Life in the ocean’s “twilight zone” could decline dramatically due to climate change, new research suggests.
The twilight zone (200m to 1,000m deep) gets very little light but is home to a wide variety of organisms and billions of tonnes of organic matter.
The new study warns that climate change could cause a 20-40% reduction in twilight zone life by the end of the century.
And in a high-emissions future, life in the twilight zone could be severely depleted within 150 years, with no recovery for thousands of years.
“We still know relatively little about the ocean twilight zone, but using evidence from the past we can understand what may happen in the future,” said Dr Katherine Crichton, from the University of Exeter, and lead author of the study.
The research team, made up of palaeontologists and ocean modellers, looked at how abundant life was in the twilight zone in past warm climates, using records from preserved microscopic shells in ocean sediments.
“We looked at two warm periods in the Earth’s past, about 50 million years ago and 15 million years ago,” said Professor Paul Pearson of Cardiff University, who led the research. “We found that the twilight zone was not always a rich habitat full of life. In these warm periods, far fewer organisms lived in the twilight zone, because much less food arrived from surface waters.”
Animals in the twilight zone mainly feed on particles of organic matter that have sunk down from the ocean surface.
The study showed that in warmer seas of the past, this organic matter was degraded much faster by bacteria – meaning less food reached the twilight zone.
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Posted On: 27/04/2023