hibis Islands and Lagoons French Pacific

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     Corals 1b

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Corals builders of reefs (madreporia) live in a very pure, salted, well oxygenated, not too deep water (generally small tides: to 2 meters) whose both temperature and saltiness vary little (18 with 29°, 24° is optimum). These requirements limit them between the parallels 30° (northern and southern), but not regularly because of cold streams and lower temperature of waters (see picture); they have grown mainly around the extinct volcanoes. They need non turbid water either, without sediments, and light too.        World location map

In the Mediterranean sea, the " red coral ", individualistic, lives basically by 40 to 100 meters, but one found corals up to 3500 meters. The " black coral " also lives with great depth.  Be cautious while bargaining a piece of famous black coral (also in the Caribbean islands) for it could be a rather good plastic imitation. At least, on the sea or in the street,  don't pay too much.

 Madreporia live in symbiosis (common interests), with a microscopic alga, distributed in their body and numbering several million for only one individual; madreporia live close to the surface of the water because these algae, unicellular, are true plants which live only with a strong light (photosynthesis).  They are involved in the coral loss of colour, when they are ill but if the coral is badly affected, it is not dead yet despite its poor looking ; one can check it with the good quality if the lime.

Fluorescence of the coral. Certain species living in the depth dark react to the ultra violet light  (light known as “black light”), adorning themselves with gorgeous .. fluorescent colours. It is not a mere extravagance of the nature, but well a manner of pointing out itself in weak lighting, by naturally emitting an ultra violet light. It was indeed noted that fish, (and may be some other organizations), perceive the light ultra violet and could be attracted.. but at their own risk. One do not know much about this complex world.

The barrier reef testify of the real size the island had at the beginning ; so, New Caledonia was twice or triple !

The lagoon spreads between the island and the circle of the barrier built by corals, which generally live in a few meters deep, but also by calcarous algae and a few by spoons.

The thickness of this circle can reach several hundreds of metres.  It is broken into chunks and crumbles under the power of tempests and uricanes.

The reef circle a lagoon whose part no facing the wind is larger than the other (say under the wind (sheltered). On the sheltered coast (the wind have to cross the island), slopes are attenuated but the sea receive less oxygen.

Reef of  New Caledonia (West coast, protected from the wind)

With its 1600 km length, its 350 varieties of corals and 2700 fish species, it is the richest behind the Great Australian Barrier ((500 varieties of corals).

 

Grouped in continuous compact colonies or isolated in "patates" (potatoes), they form fringing or reefs barrier and atols.

The Corals builders always do not form a lagoon: indeed, the reefs known as " fringing " are established in edge of the shore or next to. Fringing reefs and barriers most often exit together. The reality is that at the beginning, reefs are all along the edge of the coast, in a shallow water ; with the time, the island sinking slowly, corals try to survive and built on the deads ones to gain gradually a few centimeters (example 3 cm a year).

Inside an atoll pushed up, or quite closed, the life nearly doesn't exist  (water too salty, too warm). The life is close to the récif or sea side.

Open your eyes...for the life story unfold itself under your feet.



Branche de corail photographié en bordure de l'hôtel, à Bora Bora , mais j'en ai vu à l'Anse Vata (Nouméa), où se baigne la population !

At the edge of the shore, in less than one meter of water deep , a little society has been founded : one branch of coral, two blue fishes and a starfish. Sometimes a sea urchin with its long needles.

Open your eyes.. All interesting things are not only displayeded in museums or showed in books ; there are vestiges and fossils everywhere ; flints testify sometimes : very widespread, they would be agglomerates of sponge skeletons, perhaps going back at more than 70 million years.

One finds on them prints of shells, gorgones and corals, but it is necessary to be patient (a low sun is more favorable); with chance, one can find beautiful parts (see "hibis, decoration").

Open your eyes...  There are sea anemones on our Atlantic coasts, inside small ponds of sea water left during the low tide. Black or light-green anemones of about one tenth cm.  My own picture in Brittany. Not so great than tropical ones but it's emotional finding some.

Inside little bunches of fishing thread and algae let at the low tide ont the shore or the beach sand, we found several times these coral branches  

Branches are the first skeleton. The second skeleton is of lime. One can distinguish individual calcareous concretions with their hole that contained a polyp.

 Our beloved dinosaurs would have been living between -160 and - 60 millions years i.e Jurassic and cretacéous perod.They have thus desappear at the end of the cretaceous.

The height of the seas and oceans varies during time, fluctuating between ice periods and inter-ice periods, but there are lots of short variations between them !). so climates evolve. Some stacks to think at the both ecologists and infortunately, scientists statetements wo foresee the future with the ozon hole : At - 600.000 years, the level of seas was the same as now. See "some more, top page" for variations of ice quantity and sea levels.

Rather numerous mountains are marine deposits (limestones) raised, and even coral reefs, like the Dolomites (Italy), canyons in Madagascar and so on..
TENTACLES
 Each tentacle has several tiny pouches or bags containing a urticant liquid ; a small harpoon attached to a filament bathes in this urticant liquid. A lid closes the whole; if a prey approaches to closely and touch a cilia the lid opens and the harpoon is projected.

When one put the hand on the coral, one have the impression to get a viscous liquid on the hand and that start itching. Without any wound (cut, scratch), it won't develop any harm (see " risks and dangers..).

All are urticants : they release a paralysing liquid on their prey.

It is sensible to avoid touching the corals. Tahitians  rub a lemon on them but I don't know about the effectiveness of this process.

Coral bamboo in the Atlantic ocean, down to 1000 to 1500 metres deep. Grows in 4 degrees waters, amid strong streams. A piece got back by a fishing boat. Océarium of Le Croisic. Incredible  black Spiral Coral   with height long, long spiral stems (one can see a diver at the bottom). La Réunion. Softcorail (photo CNRS)

  Coral 2 (threats, madreporia of New Caledonia, anemones, tentacles, reproduction)

Coral 1 (origin, sea depth, madreporia, corals and madreporia, tentacles..) Coral 2 (threats, madreporia of New Caledonia, anemones, tentacles, reproduction) Coral 3 (dead reefs, red coral, black -harvest- yellow coral, gold, pink, jewellery, chirurgic, research) - Document (nautili, fish, fishing, dugouts, sea snake, reefs and passes..) Shells 1 (NewCal basic collection) Shells  2 (extraordinary collection and geisha of shells)Sharks (physical distinction - peal, jaws, senses - attacks, extermination)  - summary hibis Islands and lagoons here-after 

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