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Amethyst Johnson

Coral Reefs
What are coral reefs?
Coral reefs are built by a species of coral called hermatypic or “hard” corals, this is not
because they are hard – they are actually quite soft and fragile
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These are exoskeletons, and they protect the soft invertebrate corals
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When new polyps come along, they live in the exoskeleton
made by their ancestors and eventually these new polyps will add their own exoskeleton to
the existing calcium carbonate structure
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Coral reefs are found in tropical and subtropical oceans, usually in shallow areas at no more
than 150 feet, however some coral reefs extend deeper, until around 450 feet deep
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Biodiversity of coral reefs
For a start, there are hundreds of species of coral
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These algae provide food for the polyps using
photosynthesis, and in turn the polyps provide a home and carbon dioxide
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About 1/3 of all marine fish species live some of their lives on a coral reef
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The vast species diversity of coral reefs can be accredited to the shallow waters, which allow
algae, especially zooxanthellae, to photosynthesise and thrive
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Many species of fish in the coral reefs eat different kinds of
algae, which means the corals are protected from being smothered by it
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“Cleaner” fish and shrimp
keep other fish healthy by freeing them of parasites
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Marine worms filter organic matter in the water
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Sea squirts, salps and
molluscs sieve and eat phytoplankton
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Every organism in the coral reef plays its part to make coral reefs one of the most habitable
places on the world for marine species
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Because they are fairly shallow, they detract some of the wave or storm power, making the
effects much smaller once they reach land
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This can help to protect some of the most
endangered species on the planet
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Many of the organisms assist with carbon and nitrogen fixing – many organisms
can’t use carbon and nitrogen unless it is in specific compounds, such as carbon dioxide and
nitrates
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It also means that more fixed nutrients are
able to get into the human food chain, for example when we eat fish
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Coral reefs are also a
huge source of income for some countries, as they are used as tourist attractions – the Great
Barrier Reef generated over $1
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Science also values coral reefs very much, as they are important for providing a clear,
testable record of climatic events of the past millions of years – this may include records of
major storms and even human impacts that may be recorded by the changes in coral growth
patterns
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Examples include foods, such
as fish, and drugs – there ae new medicines being developed using reef species to treat
cancer, arthritis, bacterial infections, Alzheimer’s disease, heart disease, viruses, and more
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Coral reefs may also hold cultural value, for example coral reefs may be found in National
Parks, World Heritage Sites and other places we like to visit
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The global extent
Due to changing ocean temperatures, alien species are invading the coral reefs and can
outcompete or even kill the coral
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Because there are increasing carbon dioxide levels in the ocean, the coral skeletons are
getting weaker, offering less protection to the polyps
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Only more isolated and small island reefs are
less threatened, however some scientists predict that all coral reefs could be lost once we
reach 2050
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Due to these complex requirements, they are easily damaged or even killed
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Due to population growth and development pressures, coral reefs, salt marshes, mangrove
forests and seagrass beds have all been lost – along with the fisheries that depend on these
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Some fishers use dynamite to blow up the coral reefs, sometimes collectors poison the reefs
for the aquarium trade, and some recreationists (such as tourists – boaters and scuba divers)
can inadvertently damage the reef
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Cyanide and other toxins are often used to stun fish in the reef so they can be captured to
send to fish markets in Hong Kong and as aquarium specimens for buyers in the United
States
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Protecting and managing
The National Oceanic and Atmospheric Administration has the responsibility to conserve
coral reef ecosystems, primarily through its Coral Reef Conservation Program
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They also use satellite technology to detect algal
blooms that may harm and smother the reefs, and to monitor sea surface temperatures, which
can cause coral bleaching if elevated
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These data are
transmitted hourly to scientists to help them understand the conditions that may cause coral
bleaching
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They also
control invasive species, for example lionfish are an invasive species in the Gulf of Mexico,
Atlantic and Caribbean Sea
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They also try to manage recreational activity, by setting limits on how many people can do
certain activities at a time, as to abide by the estimated carrying capacity of the reef
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Crown-of-thorns starfish can pose a considerable threat to coral reefs when their population
blooms, so Reef Resilience monitor the abundance of this species and if it gets too high, they
can inject sodium bisulfate into the starfish – this kills the COTS and doesn’t affect other
marine life
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Overfishing or nutrient pollution can cause an outbreak in urchins, which can damage the reef
when they grow very abundant
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Sometimes, urchin
populations even need to be increased to support reef recovery, especially in areas where
populations of other herbivores have been depleted
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Reducing land based impacts is also vital to the protection of coral reefs
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