Moving Goalposts: The Challenge of Lake Erie Algal Blooms: Part 2: What We Know We Don't Know
Part 2: What We Know We Don’t Know
For immediate release: July 17, 2017
Jessy J. Sielski, Deputy Public Information Officer, MDARD
In part two of this four-part blog series about the algal blooms in Lake Erie, the author discusses how some of yesterday’s solutions may actually be some of today’s problems, as well as the critical knowledge gap that needs to be filled. (Read Part 1 Here.)
This is where things start to get complicated. Let’s begin with phosphorus. Until recently, we thought it was simple. Phosphorus binds to soil. Therefore, farmers and researchers believed that if they could keep the soil from moving off the land and into the river systems, they could prevent the phosphorus from entering Lake Erie. As a result, farmers methodically adopted a number of best management practices to prevent soil erosion—including riparian buffers (barriers of vegetation around the farmland that retain soil and absorb phosphorus), no-till farming (planting crops without exposing the soil), and cover crops (broadly grown vegetation planted after harvest that stay on the field through the winter).
Problem solved, right? Yes and no. Despite considerable improvements in wastewater treatment and all the best management practices put into place by farmers—which led to a significant reduction of phosphorus entering Lake Erie—several other troublesome and ongoing issues proved to be too much to overcome that year, leading to Toledo Water Crisis of 2014. That year, the basin experienced one of the largest blooms in recent history, leaving nearly 500,000 residents without access to drinking water.
One of the reasons for this—in addition to an abnormal year of heavy rainfall—is a relatively recent phenomenon known as dissolved reactive phosphorus (DRP), also referred to as soluble reactive phosphorus. Unlike the phosphorus that scientists have come to know and love, DRP does not bind to soil, which makes it much more difficult to address—and to contain.
Where did DRP come from and what is causing it? Well, no one is absolutely sure, but there are some credible theories based on emerging research. As Joe Kelpinski, manager of the Michigan Agriculture Environmental Assurance Program, a voluntary program for Michigan farmers explains, “Most of us believe that the problem of dissolved reactive phosphorus is linked to many factors, not just one. DRP could have always been here, but just as a very small percentage of overall phosphorus, so it went unnoticed. As to what is causing this problem, that’s what we’re trying to figure out. It’s likely that there are a number of different factors. We need to confirm what those factors are and to what degree they’re impacting the problem, and then figure out the best way to fix them.”
Some of the things enabling DRP, surprisingly, could actually be a result of previous state and federal conservation and environmental efforts. One possible contributor to the DRP problem could be connected to our rain becoming cleaner. Amendments to the Clean Air Act in 1990 were designed to address several problems, including acid rain.
The new standards worked well—but with some potentially unexpected effects.
“There is some concern about the pH level of rain having an overall effect on soil pH,” said Kelpinski. “The pH level of rain today is about one full point higher than it was in the mid-1990s. Rain has become so basic that it has actually changed the soil profile, and some believe that the changes in soil pH may have resulted in phosphorus becoming more soluble.”
Jim Johnson, director of MDARD’s Environmental Stewardship Division added, “There are some farmers who are applying soil additives to address soil pH, because they’re finding that the plant growth isn’t the same as it used to be.”
Another ongoing debate among key states and stakeholders focuses on dredging in Lake Erie. As the Ohio Environmental Protection Agency explains, “Each year, harbors on Ohio’s north shore must be dredged to keep the shipping channels open so commodities can move in and out of the ports. Nearly 1.5 million tons of material are dredged annually. Historically, much of the dredged material was dumped in the open waters of Lake Erie.”
The U.S. Army Corps of Engineers, the group responsible for the dredging, conducted a study surrounding this issue and ultimately claimed that “open-lake placement of dredged material does not contribute to the development of harmful algal blooms in the Western Basin of Lake Erie.” Ohio Governor John R. Kasich appeared to be less than convinced by this study, however, later announcing that he would allow the Ohio EPA to ban open lake dumping of contaminated dredged materials starting on July 1, 2020.
