Science & Technology

Australian wildfires contributed to large-scale algae outbreaks in the Southern Ocean

Eucalyptus forests burned down by wildfires in Australia in 2019 and 2020 Larger than West Virginia.. They emit more carbon than the whole country produced in 2018, sending 20 miles of smoke into the air, Montana-sized atmospheric vortex..

Then, according to a new study published, the smoke did something even more unexpected. Today is Nature: It fell into the Antarctic Ocean in eastern Australia, causing a month-long blue-green algae. Flowering spanned thousands of miles and had uncertain effects on both marine life and global emissions. It shows that we are just beginning to understand the global ripples of climate change.

“When you look at the images of wildfires, the environmental impact of these fires on the local ecosystem is very clear,” said Nicholas Casale, a biogeochemist and author of the paper at Duke University. increase. “The surprise to me is how these wildfires can affect marine ecosystems thousands of kilometers away.”

Blue-green algae are short-term population explosions of small sea plants. They usually occur when waterways are flooded with certain important and rare nutrients. Algae devour all their food, grow rapidly, and die. When they rot, they suck oxygen out of the water.

Public health authorities Warned Regarding the potential for algae to develop after wildfires in inland North America, as fires can choke streams, lakes, and reservoirs with ash and dead plants. And when algae bloom in that nutritious soup, it can be fatal. Past weekIt seems that three dogs died along the Columbia River in Washington after playing with algae water.

However, this is the first time an algae explosion in the open ocean has been associated with a wildfire. At sea, algae can directly poison other organisms by excreting toxins (often called “red tides”). Or it can suffocate marine life as it rots. Algae outbreaks are often caused by fertilizer contamination as follows: Dead zone at the mouth of the Mississippi River..But the record toxic flowers on the west coast in 2015 Caused by unusually warm water, 1997 events that suffocated coral reefs It was related to a forest fire in Indonesia.

In this case, researchers believe that growth was caused by iron in the smoke. The Antarctic Ocean contains many other essential minerals needed for algae to grow, but iron is relatively deficient. Those that do not exist come from the depths of the ocean, melted ice, or dust that has fallen to the surface of the ocean. “Delivery [iron] The authors write that it is believed to be an essential driver of algae growth in these areas.

[Related: Maggots and algae could be the sustainable snacks of the future]

Satellite images of smoke showed that soot had fallen over a larger area than the entire Australian continent and was particularly heavy in two locations: the ocean south of Australia and thousands of miles east of offshore South America. ..

From October to April, algae began to grow in the area, followed by soot peaks and flowers.

“The scale is considerable,” said Weiyi Tang, one of the lead authors of the study and a biogeochemist at Princeton University. “The affected regions are beyond the regions of Australia.”

The flowers were so large that the authors estimate that they would absorb 50-150 percent of the carbon released by the actual fire. This may mean that the blue-green algae actually offset the impact of the fire on the climate.

“How much was the Holy Grail offset?” Says Kasar. “But we don’t know.”

If the algae are on the surface, their carbon will quickly return to the atmosphere. However, when it sinks, carbon is trapped on the ocean floor.

To understand that, scientists need to move to the flowering area and measure the amount of gunk that actually falls to the ocean floor. Tang and Cassar have such a swift response in the future.

It is not yet clear what flowers mean for marine life throughout the Southern Ocean or around the world.according to Studies published earlier this year, The area is already home to the largest algae on the planet. As it becomes more common in climate change, these plants can absorb important nutrients that fertilize other parts of the ocean.

“The Antarctic Ocean is a really important part of the world,” says Kasar. “It has a disproportionate effect on our climate. A large amount of anthropogenic heat is in the Antarctic Ocean and is anthropogenic carbon. Therefore, changes to it can affect our global climate. There is sex. “

However, the author also notes that Australia has experienced wildfires before, but has never seen this kind of large-scale flowering. It may be because the fire was so big, or because it was consistent with other environmental cycles, such as fine weather and good wind conditions.

“The marine system had to have the perfect conditions to accommodate the higher supply of aerosols,” says Tang.

Conditions may be met in similar ways elsewhere in the world. “There may be other places to deal with wildfires,” says Tang. “We’re really trying to look better.” The oceans off the coast of North America, Siberia, Africa and the Amazon can all be changing in completely unknown ways.

Australian wildfires contributed to large-scale algae outbreaks in the Southern Ocean Australian wildfires contributed to large-scale algae outbreaks in the Southern Ocean

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