Cyanobacteria proliferate in Ile-de-France, watch out for dogs and fishing

By My B. Photos by My B. Posted Aug 29, 2022 4:56 PM

Cyanobacteria, these harmful micro-organisms also called “blue algae”, tend to develop in Ile-de-France. Following the various heat waves and high temperatures that have favored their development, making swimming prohibited in various lakes and leisure centers in the Ile-de-France region, caution is required, especially for animals and therefore dogs who like to jump into the water. Indeed, the effects of these cyanobacteria can prove fatal for your companions and make the fish unfit for consumption.

The cyanobacteria are micro-organisms that occur naturally in soil, plants and water. On a stagnant high, when the temperature rises and nutrients such as nitrogen and phosphates from fertilizers and human activity are added, they can proliferate massively and release harmful toxins.

Indeed, cyanobacteria release a toxin that can be very dangerous for humans and even deadly for animals and in particular dogs. They can thus act on the skinare mucous membranesthe liver and the nervous system and cause digestive disorders such as vomitingand diarrheadizziness, discomfort and skin infections.

This year, the heat never ends and the drought with it. With less water and less renewal, the water bodies of France’s Island are increasingly vulnerable to cyanobacteria. According to Le Parisien, a team of researchers from the National Museum of Natural History estimates that 40% of the 980 bodies of water in the region have more or less large quantities. This could have consequences on nautical activities, but not only.

You should know that in Ile-de-France, surveillance of the ARS is only done 4 times per season by sampling and visual monitoring. And that, only on bathing sites, which means only 18 bodies of water out of the 980 in Île-de-France. Systematic testing of all water bodies would be too expensive, says Christophe Laplace-Treyture, hydrobiologist and algologist at the National Institute of Agronomic Research (Inra) at Parisien.

Among the water bodies most vulnerable to cyanobacteria in Ile-de-FranceWe count :

  • Cergy ponds
  • Harvest Lake
  • The ponds of Triel-sur-Seine
  • The lower lake of Boulogne-Billancourt
  • The Lake of Meaux Park
  • The ponds of Breuillet
  • The ponds of Fontenay-le-Vicomte
  • The Ponds of the Grande-Paroisse
  • The Ponds of Varennes-sur-Seine
  • Seine-Port Pond
  • The Lake of Evry-Courcouronnes

To observe and understand this phenomenon of proliferation, the National Museum of Natural History (MNHN) has conducted 3 research projects since 2008. In order to narrow the search and target the bodies of water most likely to be infected, the museum has categorized the plans according to their hydrographic zone, their size, their surface and their use, without forgetting the surrounding population density.

On the 5 lakes selected at random according to the categories, analyzes were made for each season. Cyanobacteria have been detected in 49 out of 50 water bodies analyzed and are dominant in 12 of them. VSe which means that a quarter of the bodies of water in Île-de-France would be dominated by cyanobacteria according to the thesis of Arnaud Catherine, entitled “Determinism of blooms and toxicity of cyanobacteria in peri-urban areas (Ile-de-France)”, supervised by Cécile Bernard and Marc Troussellier.

Currently, the lakes of the Leisure Island of the Boucles de Seine and Holland ponds are currently prohibited for swimming and nautical activities following surveys carried out by the ARS, amply exceeding the limit rates.
If you detect blooms of green algae a little fluorescent on your bodies of water with nauseating odors, caution is therefore required, especially for dogs. Episodes of dog deaths are regularly attributed to cyanotoxins.Regarding fishing, LAFFSA (French Food Safety Agency), in its opinion of June 5 2008, states that the evisceration of fish before consumption does not seem protective enough for health because of the demonstrated contamination of muscle flesh. It is therefore recommended not to eat fish caught in lakes and bodies of water infected with blue-green algae. Recreational fishing can be maintained on the condition that you rinse your equipment well with clean water after use.

Note that non-toxic algae may also grow on lakes and ponds in Île-de-Franceonly analyzes can confirm or not the presence of harmful cyanobacteria.

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