The joys of eutrophication: discover the algal bowl!

Beware of eutrophication!

Summer is (almost) on us, the urge to swim is overwhelming… But why are our lake waters becoming greenish and gluey? 

The answer lies in this book published by the Alberta University Press:  The Algal Bowl: Overfertilization of the World’s Freshwaters and Estuaries, by  David W. Schindler and John R. Vallentyne. The authors are specialists in lake biology, a field that my uncle Robert Lagueux, limnologist, knew well.

 The Algal Bowl: Overfertilization of the World’s Freshwaters and Estuaries, par  David W. Schindler et John R. Vallentyne

The Algal Bowl is a very specialised text about the eutrophication of freshwater and estuaries. The book is replete with maps and schemactics, graphics, measurements, statistiqcs… It is a way more reliable information source than rumors on dubious websites; for this reason, I decided to take about 40+ hours of my free time to vulgarize its content.

The title is an allusion to the famous Dust Bowl of the 1930.

“In 1974, John R. Vallentyne predicted that by the year 2000 we would be living in an environmental disaster he called the Algal Bowl. Just as the Dust Bowl of the 1930s was created by misusing western farmland, he forecast that the continuing misuse of lakes could only lead to water degradation. “

On a litterary standpoint, this book is well written, with impressive images that stay with the reader’s mind.


A short plot summary for the non-specialists

Put loads of shit into fresh water.

Lots of it: fecal matter,  nutrients, fertilizers, organic matter. The organic matter, while decomposing, uses up most of the water dissolved oxygen. As the fish need oxygen too, they die. Other organisms take their place, modifying the aquatic ecosystem.

Lake euthrophication is a silent murder, with only the algal blooms  by cyanobacteria, as warning signs. Those microorganisms exist since more than three billion years. They are usually presents in streams and lakes, but in very small amounts, so they go mostly unnoticed. But, in large concentrations, cyanobacteria, far from being gentle vegetals, exudes  very toxic substances, causing fish (and the occasional swimmer) death.

The first warnings

Eutrophication was observed as soon as 1890, in Europe (lake Zurich), to describe modifications on aquatic ecosystems caused by a rise of plants nutriment to the water.

As lakes are not talkative  by nature, researchers observed eutrophication process signs as early as the 1960s. By monitering the water quality of the affected lakes, and comparing those results with untouched lakes, the investigators came up with three suspects: carbon, nitrogen and phosphorus.  But which of those three holds the control key to the eutrophication process?

Witness questioning: Lakes Mendota et Monona

Aerial view of lake Monona (with a part of Mendota Lake). The high density city squeezed between the lakes is Madison.

Aerial view of lake Monona from the south (with a part of Mendota Lake). The high density city squeezed between the lakes is Madison. From the Univ. of Wisconsin, Limnology department.

The study of Madison City (Wisconsin) lakes Monona et Mendota, shows the impact of the forest cutting and agriculture with fertilizers about fauna and flora.

Arrived in 1840, the settlers cleared the forests to reclaim the land around the lakes. In four decades, native vegetation was replaced by farms and Madison had becomed a prosperous town.

Except that… strange phenomenas appears in Mendota Lake. In 1880, algal blooms killed fishes, whose bodies lined the shores. Evidence pointed at sewage discharged into lake Mendota by the 10 000 habitants city.

To solve the problem, they did not dawdle: a dam was erected to raise the lake waters level; wetlands were drained (their natural filter capacity was not discovered yet), and wells were digged to catch the groundwater. The level of Lake Mendota was raised of 1,5 m by the construction of a dam in 1847.

The 1880s saw the first attemps at sewage treatment; a larger plant was raised in 1914 as population grew. So this plant removed the fecal and organic matter, but not the fertilizers, nitrogen and phosphorus. The plant effluent was discharged into the yahara river, then in Lake Monona.

Lake Mendota waters returned to their pristine and pure aspect. Meanwhile, Lake Monona became the theater of unexpected blue-green algae blooms. In the 1920, thick mats of floating algae were pushed to the shores by the winds. They  exhaled a putrid breeze that forced residents to close their windows in summer!

