The Environment and Commercial Navigation on the St. Lawrence

The development of marine transport on the St. Lawrence River has necessitated the construction of a set of infrastructures for the transshipment of goods. The surface area occupied by the main commercial ports located on the shores of the St. Lawrence acts as a source of pressure on the natural environment. The effects of the development of port areas on both the St. Lawrence environment and on use of the river translate into the loss of natural environments, reduced biodiversity and shore inaccessibility.

Eight sources of pressure have been identified:

VariablesAffected areasState
Shipping infrastructuresEntire St. Lawrence system

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.

Intensity of activitiesEntire St. Lawrence system

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.

DredgingEntire St. Lawrence system

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.

SpillsEntire St. Lawrence system

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.

Wave actionFluvial section

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.

Ballast flushingEntire St. Lawrence system

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.

OrganotinsEntire St. Lawrence system

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.

WasteEntire St. Lawrence system

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.


Sustainable Navigation Strategy for the St. Lawrence

Published in 2004 under the St. Lawrence Vision 2000 Action Plan (SLV 2000),the Sustainable Navigation Strategy for the St. Lawrence  is aimed at reconciling the protection of St. Lawrence ecosystems and water resources with the needs of users and the development of the shipping industry. The strategy focuses particularly on the integrated management of dredging activities and dredged material, the management of contaminated sites, shore erosion, ballast-water discharge, and the environmental risks associated with accidental spills.


Villeneuve, S. 2001. Les répercussions environnementales de la navigation commerciale. Le Naturaliste canadien 125(2): 49–67.

Villeneuve, S. and L. Quilliam. 2000. The Environmental Risks and Impacts of Navigation on the St. Lawrence River. Scientific and Technical Report ST-188E. Environment Canada – Quebec Region, Environmental Conservation, St. Lawrence Centre. 153 pages.

Related Link

St. Lawrence Vision 2000 – Sustainable Navigation Strategy for the St. Lawrence

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