Neon green paint on a Black mans profile to depict an algal bloom
Neon green paint on a Black mans profile to depict an algal bloom
Image by Olivier Yoan, "Painting" by Khandiz, Muse: Reece Pantry

A Blooming Catastrophe

By Khandiz Joni

Algal Blooms: What Causes Them, Their Impact on us, and Ways we can Reduce their Damage

Like human organs, the 9 Planetary boundaries function as Earth’s monitoring and regulating system. They were established to help guide humanity in living within the means of our Planet. One of these boundaries examines the Nitrogen and phosphorus cycles – and managing their run-off into bodies of water.

When these two nutrients are over-enriched in water, they can create a ‘perfect storm’ for algal blooms.

Algal blooms smother the sea floor, deplete oxygen levels and release toxins that kill marine life. They cost coastal economies billions of dollars each year, and their impact is only getting worse as our planet warms.

As far back as 2010, 121 million tonnes per year of nitrogen was being drawn from the atmosphere, alarmingly exceeding the 35 million tonnes that the nitrogen cycle could self-regulate through natural processes. We are well beyond the safe operating zone of this boundary. Phosphorus, which is an essential nutrient for plants – and, research now suggests, crucial in helping soils store carbon – is being lost through soil erosion and run-off and in turn, contributing to creating an imbalance in a different ecosystem.

So what exactly are algal blooms, and how do they form?

Algae are simple aquatic plants that live in freshwater or saltwater environments. Under the right conditions – such as warm weather and high nutrient levels – algae can grow very quickly in a process called eutrophication. When this happens, the algae begin to outcompete other aquatic plants for sunlight and space. The algae eventually form a thick mat on the water’s surface, blocking out sunlight and oxygen from reaching the plants and animals below.

The overgrowth of algae is often caused by an excess of nitrogen and phosphorus in the water. These nutrients can come from a variety of sources, including agricultural run-off, sewage treatment plants, septic tanks and even lawn fertilisers. When these nutrients enter waterways, they provide the perfect conditions for algal blooms to form. One study found that fertilisers caused 78% of the global marine and freshwater eutrophication.

Algal bloom on Milford Lake, Kansas, USA


Depending on the type of algae, the surrounding water will take on a distinct colour, often resulting in awe-inspiring hues dancing on the water’s surface like neon marble. But, they can also be unsightly, and more sinisterly, they can be deadly. Many species of algae produce toxins that can kill fish, birds and mammals. Red Tide is one such example. These toxins can also cause skin irritation and respiratory problems in humans. In some cases, algal blooms can even lead to large-scale fish die-offs, further contributing to another boundary also alarmingly beyond a safe zone; biodiversity.

The impact of algal blooms reaches far beyond the environment. They also take a toll on local economies, as they can close beaches, contaminate shellfish beds and hurt tourism. This is why these algal blooms are costing the global economy billions of dollars each year.


In 2014, 500,000 Ohioans were without clean drinking water after Harmful Algal Blooms were found in Lake Erie near a water treatment plant.

What actions can we take to reduce our impact?

There are several ways to reduce the impact of algal blooms. One way is to reduce nutrient pollution at its source by better managing agricultural run-off and sewage treatment plants.

Or, dare I suggest swapping out your mono-culture lawn for a wild-flower meadow that doesn’t rely on artificial lawn feeds to keep it “alive”?

A painting of different kinds of flowers
Studies of Flowers (1848) painting in high resolution by Jacques–Laurent Agasse. Original from The Yale University Art Gallery. Digitally enhanced by rawpixel.

Another way to reduce algal blooms is to increase water circulation in lakes and ponds. This helps to mix up the water and prevents stagnation, which can lead to eutrophication.

While algal blooms are a natural phenomenon, human activity has made them worse. By reducing nutrient pollution and increasing water circulation, we can help to mitigate the impact of algal blooms on our environment.

What are your thoughts on this issue? Share your thoughts in the comments below or purchase a print to contribute to on-the-ground solutions.

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