Shakletonia, another amphipod found beneath
Larson B Ice Shelf
Image courtesy of C. D'Udeken,
Royal Belgium Instit. for Natural Sciences, 2007
Grassle tried hard to get people excited about his work. He did not have much luck until he went to see Jesse Ausubel, who calls himself an environmental scientist and systems analyst but whose real talent is that he is a big-picture man, an organizer, and a congenital optimist. Early in his career he began studying environmental problems. “I’m going to be doing this for 40 years,” he decided, “and I don’t want to just go around saying ‘Terrible things could happen.’”
Terrible things are in fact happening to the ocean, as Grassle told Ausubel when they met. It was July 2, 1996, and they spent most of the day together in Woods Hole, Massachusetts, where Grassle had once worked at the Oceanographic Institution and where Ausubel has a summer office. A hundred miles to the east, on Georges Bank, the codfish stock had recently collapsed, as had the much larger one on the Grand Banks off Newfoundland; regulators had been forced to close both of those rich and historic fisheries. The amount we know about the marine species we depend on, Grassle told Ausubel, is minimal. The amount we don’t know about the rest of the ocean, on the other hand, is astronomical.
Ausubel took that as a challenge. The Sloan Foundation had recently sponsored a Digital Sky Survey—a systematic census of the stars. What did Grassle think, Ausubel asked, about doing a census of the fishes? Grassle thought it was a splendid idea, as long as it didn’t get diverted into something strictly utilitarian—a census of seafood—and as long as it included all the other things that lived in the ocean, including obscure but biologically important organisms like polychaetes. The Census of Marine Life was born in 2000. “It is what it says it is,” Ausubel says. “If you pick up any textbook, there isn’t one that can tell you what lives in the ocean. From microbes to mammals, from near the shore to the open ocean, from the bottom to the top—what lives there. It’s a very simple idea.”
Finding out what lives there doesn’t just mean finding new species; it also means tracking the species we already know to find out where they go. Even highly visible marine animals lead invisible lives, far from shore or underwater or both. Stanford University biologist Barbara Block and her colleagues on a census project called Tagging of Pacific Pelagics are using microchips and satellite transmitters to penetrate those secrets. So far the researchers have tagged 2,400 animals belonging to 23 species. Some tags pop to the surface at a preset time, like a flare, and radio the animal’s position back to the team via satellite. Other animals—sharks, elephant seals, whales, leatherback turtles—are equipped with tags that phone home each time the creatures surface. The tracking project’s Web site contains a map of those animals’ movements, a tangled mesh of colored lines that is updated daily.
Such maps have revealed astonishing migrations. Bluefin tuna born in the Mediterranean cross the Atlantic to feed for a few years up and down the east coast of North America, mingling there with bluefins born in the Gulf of Mexico. Bluefins in the Pacific, on the other hand, feed off California for a few years before crossing the ocean to their breeding grounds off Japan—where a single one can fetch $175,000 on the Tokyo market. And white sharks, once thought to spend most of their time hunting seals and surfers off the California coast, actually head west in winter, to the open sea. For a few months, the sharks hang out in a patch of ocean near Hawaii that is low on food and any other obvious attraction. “My students call it the White Shark Café,” Block says.
But most of the ocean’s diversity probably isn’t hiding; it is teeming everywhere, undiscovered simply because it is so small. That is why Mitchell Sogin of the Marine Biological Laboratory in Woods Hole is directing the Census of Marine Microbes. The old way to search for microbial life in the ocean, he explains, was to isolate individual species by growing them in laboratory cultures. Biologists have identified around 5,000 species that way. But over the past 15 years or so, researchers have begun to realize that those 5,000 are just the hardy few that happen to be easy to keep alive in the lab.
A newer, far less selective way of plumbing the ocean’s microscopic diversity is to isolate individual genes, not individual microbes. Researchers use a small piece of the gene for ribosomal RNA, or rRNA—a gene that is distinct in every species—to grab all the rRNA genes that are present in a liter of seawater. Then they determine the sequence of as many of those genes as their grant money will allow—typically around a thousand, coming from a thousand bacterial cells—and use that information to estimate how many different kinds of bacteria are present in the sample.
