Lake Erie algal blooms 'seeded' internally by overwintering cells in lake-bottom sediments

November 21, 2018, University of Michigan
Credit: CC0 Public Domain

Western Lake Erie's annual summer algal blooms are triggered, at least in part, by cyanobacteria cells that survive the winter in lake-bottom sediments, then emerge in the spring to "seed" the next year's bloom, according to a research team led by University of Michigan scientists.

The findings advance scientists' understanding of the basic biology driving the annual summer blooms, which are both an unsightly nuisance and a potential public health hazard. In addition, the work identifies a mechanism to explain the rapid increase in Lake Erie bloom size and spatial extent in early summer.

"The study suggests that the initial buildup of blooms can happen at a much higher rate and over a larger spatial extent than would otherwise be possible, due to the broad presence of viable cells in sediments throughout the lake," said study lead author Christine Kitchens, a research technician at the Cooperative Institute for Great Lakes Research (CIGLR) at U-M.

"These overwintering cells can quickly be entrained within the —particularly after a storm event—and start actively growing."

The study is scheduled for publication Nov. 21 in the journal PLOS ONE. Kitchens conducted the work for her master's thesis at the School for Environment and Sustainability. The other authors are Thomas Johengen, associate director of CIGLR, and Timothy Davis, an associate professor at Bowling Green State University.

Western Lake Erie has long been plagued by harmful , or HABs, fueled largely by nutrients in agricultural runoff. The blooms are composed largely of Microcystis, a genus of colony-forming cyanobacteria that sometimes produce liver toxins called microcystins.

Lake Erie is a drinking water source for 11 million people. In 2014, a cyanobacteria bloom infiltrated the Toledo water intake, resulting in a two-day "do not drink" advisory for more than 400,000 people.

This year's bloom was relatively small and fell short of scientists' predictions. Johengen said scientists should consider incorporating the new information about overwintering Microcystis cells into the computer models used to make the annual bloom forecasts.

Previous studies of other temperate lakes around the world indicate that overwintering populations of Microcystis cells possess high survivability and can seed seasonal blooms. However, the exact contribution of cells in sediments has been less clear.

For Lake Erie, one 2009 study concluded that the Maumee and Sandusky rivers were a potential source of the Microcystis cells—known to scientists as "inocula" because they inoculate the —that initiate the summer cyanobacteria blooms. But other work suggests that river populations do not seed the Erie blooms.

The new U-M-led study is believed to be the first to assess both the abundance and viability of overwintering Microcystis cells from sediments in the Great Lakes.

The researchers collected sediment-core samples at 16 sites covering 145 square miles in the portion of western Lake Erie where harmful cyanobacteria blooms are most prevalent and persistent. The sampling was done over a two-year period in water depths ranging from 10 to 30 feet.

Back in the lab, genetic tests revealed both the total abundance of Microcystis cells and the fraction of those cells that were potentially toxic. Then experiments were conducted to assess the viability of overwintering Microcystis cells and to grow some of the cells in the lab.

While Microcystis cell concentrations declined significantly over the winter, the cells that survived remained viable—meaning they were capable of growing—the following spring. In addition, the growth experiments showed that potentially toxic Microcystis strains were successfully cultured at a slightly higher rate than nontoxic strains.

That result could help explain a previous observation by the National Oceanic and Atmospheric Administration's Lake Erie monitoring program: that the percentage of potentially toxic Microcystis cells is highest during the early stages of a and declines throughout the summer.

Johengen said it's not yet known whether overwintering Microcystis pick up vital nutrients from the sediments and use those nutrients to fuel their early season growth spurt. If that's happening, it could complicate efforts to curb Lake Erie blooms by reducing fertilizer runoff from croplands, he said.

Explore further: Smaller summer harmful algal bloom forecast for western Lake Erie

More information: PLOS ONE (2018). … journal.pone.0206821

Related Stories

Image: Algae bloom in Lake St. Clair

August 5, 2015

On July 28, 2015, the Operational Land Imager (OLI) on the Landsat 8 satellite captured images of algal blooms around the Great Lakes, visible as swirls of green in this image of Lake St. Clair and in western Lake Erie.

Underwater robot tracks toxic algae in Lake Erie

August 28, 2018

Microcystin is a nasty toxin that can cause skin reactions, stomach problems, and even liver damage. It's produced by a tiny blue-green alga (cyanobacteria) called Microcystis, which multiplies like crazy in warm, nutrient-rich ...

Recommended for you

Archaeologists discover Incan tomb in Peru

February 16, 2019

Peruvian archaeologists discovered an Incan tomb in the north of the country where an elite member of the pre-Columbian empire was buried, one of the investigators announced Friday.

What rising seas mean for local economies

February 15, 2019

Impacts from climate change are not always easy to see. But for many local businesses in coastal communities across the United States, the evidence is right outside their doors—or in their parking lots.

Where is the universe hiding its missing mass?

February 15, 2019

Astronomers have spent decades looking for something that sounds like it would be hard to miss: about a third of the "normal" matter in the Universe. New results from NASA's Chandra X-ray Observatory may have helped them ...

The friendly extortioner takes it all

February 15, 2019

Cooperating with other people makes many things easier. However, competition is also a characteristic aspect of our society. In their struggle for contracts and positions, people have to be more successful than their competitors ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.