Ambassadors of the Environment

Kapalua A collaboration between

Coral reefs are like cities under the sea because they have power plants, farms, recycling, public housing, public health, advertisement, managers AND corals are the construction crew that creates the buildings.

Each resident of the reef has a job and all these residents do the work necessary to keep the reef functioning. In many ways it is like a city under the sea.

This big mound is a lobe coral. Corals are made by small animals, called coral polyps. Corals are the architects and construction crews of the reefs. The reef structure is made of coral skeletons.

Each little flower is an individual coral polyp. All of these individual coral polyps create the coral colony. It is coral colonies

that become the buildings of this city under the sea. They are coral buildings.

Notice that this coral is green. The color is due to tiny algae living inside the coral’s tissues. These algae, called

zooxanthellae, perform photosynthesis. They use sunlight to make food that helps corals build the reef structure and food

that also supports the reef food web.

There are many types of corals with a diversity of architectural styles. The different colors are due to the different varieties of algae living

inside. So the coral buildings of this city under the sea have roof-top gardens or power plants AND the waste of the animal serves as fertilizer

to help the algae grow.

Almost every surface of the reef is collecting solar energy and making food. Here brownish algae cover the hard bottom. Like the zooxanthellae living

inside the corals, these algae create food from raw materials and sunlight. Notice the scrape marks that from a grazer that feeds on this algae

Parrotfish are the lawn mowers of the coral reef. They graze on algae and keep it from overgrowing the reef.

As they graze they scrape off part of the reef and erode the limestone.

Parrotfish grind up the algae along with bits of reef and then poop sand. This parrotfish can make 200 pounds of sand each year

When your family takes a walk on a beautiful tropical beach, you may want to remind them that some of the sand

they are walking on is parrotfish poop.

These sea urchins are also part of the landscape management team. They graze on algae and help keep the reef from being overgrown with

weeds. This is important because nutrients from agriculture, fertilizer and sewage and promote excessive growth of algae and can smother a reef.

Green turtles and surgeonfish also help control the growth of algae. All of these herbivores use the energy in their food to keep themselves alive. They are important links in the reef’s food web transferring energy in algae

through herbivores and up to carnivores.

Hawkfish that sit and wait for food to come by and triggerfish that swim around looking for food are predators.

They are the next link in the food web.

Eels come out at night to explore the reef in search of sleeping fish and other prey. They may look scary, with their mouths open, but they have to keep their mouths open to breathe – to pass water across their gills.

Large predators embody the energy from the sun that passed from algae to herbivores

and through a series of predators, ending up with fish like this grouper and sharks.

Predators, such as sharks, prey on smaller fish. They keep the populations under control

and maintain ecological balance on coral reefs.

Sea cucumbers are the sanitation engineers of the reef. They are the clean-up crew as they crawl over the reef and feed.

They ingest sand, digest waste organic matter and release the sand cleaner than it was before.

They are good recyclers.

This slipper lobster, other crustaceans, worms and bacteria also digest waste organic material,

keeping the reef clean and healthy

This slipper lobster, other crustaceans, worms and bacteria also digest waste organic material,

keeping the reef clean and healthy

Here we see that energy from the sun powers the food web from algae to large predators. The material of the reef gets recycled

ending up as nutrients that help algae grow.

The reef has an incredible diversity of species. Each has its own way of living and each contributes to the health of the reef

Nudibranchs are snails without shells, using bright coloration as “advertisement!”

The bright colors say to hungry fish, “Stay away! I’m poisonous!”

Sea urchins demonstrate reef diversity. Notice the different types of spines of these urchins. Pencil urchins, upper right, have thick spines

that are too much trouble for trigger fish to bite through.

These urchins are like “termites” that excavate holes and chambers in the reef,

creating great places for other creatures to hide.

These urchins decorate themselves with debris for camouflage. Notice the 2nd one on the right.

Corals are not the only animal on the reef that is home to others. Look closely at this urchin and see if you can find someone

living among the spines.

This is a commensal (resident) shrimp perfectly adapted to live and hide among the spines of this urchin.

Another example of diversity is the family of butterflyfish. Many have a spot called a false eye to distract predators from their

real eyes. As you can see, some species also have a dark line over their real eye to further confuse a predator.

Surgeonfish have a sharp “scalpel” at the base of their tail. They call attention to this defensive weapon

with a warning, bright white coloration.

This Achilles surgeonfish calls attention to its scalpel. Your eye is drawn to the razor sharp spine

that can easily cut a finger to the bone.

The opposite of warning coloration is camouflage. Can you see the eye of this frogfish?

Now do you see the eye. Notice the mouth is facing up. These fish have a little spine, just above the eye, that looks like a worm.

When it is wiggled small fish come to investigate and are gobbled up

Some fish have diversity in their coloration. These goatfish rest on the bottom and have a greenish color with a yellow

stripe or a blotchy coloration seen in the fish at the upper right.

These two goatfish are at the doctor’s office. To attract the attention to the yellow and blue cleaner wrasses that pick off parasites, the goatfish

stand on their heads and even extend barbels (chin whiskers) on the left.

This goatfish just changed to pink, presumably to make it even more clear that it needs service

and to make it easier for the cleaners to find parasites.

At night these goatfish have another coloration – blotchy red pajamas.

This spiky crown-of-thorns sea star eats corals.

Crown-of-thorns evert their stomachs to digest coral outside the sea star’s body.

BUT the coral has a pal that fights to protect the coral from crown-of-thorns. When the predator comes the resident crab

emerges and pinches off the sea star’s tube feet.

After the crab has pinched off a few of the sea star’s tube feet the predator moves on to another coral that may not have a protective crab.

Humans are part of this story because when we allow nutrients from sewage, fertilizer and land run off to enrich coastal waters, we enable

more baby crown-of-thorns babies to survive. This can result in a population explosion that results in

entire reefs being killed by these sea stars.

So these beautiful sea stars may or may not be a problem for reefs. It depends on how humans understand and manage

their connections to reefs.

Excessive nutrients can also enable algae to overgrow corals. This problem can be even worse when people harvest too many

herbivores like parrotfish, surgeonfish and even sea urchins that some people eat.

We are all connected to reefs through the energy we use. Carbon dioxide from burning petroleum is causing global warming and ocean acidification. When the water becomes too warm corals lose the algae that provide them with food, turn white and may die.

This is called coral bleaching. Acidification also makes it more difficult to make their skeletons.

The diversity of species keeps this city under the sea healthy. Corals have solar collectors (algae) and create the buildings of this city.

Waste is recycled. Grazers and predators keep things in order. Partnerships are important to many species. People are part of this ecosystem .

We can do it harm or protect it – its up to us.