystem assessment for the Sargasso Sea. This assessment would quantify potential threats and impacts on the ecosystem to provide a baseline for collaborative monitoring, recommend strategies to mitigate threats, and support effective stewardship of the Sargasso Sea. By filling in these knowledge gaps, the Sargasso Sea Commission will further their understanding of the current state of the Sargasso Sea, and will be able to conserve this iconic high seas ecosystem.

Learn more about the Sargasso Sea Commission and how you can support their work here.



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