Toxic blue-green algal bloom in water supply.
Death by Algae

The Dangers of Toxic Blue-Green Algae (Cyanobacteria)

Algae has often been the cause of serious sickness and death in humans and animals over the course of history. There is a common perception that blue-green algae are toxic and can cause sickness or even death. This is supported by numerous cases around the world which have been well documented.

It is interesting to note, however, that not all blue-green algae are toxic.

Additionally, less well known is that it is not actually the algae which is toxic, but the toxins they produce. This means that, even if the algae are killed, the toxins themselves can remain viable. These typically break down and eventually become harmless over a further period of time.

To further complicate things, it is impossible to identify toxic blue-green algae, just by looking at it. Further examination or testing is required to pin down the exact variety and know with certainty the level of toxicity. With the potential severe risk to human or animal health, it is safer to err on the side of caution when dealing with an algal problem.

Known cases of fatalities due to algae

Whilst numerous cases of animal deaths have been recorded, human exposure has generally been limited to allergic reactions and illness. There have been a few unfortunate exceptions, however.

One of the worst was a tragic incident that occurred in north-east Brazil involving patients in a haemodialysis unit.

In February 1996, 126 patients developed symptoms of acute neurotoxicity. At first, it was a mystery, until they discovered it was a direct result of tainted water used for haemodialysis. The water used was sourced from a lake contaminated with cyanobacteria. Unfortunately, this resulted in the death of 60 patients.

Issues of blue-green algae throughout history

Rather than being a modern dilemma, blue-green algae problems extend way back into history.

Ancient Mayan Civilisation

The ancient Maya city of Tikal in northern Guatemala flourished from the second to ninth centuries.

The city was eventually abandoned due to a range of social, political and economic factors. Another interesting reason, though, was contaminated water reservoirs.

Tikal’s climate during that time included a long dry season with almost no rainfall. This left the Maya with the difficult task of finding clean water for drinking, cooking and irrigation.

Researchers from the University of Cincinnati analysed the ancient DNA buried at the bottom of the reservoirs and detected two types of blue-green algae. These types of algae are known to produce toxins that caused sickness, even if the water was boiled.

Today, Tikal is a National Park and UNESCO World Heritage site that is the subject of intense study.

The problem would have worsened to the point where the presence of blue-green algae blooms was visible on the top of the water and unpalatable if consumed.

Witnessing a vital symbol of life transform into the cause of sickness or even death could have been a factor in why they abandoned the city, with research still being conducted to this day.

Land and water management

Effective land and water managements is important for our personal and environmental health. History, both modern and ancient, shows us the results of not doing so. It is imperative to manage our land and water well to avoid the mistakes of our past.

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