Ambassadors of the
St.Thomas in the U.S.Virgin Islands, with its coral reefs and mangroves, is
a perfect place to connect people to the wonders of nature. Jean-Michel
Cousteau’s Ambassador’s of the Environment Program is dedicated to
immersing people in these tropical ecosystems and helping them
appreciate the value of nature.
In the Ambassadors program,
we use the City Under The Sea
metaphor to understand the
ecological roles of reef
creatures. As in human cities,
everyone has a job and
together all of the work done
by residents keeps the
community healthy and
running smoothly. Coral reefs
have power plants, farmers,
recycling and waste
management, and even public
As the construction crews and architects of the reef, coral provide homes
for many different creatures on the reef, like this Christmas tree worm
and this blenny.
Sponges help clean the reef, filtering water through their porous bodies
to extract a tasty meal of organic matter like plankton and bacteria.This
makes the water clean, clear, and healthy for the other reef inhabitants.
Sponges - The air/water conditioners of the coral reef
There are also“farmers” on the reef. Some damselfish maintain patches
of algae to ensure a steady food supply,“weeding out” unwanted
organisms and defending their gardens from intruders.This feisty
damselfish is facing off with his own reflection!
Damselfish - the farmers
Sea cucumbers are the“waste managers” of the coral reef.They roam the
seafloor, ingesting a mixture of sand and dead organic matter (detritus)
and excreting clean sand.This keeps the reef clean and healthy and
ensures that not even the“trash” of the reef is wasted.
Sea cucumbers - the waste managers
Cleaner gobies -
DOCTORS of the city under the sea
Cleaner shrimp - “say ahhhhhh”-
DOCTOR of the city under the sea
There are also“demolition crews” on the reef.When parrotfish and sea
urchins feed upon algae, they scrape away some of the dead coral skeleton
underneath with their rasping teeth and parrot-like beaks.This action
erodes the reef and turns old coral skeletons into sand!
Sea urchins and parrotfish -
Weed removal on the coral city
Mangroves serve as babysitters for countless inhabitants of the coral reef.
Mangroves are salt tolerant trees that grow along the shoreline and have
special roots that stick up out of the soil, creating a labyrinth of little spaces
where only young, small fish can fit, protected from predators.
Nurseries of the coral city
Solar power plants
Corals, in addition to being architects and construction crews, are also one of the biggest
solar power plants in the coral city. Not only are they an animal that catches plankton
(usually by night), but they also harbor algae inside their body tissues so they can make
food from sunlight during the day.
There are many types of algae
that grow on their own and
are readily visible on the coral
reef.They make their own food
from sunlight and then
become food for many reef
creatures, such as parrotfish
and some butterflyfish.
Therefore, like our electric
power plants, algae provide
energy for the entire coral city.
We have now learned that coral reefs and cities have many similarities.
However, unlike in human cities, the inhabitants of coral reefs and
rainforests do not pollute, deplete their natural resources, or destroy other
ecosystems.Therefore, coral reefs offer lessons that can help us make our
own communities more sustainable.
What Can We Learn From Coral Cities?
By understanding how nature
works, we can imitate it and
make our own way of life more
sustainable on Earth. In the
Ambassadors of the
Environment program, we
learned four simple lessons
about how nature works and
used them to brainstorm ways
to live sustainably.We call
them the Four Principals.
The Four Principles
The Four Principles
1. Everything Runs On Energy.
2.There Is No Waste In Nature.
3. Biodiversity Is Good.
4. Everything Is Connected.
Just like our bodies, cars, light
bulbs, computers, televisions,
and kitchen appliances –every
organism in nature needs
energy. Some creatures, like
most corals (with their algae
partners) and plants, get their
energy from the sun in a
process called photosynthesis,
and therefore we call them
1. Everything Runs
Corals are actually animals, not plants. Each little circle shown here is an
individual coral animal, or polyp.The entire colony of polyps are clones of
a single original individual, and together they are called a coral head.
However, we know that plants perform photosynthesis, not animals. So
how do corals manage to do photosynthesis?
Coral polyps contain little brown or green plants called algae inside their
bodies.These algae give a portion of the sugars they create through
photosynthesis to their coral host in exchange for their safe home inside the
coral’s body.The coral then gives the digested remains of the sugar back to
the algae, which the algae then use to manufacture more sugar! This tight,
efficient partnership is how corals get much of their energy and enables
them to survive in the relatively nutrient-poor waters of the tropics.
