One of Earth’s largest habitats could see its rich diversity of life reduced by the end of the century due to the climate crisis.
The ocean’s mesopelagic zone, also called the “twilight zone,” is located between 656 feet and 3,280 feet (200 meters to 1,000 meters) below the surface.
The marine region, which accounts for approximately a quarter of the ocean’s volume, is home to billions of metric tons of organic matter and some of Earth’s most stunning biodiversity, despite being beyond the reach of sunlight.
The twilight zone also a crucial habitat for marine life that dives in search of prey, like sharks, or lanternfish that hide in the twilight zone during the day and swim to the surface waters to feed at night.
New research warns that the climate crisis could reduce life in the twilight zone between 20% and 40% by the end of the century. And if greenhouse gas emissions continue, the researchers estimate that the ocean region’s life could be severely depleted within 150 years — and recovery may not be possible for thousands of years.
Ancient warm oceans
Paleontologists and ocean scientists teamed up to study the impacts on the ocean’s twilight zone during previous ancient warming events in order to predict how the habitat may respond in the future due to global warming. The research team studied cores taken from the seafloor that included evidence of preserved microscopic shells from plankton.
Over time, the calcium carbonate shells accumulate on the seafloor, preserving information about what the environment was like during their lifetime. The tiny shells effectively create a timeline of how the ocean has changed over millions of years.
A study detailing the findings was published Thursday in the journal Nature Communications.
“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 lead study author Dr. Katherine Crichton, a postdoctoral research fellow at the University of Exeter in the United Kingdom, in a statement.
The researchers focused on two warm periods that occurred 15 million years ago and 50 million years ago, where even ocean temperatures were “markedly warmer than today,” according to the study.
