Federal Register, Volume 76, Number 149, August 3, 2011, Pages 46595-47054 Page: 47,030
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47030 Federal Register/Vol. 76, No. 149/Wednesday, August 3, 2011 /Rules and Regulations
two of three bears died in the Canadian
experiment, and it was suspected that
the ingestion of oil was a contributing
factor to the deaths. Experimentally
oiled bears ingested much oil through
grooming. Much of it was eliminated by
vomiting and in the feces; some was
absorbed and later found in body fluids
and tissues.
Ingestion of sublethal amounts of oil
can have various physiological effects
on a polar bear, depending on whether
the animal is able to excrete or detoxify
the hydrocarbons. Petroleum
hydrocarbons irritate or destroy
epithelial cells lining the stomach and
intestine, thereby affecting motility,
digestion, and absorption.
Polar bears swimming in, or walking
adjacent to, an oil spill could inhale
petroleum vapors. Vapor inhalation by
polar bears could result in damage to
various systems, such as the respiratory
and the central nervous systems,
depending on the amount of exposure.
Oil may also affect food sources of
polar bears. Seals that die as a result of
an oil spill could be scavenged by polar
bears. Consumption of contaminated
carcasses would increase exposure of
the bears to hydrocarbons and could
result in death or reduced survival of
individual bears. A local reduction in
ringed seal numbers as a result of direct
or indirect effects of oil could
temporarily affect the local distribution
of polar bears. A reduction in the
density of seals as a direct result of
mortality from contact with spilled oil
could result in polar bears not using a
particular area for hunting. Possible
impacts from the loss of a food source
include reduced recruitment and/or
survival.
Spilled oil also can concentrate and
accumulate in leads and openings that
occur during spring break-up and
autumn freeze-up periods. Such
concentrations of spilled oil increase the
chance that polar bears and their
principal prey would be oiled. To access
ringed and bearded seals, polar bears in
the SBS concentrate in shallow waters
less that 300 m (984 ft) deep over the
continental shelf and in areas with
greater than 50 percent ice cover
(Durner et al. 2004).
Due to their seasonal use of nearshore
habitat, the times of greatest impact
from an oil spill on polar bears are
likely the open-water and broken-ice
periods (summer and fall). Distributions
of polar bears are not uniform through
time. Nearshore and offshore polar bear
densities are greatest in fall, and polar
bear use of coastal areas during the fall
open-water period has increased in
recent years in the Beaufort Sea. Thiscorrelated with the distance to the pack
ice at that time of year (i.e., the farther
from shore the leading edge of the pack
ice is, the more bears are observed
onshore). An analysis of data collected
2001-2005 during the fall open-water
period concluded: (1) On average
approximately 4 percent of the
estimated 1,526 polar bears in the
Southern Beaufort population were
observed onshore in the fall; (2) 80
percent of bears onshore occurred
within 15 km (9.3 mi) of subsistence-
harvested bowhead whale carcasses,
where large congregations of polar bears
have been observed feeding; and (3) sea-
ice conditions affected the number of
bears on land and the duration of time
they spent there (Schliebe et al. 2006).
Hence, bears concentrated in areas
where beach-cast marine mammal
carcasses occur during the fall would
likely be more susceptible to oiling.
The persistence of toxic subsurface oil
and chronic exposures, even at
sublethal levels, can have long-term
effects on wildlife (Peterson et al. 2003).
Although it may be true that small
numbers of bears may be affected by an
oil spill initially, the long-term impact
could be much greater. Long-term oil
effects could be substantial through
interactions between natural
environmental stressors and the
compromised health of exposed
animals, and through chronic, toxic
exposure as a result of bioaccumulation.
Polar bears are biological sinks for
pollutants because they are the apical
predator of the Arctic ecosystem and are
also opportunistic scavengers of other
marine mammals. Additionally, their
diet is composed mostly of high-fat
sealskin and blubber (Norstrom et al.
1988). The highest concentrations of
persistent organic pollutants in Arctic
marine mammals have been found in
polar bears and seal-eating walruses
near Svalbard (Norstrom et al. 1988,
Andersen et al. 2001, Muir et al. 1999).
As such, polar bears would be
susceptible to the effects of
bioaccumulation of contaminants
associated with spilled oil, which could
affect the bears' reproduction, survival,
and immune systems. Sublethal,
chronic effects of any oil spill may
further suppress the recovery of polar
bear populations due to reduced fitness
of surviving animals.
Subadult polar bears are more
vulnerable than adults to environmental
effects (Taylor et al. 1987). Subadult
polar bears would be most prone to the
lethal and sublethal effects of an oil
spill due to their proclivity for
scavenging (thus increased exposure to
oiled marine mammals) and theirinexperience in hunting. Because of the
greater maternal investment a weaned
subadult represents, reduced survival
rates of subadult polar bears have a
greater impact on population growth
rate and sustainable harvest than
reduced litter production rates (Taylor
et al. 1987).
To date, large oil spills from Industry
activities in the Beaufort Sea and coastal
regions that would impact polar bears
have not occurred, although the interest
in, and the development of, offshore
hydrocarbon reservoirs has increased
the potential for large offshore oil spills.
With limited background information
available regarding oil spills in the
Arctic environment, the outcome of
such a spill is uncertain. For example,
in the event of a large spill (e.g., 5,900
barrels (equal to a rupture in the
Northstar pipeline and a complete drain
of the subsea portion of the pipeline),
oil would be influenced by seasonal
weather and sea conditions, including
temperature, winds, wave action, and
currents. Weather and sea conditions
also affect the type of equipment needed
for spill response and the effectiveness
of spill cleanup. Based on the
experiences of cleanup efforts following
the Exxon Valdez oil spill, where
logistical support was readily available,
spill response may be largely
unsuccessful in open-water conditions.
Indeed, spill response drills have been
unsuccessful in the cleanup of oil in
broken-ice conditions.
The major concern regarding large oil
spills is the impact a spill would have
on the survival and recruitment of the
SBS polar bear population. Currently,
this bear population is approximately
1,500 bears. The maximum sustainable
subsistence harvest is now 70 bears for
this population (divided between
Canada and Alaska). The population
may be able to sustain the additional
mortality caused by a large oil spill if a
small number of bears are killed;
however, the effect of numerous bear
deaths due to the direct or indirect
effects from a large oil spill would be
additive to the effect of the subsistence
harvest, likely resulting in reduced
population recruitment and survival.
Indirect effects may occur through a
local reduction in seal productivity or
the scavenging of oiled seal carcasses, or
through other potential impacts, both
natural and human-induced. The
removal of a large number of bears from
the population would exceed
sustainable levels, potentially causing a
decline in the bear population and
affecting bear productivity and
subsistence use.
Evaluation of the potential impacts of
Industry waste products and oil spillschange in distribution has been
suggests that individual bears could be
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United States. Office of the Federal Register. Federal Register, Volume 76, Number 149, August 3, 2011, Pages 46595-47054, periodical, August 3, 2011; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc52326/m1/441/?rotate=270: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.