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Water Today Title January 18, 2021

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Update 2018/5/17
Blue-green algae


This story is brought to you in part by Waterloo Biofilter Systems

by Michelle Moore

Heavy rainfall this spring could mean significant harmful algae blooms (HABs) in Lake Erie this summer. The first HABs forecast from the National Oceanic and Atmospheric Administration (NOAA) and the National Center for Water Quality Research (NCWQR) in the United States revealed that the state of the blooms could be comparable to those of last year.

Lake Erie has experienced late summer algae blooms since 2002. Lake Erie is on the International Boundary of Canada and the United States. It is surrounded by Michigan, Ohio, Pennsylvania and New York, as well as the province of Ontario. It is the shallowest of the Great Lakes and also has the greatest retention time which makes it susceptible to HABs.

Simply put, HABs or blue-green algae is a potentially toxic algae that makes water unfit to swim in and drink. It appears as a thick green slime on the surface of lake water and is caused by an overabundance of nutrients, more specifically phosphorous. These nutrients are most often caused by fertilizer runoff and improperly treated sewage going into the water.

Also called cyanobacteria, blue-green algae releases liver toxins and neurotoxins which can cause skin irritations, and gastrointestinal and respiratory issues if it is swam in. If ingested, it can potentially cause liver failure. However, because humans generally do not ingest it, this is more commonly a problem for dogs who play on the lakeshore where it tends to accumulate.

André Gagnon, Media Relations Officer for Health Canada and the Public Health Agency of Canada said in a statement to this reporter, "the development of a bloom indicates the potential for exposure to cyanobacterial cells and/or their toxins in amounts which may, in some cases, be sufficient to be harmful to human health. In general, contact with waters where a bloom exists or has very recently collapsed should be avoided."

Gagnon added that when higher than acceptable levels are found in a body of water, a drinking or swimming advisory is issued by Health Canada and that "contact with waters where an advisory has been issued should be avoided until the advisory has been rescinded." The Canadian Journal of Fisheries and Aquatic Sciences confirmed that cyanobacteria in western Lake Erie has caused beach closures and drinking water advisories in Canada.

While not every algae bloom is toxic it has been estimated that as many as sixty percent have been found to be and therefore every bloom should be treated as toxic for safety reasons. Health Canada also specifies that toxins may remain present in the water for short period after a bloom is no longer visually apparent and should therefore be avoided for some time afterward.

The first HABs projection for Lake Erie for 2018 suggests the bloom will be between a 3 and a 7 out on a scale of 10. The scale, called the severity index (SI), was established in 2014 with the 2011 bloom serving as an indication of what would constitute a 10. A 1 on the scale simply indicates a total or near total absence of a bloom.

Last year the Microcystis cyanobacteria bloom was given a SI of 8 out of 10 which is significant. By comparison, 2013 saw a SI of 8.5 which was the third most significant since 2002. The SI is calculated over a thirty-day period by analyzing the bloom biomass.

The forecast for that year was fairly dependable, having indicated a SI ranging from 6.8 and 8. Projections are updated weekly and will become more precise as we near the month of July. An official prediction will be given July 12 at Ohio State University at the Stone Laboratory.

The NOAA and the NCWQR revealed that significant amounts of spring rain caused larger than normal amounts of fertilizer runoff in the Maumee River in Ohio which feeds into Lake Erie.

Richard Stumpf of the NOAA released a statement May 4 explaining that "the current iteration of the forecast is based on the amount of phosphorus entering the lake in the spring from the Maumee River, which provides the largest single source of phosphorus into any of the Great Lakes and carries a high concentration of bioavailable phosphorus, the form most suitable for supporting algal growth and bloom formation."

The forecast indicates that the total bioavailable phosphorous (TBP) loads from the Maumee River will surpass those of 2016 for the same week but will most likely be lower than 2011 or 2015. Currently, the TBP loads are greater than 2012 and approaching levels seen in 2016.

As temperatures heat up this summer it could provide the perfect conditions for the algae to develop. The forecast said that "the phosphorus load to date is sufficient for some bloom to occur, however, the uncertainty is quite large."

The extent of the bloom will depend on whether there are sustained warm temperatures as well as the amount of precipitation received between now and then; "because the forecast uses modelled discharge for two months, there is a large uncertainty in bloom severity," the forecast said.

In February 2018 the International Joint Commission (IJC) released their report titled Fertilizer Application Patterns and Trends and Their Implications for Water Quality in the Western Lake Erie Basin.

The IJC Assessment began in 2016 the same year Canada and the U.S. announced new targets to reduce the amount of phosphorous going into Lake Erie by 40%. The assessment confirms that the application of commercial fertilizer and manure are the primary sources of phosphorus in Lake Erie.

The report pinpoints that fertilizer that is stored in ditches, buffer zones and wetlands represent a potential increase in the nutrients for years and possibly even decades to come. It stated that "even a small 'leakage' of excess phosphorus may be sufficient to contribute to algal blooms."

Moreover, it specified that the manner and timing of application were the cause. If fertilizer is spread shortly before rainfall, then much of it tends to run off into nearby waterways before it can be absorbed and mixed into the soil. The report suggests that there be a review of current practices with the goal of reducing the levels of phosphorous that find their way into the lake.

Certain agricultural practices like conservation tillage also seems to contribute to the increase of phosphorous going into the lake as well as climate change. The last few years saw warmer temperatures and heavier rainfall than normal which both tend to result in greater amounts of phosphorous running off the fields.

The report stated that "phosphorus control measures enacted in the 1970s demonstrated that Lake Erie eutrophication could be reversed ... the challenge this time is with agricultural nonpoint sources of nutrients, which will require a different set of responses. Lake Erie has benefitted from bold action in the past and requires similar bold action today to ensure its health and value to the people of the basin into the future."


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