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Life in the Twilight Zone

June 24, 2018

The ocean twilight zone—200 to 1,000 meters (660 to 3,300 feet) beneath the surface—teems with life. Spanning the entire world, its waters are vast, dimly lit, and under crushing pressures. Some twilight zone animals migrate to the surface every night to feed under cover of darkness, returning to the relative safety of deeper waters during the day. It is the largest animal migration on Earth. Twilight zone animals are a big part of the ocean’s food web and transfer carbon from the surface to the deep sea. That keeps a lot of carbon dioxide, a greenhouse gas, from returning to the atmosphere and thus plays a critical role in Earth’s climate system.(Illustration by Eric S. Taylor, Woods Hole Oceanographic Institution)