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Beneath the surface of the world's oceans lies an ecosystem of staggering complexity, the vast majority of which remains entirely unknown to science. A milestone in marine biology was reached when researchers catalogued a million previously unrecorded species of microscopic sea life, offering (17) .......... about the ocean's inner workings that could fundamentally (18) .......... our understanding of how climate change is reshaping the marine environment. Each newly identified organism was encountered in the (19) .......... of the Pacific and Atlantic oceans by the research vessel Tara — a (20) .......... small craft for an undertaking of such extraordinary scientific ambition.
The expedition's (21) .......... have for the first time illuminated the astonishing diversity of microscopic plankton that underpin virtually every marine food chain. In total, 1.5 million distinct species of microorganism were formally recorded — (22) .......... more than the scientific community had previously supposed possible.
The conclusions carry a grave note of caution. The oceans are acidifying at an accelerating rate, a trajectory that will remain unaltered unless global (23) .......... of carbon dioxide are brought under meaningful control. Since the organisms now catalogued are acutely sensitive to changes in pH, a failure to act could see vast numbers of them classified as (24) .......... species within the century.