“Warming seas could kill off all life in the ocean’s “twilight zones.”
A new study shows that life in the ocean’s “twilight zones” may be drastically reduced or even go extinct because “the food supply is becoming insufficient inside the ocean as sea temperatures rise.”
The twilight zone is between 200 and 1,000 metres below the ocean’s surface. It is home to many creatures, such as lantern sharks and kite fin sharks.
The animals that live in that zone depend on the billions of tonnes of fish poop and other organic matter that falls into the ocean from the top.
According to a study that was published in the journal Nature, the rising temperature is reducing the amount of food that fell down to the zone. This means that up to 40% of the life in the twilight waters could be gone by the end of the century, and it could take thousands of years for them to come back.
Katherine Crichton, the lead author of the study and a postdoctoral research fellow at the University of Exeter, told Guardian: “The rich variety of twilight zone life evolved in the last few million years, when ocean waters had cooled enough to act like a fridge, keeping food fresh for longer and making conditions better for life to grow.”
“According to the research we’ve done, there wasn’t all this life in the twilight zone 15 million years ago, and now, because of what people are doing, we may lose it all. Crichton said, “It’s a huge loss of depth.”
Crichton added, “If we don’t quickly cut back on greenhouse gas emissions, this could kill or wipe out a lot of life in the Twilight Zone within 150 years, with effects lasting for thousands of years after that.”
Paul Pearson of Cardiff University said that warmer seas also make it harder to store carbon. This is because most of the “carbon that is sinking down as part of the marine snow” is eaten by microbes near the top instead of falling further.
Pearson, who is also the leader of the study, said that less sinking means that carbon is released more quickly.
Crichton said, “The good thing about the study was that it didn’t show that we’ve hit a point where we can’t go back. We can’t avoid all loss, but if we control pollution, we can avoid the worst.”
The UN programme that studies the twilight zones said, “The twilight zone is poorly understood, but it may have the largest and least exploited fish stock in the world, and it recycles about 80% of the organic matter that sinks.”
Crichton also said, “We still don’t know a lot about the ocean twilight zone, but we can figure out what might happen in the future based on what we know about the past.” According to what her team found, big changes may already be happening.”
“The study looked at three possible futures for the Twilight Zone: a low-carbon scenario, which allows for a total of 625 billion tonnes of emissions from 2010 on, a medium scenario, which allows for 2,500 billion tonnes, and a high scenario, which allows for 5,000 billion tonnes. Crichton said, “Both the middle and high scenarios are very bad for the Twilight Zone.
The Global Carbon Budget, which is run by the University of Exeter, estimated that the world’s total CO2 emissions hit 40,6 billion tonnes in 2022. From 2010 to 2012, they were close to 40 billion tonnes per year.
In the study’s low-carbon situation, most of the CO2 has already been released.