Ocean Alkalinity Enhancement is a climate change mitigation strategy that can reduce the amount of CO₂ in our atmosphere. In this study we add three different sources of alkalinity to natural seawater to assess how these chemicals might change carbon partitioning within seawater. The alkalinity we added had little impact on the marine carbon system except that a 4-day exposure to ~1000 µmol kg^–1 alkalinity from calcium oxide addition can negatively impact the production of organic matter.