OAK RIDGE, Tenn., March 17 (UPI) -- U.S. scientists have found tiny organisms in rivers are vital in removing nitrates -- nitrogen pollution caused by human activity -- from streams.
In the first phase of the study, led by Oak Ridge National Laboratory, researchers added small amounts of an uncommon non-radioactive isotope of nitrogen to 72 U.S. and Puerto Rican streams.
"We found the nitrate was filtered from stream water by tiny organisms such as algae, fungi and bacteria," said Patrick Mulholland, lead author of the study.
In the second phase the scientists studied nitrate removal from water within river networks. Such networks develop as small streams flow into larger streams and rivers.
"Our model showed the entire stream network is important in removing pollution from stream water," Mulholland said. "In addition, the effectiveness of streams to remove nitrate was greatest if the streams were not overloaded by pollutants such as fertilizers and wastes from human activities."
The scientists concluded streams and rivers are effective filters that can help prevent nitrate pollution from reaching lakes and coastal waters where it can cause noxious algal blooms and lead to oxygen depletion and fish kills.
The study appears in the journal Nature.
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