Expedition into Tuvalu’s deep waters reveal signs of ocean health

A deep-sea expedition around Tuvalu has revealed promising signs of biodiversity.

The National Geographic Pristine Seas expedition, supported by Tuvalu’s government, began on 6 May. More than 15 scientists and filmmakers aboard the research vessel, Argo, aim to survey Tuvalu’s ocean, from lagoons and coral reefs to deep-sea habitats.

The team is using tools like the Argonauta submersible, baited underwater cameras, environmental DNA (eDNA) sampling, and deep-sea dropcams. The months-long voyage is the 10th leg of a global Pacific initiative launched in 2023.

Oceanographer and expedition lead Dr Keiron Fraser describes Niulakita, the smallest and southernmost island in Tuvalu, as having a healthy level of biodiversity. Before the expedition, the team suspected it might be a “biodiversity hotspot”.

Fraser says Niulakita was a key target for the expedition, and they needed calm waters to study its marine environment. But, the island, measuring just 1000 metres long with a population of 36 residents, posed challenges.

Following a month of careful weather monitoring, the team finally found a suitable window and set out from Nui Atoll to Niulakita. Although they were unable to deploy the submersible, they found similar underwater banks to those northwest of Rotuma, Fiji, in Niulakita’s depths.

“We've seen lots of interesting species, the biodiversity seems quite high there and the marine environment seems quite healthy,” Fraser says.

While the expedition is ongoing, early findings are already guiding Tuvalu’s first National Ocean Policy. During the earlier stages of the expedition near Nanumea and Nanumaga, the team frequently spotted endangered shark species, such as silky sharks and oceanic whitetips.

Fraser says sharks are currently “hammered” across the globe, often becoming bycatch in pelagic longline fisheries or targeted for shark finning. He points out that the numbers of whitetip sharks have declined from being common to rare.

“We've seen them a few times on this expedition in Tuvalu and that's an important indicator of the health of the oceans around Tuvalu,” he says. “They're a species where biologically they're an oceanic species, so they’re wide reaching and travel vast distances which makes exposes them to pelagic fishing gear.”

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Fraser says that across all survey areas, from Nanumea in the north to Niulakita in the south, biodiversity has generally remained strong. However, he cautions that the data still needs to be processed.

“We've seen lots of whales, dolphins, cetaceans, less so in the south but what we have seen across the islands in a lot of ways is that the ecological communities seem quite healthy. There's some coral bleaching, it'd be surprising if there wasn’t because we're quite near the equator.

“But generally speaking, the biodiversity of these islands and the abundance of lots of species looks pretty healthy. There's a lot of good news there.”

The National Geographic Pristine Seas research vessel, the Argo. Photo/National Geographic Pristine Seas/Mary Nail.

The expedition now shifts its focus to Tuvalu’s shallow reef systems. Fraser has completed his handover to a new team as he returns to the United Kingdom. Going forward, the team will use scuba diving and inshore-baited cameras to assess coral health and monitor nearshore species that are most vulnerable to rising temperatures.

“I've worked in the Pacific now for four years and prior to that, I hadn't really worked here. It's been an amazing experience with National Geographic Pristine Seas. In some of these countries we go to, certainly in Tuvalu, there's lots of locally managed marine areas, which are small locally managed protected areas.

“They seem to work. Western countries can help some of the Pacific countries with marine protection, advice and provide help with gathering data and things but there's also a huge amount we can learn. A lot of these communities live in quite a synergistic way with the oceans around them and in a much better balance than, say, the country I come from.”