To determine if bearded seals (
Kivalina, Alaska, USA is a village of approximately
375 people located 129 km from the city of Kotzebue in northwestern Alaska on
the coast of the Chukchi Sea (Figure
Harvest locations for bearded seals sampled for trace element concentrations.
However, marine mammals, especially bearded seals (
The purpose of this study was to determine if bearded seals harvested in the vicinity of the mine were as safe to eat as bearded seals from other locations in Alaska. We compared trace element concentrations in bearded seals harvested by Kivalina hunters near the Red Dog Mine (RDM) port site with bearded seals harvested where no mining was occurring. We did not attempt to determine if mine-related activities were contaminating seals. Because there was no systematic monitoring program in place for contaminants in this area, we used a retrospective approach and compared the bearded seals harvested by Kivalina hunters near the RDM in 2005 with bearded seals harvested near Little Diomede and Hooper Bay, Alaska, in 2003–2005, where no mining was occurring.
Bearded seal teeth and liver tissue were contributed by
hunters from Kivalina, Alaska (see Figure
Liver tissues were frozen in Ziploc bags and transported to
ADF&G in Fairbanks. Tissues were then subsampled under clean
conditions using titanium knives on a Teflon covered surface [
Liver samples were
first homogenized with a meat grinder. An aliquot of approximately 100 g was
weighed and freeze-dried and then further homogenized using a blender prior to
extraction. Percent moisture was calculated by comparing the weight of the wet
sample with the weight of the dry samples before a 0.5 g sample was extracted and
digested in a microwave wet ash procedure using H2O2 and
HCl. Percent moisture was used to convert dry weight to wet weight and all results
are presented in
Samples analyzed for As and Se were digested using magnesium dry ash digestion methods. This method uses methanol, HNO3, HCl, and heat for digestion. After digestion, As and Se were analyzed using hydride generation AA. Pb was analyzed using graphite furnace AA. For total mercury, a 10 mL aliquot was removed immediately after dilution, HCl was added, and concentrations were determined using cold vapor AA. All other elements were analyzed using ICP on a Perkin Elmer 4300 DV.
Quality assurance included the analysis of procedural blanks, duplicate samples, and spiked samples run with each group of 10 samples. Instruments were also calibrated after every 10 samples. If quality standards were not met samples were rerun. Standard reference materials (SRM) provided by the National Institute of Standards and Technology (NIST 1566b, oyster tissue) and the National Research Council, Canada (NRCC DOLT-3, dogfish liver) were used. The data were accepted if the SRM reported value was within 2 standard deviations of the certified mean of the SRM. LET Laboratories participates in annual interlaboratory trials to maintain quality assurance and comparability with other participating laboratories.
Lower jaws were submerged in hot water for 30 minutes and a
canine tooth was extracted and placed in a paper envelope. Teeth were sent
to Matson’s Laboratory in Milltown, MT, USA for slide preparation. Teeth were sectioned (14
To compare RDM to sites without possible mine
contamination, we pooled samples from Little Diomede and Hooper Bay
and treated them as a reference group. For concentrations below the detection
