Erica Weston

The Importance of Coral ReefsCoral reefs are like

the rainforests of the sea

Biologically diverse Support 33% of

marine fish species

Provides medicines, chemicals, and other resources .

The Importance of Coral ReefsCoral reefs attract tourists to island, many of

which are impoverished and provide revenue.

Reefs provide a barrier to prevent erosion and protect from storms and floods.Provided millions of dollars worth of services

What is Coral Bleaching?Coral reefs get their bright colors from a mutualistic

relationship with algae called zooxanthellae.

Zooxanthellae live in the coral and receive shelter and compounds needed for photosythesis.

Corals receive food from the zooxanthellae’s photosynthesis products.

this allows coral to secret calcium carbonate and grow.

What is Coral Bleaching?The tropical waters that corals grow in are

very nutrient poor.During photosynthesis the algae make

oxygen. Corals use oxygen to remove wastes.Zooxanthellea also provide the coral with

glucose, glycerol, and amino acids.

What is Coral bleaching?When the coral is under

stress it will expel it’s zooxanthellae.

This makes the coral appear “bleached”

The coral can no longer build its calcium carbonate skeleton.

Can regain zooxanthellae if stress is reduced. If not, corals can die.

Coral StressorsWhat causes coral to expel the

zooxanthellea?Rising water temperaturesPollutionOverfishingNatural disastersPredationCoral mining

Coral reefs are very fragile habitats.

Pollution and Natural DisastersThe zooxanthellea need light from the sun for

photosynthesis.If pollution causes the water to be cloudy the

sunlight cannot reach the zooxanthellea and they cannot produce the byproducts the coral depend on.

Natural disasters can also cause the water to become cloudy with sediment and block the sunlight.

Natural disasters can also tear coral reefs apart and extreme low tides can cause them to dry out and die.

Increased Carbon DioxideA study was done (Hii et al. 2009) that tested

the effect of increased co2 on two different species of coral. Porites cylindrica and Galaxea fascicularis

The increased C02 caused stress and reduced zooxanthellae in both species of coral and caused bleaching.

Degree of stress was species dependent.

Temperature and PredationCorals live in a narrow temperature margin.A rise in temperature in 1-2 degrees for 5-10

weeks can cause bleaching.Corals are also venerable to predation from

starfish, fish, crabs, worms, and snails.1978-1979 outbreak of crown-of-thorns

starfish.

Coral mining and OverfishingThe most devastating threat to corals come

from humans.Many coral reefs are harvested for aquarium

fish and decoration, jewelry, or building materials.

Certain fishing techniques also kill coral.Blast fishingCyanide fishingDeep water trawling

Coral EvolutionThe coral expelling their zooxanthellae may be

an adaptation so they can acquire different zooxanthellae that can withstand the environmental stress.

Some studies have shown an increased tolerance in certain coral species (Maynard et al. 2008) when comparing the damage from a bleaching event in 1998 and a bleaching event in 2002.

Another study (McClanahan et al 2007) showed that some corals seem to have acclimated to rising temperature and bleach less, though these areas are less diverse.

Coral EvolutionThe future of coral reefs will highly depend

on how quickly and efficiently they can adapt to global changes.

Although some coral species appear to be evolving a tolerance for higher temperatures and Co2 levels, human interference in reefs by harvesting and fishing still pose a problem.

Protecting Coral ReefsIn 1998 the United States established the

Coral Reef Task Force (CRTF) to protect and conserve coral reefs.

The CRTF monitors and maps US coral reefs and researches causes of coral bleaching. They also work on finding ways to prevent bleaching.

To fully protect reefs legal action may be needed such as Marine Protected Areas.

Works Cited Buchheim Jason. Coral Reef Bleaching. 1998.

http://www.marinebiology.org/coralbleaching.htm. April 2010. Maynard, J. A., Anthony, K. R. N., Marshall, P. A. Masiri, I. 2008. Major

bleaching events can lead to increased thermal tolerance in corals. Marine Biology 155: 173-182.

McClanahan, T. T., Ateweberhan, M., Muhando, C. A., Maina, J., Mohammed. M. S. 2007. Effects of climate and seawater temperature variation on coral bleaching and mortality. Ecological Monographs 77: 503-525.

National Oceanic and Atmospheric Administration. March 25,2008 http://oceanservice.noaa.gov/education/kits/corals/coral11_protecting.html. April 2010.

Yii-Siang Hii, Abol Munafi Ambok Bolong, Teng-Teng Yang, and Hock-Chark Liew, “Effect of Elevated Carbon Dioxide on Two Scleractinian Corals: Porites cylindrica (Dana, 1846) and Galaxea fascicularis (Linnaeus, 1767),” Journal of Marine Biology, vol. 2009, Article ID 215196, 7 pages, 2009.