Develop a toxicity test to assess the sediments in the brackish water zone of the St. Lawrence

Context and project description

To assess the toxicity of dredged or deposited sediments in different sections of the St. Lawrence, we use tests that verify the effects of toxic products on various organisms or micro-organisms that are present in the sediments. Furthermore, in the freshwater zone, the assessment of ecotoxicological risks of sediments is in part based on the results of two types of tests: the mortality and growth of a diptrous insect whose larvae develop in the sediment (Chironomus riparius) and those of a small amphipod crustacean that lives at the bottom of waterways (Hyalella azteca).

Scientists at the St. Lawrence Action Plan now want to determine which toxicity tests should be used to evaluate the potential impact of dredged or deposited sediments in the river’s brackish water zone – that is, downstream from Île d’Orléans. Presently, Environment and Climate Change Canada's Disposal At Sea program requires three types of tests for estuary and marine zones: a bioluminescence inhibitor for a species of luminous bacteria (Photobacterium phosphoreum), fertilization among sea urchins and mortality rate for an amphipod species.

Results

Two amphipod (small crustacean) species, Hyallela azteca and Eohaustorius estuarius, were selected for the toxicity research in this project. To evaluate the tolerance of these species to various levels of salinity, they were exposed to uncontaminated natural sediments, for which the salinity conditions were varied, from low salinity to a salinity level similar to that of seawater (from 0.5 to 30‰).
The results show that Hyallela azteca can be used for toxicity testing when the salinity ranges from 0.5 to 15‰, whereas the other amphipod, Eohaustorius estuarius, can be used in all the tested salinity conditions. A fact sheet presenting the main results of this project along with recommendations for assessing toxicity in the brackish water zone has been prepared.

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