Analysis of the blue algae present at Luxembourg's swimming sites

Published on 03/08/2018

On Tuesday 31 July 2018, the Luxembourg Institute of Science and Technology (LIST) shared its expertise in environmental microbiology at a press conference focusing on awareness and prevention measures following the declaration of the presence of blue algae at Luxembourg’s swimming sites.

Indeed, LIST had been commissioned by the water management authorities following an observation of the proliferation of cyanobacteria, also known as blue algae, at the Haute-Sûre and Weiswampach lakes. These cyanobacteria produce toxins that are potentially dangerous for humans, aquatic wildlife, domestic animals and livestock. Microscopic in size and practically invisible to the naked eye, they can cause headaches, gastroenteritis, skin irritations and more importantly, can even subsequently attack the liver and the brain.

Sample testing confirms the presence of toxins

LIST continuously takes water samples at different locations at the Haute-Sûre and Weiswampach lakes, representing two of the three swimming sites in Luxembourg. Researchers then carry out detailed analyses in order to determine the species composition of the cyanobacteria.

They were able to confirm the presence of the toxins emitted by the cyanobacteria in their laboratory. They were also able to establish that the toxins present in the water came from the Microcystis sp. Species in particular, a freshwater cyanobacteria.

An early appearance with long-term consequences

Such an appearance of cyanobacterial blooms is exceptionally early and has an impact on the Luxembourgish economy and tourism. As a consequence, their proliferation resulted in a bathing and water sports ban at the end of July, with immediate effect. This ban will remain in effect until the cyanobacteria has cleared. On this point, LIST experts do not expect to see an improvement in the situation before October or November, when the water masses merge again and the temperature drops.

Currently, only the Remerschen ponds have been spared from the cyanobacteria and their toxins. This swimming site remains open to the public but monitoring has been increased. LIST researchers are ready to act in the event that cyanobacteria are observed.

Water resources to be protected

The reasons for this massive increase in cyanobacteria may be a consequence of the fine weather that the country has been enjoying for the last few weeks, but this cannot explain everything. Even the composition of the water, loaded with nitrogen and phosphorus, must be taken into account.

In coming years, the protection of water resources must therefore be at the heart of these discussions. Limiting the amount of nitrogen and phosphorus in bathing water, thanks to improvements in both waste water treatment and discussions with catchment basin operators, is proving to be indispensable.

Photography: copyright Police Grand-Ducale

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Dr Christian PENNY
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