Biomineralization by photosynthetic organisms: Evidence of coevolution of the organisms and their environment?

Abstract

Biomineralization is widespread among photosynthetic organisms in the ocean, in inland waters and on land. The most quantitatively important biogeochemical role of land plants today in biomineralization is silica deposition in vascular plants, especially grasses. Terrestrial plants also increase the rate of weathering, providing the soluble substrates for biomineralization on land and in water bodies, a role that has had global biogeochemical impacts since the Devonian. The dominant photosynthetic biomineralizers in today's ocean are diatoms and radiolarians depositing silica and coccolithophores and foraminifera depositing calcium carbonate. Abiotic precipitation of silica from supersaturated seawater in the Precambrian preceded intracellular silicification dominated by sponges, then radiolarians and finally diatoms, with successive declines in the silicic acid concentration in the surface ocean, resulting in some decreases in the extent of silicification and, probably, increases in the silicic acid affinity of the active influx mechanisms. Calcium and bicarbonate concentrations in the surface ocean have generally been supersaturating with respect to the three common calcium carbonate biominerals through geological time, allowing external calcification as well as calcification in compartments within cells or organisms. The forms of calcium carbonate in biominerals, and presumably the evolution of the organisms that produce them, have been influenced by abiotic variations in calcium and magnesium concentrations in seawater, and calcium carbonate deposition has probably also been influenced by carbon dioxide concentration whose variations are in part biologically determined. Overall, there has been less biological feedback on the availability of substrates for calcification than is the case for silicification.

Environmental controls on coccolithophore calcification

“…Dissolution of the externalised mineral skeleton in seawater undersaturated with respect to the mineral phase does not seem to be a major problem for acantharians (celestite) or diatoms (silica). At least for the diatoms, there is evidence that the organic layer surrounding the silicified frustules can decrease the dissolution rate of silica by 2 orders of magnitude (Natori et al 2006) so that the first-order rate constant for dissolution (d −1 ) falls from a value similar to the maximum specific growth rate (d −1 ) to a value of 0.01× the maximum specific growth rate (Raven & Giordano 2009, Raven 2011a. Milligan et al (2004) showed a small increase in the rate of dissolution of silica from diatom frustules with increasing CO 2 concentration in seawater; the mechanism of this effect is unknown.…”

Biomineralization on the stalk of the eustigmatophyte Pseudocharaciopsis (Eustigmatophyceae)

“…Such mineralization is seen among the bacteria (Heldal andTumyr 1983, Omelon et al 2006). A general review of biomineralization in photosynthetic organisms can be found in Raven and Giordano (2009).…”

Magnesium isotope fractionation during hydrous magnesium carbonate precipitation with and without cyanobacteria

“…Cyanobacteria induced mineralization occurred in both ancient and modern environments (Brady et al, 2009;Planavsky et al, 2009;Raven and Giordano, 2009); cyanobacteria-dominated carbonate formation occurred in oceans, lakes, springs, and soils during the Precambrian (Riding, 2000), whilst modern cyanobacteria-dominated carbonate formation occurs in highly alkaline aquatic environments (Thompson and Ferris, 1990;Braithwaite and Zedef, 1994;Dupraz et al, 2009;Power et al, 2009). Locations where modern cyanobacteria-dominated magnesium carbonate formation occurs include Lake Salda in Turkey, which is fed by ultramafic rock weathering products (e.g.…”