Simultaneous photoreduction and microbial oxidation of iron in a stream in the New Jersey Pinelands1

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.