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Savannah Bussey
Ms. Shubach
8th Grade Research
9 May 2014
How animals survive in the Great Barrier Reef
Have you ever wondered what goes on in the down under? The Great Barrier Reef is
located in the Pacific Ocean along the Northeastern coast of Australia. It consists of more than
2,900 corals reefs, 600 continental islands, 300 coral cays, and thousands of species making one
of the most complex and diverse ecosystems. There are 1500 species of fish, 17 species of snake,
30 species of whales and dolphins, 22 species of seabirds, and 32 species of shore birds that
bread on the reef (Alevison). All of these organisms are necessary to the unique ecosystem that is
the Great Barrier Reef.
Along many coral reefs everything reproduces in its own way. Corals can reproduce
asexually or sexually. Corals reproduce sexually by either internal or external fertilization. The
reproductive cells are born on membranes that radiate inward from the layer of tissue that lines
the stomach cavity. Some corals have both female and male reproductive cells. Others are either
male or female. In asexual reproduction, clonal polyps bud off from parent polyps to expand or
begin new colonies. Spawning occurs as a mass synchronized event, when all the coral species in
an area release their eggs and sperm at about the same time. Fish become sexually mature at
various ages, depending on species. In general, small species begin reproducing at an earlier age
than large species. Some bony fish are sexually mature at birth. Males of the dwarf perch can
spawn immediately after birth. In most species of bony fishes, sperm and eggs develop in
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separate male and female individuals. Males and females may look similar, or they may look
very different. Male and female differences may include size, coloration, external reproductive
organs, head characteristics, and body shape. Jellyfish can be either male or female so they
reproduce sexually. (How Do Corals Reproduce)
For corals to survive they need sunlight, clear water, warm temperature, clean water, and salt
water. Water is needed for all the animals to live and breathe. Salinity belongs in the water for
animals to live. Sunlight helps algae and plants preform photosynthesis. Nutrients keep the water
clear and sand is needed because it gives crustaceans and other abiotic factors that can’t swim a
place to live (Trophic Interactions). Corals compete for living space on the reef. Some soft corals
create toxins to eliminate competitors (Adaptations for an Aquatic environment). One adaptation
of corals is attachment. Most corals polyps attach themselves to a hard substrate and remain there
for life. Another adaptation is to produce toxins. Certain toxic compounds in soft corals may
make the corals unappetizing and deter predators. Some corals eat zooplankton or small fish,
others consume organic debris. Some reef building corals can actually digest the tissue of an
invading coral. The stomach cavities of colonial corals are interconnected. Food obtained by one
polyp can be passed to other polyps in the colony. Anemones are common coral reef animals.
They have formidable defense mechanisms. Coral reef communities are extremely efficient at
acquiring, retaining, and recycling nutrients. (Diet and Eating Habits)
Most of the reef dwelling fish have certain feeding structures that help them adapt to their
habitats. Most of them have specialized jaws, mouths, and teeth suited for certain kinds of food.
Butterfly fish have forcep-like mouths armed with fine teeth to eat coral polyps. The typical body
shape of reef dwelling fish differs, their body makes them able to turn rapidly, stop quickly, and
swiftly circle around coral heads. The function of the pancake-like body shape is further
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enhanced by specialized positioning of the pectoral and pelvic fins. These are situated and
located on the body in a way that helps them make sharp turns and sudden stops. Adaptive
coloration is used to keep predators away and facilitate mating success. Coral reef fish are
perhaps best known for their bold, striking color patterns, which differ greatly from the typical
monotonic "silvery" sheen we usually associate with fish. These color patterns serve many
functional roles in the lives of these animals, including concealment, mate recognition, and
warning. Coral polyps are nocturnal feeders. At night they extend their tentacles to capture food
with the aid of nematocyst. Animals use coral reefs as a stopping point, or they live in it. Corals
use their tentacles for defense and to capture prey. Fish, crustaceans, seaweed, reptiles, bacteria,
and fungi all have habitats in coral reefs. (Alevizon)
The animals in this ecosystem are species that rely on reefs for food and places to live.
