Saturday 18 November 2017

Giant microbe find linked to our earliest life-forms

Steve Connor

A VAST 'carpet' of underwater microbes that covers an area as big as Greece has been discovered on the seabed off the west coast of South America.

Scientists believe the microbes could be directly descended from some of the earliest life-forms to have evolved on Earth.

The discovery is part of a series of astonishing finds made since 2000 as part of the decade-long Census of Marine Life, an international project by more than 2,000 scientists from 80 countries to explore the largely unknown life which inhabits the oceans.

The "microbial mat" lives in a deep layer of seawater that is deprived of both light and oxygen and seems to have survived by "eating" hydrogen sulphide and "breathing" nitrates. It could represent a present-day community of organisms descended from primitive microbes which first evolved about three billion years ago, when there was no oxygen on the planet.

Scientists said they were taken aback by the spectacle when the first images of the microbial mat appeared on the television screens from video cameras on board a submersible robot, which had been lowered into the deep ocean to explore the continental shelf off the coasts of Chile and Peru.

"It was like a big carpet of white grass with filaments sticking out and waving in the water, said Victor Gallardo, a Chilean scientist on the expedition.

Initial tests showed the microbial mat is composed of a community of micro-organisms adapted to growing under extreme hypoxia, when there is little or no oxygen.

It is the same kind of conditions that existed before the evolution of the first photosynthetic algae, which were able to convert carbon dioxide into oxygen.

Scientists estimate that the mat extends over vast areas of the seabed in this region of the ocean, covering a territory roughly the size of Greece.

Explorers have found them off the central and northern parts of both Chile and Peru, and they have also been detected in sulphur-rich waters off the Galapagos islands, Ecuador and Panama.

The Census of Marine Life, which publishes its final report in October, has discovered that there are many more species of microbe living in the oceans than previously thought -- in 2000, there was thought to be about 20,000 species of marine microbe but now the number is nearer to 20 million.

"The extreme diversity and curious distribution of deep-sea microbes are among the great mysteries of nature, and begs the question about the evolution of life on Earth," said Mitch Sogin, the leader of the International Census of Marine Microbes. (© Independent News Service)

Irish Independent

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