The wavy fronds of seaweed form a peaceful underwater scene, with dappled sunlight falling. However, hidden in the genes of organisms may be evidence of the planet’s past geological violence.
In an article published last week in the journal Proceedings of the Royal Society B, The researchers say that the genes of the seaweed bull along the coast of New Zealand’s South Island bear marks of an earthquake that occurred 800 years ago, when part of the ocean floor rose and annihilated its inhabitants. That gave way to newcomers from a different genetic environment, the ancestors of today’s algae. The finding suggests that moments of cataclysmic change in an environment may be revealed by comparing genes between populations of some organisms.
New Zealand is on a fault nest. After an earthquake four years ago, the edge of a fault near the town of Kaikoura soared more than six feet out of the water, and Jon Waters, a professor of zoology at the University of Otago, and his colleagues began to wonder what happened. with the kelps. after such destruction. Stranded above the high tide line quickly die, but as the underwater ecosystem changes to a new normal, there is suddenly a plethora of free real estate, where new individuals can come in and take over. And because of the way a population of algae covers an area in the long term and leaves little room for newcomers, Dr. Waters said, the algae provided an ideal test bed to see if the effects of a disaster on the gene pool persist over time.
About 800 years ago, according to the geological record, there was a similar earthquake in New Zealand along the coast near Dunedin. Scientists took samples of seaweed along a 60-mile stretch of that coast. Each individual algae was very similar to the others of its species. However, when scientists examined genetics, there were large differences related to where the kelps had been collected. The bull algae that lived along a 15-mile stretch that had been forced into the air during the long-ago earthquake were distinct from their same-species neighbors on either side, whose homes had remained intact for a long time.
“We were stunned when we looked,” said Dr. Waters. “We were able to see where the elevation zone was just by looking at the genetics.”
When the wandering bulls off the coast reached the earthquake-left wasteland, they likely proliferated rapidly, dominating the entire footprint of the elevated area in a few decades, before others could enter. Their descendants still live there. . Their presence is a sign of an old interruption, but also of renewal.
“One of the things we learned from this is how quickly nature recovers,” said Dr. Waters. “It is reassuring that nature has that power.”
The work corroborates the idea that after ecosystems recover from catastrophes, the genetic makeup of the organisms there can carry signatures of change for hundreds of years or more. The fact that the new kelp has barely mingled with its neighbors 800 years after the earthquake is particularly interesting: it suggests that a “winner-take-all” effect is taking place, where the first individuals on the scene can maintain their dominance for centuries. The researchers wrote. The group is now observing the recolonization of the elevated Kaikoura earthquake zone, collecting samples as new kelps arrive. Kelps are travelers, it turns out. People can float thousands of miles and still be viable when washing on a distant shoreline.
And when kelp proliferates, Dr. Waters said, many small creatures that live within it can also return. The tangled strands that bind seaweed to rocks form small, sheltered worlds in the surf where small crustaceans and other animals reside.
“You have a small, protected environment for things to happen in your daily life,” he said.
