Draft one - Adaptation and Survival of the Coral Reef System

This discussion topic submitted by Loren Savage ( lsfalcons@yahoo.com) at 9:27 am on 4/23/01. Additions were last made on Saturday, May 4, 2002.

Adaptation and Survival of the Coral Reef System
Adaptation and survival of the coral reef ecosystem is the focus of the following paper. Currently, the biology class I teach is embarking on one of their final projects, which involves studying coral reefs from both a biological and global perspective developed in their social studies class. The survival of the coral reef system calls for an understanding of many of the concepts and issues my biology class has covered: Ecology, Evolution, the animal kingdom and Physiology. Before they can understand the interdependence of the coral reef system, a basic understanding of a coral reef's organization must be presented.
"Coral reefs are the most complex and diverse communities in the sea (Jackson, 1991)." Their diversity of life can only be rivaled by the rain forest. The largest biological structures in the sea are created by reef building corals that produce structures through calcification. Calcification itself would not be possible with a symbiotic relationship a unicellular algae named zooxanthellae (Jackson, 1991).
Zooxanathellae use light for photosynthesis. Though coral are connivers, "it seems that light enhances oxygen production, which, in turn, stimulates coral metabolism and leads to increased calcium carbonate decomposition (Nybakken, 1996)." This symbiotic relationship is so important that coral will die without light. In turn, the coral provide a home for the Zooxanathallae to divide and thrive (Nybakken, 1996)."
The structures created by classification can vary in size up to several hundred tons. The shape of the coral is determined by the species of coral that created them. A single reef may have as many as 3000 animals living on it, dominated by coral (Lalli, 1993). Individual coral resemble sea anemones. These cnidarians live most of their life in the Polyp stage sessile or free living (Jackson, 1991). Tentacles containing stinging capsules called nematocysts are used to capture small plankton or small organisms. Some also have modified mucus used to capture prey (Lalli, 1993).
Coral have both asexual and sexual reproductive strategies. Asexually, coral can break apart in clonel fragments traveling short distances. Sexually, coral produce larvae from the gametes produced by the coral. This larvae can settle in a new area (Jackson, 1991). These two sexual strategies have been very important for the historical survival of coral.
Corals have survived over 200 million years. "Through extinction, hiatuses, and climatic oscillations, reef-building corals have survived (Buddemeier, 1999)." Adaptations such as the calcification and symbiotic relationships developed early are particularly important for this survival. Recently, many coral systems have been stressed (Pittock, 1999). How has coral survived these changes in the past and what adaptations will need to be overcome in this century?

