The Arctic at Risk:
A Circumpolar Atlas of Environmental Concerns

by Stephanie Pfirman, Kathleen Crane, Kim Kane, and Tania Simoncelli

Review Draft: Not for Citation

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Biota

One of the greatest problems with some pollutants is their tendency to build up in the body and cause toxic effects in animals, including humans. The term for this process is bioaccumulation, which refers to the ability of a chemical to accumulate in living tissues during the life span of the organism. As a result, older organisms have higher concentrations of these pollutants. Bioaccumulation of pollutants can take place from water, food, or air, and often from more than one source. The chemicals that show greatest bioaccumulation are those that do not dissolve in water, but do dissolve in fats and oils; for example, the dioxins and PCBs. Hence, more of these pollutants are found in the fat and fat-containing tissues, like the liver, of animals than in muscle, for example, which contains very limited amounts of fat.

In extreme cases, this accumulation of pollutants also may be greater in carnivorous animals high on the food chain, such as meat-eating birds and humans. Toxic chemicals taken up from underwater sediments by small fish are passed on to predatory fish. Mammals and birds that eat these fish will, in turn, accumulate even greater concentrations of the chemicals. With each link in the food chain (each trophic level), the concentration increases. This process is called biomagnification. To make matters worse, the chemicals that accumulate and concentrate also remain in living tissues the longest, some for decades.

The Arctic ecosystem is especially vulnerable to contaminants (e.g., Barrie et al., 1992; Lockhart et al., 1992) because:

1) there is generally low species diversity in the Arctic, and some species have low fecundity, making them vulnerable to stress;

2) the long length of the food chain makes it susceptible to biomagnification and disruption if any of the links are impaired;

3) many organisms are long-lived, so persistent contaminants that break down slowly have a long time to accumulate in the animal, and then are passed up the food chain when consumed;

4) many contaminants are found in fatty tissues, which make up much of the mass of organisms at the top of the Arctic food chain, due to the temperature-regulating properties of fat (e.g., seals, whales, and polar bears); and

5) there is high per-capita human consumption of local wildlife or "country foods."

Terrestrial Biota

In general, vegetation and biodiversity decrease toward the north. Along the northern reaches of the continents is the Arctic desert. Less than 10% of the land surface here is covered with vegetation (Encyclopedia Britannica, 1990). Plants grow in compact cushions for protection against the severe climatic conditions.

To the south is the high Arctic tundra, consisting largely of herbs and mosses. Still farther south is the low Arctic tundra, found in northern Alaska, southern coastal areas of Greenland, and Russia. The vegetation here consists of dwarf shrubs, mosses, sedges, grasses, and lichens.

Tundra is separated from the boreal forest of the subarctic region by the treeline. The treeline is defined as the absolute northern limit of tree-like species. It generally follows the 10deg.C July isotherm and is sometimes used to define the southern limit of true Arctic conditions.

The terrestrial contaminant pathway is from the air to the plants and then to the animals. Feeding on the Arctic tundra, northern grazing mammals ingest pollutants deposited from the atmosphere. For example, lichens accumulate atmospheric contaminants on their surface over a long period of time. As a result, their contaminant load reflects atmospheric input. Caribou (reindeer) are herbivores. Because they feed mainly on lichen in winter, their contaminant levels will be largely influenced by deposition from the atmosphere (Elkin, 1993). In addition, caribou are a major component of the traditional diet in northern communities. This lichen-caribou-human pathway was important in transferring radionuclides to the human population as a result of atmospheric fallout from atomic bomb testing in the 1950's and early 1960's and, more recently, from the accident at Chernobyl. Unfortunately there are only limited data available on contaminant levels in caribou tissues used as country food (Elkin, 1993).

Many of the larger animal species in the Arctic migrate seasonally to take advantage of the short but intense summer growing season. For example, caribou migrate between the Arctic tundra and the boreal forest. Many birds migrate even farther, with wintering grounds as far away as Brazil (Encyclopedia Britannica, 1990). With such long migration routes, analysis of contaminant levels is complicated, as pollutants may be introduced in a variety of source regions.

Limnic Biota

Freshwater fish include whitefish, lake trout, and the Arctic char. Freshwater located far from sources of pollutants can become contaminated due to deposition from the atmosphere. The char, a member of the salmon family, spends most of its life in freshwater, venturing into the sea for only a few weeks each summer. Char, an important food source of northern peoples, is exposed to both terrestrial and coastal pollutants.

Marine Biota

According to Muir et al. (1992), the transfer of some pollutants, such as organochlorines, from seawater to organisms begins with contamination of ice algae or phytoplankton. Ice algae are small plants attached to sea ice. Pollutants then are transferred up the food chain when the algae are consumed. The marine food chain in the Arctic is approximately as follows (Welch et al., 1992; Muir and Norstrom, 1994): phytoplankton living in surface ocean waters and associated with sea ice are eaten by zooplankton such as copepods, the main food of Arctic cod. Arctic cod are a major food source for the ringed seal, beluga, narwhal, and some seabirds. Polar bears, at the fifth trophic level, feed mostly on ringed seals. Seals, belugas, narwhals, and polar bears will be influenced by contaminants in the ocean water as well as by contaminants entering the surface ocean from the atmosphere or sea ice melt, and from river runoff in coastal areas. Walrus are different because they feed on benthic fauna (sea floor dwellers) such as clams, which they root up with their tusks from the shallow sea floor. Walrus are likely to ingest contaminated benthos in regions where the near-bottom waters and sea-floor sediments are polluted. Because they feed at a lower trophic level than seals and other marine mammals, the effects of biomagnification are not as extreme in walrus. Finally, humans consume polar bear meat (muscle tissue), seals, belugas, narwhals, walrus, cod, and halibut.

Seabirds, such as black guillemots, feed on polar cod associated with sea ice (Lønne and Gabrielsen, 1992). Other seabirds feed on small animals associated with the ice and in the surface waters. Approximately 6 million seabirds, representing 75% of the birds in North America, breed in the Arctic (ICBP, 1984--from Barrie et al., 1992).

Contaminant levels in parts of the marine food chain are now high enough to cause concerns about human consumption of particular animals, as well as to raise concerns about the health of the animals themselves. Muir and Norstrom (1994) concluded: "Given elevated levels of some contaminants, particularly toxaphene and PCBs in narwhal, beluga, and polar bear fat, as well as heavy metals, particularly of cadmium in narwhal kidneys, it is clear that studies of effects on biota themselves at the biochemical and population level are needed."

Arctic Cod Northern Fulmar Black Guillemot Thick-Billed Murre
Walrus Selected Whales Narwahl Beluga
Ringed Seals Polar Bears Arctic Char Whitefish
Lake Trout Caribou-Reindeer

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