密歇根新闻广播 关注伊利湖中的毒性爆发（在线收听）

There's a bloom of cyanobacteria in Lake Erie right now. Scientists with the National Oceanic and Atmospheric Administration are predicting it could become the second worst on record.

The bacteria produce a toxin called microcystin. A year ago, that toxin led to a ban on drinking water in Toledo and a few Michigan communities. Officials say microcystin can cause skin irritation and could affect the liver and nervous systems if you consume it in large amounts.

This week, Toledo officials said they detected low levels of microcystin in untreated water from Lake Erie. But they say right now, their treatment system is removing the toxin and city water is safe to drink.

Joel Mazur is the commissioner of field operations with the Toledo water department.

"We're light years ahead of where we were before in terms of water treatment," Mazur says.

He says they've stepped up monitoring and added more treatment steps to take out the toxin.

"We're able to detect the issues in the lake far sooner than we were before and treat it," he says.

This year's bloom

We took a boat ride with local officials, environmental groups and reporters to get a look at this year's bloom.

Sandy Bihn is with Lake Erie Waterkeeper. She holds up a glass of lake water with little green blobs floating in it.

"It's not nearly as dense as it was last year when we were out here, because the bloom has moved further east which is good for the Toledo intake," she says.

We're three miles away from shore when Joel Mazur points out Toledo's water intake crib. He says they put in an advanced warning system after last year's crisis. So now, there's a monitor in the intake crib.

"Now that we're detecting microcystin in the water, we have crews that actually come out now and they are taking samples and taking it to the lab so we can have daily monitoring of the levels of microcystin that are in the water today," Mazur says.

There's a water quality dashboard on the city's website. Right now, city water is at the "watch" level. That means they've detected microcystin in the lake but not in tap water.

Phosphorus in Lake Erie

In June, Governor Snyder joined Ohio Governor John Kasich and Ontario Premier Kathleen Wynne in a pledge to cut phosphorus into Lake Erie by 40 percent over the next 10 years.

Phosphorus gets into the lake from farm fertilizer, wastewater from cities, and leaking septic tanks along with other sources.

Sandy Bihn says we need better monitoring of all these sources.

"We know that ag is a huge contributor," she says. "I mean, we know what the categories are. We don't know the specific locations and amounts, that's what we're missing."

She says officials need to track exactly how much phosphorus is coming from each source.

Bill Myers agrees with her. He's the president of the Lucas County Farm Bureau.

"I'm tired of hearing hypotheticals on where things are coming from," he says. "We need to know for sure what areas are contributing and target the highest levels with the quickest response to get the hugest decrease as fast as we can."

This spring, Ohio enacted a law that bans farmers from spreading fertilizer on frozen or rain-soaked fields. It's intended to cut back on phosphorus that runs off those fields.

A cyanobacteria puzzle

Scientists are trying to solve a mystery about these toxic blooms.

Greg Dick is an associate professor of earth and environmental sciences at the University of Michigan.

"One of the really interesting findings so far has been that as we track these blooms through the season, the bloom develops and it progresses and it's toxic," Dick says. "But then towards the end of the summer we still have a really strong bloom with very dense cyanobacteria, but the toxicity of that bloom changes. And in particular the toxicity of the bloom drops off."

He says they could find some clues in the DNA of these bacteria. Some strains have the gene to produce the toxin and others don't. Dick says they're testing a hypothesis that nitrogen could affect how toxic the blooms become.