Wildfire smoke may have amplified Arctic phytoplankton bloom
Large summer phytoplankton bloom near the North Pole (eastern Eurasian Basin) in summer 2014. Satellite-derived mean chlorophyll a concentration within the region of the bloom (28–155°E, 80–85°N) during the summer of 2014 (a). Dot color represents which satellite sensor (MODIS Aqua, Terra, or VIIRS) is used. Dot size is relative to the number of observations obtained (i.e., pixels). The blue line is the climatological daily average of surface chlorophyll a concentration over the period 2003–2019 (except 2014) with the shading envelope corresponding to the interval between the first and third quartiles. Sea-ice concentration and sea surface temperature, for the full period July 28–August 31 (b), and for the three time periods July 27–28, August 13 –15, and August 29–31 (c–e, respectively). Sea-ice concentration and chlorophyll a concentration, for the same dates as b–e, shown in panels f–i. For b–i: location of the bloom is within the dotted box (28–155°E, 80–85°N) and the continental shelf (bottom depth less than 50 m) is shown by cross-hatching. Credit: Mathieu Ardyna et al, Communications Earth & Environment (2022). DOI: 10.1038/s43247-022-00511-9

According to new research from North Carolina State University and the International Research Laboratory Takuvik in Canada, smoke from a wildfire in Siberia may have moved nitrogen to parts of the ocean. The work in Communications Earth & Environment sheds light on some potential ecological effects from Northern Hemisphere wildfires.

There was a large algal bloom in the Laptev Sea in the summer of 2014.

"For a bloom that large to occur, the area would need a substantial influx of new nitrogen supply," says Douglas Hamilton, an assistant professor of marine, earth and atmospheric sciences at NC State. The research was done at Cornell University. We had to figure out where that nitrogen came from.

The researchers looked at the usual suspects for nitrogen input, such as sea ice melt, river discharge and ocean upwelling, but didn't find anything that would account for the amount of nitrogen needed for the bloom.

Large wildfires in Siberia, Russia, located directly upwind of the bloom, burned 1.5 million hectares of land.

The researchers looked at the composition of the atmosphere. The Community Earth System Model is a computer model that can be used to model emissions from natural and human sources. Information about wind, temperature and atmospheric composition were fed into the model.

The model simulations showed that nitrogen deposition from the atmosphere was almost double when the bloom was detected and the fire was burning.

The fires were located in areas with a lot of peat in the thaw. Peat is rich in nitrogen and the smoke from burning it was thought to be the most likely source of extra nitrogen.

"We've known that fires can impact phytoplankton blooms, but it is unexpected to see something like this in theArctic Ocean," says the co-first author and researcher at the International Research Laboratory Takuvik. Since fires are locality specific and difficult to predict, blooms like this won't be the norm, but when these wildfires do occur, they could lead to sustained or multiple blooms.

A one-off bloom like this won't change the structure of the system, but Siberia and higharctic Canada are getting more fires. It may be interesting to explore potential downstream effects if fire activity continues to increase.

More information: Mathieu Ardyna et al, Wildfire aerosol deposition likely amplified a summertime Arctic phytoplankton bloom, Communications Earth & Environment (2022). DOI: 10.1038/s43247-022-00511-9 Journal information: Communications Earth & Environment