Abstract
Three Ge species, inorganic germanium (Ge (sub i) ), monomethylgermanium (MMGe) and dimethylgermanium (DMGe) have been identified in natural waters. Ge (sub i) in solution varies as a coherent pair with Si, reflecting uptake into and release from the tests of siliceous organisms. MMGe and DMGe display conservative (non-reactive) behaviour in estuaries and oceans, varying only with salinity. This conservative behaviour implies that methylgermanium species are not incorporated into the Si biogeochemical cycle. The residence time of methyl-Ge in the ocean is estimated to be on the order of a few m.y. Production of MMGe, DMGe and trimethylgermanium (TMGe) in an anaerobic sewage digester, suggests that methyl-Ge in the environment may be produced by microbial biomethylation of Ge (sub i) during methanogenesis. Algal cultures grown in Ge (sub i) -enriched media were not observed to produce methylgermanium, nor was Ge (sub i) methylated by reaction with methylcobalamin, a methylated vitamin B (sub 12) derivative. [Authors' abstract]