Phytoplankton cell size and the development of microenvironments

The effect of cell size on the development of extracellular microenvironments of pH produced by individual photosynthesizing phytoplankton cells was investigated. The presence of pH microenvironments was determined by detection of a chemical reaction known to occur in microenvironments of high pH produced by algal photosynthesis, specifically the extracellular oxidation of Mn(II) to MnOx. The dye leukoberbelin blue was used to detect the reaction. It was experimentally determined that individual algal cells larger than 20 μm (length and/or width) produced microenvironments, while smaller cells did not unless present as cell aggregates larger than 20 μm. A mathematical model is presented and discussed.