IISD-ELA research shows nitrogen removal doesn’t decrease bloom size

[Canada] A study within a study that has been ongoing for almost half a century at the IISD-Experimental Lakes Area (IISD-ELA) freshwater research facility provides a clearer picture on how to deal with algal blooms.

Dr. Scott Higgins is a research scientist at IISD-ELA and the lead author of the study on the effects of nitrogen on the growth of algal blooms which was recently published in Springer’s Ecosystems journal.

He said the broad study that’s occurred since 1969 has been looking at what drives algal blooms in lakes, which are the biggest water quality problem worldwide.

“At that time, there were big arguments going on about the relative importance of three different nutrients or elements algae need to grow and all plants need: carbon, nitrogen and phosphorus,” Higgins said. “Because of the high cost involved, that was the whole reason why the ELA was built, to try and answer this question because it was so costly and they wanted to make sure they got it right before they developed policy.

At the start of the experiment, researchers artificially added nitrogen and phosphorus to one of the facility lakes, which created a large bloom. Higgins said that showed carbon wasn’t part of the problem.

Then in 1975, they cut the amount of nitrogen going in and stopped adding nitrogen entirely in 1990.

“If nitrogen was the culprit, you would expect the size of the blooms would decline, but they didn’t,” he said.

The focus of the recent published study was an experiment conducted in 2011 that was trying to understand how the blooms were getting their nitrogen if it wasn’t being added to the lake, since it has a very high nitrogen requirement.

The study investigated the hypothesis that the blooms were able to get enough nitrogen through a process called nitrogen fixation. Higgins explained that nitrogen gas makes up 70 per cent of the atmosphere and readily dissolves into water. Some algae species, although not all, can use that source of nitrogen. The researchers found that the algae species in the lake had changed but the overall size of the bloom didn’t.

“What our studying is saying is we should be focusing on, in terms of policy management is the phosphorus,” he said. Although more studies and evidence is required, he added that eliminating phosphorus runoff into lakes is the way to go.

However, Higgins said there’s no downside to reducing and removing nitrogen from freshwater aside from the high financial cost. “Certainly in some agricultural situations, the pollution of groundwater is a problem, but it’s not going to do anything for algal blooms.”


Photo: A study done at the IISD-Experimental Lakes Area found that reducing or removing nitrogen from lakes doesn’t cause a decrease in algal bloom size. FILE PHOTO/POSTMEDIA NETWORK

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