Every summer, the surface of Lake Erie tells a story.
In some places, it’s calm and blue. In others, it turns a murky green—thick with algae that can threaten drinking water, wildlife, and recreation.
These events, known as harmful algal blooms (HABs), have become one of the lake’s most serious and visible challenges. But what’s really behind them—and what can be done to stop them?
The Root Cause: Too Much Phosphorus
Harmful algal blooms feed on phosphorus, a nutrient commonly found in agricultural fertilizers and animal manure. When heavy rains wash excess phosphorus off farm fields, it flows into streams, rivers, and eventually, Lake Erie.
Once in the water, that phosphorus becomes food for cyanobacteria—often called “blue-green algae”—which can multiply rapidly under warm, sunny conditions. The result? Massive blooms that deplete oxygen, harm fish, and sometimes release toxins that threaten public health.
Why It’s Getting Worse
While phosphorus runoff isn’t new, a combination of modern factors has intensified the problem:
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Changing weather patterns — Heavier spring rains and warmer summers create ideal conditions for blooms.
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Tile drainage systems — Designed to improve crop yields, these systems can carry dissolved nutrients straight to waterways.
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Legacy phosphorus — Nutrients that built up in soils and sediments over decades continue to leach into the lake even as new applications decrease.
Despite significant progress by farmers and conservation programs, including H2Ohio, the lake still receives more phosphorus than it can handle.
What’s Being Done
Across Ohio, scientists, policymakers, and organizations like the Lake Erie Foundation are working on multiple fronts:
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Supporting research projects that test innovative solutions like phosphorus filters to trap nutrients before they enter waterways.
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Advocating for funding and policies that protect wetlands and improve nutrient management.
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Partnering with farmers, cities, and industries to encourage sustainable practices that balance productivity with environmental protection.
Progress is happening—but it takes all of us to make a lasting difference.
How You Can Help
You don’t have to live on a farm or near the lake to make an impact:
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Use phosphorus-free lawn fertilizers.
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Reduce single-use plastics and properly dispose of household waste to prevent runoff pollution.
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Support conservation funding like H2Ohio and groups such as the Lake Erie Foundation that fight for science-based solutions.
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Spread awareness—talk with friends and neighbors about why a healthy Lake Erie matters.
Lake Erie Needs All of Us
Lake Erie provides drinking water for millions of people, supports vibrant communities, and fuels Ohio’s economy. Harmful algal blooms are a reminder of how interconnected we are with our environment—and how our collective choices can protect it.
Join the Lake Erie Foundation in our mission to restore and protect this vital resource for generations to come.