Spatiotemporal trends of heavy metal concentrations in fish of the River Morava (Danube basin)

Abstract

The aim of this study was to assess mercury (Hg), cadmium (Cd) and lead (Pb) contamination in muscle tissue of fishes over the longitudinal profile of the River Morava (Czech Republic, Danube basin) and to detect any temporal trends over the past 18 years. Fish samples were collected in 1992, 1998, 2000, 2003 and 2009 at 6 study sites situated just downstream of important pollution sources. Chub (Leuciscus cephalus L.) were selected as indicator species at 5 sites, and brown trout (Salmo trutta m. fario L.) at the uppermost site where chub do not occur. In total, muscle tissue of 175 specimens of chub and 19 specimens of brown trout were analysed. Concentrations of heavy metals ranged as follows: mercury 0.015–0.369 mg/kg; cadmium 0.001–0.254 mg/kg and lead 0.006–1.505 mg/kg. Mercury levels did not exceed the maximum allowed concentration in the Czech Republic (0.5 mg/kg). Content of cadmium and lead in fish muscle exceeded the maximum allowed levels (0.05 and 0.3 mg/kg respectively) in 11 and 4 samples, respectively. On average, the order of metal concentration in fish muscle was: Hg>Pb>Cd. No significant differences were found between sites along the longitudinal profile of the river. Significant differences were found, however, for the interannual comparison of cadmium and lead (but not mercury) at different sites (P < 0.05). A catastrophic flood in 1997 resulted in an increase in metal concentrations, especially cadmium and lead, in the following 1998 season. Our results indicate that the Morava river basin does not represent a threatening source of mercury, cadmium or lead for the River Danube downstream.

Keywords:

• Mercury
• cadmium
• lead
• contamination
• River Morava
• fish muscle
• Leuciscus cephalus
• Salmo trutta m. fario

Acknowledgments

This study was supported by Centre of Excellence grant no. LC522 and the research project VaV SP/207/73/08 “Identification of anthropogenic pressures on the quantitative state of water and water ecosystems in the Morava and Dyje river basin district.” The authors are grateful to the officials and managers of the Czech Anglers Union and Moravian Anglers Union for allowing us to sample fish. We would like to thank all the people who helped in the field and Dr. Kevin Roche for manuscript improvement and English correction.