The harmful algal blooms that manifest on Lake Erie in the summer can be as murky a concept to understand as they look.
But it’s important to recognize the distinct and sometimes dangerous impact these blooms can have beyond the Great Lakes’ banks: Harmful algal blooms are capable of producing toxins that can cause skin rashes, GI problems and varying degrees of damage to a person’s liver, kidneys and nervous system.
Perhaps the most infamous instance of the excessive growth of microscopic algae organisms, commonly known as blooms, resulted in a three-day shutdown of the city of Toledo’s water supply in 2014.
We asked Ohio State’s own bloom experts — Ohio Sea Grant Director Christopher Winslow and Jay Martin, professor in the Department of Food, Agricultural and Biological Engineering and also with Ohio Sea Grant — about the perennial problem of blooms, their hazards and what’s being done about them.
Harmful algal blooms are caused by increases of phosphorus in the lake.
While septic tanks, lawns, golf courses and wastewater treatment plants also contribute phosphorous to runoff that ends up in Lake Erie, about 85% of the phosphorus comes from agriculture.
Heavy spring rains lead to greater runoff of phosphorus from farm fields. The Maumee River runs through extensively farmed agriculture land as it winds through eastern Indiana and western Ohio and then feeds into Lake Erie near Toledo.
The goal going forward is to reduce nutrient inputs under heavy spring rain conditions and other movement of water over the landscape.
Blooms are running big.
Bloom events are likely to be at their greatest in August and September and are usually finished by mid-October. Onset could be as early as late June and early July; peak blooms manifest later.
On a scale of 1 to 10, scientists predict this year’s bloom to be a 3. This is similar to last year’s bloom and that in 2016 and slightly smaller than 2018.
Where a bloom settles or moves from day to day is determined by wind conditions (direction and speed). Additionally, if surface water is calm, the bloom may collect at the surface, concentrating toxins and amplifying the green color. During heavy storms, strong winds can mix up the water and the algae along with it. Communities from Sandusky, Ohio, and westward are at a higher risk because of the more shallow water in that part of the lake and the fact that the primary origin of the bloom is Maumee Bay.
Human and animal health are threatened.
Harmful algal blooms are a known liver toxin and can negatively affect the nervous system. Skin irritations are also a concern.
County health departments post advisories regarding when it is unsafe to be in or on the lake or to eat non-commercially caught fish from the lake.
The same health concerns exist for pets, which can’t control their water intake as well as people.
Blooms are costly.
It doesn’t take an economist to know that slime of any color keeps people away from the lake.
Ohio State researchers estimated blooms at two Ohio lakes cost homeowners $152 million in lost property value over six years. And a study commissioned by the International Joint Commission estimated that harmful algal blooms in Lake Erie in 2014 resulted in $43 million in lost tourism and recreation dollars.
Communities along the lake are spending millions more for water treatment, as well.
Scientists are tracking the blooms and working with agriculture experts to address causes.
The key is to reduce the amount of phosphorus and nitrogen that get into the lake. Both play a role in this excess growth, but nitrogen fuels how toxic the bloom might get.
Ohio law now prohibits farmers from spreading fertilizer on frozen ground, and Ohio State researchers are encouraging farmers to insert fertilizer into their fields rather than spread it across the surface. The result is less phosphorus in the runoff.
Already since 2014, the amount of farmland being treated with subsurface placement of fertilizer has increased from 33 to 39%. Additionally, the percentage of acres planted with cover crops when the fields would otherwise be empty has increased from 17 to 27%. Farmers also are being encouraged to plant buffer strips to further deter runoff.
Ohio, Michigan and Ontario have adopted a goal to reduce the amount of phosphorus entering Lake Erie by 40% by 2025.
These measures are not without cost. To aid farmers, Gov. Mike DeWines’s H2Ohion Initiative is incentivized to implement proven, cost-effective best management practices. These include soil testing, variable application rate of fertilization, manure incorporation and conservation crop rotation.
How close are we to the 40% reduction?
This is not easy to assess.
Many of the practices that need to be deployed on the landscape require funding and time. Some practices have a lag effect, meaning they do not draw down nutrients overnight.
Researchers also have learned that a portion of the Lake Erie nutrient inputs are coming from legacy fields, or fields that have elevated nutrient levels because of past applications, not application of fertilizers in a given year. These nutrient sources are often more difficult to address and can mask the effects of present-day conservation efforts.
Finally, annual variability in runoff, number and size of rain events also can mask the effects of present-day conservation efforts.
Ohio Sea Grant, in partnership with the University of Toledo, are coordinating $14 million in research funding from the Ohio Department of Higher Education. These funds, since 2015, have supported researchers from institutions from across the state to answer questions related to producing safe drinking water, assessing the risks that algal toxins present for human health, identifying how blooms behave and addressing nutrient runoff.
When those research projects are finished, Ohio Sea Grant and the University of Toledo are working to convey findings to farmers, water treatment facilities, municipalities, lake residents and the state agencies charged with addressing this issue.