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Nov 062009
 

By Barbara Kessler
Green Right Now

As debates about climate change — does it exist and how serious is it? – rage on, many scientists continue to uncover more and more evidence that atmospheric pollution is having negative effects on Earth, right here and now, climate change or not.

Scientists studying the chemistry of lakes reported in a study published this week that atmospheric nitrogen released from the burning of fossil fuels and the widespread use of fertilizers in agriculture is altering the makeup of even remote bodies of water.

Alpine Lake

Green Lake 5 in Colorado (Photo: James Elser/ASU)

The study,  published in Science, found elevated nitrogen levels in alpine and subalpine lakes in Colorado, Sweden and Norway.

The added nitrogen changes the food composition of the aquatic environment, first by feeding the phytoplankton, and then other organisms as it moves up the food chain. With the lake’s plant life getting a disproportionate amount of nitrogen relative to other necessary minerals, like phosphorus, the “fundamental ecology,” of the lake is changed, according to the researchers.

This result of this new balance of minerals means that the phytoplankton, in essence, are eating differently (rather like when we hominids don’t get all our vitamins). The excess nitrogen restricts how much phosphorus they can absorb, and they become, in scientific lingo, “phosphorus limited.” And that’s not a good thing.

“We know that phosphorus-limited phytoplankton are poor food – basically ‘junk food’ for animal plankton, which in turn are food for fish,” said James Elser, a limnologist (people who study fresh water environments) in the School of Life Sciences at Arizona State University, who lead the study of collaborating US and Scandinavian scientists.

“Such a shift could potentially affect biodiversity,” Elser said. “However, we don’t really know, because, unlike in terrestrial systems, the impacts of nitrogen deposition on aquatic systems have not been widely studied.”

In other words, it’s possible that the lake life will adapt. Or not.

Elser’s collaborators include researchers Tom Andersen and Dag Hessen from the University of Oslo; Jill Baron of the United States Geological Survey and Natural Resource Ecology Laboratory at Colorado State University; Ann-Kristin Bergström and Mats Jansson with Umeå University, Sweden; and Koren Nydick of the Mountain Studies Institute in Colorado, in addition to members of his own group in ASU’s College of Liberal Arts and Sciences, Marcia Kyle and Laura Steger

Elser and colleagues were supported by a grant from the National Science Foundation.

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