limit, we followed the standard practice of assigning one half the detection
limit for calculating statistics such as means (e.g., [
Our data presented
two obstacles for analysis. First, our sample sizes were small, making the
assumptions required by parametric tests difficult to assess. Second, because
concentrations of some elements are known to covary with age [
We obtained liver samples from 24
bearded seals, nine from RDM, and 15 from reference sites (nine from Little
Diomede and six from Hooper Bay). Five seals from RDM and 12 from reference
sites were aged. Seals ranged from <1
to 23 years old; seals sampled near RDM averaged 11.2 years of age and
seals sampled at reference sites averaged 7.1 years of age. Of 19 elements
analyzed, eight (Al, B, Ba, Be, Cr, Mo, Ni, Pb) were detected in fewer than 50%
of samples, from both RDM and reference sites and eight others (Cu, Fe, Hg, Mg,
Mn, Se, Sr, Zn) were detected in all
samples from all sites (Tables
Trace element concentrations (
Element | Site | Arithmetic mean | Geometric mean | Arithmetic SD | Range |
---|---|---|---|---|---|
( | ( | ||||
Al | RDM | 1.10 | 1.03 | 0.46 | 0.84–1.91 |
reference | 0.61 | 0.50 | 0.45 | 0.29–1.72 | |
RDM | 0.58 | 0.52 | 0.28 | 0.22–1.15 | |
reference | 0.41 | 0.31 | 0.32 | 0.04–1.13 | |
B | RDM | 0.28 | 0.28 | 0.01 | 0.27–0.3 |
reference | 0.36 | 0.34 | 0.17 | 0.28–0.89 | |
Ba | RDM | 0.09 | 0.08 | 0.07 | 0.07–0.29 |
reference | 0.03 | 0.03 | 0.00 | 0.03–0.03 | |
Be | RDM | 0.01 | 0.01 | 0.00 | 0.01–0.01 |
reference | 0.01 | 0.01 | 0.00 | 0.01–0.02 | |
Cd | RDM | 5.24 | 4.25 | 2.99 | 0.97–10.59 |
reference | 7.12 | 0.94 | 11.16 | 0.01–39.93 | |
Cr | RDM | 0.07 | 0.07 | 0.00 | 0.07–0.07 |
reference | 0.13 | 0.07 | 0.19 | 0.01–0.77 | |
RDM | 40.71 | 38.72 | 13.80 | 19.84–70.74 | |
reference | 24.65 | 21.82 | 12.12 | 7.8–42.78 | |
Fe | RDM | 598.40 | 589.44 | 108.23 | 421.5–781.44 |
reference | 620.09 | 575.16 | 238.49 | 272.91–1078.68 | |
RDM | 3.23 | 3.08 | 1.05 | 1.92–5.22 | |
reference | 3.93 | 1.25 | 7.28 | 0.13–28.31 | |
Mg | RDM | 185.36 | 184.80 | 15.58 | 168.02–216.75 |
reference | 183.76 | 182.62 | 20.09 | 127.88–218.73 | |
Mn | RDM | 5.09 | 5.02 | 0.84 | 3.52–6.29 |
reference | 4.51 | 4.36 | 1.25 | 2.67–6.78 | |
Mo | RDM | 0.35 | 0.33 | 0.13 | 0.27–0.58 |
reference | 0.34 | 0.33 | 0.10 | 0.28–0.61 | |
Ni | RDM | 0.08 | 0.08 | 0.02 | 0.07–0.14 |
reference | 0.07 | 0.06 | 0.02 | 0.03–0.08 | |
Pb | RDM | 0.03 | 0.03 | 0.00 | 0.03–0.03 |
reference | 0.04 | 0.04 | 0.02 | 0.03–0.09 | |
RDM | 4.79 | 4.68 | 1.10 | 3.4–6.5 | |
reference | 4.35 | 3.19 | 4.58 | 1.29–18.48 | |
Sr | RDM | 0.21 | 0.18 | 0.14 | 0.12–0.57 |
reference | 0.28 | 0.21 | 0.34 | 0.09–1.47 | |
V | RDM | 0.70 | 0.41 | 0.88 | 0.07–2.9 |
reference | 0.29 | 0.18 | 0.30 | 0.07–1.01 | |
Zn | RDM | 62.45 | 62.26 | 5.09 | 54.91–68.85 |
reference | 62.85 | 59.19 | 23.07 | 30.83–115.19 |
Statistical comparisons of trace element concentrations in bearded seal liver tissue between Red Dog Mine port site (RDM) and reference sites. No statistical tests were conducted when trace elements were detected in less than 50% of samples. ANCOVA was used to control for possible age effects when the nonparametric Mann-Whitney test identified differences in trace metals concentrations between RDM and reference samples. Trace elements detected in more than 50% of samples that Mann-Whitney tests identified as statistically different between RDM and reference sites are in bold.
