[Coral-List] New conceptual model of coral biomineralisation

Scott Wooldridge S.Wooldridge at aims.gov.au
Tue Sep 18 05:48:10 EDT 2012

“There has never been any doubt that corals write valuable information into their skeletons; it’s their language that has remained blurry and ambiguous” (Barnes and Lough, Global Change Biol., 1996). Indeed, whilst it has been understood since the 19th century that coral skeletons are built of aragonite crystals with taxonomy-linked ultrastructure, the way by which corals control this crystallization process remains an unsolved question. In a new essay in Biogeoscience Discussions, I outline a new conceptual model to explain coral biomineralisation, wherein the morphological attribute of skeletal extension is linked to the physiological requirements of the coral host to ensure its metabolic status during periods of O2‐limitation; which is exacerbated by the respiratory oxygen demands of the coral’s algal symbionts (= zooxanthellae).. The model thus provides a new narrative to explain the high growth rate of symbiotic corals, by equating skeletal deposition with the ‘work‐rate’ of the coral host needed to maintain a stable and beneficial symbiosis. In this way, coral skeletons are interpreted as a continuous (long‐run) recording unit of the stability and functioning of the coral‐algae endosymbiosis. After providing supportive evidence for the model across multiple scales of observation, I use coral core data from the Great Barrier Reef (Australia) to highlight the disturbed nature of the symbiosis in recent decades, but suggest that its onset is consistent with a trajectory that has been followed since at least the start of the 1900’s. In concluding, I explain how the evolved capacity of the cnidarians (which now includes modern reef corals) to overcome the metabolic limitation of hypoxia via skeletogenesis, may underpin the sudden appearance in the fossil record of calcified skeletons at the Precambrian‐Cambrian transition ‐ and the ensuing rapid appearance of most major animal phyla.

The article, “A new conceptual model of coral biomineralisation: Hypoxia as the physiological driver of skeletal extension” is now accessible and open for Interactive Public Discussion until 13 Nov 2012 at: http://www.biogeosciences-discuss.net/9/12627/2012/

Scott Wooldridge

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