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The algal bloom caused by Australian bushfires

The 2019-2020 Australian bushfire season burnt over 18 million hectares of land, emitted over 250 million tonnes of CO2 and lead to high levels of PM2.5. However one of its impacts that was overlooked until recently, was the effects that it had on the algal population in the sea.

How are wildfires causing algal blooms in the sea?

Algal blooms are often associated to issues such as nitrogen or phosphorous run offs from fertilisers and sewage effluent. As we know previously wildfire smoke is able to spread across vast distances. A study by the journal Nature concluded that smoke from the 2019 Australian wildfires was carried out to sea leading to an algal bloom. Researchers explained that this was due to the presence of iron in the smoke, or what is also known as pyrogenic aerosols. The aerosols are light enough to be carried by the wind, as it falls it fertilises the water and provides sufficient nutrients to cause algal blooms.

Figure 1: Photo by Japan’s National Institute of Information and Communication Technology showing the smoke and ash emerging from the Australian bushfires over the Oceans in early 2020

What are the effects of the algal blooms?

It is unclear what the effects are. On one hand, the silver lining is that Phytoplankton is able to absorb CO2. Phytoplankton is microscopic organisms that form the backbone of ocean and freshwater ecosystems. They like land plants contain chlorophyll and photosynthesize to obtain energy, through this process CO2 is absorbed and oxygen is released.

It may seem on the surface, that the more algal blooms the better. However, this might not be the case, as the CO2 emissions from wildfires are disproportionate, to even what the biggest algal blooms can absorb. Furthermore, the effects that algal blooms can have on the ecosystem can be detrimental, as an abundance of algae can deplete oxygen levels and lead to the deaths of marine life. Algae bloom in northern Norway in 2019, leading to the death of 8 million farmed salmon. One may wonder how oxygen is depleted when it is released as a product of photosynthesis by the algae. During night and periods of low light intensity, oxygen is required for respiration by the algae. Thus, an overabundance of algae may lead to oxygen depletion.

Although the same drastic effects haven’t been seen in Australia, it is crucial that these precious marine ecosystems are left undisturbed. Whether or not, these algal blooms are beneficial, the damage caused by the 2019-2020 bushfires or any wildfires is not worth the price to pay.

By CK Yu

CK Yu is currently a Biomedical Science undergraduate student, who is also interested in technology and how it can be used to solve problems, whether it may be in the medical field or for the better of the world.

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