Smoke from Australian bushfires has triggered a giant plankton bloom in the Southern Ocean

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The bush fires that scorched Australia in the summers of 2019 and 2020, destroyed millions of dollars’ worth of property and killed millions of wildlife, also caused massive algal bloom in the Southern Ocean, just a few thousand miles away.

According to a study published in the journal Nature, the thick smoke and ash from the bushfires carried nutrients such as iron thousands of kilometers into the Southern Ocean.

This has resulted in massive blooms of phytoplankton, a group of algae that are vital to ocean ecosystems as well as the world’s carbon cycle. They are the largest source of oxygen in the world and are responsible for over 50 percent of the world’s oxygen production.

According to the study, the flowers cover an estimated area larger than that of Australia. Richard Matear, co-author of the study and a climate and ocean scientist with the Australian Commonwealth Scientific and Industrial Research Organization, said natural disasters like bush fires can have profound effects on ecosystems further away. He added that this particular example shows how the terrestrial biosphere is connected to the ocean in quite interesting ways.

A satellite image showing clouds of smoke and ash from Australian forest fires sweeping towards the Southern Ocean. Credit: National Institute for Information and Communication Technology, Japan

Algal blooms occur when phytoplankton rapidly multiply into massive clusters hundreds of kilometers wide. Most algal blooms are large enough to be visible from space.

Phytoplankton feed on nutrients in the ocean, such as iron, to carry out photosynthesis. These blooms are of course dependent on the season, but can also occur when pollutants in the sea can trigger a rapid multiplication of algae. These pollutants can be naturally in the form of volcanic ash or, in this case, ash from bushfires. Artificial pollutants can also trigger algae growth.

Despite the critical role phytoplankton plays in ocean ecosystems, unnatural algae spikes can damage marine ecosystems. These plankton blooms can cover the ocean’s surface for miles and are poisonous to marine animals. According to a paleobiologist from the Swedish Museum of Natural History, a single explosive bloom can wipe out thousands of animals in a matter of days, leaving “dead zones” behind.

Cover picture: Shutterstock


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