© Greg Dumas Scientists found increased phosphorus during sampling of remote North American lakes. Janice Brahney gathers water from a site in Canada.
(
Environ. Sci. Technol. 2016, DOI:
10.1021/acs.est.5b05950).
Rising phosphorus measured in these water bodies could lead to toxic algal blooms and degraded habitat for fish, birds and frogs.High phosphorus levels in streams and lakes typically result from sewage discharge and agricultural runoff. But the new work finds phosphorus pollution in remote areas far from such sources, leaving researchers scratching their heads about where it came from.
What evidence they have suggests the phosphorus inputs are probably linked to climate change, and are unlikely to be tamed anytime soon. Phosphorus is an essential nutrient. But when levels top 10 µg/L in water bodies, ecosystems start to change.
The kinds of algae that feed a healthy ecosystem begin to disappear, and undesirable species take over, says
Emily H. Stanley, an aquatic biogeochemist at the University of Wisconsin, Madison, who was not part of the study.
One group of undesirables, cyanobacteria, can produce toxic blooms that threaten drinking water sources and cost the U.S. economy over $2.2 billion per year.
To track the health of the nation's waters, the Environmental Protection Agency monitors a selection of lakes and streams, measuring the concentration of important ions and nutrients every five years.
EPA stumbled on the new result while analyzing these data, says John L. Stoddard, a biogeochemist with the EPA. Phosphorus was the only measured nutrient that changed, he says. Uniformly across the country, median total phosphorus in streams more than doubled from 26 µg/L to 56 µg/L over the last 10 years. In lakes, levels rose from 20 µg/L in 2007 to 37 µg/L in 2012.
