The growing of coral reefs is nowadays the
most visible "geological" formation. The deformation of rocks has
been done, except of vulcanic activity the reefs are the only
active power which change the surface of our planet. And also the
man helps with the creation. He sank the old boats to the bottom of
the sea to provide the corals the possibility to create new coral
atoll. The Red Sea is known as the most beautiful coral region. And
what are these amazing employees of the Earth?
Coral Reefs
Coral reefs can be made up of hundreds of
different species of coral. There are two main types: "hard" coral
with an outer skeleton of calcium carbonate (CaCO3) and "soft"
corals that embed bits of CaCO3 inside their bodies. Although it
comes in many shapes and sizes, all coral is composed of tiny
individual polyps. A polyp is a tiny animal that looks like an
upside-down jellyfish.
In soft corals, each polyp contains little
spikes of CaCO3 that help hold many polyps together in structures
that look like fans or whips. 
In hard corals, polyps
sit inside little cups which they build out of calcium carbonate.
Many of these cups are cemented together to make up a coral colony.
Reefs are formed when hundreds of hard coral colonies grow next to
and on top of each other. Since most species of coral polyps stay
deep within their calcium carbonate cups during the day, the casual
observer may think of coral as inanimate rocks. At night, however,
the polyps emerge, and wave their tiny stinging tentacles in the
water to catch microscopic organisms called plankton.
What makes coral polyps so unique is that
plankton is only part of their diet. Each polyp harbors within its
body special algae called zooxanthellae. These one-celled plants
use sunlight and carbon dioxide to conduct photosynthesis, a
process that produces oxygen ... and other nutrients needed by the
polyps. In return, the algae get protection and a constant supply
of carbon dioxide and other raw materials they need for
photosynthesis. Such a mutually beneficial relationship is called
symbiosis. Without this special relationship, it is likely that
there would be far fewer animals in clear, tropical waters since
they typically cannot support life. It is important to realise that
the fish, crabs, snails, worms and other reef creatures depend on
the health and growth of the coral reef for their existence.
Types of reefs
Coral reefs are divided into four main types:
fringing reef, platform reefs, barrier reefs and atolls.
Fringing reefs are relatively young. They can develop in
shallow waters along the coast of tropical islands or continents.
The corals grow upwards to sea level or just below and outwards
towards the open ocean. Fringing reefs are generally narrow
platforms a short distance from shore and don't contain a
substantial lagoon.
Platform reefs usually lie in sheltered seas and quite far
offshore. They are flat-topped with small and very shallow
lagoons.
Barrier reef - A coral reef growing parallel to the
coastline and separated from it by a lagoon is called a barrier
reef. The lagoon may develop between the fringing reef and the
land. As the reef continues to grow further and further offshore it
eventually reaches the edge of the continental shelf. Barrier reefs
can also originate offshore if the depth of the seabed out there is
shallow enough to allow corals to grow.
Atolls are rings of reef, often encircling an island (sand
and coral rubble). They typically have a shallow, sandy, sheltered
lagoon in the middle. Access to the open sea beyond is through a
number of channels. These provide fresh and colder water for the
lagoons. Corals atolls are on the top of submarine mountains. These
mountains are remnants of volcanos. Once there were fringing reefs
around the volcano. As it slowly submerged the corals continued to
grow up to the surface of the water. What remained after the
volcano became invisible is a ring of coral reefs surrounded by
deep ocean.
 |
 |
 |
 |
| Fringing reef |
Platform reef |
Barrier reef |
Atoll |
However some atolls were probably formed by
rising sea levels rather by the sinking of islands. Other theories
suggest that corals colonized eroded limestone formations, so
called karstic saucers.
a fringing reef surrounding an active volcano - subsidence of the
seafloor or rising sea levels
shrinking of the island - an atoll results when the island has
disappeared
Reef morphology
Reefs are often referred to as the "rainforests
of the oceans". Coral reefs host an extraordinary variety of marine
plants and animals (perhaps up to 2 million) including one quarter
of all marine fish species. The wide variety of habitats depends a
lot on the morphology of the coral reef. The differences in
temperatures, light, exposure to waves and tides, currents and the
amount of food available result in different habitats and
niches.
A) Mud flats close to shore with tide pools - B)
Mangroves - C) Seagrass bed - D) Patch reefs on inner reef slope -
E) Inner lagoon - F) bottom with mud - G) Pinnacle - H) Outer
lagoon - I) Fine sand - K) Acropora corals - L) Algae ridge - M)
Sand and rubble - N) Gorgonians and black corals - O) Cave or
overhang
Rás Muhammad (Ras Mohamed / Ras Mohammed)
Ras Muhammad is a national park in Egypt at the
southern extreme of the Sinai Peninsula, overlooking the Gulf of
Suez on the west and the Gulf of Aqaba to the east. The park is
situated in the tourist region of the Red Sea Riviera, located 12
km from the city of Sharm-el-Sheikh. The park spans an area of 480
km⊃2;, including 135 km⊃2; of surface land area and 345
km⊃2; area over water. Marsa Bareika is a small bay inlet in Ras
Mohammed, and Marsa Ghozlani is a very small inlet located across
from the park visitors center.
Coral reef ecosystems found in the National Park
are recognized internationally as among the world's best. This
recognition is based primarily on the diversity of flora and fauna,
clear warm water devoid of pollutants, their proximity to
shorelines and their spectacular vertical profile. The reef exists
as an explosion of color and life in stark contrast to the
seemingly barren desert adjacent to it. In reality, the desert is
rich in fauna, mainly nocturnal. These ecosystems are intrinsically
linked and thus must be managed as a single unit. The National Park
offers outstanding coral reef and nature viewing experiences to the
visitor. The Eel Garden, named for its population of garden eels at
20m, also provides excellent and calm conditions. The Main Beach,
often crowded, remains one of the best locations to see vertical
coral walls. Access is restricted to the left side of the bay. The
Old Quay, often calm but having more turbid water, has some of the
best shallow water reef structure.
Your tasks
- In Ras Muhammed (on surface area) you can find great crack
formations in the earth. Is there fresh or salt water?
- How many species of corals were found in Ras Muhammad?
- Put photo of you with GPS on the site to the log.