Interview with Tim Shank
by Lonny Lippsett, photo by Chris Linder

Tim Shank

WHOI biologist Tim Shank tests a light on the Camper vehicle, getting it prepared for missions to photograph and sample rocks and animal life around hydrothermal vents, if we find any.

What is your role on this expedition?
I’m the lead biologist. It’s fabulous to test these underwater, under-ice vehicles and have them go and find hydrothermal vents autonomously, but in the end, we’re really trying to see what life is up here around vents on the Arctic Ocean seafloor. So my role is to keep in mind that the ultimate goal is to bring those animals back and look at the kind of vent conditions they’re living in.

What kinds of conditions are those?
The vent fluids are rich in chemicals, such as hydrogen sulfide or methane. But vent animals have evolved to use these harsh chemicals as nutrients. We’re talking about 10-foot long tubeworms that have no mouth, or eyes, or gut, or clams the size of dinner plates, large mussels, and swarms of shrimp. Actually, it is bacteria living inside or on the animals—whether they’re in a sack inside tubeworms or in the gills of mussels or clams—that convert the chemicals in the vent fluids into energy that the tubeworms and clams can use. A variety of vent life has evolved to take advantage of this strategy. So the discovery of vents revolutionized our understanding of how life could thrive on Earth.

Vents were first discovered in Galápagos in 1977 by a team of geologists. They didn’t anticipate finding these animals. They were looking for where heat would be coming out of the Earth’s crust.

Prior to the discovery of hydrothermal vents, it was widely held that life really didn’t exist without the use of the sun, that it was mostly a desert (albeit a diverse one) at the bottom of the ocean, and that deep-sea animals survived off organic debris that rained down from the surface. But vents changed all of that. Nutrients were coming up from inside the Earth that life could make use of. They didn’t really need the sun, except for some oxygen. And the seafloor turned out to be a highly dynamic place.

Where are hydrothermal vents found on the seafloor?
Hydrothermal vents occur along the mid-ocean-ridge, but not continuously along a ridge. You have a network of habitats, like they way you have Miami, Washington, D.C., and Boston along Interstate 95.

Different types of species are found only in certain places. So along the East Pacific Rise, (the mid-ocean ridge in the eastern Pacific Ocean), and along South America, down from Galápagos Islands, we find areas dominated by tubeworms, large clams, and mussels. But if we go up north, off of the coast of Oregon and Washington, the ridge has a different species of tubeworms than what we see in southern Pacific, and a notable lack of mussels.

In Atlantic Ocean vent sites, it’s completely different. We don’t see any tubeworms. The Atlantic is dominated by huge swarms of shrimp. If we go to the western Pacific, those vent sites over there are dominated by different species of hairy gastropods—those are large snails.

So one of the vexing questions we’ve had for a long time is what causes and maintains these so-called biogeographic provinces? How do populations on the seafloor get separated so that different species evolve? That’s why the Artic Ocean is one of the key places to explore.

The Arctic Ocean is a virtually enclosed basin. Water can flow in through the Bering Strait and out through the Fram Strait—but only at a shallow level. There’s very little connection between the deep water of the Arctic Ocean and the rest of the world’s oceans.

When seafloor spreading began in the Arctic some 58 million years ago, the Arctic Ocean basin was almost completely isolated from any water connection to the Atlantic or the Pacific. It has only been for the past 19 million years or so that a small amount of deep water has flowed into the Arctic from the Atlantic, so whatever life has been evolving along the deep Gakkel Ridge has likely been doing so for tens of millions of years or so in isolation from other oceans.

That leads us to ask, “Well, what fauna is going to be in the Arctic?” We really don’t know. It’s sort of like thinking about Australia and how 100 million years ago that became disconnected from Antarctica, and now we’ve got kangaroos there, and only there. We’ve got koalas and all kinds of different animals that we don’t see anywhere else. So what is the evolutionary history of the animals that live in the Arctic, on the Gakkel Ridge? That’s what we’re trying to find out.

I have no idea what the Arctic animals are going to look like. I have to forget my preconceived notions. But it’s safe to say that, if they’re there, they’re going to have novel adaptations. They may do things that we may not even know about yet. They may be living off nutrients that we haven’t discovered yet. So it’s a dream for an evolutionary biologist like myself to be able to go there and find those animals.


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