Australia – Coral Cays

This is a short summary as I remember it from Alex the marine biologist on our trip to the Frankland reef of how Cays ( or Keys as they are called in the USA) are formed.

Sediment and coral pieces from the broken coral is washed up into banks and built upon and eroded into coral sand. The structure of coral is calcium carbonate which is alkaline. Rain is very slightly acidic and it causes a chemical reaction on these banks which softens the calcium, darkens it and glues it all together. It looks like rock with fossils embedded in it but actually it’s still the coral. This is quite a quick process being only a few years and from what Alex said was not known about till 15 years ago.

The picture above shows the sand and the solidified brown coral.

The above is showing the broken coral before the solidification process and below both parts of the process with the shapes of the corals still seen in the solidified part.

These banks then have seeds dropped on them by birds or washed up and plants begin to colonise and solidify the land eventually becoming Islands.

There used to be a great trade in calcium carbonate here and the broken coral was shipped out for making cement and other things to the detriment of the reefs. Now nothing can or is removed and as a result the reef here is healthy.

The next photograph is of a protective case of a single celled organism that has a symbiotic relationship with coral, assisting with the absorption of calcium carbonate by coral (I think that’s what I understood). The protective case is star shaped and is as big as a grain of sand, in fact they are part of the sand. I just wonder how someone discovered it!