Unravelling the food web

Brent Young enlists community support to trace the feeding patterns of Arctic seals

It may look like a snow-covered wasteland but the Arctic is actually teeming with life, both on land and under water. The Far North is so vast—and so remote—however, that very little is known about its complicated ecosystem.

Brent Young hopes to help change that. In 2009, he worked on a study that looked at the diets of three types of Arctic seal. He wanted to find out how they fit into the northern 'food web'. (The food web is a map of the connections between predators and prey, arranged in a series of levels. Humans are at the top; small creatures like plankton are at the bottom, with larger animals such as fish and seals above them.)

"Studying the seals and their diet is very important to understanding what else is going on in the ecosystem," Brent explains.

He did the research as his university honours thesis, focusing on ringed, bearded, and harbour seal populations on the western coast of Hudson's Bay. As part of the project, he had to collect seal tissue from a number of different animals. Since he couldn't travel up north to collect samples himself, he relied on the help of northern communities.

A real group effort

His team mailed sample kits—including freezer bags with labels—to each community.

"We let them know which organs we wanted from the seals they hunt. They collected them and sent them to us here in Winnipeg," he explains.

Following a chemical trail

When the samples arrived in Winnipeg they were tested for various chemicals. The process helped reveal what and where the animals had been eating.

"Basically the idea is that when a predator consumes prey, chemical signals from the tissue of the prey become part of the tissue of the predator," Brent says.

As expected, his research showed that harbour seals mainly eat fish, while ringed seals feed on a combination of fish and crustaceans like shrimp, and bearded seals eat invertebrates such as clams.

There were also some surprises.

Brent says he and his team found differences in age classes for all three species. This means that as the seals age, their position in the 'food web' seems to change. Adult harbour and ringed seals seemed to eat larger prey than their pups. But young bearded seals feed at a higher level on the food web than adults: while most fully grown bearded seals feed on things like clams, their pups eat more shrimp, which are higher in the food web.

Brent hopes his findings, which show how complex the northern food web is, will provide a baseline for future studies and inspire others to take a closer look at the still-mysterious world of the Arctic ecosystem.

"This will really give us an idea of what's happening over the long term," he says, "and how these changes may affect the other parts of the ecosystem."