The Decline of Coral Reefs

The Decline of Coral Reefs

Cameron AndersonEmily MurrayMillie AdamsPenelope Farquharson

What are Coral Reefs?

Colonies of over a thousand tiny individual corals, called Polyps

Polyps

• Marine invertebrate animals
• Hard exoskeletons made of calcium carbonate
• Sessile - permanently fixed in one place
• Grow slowly
• Different shapes and sizes - depending on their species

Essentially, coral reefs are large underwater stuctures composed of the skeletons of colonial marine invertibrates called coral.

They provide an important ecosystem for marine life, offering food and shelter among their crevices and branches for animals including fishes, sea urchins and sponges.

Where are Coral Reefs?

Corals are found in all of Earth's oceans, from tropical to freezing temperatures; however, they only build coral reefs in warm, shallow seas in the tropics - mostly in areas around the equator where the water is warmer. More than 100 countries have a coral reef within their borders, and over half of the world’s coral reefs are found within six countries: Australia, Indonesia, Philippines, Papua New Guinea, Fiji, and the Maldives.

• Among the biggest and best-known reefs is the Great Barrier Reef of Australia - around 2,300 kilometres long.

• The most biologically diverse reefs in the world can be found in a region known as the Coral Triangle in Southeast Asia

Importance of Coral Reefs

Provide a crucial source of income for millions of people.

• Coral reefs have an estimated global value of £6 trillion each year - bc their contribution to fishing and tourism industries.
• More than 500 million people worldwide depend on reefs for food, jobs and coastal defence.

Provide an important ecosystem for life underwater

• Thousands of species can be found living on one reef.
• The Great Barrier Reef contains over 400 coral species, 1,500 fish species, 4,000 mollusc species and six of the world's seven sea turtle species.

Protect coastal areas by reducing the power of waves hitting the coast

• The ridges in coral reefs act as barriers and can reduce wave energy by up to 97%, providing crucial protection from threats such as tsunamis.
• They help protect areas such as mangrove forests and seagrass beds that act as nurseries for marine animals, as well as human coastal populations.

Extracts from animals and plants living on reefs have been used to develop treatments

• Asthma, arthritis, cancer and heart disease.

Why are Coral Reefs Dying?

Climate Change

• Rising sea levels - increased sedimentation and the smothering of coral reefs.
• Increased sea surface temperatures - higher temperatures place coral under stress, which leads to bleaching events and coral reef death.
• Ocean acidification – Oceans absorb excess carbon dioxide in the atmosphere, decreasing the growth rate of coral and can affect their structure leading to more breakages.
• Changes to ocean currents - affect the amount of food available to coral, as well as the dispersal of coral larvae.
• Changes to storm patterns - increased strength and frequency of storms in the areas around coral reefs can destroy these delicate structures.

Destructive Fishing Practices

• Blast fishing (explosives detonated in the sea) - destroys coral reefs and other species.
• Overfishing - disrupt the delicate balance of a coral reef ecosystem.
• Cyanide fishing (sodium cyanide to temporarily stun fish) - cyanide also kills the coral polyps.
• Fishing gear - bottom trawling and beach seine nets can destroy great stretches of deep-sea coral reefs.

Pollution

• Increased sediment levels – effect the coral's ability to feed, reproduce, and grow.
• Increased nutrient levels (fertilizer runoff) - contribute to eutrophication and ocean dead zones, both of which can damage coral reefs.
• Litter and microplastics - caught on coral and block the amount of available sunlight + coral may consume microplastics that are similar in size to the zooplankton they naturally feed on.

Effect of Coral Reef Loss

The loss of coral reefs would be devastating to one of the world’s largest pools of biodiversity.

• Coral reefs help seed the ocean and provide shelter and food to a complex web of organisms that leads all the way up to man.
• Coastlines become more susceptible to damage and flooding from storms, hurricanes, and cyclones - Coral reefs act as natural barriers to shorelines
• The Ocean wouldn't be able to absorb as much carbon dioxide, leaving more CO2 in the atmosphere.
• The loss of the coral reefs would have a devastating impact on tropical countries’ economy

Effect of Coral Reef Extinction

The warmer our oceans get; the faster coral reefs die out - it only takes a water temperature spike of 1°C above average to cause coral to bleachClimate change has already killed half of the Great Barrier Reef’s coral in just two years. It’s only a matter of time until the last coral vanishes from the oceans.

The day the reefs disappeared; marine biodiversity would suffer huge losses.

• The ocean bottom would be taken over by forests of seaweed, and jellyfish would occupy the Ocean.
• For many unique species of fish in the ocean, corals are their only safe habitat.
• A lot of them would be lost for good - e.g., sea turtles.Since coral are filter feeders, they clean the water.
• Remaining species, including dolphins, would be left to survive in very murky waters.
• Climate change would furthr increase due to the loss of a Carbon Sink.

How are we Preventing the Loss of Coral Reefs?

Replanting efforts - scientists are breeding corals in special facilities that simulate different growing conditions and planting them in the sea:

• Looking for varieties that are tolerant to higher temperatures, ultraviolet light (a problem since we created a hole in the ozone layer), and acidity.
• One way of doing this is by exchanging the coral's algae species for more robust types.

• Creation and preservation of marine parks and reserves.
• Avoid touching reefs or anchoring boats on the reef.
• Use reef-friendly sun protection - some ingredients in sunscreen can be harmful to or even kill corals.
• Recycle and dispose of rubbish properly - Marine debris can be harmful to coral reefs.
• The overuse of fertilizers on lawns harm water quality - nutrients (nitrogen and phosphorus) from the fertilizer are washed into waterways and can harm coral reefs.

David Attenborough

“The greatest concern now is that we might lose the reef altogether."

“The Great Barrier Reef is in grave danger. If temperatures continue to rise at the present rate it will be gone with in decades. That would be a global catastrophe.”

“Do we really care so little about the Earth on which we live that we don’t wish to protect one of its greatest wonders from the consequences of our behaviour?”

Coral Reef Decline

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