They have stinging
nematocysts that catch
Coral are truly
amazing- they lead the
life of a plant by day,
and an animal by
But what happens when the sun goes
down and the algae inside the coral can
no longer photosynthesize? The coral
polyps, having been folded safely away
during the day, emerge to catch prey
like little upside-down jelly fish.
(Indeed, coral is very closely related to
This elk horn coral looks like it
is reaching upward to get
And these pillar corals are
truly the skyscrapers of this
city under the sea.
Those elk horn and pillar corals
were reaching up toward the sun
because they wanted sunlight to
help their gardens grow. And this
brain coral uses high surface area
to allow more algae to make
more food for the coral. Notice
these corals are colored green
and brown because they have
algae living inside them.This
adaptive partnership enables
corals to get food from their plant
partners during the day.
When primary producers like plants or coral are eaten, energy is
transferred up the food chain. Energy flows from primary producers to
herbivores, and then to predators.This means that all organisms in these
ecosystems are powered by energy that originally came from the sun!
Sea grass beds are an important part of the reef’s solar power system.
The solar energy they convert into food or chemical energy in their tissues
becomes food for many reef herbivores. Does anyone know what this big
herbivore is? Lets take a closer look.
You guessed it!
This is a queen conch that feeds on turtle grass and manatee grass.
Notice its two eyes peeping out at the lower left side of the shell.
How do humans presently get most of their power? From oil and coal-
power plants. In these power plants, oil or coal is burned to heat water
and create steam, which turns turbines that generate electricity.
However, burning oil and coal releases harmful greenhouse gasses into
our atmosphere, contributing to global climate change.This serious
problem could be solved by switching to renewable energy sources such
as wind, solar, and geothermal energy.
The second Principle says there is no waste in
nature. For example, on coral reefs, creatures
such as sea cucumbers and lobsters
specialize on eating detritus, the organic
“leftovers” or“dead stuff” on the seafloor.
Along with worms and microbes, sea
cucumbers and lobsters ensure that virtually
all useful material is used on the reef.
2.There Is No Waste In Nature
Hermit crabs ensure that vacated snail shells are not wasted.
They turn them into their mobile homes!
This christmas tree worm bores a hole into the coral below it to create a safe
place to live. Given that there’s no waste in nature, what do you think is going
to happen to this hole when the worm dies?
It will become a home for another animal, like this blenny!
There are a variety of worms on the reef. Feather duster worms, on the left, and
Christmas tree worms, on the right, use their delicate gills for both feeding and
breathing. Because they eat drifting organic matter, in addition to plankton,
they can also be considered as part of the reef’s clean up crew.
Today, humans tend to waste a lot of resources. One thing we can do to
change this situation is compost. Composting is where worms, bugs and
microbes convert organic waste into soil, just as we see in nature. By
composting food leftovers, we prevent garbage from going to ever-
growing landfills. Instead, waste is converted into useful, fertile soil that
can be reused in a garden.
3. Biodiversity Is Good
Biodiversity refers to the number
of different species that live in a
certain ecosystem. It is kind of like
nature’s insurance policy, because
when there are a lot of different
organisms in an ecosystem, all of
the important work needed to
keep the community healthy gets
done. If one species ails or
disappears, many others are
around to replace it.Therefore,
biodiversity is what keeps
complex ecosystems like coral
reefs running smoothly. Also,
biodiversity is what makes our
world interesting and beautiful!
Here is a taste of the amazing biodiversity that can be found on the coral
reefs in St.Thomas!
Just look at the
diversity among corals
alone. How many
different types of coral
can you count here?
means that there is a
great variety of form
and function in the
coral reef. For example,
these porous sponges
filter water through
comes in through
small pores in their
sides, is filtered for
food, and leaves
through the big holes.
Here are two different kinds of algae.The green algae is called a sailor’s
eyeball, and it is growing on top of pink coralline algae, a type of red
algae that covers most reef surfaces and acts like mortar, cementing
pieces of the reef together and helping prevent erosion.
A diverse family of butterflyfish lives on the coral reefs in St.Thomas.
These fish often have a spot called a false eye on their bodies, an
adaptation that distracts predators from their real eyes. As you can
see, some species also have a dark line over their real eyes to further
confuse a predator.
