Effects of increasing depth: Practice Questions

Which of the following describes the environmental conditions found at a depth of \(2000\text{ metres}\) in the open ocean?

In a typical open-ocean profile, the concentration of dissolved oxygen is usually highest near the surface. Which of the following best explains this observation?

Consider the vertical profile of the ocean. Why does temperature typically show the most rapid change (the thermocline) in the zone between \(200\)m and \(1000\)m depth?

Which of the following abiotic factors does not typically change as a direct result of increasing depth in the open ocean?

Explain why hydrostatic pressure increases as the depth of the ocean increases.

State how the water pressure changes as depth increases and identify the approximate rate of pressure increase in the ocean.

Using the relationship between temperature and gas solubility, explain why deep, cold water masses can often hold more dissolved oxygen than warmer surface waters.

Explain why the concentration of dissolved oxygen is typically highest in the surface layer of the ocean and describe one biological process that causes it to decrease at mid-depths.

As a research vessel deploys equipment into the deep ocean, several abiotic factors change significantly.
(a) State how the density of sea water generally changes as depth increases from the surface to the seabed.
(b) Identify the two main abiotic factors that contribute to this change in water density at great depths.
(c) Describe the trend in hydrostatic pressure as a submersible moves from the sunlight zone to the abyssal plain.
(d) Explain why the high density of cold, deep water is a critical factor in the formation of vertical ocean currents.

A marine research team collected the following data regarding abiotic conditions at different depths in the open ocean:
- Depth (\(0\text{ m}\)): \(100\%\) light, \(22^{\circ}\text{C}\), \(1\text{ atm}\) pressure.
- Depth (\(500\text{ m}\)): \(0.5\%\) light, \(10^{\circ}\text{C}\), \(51\text{ atm}\) pressure.
- Depth (\(1000\text{ m}\)): \(0\%\) light, \(4^{\circ}\text{C}\), \(101\text{ atm}\) pressure.

(a) Describe the step-by-step procedure for using a Secchi disc to measure the depth of light penetration in surface waters.
(b) Using the data provided, describe the relationship between depth and water pressure and explain the cause of this trend.
(c) Explain why dissolved oxygen concentration typically decreases as depth increases from the surface sunlight zone into the twilight zone.