Calcification in Cyanobacteria

Abstract

Calcification in cyanobacteria depends on water chemistry as well as on physiological and morphological factors such as photosynthetic bicarbonate uptake and the existence of a suitable sheath. Physicochemical precipitation under high levels of supersaturation leads to the dense encrustation of the filaments, forming a solid micrite tube, while photosynthetic bicarbonate uptake in less supersaturated waters can lead to micrite precipitation within the sheath. Both forms of calcification are restricted to species which prefer oligotrophic, phosphate-poor environments. In this way, various environmental factors such as the saturation state of the water with respect to calcium carbonate minerals and the concentration of dissolved CO2 and phosphate may be reflected in the occurrence of fossil calcifying cyanobacteria.