Precipitation of Calcium Carbonate Mineral Induced by Viral Lysis of Cyanobacteria

Viruses have been acknowledged as important components of the marine system for the past two decades, but the understanding of their role in the functioning of the geochemical cycle remains poor. Viral induced rupturing of cyanobacteria are theoretically capable of releasing intracellular bicarbonate and inducing the homogeneous nucleation of calcium carbonate, but experimental-based support for viral induced calcification is lacking. In this laboratory study, both water carbonate chemistry and precipitates were monitored during the cyanophage infection and lysis of host cells. Our results show that viral lysis of cyanobacteria can influence the carbonate equilibrium system remarkably and promotes the nucleation and stabilization of carbonate minerals. Amorphous calcium carbonate (ACC) and aragonite were evident in the lysate compared to the brucite precipitate in non-infection cultures implying that a different precipitation process had occurred. Based on the carbonate chemistry change and microstructure of the precipitation, the viral induced calcification may initiate by rapid intracellular calcification because of the unfettered intracellular access of Ca2+ and react with cytoplasmic alkalinity after the virus attacks and breaks down the cell wall. The experimental results raised here first demonstrate the pathway and result regarding how viruses influence the mineralization of carbonate minerals. Furthermore, our results also imply that viruses play a crucial role in seawater carbonate chemistry and may balance the geochemical element budget within the earth system.

Weathering of granodiorite and micaschists, and soil pollution at Mt. Mottarone (northern Italy)

At the top of Mt. Mottarone a thin level of micaschist, covered by soil, rests on granodioritic rocks. Both rock types underwent weathering with generation of new minerals and variation of the original chemical composition. The weathering produced phyllosilicates and Fe- and Al-hydroxides. Mass balance calculations on the basis of Zr immobility indicate that at least As, Bi, Cd, Mo and Sb were added to the micaschist, whereas the other elements were removed; the soil was also enriched in As, Bi, Cd, Mo and Sb during weathering. Dry and wet pollution was responsible for the addition of the elements listed above. On the other hand, Ca, Na, Mo and Sr were surely removed from the granodiorite during weathering, whereas Bi and Cu were added by percolation from the overlying micaschist. The chemical features of a spring issuing from granodiorite agree well with the element budget as deduced from the rock transformation. This is not the case, however, for a spring issuing from the micaschist.