How Does EUTROPHICATION Work? Causes, Process and Examples

Eutrophication Process

Last Updated: Sep 12, 2018

What Causes Eutrophication?

Eutrophication occurs in water bodies when too many nutrients are introduced. This is often near farm fields where farmers apply excess nutrients to the soil.

Because of runoff from farm fields, fertilizer enters the water. Eventually, it get drained into the water body or leach into the ground.

In turn, the fertilizer rich in nitrate and phosphate sparks the overgrowth of plants and algae in water bodies.

This is how come eutrophication means ‘well-nourished’ in Greek. But in this case, it’s more like an ‘over-nourished’ water body.

What is the Eutrophication Process?

Basically, over-fertilization of water causes algae to grow on the surface. When fertilizer enters into the water, this becomes food for algae.

From here, algae reproduce and cause a thick green bloom in the water. Because algae absorbs sunlight, it prevents it from reaching the bottom.

When algae grows to such an extreme level, it entirely stops light reaching plants in the water. Eventually, plants that need sunlight cannot photosynthesize and die.

Eutrophication Process
The eutrophication process

What are the Effects of Eutrophication?

From here, bacteria begins to decompose the remains, using up oxygen for respiration. This releases more nutrients in the water repeatedly into the an ‘Algal Bloom Cycle’.

The decomposition causes the water to become depleted of oxygen. Over time, this causes the water to carry less oxygen than before.

At this point, fish cannot swim and suffocate to death in the water. Overall, this water body can no longer support life. Finally, water without oxygen is anoxic and becomes a dead zone.

Eutrophication Examples and Dead Zones

Eutrophication disturbs the aquatic life through nitrogen-enriched fertilizer. Over time, this imbalance can cause aquatic life to start dying and in the worst case scenario a complete dead zone.

And dead zones are more concentrated where we have industrialized nations. Especially, industrial farming practices that contains nitrogen and phosphate or animal waste.

For example, here is the world of dead zones. You can see areas like the Caspian Sea completely filled with algal blooms.

How can we fix dead zones? The best answer is preventative techniques to reduce fertilizer in runoff.

eutrophic dead zones hypoxia

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