chapter 14 – ocean zones. exploring the ocean because of the darkness, cold, and extreme pressure,...

Chapter 14 – Ocean ZonesChapter 14 – Ocean Zones

Exploring the OceanExploring the Ocean


• Because of the darkness, cold, and extreme pressure, scientists have had to develop new technology to enable them to study the deep ocean floor.

Exploring the OceanExploring the Ocean• A major advance in ocean floor

mapping was the invention of SONAR.

• It is a system that uses sound waves to calculate the distance to an object.

• SONAR stands for:

SOund NAvigation Ranging


• The sonar system on

a ship sends out

pulses of sound that

bounce off the ocean floor.

• The equipment then measures how quickly the sound waves return to the ship.


• Sound waves return quickly if the ocean floor is close.

• Sound waves take longer to return if the ocean floor is farther away.

Features of the Ocean FloorFeatures of the Ocean Floor

• The continental shelf is a gently sloping, shallow area of the ocean floor that extends outward from the edge of a continent.

• Its width ranges from a few kilometers to 1,300 km from shore.


• The continental slope marks the true edge of a continent.

• It is where the rock that makes up the continent stops and the rock of the ocean floor begins.


• A seamount is a mountain whose peak does not break the surface.


• The abyssal plain is a smooth, flat region.

• It is covered with thick layers of sediment, formed by the sunken remains of dead organisms from the surface.


• The mid-ocean ridge is a continuous range of mountains that winds around Earth.

• It is almost 80,000 kilometers long.


• On the other side of the mid-ocean ridge is a deep ocean trench.

Life at the Ocean’s EdgeLife at the Ocean’s Edge

Living ConditionsLiving Conditions• Some physical factors determine

where marine organisms can live include:

1. Salinity2. Water temperature3. Light4. Dissolved gases5. Nutrients6. Wave action

Living ConditionsLiving Conditions

• Scientists classify marine organisms according to where they live and how they move.


• Plankton are tiny algae and animals that float in the water and are carried by waves and currents.


• Nekton are free-swimming animals that can move throughout the water column.

• Examples:

– Octopus, squid, most fish, whales, dolphins, etc.


• Benthos are organisms that inhabit the ocean floor.

• Example:

–Crabs, starfish, lobsters, sponges, anemones.

The Rocky ShoreThe Rocky Shore

• The intertidal zone stretches from the highest high-tide line on land out to the point on the continental shelf exposed by the lowest low-tide.


• Organisms that live in the rocky intertidal zone must be able to tolerate:1. Wave Action

2. Changes in salinity

3. Temperature

4. Being exposed to both air and under water


• When the tide goes out some of the water remains in depressions among the rocks called tide pools.

• As the water in the tide pool is warmed by the sun it begins to evaporate causing the remaining water to become saltier.

Where River Meets OceanWhere River Meets Ocean

• Brackish water is salty sea water that has been mixed with freshwater.

• Estuaries are coastal inlets or bays where freshwater from rivers mixes with salty ocean water.


• Along the United States coasts, most coastal wetlands are either salt marshes or mangrove forests.

Where River Meets OceanWhere River Meets Ocean• A salt marsh oozes with smelly mud that

is rich in nutrients.

• Mosquitoes swarm over the water, which moves slowly through the tall grasses.

• Cordgrass dominates the marsh.

• Tidal channels run through the Cordgrass (waves break up)


• Mangrove forests grow well in brackish water.

• They provide a rich and sheltered area for organisms to grow.

• Fringe the coast of southern Florida.

The Neritic The Neritic & &

Open-OceanOpen-OceanZonesZones

What is the Neritic Zone?What is the Neritic Zone?

• The neritic zone is the part of the ocean that extends from the low tide line out to the edge of the continental shelf.

What is the Open-Ocean What is the Open-Ocean Zone?Zone?

• The open-ocean zone is beyond the continental shelf.

The Neritic ZoneThe Neritic Zone

• The neritic zone is home to the largest variety of organisms found in the ocean.

• Most of the world’s major fishing grounds are located in the neritic zone.


• Why is the neritic zone home to so many living things?

– Shallow water receives lots of sunlight.

– Steady supply of nutrients from the land.


• The light and nutrients allow giant algae (kelp) to grow.

• The algae serve as a food source and shelter for other organisms.


• The neritic zone has two habitats:

1. Kelp forests

2. Coral reefs

Neritic Zone: Kelp ForestNeritic Zone: Kelp Forest

• Kelp is a large, heavy algae.


• Kelp requires a solid, rocky bottom to anchor their stalks.

• A bundle of rootlike strands called a holdfast attaches the algae to the rocks.


• The kelp use sunlight and dissolved gases in the neritic zone to produce their own food.

• Large collections of growing kelp is called a kelp forest.

• Kelp forests grow along the Pacific Coast from Alaska to Mexico.

Neritic Zone: Coral ReefsNeritic Zone: Coral Reefs

• Coral reefs are made of lots of tiny coral animals, not much larger than the size of a pencil eraser.


• Coral animals produce a hard structure that surrounds their soft bodies.

• After the coral animal dies, the empty structure remains.

• New coral animals attach and grow on top of it.


• Most of the coral reefs that exist today were begun about 5,000 to 10,000 years ago.

• Coral animals feed on algae that live with the reef.

• Coral reefs only grow in tropical, shallow waters.

Neritic Zone: Coral ReefNeritic Zone: Coral Reef

• In areas where the seafloor is sinking, a reef may develop over time into an atoll.

• An atoll is a ring-shaped reef surrounding a shallow lagoon.


• Coral reefs protect the coastline from violent storms and erosion.


• Coral reefs can be damaged:

– Touching the coral

– Breaking pieces off

– Changes in water temperature

– Changes in clarity

• Can be a major problem as reefs only grow a few centimeters a year.

The Open-Ocean ZoneThe Open-Ocean Zone

• Light from the sun only penetrates to a depth of less than 200 meters.

• Differs from the neritic zone:– small portion receives sunlight– Fewer dissolved nutrients

• Supports fewer organisms

The Open-Ocean ZoneThe Open-Ocean Zone

• The open-ocean zone is divided into parts:

1. The surface zone

2. The deep zone

The Open-Ocean Zone: The Open-Ocean Zone: The Surface ZoneThe Surface Zone

• The surface zone extends as far as sunlight reaches below the surface.

• The surface zone is the only part of the open-ocean zone that receives enough sunlight to support the growth of algae.

The Open-Ocean Zone: The Open-Ocean Zone: The Deep ZoneThe Deep Zone

• Few organisms live in the deep ocean due the very cold temperatures and great amounts of pressure.


• Many deep sea organisms produce their own light which is called bioluminescence.

• This allows them to find food in the dark.


• A hydrothermal vent is an area where ocean water sinks through cracks in the ocean floor, is heated by the underlying magma, and rises again through the crack.


• Many of the deep sea creatures live around hydrothermal vents.

• The chemical nutrients in the heated water support the unique group of organisms that are found in around a hydrothermal vent.

chapter 14 – ocean zones. exploring the ocean because of the darkness, cold, and extreme pressure,...

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