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Evolutionary insight

New Harbor and forams may offer window into explosion of multicellular life a half-billion years ago

 

Explorers Cove, on the west side of McMurdo Sound, is the gateway to the Taylor Valley, one of the most intensely studied areas in Antarctica. The name itself is a sort of homage to the large number of people who have explored the area for more than a century.

For scientist Sam Bowser, the ice-covered cove is also a portal back in time to explore a period more than half a billion years ago when the dominance of single-celled organisms suddenly — at least in geologic time, as interpreted by the fossil record — ended with the rapid evolution of multicellular life.

Explorers Cove is a particularly good place to study the so-called Cambrian explosion thanks to the large number of “primitive” foraminifera species found on the seafloor at shallow depths, according to Bowser, a cell biologist with the New York State Department of Health’s Wadsworth Center in Albany.

“If the present is the key to the past, and if the way the species behave today is comparable to how they behaved 540 million years ago … then [the forams] must have had an impact on how ancient lifeforms evolved,” said Bowser, who has studied the biology and biodiversity of the early-evolving, single-celled forams in Antarctica since 1984.

“Without a time machine, you’re not certain about any of this stuff, but it gives us ideas,” he added.

Some of those ideas revolve around such evolutionary traits as building tests — or, as Bowser puts it, why a cell needs a shell — and how voracious forams might have shaped the emergence of more complex life. Certain species are as large as a BB pellet and capable of devouring a juvenile starfish.

“It’s a unique place where you have such a diversity of the single-chamber organisms,” said Jan Pawlowski, an associate professor at the University of Geneva who has worked with Bowser for a number of years on the Explorers Cove foram population. He is an expert in the molecular evolution and ecology of protists, which includes mostly unicellular or simple organisms.

“If you want to understand the evolution, how the animals evolved, we have to understand how the lineage leading up to animals evolved,” he said.

Forams typically blanket the deep ocean, thousands of meters below sea level. But cold-water conditions in Explorers Cove have created an ideal natural laboratory where the early-evolving species of forams thrive. More than 200 species are believed to exist in that part of McMurdo Sound, with at least 20 new species yet to be catalogued by Bowser and his colleagues.

Many of those species in Explorers Cove construct their shells by gluing together particles from the surrounding environment. Each species is very particular about the materials, even the size, of the chosen grains.

“How a cell is able to pick different types of particles from the environment, put them together in this type of a pattern, that’s something that’s just wild and crazy, and we still don’t understand it,” Bowser said.

The forams make use of countless pseudopodia, a “branching mass of writhing, seething cylinders,” which can autonomously move around and collect things, Bowser explained. Picture an octopus on a miniature scale, with numerous, wispy tentacles that scour the environment like a super-sticky conveyer belt.

A shell for the benthic, or seafloor, forams in Explorers Cove would give them a slight evolutionary advantage in collecting food, getting all of those little arms up away from the muddy surface to grab a passing bacterium or other bit of nutrient.

“This is a way to get food: You build a shell, and you tailor that shell to optimize your ability to capture food. I can’t think of a better driving force for the evolution of something,” Bowser said.

The how and why of foraminifera behavior and ecology is a constant topic at the New Harbor field camp on the shore of Explorers Cove, where Bowser and his team typically spend two months every Southern Hemisphere summer in a revamped Jamesway tent that serves as bunkroom, kitchen and living room.

What’s not always typical are the field team members who join Bowser from year to year. A believer in combining art and science, Bowser invited landscape painter Laura Von Rosk to join him on this past season’s expedition, which involves divers plunging through holes in the sea ice and collecting sediments from the seafloor down to about 20 meters.

Later, under the microscope, the violent realm of the forams is revealed to the eye.

“Being immersed in somebody else’s research is a unique experience,” Von Rosk said while shoveling bits of ice out of a dive hole on a warm Antarctic summer day. “It’s like stepping into somebody else’s world.”

“It’s very intense living with six other people – and I mean that in a good way, too,” she added.

It’s also been a learning experience for Danielle Woodward, a recent marine science graduate from the University of Hawaii at Hilo who has been scuba diving since she was 12 years old. She got certified in dry suit diving on the tropical island before going to Antarctica for the 2011-12 season.

Diving in water just below the freezing point takes a lot more energy than swimming through the bathtub-warm waters of Hawaii, Woodward said. Not to mention the physical struggle of squeezing into a dry suit, the skintight hood and the lobster-claw gloves.

“It takes about 45 minutes for us to get in our gear,” she said. “By the time you get your work done and back to the surface, you’re whipped.”

One of her principal jobs while under water is to drill shallow sediment cores, which the researchers will use for both physical counts of forams and more high-tech genetic sequencing techniques to identify species. Most of the work is done at depths of less than 25 meters.

“When you’re coring, you’re not necessarily pushing the depth, you’re pushing the time. It takes the entire dive just to core. Then you have to bring up the cores,” Woodward said.

One of her favorite dive spots is a place called Ice Wall, where a chunk of ice from the last ice age, which peaked around 18,000 years ago, is preserved under the water.

But Explorers Cove isn’t just a place to understand the past, Bowser repeatedly insisted, thinking beyond foraminifera. The relatively ice-free coast and the misshapen ice — cracked and dirty with sediment, with moats of fresh water snaking along the shore — could be a picture of Antarctica in the not too-distant future as the ice sheets and glaciers recede.

“This could be a real model of what we expect Antarctica to look like,” Bowser said. “I think this is a very important place, and I think much smarter people than me should come in and take a look at it. I have a nice camp all set up.”

He added, on a more serious note: “Without good knowledge of the present, you’ll never figure out the past. Nor will you ever be able to confidently predict the future.”

NSF-funded research in this story: Sam Bowser, New York State Department of Health, Award No. 0944646.

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Curator: Peter Rejcek, Antarctic Support Contract | NSF Official: Winifred Reuning, Division of Polar Programs