Summer 2008

Field Notes

Entomologist Claudio Gratton and limnologist Jake Vander Zanden (background) survey a stark grassy landscape amidst a swarm of midges, gnat-like bugs that rise in huge numbers from a remote lake in Iceland. Jack Donaldson

From a distance, the surface of Iceland’s Lake Myvatn seems to be cloaked in a dense, low-lying fog. A closer view reveals that the fog is alive, and it’s thrumming. Billions of tiny, gnat-like midges rise from the lake and drift over its surrounding lands—so many that in Icelandic, Lake Myvatn means “midge lake.”

To entomologist Claudio Gratton, these swarms are more than just a natural curiosity. He sees a neat system for transporting food and energy from one habitat to another—one that might have lessons for Wisconsin agriculture.

As an insect ecologist, Gratton is keen to understand how what insects do in one part of the landscape affects what happens in other parts. Lake Myvatn offers an extreme example of this interaction. Midges hatch in the lake, feeding on tiny organisms in sediment as larvae. As adults, they rise from the lake to mate, gradually drifting en masse over nearby lands. And that’s where most of them die, creating a mass movement of living organisms from water to land.

Arni Einarsson, University of Iceland

In each of the past two summers, Gratton has taken a team of students and researchers to Lake Myvatn to study this phenomenon. They’re particularly interested in what role the midges play in the ecosystem once they die: Do they decompose, providing nutrients for the soil? Do they fall prey to spiders or other insects?

But what the researchers learn will not apply only in Iceland. Gratton sees his research there informing his work with Wisconsin potato and soybean growers, potentially revealing new strategies for controlling agricultural pests.

“I’m interested in how pests and their predators move in the landscape,” he explains, noting that what he learns in Iceland can be applied to the natural enemies of crop pests such as aphids and potato beetles. “It’s all about understanding ecosystem linkages.”

Of course, the stark moors of Iceland are very different from Wisconsin’s relatively lush, diverse landscape. And that’s why it’s a perfect place to study habitat linkages, Gratton says.

“It’s simple and it’s dramatic. You can (follow) the movement of these organisms with your eyes,” he says. “This is a neat model for looking at really strong ecosystem linkages—the kind of linkages we’re trying to understand in a landscape like Wisconsin, where it’s a patchwork of agriculture and non-agriculture.”

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