The pelagic zone consists of the open ocean beyond coastal waters. It is divided into four subzones based on depth and light levels: (1) The epipelagic zone near the surface has enough light for photosynthesis. (2) The mesopelagic zone has limited light. (3) The bathypelagic zone is completely dark. (4) The abyssopelagic zone exists at the greatest depths. Organisms in each subzone have adapted to the unique conditions of their environment, such as light levels, pressure, oxygen levels and food sources. Phytoplankton and zooplankton are primary producers, while animals include birds, fish, marine mammals, and

1. Ocean Pelagic Zone
Amy Halstead and Hannah Basham

2. Ocean Pelagic Zone
The Ocean Pelagic Zone, sometimes referred to as the
Open Ocean Zone, is comprised of nearly the entire
ocean beyond the costal region. The word pelagic
comes from the Greek word pélagos, meaning open
sea. This region is purely comprised of saltwater,
contrasting it from the freshwater zone. Although
warm water currents run through the Pelagic Zone,
the water is generally cold: The average temperature
of the warmest subzone, the Epipelagic Zone, is 17°C,
or 68°F.

3. Subzones
The Pelagic Zone is divided into four subzones:
1)
2)
3)
4)
The Epipelagic Zone
The Mesopelagic Zone
The Bathypelagic Zone
The Abyssopelagic Zone
I. Pelagic - (1) Epipelagic (2)
Mesopelagic (3) Bathypelagic
(4) Abyssopelagic
II. Benthic - (5) Littoral, Sublittoral (6) Bathyal (7) Abyssal
(8) Ultra-abyssal | Note:
depths are in meters

4. Epipelagic Zone
The Epipelagic Zone is called the Sunlit Zone because it
is the topmost layer, comprised of the surface and
waters a small depth below; therefore, the sun
penetrates the water enough for photosynthesis to
occur. Because of the vastness of the Ocean Pelagic
Zone, about half of the world’s photosynthesis occurs
in this zone. The presence of sunlight in this zone and
the abundance of plankton causes most of the life
found in the Ocean Pelagic Zone to be found in this
subzone.

5. Mesopelagic Zone
The Mesopelagic Zone, also called the Twilight Zone,
extends from about 200 meters below the surface to
1,000 meters. Vision in this subzone is limited: Little
sunlight penetrates through to this zone, an
insufficient amount for photosynthesis. In this depth
range, oxygen is completely depleted from the water,
but organisms have adapted with highly efficient gills
and minimal movement. At this level, many of the
organisms are able to produce light themselves, or a
bioluminescent.

6. Bathypelagic & Abyssopelagic Zone
The Bathypelagic Zone (Midnight Zone) is completely
dark. No plant life can exist here and many of the
organisms that live here eat falling detritus from
above subzones or prey on other organisms in this
subzone. Some of the larger organisms are prey to
deep diving sperm whales.
The Abyssopelagic Zone (Lower Midnight Zone) was
once thought to be bottomless. Few organisms can
successful survive in the harsh environment, and
many of those that can have adapted to be
transparent and eyeless due to the extreme
darkness.

7. Bathypelagic & Abyssopelagic Zone

8. Pelagic Plants
The primary plant in the pelagic zone is phytoplankton,
a microalgae, fuelled by photosynthesis. Other plant
types are:
• Diatoms, single-celled phytoplankton
• Dinoflagellates, microscopic, single-celled algae
• Seaweeds, these plants float across the surface of
the ocean providing nutrients to other organisms.

9. Temperature & Pressure
The temperature in the Pelagic Zone varies greatly
depending on the depth, with the Epipelagic Zone
reaching up to 26°C and the Bathypelagic Zone falling
to temperatures as low as 2°C. Because of the depth
and water, pressure increases by great amounts in
each zone. Because of the variability of the
atmospheric conditions in the Ocean Pelagic Zone,
many of the organisms cannot travel between
subzones due to the environmental conditions.

10. Light
The amount light in each subzone varies because
sunlight is unable to penetrate the waters deep
enough to reach all levels.
• The Epipelagic Zone is the only subzone in which
enough light is available for photosynthesis.
• Some sunlight reaches the Mesopelagic Zone and
allows certain organism to hunt if their eyesight is
strong enough.
• The Bathypelagic and Abyssopelagic Zones are too
deep for any sunlight to reach; however, some light
may be available from bioluminescent organisms.