As animals eat the plants and other animals energy is passed through the food chain. Many of the
animals work as a team. This is called symbiosis. An example is a sea anemone’s tentacles
provide protection and safety for fish, while the fish protects the anemone from predators. There
are many abiotic factors including water, salinity of the water, sunlight, sand nutrients,
temperature, depth, and wave motions. Types of feeders are herbivores, planktivors, benthic
carnivores, and piscivores. Herbivores feed mainly or entirely on plant material. For example
Parrotfish, Surgeonfish, Rabbit fish, and Damselfish (Alevizon). Planktivores feed on small
animal plankton. For example open water plankton feeders, Benthic Planktivores, and Nocturnal
Planktivores (Alevizon). Benthic carnivores prey on a variety of animals living on or near the
sea floor. For example triggerfish, trunkfish, and Grunts. (Alevizon). Piscovores prey entirely on
other fish. For example pursuing predators, stalking predators, and ambush predators. The largest
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Carnivores that dwell on Coral reefs are the piscivores, they feed heavily upon herbivorous and
planktivorous fish. (Coral Reef Connections)
Three major groups of photosynthetic organisms are plants, algae, and bacteria. They all
contribute to net primary production within most coral reef ecosystems. Secondary consumers
include animals that prey upon reef dwelling herbivores. The group of secondary consumers
contains a huge diversity of animal species. Primary consumers are the herbivores that include
invertebrates like mollusks and fish. Primary producers include Blue green algae, Seaweed, and
coral. Primary consumers include Sea Urchins, Angelfish, Shrimp, Butterfly fish, Parrotfish, and
Sea Turtles. Quaternary consumers include Black Tipped Shark and Bellied Sea Eagle. The tiger
shark is an example of a keystone species in the Great Barrier Reef. Without it the reef food web
would be affected. The overall ecosystem would suffer greatly without the shark in its food
chain; there would be a server lack of balance due to overpopulation of many sharks prey. That
would result in the depletion of many species lower down on the food chain. (Coral Reef Food
Web)
Sharks keep the ecosystem balanced and allow populations of other creatures to maintain
healthy levels. Sharks regulate the quantity and health of other marine life, helping to keep fish
stocks in the ocean healthy. They tend to feed on weak, old and unhealthy fish, which stops the
spread of disease among fish populations. This eliminates a lot of the competition, meaning a
stronger gene pool and a more diverse population of sea creatures will survive. Although for
some time it has been thought that removing sharks from the oceans would result in a huge
increase in fish population – some scientists now think the opposite would happen; and the
existing populations would be wiped out by disease (Why are sharks important?). Being at the
top of the food chain, their role is vital to ensure that all parts of the food chain lower down are
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controlled. Without sharks controlling the food chain balance, the oceans could become overrun
with algae, drastically oxygen quantities in our atmosphere. The effects of this could be
devastating for all life on Earth. (Coral Reef Food Web)
Coral reefs are a special resource in the ocean because of their beauty and biodiversity.
They provide humans with recreation, they are a valuable source of organisms for potential
medicines, they create sand for beaches, and serve as a buffer for shorelines. Coral reefs are built
by millions of coral polyps, small colonial animals resembling overturned jellyfish that use
excess carbon dioxide in the water from the atmosphere. Corals are relatives of jellyfish and
anemones. Corals can exist as individual polyps, or in colonies and communities that contain
hundreds of thousands of polyps. Corals can be divided into two groups: soft coral and hard
coral. Hard corals, also known as stony coral, produce a rigid skeleton made of a crystal form
called aragonite. Soft corals, including sea fans, do not produce a rigid calcium carbonate
skeleton and do not form reefs, though they may be present in a reef ecosystem. Unlike hard
corals, most soft corals thrive in nutrient-rich waters with less light intensity. There are two
general types of corals—hard corals and soft corals. Hard corals take calcium and carbonate out
of seawater and turn it into an external skeleton that forms beneath their tissues. Corals are
mainly colonies, budding new animals as the thin layer of tissue on top of the external skeleton
expands in area. The process by which it is created is similar to that used by clams, oysters and
snails to create their hard shells. Only the outer layer of the reef is alive, as coral colonies grow
and expand and new corals build their skeletons on those of dead corals from earlier generations.
Millions of corals have built colonies in this way over thousands of years to form the structure of
coral reefs we see in the oceans. Soft corals, which look more like plants, are also animals.
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Almost all utilize zooxanthellea as a major energy source. However, most will eat any free
floating food, such as brine shrimp. (Coral Reef connections)
The warmer air and ocean surface temperatures brought by climate change impact corals
and change coral reef communities by coral bleaching events and changing ocean chemistry.
These impacts affect corals and the many organisms that use coral reefs as habitats. Warmer
water temperatures brought by climate change stress corals because they are very sensitive to
changes in temperature. If water temperatures stay higher than usual for many weeks, the
zooxanthellae they depend on for some of their food leave their tissue. Without them corals turn
white, because zooxanthellea give color to corals. White unhealthy corals are called bleached.
