Marine Organisms in the Twilight Zone Under Threat of Warming Due to Climate Change

For years, we have been warned about the dire effects of climate change on our biosphere. Widespread concerns are shown on how to prevent this catastrophe, but most of the actions focus on terrestrial life. Scientists remind us that climate change also affects the life forms in the deepest parts of our oceans.

The Dark Side of Climate Change

By the end of the century, global warming is expected to reduce almost 40% of life forms within the twilight zone, formally known as the mesopelagic zone. This was reported from a study conducted by a group of researchers at the University of Exeter.

Dr. Katherine Crichton led the research, which examined the warmer periods of Earth's history and analyzed the records of living organisms from preserved microscopic shells. As calcium carbonate accumulates on the seafloor, it records the type of environment during its lifetime. These tiny shells provide a timeline of the changes that occurred in the ocean over a million years.

The researchers found that fewer organisms thrived 50 million years ago and 15 million years ago. They concluded that it is due to the quick degradation of food by bacteria resulting in less sustenance reaching the twilight zone from the surface.

Dr. Crichton explains, "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, preserving the food for longer, and improving conditions allowing life to thrive."

Crichton's team used a simulation to predict the possible scenario that could be happening now in the twilight zone as well as the forecast of events in the future as affected by climate change. Their findings reveal that significant changes may already be in progress. Crichton believes that their study serves as an initiative to examine the vulnerability of ocean habitats to global warming. She also suggests that if greenhouse gas emissions are not reduced, this trend could lead to the extinction of life forms in the twilight zone within 150 years.

What Lies Beneath the Twilight Zone?

The twilight zone is the area of the ocean that lies between 200m and 1,000m. Also known as the disphotic zone, this region is a very important habitat for marine life. The depth makes it impossible for photosynthesis; organisms such as phytoplanktons serve as food for other creatures.

Oceanographers believe that the twilight zone could have ten times or 100 times the biomass than previously thought. Although humans do not have direct interaction with these organisms, it cannot be denied that we also rely heavily on the biological processes in this region.

The twilight zone is very important in keeping carbon dioxide out of the atmosphere. According to Woods Hole Oceanographic Institution, about 25% of the total carbon dioxide emission from human activities is absorbed by the ocean. The twilight zone comes into play by transferring this gas from the surface to the deep region.

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