Distribution of magnesium in coral skeleton

Abstract

Ion micro‐probe imaging of the aragonite skeleton of Pavona clavus, a massive reef‐building coral, shows that magnesium and strontium are distributed very differently. In contrast to strontium, the distribution of magnesium is strongly correlated with the fine‐scale structure of the skeleton and corresponds to the layered organization of aragonite fibers surrounding the centers of calcification, which have up to ten times higher magnesium concentration. This indicates a strong biological control over the magnesium composition of all structural components within the skeleton. Magnesium may be used by the coral to actively control the growth of the different skeletal crystal components.

Past daily light cycle recorded in the strontium/calcium ratios of giant clam shells

“…S5d). Spike-type enrichment of Mg observed previously in coral skeletons 26,27 resembles the observations described in this work. The irregular spikes possibly indicate the importance of other as-yet-unidentified controls, including biological controls, on Mg/Ca.…”

Evaluation of annual resolution coral geochemical records as climate proxies in the Great Barrier Reef of Australia

“…The relatively fast-growing 10AR2 has a lower mean value of Mg/Ca than the slow-growing 10AR1, which is also contrary to previous studies of Porites corals that were based on bulk samples from different colonies (Inoue et al 2007), and suggests that the Mg/Ca offset may also be caused by biological/metabolic differences between the two colonies (Quinn and Sampson 2002;Fallon et al 2003;Mitsuguchi et al 2003;Meibom et al 2004) and/or the loss of Mg during chemical treatment of the coral skeleton (Mitsuguchi et al 2001;Watanabe et al 2001a). The two corals were treated using the same chemical protocols, but they may have different Mg distributions induced by the differing biological controls on each of them.…”

“…As the factors controlling Mg/Ca and d 13 C in corals remain to be fully quantified (McConnaughey 1989;Swart et al 1996;McConnaughey et al 1997;McConnaughey 2003;Mitsuguchi et al 2003;Meibom et al 2004), their climatic significance will not be discussed here. Instead, we focus on the annual resolution Sr/Ca, d 18 O, and Dd 18 O series as their climatic and environmental significance is more straightforward.…”

Transformation mechanism of amorphous calcium carbonate into calcite in the sea urchin larval spicule

“…This process was first observed in the teeth of chitons where a disordered ferrihydrite precursor transforms into magnetite (2). It has also been observed in different invertebrate phyla (3)(4)(5)(6)(7)(8). Amorphous calcium phosphate was recently identified in the newly deposited fin bones of zebrafish (9).…”