The Environment and Commercial Navigation on the St. Lawrence

Loss or deterioration of riparian habitats and of biodiversity.

Modification of hydrodynamics.

Activities likely to pollute the environment (organic and inorganic contaminants).

Loss of use.

Potential disturbance of aquatic fauna (little data) and bird life, particularly in the fluvial lakes, and marine mammals in the Upper Estuary and Lower Estuary.

Resuspension of sediments in shallow areas could lead to the recirculation of contaminants.

Modification of hydrodynamics.

Loss of habitat at dredging sites and deposition of dredged spoil.

Increase in turbidity and suspended matter.

Recirculation of pollutants.

Massive modification of habitats due to Seaway: Beauharnois and La Prairie Basin.

Modification of habitats following dredging of Port of Quebec City, which changed the profile of the north shore.

From 1945 to 1988, modification of 12 600 ha of habitat, mostly in the fluvial stretch (48%) and Fluvial Estuary (40%).

Unknown losses of biomass and animal and plant species.

The environmental impacts vary depending on the nature of the product and the volume spilled, the time of year, spill location and frequency, etc.

Little data is available with which to assess the scope and the extent of the effects of a spill on biota.

55% of the 1532 km of shoreline in the fluvial stretch remains in its natural state and is found primarily downstream of Repentigny.

The shores are eroding over an area of close to 400 km in size, including 300 km on the islands.

The archipelagos of Contrecoeur and Sorel are the most affected.

20 km of the eroded shores are less than 610 m from the centre of the shipping channel, including 10 km located less than 305 m away.

Shores can retreat by up to 3 m annually.

Losses of waterfowl habitat are heavy.

The first species were introduced into the Great Lakes–St. Lawrence basin in 1810.

To date, 163 species have been introduced into the Great Lakes–St. Lawrence basin, including 85 species observed in the St. Lawrence.

Only the zebra mussel has invaded the fluvial section (and the Richelieu and Ottawa rivers).

Estimated densities in the St. Lawrence are well below those of the Great Lakes and other waterways.

It is not possible to make any determinations about the indigenous nature of some species of dinoflagellates due to an absence of historical data.

Very fragmented data on concentrations of TBT in water and sediments in the fluvial section.

The concentrations measured in water and sediments in the St. Lawrence are low relative to levels detected in large Canadian harbours, but little data is available.

TBT concentration in water from the Quebec City harbour reached the interim criteria for the protection of freshwater aquatic organisms.

There are no existing criteria relative to TBT for sediment quality.

The toxicity of organotins increases with increased salinity.

Molluscs (gastropods and bivalves) are most vulnerable to TBT toxicity.

Low concentrations of butyltins measured in blue mussels and in some starfish in the estuary and gulf indicate ubiquitous, low intensity contamination.

No study on aquatic waste has yet been conducted in the study area.

A study carried out off the coast of Newfoundland reveals that between 20 000 and 100 000 seabirds die each year due to illegal dumping of waste oil by passing ships.

Plastic debris may lead to the strangulation or entanglement of aquatic organisms.