So the authorities reacted :  copper sulfate was applied too lake Monona to kill thos pesky algae! The fear of chemical products had not taken hold at the time and from 1926 to 1936, 27 – 45 metric tons  (60 000 – 100 000 lbs) of this poison were applied each summer to the Monona Lake waters. By guy working without gloves or chemical protection, like in the pics below.


Those chemical additives and the dead algae formed layers of copper-rich sediments… who are wtill present today!

Please DO NOT DISTURB the lake bottom!

Meanwhile, true to their good habits, the authorities built in 1928 a brand new sewage treatment plant. They took care to divert the plant effluent into the Yahara river  below lake Monona!

Problem solved? Look closely at this following pic… The little green arrows show the water flow direction.

The water flows in the Madison area four lakes

So Lake Monona water quality did improve, while downstream Lakes Waubesa and Kegonsa began developing – surprise, surprise! —  eutrophication symptoms, with algal blooms, kill fish, etc.

What to do, what to do? Applying more generous amounts of copper sulfate…

Chemical Treatment Chart

As for poor Yahara river downstream of the lakes, its water were so affected that all fishes below the point of the sewage effluent discharge were killed in a blue algae bloom in 1954. Algae and decaying organic matter consumed all dissolved oxygen leaving non for the fishes.

So scientifics investigated, and quickly put their finger on ponctual pollution sources, like sewages from communities upstream of Lake mendota. But the problem from non-point sources remains: synthtic fertilizers to support cron crops. 575 000 kg of phosphorus  was applied to the lands around lake Mendota since 1970.

A new problem came along with a popular sport: angling, causing a resurgence of algae. How is that possible?

The trophic cascade summarized!

Big fish eat small fishes.
small fishes eat animal plankton.
Animal plankton eat algae.

Trophic Cascade

If enthusiast fishermen remove big fish from lakes, smaller fish multiply and eat more of animal pankton, resulting in more abundant algea! Those algea cut the light reaching the bottom. This is a trophic cascade, freely taken from a diagram in the book, page 173 . For more details, see Wikipedia  trophic levels.

We lost the chemical war, let’s fight on the biological front!

Taking this relation in tow, the managers decided to restore the pishivorous population in Lake Mendota.  Between 1987-1999, predator fishes were added to the lake, hoping to get less algae: 2.7 millions of  Walleye fish, 170 000 northern pike and more were added in the lake. The waters clarity improved. But…

The rumor spread in the angling community. Thousands of enthusiasts increased pressure on the big fishes six fold, mitigating the biomanipulation impact.

Today, the Lake water are in better shape than the beginning of the XXe century. But the growing population (Madison being Wisconsin capital), and the accumulation of fertilizers in soils, would make that even if all pollution stopped, surface runoff would leach nitrates and phoshates for dozens of years (p.27).

On the following map, the red areas are urbanized zones, while the mauve are the wetlands, those essential natural filters (they work slowly, but they work!). Note the domination of the yellow cultivated area.

4 Lakes Madison Map

Recent studies evaluated at 50 millions $ the fresh water restauration, considering the lost écosystems. I have visited Madison two times now. I can’t express how much the Lakes give a breaktaking view to the voyagers.

Also, to know more about the Madison Lakes:  go consult the nice colored presentation by Richard C. LathropControlling Eutrophication in the Yahara Lakes: Challenges and Opportunities, presented at the Spring 2009 Community Environmental Forum UW-Madison Nelson Institute of Environmental Studies.
Lathrop, R.C., S.B. Nehls, C.L. Brynildson, and K.R. Plass. 1992. The fishery of the Yahara Lakes. Technical Bulletin No. 181. Wisconsin Dept. Natural Resources, Madison, WI.

The investigation progresses…

The 3 suspects

Let’s go back to our three suspects.

Research lead the water detectives to think that phosphorus is the controlling element of plant growth. Micro-organisms feed on nutrients in an optimal  C/N/P rapport of about 100/(4-5)/1.  “About”, because this optimal C-N-P ratio changes following a aquatic or terrestrial environment.

A consensus was reached as soon as in the 60s among the scientific community. Phosphorus was the culprit, without doubt.  And the city effluents were rich in phosphates, coming from the detergents additives.

Everything seemed to fall in place: a legislation was drafted to replace phosphates by NTA (sodium nitrilotriacetate). NTA had been the most severely tested product in te USA history. In 1969, USA were on the verge to solve the eutrophisation problem by eleimnating phosphates from the detergents.

