The government is asking the general public to chip in and gather data on the hazard

Luxembourg is asking members of the public to join the fight against blue algae, a hazard for humans and animals, just as temperatures are tempting residents of the Grand Duchy to take a dip in a lake.

Swimmers or hikers can now report confirmed or suspected manifestations of the bacteria via an app called "Bloomin’ Algae", which the Luxembourg Institute of Science and Technology (List) designed together with the water management agency, both organisations said in a joint press release.

Onlookers can send photos of the bacteria, which sit on top of the water and shine in a green-blue colour, and their precise location via the app. Researchers will then validate the sighting and load the data on an interactive map which the general public can consult.

That way, researchers are hoping to gather more data on blue algae, which also threaten the environment, the press release. The water management agency and List are particularly interested in the Upper Sûre lake, Luxembourg's largest freshwater reservoir, the Weiswampach lakes and the Moselle river.

Blue algae, scientifically known as cyanobacteria, grow between August and October and re-produce best in calm and nutrient-rich waters, like lakes, ponds and rivers.

"To grow, cyanobacteria need high concentrations of nutrients, especially phosphorus, which can come from many sources: livestock effluents, compost, fertilisers spread on the soil, inadequately treated wastewater discharges, soil leaching during heavy rainfall," the release said.

"Reducing phosphorus and nitrogen inputs into surface waters remains the only sustainable way of protecting and/or restoring these ecosystems from planktonic cyanobacteria blooms," it added.