The applicability of Cladophora glomerata (L.) Kütz in an active bio-monitoring technique to monitor heavy metals in the river Danube

Abstract

Within the scope of active bio-Monitoring of heavy metals in the river Danube the bioaccumulative capability of Cladophora glomerata was used. Instead of a natural substrate in the littoral zone of the river, a floating artificial substrate was used to eliminate the majority of changes caused by the water regime. The dimensions and the structure of this substrate were designed to suit the requirements of the colonization of C. glomerata and that of the quantitative sampling of plant material for the subsequent heavy metal analysis. The heavy metal concentration in C. glomerata significantly differs according to its developmental stages and spatial (vertical) position. Both of them strongly depend on and correlated with the changes in the dry weight of the Cladophora itself. According to our field experiments in the continuously growing Cladophora web this ‘weight dilution’ effect can be considered one of the most significant factors which influences the heavy metal concentration directly. Through the changes in dry weight other physical-chemical parameters (flood effect, light condition, temperature, conductivity and redox potential) seem to be the most important factors influencing indirectly the heavy metal uptake and accumulation.