But why did the USA wait 40 years before banning the phosphates?

The soap industry conterattacks!

Phosphorus was good and cheap, why replace it? Anxious to protect their business, soapers (US Soap and Detergent Association) at first denied the phosphorus role in lake eutrophisation, despite all studies pointing to the contrary.

So they chose to interpret backward the conclusion of a long-term study: Phosphorus is not causing the algae, it’s the algae that cause phosphorus presence!

Scientists on the soaper’s payroll proposed that nitrogen was the controlling agent, using data from Lake Erié. But a close examination showed that, in the Lake Erié case, there was so much phosphorus in the water that nitrogen had become the limiting element.

Then, by a now well known tactic (like the acid rain saga and the current global warming denying), the soapers published an incendiary article denouncing the witch hunt “against”  phosphorus, condamned withou a fair trial. Ignoring the large scientific consensus, the article tried to deflect the passions by proposing carbon as the controlling element. The hidden goal was to take advantage of the uproar in order to delay the adioption of measures.

The detergents protest!

The red herring : carbon

In 1969, a new study advanced that carbon, underthe form of dissolved organic carbon (DOC), was the liming agent of algal growth. Of course,  the soap companies were more than happy to publicise this research, hoiping tpo deflect the eco-detective’s  research.

This hypothesis was based upon bottles of sampled water, undergoing lab tests.

But a lake is not a bowl of soup; it is an interactive ecosystem, with the wash basin  and the atmosphere.   Dr. Jack Vallentyne put together a large scale experimentation, more reliable than water bottles.

To check the carbon control hypothesis, nitrogen and phosphorus  were added, without any carbon. If carbon is the controlling element,  this lake should stay ologotroph. Soon, Lake 227 show signs of eutrophisation and, after a few weeks, an algal bloom.

So, carbon is not guilty, your honor!

A mystery lingers : dissoved carbon measures change between day and night. Plus, the algeas contain even more dissolved carb. Where does it come from?

Our detectives don’t give up. They call upon Dr Broecker, a gas exchange specialist. Carbon (under the form of sucrose) is added into a small lake. Monitoring show that this carbon is quickly absorbed by the algea, then released as fast into the atmosphere as CO2.

Carbon concentation in water stays the same because the excess flee into the atmosphere. If there is a lack of dissolved carbon, the algea repleted with phosphrus draw carbon from the atmosphere. This process explains the recording of dissolved organic carbon in absence of any nearby carbon sources!

The truth revealed with lake 226!

In Canada, the Experimental Lake Area (in northern Ontario) allows long-term studies in real scale. Among those lakes, Lake 226 stands out. This figure-eight lake was divides into two parts. One received the tres amigos P, C, N, while the other received only  Nitrogen and carbon doses.

And the answer is…. One picture, that brought all soaper’s  theories to an halt:

ELA_lac226_ the final proof

This is a view of lake 226  from the Lake Scientist website, from Dr Schindler’s article (Web article here  ) after only two months!

Shocking, isn’t it?

The dark blue side is the oligotrophic lake, from oligo, few, and trophic, to feed. The pale green side show the tell tale marks of advanced eutrophisation: algal bloom, fish population drop, among other impacts.

A usual, it has taken the patient work of scientists, plus a loooong-term real scale studies on lakes to reach the conclusion that phosphorus is the key controls to lake euthrophisation.


Dr Schindler continue watching over Alberta’s fresh water bodies, not without annoying some politicians. His team has released in 2010 an article about the bituminous sands exploitation impacts over the Athabasca. Another summary here.

A short time before the french version was published, I learned that the  Experimental Lake Area (ELA) was to be suppressed by the federal government, among a train of  budget cuts.

Fortunately, in spring 2014, the Ontario government allied with two organisms to continue research activities on the ELA.

Advance euthophication of a lake


This text is my own contribution to science vulgatrisation in my own former field of environmental geography. (My own M. Sc. memoir was about the Origin and evolution of two southwestern Quebec wetlands, dealing with pollen sampling and reconstitution of the paleoenvironments.)

3 responses to “The joys of eutrophication: discover the algal bowl!

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