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.
