What is the Twilight Zone?
Why is it important to protect the Twilight Zone?
Key parts of the biological carbon pump:
The surface ocean is full of tiny plants called phytoplankton and, like trees and grasses, they use carbon dioxide to grow. Phytoplankton are a vital part of the ocean food chain, creating huge amounts of new plant material each year – as much as all land plants combined, including rainforests! This material is eaten by tiny creatures such as copepods, which in turn are eaten by bigger animals and so on, reaching creatures such as the giant squid and sperm whale.
Many animals in the twilight zone commute up to the surface at night, and back down to the depths of the Twilight zone to respire during the day, transporting carbon dioxide away from the atmosphere and storing it deep in the ocean.
All the growth and feeding in the surface ocean creates a huge amount of debris from dead creatures and the waste products of living ones, known as marine snow.
Marine snow sinks in the ocean, taking large amounts of carbon with it. The deeper it gets the longer it stays away from the atmosphere. Small creatures such as copepods actively feed on marine snow, meaning 90% is recycled within the Twilight Zone. 10% of marine snow sinks even deeper, which is important in helping maintain atmospheric carbon dioxide levels lower than they would otherwise be.
What threatens the health of the Twilight Zone?
- Carbon dioxide removal – essentially using the ocean to remove carbon dioxide from the atmosphere with the aim of reducing future global warming.
- Deep-sea mining – nodules found on the sea floor are rich in the metals we need for our technology. Areas such as the Clarion Clipperton Zone in the Pacific, spans over 3,000 miles with 400,000 square miles already contracted to mining companies. Waste from harvesting nodules maybe released nearer the surface in the nodule, impacting the ecosystem.
- Fishing – the surface ocean has roughly one billion tonnes of fish, but it has recently been estimated that there are many more in the Twilight Zone, drawing attention to it as a potential source.