The open ocean is the most extensive biome on Earth, covering over 360 million km2. It is divided into vertical zones based on factors like depth, light penetration, temperature, and pressure. The pelagic zone extends from the sea surface and is divided into epipelagic, mesopelagic, bathypelagic, and abyssopelagic zones. Phytoplankton in the epipelagic zone perform photosynthesis, while organisms in deeper aphotic zones rely on chemosynthesis. Human activities like overfishing, pollution, climate change, and habitat destruction threaten ocean ecosystems.

1. Ocean
The open ocean is the most
extensive biome on earth.

2. Ocean
• The open oceans or pelagic ecosystems are
the areas away from the coastal boundaries
and above the seabed. It encompasses the
entire water column of the seas and the
oceans and lies beyond the edge of the
continental shelf. It extends from the tropics
to the polar regions and from the sea surface
to the abyssal depths. It is a highly
heterogeneous and dynamic habitat.

3. Geography
• The world ocean covers over 360 million km2
of earth’s surface and consists of one
continuous, interconnected mass of water.
This water is spread among three major
ocean basins:
 Pacific
Atlantic
Indian

5. Classification of the Marine
Environment Classification of the
Marine
• Marine scientists divide the ocean
environment into zones. Marine Zones are
areas with uniform physical conditions.
Common classifications are based on physical
factors such as
depth, light, temperature, salinity, etc. The
most basic zonation is based on substrate:
exclusively water environment (pelagic) and
bottom interface (benthic).

6. • The pelagic zone is divided by depth
into: nerithic zone, which includes the
nearshore areas over the continental shelves;
and the oceanic zone,the areas seaward of
the continental shelves. The oceanic zone
is further divided into epipelagic zone (same
as photic
zone), mesopelagic, bathypelagic, and abysso
pelagic zones. Abyssopelagic zone is water in
the deep ocean trenches. The last three
zones are all at aphotic depths.

7. The shallowest benthic environments
(below the neritic zone) are:
• * Supralittoral - bottom substrate above high
tides (not part of ocean).
* Littoral - bottom substrate within the
intertidal zone.
* Sublittoral - bottom substrate below the
lowest tides.

8. Beyond the continental shelf break
are:
• * the Bathyal zone (ocean bottom down to
the abyssal plain or the average depth of the
ocean floor),
* the Abyssal zone (from 4,000 - 6,000 m
depths), and
* the Hadal zone representing the deepest
ocean bottom in the deepest trenches.

9. • Physical factors affecting Marine Life
Any factor of the physical environment that
affects the survival of marine organisms are
physical factors. These physical factors form
barriers between various communities of
marine organisms. The most important of
these are:

10. • Light
the primary importance of light is photosynthesis.
– The depth of penetration of light will determine the birth of a food
chain sequence.
Most marine organisms live in the well-lighted neritic zone and in the
epipelagic zone where food is abundant.
Some deep water fish use light for body orientation (even dim light),
feeding, and predator avoidance.
Some marine organisms produce their own light by biochemical reaction,
known as bioluminescence. Organisms typically living at depths within the aphotic
zone, (or those that are active at night) such as squids, some fish and shrimps, are
bioluminescent. They use light to see, to communicate, and to facilitate predation.

11. • Temperature -
the metabolic rate of organisms increases
with the temperature of their bodies.
Temperature range in the oceans is -50 to
40 C, except around hydrothermal vents where
temperatures can be as high as 110 C. So in
general, marine organisms live within a much
narrower temperature range than land
organisms.

12. • Dissolved Nutrients -
Nutrients are chemical substances that
play vital role in the growth and general
functioning of an organisms.
In the oceans, nutrients in short supply
are nitrogen (N) and phosphorus (P).

13. • Salinity - marine salinity varies from 6 - 40
ppt. This large range is controlled by
evaporation rates, sea ice formation, and
freshwater supply rates. The greatest impact
of salinity variation is at the ocean
surface, whereas deeper ocean salinity
(below the halocline), is far less variable.
Salinity affects the tissues of organisms
thorough osmosis.

14. • Most marine organisms are isotonic and no
special salinity problems are imposed on
them. But marine fish (bony fish)
is hypotonic, that is, their body fluids are less
salty than seawater. Hence, they are
constantly losing water and are threatened
by dehydration.

