Smoke from Australian bushfires caused massive phytoplankton blooms in the Southern Ocean | Forest fires

Smoke from Australia’s bushfires in the 2019-20 season caused phytoplankton to thrive in the Southern Ocean larger than the entire Australian continent, according to new research.

An international team of scientists has discovered via satellite data that a bloom of phytoplankton – microscopic marine algae – occurred in the ocean between South America and New Zealand starting in October 2019 and lasted about four months.

Smoke clouds from Australian bushfires in black summer Travel to the stratosphere And roam around the world, aerosol particles are deposited thousands of kilometers from Australia.

The study published in the journal temper natureI found that the flowers were the result of iron particles in the smoke mist.

Study co-author Professor Peter Struton, of the University of Tasmania’s Institute of Marine and Antarctic Studies, likened the phytoplankton bloom to “the transformation of the entire desert into a moderately productive grassland for a few months”.

Phytoplankton require iron for photosynthesis. “The entire Southern Ocean is primarily low in iron because it’s so far away from the dust sources, so any small amount of iron deposited there can cause a strong response,” Struton said.

Phytoplankton blooms can be seen from space and occur when there is an abundance of sunlight and nutrients, resulting in an explosion in population. The massive boom in the Southern Ocean occurred at a time of year when phytoplankton activity is usually minimal.

Satellite image showing tall, thin plumes of smoke from bushfires burning in Australia across the Pacific Ocean in January 2020
A satellite image showing tall, thin plumes of smoke from bushfires burning in Australia across the Pacific Ocean in January 2020. Photo: NASA Earth Observatory Bulletin/EPA

Researchers estimate the amount of carbon absorbed by phytoplankton cells as a result of reproduction to be equivalent to about 95% of emissions from wildfires in 2019-20.

In order to permanently remove this carbon from the atmosphere, phytoplankton cells must sink to the depths of the ocean and store there, Struton said.

There is a lot of energy and biomass recycling that occurs in surface waters. It is possible that much of this carbon that was initially absorbed may have been re-released to the atmosphere when the phytoplankton cells began to decompose or gobble up.”

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Struton said the team did not specifically look at the broader marine ecosystem effects of the Great Southern Ocean’s proliferation, but that a moderate increase in phytoplankton activity over several months could have an impact on fish populations.

Professor Martina Doblin, director of the Sydney Institute of Marine Science at the University of Technology Sydney, who was not involved in the research, said her team’s analysis during the fires confirmed higher concentrations of iron and other nutrients in bushfire smoke. compared to normal air pollution.

“The nutrient content would be from the plant and the soil material that was burned. These nutrients, which are normally found in the terrestrial system, ended up in the ocean,” she said.

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Preliminary data from Doblin’s own estuarine research “is consistent with this idea that aerosols can have effects on phytoplankton growth.”

The results come as a separate study, also published in temper nature, a more accurate estimate of the amount of carbon dioxide released from the 2019-20 wildfire season.

Using satellite data, an international group of researchers found that fires emitted 715 million tons of carbon dioxide between November 2019 and January 2020, exceeding Australia’s typical annual fire emissions and fossil fuel emissions by 80%. One previous estimate The figure was estimated at 830 million tons.

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