Answer:
Carbon dioxide from the atmosphere dissolves in the surface waters of the ocean.
Step-by-step explanation:
Photosynthesis by tiny marine plants (phytoplankton) in the sunlit surface waters turns the carbon into organic matter.
Respiration from aquatic life lowers the carbon dioxide concentration in the oceans. Carbon dioxide dissolves more readily in water than in the atmosphere. Plankton at the surface funnel carbon from the atmosphere to the ocean.