Farmers spray fertiliser on fields

Fertiliser contains ammonium ions and nitrate ions, which help crops grow

When it rains, fertiliser dissolves water

Fertiliser enters rivers through a process called leaching

Fertiliser makes algae in rivers grow quickly (algal bloom)

Algae grow more quickly and block the light

Pond plants die due to lack of light, which should be used for photosynthesis

Bacteria in water decay dead plants

Bacteria use up the oxygen during aerobic respiration

Fish die from lack of oxygen - diminishing all life from the river