How the Australian megafires created the Microalk continent


At the start of 2019-2020, Australia experienced the most serious wildfire in its history. Smoke found across the Pacific Ocean off the coast of Chile has had an unexpected impact on marine life.

A To study A few days ago, the scientific journal Nature published that these fumes caused the flowering of an impressive quantity of microalgae. The phytoplankton, as they are called, in an area larger than Australia, in the middle of the Southern Ocean, is also known as the “Antarctic Ocean”.

How can a cloud of smoke appear as a form of life? John Lord of the University of Tasmania, one of the co-authors of this study, answers this question.

“All types of smoke contain not only gases but also small solid particles”, explains the researcher. “It’s mostly organic, it’s parts of unburned wood. There is a little nitrate, a few meters of a molecule. There is also iron, which plays a fundamental role in this part of the ocean.

This water has a strong iron deficiency. So much so that if we add a small amount, it produces a strong phytoplankton response.

John Lord

The proliferation of these microorganisms after a fire is not an invention. Scientists have already noticed it, for example in California, in lakes or small streams. What is really new, however, is that the event took place on the high seas and is far from where the fire occurred.

What is really new in our study is that there is a distance of about 10,000 km between the Australian fire and the place where the phytoplankton are observed.

John Lord

Smoke rises from a bushfire in Australia in November 2019. [TOM BANNIGAN – AFP]Phytoplankton absorb carbon dioxide. Researchers therefore believe that this continent of algae, formed by the smoke from the fire, has absorbed all or part of the enormous amount of CO2 released into the atmosphere. The question is, what happened to this carbon dioxide after it was taken up by algae? There are two theoretical possibilities.

“The phytoplankton are eaten by small animals and the CO2 is released into the atmosphere,” explains John Lord. “So there is no buffering effect.”

The second option: “The phytoplankton forms clumps large enough to fall to the bottom of the ocean. This is called carbon sequestration, ”explains the marine researcher.

>> To read also: Summer forest fires around the world have recorded CO2 levels

Carbon finds its way to the bottom of the ocean and stays there for a long time. Thus, the algae can act as a shield against the greenhouse gas emissions caused by this fire.

For now, researchers working on satellite imagery are developing hypotheses without knowing what really happened to CO2. They couldn’t go and couldn’t answer all of their questions yet. But to see firsthand what happened, part of the research team plans to travel to a nearby boat.

Impact on marine life

There are a number of puzzles. One is the impact of other businesses. The area of ​​the South Seas where this phenomenon occurred is described as a marine desert. Not being able to eat much, lifestyles are rare there. Could the origin of algae have changed significantly for marine animals?

Here too, in the absence of direct observations made on the spot, it is difficult to answer. But researchers know it could happen. At the phytoplankton flowering event – we speak of “phytoplankton bloom” in French – there is indeed a reaction from the animal. As in this precise case, it is most positive in the open sea or when there is a high oxygen content. “When you notice a ‘phytoplankton bloom’ in the open sea, life appears,” says John Lord.

You have to imagine the desert, suddenly the grass appears. From there, insects, small animals, and the entire food chain will begin.

John Lord

If this is confirmed in the future, it can be said with certainty that it naturally ended well. The worst fire we have ever seen in Australia and on the planet allowed life to appear thousands of miles away, usually in a very uncomfortable area …

Radio subject: Grégory Plesse

Web adaptation: Friend

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