You might expect research on octopus DNA to yield all kinds of information about octopuses, but new genetic analysis has led to an even more interesting discovery about global warming.
About 120,000 years ago, the Earth was as warm as it is today. This may have led to the complete collapse of the West Antarctic ice sheet, Australian researchers write in Sciences. To prove this, they looked at the genetic profiles of octopuses living in Antarctica, and found that populations on both sides of the West Antarctic Ice Sheet became mixed during the last ice age. By then, the ice sheet will likely have melted, so the animals can swim from side to side.
Gene exchange
Researcher Nerida Wilson from University of Western Australia “Squids could only mix and exchange genes if the West Antarctic ice sheet completely collapsed, opening up a sea route that octopuses could use to communicate with each other,” he explains.
Scientists discovered the historical genetic link between the populations by looking at the DNA of so-called Turquet octopuses that now live around Antarctica. These squid are only about the length of a pencil, excluding their arms. They live throughout the region in water up to one kilometer deep. The animals eat bristleworms, amphipods, and other small invertebrates.
The researchers sampled 96 octopuses, which they collected over a period of 33 years. Most of it was bycatch from large fishing vessels. The researchers extracted DNA from the animals from these samples. They looked at a wide range of genetic markers that allowed them to divide the squid into separate groups.
Isolated population
It showed that four groups of octopuses, living in the Weddell Sea, Amundsen Sea, Ross Sea and East Antarctica, were all connected to the ocean currents that surround Antarctica. As a result, the populations were genetically similar to each other. But after the ice sheet formed in West Antarctica, octopus populations became isolated and genetic differences began to appear. The ice sheet expanded as global temperatures dropped, creating more ice and lowering sea levels. But during the last ice age – 129,000 to 116,000 years ago – things improved again. Temperatures were 0.5 to 1.5 degrees higher than pre-industrial levels, and sea levels were 5 to 10 meters higher than today.
In line with previous research
But until now, it cannot be said with certainty whether and to what extent the West Antarctic ice sheet disappeared during that period. The new findings are now consistent with previous geological evidence that already pointed to significant ice loss. In 2019, a scientific drill ship already removed sediment from “Iceberg Alley,” an important route along which Antarctic icebergs drift north. Sediment cores showed a significant increase in icebergs during the last ice age. This shows that there may have been a massive collapse of the ice sheet. Clever analysis of squid DNA now provides quite convincing evidence that the ice sheet completely disappeared during that period.
Critical to sea level rise
This is worrying, of course, as the weather is as warm now as it was then. The results show that even if we manage to keep temperature rise below 1.5 degrees in the Paris climate agreement, the West Antarctic ice sheet could melt.
Lead researcher Professor Jan Strognell from James Cook University It explains how important it is that we learn more about the potential disappearance of this ice. “The West Antarctica Ice Sheet is critical to our forecasts because it is the largest contributor to global sea level rise across Antarctica. A complete collapse would likely raise water levels by 3 to 5 metres.”
This has serious consequences for many coastal areas and many of the world’s major cities located by the sea. The results of this study can therefore make an important contribution to decision-making regarding climate adaptation around the world.
