© Jon Benstead/University of Alabama
David Manning, a University of Georgia doctoral student, and John Kominoski, a former UGA postdoctoral researcher who is now an assistant professor at Florida International University, perform maintenance on the pump used to add nutrients to one of the streams in their experiment.
An important food resource has been disappearing from streams without anyone noticing until now.
In a new study published March 6 in the journal Science
, a team of researchers led by University of Georgia ecologists reports that nutrient pollution
causes a significant loss of forest-derived carbon
from stream ecosystems, reducing the ability of streams
to support aquatic life.
The findings show that the in-stream residence time of carbon from leaves, twigs and other forest matter, which provide much of the energy that fuels stream food webs
, is cut in half when moderate amounts of nitrogen and phosphorus are added to a stream.
"This study shows how excess nutrients reduce stream health in a way that was previously unknown
," said the study's lead author Amy D. Rosemond, an associate professor in the UGA Odum School of Ecology.
Stream food webs are based on carbon from two main sources. One is algae, which produce carbon through photosynthesis. Nutrient pollution has long been known to increase carbon production by algae, often causing nuisance and harmful algal blooms
. The second source is leaves and bits of wood from streamside forests. This forest-derived carbon typically persists year-round, making it a staple food resource for stream organisms.