No one anticipated the coral graveyard that lies nearly a kilometer below the surface off the coast of the Galápagos. Not the visitors who come each year to see the tortoises and finches. Nor do the majority of marine biologists. Until recently, scientists believed that areas like these were the stable ones, the sections of the ocean that just survived while everything above them burned and bleached. The reefs are located in cold, dark water where sunlight never really reaches.
It’s beginning to seem like a generous assumption. Recent research published in PNAS by a team at the University of Bristol under the direction of Dr. Joseph Stewart subtly challenges the notion. They recreated a 117,000-year history of life on the Galápagos seafloor after examining over 900 fossil stony corals that had been dredged from depths of up to 1,000 meters. The corals had made it through the previous Ice Age. The subsequent warming had not affected them. Then they just stopped appearing in the records about 5,000 years ago. The seafloor became silent for over a millennium.
| Key Information | Details |
|---|---|
| Study Title | Lost Millennium of Galápagos Deep-Sea Corals Linked to Major Pacific Climate Shift |
| Published In | Proceedings of the National Academy of Sciences (PNAS) |
| Publication Date | 20 April 2026 |
| Lead Author | Dr Joseph Stewart, Lecturer, School of Earth Sciences |
| Lead Institution | University of Bristol, UK |
| Co-Author | Professor Laura Robinson, Professor of Geochemistry |
| Field Partners | Charles Darwin Foundation, Galápagos National Park Directorate |
| Fossil Samples Analysed | More than 900 deep-sea stony corals |
| Depth of Collection | Up to 1,000 metres below sea level |
| Dating Method | Uranium-thorium dating |
| Timeline Reconstructed | 117,000 years of coral ecosystem history |
| Key Finding | Deep-water corals vanished for over 1,000 years, starting around 5,000 years ago |
| Climate Link | Prolonged La Niña phase within ENSO variability |
| Submersibles Used | HOV Alvin and ROV SuBastian |
| Region Studied | Galápagos region, Eastern Tropical Pacific |
It’s the kind of detail that sticks in your memory. A millennium is not a bump in the road. It happened to an ecosystem that everyone had dismissed as resilient, and it is older than the majority of cathedrals and the recorded climate history in many regions of the world.
The disappearance was linked by the researchers to a prolonged La Niña phase, during which deeper, nutrient-rich water was drawn to the surface by stronger ocean circulation, depriving the corals below of oxygen. The El Niño Southern Oscillation, the climate seesaw that most of us only hear about when it ruins a fishing season or floods a coastline, is now viewed differently by scientists as a result of this discovery.
El Niño has always been portrayed as the antagonist in popular culture because of its warm-water bleaching events that destroy shallow tropical reefs. In contrast, La Niña has been compared to the recovery phase. That is complicated by this new work. Long periods of La Niña-like weather can be equally harmful, according to Stewart, but the damage occurs in areas that people seldom visit. The idea that something we’ve been taught to associate with calmer, colder waters can silently suffocate an entire deep-water community is peculiar.
The fact that the recovery was so sluggish is unsettling. In the end, coral did return to the depths of the Galápagos, but on timescales unrelated to election years or human policy cycles. The co-author of the study, Professor Laura Robinson, noted that conservation efforts now have to deal with the fact that once disturbed, these ecosystems take centuries to rebuild. It is difficult not to interpret that as a warning directed directly at the present.
Although no one can say with certainty which way or how quickly ENSO behavior is changing as the planet warms, climate models already indicate that it is. A form of physical memory is added by this fossil record. This is nothing new for the deep ocean. It handled it poorly. It is hard to feel comforted by the antiquated notion that the deep sea serves as the planet’s buffer when you watch the same climate machinery rev up again, only faster this time. We haven’t bothered to look into it yet, but it might be more akin to a mirror.
