Reducing how much nitrogen enters a lake has little impact on algal blooms

Yet another paper has been published showing that reducing the concentration of phosphorus, not nitrogen, is the key to halting algal blooms.

Articles published at https://www.manitobacooperator.ca/news-opinion/news/nitrogen-reduction-not-the-path-2/ and https://www.iisd.org/media/reducing-how-much-nitrogen-enters-lake-has-little-impact-algal-blooms-find-canadian-scientists review a recently published paper in Springer’s Ecosystems journal that presents the results of a 46-year whole-ecosystem experiment on Lake 227 at IISD Experimental Lakes Area, northwestern Ontario, Canada. The journal paper is titled “Biological Nitrogen Fixation Prevents the Response of a Eutrophic Lake to Reduced Loading of Nitrogen: Evidence from a 46-Year Whole-Lake Experiment.

Work on this lake was first undertaken in 1969. Since then, scientists have been manipulating the carbon, nitrogen and phosphorus concentrations to investigate the nutrients responsible for algal blooms.

Throughout the experiment, researchers have been continually adding phosphorus. However, 40 years ago, researchers began reducing the amount of nitrogen they were adding to the lake, and from 1990-2013, they cut artificial nitrogen loading to zero. Despite these dramatic cuts in nitrogen loading, algal blooms continued to cover the lake.

The lead author of the paper and Research Scientist at IISD Experimental Lakes Area, Dr Scott Higgins said:

“We have been researching the role of artificial nitrogen in algal blooms for almost 50 years now, and these latest results clearly demonstrate that ceasing nitrogen loading into lakes has little effect on the size or duration of algal blooms”. “A number of algal species can make up for nitrogen deficits by fixing atmospheric nitrogen that is dissolved in the water. What is clear here is that phosphorus is the key driver of algal blooms in lake environments”.

Dr. Michael Paterson, Senior Research Scientist at IISD Experimental Lakes Area and secondary author on the paper is quoted as saying:

“When governments are tackling algal blooms while working with limited resources, these results demonstrate that their efforts should be firmly focused on reducing phosphorus loading in lakes”.

Conclusions drawn from the research highlight the importance of reducing the concentration of phosphorus entering and remaining in the lakes.

Phoslock is a phosphorus binding product that can be used safely in natural lakes to significantly reduce the concentration of bioavailable phosphorus that feed harmful algal blooms.