How do fertilisers contribute to eutrophication in water bodies?

Fertilisers contribute to eutrophication in water bodies by increasing the nutrient levels, particularly nitrogen and phosphorus.

Fertilisers are substances that are added to soil to supply essential nutrients to plants. They are rich in elements like nitrogen, phosphorus, and potassium, which are vital for plant growth. However, when these fertilisers are used excessively or improperly, they can wash off into nearby water bodies during rainfall or irrigation. This process is known as leaching.

The leached nutrients from the fertilisers increase the nutrient content in the water bodies. This sudden influx of nutrients, particularly nitrogen and phosphorus, leads to a rapid growth of algae and other aquatic plants, a phenomenon known as an algal bloom. This is the first stage of eutrophication.

As these algae and plants die, they sink to the bottom of the water body and start to decompose. The decomposition process is carried out by bacteria, which consume a significant amount of oxygen in the water. This leads to a decrease in the oxygen levels in the water, creating a condition known as hypoxia.

Hypoxia is harmful to aquatic life, particularly fish and other organisms that require oxygen to survive. It can lead to a significant decrease in biodiversity, as species that cannot tolerate low oxygen levels die off or move to other areas. This is the final stage of eutrophication.

In summary, fertilisers contribute to eutrophication in water bodies by increasing the nutrient levels, leading to algal blooms, decomposition, hypoxia, and ultimately, a decrease in biodiversity. It's a complex process that highlights the importance of using fertilisers responsibly to minimise their environmental impact.