Rhodoliths

The stone plant spent 1000 years

Turning CO2 to stone

And welcomed many homeless friends

Into its roomy home

And rolling sliding side by side

They cross the ocean floor

A million limy popcorns

Soon joined by millions more

Some will find a resting place

Upon a limy beach

While others sink into the ooze

Forever out of reach

If you have ever walked along a beach on Spencers Gulf the chances are that you would have found a rhodolith. The whole gravelly beach may in fact have been composed exclusively of rhodoliths. These are the limy popcorn shaped “corals” that we are all familiar with but they are not corals. You won’t see any sign of a polyp no matter how hard you look. The nodules are beautifully smooth and each one is an exquisite work of art. And each one is a limy skeleton of a red calcareous algae laid down over centuries in its popcorn bed on the floor of Spencer Gulf. The living ones look like the dead ones except for their pink colour. The rhodoliths are incredibly important for the world carbon balance as they turn carbon dioxide into limestone which in turn becomes a home for the plants and animals of the gulf. It’s a marvellous system but the rhodoliths have one big disadvantage. They roll around the sea floor but they can’t actively move. So when a trawler comes along to harvest the animals living on the limy bottom they often as not end up burying the rhodoliths in the ooze. So the stony plant that has for centuries used sunlight to convert CO2 to stone finally finds a grave deep in the mud where it is cut off from the life bringing sun-light. Vast areas of rhodoliths have already been destroyed by trawling in Spencer Gulf and it’s important that the remaining beds are protected. It’s important for the carbon balance, the food chain and ultimately the whole structure of the gulf. Where would we be without these engineers of the ocean? They may be small but there are lots of them and they do their work over millennia.