Wednesday, July 30, 2008

Reef Ecology

The coral reef looks very much like a garden, except flooded with salt water, and very possibly more colourful. (That is if the corals are still alive and not bleached, and you remember to put a red filter when photographing underwater)



The corals form a colossal underwater garden and is the basis of all activities on the reef. It is food, shelter, jail and much more to the animal on the reef (some beautiful, some ugly, some invisible and some imaginary). This post will help the lay person get to know the inhabitants of the reef and appreciate the diversity of life found on the reefs, including fish, jellyfish, turtles,sponges, nudibranchs (our cover girls), crabs, shrimps and so on and so forth. A more technical guide to cover the extremely numerous animal and plant life will be severely voluminous and costly, and if ever it should be published, it will be in hardcopy to earn the authors of this blog some income.

Shall we begin?

Secret ingredient
'The secret ingredient is... there is no secret ingredient'
'Yeah, okay'
'Wait. You believed what I just said?'
'Well, person like you can never keep a secret ingredient a secret, so I'm not surprised'
'No way! I can totally keep secrets okay. The secret ingredient is zooxanthallae, so there!'
'...'
'I so did not say that out loud.'

The secret for success for reef-building corals is the microscopic plant called zooxanthallae living in the tissues of the coral. These plants photosynthesize (don't ask me why. it's a plant thing to like sunlight) and build up organic matter. Zooxanthallae helps corals with calcification, allowing them to grow bigger. The precise reason why zooxanthallae is such an important player is still kept a secret (perhaps my pet rock can help you on this one). Some suggest that the oxygen produced by the photosynthesis is used by the corals for respiration, or that the corals digest bits of the zooxanthallae as a sort of diet supplement. While this sounds rather cannibalistic, let me remind my readers not to grow too emotionally attached to zooxanthallae. They are, after all, plants.

Prisoners



Ah, this one is rather interesting. The crab, Hapalocarcinus marsupialis, (not the one above!) is one very willing prisoner. So willing, in fact, that one does not need to have jail wardens or even a jail cell; this prisoner will build his own, in a manner of speaking. The crab induces abnormal growth of corals (of family Pocilloporidae) to form a tiny cage around itself. Only females do this though, the males wander around on the coral surface wondering why he can't seem to find a date. Certain shrimps also have the same paranoid practice (Paratypton siebenrocki) of locking themselves in, although the males and females prefer to live together (hanky panky!)


Casual associates



Too many to count! Many organisms temporarily make use of corals and have no lasting loyalties. These include protozoans, flatworms and copepods that creep around on the surface of the corals, molluscs and crabs that hide in the nooks and crannies of the reef, and fishes that seek shelter among branched colonies or under coral heads.

Permanant neighbours

Some organisms stay with their coral neighbours for their whole life. Either they've got incredible loyalty, or they've got no choice cause they aren't able to move to a prime estate with waterfront residences. Barnacles make homes on top of coral skeletons, and stay there for the rest of their lives. Blennies inhabit holes in the corals and use it as a vantage point to catch their prey. Sponges (family Cliona) are extremely hostile neighbouts, actively boring their way through the corals foundations by mechanically and chemically scraping through the coral skeleton, making the structure extremely weak. Some molluscs do the same, although we shall not give them their 15 minutes of fame for such bad behaviour. Remember guys, good neighbours day is on 13 November!

Predators



Crown of thorns, parrotfish. Of course, these organisms absolutely love corals! On the menu that is. Enough said.
(The corals on the left of the crown of thorns have been eaten already. Look how white they appear!)

References:
Wood, E. M.. Introduction, In: Corals of the World. 1983, T.F.H Publications,Inc., Ltd. pp 11 - 25
First image by Ms Karenne Tun. Other images by Jacque

Jacque and Theophilus finished work at 2:29 PM

______________________________

the marine junkies
Jacque and Theophilus
18071990 / 28081990
NUS High School
NUS Marine Biology Labs

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thanks
Nudibranchs drawn by Prof. Chou
(hand drawn! wow!)
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