A study of DNA found by an environmental charity in the waters of the Sargasso Sea has uncovered evidence of rare species including pygmy sperm whales.

Chris Thorne, a senior oceans campaigner at Greenpeace UK, said that the results of tests from environmental DNA samples collected in May 2024 demonstrated the rich biodiversity of the region’s waters.

“We’re all thrilled to know that pygmy sperm whales are resident in the region as they are notoriously elusive and difficult to see,” he said.

“Sadly, our research has also shown that the Sargasso Sea is facing growing pressure from shipping and industrial fishing fleets.

“Drifting longlines pose a major risk to this precious ecosystem because they fish indiscriminately, hooking marine mammals, turtles, seabirds and sharks along with their intended catch.

“Huge container ships and tankers plough through these waters day in, day out.

“In order to give the life of the Sargasso a fighting chance and support Bermudians who depend on it, the UK and other governments must champion the Sargasso Sea as one of the first ocean sanctuaries under the treaty and work with the Government of Bermuda to manage it.”

Last year, the charity travelled from the Bahamas to Spain with a visit to Bermuda as part of a campaign to have the Sargasso Sea declared an ocean sanctuary under the yet-to-be-ratified Global Ocean Treaty.

As part of the campaign, Greenpeace members on board the Arctic Sunrise collected water samples for eDNA analysis to determine which organisms lived or passed through the area.

The researchers also carried out an acoustic survey using hydrophones intended to record the sounds of marine mammals such as whales and dolphins.

Greenpeace announced this week that the eDNA analysis, carried out by researchers at the universities of Edinburgh and Exeter, revealed the presence of about 40 vertebrates including several vulnerable and near-threatened species.

A spokesman for the charity said that the study found evidence of five species of marine mammals including pygmy sperm whales, which are only slightly larger than dolphins and rarely seen in the wild.

The eDNA also found evidence of bottlenose dolphins, pantropical spotted dolphins, Gervais’s beaked whales and South American sea lions, although it was noted that the sea lion DNA was found far outside the known range of the species and so the result should be “interpreted with caution”.

The testing also recorded at least 14 families of fish including flying fish, jacks and trevallies, as well as tunas, mackerels and eels.

“Some fish could be identified to species level, such as the Sargassum frog fish, yellowfin tuna and veiled anglemouth, while some could only be detected as far as their biological group,” the spokesman said.

Meanwhile, the acoustic survey recorded eight “acoustic encounters” over the course of the journey.

While six of the recordings were found to be of dolphins, two were found to be groups of sperm whales, including one group within Bermuda’s coastal waters.

“Deep-diving sperm whales are globally designated as vulnerable on the IUCN [International Union for Conservation of Nature] Red List of Threatened Species,” the spokesman said.

“They are highly migratory, dependent on travelling through open areas like the Sargasso, so this detection is important in underlining the need for the Sargasso Sea to be protected as an ocean sanctuary.”

Noelle Young, a Bermudian environmental justice delegate, said that the island’s identity is deeply tied to the health of the Sargasso Sea and the rich variety of life that call it home.

“Its floating mats of Sargassum seaweed are a vital habitat for marine creatures found nowhere else such as the Sargassum frog fish, tiny pygmy sperm whales, shrimp, crabs, flying fish and more,” she said.

“It is a spawning ground for American and European eels and an important route for highly migratory and vulnerable humpback whales and sea turtles.

“Sadly, this valuable marine environment is threatened by environmental change, industrial fishing and pollution, but there is hope.”

Ms Young said that the region was a prime candidate for protection under the High Seas Treaty, which would bolster not only wildlife but Bermudian communities.

“Civil society in Bermuda — from fishers and local businesses to scientists — are pushing for its protection and governments like the UK must join us in championing the Sargasso Sea as one of the first ocean sanctuaries under the treaty,” she added.

The spokesman said that talks about implementing the Global Ocean Treaty or High Seas Treaty are under way, with governments meeting at the UN until Friday.

“As it moves towards entering into force, with only eight more countries required to complete ratification before it commences, the next priority is how the treaty can be used to create ocean sanctuaries covering 30 per cent of the world’s oceans by 2030,” he added.

“Greenpeace UK is calling for the just and equitable protection of the ocean, and urging progress on priority sites in the Atlantic and across the globe, including the Sargasso Sea.”