How Corals Form

When hard corals grow in one specific area and				green algae and thus the discoloration of the
gather as one huge colony, they form a coral				corals. Since these algae are not only responsible
reef. The reefs are formed by the limestone				for the outer color of the corals but for the
skeletons of these tiny coral polyps, consisting of				continuous photosynthesis as well, bleaching may
a fleshy sack with a ring of tentacles. These				often result to the coral's death.
corals are the subphylum Anthozoa.				What really are the geographical qualities that are
One might find it hard to imagine that such				ideal for coral growth and survival? First, corals
non-locomotive skeleton-like creatures are in fact				need warm sea water, between 18°C and
alive and that they even have very active				30°C. Cold water can only hinder the
symbiotic relationships with other creatures found				development of corals. This explains why they are
under the sea.				usually found in the tropical areas and not in the
Thus, it might be important to unravel an				cold corners of the earth. In fact, most coral
underwater mystery occurring between the				reefs are found where sea temperatures are
corals and the rest of the sea life.				warmest, mostly between 30 degrees north and
An indispensable symbiotic relationship is present				south latitude.
among these reef-building corals and zoxanthellae,				Another important aspect for the growth of
a type of brown algae scientifically known as				corals is a good access to sunlight. As we all
Symbiodinium microadriaticum. Within the				know, light from the sun is needed for
hermatypic corals (the coral's skin) dwell millions of				photosynthesis, which in the case of the corals
these single-celled objects. The zoxanthellae help				are performed by the green algae. The clearer
the coral in the production of calcium carbonate or				and shallower the water, the better are the
what we commonly know as limestone. They do				corals' growth. There should not be too much
this by aiding in the production of sugars and				sediment in the water as they can smother the
oxygen through a photosynthetic process, a				polyps. Too much fresh water also prevents coral
process attributed to any living organism existent				growth development; this explains why it is
on the earth. Due to the zooxanthellae's ability to				impossible to find a colony of corals in the mouth
aid the coral in its production of calcium and sugar				of the river.
for its continuous bodily formation, corals fast				Coral reefs are habitat of up to 2 million varieties
growth can be credited to the tiny zooxanthellaes.				of marine plants and animals, resulting to a very
Furthermore, the zooxanthallae is not only				extraordinary diversity. Coral reefs are known to
responsible for the skeletal growth of the corals,				be home to a number of species of tropical and
it also gives it its other aesthetic characteristic - a				reef marine fish, either swimming right adjust the
greenish color.				corals or swimming right above or the surrounding
A phenomenon called coral bleaching, in which the				area of the reef. Reefs are also haven to a large
coral's outer color from turns from greens to				variety of other sea organisms such as spongers,
totally white, may occur. Some factors that may				echinoderms, mollusks, and a whole lot more.
cause coral bleaching are changes in environmental				These creatures are part of the food chain in the
conditions, such as sudden warming of the				reef, all contributing greatly in the marvelous
temperature and a change in the salinity of the				underwater ecosystem that keeps each coral
sea water. Also, diseases, often cause by				alive.
pollution, may cause the polyps to expel the little

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How Corals Form