Minimum detection limit | Proportion of samples above detection limit | ||||||
---|---|---|---|---|---|---|---|
Element | ( | RDM ( | Reference sites ( | Above threshold for statistical analyses? | Mann-Whitney | Significant age effect? | ANCOVA |
Al | 1.78 | 0.22 | 0.33 | No | |||
— | |||||||
B | 0.62 | 0.00 | 0.08 | No | |||
Ba | 0.15 | 0.11 | 0.04 | No | |||
Be | 0.03 | 0.00 | 0.00 | No | |||
Cd | 0.03 | 1.00 | 0.88 | Yes | .24 | Yes | .53 |
Cr | 0.16 | 0.00 | 0.13 | No | |||
— | |||||||
Fe | 0.89 | 1.00 | 1.00 | Yes | .5 | No | — |
0.3 | 1.00 | 1.00 | Yes | ||||
Mg | 1.39 | 1.00 | 1.00 | Yes | .43 | No | — |
Mn | 0.16 | 1.00 | 1.00 | Yes | .1 | Yes | .28 |
Mo | 0.62 | 0.22 | 0.17 | No | |||
Ni | 0.16 | 0.11 | 0.04 | No | |||
Pb | 0.09 | 0.00 | 0.04 | No | |||
1.19 | 1.00 | 1.00 | Yes | ||||
Sr | 0.06 | 1.00 | 1.00 | Yes | .46 | No | |
V | 0.16 | 0.89 | 0.63 | Yes | .06 | Yes | .06 |
Zn | 0.16 | 1.00 | 1.00 | Yes | .28 | No |
Mining-related contamination has been found in marine
mammal tissues. Lead and zinc mines in Arctic regions have contaminated local
marine environments in both West Greenland [
Although such
concerns are justified, it is unclear whether
high contaminant concentrations would be transferred to bearded seals even if
they were present because they may not spend much time feeding there. For
example, ringed seals that were believed to feed near the Nanisivik Mine on
Baffin Island, Canada were found to have elevated levels of Mg, Pb, and Cd [
We do not know how much time bearded seals
spend feeding near RDM, but available information indicates that bearded
seals may be highly mobile. During the fall seasons of 2004–2006, 26 bearded
seal pups were captured and fitted with satellite transmitters near Kotzebue [
We found little evidence that the concentrations of
trace elements were elevated in the liver tissue of bearded seals sampled near RDM
compared to our reference sites. Concentrations of Cd, Pb, and Zn in liver
tissue from RDM were not statistically greater than what was observed at reference
sites (Table
Arsenic is found widely in marine and freshwater
environments and has both natural (volcanic) and anthropogenic (industrial and
agricultural) sources [
Concentration of As does not increase with trophic level
and lower level consumers have the highest concentrations, suggesting that As
does not biomagnify [
Most trace elements are found in the highest concentrations
in organ tissues; however, organic As has been found at higher levels in seal
blubber [
We also found elevated concentrations of Cu in seal liver
near RDM compared to reference sites (Tables
Comparisons of element concentrations in
liver of bearded seals between this and other studies. Concentration units are
Element | Location | Year | Liver mean (SD) | Mean age (yrs) | Reference | |
---|---|---|---|---|---|---|
As | Nome, Alaska | 1989–1993 | 0.161–0.577(1) | 3 | — | [ |
Cd | Nome, Alaska | 1989–1993 | 0.99–2.00(1) | 3 | — | [ |
Pt. Barrow, Alaska | 1998–2001 | 8.66 (7.03) | 38 | — | [ | |
Cu | Nome, Alaska | 1989–1993 | 6.82–34.44(1) | 3 | — | [ |
Pt. Barrow, Alaska | 1998–2001 | 22.69 (7.99) | 38 | — | [ | |
Hg | Holman, western Canada | 1973 | 143.00 (170.00) | 6 | 8.5 | [ |
Belcher island, eastern Canada | 1974 | 26.18 (26.13) | 56 | 4.9 | [ | |
Alaska | — | 1.91 (1.20) | 4 | — | [ | |
Nome, Alaska | 1989–1993 | 1.4–9.4(1) | 3 | — | [ | |
Pt. Barrow, Alaska | 1998–2001 | 3.84 (3.55) | 34 | — | [ | |
Pb | Nome, Alaska | 1989–1993 | 0.03 | 1 | — | [ |
Se | Holman, western Canada | 1973 | 34.42 (33.23) | 6 | 8.5 | [ |
