The influence of pre-treatment, temperature and calcium ions on trace element uptake by an alga (Scenedesmus pannonicus subsp. Berlin) and fungus (Aureobasidium pullulans)

Abstract

Experiments were carried out in order to obtain information on the uptake characteristics of metals in the algal and fungal components of lichens. The uptake of (115)Cd, (65)Zn, (64)Cu, (140)La, (187)W and (76)As in the alga Scenedesmus pannonicus, subsp. Berlin and the fungus Aureobasidium pullulans was determined at pH 7 and 5 respectively, in 4 h experiments varying with respect to temperature and Ca(2+) solution concentrations. Furthermore, the effects of pre-rinsing the cell suspensions on metal uptake were investigated.Pre-rinsing resulted in decreased uptake of W and As by algae and in increased uptake of all elements measured by fungi, which may be attributed to combined effects of starvation and changing densities.For algae, the uptake rates of As, W, Zn and Cd were markedly increased at the highest temperature employed. For Cu and La hardly any effects of temperature were observed, indicating the absence of metabolically controlled uptake. For fungi, but for As no relation of uptake with temperature could be determined.The presence of Ca(2+) ions in the solution applied hardly affected the uptake of As but resulted in increased uptake of W by both the algae and the fungi. The effects of Ca(2+) on the uptake of Cu and La were relatively small, probably due to specific binding sites in the cell walls for Cu and to the 'supercalcium' status of the La-ion.The presence of Ca(2+) caused decreased uptake of Cd(2+) and Zn(2+) by algae, but hardly affected the uptake of Zn(2+) by fungi.The results indicate component-specific uptake and accumulation behaviour in intact lichens.