Coral Bleaching Erica Weston The Importance of Coral

Coral Bleaching Erica Weston

The Importance of Coral Reefs Coral 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 Reefs �Coral 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 Stressors �What causes coral to expel the zooxanthellea? �Rising water temperatures �Pollution �Overfishing �Natural disasters �Predation �Coral mining �Coral reefs are very fragile habitats.

Pollution and Natural Disasters �The 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 Dioxide �A study was done (Hii et al. 2009) that tested the effect of increased co 2 on two different species of coral. �Porites cylindrica and Galaxea fascicularis �The increased C 02 caused stress and reduced zooxanthellae in both species of coral and caused bleaching. �Degree of stress was species dependent.

Temperature and Predation �Corals 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, crabs, worms, and snails. � 1978 -1979 outbreak of crown-of-thorns starfish.

Coral mining and Overfishing �The 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 fishing �Cyanide fishing �Deep water trawling

Areas of Mass Coral Bleaching

Coral Evolution �The 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 (Mc. Clanahan et al 2007) showed that some corals seem to have acclimated to rising temperature and bleach less, though these areas are less diverse.

Coral Evolution �The 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 Co 2 levels, human interference in reefs by harvesting and fishing still pose a problem.

Protecting Coral Reefs �In 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. � Mc. Clanahan, 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/coral 11_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.