Belcher Island, eastern Canada | 1974 | 20.83 (13.47) | 10 | 4.9 | [ | |
Nome, Alaska | 1989–1993 | 0.43–5.3(1) | 3 | — | [ | |
Pt. Barrow, Alaska | 1998–2001 | 5.27 (3.51) | 38 | — | [ | |
V | Norton Sound, Alaska | 1989–1993 | 0.15–1.04(1) | 3 | — | [ |
Zn | Nome, Alaska | 1989–1993 | 32.60–103.70(1) | 3 | — | [ |
Pt. Barrow, Alaska | 1998–2001 | 57.48 (10.37) | 38 | — | [ | |
(1)Range provided instead of a mean and standard deviation.
(2)All samples below the detection limit.
Of the elements that did not differ in concentration
between RDM and reference sites (Cd, Hg, Se, Zn, and V), Hg and Se
concentrations are comparable to concentrations found in similar tissues from
other locations in Alaska and are lower than concentrations found in Arctic
Canada (Table
The overall variability in concentrations of trace elements
was generally higher in the reference sample than the RDM sample. Of the
elements suitable for statistical tests (i.e., the element was detected in >50% of the samples), the standard deviation of element concentration was higher
in the reference sample than the RDM sample in 9 of 10 cases (Table
Most studies
indicate that the concentration of some elements change with animal age (e.g.,
see reviews in [
In conclusion, we examined the concentrations of 19 trace elements in the liver tissues of bearded seals harvested near RDM and reference sites. Only As and Cu were found to be elevated near RDM. However, neither of these elements is known to be toxic in the chemical form or at the concentrations found. In addition, the concentrations of As and Cu found near RDM although significantly higher than our reference samples, they were not higher than concentrations found elsewhere in Alaska or Canada. Because we found that concentrations of trace elements in bearded seal liver near RDM were not higher than elsewhere, we conclude that muscle tissue, which is more commonly eaten but has much lower concentrations, would also not be higher. Therefore, we found no evidence that bearded seals harvested by hunters near RDM were less safe to eat or that trace element concentrations were greater than those found in bearded seals harvested elsewhere in Alaska or Canada.
This study would not have been possible without the samples provided by hunters from Kivalina, Diomede, and Hooper Bay. G. Sheffield and A. Simon assisted in the collection and shipping of samples from Diomede and Hooper Bay, respectively. J. Norton and A. Swann were helpful in coordinating sample collection in Kivalina. L. Hughes handled the samples once they reached Fairbanks and assisted in the clean sampling for laboratory analysis. C. Eckert and J. Kulas of Teck Cominco Alaska Inc. assisted with logistics and sampling at Kivalina. G. Pickert provided housing at the school in Kivalina. K. Frost, A. Whiting, and M. Cameron provided information on movements of bearded seal pups. S. Shock and M. Gerry of Exponent Inc. reviewed the manuscript. Three anonymous reviewers provided comments that improved the manuscript. Teck Cominco Inc. operators of the Red Dog Mine provided funding for the Kivalina samples to be collected and analyzed. National Oceanic and Atmospheric Administration (NOAA) Fisheries and the National Science Foundation (OPP Grant no. 9910319) provided funding for sample collections at the reference sites and NOAA Fisheries funded the analysis of tissues from the reference sites. All work was done under Marine Mammal Protection Act permit no. 358-1585 issued to ADF&G.