The bush fires that scorched Australia in the summers of 2019 and 2020, destroying millions of dollars’ worth of property and killings millions of wildlife, have also caused a 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 transported nutrients such as iron thousands of miles away into the Southern Ocean.
This has caused a massive bloom of phytoplankton, a group of algae crucial for ocean ecosystems as well as for the world’s carbon cycle. They are the biggest source of oxygen in the world, responsible for over 50 percent of the world’s oxygen production.
The blooms cover an estimated area larger than that of Australia according to the study. Richard Matear, a co-author of the study and a climate and oceans scientist at Australia’s Commonwealth Scientific and Industrial Research Organisation, has said that events of natural disasters like bushfires can have a profound impact on ecosystems further afield from them. He added that this particular example shows how the terrestrial biosphere is interconnected to the ocean in a rather interesting way.
A satellite image showing clouds of smoke and ash from Australian wildfires sweeping towards the Southern Ocean. Credit: National Institute of Information and Communication Technology, Japan
Algal blooms occur when phytoplankton rapidly multiply into massive, hundreds of kilometers wide congregations. Most algal blooms are large enough to be visible from space.
Phytoplankton feeds off nutrients in the ocean, such as iron to perform photosynthesis. Naturally, these blooms are seasonal, but they can also occur when pollutants in the ocean can trigger rapid algal reproduction. These pollutants can be naturally in the form of volcanic ash or this case ash from bushfires. Man-made pollutants can also trigger algal growth.
Despite the crucial function that phytoplankton serves for ocean ecosystems, unnatural algal spikes can harm marine ecosystems. These plankton blooms can cover the ocean surface for miles and are toxic to marine animals. According to a paleobiologist from the Swedish Museum of Natural History, a single explosive bloom can potentially wipe out thousands of animals in a few days, leaving “dead zones”.
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