Coral Reefs

What is a coral reef? Ecosystem Community of living organisms Exist since millions of years The reefs that we see today had to grow for around 10,000 years Grow really slowly One quarter of animals in the ocean find shelter in coral reefs But not a lot of the ocean’s ground is covered by coral reefs The biggest coral reef: Great Barrier Reef (Australia)

Where are coral reefs located? Coral reefs cover 284,300 km^2 -> 0.1% of the ocean’s ground Most of it is in the Indo-Pacific region In temperate and tropical waters Optimum temperature = 26 to 27 °C

How do coral reefs form? Free-swimming coral larvae connect to submerged rocks Located at edges of islands/ countries at the sea Slowly growing -> 0.3 to 10 cm per year Three structures: 1. fringing: most of the reefs / it has borders around the shoreline / goes around the island 2. barrier: borders around shorelines too (further away) / separated from island or country by deep water 3. atolls: circular / central lagoon / gaps in the reef (good shelter for animals) They can take 100,000 to 30,000,000 years to develop fully

What is the structure of a coral reef? The main structure of a coral reef is polyps Polyps are coral organisms They are related to sea anemones and jellyfish They have a base made of limestone skeleton (calicle) There are many layers in coral reefs; only the top one includes living polyps The reef uses the polyps as protection: polyps have little tentacles that can sting attacking enemies Polyps are also used to catch food (zooplankton)

Why are coral reefs special? They are important for the life in the ocean: Absorb wave energy so shorelines do not get damaged Place for fishes to release eggs (left picture) Gives a home to many ocean animals (right picture)

How do humans benefit from coral reefs? Coral reefs provide food -> seafood (“food” lives in coral reefs) Healthcare: Since the 21 st century Against cancer, arthritis, human bacterial infections, Alzheimer’s disease, heart disease, viruses and other diseases Research is still in process Tourism: Local citizens gain money from tourists who want to see the coral reefs

Coral reefs also contribute help to the carbon cycle: Site to two processes in the cycle: 1. organic carbon metabolism (photosynthesis and respiration) 2. inorganic carbon metabolism (calcification and dissolution of calcium carbonate)

What are the threats to coral reefs? Tourists: They want to take souvenirs back home and try to remove parts of the reef They empty their waste into the sea because they are not aware of the impacts sometimes Interrupted food chain caused by overfishing Sewage: causes overgrowth of algae (would affect that there is not enough sunlight for coral reef) Coral Mining: humans use the first layer of coral reefs (which is alive) as road- fill or cement (causes long-term damages) Climate Change: temperature cannot be too high otherwise coral reefs cannot survive OCEAN ACIDIFICATION

What is ocean acidification? Most significant threat for coral reefs Chemical reactions CO2 from atmosphere is absorbed by seawater; CO2 bonds with seawater and forms carbonic acid which releases a bicarbonate ion and a hydrogen ion; hydrogen and another carbon ion bond to form a bicarbonate ion Chemical reactions reduce seawater pH, carbonate ion concentration and saturation states of calcium carbonate minerals Calcium carbonate minerals are contained in shells and skeletons (which are needed in coral reefs) Due to these reactions there is not enough carbonate to create skeletons The higher the ocean acidification (OA) is the harder it is for coral reefs to produce their skeletons

When coral reefs have to rebuilt it is nearly impossible with an increasing ocean acidification It is increasing because the CO2 concentration in the atmosphere is increasing with the global warming This also affects all the animals living in the coral reefs because the space is becoming rare In addition it is expensive for humans to protect the shoreline They also try to keep the pH of the seawater high which is expensive too Tourism is decreasing so the local citizens do not gain so much money anymore A positive aspect is that coral reefs are needed at the moment because there is research going on looking at cancer medicine which is found in coral reefs Therefore they have to invest money to protect them

What can we do to protect coral reefs? Use less water -> less waste water in oceans Do not put chemicals into waterways Do not touch coral reefs when you go diving You can help out in holidays in local beaches

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