Lake continues trend of harmful and unsightly effect of nutrient pollution.
By Codi Kozacek
Circle of Blue
Water plant managers and city officials in Ohio and Ontario are bracing for an above-average toxic bloom of algae that is forecast to spread across Lake Erie later this summer. The 2014 algae bloom is anticipated to be the second or third largest in more than a decade, according to models by scientists at the National Oceanic and Atmospheric Administration and the University of Toledo.
The forecast measures the expected weight of the algae mass. The estimate of 22,000 metric dry tons (MT) is above the 10-year average of 14,000 MT. Uncertainties in the forecast mean the bloom will most likely be between 11,000 MT and 33,000 MT.
Blooms of toxin-releasing algae — a persistent problem in the 1960s that disappeared in the late 1980s following state and federal efforts to clean up nutrient pollution — have again become an annual occurrence on Lake Erie. The blooms turn the lake water pea green, release toxins harmful to humans and aquatic life, and can produce “dead zones” when they die and decompose, using up oxygen in the cold bottom layer of water.
In 2011, the Lake Erie algae bloom covered 5,000 square kilometers (1,930 square miles), a record. Last year the Carroll Water and Sewer District, near Toledo, shut down its drinking water treatment plant because of dangerous levels of algae-related toxins in water drawn from Lake Erie. Algae blooms also are growing thicker and more expansive along the shores of Lake Michigan in northern Michigan and northern Wisconsin.
The primary driver behind the blooms is phosphorus, a nutrient found in fertilizer, sewage, and industrial wastewater. The most problematic source of phosphorus in Lake Erie is runoff from agricultural fields, carried to the lake during large storm events that are expected to become more common with climate change, researchers have found. The relatively wet spring this year carried about the same amount of phosphorus into the lake as last year—slightly more than 1,000 metric tons, according to data compiled by the National Center for Water Quality Research at Heidelberg University in Ohio.
“To me, the data suggest that the bloom this year will probably be above average for the last 13 years, but similar to 2008-2010,” Laura Johnson, a research scientist at Heidelberg, told Circle of Blue. “Yet, we still don’t completely understand why 2013 was so high when [phosphorus] loading was similar to 2003. I don’t expect a year as bad as 2011, and it will definitely be worse than 2012.”
Winds, currents and temperature also play a role in the size of the bloom, which typically appears in late summer and early fall. Last year, the bloom’s most potent effects were felt in September, when high toxin levels forced an Ohio drinking water plant to shut down for the first time in history.
Conditions Clear So Far
So far, there are no blooms on the lake, though water temperatures are relatively warm.
“The water by the islands and east is very clear,” Justin Chaffin, a senior researcher at Ohio State University’s Stone Laboratory, told Circle of Blue. “I have never seen water this clear on Erie before.”
Chaffin added that a quick warm up after the cold, icy winter could have implications for the lake’s seasonal dead zone, which is created when lake organisms use up the oxygen trapped in the cold, bottom layer of the lake before supplies get replenished in the winter.
“We went from winter to summer in about a month,” he said. “This quick warm up led to a very thick hypolimnion [deep water layer] in the central basin. Oxygen profiles looked more like a deeper lake with more oxygen in the bottom waters than top waters. The thick hypolimnion might mean that the dead zone might be smaller this summer or delayed in its appearance. There was a lot more oxygen to begin with when the lake stratified [separated into cold and warm layers].”
State and Federal Efforts Take Aim at Algal Blooms
Algal blooms and dead zones are a persistent problem not only in Lake Erie and the Great Lakes, but also in other economically important marine environments in the United States. The annual dead zone in the Gulf of Mexico, for example, is expected to reach 14,000 square kilometers (5,400 square miles) this year — near its average. The dead zone in the Chesapeake Bay is predicted to occupy 8.2 cubic kilometers, which is slightly above average. The Chesapeake dead zone is measured in volume rather than surface area because the bay is so shallow. These areas can also suffer from toxic algal blooms, though the species of algae differ from those found in Lake Erie.
In response to the problem, President Obama in late June signed a bill to spend $US 82 million on algal bloom research through the Harmful Algal Blooms and Hypoxia Research Act. The law was originally created after an outbreak of toxic algae in Chesapeake Bay tributaries, which caused a major public health scare and devastated the bay’s seafood industry for several months in 1997. The law seeks to uncover the mechanisms behind algal blooms and dead zones, but it does not pursue any regulatory action for nutrient pollution.
Ohio took a step toward nutrient regulation this spring by passing a bill that creates a fertilizer certification program for farmers and requires farmers planting more than 50 acres to be certified by the state. The law, which goes into effect in 2017, does not limit how much fertilizer farmers can use and does not include the application of manure.