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?
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).
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.