High precipitation rates characterize biomineralization in the benthic foraminifer Ammonia beccarii

The unique nano- and microstructure of twinned foraminiferal shell calcite

“…In summary, our structural-crystallographic study of P. obliquiloculata shell calcite con rms the state of elevated pH 58,46,40 at foraminiferal calcite biomineralization. The strong twin formation and the strongly prevailing highly irregular crystal morphologies indicate high supersaturation conditions at nucleation and crystal growth, especially, at formation of the bril to platy crystals.…”

“…Nucleation occurs very rapidly and results in the formation of numerous, randomly oriented nuclei 55 . We have indications that P. obliquiloculata calcite is formed at high supersaturation: (i) shell formation is very fast; a new chamber is completed within about 6 hours 36 , (ii) physiological results point to an increase in pH at mineral secretion 45,46,58 , (iii) at foraminiferal shell mineralization calcite precipitation rates are high 40 , (iv) we nd extensive formation of growth twins at and close to the POS (Fig. 11a).…”

“…An increase in intracellular pH from 8 to 9 is reported at foraminiferal shell calci cation 35,45,46,58 . Hence, high pH/high supersaturation conditions lead to fractal-dendritic crystal morphologies (this study), high precipitation rates 40 and fast shell crystallization 36 , while the accompanying competitive growth process ensures that further crystallization becomes regulated. Of the many crystals that nucleate at the start of shell mineralization (due to high pH and high supersaturation), the regulating process of growth competition induces that only few crystals grow to large entities and secures that the c-axis of the large crystals become oriented perpendicular to shell surface.…”

Mesocrystalline Architecture in Hyaline Foraminifer Shells Indicates a Non‐Classical Crystallisation Pathway

“…Hence, the relative volume of alternative phases can be concluded to be small in comparison to the bulk wall material, and may qualitatively not interfere with results from refinements and PDF calculations (i.e., only the spine base remains present in the test wall, see Figure S1 in Supporting Information S1, and additional nanoparticulate phases are not resolved). In addition, element concentrations are highly heterogeneous in the bulk shell material on a micrometer scale (e.g., in bandings in some species, possibly in association with organic material), may differ between chambers, and vary with the ontogenetic stages of the individuals as shown for several species (Branson et al, 2015(Branson et al, , 2016Eggins et al, 2003;Erez, 2003;Fehrenbacher et al, 2017;Geerken et al, 2019Geerken et al, , 2022Khanolkar et al, 2021;Schiebel & Hemleben, 2017;Yoshimura et al, 2017). As heterogeneous element concentrations are likely to cause heterogeneous levels of incorporation of impurities into the foraminifer test calcite lattice, it is possible that different grains experience different concentrations of defects.…”

Characterization of calcite spines of planktonic foraminifers (Globigerinidae)

“…In the benthic foraminifera Ammonia beccarii, the shell thickening rate has been revealed to be ∼0.009 μm min −1 . 24 Bivalve shells, Crassostrea virginica, Mesodesma donacium, and Chione subrugosa, were reported to grow at rates of 0.05-0.09, ∼0.06, and ∼0.08 μm min −1 , respectively. 25,26 The growth rate of reef-building corals varies depending on the species and habitat environment, with a range of 0.008-0.29 μm min −1 .…”