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The algae bloom in Lake Erie in 2011, triggered by agricultural practices and warm temperatures, could become a regular occurrence, U.S. scientists warn.

A study published Monday in the National Academy of Sciences said that the 2011 record-breaking algal bloom in Lake Erie was triggered by long-term agricultural practices and extreme precipitation, followed by weak lake circulation and warm temperatures.

The research team, led by Carnegie Institution for Science at Stanford University Anna Michalak, also foresees that, unless agricultural practices change, the lake will continue to experience extreme blooms. The bloom covered an area 2.5 times larger than that of any Erie bloom on record.

"The perfect storm of weather events and agricultural practices that occurred in 2011 is unfortunately consistent with ongoing trends, which means that more huge algal blooms can be expected in the future unless a scientifically guided management plan is implemented for the region," said Michalak.

Using computer models, the researchers predict that climate change will accelerate these trends. They say different agricultural regulations are needed to prevent more mega-blooms, which are toxic and suck oxygen from the water.

The researchers also determined that certain strains of blue-green algae are toxic, which makes these blooms dangerous to more than just lake-dwelling life. In the case of the 2011 bloom in Lake Erie, the blue-green algae composed most of the bloom, and concentrations of the toxic material reached 4,500 μg/L, which is 225 times greater than the maximum that the World Health Organization recommends for water that is safe enough for swimming and boating.

"We need management policies that are good for agriculture as well as the lake ecology," Michalak said. "It doesn't do anybody any good to have these nutrients flowing into the lake. It's money being wasted by the farmers, and you are essentially fertilizing the algae instead of fertilizing the crops."

Invasive zebra mussels and quagga mussels have added to Lake Erie's problems, as these organisms preferentially eat phytoplankton that live in the lake and that normally compete with cyanobacteria, Michalak added.