The presence of phosphates in water is an important detail in water quality.

Phosphorus is essential for life. It is needed for plant growth and metabolic reactions of plants and animals.

Because algae only require small amounts of phosphorus to live, excess phosphorus causes extensive algal growth called 'blooms' which are symptoms of eutrophication.

Eutrophication is the human-caused enrichment of water nutrients, usually phosphorus. This comes from run-offs from pesticides from agriculture fields. Intolerant species cannot survive eutrophication and are replaced by more tolerant species.