SRI LANKA GUARDIAN NATURE
“The builders and architects of the colourful, fascinating and indeed the incredible world of the reefs are mainly millions and millions of tiny anemone-like creatures called polyps. These secrete limestone protective shells that function as their home, and as they multiply and develop further, become the coral formations with which we are familiar.”by Victor Karunairajan
(October 13, Toronto, Sri Lanka Guardian) The oceans of the world beyond the reefs and shelves are vast. Virtually unexplored, these realms have their own unique habitations, which without doubt play decisive roles in the global life-support systems.
The little we have come to know of the deeps through the chance encounters of mariners, deep-sea samples collected by marine biologists and strange catches by fishermen have fired our imagination. As a result, today we are delving more fully into these fascinating regions of life in its many splendoured and bizarre forms.
These depths, from what we already know, are the world of transparent fish with their internal organs visible within their grotesque glass-like bodies, tricolour shrimps with long antennae and several kinds of squids and strange plant-like animals. There are also the gardens of anemones, colonies of spider crabs with their remarkable large legs, heaps of bivalve molluscs and tens of hundreds of other quaint and amazing beings beyond even our wildest imagination.
But it is with life in the reefs that we must become familiar and acquainted to understand the significance of life forms in the deeps better. This appears to have a two-way relationship with the deep ocean life on one side and terrestrial life on the other. The Seychelles Ste Anne Marine National Park, the first of its kind in the world, situated on the world’s largest submerged plateau in the western Indian Ocean, provided an ideal place for such a study.
Tropical reefs are the most biologically active areas in the world. They are indeed natural formations constructed by tiny living animals with hard shell-like skeletons of which corals are the main ones. Hence these are called coral reefs. Apart from the life these coral structures nurture, sustain and support, shorelines are protected from erosion and strengthened by fringing reefs. Certain types of tube worms and calcareous algae also help in the formation of reefs while all kinds of shell forms become constituent parts in reef building.
Generally when corals become established they grow upwards towards the surface. When the extremities of their calcareous structures chip off, the resulting coral debris help to form a new platform with the aid of encrusting organisms that cement them together. On such a platform new corals will grow.
The coral reefs of the Seychelles Plateau, which is a micro-submerged continent by itself, represent a vast and complex marine habitation system. There are probably more living organisms and diverse varieties of different species among the reefs than in any other habitat in the sea or on land. The reefs provide shelter, refuge from enemies from outside and even a chance from predators in the region, protection from tides and currents, and a place to breed. The corals come in many shapes and formations. An excursion to the Ste Anne Marine National Park in a glass-bottom boat or a sub-sea vessel will bring us into some understanding of the complex world of the corals.
Coral is a general term applied to any polyp that produces a skeleton of some sort; a hard, stony skeleton, a horny one of even a mosaic of particles inside the body. Corals are carnivorous, observed Dr Peter Vine in his Life on Coral Reefs in the Seychelles. "They feed on minute organisms in the plankton or tiny crustaceans." The coral polyps have soft, sac-like bodies with one end closed and the other opening at a mouth surrounded by the tentacles bearing the stinging cells.A Reader’s Digest publication, a unique ‘safari’ through the strange world of nature, dwelt on many types of corals both solitary and those that coexist in colonies. Corals begin as a single polyp created by sexual reproduction. It then emerges from the parent’s body as a free-swimming pin-head sized larva and develops a tentacle-fringed mouth leading to a gut and settles on a firm support with its undersurface forming a base that begins to produce the skeleton.
The cycle of development with the solitary coral is complete now and it has only to maintain and reproduce itself. But with the colony types this is only the early stage of development. Known popularly as the reef-builders, the colonial corals multiply by sexual budding. Side polyps grow from the original polyps and these in turn sprout so that a vast structure arises. As the earlier polyps die, the skeletons of the predecessors support the living polyps of the outer layers.
Polyps tend to follow characteristic growth patterns which give corals the varied shapes suggested by their common names such as brain coral, stag horn coral, lettuce coral, fire coral, potato coral and mushroom coral, all of them very much in abundance among the reefs of Seychelles. There are also the whip corals, sea fans, sea pens, sea feathers and the sea pansies.
