Agriculture major contributor to Lake Erie algae blooms

Better on-farm management would go a long ways towards solving the problem

A toxic algae bloom in Lake Erie viewed by satellite in 2014.

There are two easily identifiable solutions to the Lake Erie algae blooms, said an American researcher, but success will require the co-operation of thousands of farmers.

Jeffrey Reutter, a researcher at the Lake Erie island-based Ohio State University Stone Lab research station, has seen both the 1970s sewage-driven algae bloom, and the current blooms that are driven by excess phosphorus from agricultural run-off.

“I honestly think we could solve the problem if everyone soil tested and did not apply more phosphorus than is needed,” he said at the Innovative Farmers Association of Ontario annual conference recently in London, Ont. The second practice is incorporating the fertilizer when it is spread.

“If we can do that the problem will go away,” he said.

There’s up to 60 per cent reduction in phosphorus loss when the fertilizer is incorporated, he said.

After a long presentation on the extent of the challenge of algae blooms and their causes, Reutter made his statement about the simplicity of the solution in an answer to a question about farm production practices with the most impact.

The solutions would, in fact, be profitable for farmers. Applying less fertilizer would save on costs, and incorporating the phosphorus would make more efficient use of the resource.

The reality is that among thousands of farms, there are many different production practices that have made sense for generations, and applying more fertilizer than needed makes sure that there’s always enough. More precise application would require investment in equipment and regular testing, which not all farms are able to do.

Reutter said about 30 per cent of farmers are already using production practices that reduce phosphorus. Another 30 per cent will likely move to those practices. The question is how to convince the other 40 per cent. Research shows that 42 per cent of acres are responsible for 78 per cent of phosphorus and sediment loss.

“It’s probably not going to happen only voluntarily,” he said.

Sewage in the ’70s

The 1970s algae blooms were mostly due to the almost complete lack of sewage treatment by U.S. cities along the lake. That was fairly easily solved with more regulation and the imposition of standards. The lake rejuvenated.

Reutter calls the 1970s cleanup “the greatest example of ecosystem recovery in the world.”

Fish returned, as did fisheries and tourism.

However, by the late 1990s, the re-eutrophication of Lake Erie had begun, as more phosphorus from various sources, including agriculture, made their way to the lake. By 2014, the problem was acute enough that Toledo, a city the size of London, Ont., had to stop drawing municipal drinking water from the lake due to toxins created by algae blooms.

Of the five Great Lakes, Erie is the only one with serious pollution issues. That’s because it’s by far the shallowest. The deepest point in the lake is 64 metres deep, whereas Lake Superior reaches depths of 405 metres. In the western basin of Lake Erie, it is only 7.5 metres deep.

However, the water does change over rapidly in the lake due to the large flow in from the Detroit River and out through the Niagara River. That means that when changes are made, improvements occur relatively quickly.

Reutter said there is not much doubt that agriculture is a major contributor to the phosphorus problems in Lake Erie. There are very precise and regular measurements taken of rivers such as the Maumee River in Ohio. Similar measurements will be in place on the Thames River in Ontario by this summer. The major algae blooms are highly correlated with heavy rainfall years, when more phosphorus is washed into water courses that run to the lake. Storm activity has also increased in ferocity, which means more nutrients washing to the lake. Annual storm discharge into the lake is up 53 per cent since 1960, said Reutter.

The use of more bioavailable phosphorus sources for fertilizer has also meant greater movement of that phosphorus, said Reutter.

Canadian farmers have a role, but Reutter said the problem is largely one for Americans to solve, as their rivers are contributing significantly more to the problem than those in Canada. For example, the Maumee River in Ohio contributes between five to 10 times more phosphorus to the lake than the Thames River, which is the largest Canadian source.

“The vast majority of this phosphorus is coming from the U.S., not the Canadian side,” he said.

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