Coral Reefs

Coral Reefs

Warm, shallow reefs found in tropical oceans.

Where are coral reefs found?

Along continents, around islands, and in open-ocean atolls.

Optimal coral reef temperature

About 73–84°F.

Atoll

A ring-shaped reef or chain of islands formed by coral.

Fringing Reef

A reef along a coast, usually with a shallow lagoon.

Barrier Reef

A reef parallel to a coast with a deep lagoon between the reef and coast.

Great Barrier Reef

A famous example of a barrier reef located in Australia.

Three types of coral reefs

Fringing reefs, barrier reefs, and atolls.

Zooxanthellae

Algae that live symbiotically within coral tissue.

Coral and zooxanthellae relationship

A symbiotic relationship where both the coral and algae benefit.

What do zooxanthellae provide corals?

Nutrients produced through photosynthesis.

What do coral reefs provide zooxanthellae?

Shelter and access to sunlight for photosynthesis.

Coral Bleaching

The loss of zooxanthellae from coral tissue, causing the coral to turn white.

Cause of coral bleaching

High water temperatures can cause zooxanthellae to leave coral tissue.

Why does coral bleaching harm coral?

The coral loses its main source of nutrients and energy and may eventually starve.

Why does coral turn white during bleaching?

It loses the colorful zooxanthellae living in its tissues.

Can coral bleaching be reversed?

It can sometimes be reversed in the short term if conditions improve.

Zooxanthellae and coral energy

Zooxanthellae provide most of a coral's energy through photosynthesis.

1997–98 coral bleaching

High ocean temperatures killed about 10% of ocean reefs.

Great Barrier Reef bleaching

The Great Barrier Reef has experienced five mass bleaching events since 2016.

Great Barrier Reef coral impact

About 91% of corals were impacted by bleaching.

Cyanide fishing

A fishing method common in Southeast Asia that uses cyanide to stun and capture fish.

Cyanide fishing impact

Cyanide can kill nearby organisms, especially corals.

Dynamite fishing

A fishing method that uses explosives to kill or stun fish.

Dynamite fishing impact

It destroys coral reefs and other marine habitats.

Cold Deep Reefs

Deep-water reefs that can live in extremely cold, deep water.

How deep can cold deep reefs live?

They can live in water up to about 20,000 feet deep.

How cold can deep reefs live?

Some can survive in water as cold as about 30°F.

Do cold deep reefs require sunlight?

No, they do not require sunlight.

How do cold deep reefs obtain nutrients?

They trap tiny organisms from the water using structures such as tentacles.

Oldest marine organisms

Some cold deep reef organisms are among the oldest marine organisms.

Age of some deep reef organisms

Some are more than 4,000 years old.

Deep reef organism size

Some deep reef organisms grow much larger as they get older.

Bottom trawling

A fishing method where large weighted nets are dragged along the seafloor.

Bottom trawling impact

It mostly affects older marine organisms and can disturb deep-sea habitats.