Lowly Icelandic midges reveal ecosystem's tipp...( MADISON - The midges that periodical...)

MADISON - The midges that periodically swarm by the billions from Iceland's Lake Myvatn are a force of nature.

At their peak, it is difficult to breathe without inhaling the bugs, which hatch and emerge from the lake in blizzard-like proportions. After their short adult life, their carcasses blanket the lake, and the dead flies confer so much nutrient on the surrounding landscape that the enhanced productivity can be measured by Earth-observing satellites.

Now, however, the midge Tanytarsus gracilentus and its periodic, sky-darkening hatches are giving scientists an opportunity to assess how the slightest environmental perturbation can tip the precarious balance of an ecosystem and push it into altered states with unknown consequences. Writing this week in the journal Nature, a team led by University of Wisconsin-Madison zoologist Anthony Ives describes an ecosystem population dynamics model built on the flies of Lake Myvatn, showing how even slight human-induced changes can irreversibly alter the balance of nature.

"If our model is correct, the magnitude of these cycles should be sensitive to even the smallest changes in the hydrology of the lake," explains Ives, who conducted the research in collaboration with rni Einarsson and Arnthor Gardarsson of the University of Iceland, and Vincent A. A. Jansen of Royal Holloway, University of London.

The new study is important because it suggests the possibility of constructing powerful models that scientists can use to assess what may occur as a result of both natural changes and human-induced changes such as those linked to global warming.

"It doesn't take much noise to cause big changes in the pattern," says Ives of phenomena, natural or human-induced, that can tip the balance of an ecosystem. "Even small amounts of environmental noise cause very different biological processes to dominate. And even if you understand the causes, you can't predict the effects."

I
'/>"/>