Ocean acidification occurs when CO2 dissolves in seawater, forming carbonic acid and releasing H+ ions, lowering ocean pH. Which statement best reflects this phenomenon?

Ocean acidification occurs when CO2 dissolves in seawater, forming carbonic acid and releasing H+ ions, lowering ocean pH. Which statement best reflects this phenomenon?

• A. Rising pH and stronger shells
• B. Lower pH and weaker shells
• C. No change in calcification
• D. Increased salinity

Answer: (B)

Ocean acidification is about how adding CO2 to seawater changes its carbonate chemistry. When CO2 dissolves, it forms carbonic acid and releases hydrogen ions, which lowers the water’s pH. That same shift reduces the amount of carbonate ions available for calcification, making it harder for organisms like mollusks and corals to build calcium carbonate shells. With less carbonate and more hydrogen ions competing, calcification slows and shells tend to be weaker or more prone to dissolution. The statement describing lower pH and weaker shells captures this direct link between the chemical change and its biological impact. Increased salinity isn’t driven by CO2 dissolution, and calcification does change under acidified conditions, so those options don’t fit.

Ocean acidification is about how adding CO2 to seawater changes its carbonate chemistry. When CO2 dissolves, it forms carbonic acid and releases hydrogen ions, which lowers the water’s pH. That same shift reduces the amount of carbonate ions available for calcification, making it harder for organisms like mollusks and corals to build calcium carbonate shells. With less carbonate and more hydrogen ions competing, calcification slows and shells tend to be weaker or more prone to dissolution. The statement describing lower pH and weaker shells captures this direct link between the chemical change and its biological impact. Increased salinity isn’t driven by CO2 dissolution, and calcification does change under acidified conditions, so those options don’t fit.