A warm tropical breeze wafts unwitnessed, across the surface of the Sulawesi Sea as the cloudless spring day pales into twilight. Above, the relative intensity of the full moon increases in proportion to the fading sunlight while half a kilometre out from Derawan Island, the gentle waves barely reach five centimetres from crest to trough. It is a magical enough evening above the waves but what is happening just beneath is truly miraculous.
Coral does not care whether an ocean or island is named. Coral does not understand such things. Coral knows nothing of the world above the waves. Neither is coral even remotely concerned if any human eye ever witnesses its incredible natural beauty. But coral is concerned with the full moon and when the sun is setting. Coral is also sensitive to temperature changes in the water and is somehow aware of the changing tide. These things are important to the ocean dwelling, polyp shaped, calcium secreting, asexual, plankton eating, invertebrate animals that we have come to know as coral… that we have named coral.
Even if someone were there… to appreciate the full moon sunset, on a surface water craft of some kind, they would not have the slightest inclination of the most extraordinary and precisely timed event taking place in the liquid darkness below them. One would have to be in the water, with mask and perhaps even a water-proof light, to notice the cloudy expulsion into the water, that would indicate spontaneous spawning had just occurred. Somehow, through the miracle of evolution, coral has learned that successful propagation depends on triggering a synchronized release of sperm and eggs according to a few distinct temporal cues. Recognizing the full moon and being aware of the setting sun are two of these very important time based prompts.
Not all coral reproduces through spontaneous asexual spawning to form larvae however. These creatures have persisted through the aeons by a variety of measures and means, including a few different methods of self-cloning.
For many… for myself… there is little that better epitomizes the incredible beauty and variety within nature than a brilliantly coloured coral reef. It is not so surprising that this extraordinary otherworldly beauty is alive, and that it is as fragile as it is tenacious. The magical beauty of a coral reef defies meaningful description. It is one of those things that must be experienced first hand to be truly appreciated.
I remember one magical night, scuba diving off the east coast of Borneo in the early nineties. The colours and shapes of the coral and fish within the illuminated cone of my headlamp were as vivid and effulgent as anything I might have conjured up in my untethered imagination. The inky blackness was in sharp contrast to the truly remarkable scene in front of me. It appeared entirely too strange… the colours and shapes too unfamiliar and remarkable to believe that it wasn’t some form of fabricated reality. Yet I fully understood that what I was seeing was in fact real.
Richard Feynman once said that anyone can appreciate a rose, but a scientist can appreciate it on an entirely different level. To understand the atomic structure and biology of a coral reef is very obviously not required to appreciate the unique and preposterously inordinate beauty. But it does provide a fascinating insight into the structure and source of its beauty.
There are at least two thousand and five hundred species of coral. Corals are in fact animals, though one might think that a coral reef is a collection of plant like life-forms. Their physical appearance is certainly more like some kind of exotic plant than it is to any animal, warm or cold blooded, either marine based or of the land. But that assumption would be blatantly wrong. Corals being invertebrates, have no skeletal structure. They have no spine. This fact might be partly responsible for a general false assumption of coral being plant based.
Corals are polyps. This is a term that describes a shape, a tubular shape, elongated to varying degrees depending on the species. Some coral polyps are barely a few millimetres in diameter while some are over 10 centimetres across. Corals are also sessile, which means they are firmly attached to something and are immobile. It is not surprising that sessile polyps are mistakenly considered to some form of ocean flora.
Despite the brilliance and range of colour across the various species, coral are not inherently very colourful at all. The intense radiant richness of reds, greens, yellows and blues are characteristic of the potpourri of various forms of algae who enjoy a symbiotic relationship within the coral.
But, as ocean temperatures rise, the coral is no longer able to provide sufficient carbon dioxide and ammonium to the algae to maintain its responsibility of the reciprocal mutually beneficial arrangement. The colourful algae is expelled in a valiant short term struggle for survival. The resultant white coral is not immediately dead but if adverse conditions persist, and the algae is unable to return to re-initialize photosynthesis, the coral polyps will eventually starve and perish.
Life on Earth may not be entirely dependent on the existence of coral polyps, but it is very much enhanced as a result. Life in general is at least partially dependant on the ecosystem surrounding coral and coral reefs. Critical symbiotic relationships exist between the coral and fish, anemones or ocean flora and by extension from there, to life on land. The world is a more diverse, colourful, amazing place as a direct consequence of this truly incredible creature.
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Michael, your blog is truly amazing!!!😘 I have been following Ocean Mysteries With Jeff Corwin and recently in season#3 episode #11 we witnessed the wonder of coral spawning. I am so impressed with your knowledge of the many, many corals that are thriving. Yet sadly enough (as you wrote ) some coral are struggling for survival …mama 😍❤️very impressed!!!