Chapter 14 – Ocean Zones

Exploring the Ocean

Exploring 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 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

Exploring the Ocean 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.

Exploring the Ocean 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 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.

Features of the Ocean Floor 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.

Features of the Ocean Floor A seamount is a mountain whose peak does not break the surface.

Features of the Ocean Floor 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.

Features of the Ocean Floor The mid-ocean ridge is a continuous range of mountains that winds around Earth. It is almost 80,000 kilometers long.

Features of the Ocean Floor On the other side of the mid-ocean ridge is a deep ocean trench.

Life at the Ocean’s Edge

Living Conditions Some physical factors determine where marine organisms can live include: Salinity Water temperature Light Dissolved gases Nutrients Wave action

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

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

Living Conditions Nekton are free-swimming animals that can move throughout the water column. Examples: Octopus, squid, most fish, whales, dolphins, etc.

Living Conditions Benthos are organisms that inhabit the ocean floor. Example: Crabs, starfish, lobsters, sponges, anemones.

The 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.

The Rocky Shore Organisms that live in the rocky intertidal zone must be able to tolerate: Wave Action Changes in salinity 3. Temperature 4. Being exposed to both air and under water

The Rocky Shore

The Rocky Shore 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 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.

Where River Meets Ocean Along the United States coasts, most coastal wetlands are either salt marshes or mangrove forests.

Where 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)

Where River Meets Ocean 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 & Open-Ocean Zones

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 Zone? The open-ocean zone is beyond the continental shelf.

The 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.

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 Neritic Zone 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 The neritic zone has two habitats: Kelp forests 2. Coral reefs

Neritic Zone: Kelp Forest Kelp is a large, heavy algae.

Neritic Zone: Kelp Forest Kelp requires a solid, rocky bottom to anchor their stalks. A bundle of rootlike strands called a holdfast attaches the algae to the rocks.

Neritic Zone: Kelp Forest 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 Reefs Coral reefs are made of lots of tiny coral animals, not much larger than the size of a pencil eraser.

Neritic Zone: Coral Reefs 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.

Neritic Zone: Coral Reefs 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 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.

Neritic Zone: Coral Reefs Coral reefs protect the coastline from violent storms and erosion.

Neritic Zone: Coral Reefs 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 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 Zone The open-ocean zone is divided into parts: The surface zone The deep zone

The Open-Ocean Zone: The 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 Deep Zone Few organisms live in the deep ocean due the very cold temperatures and great amounts of pressure.

The Open-Ocean Zone: The Deep Zone Many deep sea organisms produce their own light which is called bioluminescence. This allows them to find food in the dark.

The Open-Ocean Zone: The Deep Zone 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.

The Open-Ocean Zone: The Deep Zone 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.