- Associated Press - Sunday, August 10, 2014

TOLEDO, Ohio (AP) - Scientists and farmers agree that phosphorus from agriculture runoff is feeding the blue-green algae blooms on Lake Erie linked to a toxin found in the drinking water of 400,000 people in Ohio and southeastern Michigan last week.

Ohio’s political leaders are calling for more studies to find out why the blooms are increasing and how to control them. A number of environmental groups say it’s time for strict regulations on the agriculture industry.

But how much of a role do the farms play? Researchers already know some of the answers, yet there are still many unknowns.

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THE SOURCES

The debate over the algae blooms that produce the toxins found in Toledo’s water starts with what is causing them.

Scientists say climate change has brought on more heavy spring rains that are washing fertilizers off farm fields and lawns and causing sewer overflows in cities. All of those combine to dump more phosphorus in the rivers and streams that flow into the lake.

At the same time, scientists believe invasive zebra mussels in Lake Erie have disrupted the food chain so much that it has helped the algae flourish.

Then there is the question of where all the phosphorus is coming from. It’s found in farm fertilizers, livestock manure and raw sewage.

The Ohio Phosphorus Task Force - a group in Ohio representing the agriculture industry, environmental researchers and state regulators - concluded nearly two years ago that agriculture was the leading source of the phosphorus. Some researchers say it’s as much as two-thirds from agriculture.

That’s mainly because half the phosphorus in the lake comes down the Maumee River, which drains 3 million acres of farmland before flowing through Toledo and into the lake - not far from where last week’s algae bloom overwhelmed Toledo’s water intake.

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THE UNKNOWNS

While it’s now widely accepted that much of the phosphorus is coming from farmland, what’s much more difficult to pin down is exactly where and why.

There’s an assumption that farmers are simply overfertilizing their fields. Soil tests have shown that about 30 percent of fields have more phosphorus than they need. Cutting down on fertilizing that land would help with the problem.

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