Answer: low, though the large area occupied by the ocean supports a large number of producers like phytoplanktons, this is because the open ocean has a zone known as Epipelagic zone where photosynthesis can take place as a results of light penetration.
Open ocean is also called the pelagic zone, it is the area where the biggest marine animals are found because it is an area of the ocean that is outside the coastal area. Animals in this zone suffers from or are affected by prey, wind activity, pressure, water temperature, etc.