Wildfires Fuel Massive Ocean Algal Blooms
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- Wildfires release iron-rich smoke and ash that settle on oceans and lakes, providing nutrients that can trigger rapid algal growth, according to environmental research.
- Algal blooms can grow so large they are visible from space, as seen after Australia’s 2019–20 bushfires, when a bloom spanned an area larger than the country itself.
- Iron from wildfire ash acts as a potent catalyst in marine environments where the element is typically scarce, stimulating phytoplankton growth even in small concentrations.
- Dead zones form when algal blooms die and decompose, consuming oxygen in the water and threatening aquatic life, a consequence increasingly linked to post-fire runoff and deposition.
- Australia’s 2019–20 'black summer' bushfires injected vast plumes of ash into the Southern Ocean, leading to one of the most dramatic wildfire-triggered algal blooms ever recorded.
- Smoke can both promote and inhibit algal growth—while iron fuels blooms, toxins in smoke and reduced sunlight from dense clouds can suppress photosynthesis, creating complex ecological effects.
Why it matters: Marine ecosystems now face a newly amplified threat from wildfires, which are increasing in frequency and intensity. The iron-laden ash they deposit can disrupt ocean chemistry over vast areas, triggering blooms that deplete oxygen and harm fisheries—altering food webs and coastal economies dependent on them.
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