Decline in microbial genetic richness in the western Arctic Ocean

In a Concordia-led study published in the journal ISME Communications, the researchers analyzed archival samples of bacterial and archaeal populations taken from the Beaufort Sea, bordering northwestern Canada and Alaska. The samples were collected between 2004 and 2012, a period that included two years — 2007 and 2012 — in which sea ice coverage was historically low. The researchers looked at samples taken from three water levels: the summer mixed layer, the upper Arctic water beneath it and the deep surface Pacific water.

The study examined the genetic makeup of microbes over a nine-year period using bioinformatics and statistical analysis. Using this data, researchers were able to see how changing environmental conditions were affecting the structure and function of organisms.

The researchers found subtle but statistically significant changes in the communities they studied.

“We observed an overall loss in species diversity across all the different water bodies,” says David Walsh, professor in the Department of Biology and corresponding author of the paper.

“We also saw changes in the composition of the microbial community, meaning that species diversity was minimal after the 2007 sea ice melt compared to before.”

However, periods of declining population richness alternated between ocean water layers. In 2005–2007, a sudden drop in fresh summer mixed water levels between 3–9 m depth was observed. Upper Arctic water, between 16-78 m, was observed to decrease in 2010-2012, while deep Pacific water, between 49-154 m, experienced a two-step decrease — once between 2005-2007. Between and again between 2010-2012. .

Small beginnings

The researchers are careful not to overemphasize the implications of their findings, saying that the changes, although significant, remain modest. But with summer Arctic ice cover continuing to shrink year-over-year, the data point to potential trends that could be seen in population studies in recent years.

“With the warming and freshening of the Arctic Ocean comes the depletion of nutrients that are important for photosynthesis, which produces organic matter that serves as a source of energy and carbon for the marine food web,” Walsh explains. Walsh explains.

“This change threatens to reinforce what is known as the microbial loop, in which energy and carbon that would normally go to higher trophic levels — namely zooplankton and then fish — are rapidly recycled by microorganisms. which will be strengthened as the system continues.”

“This study gives us a fundamental idea of ​​what’s going on in the Arctic,” says co-author Arthi Ramachandran, PhD 23. “The Arctic is warming four times faster than the rest of the world, which makes it an interesting ecosystem. Study. All oceans are interconnected, and the physical barriers of these oceans are shrinking. “

Exploring the ocean’s warmer, fresher future

The researchers are now planning a metagenomic study that extends the time series to cover periods of even more extreme sea ice minima. They hope to completely sequence the organism’s genome to further understand the diversity and function of microbial communities in the environment.

Other co-authors of the paper are PhD candidate Vera Ona, Environment and Climate Change Canada’s Susan Kremer and Fisheries and Oceans Canada’s William Lee.

gave National Science and Engineering Research Council of CanadaDiscovery program contributed to the funding for this study.