9.7 - Ocean Acidification

Question 1

Ocean Acidification

Answer 1

• Increased CO2 in atmosphere ➡️ increased ocean CO2 (direct exchange)
• CO2 combines with ocean water to form carbonic acid (H2CO3)
• Carbonic acid dissociates into Bicarbonate ion (HCO3-) and H+ ion

Question 2

Calcium Carbonate & Marine Organisms

Answer 2

• Marine org. that make shells use calcium (Ca+) and carbonate (CO32-) ions to build their calcium carbonate shells (calcification)
• CO2 increase & ocean acidification makes carbonate ions less available
• Carbonic acid ➡️ increased H+ ions which bond w/carbonate to form Bicarbonate (HCO3-)
• Marine shells breakdown as pH decreases and carbonate ions are less soluble in ocean water
• Fewer carbonate ions = less calcification; weaker shells of coral, mollusks, and urchins

Question 3

Climate Change and Ocean Acidification

Answer 3

• Anthropogenic causes for ocean acidification: fossil fuel combustion (CO2), deforestation (CO2), and coal/gas combustion (NOx/SOx → acid precip.)
• CO2 increase directly correlated with ocean acidification
• Inverse relationship b/w atm. CO2 & ocean pH (low pH = more acidic)
• Ocean pH has decreased from 8.2 to 8.1 in past 150 years; could decrease to 7.8 by 2100
• *pH = log scale so 8.2 to 8.1 = 30% decrease