Smoke from a Siberian wildfire may have carried enough nitrogen to parts of the Arctic Ocean to amplify a phytoplankton bloom, according to new research from North Carolina State University and the Takuvik International Research Laboratory (CNRS/University Laval) in Canada. The work sheds light on some of the potential ecological effects of Northern Hemisphere wildfires, particularly as these fires grow larger, longer and more intense.
In the summer of 2014, satellite images detected a larger-than-normal algal bloom in the Laptev Sea, located in the Arctic Ocean about 850 kilometers (528 miles) south of the North Pole.
“For such a large bloom to occur, the area would need a substantial influx of new nitrogen supply, as the Arctic Ocean is depleted of nitrogen,” says Douglas Hamilton, assistant professor of marine, terrestrial and atmospheric sciences at NC State and co-first author of an article describing the work. Hamilton was previously a research associate at Cornell University, where the research was conducted. “So we had to figure out where that nitrogen was coming from.”
First, the researchers looked at the “usual suspects” of nitrogen input, such as melting sea ice, river discharge and ocean upwelling, but found nothing that accounted for the amount of nitrogen required for flowering to occur.
But during that same time period, exceptionally large wildfires in Siberia, Russia, located directly upwind of the bloom, had burned an estimated 1.5 million hectares (or about 3.5 million acres) of land .
So the researchers turned their attention to atmospheric composition. They used the Community Earth System Model (CESM), a computer model that can simulate what happens to emissions from natural and human sources as they enter and leave the atmosphere. The model received information about the wind, temperature and atmospheric composition, including the composition of wildfire smoke, for the time period in question.
Model simulations showed that during late July and August 2014, when the bloom was detected and the Siberian wildfire was burning, nitrogen deposition from the atmosphere was nearly double that of previous years and next.
“The wildfires were located in rapidly warming boreal regions that have a lot of peat in the thawing permafrost,” says Hamilton. “Peat is very rich in nitrogen, and it was hypothesized that smoke from burning peat was the most likely source of much of the extra nitrogen.”
“We know that fires can affect phytoplankton blooms, although it is unexpected to see something like this in the Arctic Ocean,” says Mathieu Ardyna, co-first author and CNRS researcher at the Takuvik International Research Laboratory (CNRS/ Laval University). “Most likely, because fires are locality-specific and difficult to predict, blooms like this will not be the norm, but when these wildfires do occur, the nutrients they provide could lead to sustained or multiple blooms.” .
The researchers’ next steps could include reviewing the satellite’s historical record and further characterizing the chemical composition of particles within the smoke to get a clearer picture of how wildfires like these could affect different ecosystems.
“A one-time bloom like this won’t change the structure of the ecosystem, but both Siberia and high Arctic Canada are getting more wildfires,” says Hamilton. “Therefore, it may be interesting to explore potential downstream effects if fire activity and nutrient supply remain high.”
The work appears in Communications Earth & Environment and was supported by the Department of Energy under grant number DE-SC0021302, the Alg-O-Nord research project of the CNES (Centre National d’Etudes Spatiales), the Program of High Impact Publications from ArcticNet and a Marie Sklodowska-Curie grant from the European Union Horizon 2020 (no. 746748).
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