Coral reefs are the most diverse and beautiful of all marine habitats.
Large wave resistant structures have accumulated from the slow growth of
corals. The development of these structures is aided by algae that are
symbiotic with reef-building corals, known as zooxanthellae. Coralline
algae, sponges, and other organisms, combined with a number of
cementation processes also contribute to reef growth.
The dominant organisms are known as framework builders, because they
provide the matrix for the growing reef. Corals and coralline algae
precipitate calcium carbonate, whereas the framework- building sponges
may also precipitate silica. Most of these organisms are colonial, and
the slow process of precipitation moves the living surface layer of the
reef upward and seaward.
The reef is topographically complex. Much like a rain forest, it has
many strata and areas of strong shade, cast by the overtowering coral
colonies. Because of the complexity, thousands of species of fish and
invertebrates live in association with reefs, which are by far our
richest marine habitats. In Caribbean reefs, for example, several
hundred species of colonial invertebrates can be found living on the
undersides of platy corals. It is not unusual for a reef to have several
hundred species of snails, sixty species of corals, and several hundred
species of fish. Of all ocean habitats, reefs seem to have the greatest
development of complex symbiotic associations.
Reef-building corals may occur in a variety of growth forms, and there
often is strong variation in coral shape even within a species. In this
photograph, we can see the branching elkhorn coral Acropora palmata
(upper left), with arms showing strong orientation into an oscillatory
current between left and right. In the right foreground is the
mound-shaped coral Montastrea annularis. It is of great interest that
such differently shaped corals can occur side by side. What might that
indicate to you?
Acanthaster planci is a carnivorous asteroid starfish whose principal
prey are corals. It has sharp dorsal spines that penetrate human skin
and cause sickness. Normally it occurs at low density and is nocturnal.
In the 1960s, population explosions were found all over the Indo-Pacific
and the starfish were moving in large numbers during the day. Instead
of being of minor impact, they were now major predators on the reef. In
Guam, for example, over 90% of the corals were killed. The explanation
of the origin of the outbreaks is still very controversial. Charles
Birkland suggested that they were related to storms that could wash out
nutrients from atolls, which stimulated phytoplankton grown, which, in
turn, increased the survival of starfish planktotrophic larvae. Others
have argued that larval starvation is not a limiting factor in larval
survival. It was also argued that typhoons and other storms killed
corals, causing starvation among the starfish and a switch to roving in
aggregations in search of food.
Pacific shallow reefs are often dominated by the the erect coral
Pocillopora damicornis. When the crown-of-thorns starfish tries to mount
and consume the coral, several species of shrimps and crabs that live
among the coral branches move to attack the starfish, thus defending the
An atoll is a ring- or horseshoe-shaped group of islands, surrounding a
lagoon. Coral reefs line the inner and outer parts of the island. Darwin
hypothesized that the earth's crust was slowly sinking, and that corals
were growing upward and keeping up with the overal sinking rate. At
first, a submarine volcano might be jutting out into the sea, but
sinking led to the ring of coral reefs around the volcano to grow
upwards and form the islands. While most agreed with this hypothesis,
the geologist Harry Ladd confirmed it by leading a drilling team to this
region. The team drilled through hundreds of meters of coral reef rock
before reaching volcanic rock below of Eocene age.
Coral Reefs are the "Rainforests" of the ocean. Reefs are ecologically
important ecosystems and have a high biodiversity that serves as a
storage bank of rich genetic resources. They are a source of food and
medicine, and they protect the coast from wave erosion. Coral reefs are
found in about 100 countries. Coral Reefs are home to over 25 percent of
all marine life and are among the world's most fragile and endangered
ecosystems. In the last few decades over 35 million acres of Coral Reefs
have been obliterated. Reefs off of 93 countries have been damaged .
When corals are stressed by high temperature, ultraviolet light or other
environmental changes, they lose their symbiotic algal cells, and
appear white (the white skeleton is actually visible through the
Climate change will destroy the world's great coral reefs within a
century, according to a report by German and Australian marine
The researchers say governments must take action now to reduce the emissions of gases such as carbon dioxide, which are thought to be behind a rise in average global temperatures.
The scientists combined their coral expertise with the latest climate
models to project what is likely to happen to the world's greatest reefs
if global warming remains unchecked. Their study suggests the unique
marine environments will increasingly become victim to a process known
as coral bleaching.
A slight rise in maximum water temperatures - only one to two degrees -
can stress the corals. This causes them to expel the microscopic
organisms, known as zooxanthellae, which color their tissues and provide
them with essential nutrients.
If they zooxanthellae do not return, the corals will die. In 1998, the
warmest year on record, every reef system in the world's tropical oceans
was affected by some degree of bleaching. The report says the frequency
and intensity of bleaching is set to rise.
The report's lead author is Professor Ove Hoegh-Guldberg, an expert on
coral bleaching at Sydney University. Coral reefs could be eliminated
from most areas of the world by 2100, Even the world's largest reef -
the Great Barrier Reef off Australia - could be dead within 30 years
unless measures are taken now to slow climate change.
Dolphin Reef "Coral Garden" One of the most amazing places around the world -Coral Reef-, in this case South Egypt -Red Sea-. I want to share with you the reef where I'd live if I was a fish. Dolphin Reef, light and colour, full of marine species, enjoy!
Amazing Coral Reefs One of the most amazing habitats on earth is found in warm, clear, shallow waters of tropical oceans worldwide. Tiny cup-shaped animals, called polyps, live in colonies, and when they die, their skeletons form a hard, stony, branching structure made of limestone.
under water see the under water secrets ..see the colorful coral reefs anf fishes
Thank you so much Dear Ee ...
Thank you very much,all these are fantastic.Wishing you all a good week.~For the Oceans~
Thank you Dear Mike - I'm happy you like it ...
Australia | Coral Reef
Beautiful world of hidden coral reef, fishes and colorful undersea nature