Global cooling helped life flourish in ocean’s twilight zone

Life populating the shadowy ocean flourished thanks to the cooling of the Earth's climate over millions of years, according to a new study involving UCL. The research team tracked the development of the largest and least understood habitat on Earth, home to a wide range of mysterious creatures, including plankton, jellies, krill, squid and fish. The ocean's twilight zone extends from 200 to 1,000 metres below the ocean's surface. Within it is a hidden treasure of biomass and biodiversity that is key to the health of our oceans. In a new study, published in Science , the team showed how life there became established and diversified, driven by the cooling of the ocean over the last 15 million years. The new findings raise concerns about how the array of creatures that live at these depths may react to future heating of the oceans. Life in the twilight zone relies on "marine snow" - organic matter that sinks down from the surface - as a source of food.