Blue Algae in lake at Remerschen; Credit: Erliefnis Baggerweier

On Thursday 25 August 2022, Luxembourg's Water Management Administration announced that, due to the presence of blue-green algae, a swimming ban and recommendation to avoid all nautical activities was announced for the ponds at Remerschen.

The presence of blue algae was detected as a result of regular monitoring of the quality of swimming water: a proliferation of cyanobacteria, known as "blue algae" was observed in the ponds of Remerschen.

Some species of cyanobacteria synthesise toxins that can lead to a health risk for people, aquatic fauna, pets and livestock. For people, disorders related to contact, ingestion or inhalation of these toxins are of variable nature and intensity and may, for example, include headaches, irritation and/or skin burns, or even nausea.

The Luxembourg Institute of Science and Technology (LIST) was commissioned to carry out detailed analyses to determine the species composition of cyanobacteria and the presence of toxins. The analyses revealed the dominant presence of the Dolichospermum species, potentially producing toxins, and therefore potentially harmful to health.

For these reasons, and on the basis of the amended Grand-Ducal regulation of 19 May 2009 determining the special protection measures and the monitoring programmes for the state of swimming waters, a swimming ban was pronounced with immediate effect for the ponds of Remerschen. 

In addition, the Water Management Administration, based on the assessment of the Health Department, recommends that the public:

• do not allow dogs and other pets to drink the water,
• avoid any contact with water,
• avoid all water activities (e.g. water sports, fishing).

If anyone has experienced any health problems following swimming in the Remerschen ponds during the past few days, they are advised to contact their doctor, mentioning any possible contact with toxic cyanobacteria.

With regard to the lake of Weiswampach and the beaches of the lake of the Haute-Sûre, swimming remains, at this stage, authorised. Any possible prohibition concerning these two sites will be announced to the public: the current situation concerning bathing (swimming) water (Lac de la Haute-Sûre, Lac de Weiswampach and the Remerschen ponds) can be followed online at www.waasser.lu.