To determine the state of a river, researchers have been analyzing algae communities on rocks along rivers for the past 20 years.
They are called diatoms.
“When you walk along the rivers, the rocks are very slippery and slightly brownish, they are diatoms, there are astronomical quantities of them”, explains Stéphane Campeau, from the University of Quebec at Trois-Rivières and member of the Center for Research on Watershed-Aquatic Ecosystem Interactions.
The researcher knows what he is talking about, since it was he who designed the Eastern Canada Diatom Index (IDEC) with his student, Isabelle Lavoie, now at INRS.
“We take a sample from the rocks and look under a microscope to see what algae are present, and from that we made an index that varies from 0 to 100; 100 being the best rivers in eastern Canada, so clean rivers, and 0 being the worst rivers in eastern Canada.”
For example, there are 8 rivers or streams that have the worst rating of 0.
These algae undergo all the disturbances of the watercourse. “They are representative of all the stresses that the river undergoes (heavy metals, pesticides)”, he says.
“When there are a lot of pesticides in a river, it will inevitably affect the diatoms, adds Isabelle Lavoie. When there are a lot of pesticides, it is generally because it is a heavily agricultural basin and it is rare that there are just pesticides. There’s going to be a lot of nutrients in the water and that’s going to move the value of CEDI.”
Diatoms, brown micro-algae on rocks bordering waterways, reveal the state of health of rivers
Courtesy
8 rivers with the worst index of zero
- Champlain River in Saint-Maurice in Mauricie
- Rivière des Chutes in Saint-Narcisse in Mauricie
- Petite rivière du Loup in Louiseville in Mauricie
- North River in Saint-André d’Argenteuil, Laurentians
- Rouge River in Saint-André d’Argenteuil, Laurentians
- Bédard River in Alma, Saguenay-Lac-Saint-Jean
- Bernier stream in Saint-Boniface (MRC Maskinongé), Mauricie
- Lavergne stream in Saint-Boniface, Maskinongé, Mauricie
►It is in the watershed of the Richelieu River that we find the most rivers in very poor condition (eutrophic), i.e. 13.
►If we look at the integrated water management zones by watershed, those of Châteauguay (Montégérie), Richelieu (Montégérie), Saint-Maurice (Mauricie) and Loup-Yamachiche (Mauricie) have the most rivers in poor condition .
-With the collaboration of Philippe Langlois