Abstract

Tissues obtained from three populations of Northern fur seals were analyzed for heavy metals. This paper presents the results of this project and establishes, what the authors believe, to be the first baseline data for this species.

Introduction

Little heavy metal data has been accumulated on marine mammals. Large quantities of mercury (172.0 ppm) (1) in Northern fur seals (Callorhinus ursinus) and lead (34.2 ppm) (2) in California sea lions (Zalophus californianus) have been reported even though these animals appeared healthy. Cadmium was found concentrated in the kidney in several pinnipeds. California sea lions, from Oregon coastal waters, had kidney cadmium levels of 10.2 ppm (3). Harbour seals (Phoca Vitulina) and Northern fur seals had kidney cadmium levels lip to 0.17 ppm (3) and 15.6 ppm (1), respectively. Lead was found in harbour seal bone at 3.5 ppm (4) and in the liver at 0.74 ppm (5). Although no marine mammal deaths have been definately linked to metal poisoning, it has been suspected in one case (6).

Materials and Methods

Northern fur seals from three different locations were obtained for this study. One group of seals was collected at sea, during a Bering Sea cruise of a NOAA research vessel, between September 22-October 12, 1982. This group consisted of ten females and five males. Ages were estimated at the time of collection.

The second group of seals was collected or found dead off Long Beach Peninsula in Seattle, Washington, during March, 1980. All of the seven animals were females. No ages were taken.

A third group of seals was collected at St. Paul, Pribilof Islands, Alaska, during the summer of 1982. Twenty-eight of these animals were females and four were males. The ages of these animals were estimated to be between three and seven years.

Tissue samples were cut frozen, weighed, acid digested, and ashed using a modification of the technique suggested by Pinta (1962). This modification was developed by the authors (7).

The heavy metal levels were then determined by flame Atomic Absorbtion Spectroscopy using both nitrous oxide and acetylene gas techniques. The following tissues were analyzed: brain, kidney, liver, and fat. The metals analyzed for were lead, nickel, cadmium, chromium, copper, and iron.

Results

Lead Results

Seas

The highest lead in these animals was found in the brain tissue (23.33 ppm) in one animal. Mean values were: brain, 1.581 ppm; kidney, 0.006 ppm; liver, 0.002 ppm; and fat, 0.002 ppm (Figure 1).

Pribilofs

Overall, the highest mean lead value in the seals collected from the Pribilofs was in the liver (0.166 ppm). Other mean values were- brain, 0.028 ppm; kidney, 0.020 ppm; and fat, 0.012 ppm (Figure 1).

Seattle

Mean values of lead in these animals were: brain, 0.005 ppm; kidney, 0.002 ppm; liver, 0.002 ppm; and fat, 0.012 ppm (Figure 1).

Nickel Resuts

Seas

The smallest ranges of nickel among the three groups were detected in the animals from the sea. Mean values were: brain, 0.005 ppm; kidney, 0.111 ppm; liver, 0.006 ppm; and fat, 0.002 ppm (Figure 2).

Pribilofs

Higher amounts of nickel were found in this group. Mean values were: brain, 0.202 ppm; kidney, 0.111 ppm; liver, 0.082 ppm; and fat, 0.154 ppm (Figure 2).

Seattle

Nickel levels in this group were similar to those of the Pribilof group. Mean values were: brain, 0.070 ppm; kidney, 0.006 ppm; liver, 0.006 ppm; and fat, 0.188 ppm (Figure 2).

Cadium Results

Seas

Highest mean values of cadmium in this group were found in the kidney (1.792 ppm). Other values were: brain, 0.002 ppm; liver, 0.522 ppm; and fat, 0.001 ppm, Figure 3).

Pribilofs

High mean cadmium values were found in the kidney (1.022 ppm) and liver (0.0373 ppm). Other values were: brain, 0.002 ppm; and fat, 0.001 ppm (Figure 3).These animals, in breeding condition, were not actively feeding and thus, cadmium values should be lower than those values from the see.

Seattle

Lower cadmium values were recorded in these animals as compared to the other two groups. Kidney mean value was 0.396 ppm. Other values were: brain, 0.003 ppm; liver, 0.172 ppm; and fat, 0.005 ppm (Figure 3).

Chromium Results

Seas

Mean values of chromium in these animals were: brain, 0.026 ppm; kidney, 0.019 ppm; liver, 0.014 ppm; and fat, 0.027 ppm (Figure 4). These animals are probably accumulating chromium through the food chain, in addition to metabolizing a thicker fat layer.

Pribilofs

Mean ranges of chromium were: brain, 0.005 ppm; kidney, 0.001 ppm; liver, 0.003 ppm; and tat, 0.001 ppm (Figure 4).

Seattle

No significant amount of chromium was found in this group (Figure 4).