The long, thin shape of these
trumpetfish help them blend in
with various gorgonians and
soft coral.They often wait here,
swaying in time with the gentle
motion of their surroundings,
ready to suddenly dart out and
catch passing prey.
Parrotfish use their sharp beaks to scrape algae from rocks and coral
skeletons, keeping the growth of algae in check. As they graze, they often
gouge into dead coral and take in some of the calcium carbonate, later
excreting this material as sand. One parrotfish can produce 300 lbs of
sand in one year!
So next time you walk down a tropical, sandy beach, remember where some
of that sand likely came from!
spiny skin, an
since you can see many
projections of its
skeleton on the surface
of this sea star. On the
underside of the sea
star you can find tube
feet, thousands of
small suckers the sea
star uses to stick to the
ground or slowly move
Sea stars are members of the
echinoderm phylum, and they
are related to sea urchins and
Diversity is good even within
a single species. French
angelfish change their
coloration as the grow. Look at
the differences between the
juvenile (top left)
intermediate stage (top right)
and the adult (bottom).
Mangroves are another example of the biodiversity found on St.
Thomas. As one of the few salt-tolerant plants, they live on margin
between land and sea, bordering some of the island.They create
essential habitat where many fish, birds, and other critters live.
Sea grasses are also very important to St Thomas.They are a habitat for
many fish, like these surgeonfish.They are also an important source of
food for some species of turtles and even bigger animals like manatees.
The fourth Ambassadors of the Environment principle is that EVERYTHING
IS CONNECTED–person to person, creature to creature, land to sea, and
present to future.We encountered many examples of connections
between organisms both in the ocean and on land. For example, this tiny
yellow and black goby has a partnership with reef fish in which it eats
their dead scales and parasites: it gets a meal in exchange for a cleaning!
4. Everything Is Connected
There are connections between various fish that live on the reef.This jack is
using a queen triggerfish as a moving shield to hide behind while it hunts.
Notice the jack is on the side away from the reef so that it is concealed. Just
after this picture was taken the jack darted to the reef and caught a small
fish then returned to its position next to the triggerfish.
Here is an example of a negative connection between reef creatures.
This isopod has attached itself to the head of a soldierfish and is leaching
energy and nutrients from the fish’s blood.This is a parasitic relationship
because the isopod benefits while the soldierfish is harmed.
This juvenile Spanish hogfish, top, hangs around on one place of the reef
called a cleaning station. Larger fish, like this French grunt, come to these
places to get their medical problems tended, like removing parasites.
There are often connections between organisms that we do not notice
at first glance! This orange blob is a sponge but there is more to this
story than what you see. What do you think we would find if we turned
this sponge over?
In the sponge is a crab. In fact, this crab has specially adapted hind legs
that hold the sponge in place.Why do you think the crab does this?
By carrying around the sponge, the crab is not only hidden but it is also
protected by the distasteful chemicals in the sponge.
Frigate birds bridge the gap between land and sea.They spend much of
their lives out to sea, in the open ocean or pelagic region, coming to
shore to breed or rest.
Humans enter the
underwater world as
guests.We respect the life
around us by not
touching the reef and
keeping an appropriate
distance from its
sometimes we have
effects on these
organisms that we are
not aware of.
Humans are very closely connected to the ocean.When we pollute our
oceans, it contributes to coral bleaching, one of the serious threats to coral
reefs today.When corals become stressed due to something like pollution,
they expel their symbiotic algae, becoming white and having no way to
photosynthesize. Unless the coral can find new algal symbionts (which is
not very likely), they end up starving to death.
Notice the color of this healthy coral head compared to that of the
bleached coral.This is a very conspicuous example of how humans have a
negative impact on the health of the reef!
Human pollution can also upset the balance between reef creatures. Coral
and algae usually compete for space on the reef and are evenly matched,
but when extra nutrients from human runoff or pollution are introduced
to the system, the algae get an advantage.This is another example of the
delicate connections between organisms on the reef and how human
actions can directly affect the reef ecosystem.
Here is another obvious example of how humans are connected to the
natural world.What do you think this litter could do to the mangrove and
coral reef ecosystems?
With understanding of how connected we are to reefs we can
keep our reefs healthy and full of fascinating residents for us to
enjoy and learn from.