Biology

Abitibi mussels as “sentinel species”

In mining regions, the plumes from industrial chimneys release various metals into the atmosphere, and these eventually precipitate into lakes. Not all of them are equally toxic. Nickel, lead, zinc, and copper are less toxic than cadmium, which is almost as toxic as mercury. Cadmium accumulates in lake sediments, and can have deleterious effects on invertebrates.

To measure cadmium contamination levels, the team led by Bernadette Pinel-Alloul, a researcher in the Interuniversity Research Group in Limnology and the Aquatic Environment (GRIL) and Professor in the Department of Biology at Université de Montréal, selected as her sentinel species Pyganodon grandis, the Giant Floater, which filters water and thus retains cadmium. The team adopted to approach the problem at several biological levels, from the cell to populations.

Olivier Perceval, a doctoral student, is interested in the state of health of bivalve populations (density, biomass, growth rate, productivity, etc.) subjected to different concentrations of cadmium. “When the ambient concentration of cadmium is high, bivalves are less numerous and reproduce less efficiently,” the young researcher points out. In the most contaminated lakes (Vaudray and Heva), the bivalve density was 0.02 individuals per, m 2, but reach be as high as 1.5 individuals per m 2 in uncontaminated lakes (Opasatika). For more than ten years GRIL researchers have been collaborating with their colleagues at INRS-Water, Land and Environment to evaluate the effects of metal accumulations in aquatic invertebrates such as bivalves and insect larvae. Since 1989, the team has been studying the effects of mining industry waste in the Rouyn-Noranda region, in Abitibi, by taking samples from ten lakes located upwind and downwind of the foundry’s atmospheric effluent.

Among the toxic metals present in the environment, cadmium is especially disturbing because its effects are difficult to measure. A protein, metallothionein, could give ecologists the boost they need. “With a biological marker, or biomarker, it is possible to estimate the bioavailable cadmium in the lake, measure its potential toxic effects, and establish a correlation with the ambient level of contamination,” Bernadette Pinel-Alloul explains. She authored a chapter on “Metallothionein – A biomarker of exposure to cadmium for freshwater invertebrates,” which appeared recently in the book Écotoxicologie moléculaire, published by Les Presses de l’université du Québec.

The toxic effects of cadmium on several species of bivalve had already been tested in the laboratory. They have yet to be assessed in the natural environment, which is the object of this study. This protein will make it possible to better estimate the toxic potential of a metallic contaminant, which is not possible by simply studying its accumulation in sediments.