How does phosphorus pollution harm the environment?

It is alleged that the two major sources of pollution in the rivers Wye, Lugg and Usk are:

1. The intensive poultry farming operations of the Avara Foods poultry group which allegedly causes phosphorus-rich manure to accumulate in the region and be spread on fields. When run-off occurs from fields, for example during rain, the phosphates pollute the rivers.
2. The operations of Dŵr Cymru Welsh Water: untreated and treated sewage, both high in phosphates, are regularly discharged into the rivers.

It is widely accepted that high concentration of phosphates in the rivers causes algal blooms, which in turn limits oxygen in the river, making it hard for wildlife to survive. This decreases the health of the river and the surrounding ecosystems.

Algal blooms can also be unsightly and odorous, resulting in insect swarms. Blue algae can also be especially harmful to animals, such as pets and livestock, and can even harm humans who come into contact with it.

Campaigners have said that without immediate and meaningful action, the rivers could suffer irreversible ecological damage.