Page 3 of 5

Gone: Mass Extinction and the Hazards of Earth's Vanishing Biodiversity

By the end of the century, half of all species on Earth may be extinct due to global warming and other causes. Who will survive the world's dwindling biodiversity, and why?

Weather permitting, the sub dives each morning carrying two researchers who spend the day in near-fetal positions, staring out portholes the size of grapefruit and breathing recirculated air infused with the smell of dirty socks. While the researchers work their task lists, the pilot manipulates Alvin's robotic arms, biopsying holes in the ocean bottom and collecting mud from around the seeps. Seven hours from launch, tired and dehydrated, all three aquanauts return to the surface looking a decade older.

Lisa Levin of the Scripps Institution of Oceanography is one of the foremost experts on these strange chemical worlds, and is chief scientist for one of the two research teams sharing the cruise. Her group is composed of 12 marine biologists and biogeochemists collaborating on a study of seep ecology and evolution. Petite, in jeans and Converse sneakers, Levin leans forward in pursuit of perpetual questions, then leans back to issue commands. Most of the time she just moves—fast and quiet, mud-spattered, clipboards in hand. She doesn't say much, maybe the result of working the deepwater for 27 years, making more than 70 dives into a quiet world no humans have words for.

She loves the bottom. It's possible to read mud, she says. I picture her peering out Alvin's porthole and tracking the infinitesimal movements of clams and sea stars.

We're sitting in Atlantis' library, a room familiar from many a Robert Ballard National Geographic documentary. It's six days into a three-week cruise, and her team is holding a heated powwow on mud allocation. Levin's job is peacemaker, and she tries hard to satisfy a grumpy biogeochemist who spends many hours alone in a radioisotope lab in a shipping container on a weather deck and wants more tube cores and fewer bio boxes to come up from the bottom. The other principal investigators seem willing to compromise, but to no avail.

Typical of my position on this cruise, I sit in a no man's land—in this case beside the accordion wall separating the library from the mess deck. Willingly or not, I can also monitor the conversation on the other side from a bunch of off-duty seamen swearing colorfully about their right to smoke cigarettes. They have lately been curtailed by smoke-sensitive scientists.

Levin's group is studying bristleworms, in particular why so many from the family Dorvilleidae inhabit these seeps (17 species so far, including 10 in one genus). Dorvilleid worms appear to be the underwater equivalent of the Galápagos finches that proved seminal in Charles Darwin's thinking on evolution. All 14 species of finches currently inhabiting the Galápagos radiated from a handful of ancestors blown to sea from South America, making landfall on the largely birdless islands, there to evolve into new species more like blackbirds, wrens, grosbeaks, woodpeckers, and mockingbirds than finches.

Having likewise arrived at the "islands" of underwater seeps and whale falls, the dorvilleid worms build ephemeral communities lasting as long as fuel is available. Like Darwin's finches, these worms are rapid responders, filling empty niches in no time at all, evolutionarily speaking, with fully functioning communities. They are also living examples of the kind of speciations that follow on the heels of mass extinctions.

Listening to the simultaneous griping and negotiating in the library and mess deck, it occurs to me that our floating community of 51 souls aboard Atlantis illustrates the divergent human impulses between competition and cooperation that will, in the near future, seal the fate of all Earth's species—counted, uncounted, ancient, and newborn.

 

WITHIN DAYS OF BOARDING ATLANTIS I'm learning to sort worms. Until today, the seas have been calm enough that staring at tiny living creatures magnified 12 or 50 times in petri dishes full of deoxygenated water has been a hypnotic, through-the-rabbit-hole exercise: foraminiferans like frosted Christmas-tree ornaments, spaghetti worms like exploded dissections gone bad, snails wearing circa-1960 bathing caps with bobbing bacterial filaments, all amid a snow-globe blizzard of gold, mica, and dragonfly-iridescent flakes. We work with paper-thin forceps and glass pipettes, yet these creatures are so delicate that many disintegrate when touched.

The seas have kicked up today, and some of the researchers normally glued to stools along the microscope bar have retired to ride out the bad weather in their bunks. Through my looking glass, the mud world in the petri dish reels from mini-tsunamis, worms flailing, snails spinning in shells, amphipods sprinting on swimmerets, bacterial filaments tying themselves into knots. It's a stomach-churning chaos presumably unknown in their deepwater home.

