The hidden life in our oceans

A carper of underwater microbes that covers an area the size of Greece has been discovered off the west coast of South America, reports The Independent. The "microbial mar" exists in water deprived of light and oxygen, and seems to survive by "eating" hydrogen sulphide and "breathing" nitrates - much as primitive organisms are thought to have done billions of years ago. "For most of the time in the history of the world, most of the ocean was anoxic, so these species probably dominated the planet for hundreds of millions of years," said Prof Ron O'Dor, who is leading the Census of Marine Life, a decade-long international project. "The DNA in these micro-organisms (above) has probably been alive for longer than anything else on the planet."
The census has also revealed that marine microbial life is far more diverse - and abundant - than previously realised. A decade ago, there were thought to be about 20,000 species of marine microbe. Now scientists think the figure is closer to 20 million. Meanwhile, estimates for the number of microbial cells inhabiting a litre of seawater have been upgraded from about 100,000, as suggested 50 years ago, to close to one billion. Put together, it would weigh as much as 240 billion African elephants. That's roughly 35 "elephants" of microbes per person on the planet.