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The main cause of coral bleaching is heat stress resulting from high sea temperatures. Temperature increases of only one degree celsius for only four weeks can trigger bleaching events.
The leading cause of coral bleaching is climate change. A warming planet means a warming ocean, and a change in water temperature—as little as 2 degrees Fahrenheit—can cause coral to drive out algae. Coral may bleach for other reasons, like extremely low tides, pollution, or too much sunlight.
What causes coral bleaching? The ocean heats, which makes the coral expel the algae, which makes them leave the tissue in the coral, turning the coral completely white.
Which of the following is NOT a trigger of coral bleaching? death of zooxanthellae whaling acidification increased water temperature.
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Bleached corals are likely to have reduced growth rates, decreased reproductive capacity, increased susceptibility to diseases and elevated mortality rates. Changes in coral community composition can occur when more susceptible species are killed by bleaching events.
As the Earth’s temperature warms due to global warming – so does the risk of mass bleaching – as seas get warmer. Coral bleaching can be devastating – it has the potential to wipe out whole ecosystems – as wildlife around the coral can no longer find food, they move away or die, creating barren underwater landscapes.
9-12 years
The leading cause of coral bleaching is rising water temperatures. A temperature about 1 °C (or 2 °F) above average can cause bleaching.
Reef-building corals can make unexpected recoveries from climate change-induced destruction. They discovered that seemingly dead corals can in fact regrow in the wake of heat damage caused by climate change. Some made an almost full recovery.
Reef-building corals cannot tolerate water temperatures below 64° Fahrenheit (18° Celsius). Many grow optimally in water temperatures between 73° and 84° Fahrenheit (23°–29°Celsius), but some can tolerate temperatures as high as 104° Fahrenheit (40° Celsius) for short periods.
Greenhouse gas emissions are the main cause of ocean acidification and the increases in sea temperature that cause coral bleaching. Any efforts to reduce emissions will bring benefits both on land and at sea. However, global greenhouse gas emissions have risen steadily in recent years.
Severe heat stress causes bleaching (the expulsion of corals’ food-producing algae). Ocean acidification (the drop in seawater pH as the ocean absorbs carbon dioxide) reduces the availability of calcium minerals for skeleton building and repair. The combination of these two threats poses a Catch-22 for coral reefs.
Ocean acidification is just one more threat to the success of hard corals. Coral reefs are already being affected by many other pressures, some human-related and some natural. Warming ocean temperatures are contributing to coral bleaching and making them more susceptible to diseases.
No coral reefs, means no oxygen from the ocean. Coral reefs protect coastlines from storms and erosion, provide jobs for local communities, and give us a free playground. They are also are a source of food and new medicines.
Age estimate places coral among the most long-lived species on the planet. Some species of coral can live for over 4,000 years — longer than any other animal that lives in the ocean, a study has found.
Corals usually develop into one of three characteristic structures: fringing reefs, barrier reefs or atolls. Learn more and view a larger image. As coral reefs grow, they establish characteristic biogeographic patterns. Learn more and view an animation.
Sunlight: Corals need to grow in shallow water where sunlight can reach them. Corals depend on the zooxanthellae (algae) that grow inside of them for oxygen and other things, and since these algae needs sunlight to survive, corals also need sunlight to survive.
Corals are animals And unlike plants, corals do not make their own food. Corals are in fact animals. The branch or mound that we often call “a coral” is actually made up of thousands of tiny animals called polyps. A coral polyp is an invertebrate that can be no bigger than a pinhead to up to a foot in diameter.
Look at the color and shape. Old dead corals will be broken down, and lack a healthy color, and are sometimes covered in algae. Corals that have been bleached from rising ocean temperatures turn white when the symbiotic algae leaves the coral. In some rare circumstances these may recover if the algae returns.
Don’t touch! Corals are fragile animals. Be careful not to touch, kick or stand on the corals you see in the water because this may damage or even kill them.