Coral Reefs
Abstract
In this lesson, students will participate in a PowerPoint-lead discussion of basic reef
formation, coral reef research, and community outreach programs. Students should have
basic knowledge of coral reef biology and coral reef formation prior to this lesson. After
viewing and discussing the presentation, students should be able to describe the geologic
origins of the island of Moorea, and be able to list and describe three reef types. This
lesson is also a good starting point to discuss the importance of community education and
involvement in scientific projects.
Level
High School
Time required
30 minutes, or half a class period
Teacher Background
Along with other lesson plans on the MCR LTER website, this presentation can be used
to assist educators in developing meaningful curriculum for their classrooms.
This PowerPoint was designed to be used in a high school Marine Science class. There is
an explanation of the geologic origin of the island of Moorea, as well as some of the local
fauna found on the reefs surrounding Moorea. Students should be given a brief
explanation of similar island formations, like Hawaii. Each slide offers a general
description or explanation of a specific topic, which allows for further discussion by
teachers and students.
Outreach is a crucial part of the LTER project as it allows the local school children to see
first hand what the lab has to offer and what scientists are working on. This specific
outreach program was completed over a two week period in April 2009. Teachers might
want to talk about the importance of community involvement and education.
This PowerPoint can serve as a spring board for discussion on various marine related
topics for classes of various ages and academic ability. Some ideas for lesson plans that
could be set up are as follows.
 Marine geology
 Types of coral reef
 Symbiosis
 Fauna of Moorea’s coral reefs
 Importance of outreach in an island community
What are corals?
Corals belong to the phylum cnidaria, within the animal kingdom. Corals are related to
jellies and sea anemones because they possess stinging cells, called nematocysts, which
they use for protection and to capture food. Corals can be either hard or soft, and it is the
Craig Didden
Moorea Coral Reef Long Term Ecological Research Program
hard corals that are capable of building coral reefs. Almost all corals are colonial
organisms, which means that each of the large coral structures that make up a reef are
made of hundreds to hundreds of thousands of individual animals. Each individual animal
is called a polyp.
Corals grow best in sunny, shallow, clear water, where the temperature is between 25º
and 31º C. The water must be clear and shallow for the coral to receive sunlight. Corals
do poorly in areas inundated by freshwater river runoff, or where silt can smother corals
or muddy the water and block sunlight. Most corals contain symbiotic algae cells within
their polyps. These algae, called zooxanthellae (or symbiodinium), have a mutualistic
relationship with the coral. The coral provides the algae with a protected environment and
some of the compounds needed for photosynthesis. In return, the zooxanthellae produce
oxygen and supply the coral with important metabolic compounds (like glucose, glycerol,
and amino acids). In poor environmental conditions coral polyps expel their
zooxanthellae, which results in a white, bleached appearance. This process, called coral
bleaching, leads to the death of the polyps and is a major concern to reef health
throughout the world.
Coral reefs are home to many different animals, all growing together and dependant upon
one another for survival. Coral reefs usually form around islands, using the warm
shallow waters as areas to reproduce and grow. Fringing reefs are reefs that grow along
the edges of islands. As the volcanic islands sink, the once fringing reef becomes a
barrier reefs and a new fringing reef forms. Barrier reefs enclose a lagoon and protect the
lagoon, fringing reef and island from open ocean currents and waves. Atolls are created
when volcanic islands completely sink below the ocean surface, leaving a circular barrier
reef around a lagoon. Atolls are also created when water levels rise to cover an island and
the surrounding reef grows to keep up with the surface of the water.
Craig Didden
Moorea Coral Reef Long Term Ecological Research Program