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The good environmental practices presented in essentially are aimed at limiting the nutrient input (mainly phosphorus and nitrogen) into a lake. Eutrophication (aging of a lake) is a very slow natural process whereby nutrients gradually accumulate in a medium. The lake becomes rich in nutrients, which brings great changes to the fauna and flora in it. In the case of a lake, this process will generally last several thousand years and transform the lake into a marsh, then into a bog and finally into a forest. Unfortunately, eutrophication speeds up when caused by human activities; we are talking about tens of years instead of thousands. The consequences are serious for the fauna and flora of the lake, but also for those who use the lake, whether for fishing, swimming, water supply or anything else.

Aside from the accelerated aging of our lakes, other issues and consequences of the poor practices of users are described in the following sections: the appearance of cyanobacterium water blooms (blue-green algae), the proliferation of periphyton, the multiplication of aquatic plants and algae, and the potential invasion of alien species introduced by boats transported from one lake to another. References are provided for each subject.

The water blooms that concern residents are caused by cyanobacteria, called blue-green algae; but in fact, scientists now consider them bacteria. However, even if their presence in our lakes is normal, there are problems when they proliferate abnormally. In this case, they become visible in the form of a flower of water (or bloom); they then give a bluish to greenish color to the water, take on a filamentous form or form foam on the surface of the water. These water blooms may look like broccoli soup, pea puree or spilled paint. These water blooms are occasionally reddish, but more often green or turquoise. Some species can produce toxins that are dangerous for our health. These toxins can cause irritation of the skin, nose, throat and eyes as well as stomach upset, vomiting and diarrhea if swallowed.

Cyanobacterial blooms occur in lakes that receive significant nutrient inputs, particularly phosphorus. Blue-green algae blooms can be triggered by a variety of physical factors, such as high water temperatures, water stagnation and inputs of phosphorus. The latter is identified as the main culprit. Indeed, like algae and aquatic plants in general, cyanobacteria need nutrients for their growth. When nutrient inputs, including phosphorus, are abundant, cyanobacteria proliferate and grow rapidly, invading bodies of water. Phosphorus inputs are naturally present via water runoff, animal waste and the decomposition of organic matter, but we must add the growing number of human sources. Fertilizers, septic waste, soaps and detergents, fireworks, wood-burning ashes, overdevelopment and shoreline degradation all contribute to increasing the amount of phosphorus in the plans. A single episode of water bloom was recorded at Cedar Lake in 2018 and reported to the provincial ministry.

These water blooms can affect the health of water users if the cyanobacteria and toxins they produce (cyanotoxins) are present in excessive amounts. Users most affected are those in direct contact with the water (swimming, windsurfing, playing at the water's edge, etc.). Sources of drinking water can also be affected. Adequate treatment must then be applied. The provincial department is responsible for the Intervention Plan for the Management of Cyanobacterial Water Blooms in Quebec. In the field, regional directorates act on behalf of the department. They collaborate closely with public health departments. From the information provided here, if you suspect the presence of water blooms, please report the situation immediately to the Cedar Lakes Association/l’Association de Protection des Lacs des Cèdres (APLC), which will notify the Outaouais Regional Office of the provincial department using the form « Constat visuel de la présence d’une fleur d'eau de cyanobactéries ». (Visual observation of the presence of a cyanobacterial water bloom). For more information on preventing the health effects of cyanobacteria, see reference documents.

Supporting documents (some only available in French)

Cyanobacterial :

Periphyton :

Invasive aquatic plants :

Aquatic plants :

Eutrophication :

RAPPEL - information sheets: