Coral Bleaching
Coral reefs are the most biodiverse ecosystem on the planet. There are more than 25,000 known species of organisms and countless others that have yet to be identified (Helvarg, 2000). Reefs thrive on the shallow edge of tropical seas, most often on the eastern edge of continents along warm water currents that brush the coasts. Reefs cannot live in cold waters and are limited by ocean depth and available sunlight. Coral is the foundation of the reef community, providing a three-dimensional structure where thousands of species of vertebrates and invertebrates live and feed. Some species of coral are hard, while others soft. Some are branched, yet others are compact and rounded. Coral is made up of large communities of tiny jellyfish like polyps. These polyps absorb calcium from the sea water and secrete a hard limestone skeleton. At night the polyps extend sticky, stinging tentacles from their skeletons to capture and consume small floating organisms such as zooplankton. Every coral has a two-stage life cycle: the larva, and the polyp. The larval stage is free swimming, and the polyp is stationary. Ocean currents carry the larva from the stationary parent polyp to any hard, clean, silt-free surface where, if the conditions are perfect, the larva grows into a coral forming polyp, never to move again (Levin, 1999). One of the most valuable resources for coral polyps are algae. Some live on the coral skeletons, but one type in particular, zooxanthellae, lives inside the tissue of the polyps. Zooxanthellae makes up about half the weight of the fleshy polyps and are not only a valuable food resource, but they are responsible for the brilliant colors associated with coral. When coral looses these prec...
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... as Helvarg (2000), Winiarski (19998) and Warrick (1999) have the benefit of being able to describe what coral bleaching is and it’s probable causes in a much more concise and to-the-point fashion.
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References
Gates, R.D., and Edmunds, P.J. 1999. The Physiological Mechanisms of Acclimatization in Tropical Reef Corals. American Zoologist; Vol. 39, No. 1 (Feb. 1999), pp. 30-43.
Huppert, A., and Stone, L. 1998. Chaos in the Pacific’s Coral Reef Bleaching Cycle. The American Naturalist; Vol. 152, No. 3 (Sept. 1998), pp. 447-459.
Levin, T. 1999. To Save a Reef. National Wildlife; Vol. 37, No. 2 (Feb./Mar. 1999), pp. 20-29.
Warrick, J. 1999. Warm Weather Destroyed Corals in ’98, Report Says. Houston Chronicle; March 8, 1999, p. 6.
Winiarski, K. 1998. Coral in Peril as Reefs Suffer Worldwide. USA Today; October 19, 1998, p. 04A.
The outer layer of a reef consists of living animals, or polyps, of coral. Single-celled algae called zooxanthellae live within the coral polyps, and a skeleton containing filamentous green algae surrounds them. The photosynthetic zooxanthellae and green algae transfer food energy directly to the coral polyps, while acquiring scarce nutrients from the coral. The numerous micro habitats of coral reefs and the high biological productivity support a great diversity of other life.
Earth, an endless source of wonder and beauty, produced the Great Barrier Reef. Hustling and bustling, the Reef thrives like a busy city, teeming with life. Sheltering thousands, corals, maintain the well-being of the Reef; however, the world threatens its nature and delicacy. Populations growing and technological advances increasing, the world becomes more and more disconnected with the natural world, posing an alarming risk for the planet we live on. Although many organizations try to keep the oceans clean, because of human interference and unnatural occurrences, the Great Barrier Reef needs scientific help to adapt corals to new conditions for means of survival, putting pressure on the Australian government to save their ocean environment.
This article discusses how important the organisms symbiotic with coral reefs are, as well as how important coral reefs are to our environment. Also explained is how natural and non natural things things like hurricanes and overfishing affects them. A study is quoted about how water acidity also plays a role in the bleaching of corals. Lastly, restoration and conservation efforts are discussed and how we could possibly help our oceans.
Coral Reefs are said to be the “tropical rainforest” of the sea. They are home to over 25% of all marine life (http://coralreefalliance.org.stories/storyReader$77). Over the past few decades they have been subjected to destructive anthropogenic practices. Some of the major threats to coral reefs include sedimentation, water pollution, harmful recreational activities, and global warming. All of these things cause stress on corals and can potentially cause mortality. Corals are made up of two parts, a polyp and zooxanthellae. A polyp is a calcerous body that grows from a hard part of the ocean floor. Zooxanthellae is a photosynthetic algae which lives in the polyp and provide energy for themselves and the coral. In many cases, corals undergo “bleaching,” which is a process where corals lose the zooxantheallae or chlorophyll pigment, and turn white (Wilkinson et all). After bleaching corals can survive for several months. It is possible for corals to recover by hosting more zooxantheallae, but it can take between 5 and 50 years for them to recover completely (Wilkinson et all, 1999).
