Heavy Metal Levels in Tissues of the Northern Fur Seal Collected from Five Rookeries in the Pribilof Islands - 1985
Diane M. Metzger; Edwin J. Skoch, PhD
Marine Mammal Research Laboratory, John Carroll University, University
Samples of liver, kidney and muscle were sent to our lab from 62 young, male Northern fur seals that had been harvested during the 1985 Federal harvest (under contract with NOAA Fisheries, Seattle). These animals were collected from 5 rookeries on St. Paul's Is., Pribilofs. The metals that were to be analyzed for included aluminum, chromium, copper, lead, nickel, zinc, cadmium, iron, titanium, and selenium. The analysis was accomplished by flame absorption spectroscopy using air-acetylene and nitrous oxide-acetylene gas mixtures. Many of the metals that were tested for in this study did not appear to present any particular hazard to the animals. Levels of titanium and selenium, however, appear to be somewhat abnormal, with a high mean value of 393.23 ppm for selenium. The intention of this report is to determine the difference between the rookeries, and the potential for toxicity of these metals for both the animal and the human consumer of these animals.
Data accumulated on the heavy metal levels in marine mammals has not been extensive throughout the years. Analysis of marine mammal tissues has been primarily on the muscle, liver, and kidney (1,2). The metals that have been most commonly analyzed for are mercury, zinc, lead and iron. The metals that were analyzed for in this study included nickel, copper, zinc, aluminum, chromium, lead, titanium, iron, cadmium, and selenium because they highly influence immune responses on animals and are considered to be both synergistic and anti-synergistic toxic agents (3).
During the past six years, this lab has been studying the levels of heavy metals in Northern Fur Seals and a variety of other marine mammals, the object being to determine "base" tissue metal loadings in both healthy and stranded animals. The potential of metal loadings in the tissues of animals poses a health hazard for them, and may influence immune response and reproductive success. It has been suspected by investigators that marine mammal strandings may be influenced by toxic materials.
It is the purpose of this paper to determine the heavy metal loadings in three types of tissues from young, male Northern fur seals collected from five rookeries, which were collected in the 1985 Federal Harvest in the Pribilof Islands. The determination of possible metal poisoning is difficult, as our lab did not receive all information regarding the seals. Please note that we were requested (by NOAA) to comment on the potential human health hazard of these animals as a food supply to the Aleut Indians. The Indians, however, primarily ingest the flipper after it has been pickled, but do take some liver and shoulder muscle (4). You will note that the data to be presented does not include flipper samples.
Materials and Methods
Our lab received frozen samples of liver, kidney and muscle taken from 62 young (2-4 years), male Northern fur seals from the 1985 Federal Harvest in the Pribilof Islands. Tissue samples were treated according to our standard method of preparation, utilizing microwave drying, acid digestion, and flame spectroscopy (5). The statistics that were performed included one and two-tailed "t" tests. The confidence interval used for all calculations was 95%.
The results showed a wide range of data for all metals, tissues and rookeries. In particular, higher copper and iron concentrations were observed in the liver samples as well as iron concentrations being high in muscle. Unusual levels of selenium in all tissues and in all rookeries was found. Titanium concentrations were high, particularly in those animals from Gorbatch.
Polovina showed the highest mean value of 28.80 ppm in the muscle tissue, with Zapadni being the next highest of 28.15 ppm. The largest fluctuation of levels between rookeries was observed in kidney (0.37ppm-21.05ppm). (Figures 1A, 3A).
Values for chromium proved to be considerably low for all tissues. The highest mean value was 2.97 ppm in muscle tissue from Polovina. A low of 0.77 ppm in kidney from Gorbatch was observed. No real fluctuations in levels was observed. (Figsure 1A, 3A).
Liver tissues from all five rookeries demonstrated consistently high mean concentrations of copper, the highest being 85.16 ppm. (Figure 2A) The next highest values for copper were shown in kidney with the lowest in muscle. (Figures 1A, 3A).
Animals from Gorbatch showed a value of 42.63 ppm in kidney tissue. (Figure 1A) other rookeries showed relatively consistent values of approximately 14 to 18 ppm.
Nickel values did not vary much between the tissues or the rookeries, except for muscle tissues from Polovina and muscle tissues from Gorbatch; 14.12 ppm and 15.53 ppm respectively. (Figure 3A).
A large fluctuation in concentrations between the rookeries was found in the kidney tissues. (Figure 1A) The highest mean value was 94.23 ppm from Tolstoi. Zinc levels were consistently higher throughout all of the tissues. (Figures 1A - 3A).
Considerably higher concentrations of cadmium were found in kidney tissues from all rookeries, ranging from 142.95ppm (Gorbatch) to 266.48 ppm (North East Point West). (Fig. 1A) The lowest values were found in muscle. (Figure 3A).
Iron concentrations were high in in muscle and liver tissues from all rookeries but Zapadni; muscle 774.61 ppm (Figure 3B), liver 1364.51 ppm (Figure 2B) and kidney 321.80 ppm (Figure 1B). Concentrations in the kidney were generally much lower (Figure 1B).
Gorbatch animals had high concentrations of titanium in kidney, 141.15 ppm (1B), and muscle, 224.41 ppm (3B). Concentrations were highest in muscle from Zapadni, 256.17 ppm (Figure 3B).
