Algae known as sea lettuce is flooding the beaches of Brittany. Scientists attribute this to the development of agro-industrial complexes, in particular pig farming, livestock farming and poultry farming.Nitrates and phosphates from fertilizers and animal waste pollute the water system and end up in the sea, where they feed algae and cause algae blooms.Once on the shore, the algae decompose and release toxic gases, putting the health of people and animals at risk.