Tackling Lake Erie’s algal blooms requires targeted conservation strategies

A satellite image of an algae bloom in Lake Erie in September 2017.

Excess nutrients, especially phosphorus and nitrogen, can increase harmful algal blooms. (Earth Resources Observation and Science Center) Anyone living along the coast of Lake Erie will be well aware of the periodic algal blooms that appear on its surface.

The greenish blooms can cause rashes and other health problems and pose risks to both humans and animals.

In 2016, Canada and the United States agreed to reduce the amount of phosphorus entering Lake Erie’s western and central basins by 40 per cent of 2008 levels.

Yet recent reporting shows that this target remains largely unmet .

Excess nutrients, especially phosphorus and nitrogen, can increase harmful algal blooms in lakes.

These blooms deplete oxygen levels in the water, threatening drinking water, fisheries and communities that rely on tourism.

Algal blooms in Lake Erie also remind us how closely food production and clean water are connected.

Many of these nutrients come from nearby farms, and the challenge is keeping them out of waterways.

Agricultural water pollution is not like pollution from a single pipe: it comes from many fields and moves through different pathways.

Some of these excess nutrients come from nearby farm fields.

They travel overland during storms or in snowmelt, or move underground through drain tiles — buried pipes that remove excess water from wet soil.

In 2025, we studied the area around Medway Creek, a tile-drained agricultural watershed in southwestern Ontario.

We observed the fields, terrain, soil, crop history and drainage information and used a mapping tool to identify potential locations for conservation practices.