Silica and testate amoebae in a soil under pine–oak forest

Soil testate amoebae are cosmopolitan and abundant protozoa, and accumulate silica for reproduction. Their effect on the terrestrial silica cycle, however, has not been quantitatively determined. We found that testate amoebae consumed 55% of silica absorbed by microbes in the incubation experiment. We estimated amoeban biosilica using our present data and published data. Although biosilica preserved by living testate amoebae was as small as 0.45–1.57 kg SiO2 ha− 1, annual biosilicification in various forest soils was estimated to range from 10 to 227 kg SiO2 ha− 1 yr− 1. We concluded that testate amoebae have a high potential as silica consumers and suppliers, and play a role comparable to that of higher plants in the terrestrial silica cycle.