Simultaneous photoreduction and microbial oxidation of iron in a stream in the New Jersey Pinelands

Photoreduction of ferric to ferrous iron was determined in water held in bottles placed in a New Jersey Pinelands stream, although concentrations of ferrous iron in the stream itself remained below detection (15 ng ml-1). The low ambient levels of ferrous iron apparently resulted from the action of iron-oxidizing microorganisms in water and soil, as shown by a temperature optimum for, and by the inhibitory effect of sterilization upon, the disappearance of ferrous iron. Measurements of 14CO2 incorporation into soil organic matter indicated that the iron-oxidizing microorganisms were not chemolithoautotrophs, but might have been iron-depositing bacteria or chemolithoheterotrophs