Sea life vastly more varied than we realised, say scientists

The diversity of microbes living in the world's oceans may be more than 100 times greater than previously estimated, according to a survey of marine life.

Scientists working in marine sites around the world, including several North Atlantic sites between Greenland and Iceland, were astonished to find that they had massively underestimated the diversity of single-cell organisms that, despite being invisible to the naked eye, make up 98 per cent of life in the oceans.

An international team of marine biologists carried out the study with the help of DNA probes, which can quickly distinguish between thousands of life forms in a single glass of seawater.

Only 5000 marine microbes have been named and formally described by scientists but the true number of bacterial species living in the ocean could be up to 10 million, said Mitchell Sogin, director of the Marine Biological Laboratory in Massachusetts.

"This study shows we have barely scratched the surface. Over the last 10 to 20 years molecular studies have shown there to be more than 500,000 kinds of micro-organisms," he said.

"In our new study, we discovered more than 20,000 in a single litre of seawater, having expected just 1000 to 3000. These observations blow away all previous estimates of bacterial diversity in the ocean.

"Just as scientists have discovered through ever more powerful telescopes that stars number in the billions, we are learning through DNA technologies that the number of marine organisms invisible to the eye exceeds all expectations, and their diversity is much greater than we could have imagined."

Marine microbes are living descendants of the most ancient forms of life on Earth, and without them life in the sea and on land would not be possible, which is why scientists want to know more about their diverse roles.

"Microbes constitute the vast majority of marine biomass and are the primary engines of the Earth's biosphere," Dr Sogin said.

"They are the oldest life forms, the primary catalysts of energy transformation, and fundamental to the biogeochemical cycles that shape our planetary atmosphere and environment."

The latest research, published in the Proceedings of the National Academy of Sciences, was carried out by researchers working on the International Census of Marine Microbes, part of the Census of Marine Life, a 10-year initiative to catalogue the diversity of the oceans before they are depleted.

- INDEPENDENT