Corals and Symbiotic Relationships

Corals reefs are home to...

100,000 different species of sea creatures

What is a symbiotic relationship?

A close and often long-term living relationship between two different biological species

When do most corals feed?

At night.

Mutualistic

Both organisms benefit

CaCO3

Calcium carbonate

What are corals?

Corals are marine animals (usually tiny) that have a structure called a polyp.

Coral bleaching

Corals get stressed by changes in conditions (water, temp, light, availability of food/nutrients). They expel their zooxanthellae which causes the coral to look bleached because when the colorful zooxanthellae are gone, you can see through the clear polyps to their white calcium carbonate shell. (If the algae is gone for too long, the coral polyps die eventually)

Zooxanthellae and coral

Important mutualistic symbiotic relationship. Corals get up to 90% of their nutrients from zooxanthellae and the zooxanthellae gets protection and chemicals that they need for photosynthesis from the coral polyp.

Where are nematocysts located?

In the coral polyp's tentacles and outer tissues.

Parasitic

One organism benefits and the other is harmed or killed

Commensal

One organism is benefited and the other is not affected

Polyps

Polyps have a sac-like shape with one opening to take in nutrients and to get rid of waste products.

Coral reefs

Structures that are made of the calcium carbonate that has been deposited by coral polyps and organisms over thousands of years.

Soft corals

They do not produce the hard shell. They do produce small amounts of calcium carbonate so they can keep their shape. Soft corals always have multiples of 8 tentacles.

Reef-building corals (hard corals)

They secrete calcium carbonate which forms a hard shell that protects the polyp. Hard corals always have multiples of 6 tentacles.

How do corals capture food?

They use stinging cells called nematocysts.

Zooxanthellae

Tiny, unicellular algae that live within coral polyps' tissues. They give coral their color. As they engage in photosynthesis, they provide food for the coral polyps and essential ingredients that corals need to build their hard shells.