Future Sea-Level Rise: Unveiling Clues within Octopus DNA

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The groundbreaking research delved into the genetic ancestry of the Turquets octopus (Pareledone turqueti) that inhabits the seafloor of the Antarctic, aiming to uncover insights about the region's geological history. Analysis of historical interactions among different populations of the species indicated that the most recent ice sheet collapse took place over 100,000 years ago during the Last Interglacial period. This confirmation, long suspected by geoscientists, was detailed in a study published in the journal Science on Thursday.

Lead study author Sally Lau, a postdoctoral research fellow at James Cook University in Australia, expressed her excitement about the project, stating that it provides a fresh perspective for addressing a longstanding question within the geoscience community. She also highlighted that the DNA of modern-day animals serves as a time capsule, containing information about their ancestors from the past.

The research team utilized DNA sequencing to investigate 96 Turquets octopuses collected from institutions worldwide and through fishing bycatch over several years. Even the oldest samples from the 1990s, when sequenced, revealed a detailed family tree dating back millions of years.

The team studied genetic information from Turquet's octopus, which is pictured above.

Researchers used DNA analysis to determine if different populations of Turquets octopuses had interbred and when this interbreeding occurred. This allowed for a greater understanding of the species' genetic interactions.

“It’s as if we’re conducting a genetic test on the octopus, similar to 23andMe,” Lau explained. “This genetic information is passed down from one generation to the next and so forth.”

Currently, the populations of Turquets octopus in the Weddell, Amundsen, and Ross seas are isolated by the massive West Antarctic ice shelves and are unable to mix.

The study indicated a genetic connectivity between these populations around 125,000 years ago during the Last Interglacial, when global temperatures were similar to today's. This suggests that the West Antarctic ice sheet had collapsed during this time, allowing octopuses to occupy ice-bound areas on the seafloor and encounter and breed with members of Turquet's populations that were once geographically separated from one another.

Jan Strugnell, a professor and director at the Centre for Sustainable Tropical Fisheries and Aquaculture at James Cook University, emphasized the importance of the WAIS as Antarctica's largest current contributor to global sea level rise. She highlighted the potential impact of a complete collapse, estimating that it could raise global sea levels by 3 to 5 meters. Strugnell proposed using genomic methods to investigate the collapse of the ice sheet during the Last Interglacial, stating that understanding its configuration during periods of similar global temperatures can improve projections for future sea level rise.

Conducting the research are Sally Lau (right), a postdoctoral research fellow at James Cook University in Australia, and Jan Strugnell, professor and director of the Centre for Sustainable Tropical Fisheries and Aquaculture at James Cook University.

Joe Perkins

Why octopuses?

The team selected this particular octopus species for the study due to their limited mobility, as they can only crawl along the seafloor, increasing the likelihood of breeding within their genetically distinct local groups. In contrast, faster-moving marine species like krill would have more uniform DNA, obscuring historical genetic connections, Lau explained.

Furthermore, the biology of the Turquets octopus has been extensively researched, and scientists have a good understanding of its DNA mutation rate and generation time, which are essential for precise molecular dating, Lau noted.

Using octopus genomics is an "an innovative and exciting way" to address an important question about historical climate change, one expert said.

Louise Allcock noted previous studies found a biological signature of ice shelf collapse with connectivity between the Ross and Weddell seas in species of crustacean and marine mollusk. However, the new Turquet octopus study is the first to provide high-resolution data and an adequate sample size to determine whether genetic connectivity is driven by the ice sheet collapse or the gradual movement of octopuses around its edges.

Lau mentioned that their genetic approach was not able to provide specific timing or duration of the ice sheet collapse. Nonetheless, the use of fresh octopus samples and advanced DNA analysis techniques could potentially address these questions in the future.

Landmark research

Published alongside the study, Andrea Dutton, a professor in the department of geoscience at the University of Wisconsin-Madison, and Robert M.DeConto, a professor at the School of Earth and Sustainability at the University of Massachusetts Amherst, lauded the new research as "landmark."

The geological evidence suggests that the West Antarctic ice sheet may have collapsed during the Last Interglacial period. However, each study's findings come with caveats. Introducing a new dataset raises intriguing questions about whether this history will repeat itself, given Earth's current temperature trajectory.

Douglas Crawford, a marine biology and ecology professor at the University of Miami, commented that utilizing octopus genomics was a groundbreaking and thrilling approach to examining the significant issue of historical climate change. He further stated that the study was meticulous, with a sufficient sample size and a thoroughly reviewed set of genetic markers.