Restricting nitrogen in fertilizers may not help algae problem

A professor of the University of Alberta has found that restricting the use of nitrogen-based fertilizers has little effect in reducing the problem of algae in lakes.
In a Canadian Press report, Professor David Schindler said that he and his fellow researchers began experimenting on algae 37 years ago on lakes in northern Ontario. After this prolonged period they found that algae bloomed in proportion to the amount of phosphorous added to the water, whereas the availability of nitrogen had little effect. Common fertilizers contain both nitrogen and phosphorous.
Schindler’s team found that the algae were feeding on phosphorous, but at the same time “fixing” nitrogen from the air. This made the algae problem even worse because the particular algae that fixed nitrogen from the air was unpalatable to small insects and snails and so thrived and overtook the other types of algae.
Schindler has an international reputation for his work in freshwater ecosystems and proved in the 1970s that phosphorous was key in controlling algae blooms.
His recent findings on nitrogen contradict the efforts that are often taken to control algae by imposing restrictions on nitrogen in fertilizers.
Schindler ran his experiment over 37 years at a small lake in the Canadian Shield in northwestern Ontario. He was co-author of a paper on the research that will be published August 12 in the Proceedings of the National Academy of Sciences.