11. Depth & Location
The Ocean Pelagic Zone reaches down to a depth of 11
km (6.8 mi) at the lowest point and has an average
(mean) depth of about 3.68 km (2.29 mi). The depth
plays an important role: As depth increases, the
abundance of life decreases.
Water covers over 70% of Earth’s surface, with the
largest contributions to this fact being the oceans.
Because of this, the Ocean Pelagic Zone can be found
almost anywhere where there are not masses of
land.

12. Water Type
The water in the Ocean Pelagic Zone is always salty.
The salinity of the water ranges from 6 – 40 ppt. The
range can be attributed to evaporation rates, sea ice
formation, and freshwater supply rates.

13. Nutrients
Certain vital nutrients in the Ocean Pelagic Zone are in
small supply. The following elements, called limiting
nutrients, are recycled through marine plants:
• Nitrogen
•Magnesium
•Zinc
• Phosphorus
• Calcium
• Silicon
• Iron
• Copper

14. Animals
There are five main types of animals that live in the
Ocean Pelagic Zone:
• Birds
• Invertebrates
• Mammals
• Fish
• Reptiles

15. Pelagic Birds
Pelagic birds are birds that live on the open sea rather
than land or waters close to land. These birds feed
on crustaceans, forage fish, and squid.
• Atlantic Puffin
• Macaroni Penguin
• Sooty Terns
• Shearwaters
• Procellariiformes

16. Pelagic Invertebrates
Pelagic invertebrates play a huge role in the Ocean
Pelagic food chain. Photosynthetic zooplankton are
included in this group which are base of the food
cycle. Other invertebrates include:
• Jellyfish
• Crustaceans
(crabs, lobsters, prawns)

17. Pelagic Fish & Reptiles
Fish are by far the most abundant type of animal in the
Pelagic Zone. A majority of the fish live relatively
near the surface.
Pelagic reptiles include sea turtles and some species of
sea snakes.

18. Pelagic Mammals
The Pelagic Zone is home to many mammals, one of
which is the blue whale—the largest mammal on
earth. The three main types of mammals found in
the Pelagic Zone are whales, dolphins, and porpoises.
Because the oxygen concentration is much higher
near the surface, all Pelagic mammals live in the
upper region.

20. Animal Adaptations
The animals that live in the Pelagic Zone face conditions that are very
different from many other parts of the world, and therefore have
adapted to this environment:
• Mammals lungs collapse so they can dive down to greater depths.
• Deep sea fish have lung-like swim bladders to control their
buoyancy.
• Fish have developed specialized functions to keep their bodies from
equalizing saltwater through osmosis.
• Fish have blubber to protect them from the cold, as well as a
chemical in their blood to keep it following
• Organisms that live in the deep sea have adapted so they can with
stand the pressure, darkness, and cold—as well as the scarcity of
resources.

21. Works Cited
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Alexander, Constantine. "Phytoplankton Loss Could Spell Disaster for Marine ecosystems." No Fish Left. N.p., n.d. Web. 11
Oct. 2013.
Campbell, Neil A., and Jane B. Reece. Biology. San Francisco: Benjamin Cummings, 2002. Print.
"Deep Sea Photography." Deep Sea Photography. N.p., n.d. Web. 13 Oct. 2013.
Kennedy, Jennifer. "The Open Ocean - Pelagic Zone." About.com Marine Life. N.p., n.d. Web. 9 Oct. 2013.
"Natural History Photography." Natural History Photography. N.p., n.d. Web. 13 Oct. 2013.
"Oceanic Pelagic Biome." Oceanic Pelagic Biome. N.p., n.d. Web. 10 Oct. 2013.
Stenstrom, J. 2009. "Pelagic Biome" (OnLine) UntamedScience. Accessed Oct 12, 2013 at
http://www.untamedscience.com/biology/world-biomes/pelagic-biome
"The Structures and Adaptations to Marine Living - MarineBio.org". MarineBio Conservation Society. Web. Saturday,
October 12, 2013.
Woodward, Susan L. "Life Zones in the Ocean." Biomes of the World. Radford University, 2012. Web. 13 Oct. 2013.