Influence of low cadmium and zinc concentrations on batch culture Prorocentrum micans (Dinophyta) containing low levels of dissolved organic carbon

Abstract

Experiments with Prorocentrum micans Ehrenberg were run over a period of 380 h in North Sea water containing 0.5 mg C 1-' of dissolved organic carbon. Dissolved Cd concentrations ranged from 0.08 to 10 pg l-'; Zn concentration was 0.1 pg 1-'. Cell density started with 35 000 1-'. Growth in terms of cell numbers, primary productivity, bacterial activity, and uptake of Zn and Cd-measured by the radlo isotopes 6 5 ~ n and ' OgCd-were followed in short intervals during exponential and stationary growth phases. Enrichment factors of the metals were highest at the lowest Cd concentration. On a daily basis, Cd and Zn concentrations increased during the day and decreased at night. The rhythm was most obvious during exponential growth. This indicates the special role of actively metabolising cells for uptake of Zn and Cd. Accumulation was more rapid for Zn (maxima every 24 h) than for Cd (maxima every 26 h), so that the daily rhythm of the metals was shifted.