Deakin Communicating Science 2016

EES 200/101

Ocean Acidification… Uh, what?




In my last post we investigated coral bleaching, and how this disastrous event is impacting the Great Barrier Reef right now. Today we will be looking at ocean acidification, which is one of the major events that causes coral bleaching and also impacts shelled marine life.

Despite what many people believe, acidification doesn’t mean that the ocean is toxic and corrosive all of a sudden! The term however it is scientifically correct and refers to any solution that has its pH decrease.

Ocean acidification is a process that occurs over a long period of time. This happens when the ocean absorbs carbon dioxide (CO2) which undergoes a series of chemical reactions that produce a high concentration of hydrogen ions (H+). The influx of hydrogen ions is what makes the water’s pH change and become more acidic. To counteract this, carbonate ions in the water react to neutralise the free hydrogen ions in the ocean.

Throughout the last century, the ocean has absorbed around 30 to 40% of the carbon dioxide in the atmosphere (Orr et al. 2001). The amount of carbon dioxide emissions in the atmosphere during this time has risen above natural levels, which is human-induced. Therefore, the ocean has also absorbed an increased, unnatural amount of carbon dioxide.

You could say that this is good news for us, because that means less emissions in the atmosphere! However, I’ll have to get you to pause that thought and think from a biocentric point of view. How does this affect marine wildlife?


Figure 1.1: Liittschwager D 2007. Images showing what happens to Pteropod shells when placed in a seawater that contains levels of pH and carbonate that are predicted to occur in 2100.


Corals and shelled animals such as marine snails and molluscs rely on carbonate and use this substance to undergo a process called calcification. This produces calcium carbonate which is a vital substance that maintains their skeletons and/or shell. If carbon dioxide is using carbonate, then there will be less product for calcifying organisms to make calcium carbonate from, and they will face high mortality rates due to their weakened structure. Animals that rely on reefs and shelled animals will be affected too, and their populations will dwindle.



Coral reefs have been found to face greater risk more than anything because reefs and their calcification ability are very sensitive to changes in carbonate saturation levels (Langdon and Atkinson 2005). The Great Barrier Reef has been predicted to see a decrease in calcification levels by around 30% by 2100 if anthropogenic (human-induced) emissions continue to unnaturally rise (Kleypas et. al 1999).


Figure 1.2: Liittschwager D 2007. Comparison of the oceans pH levels in 1995 compared to what is predicted to occur in 2100.

Scientists such as Dr Richard Feely, a senior scientist working for the US National Oceanic and Atmospheric Administration (NOAA), believe that the best way to reduce impacts of ocean acidification is by reducing carbon dioxide emissions. “In order for us to address ocean acidification on a global scale we would have to add two billion tonnes of calcium carbonate,” he said (Kieran J 2016).

“It’s just economically not feasible to do that so this is why we’re saying the most important thing we can do is reduce CO2 emissions right now and make sure [more acidification] doesn’t happen.” – Dr Richard Feely (Kieran J 2016)

The topic of ocean acidification has been discussed for a while but is not as prioritised as other climate change impacts. Sadly, not many people even know what it even is and deny it. I feel that it’s quite real, and the true facts are something that the public and Government should be more aware of before it’s too late.




  1. Kieran, J, 2016. ‘Acidic oceans are dissolving shells of tiny sea snails, researchers find’, ABC News, 2nd May, retrieved 3rd May 2016, <>
  2. Kleypas, J, Buddemeier, R, Archer, D, Gattuso, JP, Langdon, C, Opdyke, B. 1999 ‘Geochemical Consequences of Increased Atmospheric Carbon Dioxide on Coral Reefs’, Science 2, vol. 284, no.5411, pp. 118-120, retrieved 2nd April 2016, doi:10.1126/science.284.5411.118
  3. Langdon, C and Atkinson, MJ. 2005 ‘Effect of elevated pCO2 on photosynthesis and calcification of corals and interactions with seasonal change in temperature/irradiance and nutrient enrichment’, Journal of Geophysical Research: Oceans, no. 110(C9), retrieved 3rd April 2016, doi:10.1029/2004JC002576
  4. Liittschwager D 2007, Acid Threat, photograph, National Geographic, retrieved 3rd April 2016, <;
  5. Orr, JC, Maier-Reimer, E, Mikolajewicz, U, Monfray, P, Sarmiento, JL, Toggweiler, JR, Taylor, NK, Palmer, J, Gruber, N, Sabine, CL, Le Quere, C, Key, RM, Boutin, J. 2001 ‘Estimates of anthropogenic carbon uptake from four three-dimensional global ocean models’, Global Biogeochemical Cycles, no. 15, pp. 43-60, retrieved 2nd April 2016, doi:10.1029/2000GB001273

About Tegan

Just a small town university girl, living in a slightly intimidating yet exciting science world that's waiting to be discovered. Cat enthusiast and current student studying a Bachelor of Zoology and Animal Sciences.

One comment on “Ocean Acidification… Uh, what?

  1. Pingback: The Heated Future of the Great Barrier Reef | Deakin Communicating Science 2016

Leave a Reply

Please log in using one of these methods to post your comment: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Deakin Authors

%d bloggers like this: