Chemical pollution and St. Lawrence beluga whales 

• The beluga of the St. Lawrence: An ongoing investigation
• If the River is cleaner, are the belugas healthier?

The beluga of the St. Lawrence: An ongoing investigation

For 20 years, the beluga of the St. Lawrence has regularly been front-page news. Behind the grim headlines, serious scientific investigation is being carried out, begun in 1982 following the discovery of a beached whale near Rimouski. Pierre BÈland1, then a researcher at the Fisheries Ecology Research Centre, and Daniel Martineau2, who was working as a veterinarian with Agriculture Canada at the time, set out to determine cause of death. Tissue analysis revealed many toxic contaminants including organochlorines, such as PCBs and mirex, found in unprecedented concentrations in the whale’s fatty tissue. Initial necropsies revealed problems in the beluga’s reproductive system and an alarming number of tumours.

These discoveries were particularly disquieting since it was feared that the effects of pollution would slow down or prevent the recovery of a population that had been severely threatened by past human activity. In fact, commercial hunting, interrupted in the mid-1950s, had already greatly reduced its numbers. Based on surveys carried out by Leone Pippard, a journalist turned researcher, and then by Dave Sergeant of Fisheries and Oceans Canada, the population was estimated to be 500 in the early 1980s, a mere 10 % of what it was at the turn of the century. In 1983, the St. Lawrence belugas were given endangered population status.

By 1998, their endangered status remained and, over 16 years after the investigation first began, there is still a cloud of uncertainty surrounding the belugas’ recovery. Sylvain DeGuise, Michel Fournier and several other researchers have gone on to work with Pierre BÈland and Daniel Martineau, providing impressive data which suggests that pollution in the St. Lawrence affects both the immune and reproductive systems of belugas. Necropsies were performed on a total of 73 beluga carcasses between 1982 and 1996; 29 of these had tumours, of which 14 were cancerous. According to Martineau, the high incidence of tumours in St. Lawrence belugas can be attributed to the presence of powerful carcinogenic agents in their environment. At the outset of the investigation, benzo[a]pyrene (BaP), resulting from the incomplete combustion of organic matter, was identified as one of the harmful substances in question. DNA analyses performed on belugas revealed exposure to this substance. However, the variety of tumours observed suggests the probable existence of more than a single harmful agent.

Research conducted by Pierre BÈland and his team has revealed the extent of contamination of the St. Lawrence River’s marine food web. Despite progress in scientific methodology, the ability to relate cause and effect in complex natural systems is limited. In some ways, the many diseases suffered by the belugas can be considered "circumstantial evidence". This evidence is, nonetheless, overwhelming.

If the river is cleaner, are the belugas healthier?

Pierre Béland, SLNIE

Toxic man-made chemicals have not always been present in the natural environment. Most were introduced after the 1930s, and some, like DDT, have now been banned in Canada and the United States for more than 20 years. It should therefore be expected that their concentrations in the tissues of belugas will change over time.

The most recent chemical analyses of beluga tissues were done on samples from animals that died in 1994. A comparison with other data collected since 1982 shows that the average levels of DDT and PCBs have decreased since 1988 in males only. No trend was seen in females nor in either sex for any of the other organochlorine chemicals (such as toxaphene, hexachlorobenzene, chlordane and others).

A decrease in DDT and PCBs was also observed in eels, marine birds and harp seals in the Estuary and the Gulf of St. Lawrence during the same period. The earliest data on harp seals date back to the 1970s. If we assume that decontamination in belugas proceeded at the same rate as in the seals, a projection into the past suggests that belugas in the 1970s would have been at least twice as contaminated as the very high levels that we observed when we first examined carcasses in 1982-83! This estimate is consistent with our hypothesis that toxic chemicals had a major impact on the beluga population as industrialization and agricultural pesticide use increased after the 1930s. As we now know, pollution of the Great Lakes basin was then progressing, peaking in fish and birds around the late 1970s.

Necropsies on belugas that were found dead over the last five years (1994-98) revealed the same lesions as those carried out from 1982 to 1993. There is therefore no sign of improving health for belugas. It is plausible that the combined effects of the various chemicals present in the whales would be felt at concentrations even lower than those presently observed. If this is so, decontamination of the Great Lakes and St. Lawrence basin will have to proceed much further before we can claim victory for the beluga.