Development of marine life in the twilight zone in connection with climate change Science & Tech News
New research has shown how creatures in the ocean’s so-called twilight zone, which extends from 200 to 1,000 meters below the surface, evolved as a result of climate change.
Led by scientists from Cardiff University, the study was the first to track how the world’s largest and least understood habitat evolved as the oceans cooled over the past 15 million years.
The habitat is home to some of the most mysterious creatures in the world, from plankton and jellies to octopus and very strange looking fish.
“There is a real hidden treasure of biomass and biodiversity that is vital to the health of our oceans,” said Cardiff University.
All life in the twilight zone is dependent on “sea snow”, the organic matter that sinks from the surface as a source of food.
The study analyzed tiny fossil shells extracted from mud on the ocean floor to see how deep-sea creatures had changed and diversified over time.
“During our study, we observed evidence that species migrated from the surface to deeper and deeper regions of the oceans over a period of 15 million years, which was puzzling,” said paleontologist Dr. Flavia Boscolo-Galazzo, one of the two main authors of the study.
“The water temperature turned out to be the key to the puzzle,” added lead author Dr. Katherine Crichton, who developed a computer model simulation of the evolution of the marine carbon cycle over time.
“The interior of the ocean has cooled significantly during this time. This had a cooling effect, which means that the sinking sea snow lasts longer and sinks deeper and provides food.”
Dr. Boscolo-Galazzo continued: “The cooling of the deep ocean gave life a boost and made it flourish and diversify.”
The researchers penetrated the mud beneath the floors of all of the world’s oceans to build a story about which plankton communities would have inhabited the oceans over millions of years.
The fossil plankton in the mud contained clues as to the depths at which the creatures lived, as well as the density of the falling sea snow around them.
The team says the results raise new concerns about the future of our planet’s oceans as they warm up under the pressure of global climate change.
“Many of the strangest life forms are found in the depths of the ocean, including comb jellies that look like alien spaceships and ugly fangfish. But they’re also vital to the ocean’s food webs,” said Project Leader Professor Paul Pearson.
“Deep fish make up one billion tons of biomass and are an important food source for whales and dolphins, as well as large diving fish like tuna and swordfish,” added Professor Pearson.
If changes in sea temperature affected this stage of the food chain, it could reverberate across the planet’s ecosystem.
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