Arctic Phytoplankton Bloom May Have Been Bolstered by Wildfire Smoke

phytoplankton bloom

According to recent research from North Carolina State University and the International Research Laboratory Takuvik (CNRS/Laval University) in Canada, smoke from a Siberian wildfire may have brought enough nitrogen to areas of the Arctic Ocean to enhance a phytoplankton bloom. The study clarifies some potential ecological impacts of wildfires in the Northern Hemisphere, particularly as they grow bigger, longer, and more intense.

The Laptev Sea, which is 850 kilometres (528 miles) south of the North Pole in the Arctic Ocean, experienced a larger-than-usual algal bloom in the summer of 2014.

“For a bloom that large to occur, the area would need a substantial influx of new nitrogen supply, as the Arctic Ocean is nitrogen-depleted. So we needed to figure out where that nitrogen was coming from,”

said Douglas Hamilton, assistant professor of marine, earth and atmospheric sciences at NC State and co-first author of a paper describing the work.

Nitrogen To Blame?

Large summer phytoplankton bloom near the North Pole (eastern Eurasian Basin) in summer 2014
Large summer phytoplankton bloom near the North Pole (eastern Eurasian Basin) in summer 2014. Credit: Mathieu Ardyna, et al CC-BY

The “usual suspects” for nitrogen input, such as sea ice melt, river discharge, and ocean upwelling, were the first things the researchers looked at. However, they were unable to identify anything that could account for the quantity of nitrogen required for the bloom to occur.

But at the same time, exceptionally large wildfires had burned about 1.5 million hectares (or about 3.5 million acres) of land in Siberia, Russia, which was directly upwind of the bloom.

The scientists then focused on the makeup of the atmosphere. In order to simulate what happens to emissions from both natural and human sources as they enter and exit the atmosphere, they used the Community Earth System Model (CESM), a computer model. The model was fed data from the time period in question on wind, temperature, and atmospheric composition, including the makeup of wildfire smoke.

Thawing Permafrost

The model simulations revealed that nitrogen deposition from the atmosphere in late July and early August of 2014 — when the bloom was discovered and the Siberian wildfire was raging — was nearly twice as high as in the years before and after.

“The wildfires were located in rapidly warming boreal regions, which have a lot of peat in the thawing permafrost. Peat is very nitrogen rich and the smoke from the burning peat was hypothesized as the most likely source of much of the additional nitrogen,”

Hamilton says.

“We’ve known that fires can impact phytoplankton blooms, though it is unexpected to see something like this in the Arctic Ocean. Most likely, since fires are locality-specific and difficult to predict, blooms like this won’t be the norm – but when these wildfires do occur the nutrients they bring in could lead to sustained or multiple blooms,”

said Mathieu Ardyna, co-first author and CNRS researcher at the International Research Laboratory Takuvik (CNRS/Laval University).

In order to gain a better understanding of how wildfires like these might affect various ecosystems, the researchers’ next steps might include reviewing the historical satellite record and further characterising the chemical composition of the particles within the smoke.

“A one-off bloom like this won’t change ecosystem structure, but both Siberia and high arctic Canada are getting more wildfires. So it may be interesting to explore potential downstream effects if fire activity and nutrient supply remain high,”

Hamilton concluded.

Reference: Ardyna, M., Hamilton, D.S., Harmel, T. et al. Wildfire aerosol deposition likely amplified a summertime Arctic phytoplankton bloom. Commun Earth Environ 3, 201 (2022). https://doi.org/10.1038/s43247-022-00511-9

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