15. • Dissolved gases - gases dissolve more in cold
water than in warm water. The two most
important gases to marine organisms are:
O2, and CO2. O2 is essential for respiration
and CO2 for photosynthesis. O2 is less
soluble is seawater and tends to be in
abundance only in surface waters. Why? CO2
is more soluble in seawater and its
concentration increases with depth. Why?

16. • Planktons
In the biosphere, nearly all living organisms
use converted solar energy as the primary
fuel to facilitate their daily activities.

17. • In the oceans, the organisms that capture
solar energy and bind it into usable energy
for their own use as well for the use of other
organisms are known
as phytoplanktons and seaweed.

18. • Planktons represent a community of
organisms associated solely on their mode of
locomotion. All planktons drift or swim very
weakly, moving around with the currents or
waves. Many can move vertically through the
water column.

19. • In general, planktons live in the euphotic
zone, in the upper layers of the open ocean
down to the compensation depth. This is the
depth to which 1% of surface light penetrates
and photosynthetic organisms produce just
enough carbohydrate to serve all the
organisms' needs (zero net productivity).
Although the compensation depth is
variable, it averages about 150 m from the
ocean surface.

20. • Planktons are generally diverse, ranging from
those with soft, gelatinous bodies with little
or no hard parts, to those encrusted in hard
parts. The common planktons are drifting
jellyfish, arrowworms, single-celled
organisms, some crustaceans, a few marine
mollusks, some algae, etc. Hence both
animals (zooplanktons) and plants are part of
the plankton community.

21. • There are, at least, eight major types
of phytoplanktons (the plant variety)
responsible for the nearly all the oceans
primary productivity. These phytoplanktons
are mostly single-celled, microscopic
organisms that
include diatoms, dinoflagellates, cocclithoph
ores, silicoflagellates, and extremely very
minute varieties
called nannoplanktons and picoplanktons.

22. • Photosynthesis
Photosynthesis is the process used by
primary producers to manufacture their own
food in the presence of light. These
organisms possess a green
dye, called chlorophyll, which is the molecule
that traps sunlight and converts it to chemical
energy in chemical bonds of substances
called carbohydrates. When these bonds are
broken, the energy is released and used in a
variety of ways by organisms.

23. • Carbohydrates are assembled from
small, simple, low-energy molecules such as
water and CO2, to produce large, high-energy
molecules (sugar) and oxygen.
• 6CO2 + 6H2O --> C6H12O6 + 6O2

24. • Chemosynthesis
This is another energy binding process
performed by organisms that do not use light to
harness energy for living organisms. Instead,
because these organisms live in the aphotic
zone, they capture energy from breaking down
chemical bonds of simple molecules (such as
hydrogen sulfide), and use the energy obtained
to synthesize carbohydrates from carbon dioxide
and water. Chemosynthesis is estimated to
contribute 2% to 8% of the ocean's primary
productivity.

25. Structure
The oceans can be divided into
several vertical and horizontal zones.

26. Structure
• Litoral zone- the shallow shoreline under the
influence of the rise and fall of the tides
• Neritic zone- extends from the coast to the
margin of the continental shelf
• Oceanic zone- beyond the continental shelf
• Epipelagic zone- is the surface layer of the
ocean that extends to a depth of 200m
• Mesopelagic zone- extends from 200m to
1000m

27. Structure
• Bathypelagic zone- extends from 1000 to
4000m
• Abyssal zone- the layer from 4000to 6000m
• Hadal zone- the deepest part of the ocean

28. Structure

29. Ocean Light Zone
• 1. Sunlit Zone: This is the top layer, nearest
the surface. It is also called the euphotic
zone. Here there is enough light penetrating
the water to support photosynthesis.
2. Twilight Zone: Only a small amount of light
can penetrate the water at this depth. As the
water becomes deeper, the pressure
increase, too. Plants do not grow here. Only
animals that have adapted to little light
survive.

30. • 3. Midnight Zone: Ninety percent of the
ocean is in the midnight zone. It is entirely
dark—there is no light. The water pressure is
extreme. The temperature is near freezing.

31. Ocean Light Zone

32. Human Impact
Humans have a lot of 'waste' that is
often disposed of in the ocean -
trash, sewage, oil, chemicals, heat, and
even 'noise' to name a few.

33. Human Impact
• Over fishing
• Climate change
• Oil spills
• Noise pollution
• Habitat destruction
• Introduction of alien species
• Sewage and trash