Summary
Sunlit, twilight and midnight zones differ in light, temperature and pressure and support different life.
In depth
Epipelagic (0 to 200 m, photosynthesis), mesopelagic (200 to 1000 m, twilight), bathypelagic (1000 to 4000 m, dark), abyssal and hadal. Pressure increases by 1 atmosphere per 10 m. Vertical migration is the largest daily movement of biomass.
Light penetrates only to about 200 m (euphotic zone). Temperature drops sharply in the thermocline. Deep life depends on food from above.
Example: benthic zone describes the sea floor at any depth.
Ocean life is arranged by depth. The epipelagic (sunlight) zone reaches about 200 m and has enough light for photosynthesis; the mesopelagic (twilight) zone to about 1000 m has dim light and many vertically migrating animals; the bathypelagic (midnight) zone to 4000 m is dark, cold and under high pressure; the abyssal and hadal zones lie below.
Pressure rises by one atmosphere every 10 m. Temperature drops sharply at the thermocline, and most deep water is near 2 to 4 °C. Horizontally, the neritic zone covers continental shelves and the oceanic zone covers open water; the benthic zone is the seafloor.
Example: lanternfish rise to the surface at night to feed.
Key idea: light is the main limit to primary production.
Frequently asked questions
What is Ocean Zones?
Sunlit, twilight and midnight zones differ in light, temperature and pressure and support different life.
Which area of biology covers Ocean Zones, and how advanced is it?
Ocean Zones is one of the 54 topics in Marine & Environmental Biology. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Biological Pump, Oceans, Upwelling.
Can you give an example of Ocean Zones?
Lanternfish rise to feed near the surface at night.
What should I learn before Ocean Zones?
Ocean Zones is a Beginner topic, so no earlier topic is required. Other Beginner topics in Marine & Environmental Biology that pair well with it include Oceans, Plankton, Coral Reefs.
What topics are related to Ocean Zones?
The closest topics to Ocean Zones are Biological Pump, Oceans, Upwelling, Hydrothermal Vent Ecosystems. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Ocean Zones?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Ocean Zones. To practise the whole of Marine & Environmental Biology, use the Marine & Environmental Biology quiz.
How is Ocean Zones different from Biological Pump?
Ocean Zones: Sunlit, twilight and midnight zones differ in light, temperature and pressure and support different life. Biological Pump: Sinking organic matter transports carbon from surface waters to the deep ocean. Read both side by side and note what each one explains.
How should I study Ocean Zones step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Biological Pump and explain the difference aloud. Finally, take the Marine & Environmental Biology quiz and come back to this page for any question you miss.