Polar bears (Ursus maritimus)-classified as a marine mammal, roam the arctic sheets and swim in the region’s coastal waters. As these bears depend on sea ice for their existence and are directly impacted by global warming and climate change, it makes them a significant indicator species (Ramsay M., 1998). Polar bears are also on the top of the very long Arctic marine food chain and by measuring the levels of contaminants in their tissues; scientists get an idea of the degree of contamination of the Arctic marine ecosystem.
Now, a new worrisome study has surfaced which says that Polar bears in and around Svalbard in the Arctic are found to be carrying increased loads of mercury in their bodies. The study, published in the journal Environmental Science and Technology on May 15, 2020, says that the increasing load of mercury–a potent neurotoxic pollutant, in the bodies of Polar bears indicates that rapid warming is releasing mercury previously locked by the Arctic’s freezing temperatures (Lippold A, et al., 2020).
The scientists examined nearly 200 hair samples of female polar bears collected from 1995 to 2016 from the Barents Sea region. The study recorded yearly median total mercury (THg) concentrations ranged from 1.61 to 2.75 micrograms per grams and increased nonlinearly by 0.86 micrograms per grams in total over the study. It says that “the rise in THg concentrations in the polar bear food web was possibly related to climate-related re-emissions of previously stored Hg from thawing sea-ice, glaciers, and permafrost” (ibid).
The surprising aspect of this study is that it recorded the mercury increase in Svalbard bears, which is on the Norwegian Arctic archipelago, while the situation is quite opposite in the Southern Beaufort Sea polar bears where a previous study has recorded decreased mercury levels in the bodies of polar bears. Between 2004 and 2011, samples from Beaufort Sea polar bears showed a 13 per cent annual decline in the mercury levels in their bodies (Melissa A, et al., 2020).
The study attributes the foraging ecology for the decline and not the declining environmental concentrations of mercury. Now Southern Beaufort Sea bears are spending more time on land and left over Krill-eating bowhead whales on beaches have become an important part of their food source, which is lower on the trophic level than fish eating seals. Consequently they accumulate less mercury.
As far as Svalbard polar bears are concerned, they are also spending more time on land and their dietary trend is also changing, however, the reason behind the increased mercury concentration is warming and reduced ice–exposing more open water that can absorb mercury from the atmosphere (Rosen Y., 2020).
This is not surprising. The NASA and National Science Foundation-backed National Snow and Ice Data Centre (NSIDC) study shows that over the past 30 years, the Arctic has warmed at roughly twice the rate as the rest of the globe and the amount of floating sea ice in the region is also dropping (Andrews L., 2020). And the study by Anna Lippold and others shows that climate change is more pronounced in the Svalbard area than elsewhere in the Arctic.
Mercury in the Permafrost
Any soil that remains frozen at 0°C or cooler for at least two years straight, keeps carbon buried within it by acting as massive ice traps. In recent times, increased human activities are driving global warming causing permafrost thawing (Paul F. Schuster et al., 2018). As per one calculation, there are 32 million gallons worth of mercury trapped in the permafrost, which is twice as much mercury as the rest of the all soils, the atmosphere and ocean combined (Mooney C., 2018). Once exposed to a mercury laden environment, human and wildlife health are bound to be impacted. Mercury can adversely alter the neurological and reproductive systems of humans and wildlife (Tomle P., 2012).
What do you know about Polar bears?
-Polar bears are carnivorous marine mammals and their average lifespan in the wild is 25 to 30 years.
-They are marine mammals because they spend most of their lives on the sea ice in the Arctic Ocean.
-Polar bears survive in the Earth’s coldest environment thanks to the thick coat of insulated fur.
-These bears prey on fish-eating seals.
-The Inuit people call the Polar bear nanuq, Russia calls it beliy medved whereas in Norway and Denmark it is called isbjorn.
-Female polar bears usually give birth to twins.
-Polar bears look white, but actually have black skin and hollow, colourless hair.
Mooney C., 2018. The Arctic is full of toxic mercury, and climate change is going to release it, available at https://wapo.st/2BvxgLS.
Ramsay M., 1998. University of Saskatchewan in Canada, available at: https://www.pulseplanet.com/dailyprogram/dailies.php?POP=1770
Lippold A et al., 2020, available at https://pubs.acs.org/doi/abs/10.1021/acs.est.0c01848
Melissa A, et al., 2020. Ecological change drives a decline in mercury concentrations in Beaufort Sea polar bears, available at https://pubs.acs.org/doi/abs/10.1021/acs.est.7b00812
Andrews L., 2020. Arctic records its hottest temperature EVER as mercury hits 100F in town of Verkhoyansk in Siberia, available at http://dailym.ai/2YGVwUN.
Rosen Y., 2020. Rapid warming is probably behind a spike in mercury levels in Svalbard polar bears, available at https://bit.ly/2NlwvYK.
Paul F. Schuster et al., 2018. Permafrost Stores a Globally Significant Amount of Mercury, available at https://bit.ly/2NimqMb.
Tomle P., 2012. Mercury’s Harmful Effects, available at https://www.nwf.org/Magazines/National-Wildlife/2013/DecJan/Conservation/Mercury-and-Wildlife
WWF, available at https://wwf.ca/species/polar-bears/
Facts about polar bears, available at https://wwf.to/2B0sK8h.