Copper Results

Seas

Mean copper levels were: brain, 0.067 ppm; kidney, 0.162 ppm; liver, 0.284 ppm; and fat, 0.002 ppm (Figure 5).

Pribilof

Similar copper levels as those found in the sea animals were found in the Pribilof group. Mean values were: brain, 0.039 ppm; kidney, 0.070 ppm; liver, 0,225 Ppm; and fat, 0.001 ppm (Figure 5).

Seattle

Somewhat lower copper values were found in this group, as compared to the other two. Mean values were: brain, 0.039 ppm; kidney, 0.032 ppm; iver, 0.075 ppm; and fat, 0.000 ppm (Figure 5).

Iron Results

Seas

The highest mean value of iron was recorded in the liver (1.338 ppm). Other values were: brain, 1.519 ppm; kidney, 0.550 ppm; and fat, 0.375 ppm (Figure 6).

Pribilofs

The highest mean iron value (1-297 ppm) was found in the liver. Other values were: brain, 0.644 ppm; and fat, 0.223 ppm (Figure 6).

Seattle

Slightly higher mean values were recorded in these animals. Values were: brain, 0.466 ppm; kidney, 0.735 ppm; liver, 2.450 ppm; and fat, 0.408 ppm (Figure 6).

Discussion

Looking at these groups of animals, it appears that nickel and lead concentrations were highest in those seals that were found at the Pribilofs. Those collected from the sea had higher levels of cadmium and chromium. Iron and copper, on the other hand, appeared to be about the same in all groups.

Looking at these groups of animals, it appears that nickel and lead concentrations were highest in those seals that were found at the Pribilofs. Those collected from the sea had higher levels of cadmium and chromium. Iron and copper, on the other hand, appeared to be about the same in all groups.

Upon closer examination of the data, it is apparent that certain trends can be noted. Brain, liver, kidney, and fat were the four organs that consistently showed measurable metal levels. It appears that both chromium and copper concentrations in these organs were consistently higher in the animals collected at sea, than either of those from Seattle or the Pribilofs. Iron levels also tended to be higher in the animals from the sea, except in the case of the kidney within the Pribilof group. Cadmium levels in fat were highest in the Pribilofs, yet levels in brain, kidney, and liver appear highest at sea. In contrast, the Pribilof group tended to have higher lead and nickel values in all organs. At sea, during the non-breeding period, fur seals are actively feeding, growing, and producing fat. Chromium is known to be involved in fat synthesis and this may be a reason for the higher chromium values in those seals collected at sea. Body metabolism in these animals is also high and may explain the higher iron and copper values. Cadmium may be accumulated at the higher levels of the food chain.

A different physiological state is encountered within the Pribilof animals. These are breeding animals with hormonal and metabolic levels that differ from those at sea.

These animals are not actively feeding, and are using fat reserves for energy. With metabolism of fat tissue, metals tend to circulate in the body. This may be the reason for the higher levels of these metals in the Pribilof animals.

Animals from the Seattle area remain puzzling. Levels of metals were the lowest of all the groups (except in the case of the brain and the metal cadmium). These animals were on their northward migration to the Pribilofs. The accidental spill of flurotitinate, which occured at the time of the strandings, may have had influence not only on the low metal levels, but also in stress related physiological problems encountered during the beaching. The animals from Seattle showed what appears to be a stress related fluctuation in metal levels. This theory is supported by a comparison of tissues in other Northern fur seals (8).

In conclusion:

1. Mean lead and nickel levels were generally higher in those animals collected at the Pribilofs. This could be due to their metabolic state, which accompanies breeding conditions.
2. Mean cadmium, chromium, and copper levels were generally higher in those animals collected at sea. This is probably related to their active feeding condition.
3. Iron Ievels appeared to be similar among all three groups. The major exception was that those animals from the Washington coast (Seattle) had a significantly higher level of iron in the liver tissues than either of the other two groups.
4. With the exception of a brain lead value of 23.33 ppm in one seal from the sea group, no "toxic" levels were noted.
5. No significant differences in any of the tissues were noted between males and females.
6. More useful data may be obtained by monitoring the movement of heavy metals in the circulatory systems and organ systems of live animals during periods of illness, unusual behavior, or other stress related phenomena.

References

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3. Buhler, at al. Heavy metals arid chlorinated hydrocarbon residues in California sea lions (Zalophus californianus). J Fish. Res. Bd. Canada 32: 2391-2397 (1975).
4. Roberts, at al. Distribution of heavy metals in tissues of the common Seal. Marine Poll. Bull. pp. 194-196 (1972).
5. Harins, U., et al. Further data on heavy metals and organochlorines in marine mammals from the German coastal waters. Meersforsch 26: 153-161 (1978).
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