Unit 9: Global Change: 4.58: ocean warming and acidification

Two main ideas:

Global warming is causing ocean water to expand, rising sea levels
Increased CO2 in the atmosphere is changing the pH of the oceans (ocean acidification)

Some lakes (confined, smaller bodies of water) have increased by 2°C or more
Oceans has warmed by 1.5-2°C
2.7°C in the top layers (!)
- Kyoto protocol: 5.2% decrease in greenhouse gases by 2012
- Paris climate Accord: 2°C max temp increase

Result:

fish migration, northwards

coral bleaching: mutualistic algae (zooxanthellae) dies
corals are sensitive to pH, temp, sedimentation, pollution, disease and salinity (few corals on windward shores of Hawaii due to freshwater runoff)
some genetic researchers are trying to create heat resistant corals (CRISPR) and other variants of zoozanthellae (A-C)

Ocean acidification:

CO2 + H2O <--> H2CO3 <--> HCO3- + H+

H2CO3 is carbonic acid

H+ joins with water to become H3O+ known as the hydronium ion (basis for low pH)

Screen Shot 2023-04-08 at 4.02.29 PM.png

Important:

As pH decreases, CaCO3 in corals dissolves (AP exam question last year) and creatures have a harder time absorbing calcium carbonate

Coral Bleaching:

Here’s how to read this:
The top formula is what you know already:
CO2 + H2O <-> H2CO3<-> H+ + HCO3-

The next bit is more complex:
Since there is lots of H+ in the ocean with acidification, it pulls CO3-- out of coral:

Follow coral from the left:
CaCO3—>Ca++ + CO3-
CO3-- + H+ —> HCO3-

This second part is what you may be asked about on the AP exam...

Thanks to Sammy Sudin for these cool posters:

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