What is contributing to ocean acidification and why is this a problem?
Why You Should Care
Burning anything organic releases carbon dioxide. In the past 200 years, the amount of burning (from clearing land, fossil-fuel consumption, and natural sources) has increased dramatically, and the levels of atmospheric carbon dioxide have skyrocketed. Oceans act as “sinks” for atmospheric nutrients, so 30% of the released carbon dioxide has been soaked up the oceans.
In the ocean, the carbon dioxide reacts to form carbonic acid, which is lowering the pH of the ocean as a whole. This change in pH is called ocean acidification, and everything that lives in the ocean is adapted to a particular pH. As the ocean becomes more acidic, it produces changes small (slowing shell development of plankton) to large (killing coral reefs and changing nutrient cycles). What’s more, these changes all increase the production of carbon dioxide and produce a positive feedback loop that increases the impact.
Test Your Vocabulary
Select the correct term for each of the following definitions:
Term
Definition
The lowering of the pH of a solution.
Changes caused by an initial event accentuate that original event (i.e., changes brought on by warming lead to even more warming).
Changes caused by an initial event trigger events that then reverse the response (i.e., changes brought on by warming lead to cooling).
Colonies of tiny animals (coral) that produce a calcium-carbonate exoskeleton that over time build up to form large underwater structures (the reef) in shallow, warm, tropical seas.
Region where rivers empty into the ocean.
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1.
On the pH scale, what happens if the seawater pH becomes lower?
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2.
On the map of ocean pH, where are pH values the lowest preindustrial and lowest in the 2100 estimate?
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3.
On the graph that shows carbon dioxide and ocean pH, as atmospheric carbon dioxide increases:
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4.
To stop the increasing seawater carbon dioxide from rising more, we need to:
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5.
What happens to marine organisms' shells at normal carbon-dioxide levels?
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6.
At higher seawater carbon-dioxide levels, what happens?
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7.
What are some of the effects of less calcium carbonate in the oceans in 2100?
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Lower levels of calcium carbonate would create thinner shells for marine invertebrates and decrease the number of invertebrates. This would impact food webs and lower diversity as these communities contract.
8.
The scenario for oceans in 2100 is a positive-feedback effect. Explain how increasing CO2 leads to a positive-feedback loop.
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Positive-feedback loops have an initial change that creates a greater change over time. Here, the increasing CO2 levels lead to a lowering of pH. This change increases available acid, which dissolves calcium carbonate faster. This in turn leads to fewer organisms to take up the CO2 (they need it for their shells) and so there is even more CO2 in the seawater. The initial CO2 eventually leads to a greater level of CO2.
