Crustaceans as biological indicators of heavy metal pollution in Lake Balaton (Hungary)

Abstract

Trace metals (Cd, Cu, Pb, Zn) were measured in mixed zooplankton samples collected from the open water of Lake Balaton (Hungary) in order to assess spatial and seasonal changes in the heavy metal load of different sites, during 1996–2000.Samplings were performed usually twice a year in different seasons (spring, summer and autumn). The heavy metal concentrations of zooplankton biomass were determined by atomic absorption spectrophotometry. Additionally, for some of the sampling sites – Western- and Eastern basins – the correlations between the heavy metal load of Crustaceans and the element concentrations of the water recorded monthly by the Transdanubian Environmental Protection Agency were also analyzed.The average metal concentrations in zooplankton varied in the following ranges: Cd: 0.25 – 3.91; Cu: 5.9 – 26.4; Pb: 1.59 – 12.84; Zn: 37.6 – 180.5 mg kg⁻¹ dry weight. Significant spatial and seasonal variations with occasionally outstanding differences in the heavy metal load of samples could be observed during the investigated period. The heavy metal load of the Crustacea plankton biomass in summer and autumn proved to be usually higher than in spring. During the investigated period an overall significant increase in the cadmium, copper and lead load of the Crustacea plankton populating the lake could be observed. Pearson correlation analysis performed between the heavy metal concentration of Crustacea plankton biomass and that of the water in the two outlying basins of the lake revealed strong relationship for Cd, Cu and Zn, while for lead the correlation proved to be not significant.