OCEAN ZONES
• ZONES OF THE WATER COLUMN
• FEATURES OF THE OCEAN FLOOR
• OCEAN BIOMES

Intertidal
Pelagic
Benthic
Abyssal
Four Zones of
Interest

• Intertidal : the area between high tide and low tide. Sometimes covered, sometimes exposed, a very tough habitat to live in.
Subjected to drying and submersion, temperature extremes, the pull of the waves, and sea and land predators.
Animals often burrow or have hard shells that can be sealed to prevent water loss.
Plants usually cling to hard bottoms.

High Tide
Low Tide

• Pelagic zone : Open ocean zone.
Usually sub-divided by depth or amount of sunlight. The upper pelagic receives sunlight, so there are many phytoplankton for photosynthesis.
Zooplankton, jellyfish, squid, and fishes of all sizes make up the food chain. The lower reaches receive less or no sunlight, so there are no plants and animals are often bioluminescent (make their own light).

BENTHIC PELAGIC

• Abyssal: The midnight zone of the ocean – no light penetrates. The pressure at 10,000 ft. would be like you having 5 jumbo airliners on your back. Animals are adapted to withstand the dark, the cold (near freezing), and the tremendous pressure.
That’s why they usually don’t survive the trip to the surface. Most are dark or nearly transparent in color, and are bioluminescent. They don’t move much, and usually eat what falls from above. Jaws are big to swallow large objects whole.

A very hostile environment
Increasing Cold Increasing Pressure

Fantastic
Denizens of the Deep

• Benthic : a term meaning bottom, is the ocean zone ranging from the deepest part of the ocean to the shore. Many kinds of organisms live in the benthic zone – plants, anemones, sponges, fish, skates and rays, octopus, mollusks, crabs, sea stars, corals and worms.
Most are scavengers. In the deep ocean, there are special benthic communities around hydrothermal vents whose energy comes from chemical reactions rather than from the sun.

BENTHIC PELAGIC

Intertidal Benthic Coral Reef
Hydrothermal vent

In 1977, the submersible Alvin found seafloor vents that were gushing hot mineral-rich water in the midnight depths of the ocean.
Cold sea water seeps into cracks in the
Earth’s crust and is superheated by the magma in the mantle. The hot water with dissolved minerals from the magma rises and spews out like an undersea geyser .

Cold water and chemical reactions cause mineral deposits to settle out as vent chimneys.
Fantastic communities of organisms that live by chemosynthesis thrive around these “black smokers”, using energy from chemical reactions with minerals in the water to live.

OCEAN ZONES
• ZONES OF THE WATER COLUMN
• FEATURES OF THE OCEAN FLOOR
• OCEAN BIOMES

• What do you think the ocean floor looks like?
Is it flat? Saucer-shaped? Mountainous?
• The same mountains, valleys, plains, trenches, and pits we see on land are also on the ocean floor.

• Continental shelf: surrounds the continent as a shallow extension of continental crust extending out to the continental slope.
• Continental slope: steep drop-off at the end of the continental shelf that connects the continental crust to the oceanic crust.
• Together, they make up the continental margin.

• Abyssal plains: are the flattest areas on earth.
• Ocean ridges: are long mountain ranges formed when magma seeps or erupts between pieces of the Earth’s crust (tectonic plates).
• Trenches: are the deepest part of the ocean and are formed when one tectonic plate is forced under another tectonic plate.
• Seamounts: isolated volcanic mountains which erupt under the ocean. Large ones are islands.
• Guyots: are extinct volcanoes with eroded flat tops.

The highest mountain on Earth is Mauna Kea,
Hawaii, a seamount
Ocean ridges form a mountain chain 40,000 miles long through all the oceans
The average depth of the ocean is 12,200 feet (3,720 m.)

Trenches form where tectonic plates (chunks of the Earth’s crust) are forced under another plate.
The Mariana Trench in the western Pacific is the deepest point on Earth –
36,198 ft. (11,033 m.)

In 1960, the US Navy sent a small submersible (mini-sub) to see how far down it could go. It sat on the bottom at 35,838 ft.
(10,923 m.) The sailors had
7 miles of water over their heads!

OCEAN ZONES
• ZONES OF THE WATER COLUMN
• FEATURES OF THE OCEAN FLOOR
• OCEAN BIOMES

• Can be divided by zones: intertidal, pelagic, and abyssal. Benthic organisms are the bottom dwellers in each zone.
• Each zone requires different adaptations for survival. Organisms are specialized to live in a particular zone.
• Like in land biomes, similar types of flora and fauna live in similar types of biomes across the world oceans.

Pelagic
Intertidal
Abyssal
Benthic

• “Aquatic” means water.
• Other aquatic biomes besides the ocean
(marine biome) are freshwater and estuarine.
• Freshwater is water with no salt, and includes rivers, lakes, ponds, etc.
• Estuaries are environments where salt water and fresh water meet. The salinity (amount of salt) varies with the tides and the seasons.
• Estuaries are often warm, shallow, protected places that serve as nurseries for marine organisms.

Marine
Estuary
Freshwater

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AMSTI-GLOBE
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