Oceans: A Book of Life for the Seas

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“Only the sea knows the depth of the sea.” So goes a line from Hindu scriptures, one that well describes the mystery of the ocean depths—and our ongoing ignorance about life beneath the waves. For thousands of years, our knowledge of the seas was limited to surface currents and the fish that we could catch, close to the coast. We knew little of what lived below the depth a man could dive, and often imagined the deep ocean to be an aquatic desert, undifferentiated and mostly devoid of life.

It was only in the 19th century that scientists began to look deep—in the 1870s the HMS Challenger performed a remarkable around-the-world scientific voyage, dredging amazing creatures from the deep. But even today, when humans has gone to the deepest part of the ocean (though only once) and robots can perform fine procedures more than a mile beneath the surface, our knowledge of the deep seas and what lives there is still a sketch. Almost 20% of the oceans’ volume has never had a single scientific sample taken from it. As the oceanographer Sylvia Earle told me recently: “We don’t even know what we don’t know.”

But that’s beginning to change, thanks to one of the most silently remarkable scientific research programs ever launched. This afternoon at the Royal Institution of Great Britain in London scientists will present the finds of the first Census of Marine Life, a 10-year-long initiative that attempted—for the first time—to systematically catalogue what lives in the world’s oceans. (Download a PDF—it’s 15 MB—of  the Census here.) The $650 million program is probably the most ambitious act of marine science in history—and thanks to advances in genomics that allow for rapid DNA screening of new organisms, certainly one of the most fruitful. “We are now more aware of the limits of what we know now,” Ronald O’Dor, the co-senior scientist at the Census, told me recently. “We’ve gone where no one has ever explored.”

The results of the Census, at a time when it can sometimes seem that we’ve fully explored this planet, are really quite amazing:

540+ research expeditions

9,000 days at sea

2,700+ scientists

80+ countries

2,600+ peer-reviewed scientific publications

1,200+ new species described

5,000+new species collected, and not yet described

35,000 species identified with DNA barcodes

18 million microbial DNA sequences

It’s those last series of numbers that really make a difference. Before the Census began, O’Dor says that scientists estimated that there were perhaps 250,000 species in the oceans, “but that was really just a guess.” The Census has put hard data to that estimate—and provided ample evidence that the oceans are full of life. “The number of 250,000 will almost certainly go up to 1 million, perhaps 2 million,” says O’Dor.

The scientists who participated in the Census—which took some of its funding from the Alfred P. Sloan Foundation—have found new species the old-fashioned way: pulling up samples from the deep, then doing the taxing scientific work of searching the published literature to ensure the sample really is a new species, a process that can take years.

But the Census researchers also managed to rapidly characterize new species with new genetic sequencing tools. Species have DNA barcodes—a snippet of genetic code that might be as small of 700 base pairs—that when analyzed has a more than 95% chance of providing enough information to distinguish new and different species. That can speed up the process of cataloguing life exponentially—and not just for fish, plants and marine mammals. Bacteria make up most of the biodiversity found in the oceans—as much as 90% by weight—and the Census identified millions of new microbes, any of which could become useful biomaterial in the future. “It’s going to be a transitional process for taxonomy, using DNA barcodes,” says O’Dor. “But now we have a short answer that can be easily indexed in print and online.”

The Census won’t end this week—the research initiative has helped put together a growing global ocean network of underwater microphones that can track salmon and other migranting species, as well as thousands of “bio-logger” animals that are equipped with recording devices that will send back data as those sentinels swim around the world. And perhaps most importantly the Census has collected and collated what we know about the marine world—through nearly 30 million observations of 120,000 species made during the Census—in the Ocean Biogeographic Information System. It’s the Book of Life for the oceans.

The information from the census will help scientists establish baselines for the oceans that can be used in the future to determine the impact of oil spills, climate change and everything else humans will do to the seas. But as wide-ranging as the Census is, there’s still a great deal that we don’t know about the ocean life—or how the seas and the global climate system interact. And while there’s more work for the Census to do, it’s not clear where the additional funding will come from—or if it will come at all. “It’s likely to take us another 50 years to get a full picture of what’s in the oceans,” says O’Dor. “But we would probably manage the oceans better if we knew about the 75% of other things that were in there.”

O’Dor’s right—and between climate change, ocean acidification, overfishing and marine pollution, it’s worth wondering how much of that 75% will still be there in a half century. The oceans, as I wrote for TIME magazine recently, are in a crisis, and their fate—and ours—is cloudy. But at the very least the Census of Marine Life should remind us how much is still out there in the depths, waiting. As Ian Pointer, chair of the Census Steering Committee, put it: “The Age of Discovery continues.”