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Lake Erie's toxic algae bloom is back and it's spreading

Western Lake Erie Basin's developing algal bloom, on July 28, 2015. Credit: NASA Earth Observatory

Scott Sutherland
Meteorologist/Science Writer

Thursday, August 6, 2015, 1:44 PM - Lake Erie's toxic algal bloom, predicted to rival the record-setting bloom seen in 2011, has now formed and is spreading through the western end of the lake, and even up into Lake St. Clair.

Each summer, Lake Erie goes through a sudden and dramatic shift in colour, as the normal deep blue of the water becomes mixed with the swirls and swaths of vibrant green from algal blooms that spread throughout the shallower regions of the lake.

On July 28, 2015, NASA's Landsat-8 satellite captured the images below, of the western tip of Lake Erie and Lake St. Clair, showing this vibrant green spreading through the water.

Satellite view of western Lake Erie's algal bloom, July 28, 2015. Credit: NASA/Landsat-8

Satellite view of Lake St. Clair's algal bloom, July 28, 2015. Credit: NASA/Landsat-8

The animation below, captured by NASA's Terra and Aqua satellites, from July 22 to August 5, show the blooms developing and spreading.

This vibrant green colour comes from a population explosion of algae - known as cyanobacteria - which is touched off by a combination of warm waters, sunshine and an abundant supply of nutrients thanks to phosphorus from commercial agricultural runoff, sewage and industry that gets washed into the lake water.

Cyanobacteria is naturally occurring in the environment, and uses photosynthesis to consume carbon dioxide and phosphorus in the water, and produces oxygen as a waste product. It's thought that these bacteria were the first to introduce oxygen into ancient Earth's atmosphere.

In past, populations were kept more under control by the natural processes in the lake. In more recent years - mainly in the 1950s and 1960s and again roughly in the past decade - higher concentrations of phosphorus entering the lake water have caused more of these population explosions.

Normally fairly harmless in lower concentrations, when these harmful algal blooms (HABs) occur, cyanobacteria pose a risk to aquatic life and human health.

As a bloom spreads throughout the surface layer of lake water, the cyanobacteria release toxins known as microcystins into the environment. Simply swimming in water with high concentrations of microcystins can cause symptoms such as stomach cramps, vomiting, diarrhea, fever, headache, muscle and joint pain, and weakness, as well as skin and eye irritation, sore throat and allergic reactions. If these toxins enter the drinking water supply in sufficient amounts, such as during extreme outbreaks, symptoms can develop that cause liver and kidney damage, or life-threatening bouts of gastroenteritis, aka "stomach flu" (especially for children and the elderly).

Projected HABs bloom range for 2015.
Credit: NOAA

Coupled with these toxins, further problems occur due to the life cycle of the cyanobacteria. Since individual bacteria only live for a very short time, even as the bloom spreads, millions of them die in the process. The death and decay of the bacteria strips oxygen from the water (hypoxia), and the dead organisms form a layer of scum on the surface. Thus, the living bacteria in the top layer of the water absorbs sunlight for photosynthesis while at the same time more sunlight is blocked from reaching deeper waters by this scum on the surface. This combination kills off important plant and microorganism species that live deeper down, and as well as any organisms that depend upon them, worsening the hypoxia in the lake water. Some regions of the lake can become "dead zones," with massive fish die-offs ("fish kills") that can make the situation worse.

Second worst in history?

According to the National Oceanic and Atmospheric Administration (NOAA), this year's Lake Erie algal bloom could reach severe levels, and could become the second worst bloom on record, after the current record-holder in 2011.

As stated on the NOAA website:

The bloom will be expected to measure 8.7 on the severity index with a range from 8.1 to potentially as high as 9.5. This is more severe than the last year’s 6.5, and may equal or exceed 2013, which had the second worse bloom in this century. The severity index runs from a high of 10, which corresponds to the 2011 bloom, the worst ever observed, to zero. A severity above 5.0 indicates blooms of particular concern.
"While we are forecasting a severe bloom, much of the lake will be fine most of the time. The bloom will develop from west to east in the Lake Erie Western Basin, beginning this month. It is important to note that these effects will vary with winds, and will peak in September," said Richard Stumpf, Ph.D., NOAA’s ecological forecasting applied research lead at NCCOS, who formally presented the forecast in a media event and science presentation at Ohio State University’s Stone Lab on Lake Erie today [
July 9, 2015].

Lake Erie algal bloom, October 9, 2011. Credit: NASA Earth Observatory/Landsat-5

Sources: NASA Earth Observatory | NOAA | EPA (pdf) | Health CanadaNASA Worldview

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