Antarctica – A hidden world beneath the Antarctic ice has been revealed, following the calving of the massive A68 iceberg from the Larsen C Ice Shelf. Using an underwater robot, scientists have discovered thousands of highly organized fish nests stretching across the seafloor, likened to a vast underwater city.
The remarkable discovery was made in a remote part of the Western Weddell Sea, an area previously sealed beneath a 200-meter-thick ice shelf. The opportunity to study this environment arose when the 5,800 square kilometer A68 iceberg broke away in 2017.
Structured Nests in the Exposed Seabed
The team, operating from the South African polar research vessel SA Agulhas II during the Weddell Sea Expedition of 2019, deployed a remotely operated vehicle (ROV) into the newly accessible waters. The ROV revealed over 1,000 circular nests, each cleared of the thick plankton detritus that carpeted the surrounding seabed.
The architects of these intricate nests are the yellowfin notie (Lindbergichthys nudifrons), a species of rockcod. Each nest would have been actively guarded by a parent fish, a protective strategy against predators. What struck scientists was the non-random arrangement: the nests formed deliberate, geometric groupings, including sweeping curves and dense clusters.
This dense clustering is thought to be an example of the ‘selfish herd’ theory, where individual fish in the center gain protection shielded by their neighbors, while solitary nests on the outskirts may be occupied by larger, stronger individuals better able to defend their eggs.
Conservation and the Search for Endurance
The Weddell Sea Expedition had a dual focus: a broad scientific study of the waters around the Larsen C Ice Shelf and the historical search for Sir Ernest Shackleton’s lost ship, the Endurance. Although the heavy pack ice prevented the team from finding the wreck in 2019, the expertise gained in operating the advanced submersibles proved vital to the successful Endurance22 expedition, which located the shipwreck in 2022.
The scientific findings, however, carry critical implications for conservation. This discovery provides strong evidence that the area constitutes a Vulnerable Marine Ecosystem (VME), a unique and fragile habitat crucial for global biodiversity. Building on previous work in the region, the findings are vital to support the formal designation of the Weddell Sea as a Marine Protected Area (MPA), ensuring the safeguard of these hidden nurseries and the broader Antarctic food web.
The finding underscores the surprising biodiversity of Antarctica and the urgent need to protect these rapidly changing environments as the ice continues to retreat.