The Davis Strait - DCE - Nationalt Center for Miljø og Energi

Seal pups are very sensitive to direct oiling, because they have not developed
an insulating blubber layer and are dependent on their natal fur for insulation
(Geraci & St. Aubin 1990). The hooded seal is particularly sensitive
in this respect because whelping patches are located within the assessment
area, on the eastern edge of the Davis Strait pack ice. For the polar bear, contact
with oil also means loss of the insulation properties of the fur. Polar
bears can pick up the oil when they swim between ice floes and may also
unavoidably ingest oil as part of the grooming behaviour; both can be lethal.
In the assessment area, however, the number of polar bears is low and their
occurrence is dependent on the presence of sea ice.
Marine mammals are forced to come to the surface to breathe. Therefore inhalation
of vapours from oil is a potential hazard to seals and cetaceans. AA
recent report indicates that the loss of killer whales after the Exxon Valdez
oil spill in 1989 was related to inhalation of oil vapours from the spill
(Matkin et al. 2008). These killer whales did not avoid the oil spill and were
observed surfacing in oil-covered water. Harbour seals found dead shortly
after the Exxon Valdez oil spill had evidence of brain lesions caused by oil
exposure, and many of these seals were disoriented and lethargic over a period
of time before they died (Spraker et al. 1994). In periods with icecoverage
where oil can fill the spaces between the ice floes, the risk of inhalation
of toxic vapour may be even more serious because marine mammals
are forced to surface in these ice-free spaces where the oil may be gathering.
There is also concern relating to damage to eye tissue on contact with oil as
well as for the toxic effects and injuries in the gastrointestinal tract if oil is
ingested during feeding at the surface (Albert 1981, Braithwaite et al. 1983,
St. Aubin 1990). Surface feeding whales such as the bowhead, minke, fin, sei,
blue and humpback whales are especially exposed to this threat. Furthermore,
baleen whales are at risk during even short exposures to oil because
they feed by filtering prey-laden water through their baleen plates. The effect
of fouling of baleen plates by oil and the long-term effects are uncertain,
but filtration may be seriously affected (Werth 2001).
Risk of long exposures, such as inhalation of oil vapours, ingestion and contact
with eye tissues, is aggravated because animals may not be able to perceive
oil as a danger and have repeatedly been reported to swim directly into
oil slicks (e.g., Harvey & Dalheim 1994, Smultea & Würsig 1995, Anon
2003a, Matkin et al. 2008).
As top predators, marine mammals have a risk of being affected through
toxic substances accumulating in the food chain. Walrus is especially sensitive
because they feed on bivalves buried in the seabed in shallow waters
where toxic concentrations of oil can reach the seafloor. Bearded seals are also
vulnerable, as their diet includes benthic organisms such as polychaetes,
bivalves and sea cucumbers.
Marine mammals species affected by an oil spill during winter in the assessment
area could include bearded seal, hooded seal, ringed seal, harbour
seal, bowhead whale, narwhal, white whale, polar bear, harbour porpoise
and occasionally also walrus, bottlenose whale and sperm whale. Harbour
seals are especially vulnerable because they are endangered in Greenland
and conservation of the remnant populations still existing in the assessment
area is crucial for the recovery of the population. As previously mentioned,
the hooded seal is also highly vulnerable due to whelping patches on the
219