Assess students' understanding of ocean acidification causes (anthropogenic CO2 uptake), core carbonate-system chemistry (pH, CO2 ⇌ H2CO3 ⇌ HCO3− ⇌ CO32−, and aragonite/calcite saturation state), and ecological impacts on shelled organisms and coral reefs. Quiz items should include concept explanations, interpretation of simple chemical equilibria and graphs, qualitative reasoning about how rising CO2 reduces carbonate ion availability and calcification, and short analyses of biological consequences and potential mitigation/adaptation strategies.