Scientists charting life in the Earth's oceans have found 10 to 100 times more species of bacteria than expected, including many new and rare microorganisms.
"These observations blow away all previous estimates of bacterial diversity in the ocean," says Mitchell Sogin, with the Marine Biological Laboratory in Woods Hole, Massachusetts.
He and his colleagues from the U.S., the Netherlands and Spain did a genetic analysis of eight samples of water taken from different sites in the Atlantic and the Pacific, from depths ranging from 550 to 4,100 metres. They were astonished by what they found. There were 20,000 species of microbes in just one litre of sea water.
They had expected fewer than 3,000.
"Our jaws dropped," says Dr. Sogin.
This means a swimmer taking just a swallow of seawater could consume 1,000 different forms of bacteria.
Most don't cause disease in humans, and in fact, are essential to life as we know it on earth. They break down organic material, and make nutrients available to other sea creatures.
Most of the bacteria they found were relatively common, but about 20 per cent were rare, new species. Scientists aren't sure what they do, or where they fit in.
Ocean bacteria are invisible to the naked eye, but can be strangely beautiful under a microscope, shaped like macaroni or beads of pearls.
