How can we measure the impact of climate change on marine biodiversity? By focusing on the microbial population, among others. A new study led by Concordia University demonstrates a change in the diversity of bacteria present in the Arctic Ocean likely linked to warming waters.
Co-written by David Walsh and Arthi Ramachandran of Concordia University and published in January in the journal ISME Communicationsthe study looks at the genetic composition of bacteria and other microorganisms present in this ocean, and the changes it has undergone over a period of nine years.
“Bacteria are an abundant component of marine ecosystems,” explains Mr. Walsh, professor of biology. “These bacteria play essential roles in the marine food chain”, particularly with regard to the transformation of organic matter, a bit like compost on land, he illustrates.
The advent of climate change, particularly ocean warming, has a direct impact on these bacterial populations. The study, in particular, focuses on the Arctic Ocean, which is warming faster than any other ocean on Earth, leading to profound changes in the region’s ecosystems.
The researchers took samples from different depth levels of the Beaufort Sea, northwest Canada and northern Alaska, between 2004 and 2012. A place which is also experiencing an increased increase in its contribution in fresh water, which disrupts ocean currents and local biodiversity.
“This is quite a unique project, because it is one of the first time series studies that focuses on microbial diversity” in the ocean, emphasizes Mr. Walsh. This period stands out in particular because it contains two years, 2007 and 2012, when records were broken with regard to the glacial surface in the Arctic — that is to say, two years when the sea ice reached record minimum levels.
“Subtle, but significant” results
“What we observed was a subtle but significant loss of bacterial biodiversity in the Arctic Ocean,” notes David Walsh. Nothing drastic, he adds, but these are changes that deserve to be highlighted and, above all, studied. Especially since this is one of the first studies where these fluctuations over time are attributed and directly linked to climate change, recalls the researcher.
At this stage, it is difficult to determine the long-term implications of such a discovery, but some avenues exist. “The next thing is to understand how these changes will affect the structure and function of the marine food chain,” says Walsh.
As ocean warming and softening continue, we will notice increasingly concrete — and harmful — consequences on ecosystems. Softening, among other things, causes stratification of the ocean, which pushes nutrients needed for photosynthesis into deeper layers and therefore makes them less accessible to the surface, where this process takes place.
“From this point on, we can see a decrease in organic matter and energy production in all systems. And it is considerable, because it is this energy which feeds the upper levels of the marine food chain, summarizes the professor.
What is happening in the Arctic Ocean could therefore take shape in the other oceans of the planet. As a reminder, last March recorded a record average ocean surface temperature, set at 21.07°C. According to the latest data from the European climate observatory Copernicus, the month of April seems to continue this trend, with sea temperatures well beyond the last records set in the last twenty years.
This content is produced in collaboration with Concordia University.