Narwhal tusks have lots of illuminating tricks


    a remarkable spiraled tooth that can extend up to 10 feet long, holds crucial details about a fast-changing Arctic, a new research study has found.

    The study, published on March 10 in the journal Existing Biology, evaluated stable isotopes and mercury concentrations in 10 narwhal tusks. The authors– led by Rune Dietz, a conservation biologist at Aarhus University in Denmark, and Jean-Pierre Desforges, a postdoctoral scientist at McGill University– discovered that both the narwhals’ diet plan and their direct exposure to mercury altered significantly in between the years 1960 and 2010. The scientists assume these shifts relate to the effects of a warming world.

    Narwhal tusks grow a bit each year and due to the fact that they are connected to the blood stream, they can indicate changes in the animals’ diets. By examining these giant teeth, scientists can glean timed physiological info– kind of like tree rings, coauthor Desforges states which researchers utilize to discover historic variations in climate. The tusks, which were gathered from Inuit subsistence hunters in northwest Greenland, in many cases belonged to animals that were over 50 years old, allowing researchers a wide breadth of historic information within a single sample.

    Steady isotopes of carbon and nitrogen “are basically utilized as dietary proxies to inform us something about what types the animals are consuming,” explains Desforges. “But also we can take a look at toxins like mercury, due to the fact that this can be transferred in the teeth as well.”

    The team’s findings recommend that before the 1990’s, when sea ice levels were regularly high, the narwhals were most likely feeding on arctic cod, which grow in sea ice environments, along with fish like halibut, which are higher up on the food cycle. After 1990, as the sea ice started to decrease, the information show that the narwhals switched to various prey, lower on the food cycle. It’s just a connection, Desforges states, but “the observed styles that we see seem to match extremely well with the modifications in the natural environment.”

    As humans continue to heat up the world, we’re losing Arctic sea ice at shocking rates. That sea ice, which traps a lot of nutrients, is securely wound into the Arctic food web: Sea ice nutrients feed the plankton, who feed the fish, who feed the seals and whales, who feed the polar bears, and so on. The loss of sea ice can interrupt which types live where, and who eats what. And due to the fact that more toxins build up the greater up you go in the food chain (a process referred to as “biomagnification”), when there’s a modification in the ecosystem, “there’s a chance for that to alter the way that contaminants move in the food web,” Desforges says.

    Mercury, a naturally-occurring metal and neurotoxin that’s been spewed out at unsafe rates by extractive procedures like mining, is all over the Arctic. The authors discovered that mercury levels in the narwhal tusks increased in between 1962 and 1990, probably a reflection of the greater mercury levels of the fish that the narwhals were eating, and the way toxic substances build up in animals’ bodies with age. “The unexpected thing was after the 1990s and the 2000s”– when the narwhals started eating fish lower down on the food chain, which must imply less mercury–” we actually see mercury levels increase, and not just increase above what we anticipated, but at a greater rate than any other time in our time series,” states Desforges.

    The authors speculate that this unexpected spike belongs to more mercury putting into the environment, climate-related changes in the food web, or both.

    ” We’re handling multiple stressors of change, and this study is revealing the cumulative effects of that,” states Lisa Loseto, a research researcher at Fisheries and Oceans Canada who was not included in the research study. This research study is “considering climate change and impurities together, and what one species is having to deal with in the Arctic– the place that’s sustaining the most alter.”

    The study’s findings are “a call to action,” states Loseto, that “we require to take a look at our effects on wildlife in the Arctic.”

    Published at Fri, 02 Apr 2021 14:00:52 +0000