engleski

Analysis of molecular biomarkers in the digestive glands of Unio crassus as a useful tool for assessing pollution of aquatic ecosystems: a study in the Mrežnica River (Croatia).

The Croatian karst river Mrežnica has been in some parts exposed to pollution from various types of anthropogenic activities, especially from industry. Although most industrial plants now provide proper treatment and discharge of wastewater, pollutants previously accumulated in sediments may still pose a threat to aquatic organisms. Molecular biomarkers are considered the most sensitive and earliest response to pollutants. Therefore, it is useful for pollution assessment to obtain information about the harmful effects of pollutants on biota by analysing different biomarkers. As benthic inhabitants and filter- feeding animals, mussels are capable of accumulating large amounts of pollutants and are therefore considered good bioindicator organisms for assessing water pollution. In order to assess water pollution and evaluate possible effects of pollutants on aquatic biota, a set of molecular biomarkers was analysed in the digestive glands of Unio crassus mussels from the Mrežnica River. The set included following biomarkers: metallothioneins (MT) for metal exposure, total glutathione (tGSH) and catalase (CAT) for oxidative capacity and malondialdehyde (MDA) for oxidative damage. In addition, cytosolic concentrations of several essential and non- essential (Ag, Cd, Cu, Pb and Zn) elements were determined. Biomarkers were measured spectrophotometrically, and element concentrations were quantified using a high-resolution inductively coupled plasma mass spectrometer. Mussel samples were collected from two sites at the Mrežnica River: in the industrial zone of the town of Karlovac (contaminated site) and upstream from the town of Duga Resa (reference site). The MDA levels and the activity of CAT were significantly increased in the mussels from the contaminated site, indicating possible overproduction of reactive oxygen species and oxidative stress in these mussels. The elevated levels of these two biomarkers correlated with the increased concentrations of cytosolic Ag, Cu and Pb. Higher tGSH and MTs concentrations at the reference site coincided with higher cytosolic concentrations of Cd, a known inducer of MTs. Cytosolic Zn concentration was similar in mussels from both sites of the Mrežnica River. The presented results suggest differences in biochemical responses of mussels from two sites with different pollutant loads. Therefore, the application of molecular biomarkers is a very useful tool for diagnosing the effects of environmental conditions on organisms.

Biomarkers ; Metals ; Unionidae

nije evidentirano