Decreasing algal blooms in freshwater

Professor Steven Chapra, Louis Berger Chair of Civil and Environmental Engineering

A team of American and Canadian researchers, including Professor Steven Chapra, has demonstrated that reducing phosphorous decreases algae blooms in freshwater. In the past ten years, some scientists have argued that controlling phosphorous alone was not enough, and that nitrogen inputs must also be reduced. The research team found that reducing nitrogen won’t actually help the problem of eutrophication (the proliferation of algal blooms and related changes in lakes), which is one of the leading causes of freshwater pollution and costs an estimated $2.2 billion a year in the U.S. alone.

In many ways, Chapra and colleagues say, this is good news—controlling inputs of phosphorous is much less costly than controlling nitrogen. “It is obvious in retrospect that the reduction of nitrogen would have been largely futile and wastefully expensive,” said Chapra.

The team detailed their research in a recent feature article in Environmental Science & Technology.

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