The oceans could be teeming with 10 to 100 times more types of bacteria than thought, say scientists who are studying what role the tiny organisms play in sustaining life.
The international team of researchers concluded that there are more than 20,000 different microbial species in one litre of seawater taken from deep in the Atlantic and Pacific oceans. The team used a new technology that distinguishes organisms using short bits of their genetic code.
"These observations blow away all previous estimates of bacterial diversity in the ocean," said the study's lead author, Mitchell Sogin, director of the Marine Biological Laboratory in Wood's Hole, Mass.
Many of the microbes differ from anything scientists had seen before, said study co-author Julie Huber, who also works at the lab.
In theory, the findings mean a swimmer swallowing a mouthful of sea water could consume 1,000 types of bacteria.
The study, released Monday, is part of the global Census of Marine Life— a decade-long project to map all marine life.
"It's similar to when astronomers used to only be able to look at certain parts of the sky," said Huber. "And when Hubble came on, they were able to see â¦ the whole universe."
Studying the microbes can help researchers to learn more about how species adapt to environmental change, said Ron O'Dor of Dalhousie University in Halifax.
"They've been around for over four billion years," said O'Dor. "They've survived all sorts of conditions, the results of volcanic eruptions and asteroid impacts, heating, cooling, everything that we can imagine, and they came through."
Scientists don't know what role is played bymicrobesthat are low in abundance.
It's possible the rare organisms are more common in some places and not others, which challenges the traditional view that life is similar across oceans.
Or the rare microbes may play an important role such as making an essential compound that is needed by themore common species, said Sogin.
The study appears in the journalProceedings of the National Academy of Sciences.