University of Southern California

Hunting Seaweed, Dodging Penguins

Mark Denny, January 15, afternoon — When I think of Antarctica, I first think of ice and snow and freezing cold water. As a zoologist, I then find my mind turning to the unusual animals that live in that environment: penguins, Weddell seals, whales.

What I certainly do not think of is seaweeds.

It thus came as a surprise to me to find out that there are at least three species of seaweeds that live attached to the sea floor just under the sea ice, here in McMurdo Sound. Their presence raises questions: How do photosynthetic organisms survive the long, dark winter, given that the only time they have access to sunlight is the late summer (basically, February) when the sea ice breaks up? How do they avoid being scraped off the bottom by the ice the rest of the year?

To begin to answer these questions, we made an expedition to Cape Evans, 10 or so miles north of McMurdo Station here on Ross Island. Cape Evans is the site of the hut from which Robert Falcon Scott started his ill-fated trek to the South Pole in 1911. The hut is still there, literally frozen in time, and it made a somewhat surreal backdrop to our trip.

It is roughly a 10-minute helicopter ride from McMurdo to Cape Evans, and the helicopter dropped us off near the shore, just east of Scott’s hut. We then spent the better part of an hour schlepping the equipment for two divers out to the two holes that had previously been drilled through the sea ice 100 yards from shore, hopping cracks in the ice as we went.

Each dive hole is about four feet in diameter, and once we reached them it took a few minutes with ice axes and shovels to clear them of the ice that had formed since they had last been used. Our presence, and the unusual activity, attracted a trio of Adelie penguins, who waddled over to take look. They seem to have no fear of humans, boldly approaching within a couple of feet to check us out.

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While most of us were engaging the penguins, Jim Leichter and Shawn Horner, our divers, insinuated themselves into their dry suits and, after carefully checking their gear, slipped into the dive hole. The air temperature was roughly +20F, and standing there in the wind, I couldn’t imagine myself getting in that water. My fingers were either aching or numb from the little contact I had had with the +28F water while I was helping the divers suit up, and the thought of dunking my whole body gave me chills.

Jim and Shawn were down for half an hour, giving me plenty of time to take pictures of the penguins (still wandering around as if on holiday), and of Mt. Erebus and the Barne glacier which loom off to the northeast of the Cape.

The dive was a great success: In their half-hour under the ice, Jim and Shawn found and collected plenty of one species of seaweed, Phyllophora antarctica, a red alga with flat blades a couple of inches long. In addition, they brought up several small fish, some sea urchins, and a sea star, all of which we will use in our experiments.

After repeating the whole procedure (penguins and all) at the second dive hole, we quickly schlepped all the equipment back to the landing site, hustling to be packed and ready by the time the helicopter was scheduled to pick us up.

Of course, as so often happens with field trips, our hurry was followed by a wait — the helo was delayed on another job, providing us with the time-honored Antarctic opportunity to simply sit and look around. In the five hours we had been at Cape Evans, the angle of the sun had changed substantially, giving a whole new look to the area. Clouds came and went around the peak of Erebus. The ice breaker came and went, clearing the channel to McMurdo. Icebergs floated along. A mating pair of skuas soared and swooped, and a seal hauled out of the dive hole we had last used.

It was almost a shame when the helicopter finally arrived. Equipment loaded, tired and hungry, we headed back to town to start our experiments on the interaction of seaweeds with sea ice.

Mark Denny holds a named chair in marine sciences biomechanics at Stanford University.