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AP Enviro



Unit 9

9.7 Ocean Acidification

2 min readmay 29, 2020


Jenni MacLean

AP Environmental Science ♻️

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Image courtesy of Wikimedia

Acid Formation

Dissolving CO2 in seawater increases the hydrogen ion (H+) concentration in the ocean, and thus decreases ocean pH, as follows:
Ocean acidification is caused by the absorption of excess atmospheric CO2 into the ocean. As more CO2 is released into the atmosphere the oceans will continue to become more acidic. Humans are inadvertently causing ocean acidification by increasing atmospheric CO2 with the burning of fossil fuels and deforestation.  Over the last 200 years of global industrialization, ocean pH levels have dropped 0.1 pH units. The pH scale is logarithmic meaning that a change of 0.1 would translate to a 30% in the ocean acidity levels. 

Impacts of Changing pH

The increasing acid levels in the ocean have large negative implications on organisms whose bodies are made of calcium carbonate.  Corals and shelled creatures like snails and clams will not be able to form their bodies in the lower pH environment and will not be able to survive. In contrast to these organisms being negatively impacted, ocean plants like seagrass and algae tend to thrive in a CO2 rich environment.  These conditions, lack of adequate herbivores and exploding plant growth could create hypoxic, eutrophied environments. 
Scientists are predicting that at current CO2 production, ocean acidity could increase by over 100% in the next 100 years.  This change would present a significant challenge to marine organisms and impact those human populations that rely on them. 



Image courtesy of Wikimedia

One organism of concern is the pteropod.  These tiny pelagic snails make up the basis of the food chain for a wide variety of animals. Scientists have studied these organisms in ocean waters that simulate predicted acidity levels and their shells completely dissolve in less than 50 days.  The collapse of this species would have a domino effect on the organisms that rely on it for food. Whales, salmon and other pelagic organisms would most likely not survive the total collapse of pteropods.

Image courtesy of Wikimedia


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