Final answer:
The two sources of oxygen in the open sea are photosynthesis by marine organisms and dissolved oxygen from the atmosphere.
Step-by-step explanation:
The two sources of oxygen in the open sea are photosynthesis by marine organisms and dissolved from the atmosphere.
Photosynthesis is the process by which plants, algae, and some bacteria convert carbon dioxide and water into glucose and oxygen.
Photosynthesizing organisms, including phytoplankton, contribute to the production of oxygen in the open sea.
Dissolved oxygen refers to oxygen that is physically dissolved in the water.
It comes from the exchange of gases at the water's surface with the atmosphere.
Fish and other aquatic organisms extract dissolved oxygen from the water through their gills for respiration.