Lake Winnipeg shows nitrogen, phosphorus spike

The massive floods in Manitoba's Red River Valley back in the spring will result in more algae growth on Lake Winnipeg, experts say.

The Red River floodwaters gathered soil and debris from hundreds of thousands of flooded hectares south of the lake, sending phosphorus and nitrogen levels to about 20 per cent higher than normal in Lake Winnipeg, Canada's fifth-largest freshwater lake. 

Gordon Goldsborough, a biology professor at the University of Manitoba, said any increase in phosphorus or nitrogen in Lake Winnipeg makes the lake vulnerable to algae, which produces toxins that are hazardous for fish and other wildlife.

Massive algae blooms in the north basin of the lake have been visible for several years. Beaches in the south basin have sometimes turned a blue-green colour from the presence of algae.

Goldsborough said it will take decades to undo the damage accumulated over a century, adding it may take even longer if Manitoba continues to see massive flooding every few years.

After significant algae blooms on the lake in recent years, the Manitoba government has placed restrictions on hog farmers, in an effort to curb the introduction of waste into waterways that flow into the lake. Next year there will be a new ban on dishwasher detergents that contain phosphorus.

Winnipeg, about 60 kilometres south of the lake, also has been ordered to spend hundreds of millions of dollars to upgrade its waste-water treatment plants to curb the amount of nitrogen pouring into the lake.