Harmful algal bloom predicted on Lake Erie
While the western end of Lake Erie will always be hit hardest by harmful algal blooms, it doesn’t mean the eastern end is immune, says Brock University earth science professor Francine McCarthy.
“It could certainly happen here,” she says.
But, McCarthy says, the eastern basin of the lake is deeper and colder, giving it a layer of protection over the much shallower western basin. The eastern basin starts from the Long Point area, while the western basin stops in the Point Pelee area. The central basin of the lake is in between those two points.
“The western basin is very warm throughout the water column,” she says. “Warmth is one of the things that correlates with harmful algal blooms.”
The U.S. National Oceanic and Atmospheric Administration, and its partners, predicted a significant harmful algal bloom for the western end of Lake Erie this summer. The scientific agency, part of the U.S. Department of Commerce, says the 2017 bloom could reach levels last seen in 2013 and 2014, but smaller than the record bloom of 2015.
In a release, it says the bloom “is expected to measure 7.5 on the severity index, but could range between six and 9.5. An index above five indicates a potentially harmful bloom. The severity index is based on a bloom’s biomass — the amount of its harmful algae — over a sustained period. The largest blooms, 2011 and 2015, were 10 and 10.5, respectively.”
In 2014, Toldeo, Ohio, saw its municipal water supply shut down and a two-day ban on drinking or cooking with tap water due to an bloom in the western basin.
Algal blooms are caused by cyanobacteria, says McCarthy, adding it used to be called blue-green algae. The cyanobacteria creates microcystins, a neurotoxin that can affect everything living thing in the water and those that drink it.
She says the cyanobacteria are found across the lake, but it takes the right conditions — like warm waters and ample, available nutrients — to see them increase and cause a harmful bloom.
Nutrients that feed cyanobacteria include nitrogen and phosphorus found in agricultural fertilizer, and human activity such as effluent from wastewater treatment plants.
“Back in the ’80s and ’90s, people began to become aware and decreased the use of fertilizer. The Great Lakes Water Quality Agreement (between Canada and the U.S.) had an impact,” says McCarthy.
She says farmers on both sides of the border started to change the way the plowed their fields and applied fertilizer more judiciously, measures suggested by scientists to reduce phosphorus and other nutrients from entering the lake.
“Over time though, the population in the Great Lakes increased … the number of people that need to be fed.”
McCarthy says Ohio and Michigan are an agricultural heartland for the region, and even with best-use farming practices, there are factors beyond farmers’ control that will cause fertilizer to run off into the lake.
Weather events, such as large storms, erode fields no matter how well plowed.
“The warming we’ve experienced over the last several decades make more of these large storm events less rare.”
McCarthy says large rain events that take place during the spring months have a bigger impact, because that is time of year farmers are fertilizing their fields.
And with the amount of rivers, and tributaries that feed those rivers, on the U.S. side of the border the run-off from agricultural lands into the lake will continue to feed the cyanobacteria.
“We’ve taken steps as a society as much as we can, but still the odds are against us.”
Information on harmful algal blooms can be found at https:// oceanservice.noaa.gov/hazards/ hab and Lake Erie forecasts at https://tidesandcurrents.noaa. gov/hab/lakeerie.html. dajohnson@postmedia.com