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CEN­TRED ON CO­RAL

Scuba Diver Australasia - - Contents - In­for­ma­tion cour­tesy of the Co­ral Tri­an­gle Cen­tre

HARD CORALS

• Grow into co­ral reefs

• Live within an ex­oskele­ton cup (or ca­lyx), pro­duced as the co­ral se­cretes cal­cium car­bon­ate to stick to the ground and also to its polyp friends in its colony.

• Polyps are in­ter­con­nected via a sys­tem of gas­trovas­cu­lar canals that al­low them to share nu­tri­ents and zoox­an­thel­lae. These canals run through a very thin tis­sue on the sur­face of the co­ral

colony. These tis­sues can be eas­ily dam­aged.

CORALS ARE VI­TAL!

• Co­ral reefs pro­vide goods and ser­vices worth an

estimated SGD375 bil­lion each year.

• Co­ral reefs pro­tect shore­lines from wave ac­tion and pre­vent ero­sion, prop­erty dam­age and loss of life. Reefs also pro­tect the highly pro­duc­tive wet­lands along the coast, as well as ports and har­bours and the economies they sup­port.

• Glob­ally, half a bil­lion peo­ple are estimated to live within 100 kilo­me­tres of a co­ral reef and ben­e­fit from its pro­duc­tion and pro­tec­tion.

SOFT CORALS

• Do not pro­duce a rigid cal­cium car­bon­ate skele­ton and do not form reefs, though they may be present

in a reef ecosys­tem.

• Can of­ten ap­pear to look like plants, as they bend and sway in the

sea cur­rents.

• Are also very sen­si­tive to touch and

eas­ily dam­aged by care­less divers

1 Co­ral is an an­i­mal. They eat plank­ton and other small mi­crobes, catch­ing them with their ten­ta­cles.

2 In­di­vid­ual co­ral polyps grow and live to­gether to form colonies.

3 Co­ral polyps have a sym­bi­otic re­la­tion­ship with an al­gae called zoox­an­thel­lae. The co­ral pro­vides a home for the zoox­an­thel­lae. The polyps breathe in oxy­gen and breathe out car­bon diox­ide and wa­ter, which the zoox­an­thel­lae pho­to­syn­the­sise, pro­duc­ing nu­tri­ents that, in turn, the co­ral polyps use as food.

4 Growth rates vary be­tween species, but is gen­er­ally be­tween 0.3 to 2 cen­time­tres per year for “mas­sive” corals, and up to 10 cen­time­tres per year for “branch­ing” corals.

5 It can take up to 10,000 years for a co­ral reef to de­velop. De­pend­ing on their size, bar­rier reefs and atolls can take from 100,000 to 30,000,000 years to fully form.

6 Co­ral reefs sup­port more species per unit area than any other ma­rine en­vi­ron­ment.

7 Sci­en­tists es­ti­mate that there may be an­other 1 to 8 mil­lion undis­cov­ered species of or­gan­isms liv­ing in and around reefs.

8 Corals are most pro­duc­tive at less than 27 me­tres deep, but some deep-wa­ter species have been found at around 2,000 me­tres.

9 Co­ral reefs cover less than 1% of the sur­face of the planet.

Touch­ing a hard co­ral can stop the polyps be­ing able to com­mu­ni­cate and share nu­tri­ents.

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