Behavior of Organically-bound Iron in Lake Ohnuma

Abstract

Water samples were taken from Lake Ohnuma and a river which flows into it. Concentrations of organically-bound iron and nitrate in both the lake and the river were measured throughout one year. The iron complex in the river water is a dissolved small molecular size species and diffuses into the lake without physical deposition. The iron complex in the lake shows a lower concentration during the period from spring to autumn than in the river because of utilization by phytoplankton. In winter the iron complex concentration became equal to that in the river. Throughout one year the iron complex showed the same behavior as nitrate. The iron complex increased the growth rate of phytoplankton in a culture experiment and passed through a semipermeable membrane with a pore size of 24 A. The iron complex was assumed to be fulvic acid-Fe. © 1982, The Japanese Society of Limnology. All rights reserved.