Selenium concentrations were consistently high in all tissues and in all rookeries, ranging from 74.21 ppm in kidney from Gorbatch, to 251.77 ppm in muscle from North East Point West (1B-3B).
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In general, the metals analyzed for that do not indicate or suggest a health hazard include aluminum, chromium, copper, lead, nickel, zinc, cadmium, and iron. The concentrations of titanium and selenium, however, indicate a possible toxic hazard. The animals from Gorbatch, Zapadni and Tolstoi had concentrations generally over 100 ppm, and sometimes over 200 ppm titanium. The data showed that there were much higher values for titanium in the muscle tissue than in kidney. The values for titanium that were obtained in this study indicate much higher values than would be considered normal. Studies previously done at our lab indicated that values considerably lower than those in the present samples, were proof of a contributory cause of a massive stranding of Fur Seals in the Seattle area in 1960 (6). Urine analysis on the same animals further showed the presence of titanium.(7) A study conducted by BioMed Research Laboratories,Inc. in Seattle (1980), showed that 175 ppm of potassium flour titanate killed 6 of 6 Coho salmon within one hour after the addition of the compound to the tank. when 10 ppm, 50 ppm and 100 ppm of the compound was added to the tanks, the fish did not die.(7) If these values were compared to ours, it would indicate that the animals from North East Point West and Polovina do not have a problem. The animals from Gorbatch, Zapadni and Tolstoi, however, showed values that might indicate a possible toxic problem.
Selenium values generally averaged in the 180 ppm range to 250 ppm range, for all animals and all rookeries. These higher values of selenium could indicate one of two things. These animals may be very healthy due to the fact that selenium is an anti-synergist to cadmium, but the levels may also be indicative of a further health problem, as selenium is also co-synergistic to mercury and is a known immune system stimulant/suppressant.
The results of our paper on harvested fur seals from 1984 suggest that the different metal levels and the loadings in the different tissues could be attributed to the males having fed at different areas before they returned to the rookeries (2). The data received in this study (1985 Harvest) indicates the same possibility to be true. From the data it appears that the rookeries of Gorbatch, Polovina and Zapadni contain animals with higher concentrations of toxic metals than the other two rookeries.
Metal loadings vary with both the age of the animal and the specific tissue site at which the tissue was sampled (e.g., the right lobe of the liver as opposed to the left lobe, or the different poles of different kidneys). The age data that was supplied with -the samples lists most of the animals as being three year old males. The samples from Gorbatch were the only ones that were supplied without any four year-old males. Immature males do not always return to the same rookery (4), and some of the range of data from high to low may reflect older animals, or animals related to members from other rookeries. When a study of possible relation to age and loadings was done, there were no significant conclusions that could have been made about the data. Prom what we were able to determine, there was no obvious relationship apparent. Because we had no data regarding the specific tissue site, nor did we receive information on tagged animals, it is difficult to offer anything more than these generalities.
A summary of our findings is this: The data suggests that the majority of the animals leave for different feeding sites, which may or may not be specific, and then return to the same rookery as in previous years. The animals from Polovina, Gorbatch and Zapadni have been exposed to higher levels of toxic metals, possibly due to food, industry, substrate loadings or to veterinary management of the rookery. The animals collected from North East Point West and Tolstoi appear to have a lesser exposure to the metals than the animals from other rookeries. Lead, zinc, and copper appear to show the least variation of the metals that have been tested for in this study, with chromium being next. Chromium, however, like lead does not tend to accumulate in the tissues. Selenium, titanium, and cadmium are all relatively new industrial metals with a continued increase in their use. it is not possible to discount their potential as toxic agents to these animals, especially because there were such high concentrations that were found in this study. The unusual iron data from the animals collected at Gorbatch might indicate a health problem. Blood data, such as blood iron levels or hematocrit levels could be useful. The data from the study suggests that the animals from North East Point West and Tolstoi are a safer food source to the Aleuts than are the animals from the rookeries of Polvina, Gorbatch, and Zapadni.
1. Hoste, R., E.J. Skoch and J. Grills. 1984. Heavy Metal Analysis in the Northern Fur seal, Calorhinus Ursinus. Proc. 15th Ann. IAAAM Conf. a and Wksp.
2. Richard, C.A. and E.J. Skoch. 1987 Comparison of Heavy Metal Concentrations Between Specific Tissue Sites in the Northern Fur Seal Proc. 17th Ann IAAAM Conf. and Wksp.
3. van Heeckeren, Anna and E.J. Skoch. 1987. Potential Heavy Metal Influence on the Death of Several Species of Pinnipeds. Proc. 18th Ann.Conf. IAAAM Conf. and Wksp.
4. Personal Communication with Dr. C. A. Wood, NOAA, Seattle.
5. LaCognata, Salvatore and E.J. Skoch. 1987. A Comparison of Techniques for the Extraction of Heavy Metals in Tissues. Proc. 18th Ann. IAAAM Conf. and Wksp.
6. Skoch, E.J., R. Hoste and C. Bral. 1985. Titanium, Aluminum and Flouride Levels in Tissues of the Northern Fur Seal. Proc. 16th Ann. IAAAM Conf. and Wksp.
7. Personal communication with Dr. T.A. Gornal, Marine Mammal Stranding Center, Seattle.