The truth is, I'm beginning to have qualms. I feel sorry for the worms, some of which, I keep remembering, might be more than 170 years old. My doubts crystallize when Ken Halanych, a marine biologist from Auburn University, tells me I have to dissect the worms out of the tubes they've built, and not just collect the ones floating free. This is all part of the sorting business, of course, seeing who lives where, correlating it with gas measurements of the mud layers they inhabit, quantifying the ecosystem, and searching for new species. Halanych is my friend at the dissecting scope, one of the only scientists, in fact, who seems enthusiastic about the hours I spend there and willing to teach me. But I can't do it.

Even though all these worms brought up from the bottom are destined to die anyway, to sacrifice themselves for science, as the grad students weakly joke, I still can't bring myself to yank them from their glovelike tubes. So I leave the dissecting scope and return to my mindless tasks of labeling Nalgene sample bottles, dubbing the Alvin's dive tapes, assembling tube cores for collecting mud.

Later, I overhear Victoria Orphan, a serene geobiologist from the California Institute of Technology and chief scientist of the other team aboard Atlantis, confess her own squeamishness about worm dissections. Maybe because of this, her chosen work is with the methane-eating bacteria and archaea that fuel the gas-powered food web at the seep. She observes these single-celled creatures through chemistry alone, death throes mercifully invisible.

Orphan's study addresses a pressing issue in the biodiversity crisis. In past warming eras, vast undersea deposits of methane ice may have melted, burping gas into the atmosphere and accelerating global warming. Some scientists theorize that a methane burp precipitated or at least contributed to the Permian-Triassic extinction event approximately 251 million years ago, killing 90 percent of all marine life, and 50 to 70 percent of all terrestrial life.

The fact that little methane seeping from the seafloor today ends up a greenhouse gas is because it's consumed on the bottom by the microorganisms around cold seeps, at least in part. In other words, Orphan's single-celled bacteria and archaea keep our world livable to some extent, and maybe to a critical extent in the years ahead—a reminder of the power of the meek, including the unknown power of the undiscovered meek, all 10 to 100 million species of them.

For a while, I switch to Orphan's lab—younger, noisier, more crowded, and less reverent. The students on her team name their tube cores for rappers and discuss the quantity of bling in their mud. They are powerfully, almost alarmingly, focused on their work, barely breaking to take note of schools of dolphins on our bow, humpback whales, soaring albatross—which they refer to, wistfully or dismissively, as charismatic megafauna.

I wonder if anywhere along their educational route they are encouraged to consider science's own footprint. The cold seeps we're visiting are frequented by teams from all over the world. Every submersible drops its ballast before ascending to the surface, and popular dive sites are slowly but surely being paved with metal brick weights. When I mention this, I'm told the metal will rust away in the seawater. When I point out that the seeps are anoxic environments, nearly devoid of rust-inducing oxygen, they blink. Like Mount Everest, Hydrate Ridge is littered with the refuse of exploration.

A week later, at Eel River Seeps off California, Alvin brings up big slabs of rock punctured with deep, perfectly round holes. The two returned scientists tell me of scores of holes as far as they could see down there. Everyone is excited by the doughnut rocks. There's speculation about bubbling methane "chimneys." Yet somehow the holes look familiar to me. They remind me of the tube cores I spend nights reassembling for the next day's dive. I walk to my station and return with a tube core and plug it into a doughnut hole. It's a perfect fit—with this hole, and that hole, and the next one. It fills all the holes I see and test as impeccably as a cookie cutter.

Only Anand Patel, a grad student on Levin's team, seems interested in this; the other scientists studiously avoid it. Since tube cores can sample soft sediments, not hard rock, Patel and I speculate the process of biopsying might prompt a reaction that turns the mud to stone, like scar tissue. He's interested in the chemistry of it. I'm interested in the possibility that all the scientists who love mud so much may be hastening its demise here.

But who knows? Maybe science's footprint will prove useful eventually. With the whale falls largely gone, perhaps a new life-form will evolve to feed on iron ballast.

Page 3 of 5