Bleached corals are weak and less able to fight off disease. As climate change continues,
bleaching will become more common and the overall health of coral reefs will decline. (Ocean
Science)
Tropical coral reefs, biotic reefs formed in tropical waters like the Great Barrier Reef are
formed by the deposit of sand and other materials in shallow water. The best growing habitat for
coral reefs is a clear-water photic zone less than 50 m deep where light shines down and
microscopic algae can best provide photosynthesis for the corals. Corals can be found throughout
the oceans, from deep, cold waters to shallow, tropical waters. Corals also need salt water to
survive, so they also grow poorly near river openings with fresh water runoff. Other factors
influencing coral distribution are availability of hard-bottom substrate, the availability of food
such as plankton, and the presence of species that help control macroalgae, like urchins and
herbivorous fish. The wide array of coral reef forms includes the Apron reef, the Fringing reef,
the Barrier reef, the Patch reef, the Ribbon reef, the Table reef and the Atoll reef. The Apron and
Fringe reef both reach down and out from the shore point or peninsula although the Apron reef is
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typically not as steep as the Fringe reef. Barrier reefs, like the Great Barrier Reef, are separated
from the shore by lagoons. An Atoll reef surrounds a lagoon in a circular fashion and is different
from the others because there is no island in the middle. Coral reefs are extremely sensitive to
changes in light, temperature damaging fishing practices, pollution, and excess sediment from
development and erosion. Human activity is one of the greatest threats to coral reefs, particularly
the destruction of mangrove forests that naturally absorb sediment and nutrients that can
suffocate coral reefs with silt and algae blooms. Coral reefs are very important because they
protect coasts from strong currents and waves by slowing down the water before it gets to the
shore. That is why they are called barrier reefs. They provide a barrier between the ocean and the
shore. ( KDE Santa Barbara)
Protecting the reefs also plays a big roll on how all the species of animals survive.
Humans are the biggest reason for fish extinction and coral decay. People really don’t realize the
effect that they can have on an environment. Not just the Great Barrier Reef but many other
places as well. There are many things that people can do to prevent pollution and fish from going
extinct. Conserve more water. People use way to much water in just a day by leaving the water
on while they are brushing their teeth, and leaving the shower water running. The less water
people use the less runoff and wastewater will pollute our oceans. Help reduce pollution. Fossil
fuel emissions from cars and industry raise lead to ocean warming which causes mass-bleaching
of corals and can lead to widespread destruction of reefs. Use organic fertilizers. People can live
thousands of miles from a coral reef ecosystem, but these products can still flow into the water
system, pollute the ocean, and can harm coral reefs and marine life. Throw away your trash.
Don't leave fishing lines or nets in the water or on the beach. Any kind of litter pollutes the water
and can harm the reef and the fish. Support reef friendly businesses. Ask the fishing, boating,
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hotel, aquarium, dive or snorkeling operators how they protect the reef. Plant a tree. Trees reduce
runoff into the oceans. Practice safe snorkeling and diving. Respect local guidelines when
visiting reefs. Ask at local environmentally friendly businesses how to be a reef friendly tourist.
Do not touch the reef or anchor your boat on the reef. Contact with the coral will damage the
delicate coral animals, and anchoring on the reef can kill it. Volunteer for a coral reef clean up.
You don't have to live near a coral reef. So do what many people do on their vacation, visit a
coral reef. Spend an afternoon enjoying the beauty of one of the most diverse ecosystems on the
Earth. Contact your government representatives. Demand they take action to protect coral reefs,
stop sewage pollution of our oceans. Spread the word. Remember your own excitement at
learning how important the planet's coral reefs are. Share this excitement and encourage others to
get involved. Report illegal activities on reef ecosystems. Illegal fishing, improper anchoring,
dumping of trash should be reported to proper authorities. Use less toxic household and garden
products. Replace household cleaners and detergents with chlorine and phosphate-free,
biodegradable products. Use water-based paints. Turn food waste into compost, and leave grass
clippings on your lawn to fertilize your garden. Use natural pests rather than chemical pesticides
in your garden. Drive less, walk, cycle, and skate, use public transport, combine errands, car
share. ("Coral Reefs of the Tropics") It is very important that people begin to realize what the
right thing and the wrong thing to do is. Doing the wrong thing can be very damaging to the
environment. To humans it seems normal because it doesn’t affect the way they live but it
definitely affects the species in the coral reefs. Losing one species of fish affects all the other
species that lives in the Great Barrier Reef. That is why it is important that people keep the ocean
clean and are safe while swimming, fishing, and diving. Keeping the ocean clean is one reason
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that the Great Barrier is home to so many species of fish and coral. Now people can know what
goes on in the down under of the Great Barrier Reef.