Answer:
- few nutrients
- high pressure
- low temperatures
Step-by-step explanation:
1. Few nutrients: open-ocean zone is located way far from the land, which is the main source of the essential nutrients.
2. High pressure: pressure increases by 1 atmosphere for every 10 meters increase in depth.
3. Ample sunlight: a large fraction of the sunlight is reflected back to the atmosphere from the sea surface.
4. Varying salinity: below the thermocline, the water is isolated from the atmosphere so the salinity remains stable over the year.
5. Low temperatures: the temperature of open-ocean zone ranges from a low of -2°C to an average of 17°C.