Leading scientists advise climate change will cause increases to the frequency and intensity of extreme weather events. Rising sea levels pose a significant risk to coastal communities, while the world’s oceans could become too acidic to support coral reefs and other calcifying marine organisms. Coral reefs contain only six per cent of the area of the Great Barrier Reef, yet they provide critical habitat and food for numerous species in the ecosystem. However, climate change has already impacted coral reefs in the Great Barrier Reef as corals are very helpless against its potential impacts. Eight mass coral bleaching events has occurred since 1979, triggered by unusually high water temperatures. And because of this, zooxanthellae (photosynthetic algae) leave their tissues and corals will have no more colours hence ‘bleaching’. Without the zooxanthellae, the corals that remain gradually starve to death. Once the coral dies, fish and a multitude of other marine species are soon affected. Rising sea levels and more frequent and intense storm surges will see more erosion of Australia’s coastline, causing community and residential
All over the world coral reefs play an important part in our environment. Not only are the reefs colorful and beautiful to look at but the coral reefs house several different types of fish and other sea creatures. Coral reefs have started to decline over the years due to “climate change, El Nino events, overfishing, pollution and other pressures” (Newnham 1). A healthy coral reef can also collapse due to a natural disaster (Newnham 2). There can be several different reasons why a coral reef has started to decline or has been destroyed.
Certain symbiotic algae (zooxanthellae) attach to coral and actually give the coral its color. When temperatures get too hot the symbiotic algae pack up their bags and leave the coral, resulting in a bleaching effect on the coral.
Corals are a type of animal called a polyp, the simplest of predators that eat meat in the form of drifting zooplankton…all corals have boarders, zillions of microscopic, one-celled plants called zooxanthellae that live inside the polyps and transform sunlight into oxygen, keeping the corals alive. As you will see, the corals need these algae in order to live, but too much is deadly.
Sweatman, H, Delean, S, & Syms, C 2011, 'Assessing loss of coral cover on Australia's Great Barrier Reef over two decades, with implications for longer-term trends', Coral Reefs, 30, 2, p. 521-531, Scopus®, EBSCOhost, viewed 28 April 2014.
Rates of coral calcification on the Great Barrier Reef and many other reef systems around the world have declined by 15-20% since 1990 due to increasing thermal stress (De’ath 2012). It has already been mentioned that the oceans absorb almost all of the excess heat from climate change. This affects coral reef systems in what is known as coral bleaching. The term bleaching refers to the loss of corals’ colors. A coral’s color is the result of the zooxanthellae present.
The leading natural cause of destruction among the coral reefs is global warming. Global warming causes the bleaching of coral reefs to occur. Bleaching is a response to stress by the coral reef that happens when the water becomes to warm. The coral then put out a brownish zooxanthelle which causes them to lose their color. Without the zooxanthelle, the corals cannot provide nourishment for itself and th...
Climate change has been affecting coral reefs in a negative way. If the climate continues to get warmer more of our coral reef become bleached, the structure of the reefs will become weak, and algae that keeps coral healthy will die. In the essay, “A framework for understanding Climate change impacts on Coral Reefs” by Joshua Clinner (2016), he emphasizes our climate change has become one of the long-term threats to coral reef. The article “Climate change and human impacts are damaging the world’s coral reefs”, which didn’t include an author (2001), states that the sea temperatures throughout the tropics has increased dramatically leaving much of the coral unhealthy. Spencer Hall (2008), discussed in his article “Coral Reefs and Climate Change”, how the increase in climate change puts a lot of stress on coral reefs because they are very sensitive to the change of temperature. Rigel B (2003) states in his essay, “Climate Change and Coral Reefs”, that coral reef has already been negatively impacted by
Additionally, coral reefs are a critical environmental resource. Often referred to as the “rainforests of the sea,” reefs are some of the most diverse and productive ecosystems on earth. Reefs are home to a diversity of plant life, providing a wealth of food for fish. As they do with shoreline, reefs shelter marine life from waves and storms. Due to their unique ecological properties, coral reefs “support more species per unit area than any other marine environment.” But these ecosy...
Coral reefs are said to be the foundation for many marine species, and are a crucial support for human life. The coral reef ecosystem is an a diverse collection of species that interact with each other and the physical environment. Coral reefs are the homes of many species including crabs, shrimp, oysters, and clams, foods eaten by humans on a daily basis. Coral reefs are among the most diverse and biologically complex ecosystems on earth, supporting 33% of marine fish species. Research has shown that there exist a host of dangers for these precious species that are living in our very oceans and alongside our seashores, and these are some pertinent questions that need to be addressed in order to establish whether coral reefs are needed for our future existence and to global warming:
Coral reefs need to be preserved for many reasons. In this paper, I will discuss a few of them. First of all, they house a collection of diverse organisms, and contribute to fisheries which provide food items such as fish, crustaceans, and mollusks. Furthermore, coral skeletons are being used as bone substitutes in reconstructive bone surgery and may be able to provide important medicine, including anti-cancer drugs and a compound that blocks ultra-violet rays, they even help reduce global warming by taking carbon dioxide out of the air. These reefs provide a habitat for many species.