Coral has survived many systematic changes (changes throughout any compartment of the earth's system) (Buddemeier, 1999). Carbon dioxide levels are important to coral in that increased atmospheric carbon dioxide decreases the available CaCO that can be used by coral for calcification. Decreased calcification, decreases habitat (Pittock, 1999). It is estimated that calcification rates have been reduced ten percent in the last one hundred and ten years. Global warming may be responsible for another reduction of twenty two percent in the next one hundred and ten years if current carbon dioxide level increase continues at the same rate (Buddemeier, 1999).
The burning of fossil fuels has been the main cause of global warming. Global warming is a theory that states increased level of carbon dioxide and methane are causing an increase in the greenhouse effect. These gasses are responsible for trapping heat around the earth and increased gas levels may be responsible for the increases in temperature on earth. A comparison of carbon dioxide levels from current day to concentrations sealed in ice core bubbles from Greenland show an increase in carbon dioxide levels from 200 parts per million to 370 parts per million during the last two glaciation (Pittock, 1999).
The earth's average temperature has risen one degree Celsius in the last thousand years. Comparatively, it is projected that the earth may have an increase of 4 degrees Celsius in the next one hundred years. Current trends call for an increase in carbon dioxide from 370 parts per million to 900 parts per million in 2100. Coral has to survive decrease classification due to carbon dioxide increase as well as a rise in the average temperature of water (Pittock 1999).
Coral have a zone of resistance, which is their level of temperature that they can survive. Enzymes that control metabolism are less efficient at the upper and lower zones of this range. Sea life can shift their metabolism in a process called acclimatization in which they can survive longer periods of ranges outside of their optimal level. Temperature of water controls the reproductive cycles and overall productivity of the whole aquatic system (Milne, 1995).
The devastating effects of temperature may also be manifested in changing weather patterns. Isotherms, which are cold bodies of water, move through natural phenomenon and move due to cyclone storms. Cyclones are predicted to become more frequent with global warming. Cold water colder than nineteen degrees Celsius destroys coral reefs. The shear force of water from these storms also devastates coral reef communities (Pittock, 1999).
Another systematic challenge involves increased rainfall regarding the water cycle. Global warming is once again responsible for this systematic change (Pittock, 1999). Coral placed in fresh water would swell up and die. Exposure to high salinity also causes the organism to die, as it would shrivel up. Osmosis is responsible for the creature's death in both cases. Osmosis is the movement of water through a membrane. Molecules are carried with it. Water moves in and out of the organism as salinity levels in and out of the membrane are naturally regulated to a level that should be equal inside and surrounding the organism (Milne, 1995).
Change in weather patterns will change the levels of salinity in many regions, as the amounts of fresh water runoff are partially responsible for salinity. Most marine invertebrates have adapted salinity levels in their body fluids and blood that is about equal to the salinity of seawater. Higher organisms can excrete salt through their kidneys or gills, or use active transport to eliminate extra salts (Lilli, 1993).
The final predicted adaptation that coral will have to generate regarding temperature involves rising sea levels. Sea level rises due to the green house effect and may drown many corals. Increased depths of the existing reefs will move many of the species out of the photic zone, killing Zooxanthellae in which coral can not live without. The predicted 10-meter rise in sea level is largely do to increased melting of the polar ice caps. These caps are retreating at greater rates than any time in recent history (Pittock 1999).
Coral reefs as a system have a tremendous turn over rate; species are constantly being replaced. It is theorized that the tremendous diversity in species has insured coral survival. Different species are particularly adept to surviving different conditions and catastrophes. The Elkhorn coral skeleton is very strong and can withstand tremendous wave forces. Foliaceous coral is very adept to surviving deep-water conditions because it is less dependent on symbiotic relationships (Jackson, 1991).
Succession stages can be compared to that of a deciduous forest. Many communities are controlled by systematic or catastrophic events that drive the community in a direction. This direction could have been determined hundreds of years ago. Communities shift; this shift can be studied through the fossil record. It is believed that the current patterns of the reefs resemble Jamaican patterns rather than what has been more of the constant patterns in the fossil record. Coral has found a way to adapt to systematic global changes throughout the last 200 million years. Hopefully, the coral reef system can adapt to the tremendous change in climate that humans are causing. Unfortunately, cumulative conditions must also be considered (Jackson, 1991).
Cumulative changes accrue at discreet location and are created by human beings (Buddemeier, 1999). For example, Cloroflorocarbons have decreased the ozone layer approximately four to five percent on average. This reduction of the protective layer is not universal with any measurable reduction of ozone in some tropical regions of the earth and much more significant increases in Polar Regions. Change in levels and frequencies of ultraviolet radiation may interfere with symbiotic relationships in the future (Pittock, 1999).
Communities developed around the Great Barrier Reef in Australia have created sediment in water that has increased turbidity. Photosynthesis was effectively eliminated by decreased phototropic zones destroying coral communities. Rain runoff from these communities has also brought pesticides and herbicides, which are poisoning communities. Sewage contamination has brought pathogens and fertilizer runoff has created algae blooms also destroying habitat (Pittock, 1999).
Added pressure from mining and fishing, which is destroying habitat, may be to much for the coral reef system to overcome (Pittock, 1999). The coral system has had millions of years to utilize the mechanisms of survival so brilliantly deducted by Darwin. Will the coral reef ecosystem be able to adapt to the blitzkrieg of cumulative threats? With the compounded systematic changes also being created by man, the future of the coral reef is uncertain.
"Planned adaptation, which involves conscious human interference, in some way can assist in the persistence of some desirable traits of the system that may be necessary (Pittock, 1999)." Limiting freshwater flow into a lagoon reducing pollutants and sediment may be a valuable conservation effort. Seeding areas that need help along their succession process, changing species composition by the addition, or eliminating species may all be steps necessary to preserve this ecosystem (Pittock, 1999). Conservation efforts have been successful in restoring terrestrial biomes; more research in positive human interaction should be explored.
In conclusion, our society is creating many systematic and cumulative challenges for the coral reef community to overcome. Technologies to reduce our emissions of greenhouse gasses need to be developed to ensure this system's survival. Regulations regarding cumulative pollution also need to be enforced. The diversity and adaptation of this system has ensured 200 million years of survival. The many variables and interdisciplinary nature of this system make it a difficult one to study. The research presented in this paper has synthesized many biological concepts into a more global understanding of the adaptations and challenges necessary for the survival of the coral reef system.

Works Cited
Buddemeier, Robert. "Coral Adaptation and Acclimatization: A Most Ingenious
Paradox." American Zoology. Ed. Kirk Miller. vol.39 page 1-9, 1999.
Jackson, Jeremy. "Adaptation and Diversity of Reef Corals." Bioscience. vol. 41
no. 7 page 475-480, 1991.
Lalli, Carol and Tim Parsons."Biological Oceanography: An Introduction.
New York: Peramon Press, 1993.
Milne, David. Marine Life and the Sea. Belmont, California: Wadsworth
publishing company, 1995.
Pittock, Barrie. "Coral Reefs and Environmental Change: Adaption to what?."
American Zoology. vol. 39 page 10 - 29, 1999.




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