video transcript

SOUNDBITE (English) CHRIS BOWLER, SCIENTIFIC COORDINATOR OF TARA OCEANS, SAYING: "When you do take a microscope and look at the average drop of water you see that it's really teeming with all kinds of microscopic life that do incredibly important functions for managing the planet, ensuring the well-being of the planet, generating the oxygen we breathe, removing carbon dioxide from the atmosphere and generally maintaining this Earth in a state that is habitable for us human beings." Scientist Chris Bowler has just returned from a 70,000 mile voyage across the world's oceans aboard Tara, a schooner equipped for scientific research. The Tara Expedition is a unique attempt to investigate the impact of climate change on marine ecosystems and biodiversity. The crew have brought back 30,000 samples from the ocean floor. They'll take a decade to analyse but preliminary findings suggest there are 1.5 million types of plankton in the sea - double previous estimates. SOUNDBITE (English) CHRIS BOWLER, SCIENTIFIC COORDINATOR OF TARA OCEANS, SAYING: "We're using very high throughput DNA sequencing technology, we're using high throughput microscopy....but obviously it's going to take a long time and we need not only to study what plankton are present in each different area that we sampled , but we also need to match that up with the physical, chemical conditions of that area." Among the samples...the humble diatom, a unicellular organism which first appeared 200 million years ago. Bowler says the diatom is crucial to human existence. SOUNDBITE (English) CHRIS BOWLER, SCIENTIFIC COORDINATOR OF TARA OCEANS, SAYING: "Close to half of the oxygen generated by the oceans we believe comes directly from diatoms, so that basically means every fifth time that you breathe you're breathing oxygen which we can directly trace back to diatoms, so they're sort of as important as a tropical rain forest in terms of their global contribution." Bowler says plankton populations are affected by climate variations, and in turn can influence the climate by modifying the earth's absorption of carbon. The expedition team say their study is crucial to predicting how the ocean will look in the future when CO2 levels are higher and ocean acidification more concentrated. The study will be published on free-access databases, allowing scientists to go back in time to improve their understanding of the biosphere's history. But Bowler's team say looking to the future is perhaps even more important. They see their plankton survey as a new source of evidence underscoring the dangers of climate change.