1. Why is a submersible needed to descend to the bottom parts of the ocean?

Explanation:

A submersible is referred to as watercraft. It's small in nature and it has been designed to operate underwater.

it has a pressurized hull which enables the submersible to withstand high pressure from water outside ,the pressure outside is greater than the pressure inside. so in other words the submersible is needed to descend to the bottom part of the ocean because the submersible has been built to withstand a very high water pressure in the deep ocean depth.

answer: - few nutrients

high pressure

low temperatures

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