Lake Erie has been affected by hypoxia since the 1950s.
Areas of low oxygen are 30 times more prevalent in the nation’s waterways now than they were in 1960, according to a recent federal report.
And climate change means they’ll continue to worsen.
The report says that the low-oxygen condition known as hypoxia has been detected in half of the more than 600 national waterways analyzed by the National Oceanic Atmospheric Administration, the U.S. Geological Society, the Environmental Protection Agency and the U.S. Department of Agriculture.
Hypoxia is often caused by increased nutrients such as phosphorous and nitrogen. These common components of fertilizer often enter lakes and streams with runoff from farms and lawns.
Nitrogen released into the atmosphere from fossil fuel production can also settle onto the water’s surface.
“What we do affects the amount of nutrients that wash off the land and are ultimately carried by rivers to the coast,” said Herb Buxton, one of the authors of the report and the U.S. Geological Society’s Toxic Substances Hydrology Program Coordinator. “Runoff is the conveyer belt for moving nutrients from the landscape to our coastal systems.”
The nutrients cause algae to grow. When the algae dies, the bacteria that decompose the plants also consumes oxygen. The resulting low oxygen in the water will typically either kill the animals in the area or force them to move. The process is called eutrophication and the resulting low-oxygen regions are known as dead zones.
Hypoxia has been present across the U.S. for more than 50 years. The Chesapeake Bay is one of the first places it was recognized in the 1950s. Since then, it has been detected in the Gulf of Mexico, Lake Erie, Lake Michigan and off the coasts of Washington and Oregon. According to the report, low oxygen levels currently threaten at least 300 bodies of water.
Hypoxia has caused severe algae blooms and killing fish in China's Dianchi Lake.
Globally, hypoxia has increased 10-fold in the past 50 years, the report says.
In 1980, the condition affected only one of the Great Lakes — Lake Erie. Today it is present in Lake Erie and Lake Michigan.
“In the last ten years, it has been recognized that the Great Bay of Lake Michigan is experiencing low oxygen problems that correlate with temperature changes and runoff.” Jewett said.
Lake Erie has been affected by hypoxia since the 1950s. The lake receives the highest sediment loads out of all the Great Lakes, according to the report. The Maumee River in northwestern Ohio is the lake’s main source of nutrient sediment.
This video shows the movement of sediment in Lake Erie throughout last March.
According to the EPA, source control and limiting the use of phosphorus in the 1970s helped to practically eliminate hypoxia from Lake Erie by the mid-1980s. However, it has been progressively increasing again for the past 20 years.
The growth of hypoxia in the Great Lakes over the past few decades has been small compared to many other regions. The report notes that most of the changes in hypoxia levels have been in the North Atlantic, South Atlantic and Pacific.
But global warming caused by burning fossil fuels will make things worse, researchers say.
“There is a lot to be figured out about the interaction between climate and hypoxia,” said Libby Jewett, an author of the repor