The state of the St. Lawrence

Over the past two centuries the St. Lawrence has been subjected to degradation associated with industrial activity, agriculture, urbanization and shipping traffic. Climate change, already observable, is adding another factor to the equation. The subject of the state of the St. Lawrence is complex. Analysis must be carried out with caution; research is still underway.

Pollution and oxygen decreasing oxygen levels

The decline in oxygen levels began with waste from the timber industry in the XIX Century and continued with pulp mill runoff, which also included contaminants such as mercury salts and chlorine. The trend has increased since the 1970s. Yet, oxygen saturation levels are uneven from one area to the next. With average levels of between 40 and 60 percent, levels measured off Les Escoumins are very low at 20 percent, while the head of the Laurentian Channel is well oxygenated.

Other industries, notably in the aluminum and agriculture sectors, have dumped heavy metals such as lead, mercury and cadmium, along with organic molecules such as PAHs, DDT, PCBs and Mirex (a pesticide), into the aquatic environment. TBT is a toxic anti-fouling paint that is banned in most countries for boats under 25 m in length, is still present on the hulls of many commercial vessels.

Although the dumping of toxic chemicals has ceased or been significantly reduced, chemicals remain in the system. They settled to the bottom and were eventually integrated into the sediment. In spite of this, they are regularly stirred up by the natural mixing caused by water movement or by the dredging operations required for the maintenance and development of the St. Lawrence Seaway. Meanwhile, new contaminants are still coming onto the scene. Organobromines, for example, are used in the textile industry as fireproofing agents. While little is known about their effects on the environment, we do know that they are very persistent.

Municipal sewage and wastewater from boats also represent a source of pollution. On both shores of the River the quality of sewage treatment facilities is extremely variable, and occasionally very basic. All of these problems are complex, regulations are evolving and application of regulations takes time.

A changing climate

Global warming of the planet's atmosphere and modifications in planetary ocean currents are influencing St. Lawrence water masses. They are responsible for changes observed in salinity, temperature, freshwater flow, ice cover, the structure of the major water layers and how they flow. Researchers are attempting to understand how the various life forms present in the St. Lawrence are reacting.

The impact of environmental changes on certain species

The story that most frequently comes to mind when we think about pollution in the St. Lawrence is that of the beluga whale. Everything began near Rimouski in 1982 around a beached beluga whale. Pierre Béland, then a researcher at the Centre en écologie des pêches and Daniel Martineau, who was at the time a veterinarian working for Agriculture Canada, wanted to know what the animal had died of. A beluga whale carcass recovery programme was launched. The programme continues to this day under the supervision of Fisheries and Oceans Canada. Tissue analysis has allowed researchers to identify numerous toxic contaminants that are present in record levels in the blubber of these animals. The first necropsies , revealed problems with the reproductive system and disturbingly high numbers of tumours.

The good news is that this scientific enquiry galvanized efforts for the decontamination of the St. Lawrence. Considerable effort was agreed upon to reduce toxic effluent in the Great Lakes, the St. Lawrence and its tributaries through programmes such as the St. Lawrence Action Plan, Vision 2000. These programmes have shown positive results. There has been a drop in DDT and PCB levels in eels, seabirds and harp seals in the St. Lawrence Gulf and Estuary, for example.

Unfortunately, the beluga whale is still stuck with disturbing concentrations of various contaminants. The inertia is due in part to its long lifespan and the fact that mothers contaminate their young during gestation and throughout the nursing period. Even today, nearly one beluga whale in four dies of cancer.

Climate change, for its part, could explain major changes at the bottom of the food chain. The timeline measured by Michel Harvey of the Maurice Lamontagne Institute (Fisheries and Oceans Canada) suggests a 70 percent decline in macro zooplankton in the St. Lawrence Gulf and Estuary between 1994 and 2003. Furthermore, while krill made up 80 percent of all macro zooplankton in 1994, it represented only 40 percent in 2003. At the same time, a new species has arrived in great profusion in the St. Lawrence since the early 1990s. This species is a cold-water, Arctic amphipod named Themisto libellula. Its presence has not gone unnoticed: between 1994 and 2003 it represented 2 percent and 45 percent of the biomass respectively. It is possible that these changes in the communities of the St. Lawrence ecosystem, which are a major food source for whales, may have long-term effects on these giants.

Chemical pollution and climate change add to the negative impacts of other human activities such as shipping traffic (noise pollution, increased risk of collisions, dredging) or fishing (over fishing, destructive practices). Will the St. Lawrence and its inhabitants be able to accommodate this human presence? We must learn to be more discreet in this fragile environment if we wish to take advantage of its generosity in the future.

[Special thanks to Nadia Ménard, biologist at the Saguenay-St. Lawrence Marine Park]