UBC researchers study ocean stress on seaweed

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Pity the poor stand of seaweed, battered without relief by endless ocean waves. It cannot move away for a break, or duck low. It can only endure.

Researchers at the University of British Columbia were curious about how the shape of seaweed affects the drag it experiences as they attempted to understand "how anything can survive in these really stressful habitats, because they're experiencing these forces every, say, 11 to 20 seconds," Patrick Martone, an associate botany department professor, said in an interview.

"Mobile animals can hide. They can run away when the storms hit. They can hide in cracks or crevices or at least hunker down and hold on tightly."

Not seaweed, which clings to rocks with root-like appendages called holdfasts, which squeeze into small spaces, and a natural adhesive.

But when it came time to recreate this in a UBC lab, the team decided to make seaweed on campus from latex that they cut into seaweed-like shapes with a laser beam. The imitation stuff worked.

"It wasn't a matter of convenience or a matter of laziness to use this artificial seaweed," said Prof. Martone, who is now on sabbatical in California collecting seaweed and working with colleagues at the University of California, Berkeley and Stanford University.

"They had a specific role, and the role was we needed to precisely control both size and shape. Seaweeds are extremely variable in the way they can look. Their shape can differ from rock to rock on the coast. If we had just gone out to collect wild seaweed, we could not have drawn the conclusions that we did because we would have been comparing apples and oranges."

During a lab visit, researcher Sam Starko showed the test seaweed – green shapes, some with branches and others without. Altogether, they looked like the creations of an especially gifted child in art class. But function and shape were more important than appearance.

In the basement lab, researchers did their tests with a flume machine. The setup against a wall has a long rectangular water tank resembling an aquarium. It is bracketed by a u-shaped, white pipe. Researchers set the speed of water funnelled through the pipe. Velocities for the tests reached up to 3.5 metres per second.

The seaweed samples were hung into the tank from hooks with devices in them that measured the drag they experienced. Some of the stand-in seaweeds had branches. Other samples did not. The team was interested in how the varied samples experienced drag.

"We wanted to understand how they were experiencing these big waves and if there was any kind of cost that went along with branching," Prof. Martone said.

Mr. Starko said one of the research challenges was photographing the tests to get useful imagery. The team had to figure out, for example, how to get bubbles out of the flume.

It will take countless experiments and further study at UBC to understand the issue fully. At one point, the team considered using real seaweed. They cut out test shapes from actual seaweed with an Exacto knife. But the real stuff dried up, and the shapes were not consistent.

Engineering student Barry Claman figured out how to use computer-assisted design and a laser beam to cut shapes from latex.

At first, Mr. Starko said, it seemed a bit odd. "But once we got going on it, it was clear, it was a really great idea," he recalled.

The samples are in storage in the lab.

"Maybe some other undergrad will come up with a project idea that involves them or maybe they will sit on the shelf. Time will tell," Mr. Starko said.