By changing the composition of fish populations in a lake, scientists have found a switch by which the flow of carbon between lakes and the atmosphere can be turned on, off, or reversed.
The finding, reported by researchers from UW-Madison in this week's (July 11) edition of the journal Science, is the first to show that only slight rearrangement of an intact ecosystem's food web can directly influence the atmosphere.
The discovery is important because it demonstrates that single, seemingly subtle changes in ecosystems can have far-reaching consequences, and are capable of disrupting the fundamental biogeochemical processes of the Earth.
"Linkages in ecosystems are both stronger and stranger than we imagined," said Stephen R. Carpenter, a UW-Madison limnologist who, with fellow limnologists Daniel E. Schindler and James F. Kitchell, authored the report. "Biological processes have powerful feedbacks to processes that are normally thought to be purely physical or chemical in nature."
While lakes occupy a very small area of the planet's surface, the discovery that simple biotic change is capable of altering the exchange of carbon between the atmosphere and the Earth's surface raises questions of global significance, said Carpenter.
"To what extent could fertilization of the oceans and alteration of oceanic food webs affect global carbon cycles? In fact, runoff from land is now enriching coastal oceans to unprecedented levels, and industrial fishing is causing massive changes in marine food webs. So the global experiment is underway," said Carpenter.
Carbon, an essential nutrient in lakes, typically flows from the land in the form of dead leaves and other organic matter that accumulates and decays underwater. Usually, these processes lead to a surplus of carbon dioxide in lakes. Excess carbon in a lake is released as a gas, carbon dioxide, to the atmosphere.
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Contact: Stephen Carpenter
srclake@macc.wisc.edu
608-262-8690
University of Wisconsin-Madison
10-Jun-1997