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Wildfire smoke may have amplified Arctic phytoplankton blooms

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Smoke from a wildfire in Siberia 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/Laval University) in Canada. The work sheds light on some potential ecological effects of wildfires in the Northern Hemisphere, particularly as these fires grow larger, longer and more intense.

In the summer of 2014, satellite imagery 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 nitrogen depleted,” 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 flow and ocean upwelling, but found nothing that would explain the amount of nitrogen needed for growth to occur.

But during that same period, unusually large wildfires in Siberia, Russia, located directly upwind of the bloom, had burned about 1.5 million hectares (or about 3.5 million acres) of lands.

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 was fed information on the wind, temperature and atmospheric composition – including the composition of wildfire smoke – from the period in question.

Model simulations showed that in late July and August 2014 – when the bloom was detected and the Siberian Wildfire was burning – atmospheric nitrogen deposition was almost double that of previous years and following.

“Wildfires have been localized to rapidly warming boreal regions that have a lot of peat in the permafrost melting,” Hamilton says. “Peat is very high in nitrogen, and smoke from burning peat has been assumed to be the most likely source of much of the extra nitrogen.”

“We know that fires can impact phytoplankton blooms, but it’s 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, given that fires are location-specific and difficult to predict, blooms like this won’t be the norm – but when these wildfires do occur, the nutrients they bring could lead to blooms. sustained or multiple.”

Next steps for researchers could include reviewing historical satellite records and further characterizing the chemical makeup of particles in the smoke to get a clearer picture of how wildfires like these might impact on different ecosystems.

“A one-time bloom like this won’t change the structure of the ecosystem, but Siberia and the Canadian High Arctic are experiencing more forest fires,” Hamilton says. “Therefore, it may be worth exploring potential downstream effects if fire activity and nutrient input remain high.”

The work appears in Earth & Environment Communications and has been supported by the Department of Energy under grant number DE-SC0021302, CNES (Centre National d’Etudes Spatiales) Alg-O-Nord research project, ArcticNet High Impact Publications Program and the European Union Horizon 2020 Marie Sklodowska- Bourse Curie (n° 746748).

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Note to editors: A summary follows.

“Aerosol deposition from wildfires likely amplified a summer bloom of Arctic phytoplankton”

DO I: 10.1038/s43247-022-00511-9

Authors: Mathieu Ardyna, Laval University, Stanford University and CNRS; Douglas S. Hamilton, North Carolina State University and Cornell University; Tristan Harmel, University of Toulouse; Léo Lacour, Julien Laliberté, Laval University; Diana N. Bernstein, University of Southern Mississippi; Chris Horvat, Brown University; Rémi Laxenaire, Florida State University and CNRS; Matthew Mills, Gert van Dijken, Kevin Robert Arrigo, Stanford University; Igor Polyakov, University of Alaska and Finnish Meteorological Institute; Hervé Claustre, CNRS; Natalie Mahowald, Cornell University
Published: September 19, 2022 in Earth & Environment Communications

Summary:
In recent years, an increase in the frequency of forest fires has been observed in July and August in boreal forest and tundra ecosystems on a pan-Arctic scale. Although wildfires in the Northern Hemisphere are common, they are becoming particularly unusual due to their increased latitude, duration and intensity. Such extreme wildfire activity is correlated with increased temperatures, dry conditions, and atmospheric disturbances (i.e. thunderstorms) associated with climate change. Here we report a newly observed and unexpected consequence of high latitude wildfires; large phytoplankton blooms near the North Pole (up to 82°N in the eastern Eurasian Basin), induced by northward transport and deposition of nutrients carried in wildfire aerosol smoke plumes . These Arctic surface waters, which are highly stratified and nitrogen depleted relative to phytoplankton requirements, received large amounts of wildfire-derived nitrogen in the summer of 2014, which alleviated the limitation of nutrients and triggered an unusually large phytoplankton bloom. These intensified climate changes to natural biogeochemical cycles will need to be quantified and incorporated into Arctic studies to account for their impacts on nutrient and carbon cycles.