The species that dominate the Ste Anne Marine Park are the stag horn corals. Known for their commanding and dramatic formation on the reef and extending profusely like an underwater forest, these corals spread out in tree-like forms with numerous pointed branches. Some types of this coral could grow up to two to three metres tall in deeper waters. Its colonial nature affords a protective shield for the smaller fish on the reef. Butterfly fish in particular, popularly known as the beach builder because of its feeding habits on the corals, and several other species including snappers and the angel fish find for themselves a safe haven in the closely packed sharply pointed spires of the stag horn coral colony.
There are also the Moorish idols as well as the surgeon fish. Other reef varieties include the wrasses, damsel fish, parrot fish and file fish. In the Seychelles waters, according to Dr Vine, one can record about two hundred species of fish from a shallow area of reef as small as three thousand square metres. In such a highly complex world of the corals, the opportunities for concealment from predators and for feeding are plenty. Dr Vine observed that the constancy of the environmental factors and a high productivity area have both contributed considerably to the biological success story of the coral reef.
Among the common coral formations, the brain coral, which bears close resemblance to the human brain, is symbolic of the species variety of St Anne Marine National Park. The brain coral grows in isolated heads and could be as small as six centimetres or even giants reaching seven meters across. The elk horn, also called the fan coral, can grow to a height of three metres.
Found usually close to the surface, the elk horn adds much to the beauty of the reef. Without it, observed Robert Staughan author of many books on marine life, the reef would lose much of its magnificence and magnitude for it would be like a rather bare forest. Although all the corals are fascinating in their own way and some grow to gigantic sizes, none of them possess the commanding majesty of the elk horn coral in the submerged world of the reefs.
Mushroom coral or rose coral is in many ways a solitary type. Found in single heads lying loosely on the sea floor, it is said to contain a large single polyp rather than tiny ones in colonies, as is the case with most corals. The mushroom coral is also the favourite food of the butterfly fish.
Soft corals are characteristic features in these waters. The bright orange or red horny types in their natural state are some of the most beautiful formations of the reef habitations. There are the organ pipe coral, which is not easily recognized, and also the stony corals that come in hundreds of shapes and colours.
All these make coral reefs remarkable regions for engaging research and study. In his study, Dr Vine has corrected a misconception that it is the calcium carbonate skeleton in some strange ways constituted the living animal. The skeleton, he said, is produced by fleshy living polyps each one similar to a tiny sea anemone. The leafy fire coral that grows to heights of three metres in large patches usually in shallow waters along the outer reefs is easily recognized. A brush against it will make one gasp with pain. Gloves are important when studying corals in their natural surroundings more so with species like the fire coral. Among the many lesser species of corals found in the marine park, one is the beautifully formed lettuce coral, usually found beside brain corals. Another much sought after by collectors is the star coral, a small species found in little pockets of the reef.
The Ste Anne Marine National Park bordered by several granitic islands is an open-air aquarium with its own natural setting. These granitic islands along with others standing on a platform type plateau have given to this region of Seychelles the characteristics of a lagoon. Some scientists have expressed the view that there is evidence to indicate that twice during the last 100,000 years the Seychelles Plateau may have sunk and risen up again. They believe that the reefs of this area have experienced at least two or even three successful periods of flourishing growth alternating with decades of deterioration, such occurrences corresponding with oscillations of the sea level.
Soviet scientists who did extensive research in these waters from the research vessel of the USSR Academy of Sciences, RV Akademik Alexandr Vinogradov, said all indications were that the reefs of the Seychelles Plateau were possibly the remnants of the flourishing reef biota of an early Holocene Epoch. This period marked the extinction of the giant mammals. The present state of the reef, according to them, was possibly caused by some environmental disturbances. However, they added, that there was evidence of significantly higher phyto-plankton content and dissolved chlorophyll in the waters of the Seychelles Plateau and this they noted was about ten times higher than in the well-developed Pacific and Atlantic reefs. It is this vital factor in the food chain that makes this region biologically rich and promising.
The corals of this region are indeed great attractions to underwater enthusiasts. The relief and the structures of this briny Neptunian world has exciting features including caves, huge stones and rocky outcrops covered with coral growth like underworld fairyland. The marine world of this submerged platform and the terrestrial life on the peaks of the plateau though different in many ways certainly has a symbiotic relationship and to this there must be many dimensions. We humans have so much to learn yet to fully understand the intrinsic network of interdependency of all living organisms. This is essential for our very survival. - Sri Lanka Guardian
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