with respect to calcite at all times, there was a diurnal pattern Calcium and pH ion-selective microelectrodes are used for the to calcite precipitation. They proposed that the diurnal patfirst time to measure chemical activity profiles above laboratorytern may be linked with local variations in the solution comgrown algal biofilms (green alga, Chlorococcum sp). The results position close to algal surfaces. They also noted that the are used to calculate the solution composition changes above an presence of biota induced nine times more mineral precipitaactively photosynthesizing biofilm. These changes include the total tion compared with precipitation in abiotic conditions.
calcium concentration, degree of supersaturation of the solution
Calcite precipitation has important ecological effects bewith respect to calcite, and the partial pressure of carbon dioxide.
cause it can induce the coprecipitation of inorganic phos-Measurements are made in a flow-cell, which was designed to hold phate, often described as a ''self-cleaning'' mechanism bethe templates on which the biofilms are grown. Measurements show pronounced gradients of pH and calcium concentration, cause it removes biologically available phosphorus, thus within a distance of approximately 500 mm above the biofilm. The controlling eutrophication. Phosphate coprecipitation in high degree of supersaturation caused by the low concentrations lakes has been widely studied (5-10), the self-cleaning of carbon dioxide near the biofilm surface leads to the precipitation mechanism is thought to operate both directly through the of calcite on the biofilm. SEM micrographs illustrate the close coprecipitation of inorganic phosphorus with calcite, and association of calcite crystals with the algal cells. Preliminary reindirectly by the association of nucleated minerals with algal sults are presented of the precipitation rates estimated from the cells, causing their flocculation and deposition to the bottom diffusion flux of calcium at the biofilm surface. The results are in sediments.
broad agreement with the rates expected from calcite seed growth Biofilms are highly complex structures, heterogenous in experiments in similar solution conditions.