The Dynamics of Coral Reef Interaction Forms a Symbiosis


Palemahan - Coral reefs are not a static and simple system, but a dynamic and complex ecosystem. High primary productivity in coral reef ecosystems, which can reach 5000 g C/m2/year, triggers high secondary productivity, which means that the communities of living things in it are very diverse and available in abundant quantities. Various types of living things that exist in the coral reef ecosystem interact with each other, either directly or indirectly, to form a living system. Living systems on coral reefs can increase or decrease in dimension due to complex interactions between various biological and physical forces.

The Ecological Role of Coral Reefs
Coral reef organisms are a group of animals or plants associated with coral reefs, their presence is conspicuous and found in various micro-habitats on coral reefs. There are coral organisms that live sedentary and look for food in coral reef areas, so that if coral reefs are damaged or destroyed, coral organisms will also lose their habitat. As organisms whose lives are associated with coral reefs, the damage to coral reefs naturally affects  diversity and abundance of coral organisms. This diverse habitat can explain the number of coral organisms in these ecosystems [1].

The ecological role of coral reefs that is currently being highlighted is the function of coral reefs as carbon sinks that can reduce the effect of greenhouse gases. Carbon is a gas that can damage the ozone layer which results in global warming and global climate change. Coral reefs with their unique symbiosis with zooxanthellae are able to absorb carbon for photosynthesis by producing oxygen. The absorption of carbon can reduce the amount of carbon in the atmosphere.

Mutalalism Symbiosis between Coral Reefs and Algae
The role of zooxanthellae algae in coral bodies can utilize or absorb carbon as an energy source on the process of photosynthesis. The photosynthetic process that occurs in coral-algae symbiosis can trigger a calcification process that allows coral to build reefs. This coral reef is a habitat for many marine biota. Most of the reef building functions are formed by reef building (hermatypic) corals, which form massive limestone (aragonite) deposits. Hermatypic corals contain zooxanthellae symbiont algae which greatly speed up the classification process, thereby enabling their host corals to build massive colonies [2].

Zooxanthellae provide food for corals which is formed through the process of photosynthesis, whereas corals provide protection and access to light to zooxanthellae. Thus a unique mutualism symbiosis occurs between hermatypic corals and zooxanthellae. Corals as “hosts” and coral reef symbionts are photosynthetic dinoflagellate algae that live in the host animal cells. Thus the symbiosis takes place very tightly (intracellular endosymbiosis) [3].

Zooxanthellae are concentrated in the gastrodermal cells of polyps and tentacles. During photosynthesis, zooxanthellae fix large amounts of carbon that are passed to their host polyps. This carbon is mostly in the form of glycerol including glucose and alanine. These chemical products are used by polyps to carry out their metabolic functions or as building blocks in a series of proteins, fats and carbohydrates. Zooxanthellae also increase the ability of corals to produce calcium carbonate. The photosynthetic results of zooxanthellae which are utilized by corals, are sufficient to meet the needs of the coral respiration process and 95% of coral food sources come from zooxanthellae [4].

Symbiosis of Parasitism between Coral Reefs and Starfish
The Population Explosion of Acantaster planci has had an impact on coral death and reef structure. In 1981-1982 there was a population explosion which killed a very wide range of corals. These animal attacks cause 90% of coral reefs to be damaged. This animal boom occurred because its predator, Charonia tritonis, was taken and sold as decoration and runoff which led to an increase in nutrition. Population growth of Acanthaster planci threatens the survival of coral reefs in the Coral Triangle region in Indonesia. This area is a coral reef area with the highest biodiversity in the world.

The spiny starfish known as the Crown of Thorns Starfish is a ferocious predator for coral reef-forming biota. Starfish prey on coral by covering the surface of the coral reef with their stomachs and producing digestive enzymes that damage the coral's soft tissue. Acantaster planci is a serious threat to coral reefs around the world, especially in the Indo-Pacific region. Mass destruction was found in many places around the world. This population explosion has reduced the number of live corals in many places over the past 30 years.

The sea star Acanthaster planci is one of the big potential problems faced in coral reef management. Among the existing coral predators, Acanthaster planci is the most dangerous coral predator when an outbreak occurs, so that almost all living corals are preyed upon by Acanthaster planci. This animal directly eats living coral tissue which is capable of eating about 5-13 m2 of live coral reefs. This of course can cause coral damage when compared to the average growth of coral which is only 1-2 cm per year [5].

[1] Luckhurst, B. and K. Luckhurst. 1978. Analysis of the influence of substrate variable on coral reef communities. Mar Biol 49:469-478.

[2] Levinton, J. S. 1995. Marine Biology: Function, Biodiversity, Ecology. New York: Oxford University Press.

[3] Lalli, C.M., and T. Parsons. 1995. Biological Oceanography: An Introduction. Oxford: Butterworth-Heinemann Ltd 

[4] Sebens,  K.P.1987.  Coelenterata.  In  T.J. Pandian  and  F.J.  Vernberg  (eds). Animal energetics. Academic Press, San Diego California

[5] Giyanto, Manuputty A EW, Abrar M, Siringoringo R M, Suharti S R, Wibowo K, Edrus I N, Arbi U C, Hendrik A.W. Cappenberg, Sihaloho H F, Tuti Y, Anita DZ. 2014. Panduan Monitoring Kesehatan Terumbu Karang. Jakarta :CRITC COREMAP CTI - LIPI. 63 hlm.

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