By Matt Reese
Ohio is unbelievably fortunate to have Lake Erie, the richest, most productive and most biologically diverse of the Great Lakes.
“Lake Erie is one of the most important lakes in the world,” said Jeff Reutter, director of Ohio Sea Grant and Stone Laboratory on Lake Erie. “Lake Erie produces more fish for human consumption than the other four Great Lakes combined.”
Lake Superior has around 50% of the water and 2% of the fish of all the Great Lakes, while Lake Erie has 2% of the water and 50% of the fish. Reutter also pointed out that Lake Erie supplies drinking water for 11 million people, has more than 20 power plants, and a $1 billion sport fishery. In addition, Lake Erie is the shallowest and warmest of the Great Lakes, and the watershed is dominated by cities and agriculture, so it gets more sediment, more fertilizer and sewage and more pesticides.
“There are huge sediment loads coming into the Western Basin of Lake Erie from the Maumee and Sandusky rivers,” he said.
The Maumee River alone brings more sediment into Lake Erie than all of the tributaries draining into Lake Superior, and Lake Superior holds 20 times the volume of water. Sediment from the Maumee Watershed has been found beyond Niagara Falls.
This sediment is costly when it leaves farms and costly again when it reaches Lake Erie. In 2010, 1.9 million cubic yards of sediment needed to be dredged from the Port of Toledo to accommodate shipping traffic.
“The harbors must be dredged to 28 feet,” Reutter said. “All of this dredged material is loaded onto a barge and dumped back into the Western Basin.”
Leading up to 1970, Lake Erie was showing very clear signs that water quality was deteriorating. When the Cuyahoga River caught fire in 1969 and photos were featured in Time Magazine, the public took notice.
“The pollution problems were severe and those photos in Time really shifted the environmental awareness,” Reutter said.
The ecology that makes Lake Erie so valuable is also its curse. The Lake is divided into three distinct basins. The Western Basin is very shallow and gets the most sediment and nutrient influx from the rich agricultural lands surrounding the Maumee and Sandusky Rivers. Lake Erie is also the warmest of the Great Lakes due to its shallow depth and southern location.
When the warm water and the necessary nutrients mix, it can result in the unwanted growth of harmful algal blooms. In the 1960s, it was common to see the green sheen of slime coating much of the surface of the Western Basin with these harmful algal blooms. The algae then floated out into the deeper Central Basin of the Lake, died in the cooler water, sunk to the bottom and decomposed. The decomposition pulled oxygen from the water and created a large dead zone. The Eastern Basin, which starts around the Ohio/Pennsylvania line, is much deeper and colder than the other two, making it largely immune from the most severe problems.
Reutter and his colleagues at the Stone Lab began working on solutions to the growing problem and found that they should target phosphorus (P) in the late 1960s.
“P is the most common limiting nutrient in fresh water. In salt water it is nitrogen,” Reutter said. “When you have a harmful algal bloom, it will continue until the essential nutrient in the shortest supply is gone. In fresh water, most of the time it is P. By reducing the P, you can most easily stop the bad algae growth in Lake Erie.”
With this in mind, they started the daunting task of cleaning up Lake Erie.
“In 1969, we started working to reduce the phosphorus loads from point sources. Our goal was to reduce the P from 29,000 metric tons to 11,000. I was a young guy back then and I thought it was impossible, but we did it and the Lake responded. From 1970 to 1975, water quality stabilized and then steadily improved until 1995. By 1990, we were right about at the goal,” he said. “From the 70s to the 90s we focused almost entirely on point sources and improving sewage treatment in the big cities. Agriculture was contributing back then, but not as much as the point sources.”
In 20 years, Lake Erie went from the “dead lake” that produced an annual harvest of 112,000 walleye to the Walleye Capital of the World producing a harvest of over 5 million walleye a year. As clear as the evidence had been of the deteriorating water quality before 1970, improvements from 1975 to 1995 were equally clear. The P reduction efforts were a dramatic success.
“It was the best example of ecosystem recovery in the world,” Reutter said. “We accomplished that by significantly reducing P loading.”
But the story does not end there. The dissolved reactive P concentration in Lake Erie that had been declining sharply since the 1970s began steadily rising in the mid-1990s. The harmful algae followed. In 2010, around two-thirds of the Western Basin was covered with harmful algal blooms.
With a billion-dollar fishing industry, drinking water for millions and the tremendous environmental implications, people are once again taking notice. Last May, the Ohio Lake Erie Phosphorus Task Force released its findings that included a renewed focus on agricultural sources of P, particularly in the Maumee and Sandusky tributaries. The report press released from the Ohio EPA, stated: “There are multiple sources of phosphorus loading; however, the most significant is runoff from agricultural nutrient applications such as commercial fertilizers and livestock manure. The task force’s primary concern was dissolved reactive phosphorus (DRP), a form of phosphorus in solution that does not attach to sediment. DRP, also called soluble phosphorus, is more readily available for uptake by both crops and algae than particulate phosphorus attached to soil and sediment. Both manure and commercial fertilizer have relatively high concentrations of soluble, or dissolved reactive phosphorus, which is why it was the task force’s primary concern.”
While agriculture is certainly not the only source of excess P in Lake Erie, the industry will have to be a major part of the solution.
“It appears that agriculture is going to need to reduce the amount of P going into the Lake by 50% to 75%, a 10% reduction is not going to do it,” Reutter said. “Ohio agriculture needs to start looking for the low hanging fruit. It would be smart for agriculture to be proactive on this.”
Buffer strips, nutrient incorporation, careful timing of nutrient application, manure tests and application based on P, reduced tillage, increased soil testing, and other practices could all play a role. Ignoring the problem, though, is not an option.
“We can’t do nothing. There are 11 million people using for drinking water. It is a human health issue and we cannot allow the problem to continue, but as a society, we do not want to reduce our ability to produce food either,” he said. “How do we do both? This is a national problem. Can we achieve these goals simply by using best management practices or do we need regulations?”
Of course, this problem is not limited to Lake Erie or to Ohio. Due to the unprecedented harmful algal blooms in 2009 and 2010, the Grand Lake St. Marys watershed was designated a watershed in distress last month by Ohio Department of Natural Resources. Other smaller lakes are seeing problems as well.
The warm weather, more severe storm events, nutrient levels, invasive species, sediment and harmful algal blooms are all interconnected in Lake Erie and other bodies of water, Reutter said. Of all of these factors, P is still the easiest to control.
“Forty years ago I started out my career with Lake Erie and now we are right back where we started. But now we know that if we control the P, we can control the problem,” he said. “There is so much notoriety about it and people are looking for these harmful algal blooms. This problem is not going away and it is getting worse. How will agriculture respond?”