There is also reason to believe that long-term no-till farming—one of the best management practices designed to keep particulate phosphorus on the land—is actually contributing to the movement of DRP off farmland. As Johnson explains, “When you don’t churn the soil, the phosphorus could be confined to those top two to four inches. And what we know is when phosphorus saturation reaches a certain point, it cannot attach to the soil, and it moves freely through soil profile in a dissolved form, eventually reaching the tile drain lines. Leaving soil undisturbed beneath the surface removes a critical filtration process.
“No-till has its erosion benefits, but there are some risks,” Johnson continued. “A field demonstration from about 15 years ago involved blowing smoke into a tile line, and the end result was that you could actually see the smoke rise up through the ground, through worm holes, all along the tile lines. This demonstrated just how porous that soil was along those lines in a no-till operation. It could be flushing phosphorus through the soil profile. This is clearly one of those issues we need to better understand before we can confidently urge farmers to spend time, money and resources on implementing new practices.”
This is one reason why, as Kelpinski and Johnson explained, a key part of Michigan’s Domestic Action Plan for Lake Erie includes edge-of-field research that will take a close look at tile drainage and nutrient management.
“We know all about the buffers at the edge of fields, which address the movement of soil and water off the land, but DRP is a completely different situation,” added Johnson. “Everybody is trying to figure out the DRP issue. The question is, How do we find that see-saw balance to get the best of all worlds? We need to find ways to maintain the practices that keep phosphorus on the land without contributing to the movement of DRP.”
“The bottom line,” Johnson continued, “is that we just don’t have all the answers we need to make all the necessary changes. We know the what. We just don’t know the why. That’s why we’re doing things like the edge-of-field research. We need to understand exactly what factors help or prevent the movement of dissolved reactive phosphorus. We will get there, but it’s going to take some time.”
Another layer in the Lake Erie plot is invasive species. As Kelpinski explained, “After the Clean Water Act of the early 1970s, things were chugging along. The water was getting healthy, and the blooms died down. Then, in the 1990s, Lake Erie started to get invasive species. Zebra mussels and quagga mussels actually eat the algae that they like, and selectively filter out the algae they don’t like—one of which turns out to be the cyanobacteria that causes the harmful algal blooms. What happens is that the water starts to clear up, but that allows sunlight to penetrate even deeper, which of course helps the remaining algae grow. So, all of a sudden back in the late 90s, we started to see the algal blooms again.”
And last but certainly not least, to help complete the entire picture of the Lake Erie algal blooms, much work remains to be done to understand legacy phosphorus. In short, legacy phosphorus is all the phosphorus that has built up over many years and currently remains suspended in the sediments of streams, rivers and lakes—including Lake Erie.
“There is some debate about this too,” said Kelpinski, “but theoretically, if agricultural activity in the Western Basin stopped completely, it’s possible that it could still take years for the algal blooms to stop, simply because of the phosphorus that remains in the streams, rivers and lakes. As we saw in 2014, all it takes is one summer of heavy rain to flush a bunch of legacy phosphorus into the lake.”
Andrew Sharpley, PhD, a professor at the University of Arkansas and Co-Chair Environmental Task Force and Co-Director Discovery Farms for Arkansas Program, has studied soil science and phosphorus for more than 40 years. One study he conducted, in part, looked at standing bodies of water (lakes, reservoirs, etc.) and their ability to trap sediments like phosphorus. As he explains, “the relationship between [phosphorus] concentration and flow has changed markedly during several decades, such that [phosphorus] concentrations in reservoir discharges…are currently two- to threefold higher than those that occurred in the past at similar flow rates.”
He then goes on to explain how one severe weather event can have a massive impact on phosphorus loading into a waterway. “Tropical Storm Lee in 2011…accounted for 61% of the annual [phosphorus] flux in 2011 and 22% of the [phosphorus] flux during the past decade [out of the Susquehanna River].”
So, there are many unknowns about how much legacy phosphorus currently exists at the bottom of Lake Erie and the area around it, what role that has played in the recent blooms, what impact that will have on current efforts, and what—if anything—can be done to address it.