Toxic algae is wreaking havoc in northern Ohio, but it's not doing it alone.
A toxic bloom in Lake Erie — which forced the city of Toledo to turn off its tap water for two days this weekend — was exacerbated by another environmental calamity: hordes of invasive mussels that plague the Great Lakes ecosystem.
The mollusks, known as zebra and quagga mussels, arrived from Eastern Europe in the late 1980s by latching onto boats and have since spread throughout the Great Lakes.
And, in terms of water quality, the critters are a reverse filter: They remove sediment and food particles out of the water, sapping the resources native mussels and fish need.
But they leave the dangerous elements in place. The invaders are picky and don't absorb toxic forms of algae known as microcystis, leaving it to collect in the harmful blue-green algae blooms that collect on the surface.
"It's basically spitting the stuff out," explained Alan Steinman, director of the Annis Water Resources Institute at Michigan's Grand Valley State University. "Now the blue-greens in the water column have very few competitors "¦ and they bloom."
That's what's happening in Lake Erie, and this weekend, the trouble came to Toledo. More than 400,000 residents were without water until Monday morning after a toxin linked to an algal bloom was detected in an intake system. The ban was lifted on Monday, but the algae problem isn't going away — blooms will linger throughout the summer and have been steadily making a comeback in Lake Erie for years.
The mussels aren't the only factor behind the toxic algae. The blooms themselves are the result of an excess of phosphorous in the lake, due in large part to runoff of fertilizer from farms and other agricultural sources, as well as from septic systems and cities (the blooms grow especially quickly in shallow Lake Erie, especially on its western end). Excessive rain and storms linked to climate change have also been fingered as culprits in the recent rise in algae blooms, which were prevalent in the 1960s and '70s until the Clean Water Act forced the cleanup of some pollution sources.
But the presence of the mussels exacerbates the other factors, said Marc Smith, policy director for the National Wildlife Federation's Great Lakes office.
"While all this nutrient runoff is happening, the mussels really stir things up and double down the problem," Smith said. "There's no easy answer to this."
The National Oceanic and Atmospheric Administration has predicted that Lake Erie will experience a "significant" bloom this year, although it will be smaller than one that cropped up in 2013 and a record-setting bloom in 2011 that covered 1,900 square miles of the lake.
The thick green cyanobacteria won't just pose a danger to water supply; the blooms also block out light and can kill off plant and animal life in the lake.
They come at a time when the invasion of mussels is stirring up trouble in the Great Lakes — and it's spreading fast. They've been detected as far away as California and Texas and it's estimated that there are more than 950 trillion (with a "t") in Lake Michigan alone. It's a concentration so high that videos have shown them stacked as much as 5 feet high.
That has the potential to upend the ecosystem by robbing fish of the nutrients they need, soaking up plankton and tiny plants before they can reach the native species. Ironically that's left lakes clearer, but has also contributed to a die-off of fish and species up the food chain. A 2011 NWF report that looked at the "boom and bust" of the Great Lakes ecosystem found that 95 percent of the biomass of prey fish in Lake Huron had dropped 95 percent in 15 years, which in turn left bigger fish like salmon with little to eat. In Lake Michigan, the population of the tiny shrimp at the bottom of the food chain had dropped 94 percent in a decade.
And the mussels can also gather and clog up the intake tanks for water systems and industrial sites, which has caused hundreds of millions of dollars in damage in the Great Lakes region. A recent series in the Milwaukee Journal-Sentinel looked at the impact of invasive species across the Great Lakes.
With no natural predators or known way to eradicate the mussels, much of the response has been focused on simply stopping the mussels from spreading any further. The Environmental Protection Agency has advised boaters travelling in waters that may have been affected to be aware of any mussels latching on and using a heated spray to ward them off.
Scientists haven't yet found a way to eradicate the mussels without impacting the broader food system, and their vast reach makes a targeted approach difficult.
Even solving the mussel problem isn't likely to fix the rise of algae blooms, given the myriad factors that have contributed to their growth. Environmentalists have long sought more control over agricultural runoff to reduce the amount of phosphorous seeping into freshwater bodies, a call that's been renewed in the days after the Toledo incident.
And President Obama last month signed the Harmful Algal Blooms and Hypoxia Research and Control Amendments Act, which authorized $20.5 million to NOAA from 2014 to 2018 to study harmful blooms and look at solutions in freshwater.
Smith said the eventual solution would have to be a comprehensive effort that considered all of the causes, which in turn could clean up a number of water problems.
"To address invasive species without considering farmland or water quality won't work. We know everything has to be taken into account together," he said. "There's a lot of money out there that could be utilized, but it has to be strategic and not just random acts of conservation."