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Use the effects of harmful and toxic algae as indicators for monitoring the quality and eutrophication of the water

Context and project description

For complex problems, look at all the angles. The proliferation of harmful or toxic algae in the St. Lawrence ecosystem is a growing phenomenon that is more and more concerning for riverside communities. Several effects of these flowering blue, brown, or blue-green algae or the appearance of red tides are well known: for example, the ability of certain algae to produce toxic compounds that attack the liver or nervous system of the organisms that eat it, or that alter the taste, smell and aspect of drinking water. However, we are very familiar with the significant mortality of fish that occurs following a decrease in the levels of oxygen in the water, caused by the degradation of the algae biomass.

We know that the problem is largely related to eutrophication, but, overall, the phenomenon is not well understood. Which specific algae are toxic? What factors control the flowering of algae and the production and transformation of toxins in the ecosystem? What long-term effects are caused by the exposure of aquatic organisms to these algae? In short, how does the presence of toxic algae change the ecosystem? These are the questions that several researchers will study as part of this project. The research will cover a very large range of work on several species of algae and exposed organisms (mollusks, crustaceans and fish) from one end of the St. Lawrence to the other.


We have learned more about toxic algae and their effects on the St. Lawrence ecosystem. As part of this project, a scientific article on the spatiotemporal distribution of a toxin in Lyngbya wollei (cyanobacteria) mats in Lake Saint-Pierre and Lake Saint-Louis was published in the journal Harmful Algae [1] in spring 2016. According to the authors, water quality is not the most important factor in the proliferation of toxic algae. They conclude that monitoring Lyngbya wollei abundance is necessary to assess the associated risks to human health and to the environment. The research conducted in this project has therefore provided a better understanding of the factors involved in the appearance of harmful algae in the St. Lawrence. This work is continuing in order to further document the factors responsible for toxic algae blooms.

[1] For more information, see the original article, “Spatial and temporal variations of a saxitoxin analogue (LWTX-1) in Lyngbya wollei (Cyanobacteria) mats in the St. Lawrence River (Québec, Canada)” (Harmful Algae, 2016, No. 57, pp. 69–77).

Participating departments

Government of Canada

  • Environment and Climate change Canada
  • Fisheries and Oceans Canada

Government of Quebec

  • Ministère du Développement durable, de l’Environnement et de la Lutte contre les changements climatiques
  • Ministère des Forêts, de la Faune et des Parcs