Posted on 29 July 2004
Chemical pollution is threatening whales with extinction in parts of Canada and the Pacific Ocean, and is poisoning their food source in the Antarctic.
- Chemical pollution is threatening whales with extinction in parts of Canada and the Pacific Ocean, and is poisoning their food source in the Antarctic.
Beluga whales (Delphinapterus leucas
) in the St Lawrence River, Canada, have been dying of cancer, local scientists have found. The local population of belugas is estimated to be around 650 animals, but 14 or 15 of them are dying each year. When local veterinarians became concerned about the number of dead beluga whales that were being washed up, they decided to investigate. Between 1983 and 1999, Daniel Martineau and his team from Montreal University carried out autopsies on 100 of the dead whales
found on the shores of the river.
What they found shocked them: 27 per cent of adult and 17 per cent of juvenile belugas examined had died of cancer.
"In dolphins and terrestrial animals, the figure is closer to 2 per cent," said Dr Martineau(1). "The cancers found in Saint Lawrence belugas represent about 40 per cent of all cancers ever reported in cetaceans worldwide."
Most of the cancers were of the gastrointestinal tract (intestine or stomach), but there were also cancers of the mammary gland, skin, ovaries, and uterus.
The autopsies showed that the whales had been exposed to carcinogenic polycyclic aromatic hydrocarbons (PAHs). PAHs are persistent chemicals that do not break down easily in the environment and accumulate in the sediment of rivers and near shorelines. Beluga whales eat by diving deep down to the bottom of the river and feeding on the organisms living in this sediment, and the PAHs accumulate in their blubber.
There are approximately 70,000 beluga whales worldwide. Most live in the Arctic Ocean, but occasionally groups are found in rivers with cold water temperatures, like the St Lawrence River, where such a group has lived for the last 10,000 years.
The scientists also noticed that none of the females over 21 years old seemed capable of reproducing, while belugas living in the Arctic can produce calves until the end of their lives (i.e. between 35 to 50 years old). In addition, veterinary pathologist Sylvain DeGuise from Connecticut University found that in addition to the cancers in the St Lawrence Belugas, 36 per cent of the females had lesions (ie. abnormal tissue) in their mammary glands.
The researchers believe that an aluminium plant upstream, which is a source of chronic PAH pollution in the river, could be to blame as the incidence of human cancer in the area is also higher than for Canada as a whole and some of the cancers have been related to PAHs. In addition, river pollution is so severe that environmental officials have warned residents not to eat fish caught from the river more than once a month.
Killer whales also under threat
Killer whales (Orcinus orca
) in the Northeast Pacific Ocean are also being polluted and threatened by chemicals. Researchers reported that "a recent computer viability model suggests a high risk of extinction within 150 years unless habitat improvement measures are taken" and that "High levels of PCBs were cited as one reason for the listing of …killer whales as "endangered" and…communities as "threatened"".
Researchers Sierra Rayne and Dr Peter Ross carried out a study of the level of pollution by a number of chemicals, including polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs), and polychlorinated naphthalenes (PCNs), in the killer whales
which frequent the waters of the western coast of North America between Vancouver and Seattle. PBDEs are suspected of causing hormone disruption and damaging the immune system in the whales, while some PBBs are suspected of being carcinogenic and some PCNs are toxic. These whales are some of the most vulnerable wildlife to chemical pollution.
The team analysed the levels of the chemicals in three different whale groups in the region: northern residents; southern residents, and transients. The team found high concentrations of the PBDEs in male southern residents, and male and female northern residents. PBDE concentrations were much higher than those for PBBs and PCNs. The levels of PBDE concentration in these whales were 2–10 greater than in North Atlantic sperm whales and in the range of PBDE concentrations found in North Sea pilot whales, showing that persistent chemicals are accumulating in the coastal food chain off Washington State and British Columbia. Evidence suggests that PBDEs and related compounds may pose a serious risk to the whales’ health. Previous studies
have demonstrated that female killer whales significantly reduce their toxic burden by transferring persistent organic chemicals, such as PCBs, to their offspring, either via the placenta during pregnancy or in their fat rich milk during lactation".
The killer whale is the largest member of the dolphin family as the male can weigh up to 9,000kg and the female 5,000kg. It eats squid, fish, seals, and other aquatic animals, and its mouth is so wide that it can swallow a small seal whole.
It is also considered one of the most contaminated marine mammals in the world, and the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) has upgraded the southern residents of the northeastern Pacific killer whale populations to endangered, meaning that there is the threat of "imminent extinction". Transient and northern resident killer whale populations have been upgraded to the status "threatened". In both these cases this is because of the effects of persistent toxic chemicals and a reduction in suitable food sources(2).
Food source for Antarctic whales polluted by POPs
A third piece of recent research has revealed that whales (3) living in the Antarctic during the summer months are being contaminated by chemicals in krill, an important food source. Although the Antarctic is one of the most remote regions in the world, toxic chemicals are being carried through the atmosphere and marine currents to pollute the food chain and hence whales and other marine mammals.
A group of researchers from the Virginia Institute of Marine Science looked at the level of chemicals
found in both ice algae and phytoplankton being passed up the marine food chain. Chemicals travel thousands of miles to the Antarctic where they are accumulated by the SIMCO (Sea Ice Microbial Community) and phytoplankton. These are then eaten by zooplankton (tiny marine animals) including krill, small shrimp-like organisms, which are then consumed by whales.
The research team analysed the ice algae and found concentrations of hexachlorobenzene (HCB) and brominated diphenyl ethers (BDE-47, -99, and –100).
Dr Ross, who carried out the work on the killer whales in the Pacific, has described the whales as being "sentinels of a contaminated planet and indicators of global contamination". The level of chemicals present in these whales and their food sources indicate that measures need to be urgently taken to ensure the whales’ long-term survival and to reduce the threat of chemical pollution worldwide.For further information:
WWF DetoX Campaign
Tel: +32 2 743 8806
E-mail: firstname.lastname@example.org Notes
1. As quoted in New Scientist Online News 17:10 27 February 02
2. Report on Status of killer whales
, Robin Baird, submitted to COSEWIC
3. The types living in the Antarctic are: blue whale, fin whale, humpback whale, minke whale, right whale, bottenose whale and sperm whale.