What are the potential impacts on marine life from the Australian bushfires?

After months of extreme burning and a resulting ecological crisis that has caught the attention of the entire world, the Australian bushfires are starting to die down. However there may still be some serious problems to follow in the marine environment surrounding the continent.

Distressing images like these have dominated the news in recent weeks as flames rip through t Australia 

There has been no escaping it in recent weeks. Extreme conditions provided by human caused climate change has caused months of devastating bushfires that are only just coming to an end thanks to heavy rain sweeping over the country. And whilst there has been billions of dollars’ worth of damages and loss of life, it is the natural environment and wildlife in Australia that has ultimately paid the price. Researchers from the University of Sydney have estimated that as many as a billion animals have died as a result of the fires and experts also believe entire species are likely to have been wiped out completely. The grief of this loss has been felt around the world as media outlets from across the planet have shared distressing images of burnt koala bears clinging to firemen and kangaroos fleeing from the flames in fear. But whilst this awful tragedy unfolds on land there are also likely to be some worrying knock-on effects to the oceans and marine life surrounding Australia as well.

Acidic smoke

You only have to of turned on your TV or looked at your phone over the last few weeks to see the dark pillars of smoke towering over Australia, but where is it all going? Unfortunately the answer for most of it, is into the oceans. The Australian continent is surrounded by the sea which acts like a massive carbon sponge soaking up all the CO2 from the air and trapping it in the marine environment. This isn’t anything new. Our oceans have absorbed the majority of the emissions we have produced over the last century, but that has come at a big cost. As dissolved CO2 is absorbed by our oceans it has turned their waters increasingly acidic.

smoke over water
Smoke from the bushfires has been blown over the ocean surrounding Australia’s East coast and towards the Great Barrier Reef


Ocean acidification already affects a majority of marine life, but those hit hardest have been the ‘calcifiers’ like corals, crustaceans and molluscs who use calcium carbonate to build their shells and skeletons. Increases in acidity seriously impact these animals ability to do this and so the structures they are building are far more weak and easy to break. Although this has been happening for years a massive dump of fresh CO2 from the forest fires is likely to create some big problems. In particular it raises a lot of red flags about the Great Barrier Reef whose corals are already struggling from rising temperatures and are particularly susceptible to bleaching caused by acidification. As well as the thousands of species who depend on the reef for their survival, many of which can’t be found anywhere else.

Toxic ashes?

Of course smoke isn’t the only thing that the flames have been sending into the air. Where there is fire there is also ash and the bushfires have created absolutely tonnes of it, which like CO2 has found its way into the ocean. In fact there has been so much of the stuff in the sea that entire beaches have been turned black as it has washed back onto the shore (see video below). On the face of it ash seems like less of an issue than CO2, after all regular ash can’t acidify waters and will have limited impacts on marine life. The problem is that this isn’t any ordinary ash, because as buildings, cars and even towns have been engulfed by the flames the ash they produce have become enriched with heavy metals.

Due to the large array of different chemicals and metals that will end up in Australian waters, it is hard to predict what effects they will have on marine life. Although in reality it is unlikely they will be anything good. One of the big fears is that it may have a similar effect to nutrient run-off in river basins which is known to cause phytoplankton blooms. This is when an increase in nutrients, in this case from enriched ash, causes phytoplankton to rapidly multiply and spread over a large area. Whilst this may sound good like a good thing, it can actually seriously reduce the available oxygen in the waters below the blooms making them toxic to all manners of marine life. Most marine organisms will also have never come into contact with the sorts of elements being introduced to their environment so we have little way of knowing how they will be effected.

Only the beginning

At a time like this it is hard to picture any impacts the bushfires may have on the marine environment which are as comparable to the major devastation we have seen on land. However not only will the fires have a big impact beneath the waves, it is likely to just be the beginning. As human caused climate change accelerates in the future the conditions needed for these fires occur will only become more common. This makes it important to find out and monitor how the Australian marine life copes with these changes. There is already research underway following the extreme fires in California and unfortunately even more places will start to experience these problems in the near future as well. This is an area of science that will be important in the coming decades and so we must make sure we use this opportunity to learn as much as we can.

red skies
Red skies caused by the fires stretch across the coastlines of Australia, they are likely to become a lot more common in the future

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