Zones of the Marine Environment
Name: ______________________________________________
The marine environment makes up more than 70% of the Earth’s surface. That and its complexity make it a difficult
system to classify. The oceans have two principal life zones: the coastal zone and the open sea. The coastal zone is
relatively warm, nutrient-rich shallow water that extends from the high-tide mark on land to the edge of the continental
shelf. The continental shelf is the submerged part of the continents. The coastal zone represents less than 10% of the
oceans, however, it contains 90% of all ocean species. This zone is the source of most of the ocean’s productivity per
acre. The open ocean extends outward from the edge of the continental shelf. The open sea contains about 90% of the
world’s ocean area, but has only about 10% of all ocean organisms. Your goal today is to examine and characterize the
physical characteristics of these zones in the coastal and open ocean regions.
1. What percentage of the ocean area is considered coastal? What percentage of life is found in the coastal zones?
2. What percentage of the ocean area is considered open ocean? What percentage of life is found in the open
ocean?
3. Which area is more productive?
The marine environment is a very
large and complex system. One way
to designate particular marine
environments is based on physical
characteristics like temperature,
depth, light and DO. The
environments in which the pelagic
and benthic organisms live can be
grouped into four major ecological
zones: littoral (intertidal) zone,
sublittoral zone, bathyal zone and
abyssal zone. Examine the location
of these zones in Figure 1.1.
4. Describe how the littoral
and sublittoral zones are
different from the bathyal
and abyssal zones based on
the physical characteristics
listed above.
The intertidal zone is part of the seashore located between high and low tide. Organisms of the intertidal zone are
covered with salt water at high tide and uncovered at low tide. In addition to withstanding the change in water level,
they must also withstand the pounding of the surf. This zone is crowded with life since nutrients and oxygen are readily
available. Look at Figures 1.2 and 1.3.
5. Why are nutrients
and oxygen in high
concentrations in
this zone?
6. Why does the
intertidal zone have
great variation in
temperature?
7. Besides the
intertidal zone,
where else do you
see lots of
nutrients? Why?
8. Describe where you
see high or low
concentrations of
salts. Why do you
think that is?
9. The salinity of the intertidal zones will actually vary depending on several factors:
a. How does river run-off affect salinity?
b. How does precipitation affect salinity?
c. How does evaporation affect salinity?
10. Why is the intertidal zone a region of constant change and how does this affect the organisms that live there?
The sublittoral zone is the zone from the low tide mark to the edge of the continental shelf (seen in Figure 1).
11. How is the sublittoral zone different from the intertidal zone?
12. The bathyal zone is the region from the continental shelf to the start of the abyssal zone; down to about 2,000
meters. The abyssal zone refers to the abyssal plains and is about 2,000-6,000 meters. The hadal zone is mainly
deep ocean trenches and is deeper than 6,000 meters. What factors likely change as you travel from the bathyal
to abyssal to hadal?
13. Fill in the table using the figures that show the abiotic factors and location of the zones.
Marine Zone
Location
Light
Salinity
Oxygen
Nutrients
Temperature Organisms
Intertidal
(littoral)
Sublittoral
Bathyal
Abyssal
14. Some of these zones are located in the photic zone where light intensity is great enough for plants and
phytoplankton to perform photosynthesis. Which of the four zones would be included in the photic zone?
15. Which zones are located in the aphotic zone where light is absent? What organisms would not be found in
these zones?
16. Marine organisms can be assigned to groups based on depth and lifestyle. For example an animal may be
considered bathypelagic. What does this mean?
17. Describe what might be difference about animals that are bathypelagic and bathybenthic.
18. Which of the zones will be most impacted by pollutants from watersheds of rivers?