Marine scientists are building a device to collect samples from the ocean's 'twilight zone', containing CO2 capturing plants, as well as the faecal pellets of creatures that eat it. Matthew Stock reports.
Marine scientists call it the ocean's 'twilight zone', where only a small amount of sunlight can penetrate. But it's the ocean life here - between 100 and 1000 metres deep - that scientists say is crucial for keeping atmospheric carbon-dioxide (CO2) levels 30 percent lower than it otherwise would be. (SOUNDBITE) (English) DR STEPHANIE HENSON, OCEAN BIOGEOCHEMIST, NATIONAL OCEANOGRAPHY CENTRE (NOC), SAYING: "So, just like the plants in your garden, phytoplankton - the plants in the ocean - absorb carbon dioxide from the atmosphere. The difference is when these guys sink they can go down into the deep ocean. And then the deep ocean of course isn't in contact with the air anymore and so it's captured and it's stored down there for long periods of time." In a bid to collect samples from this elusive region, they've built PELAGRA, or the 'pelagic lagrangian sediment trap'. (SOUNDBITE) (English) PROFESSOR RICHARD SANDERS, HEAD OF OCEAN BIOGEOCHEMISTRY AND ECOSYSTEMS GROUP, NATIONAL OCEANOGRAPHY CENTRE (NOC), SAYING: "So what this does is it samples the bit between about 50 and 500 metres, that's where a lot of the action is. We've got stuff sinking and there's lots of organisms that live there eating it." The device is carefully ballasted - so that it will drift through the twilight zone, neither sinking nor floating - all the while collecting sediment samples through these rotating funnels. After a given time it will release a heavy weight so that it rises to the surface to be picked up by the researchers. And this is what it's going to collect. Known as 'marine snow', it's comprised of dead plants, animal plankton, and plankton faeces. (SOUNDBITE) (English) DR STEPHANIE HENSON, OCEAN BIOGEOCHEMIST, NATIONAL OCEANOGRAPHY CENTRE (NOC), SAYING: "Marine snow is composed of dead phytoplankton which sort of clump together to form flakes and then they're heavy enough to sink down into the deep ocean. It can also be formed of little animals which eat the little plants and then they poop out that carbon, and then their faecal pellets are very heavy and they sink down to the bottom of the ocean, also carrying lots of carbon with them." The team is preparing to embark on missions to the south Atlantic Ocean. They hope to better understand marine snow's importance in removing CO2 from the air. The research, they say, will also lead to more advanced computer models that could more accurately predict its impact on climate.