engleski

Multibiomarker approach on the gills of brown trout (Salmo trutta) as a tool for the assessment of the Krka River metal pollution

The Krka River is a karst Croatian watercourse, which is considered as one of the most beautiful pristine environments in the region. However, recently, an increase in the concentrations of several trace elements was observed downstream of Knin town, as a consequence of direct discharge of untreated municipal and industrial wastewaters into the river 1, 2. A part of the Krka River, starting 2 km downstream of Knin town, was proclaimed a National park, and reported contamination could present a potential threat for its conservation. With an aim to evaluate the current pollution status of the Krka River we have applied multibiomarker approach, which encompassed the assessment of trace element bioaccumulation and analyses of several biomarkers in the gill cytosol of brown trout (Salmo trutta Linnaeus, 1758), as a representative fish species in this river. Trace element concentrations in the gill cytosol were determined by high resolution inductively coupled plasma mass spectrometry (HR ICP-MS), and the analyses included thirteen elements, seven essential (Co, Cu, Fe, Mn, Se, V, and Zn) and six nonessential (As, Cd, Cs, Rb, Sr, and Tl). Analyzed biomarkers included the activity of enzymes catalase (CAT) and acetylcholinesterase (AChE), and concentrations of malondialdehyde (MDA), glutathione (GSH), total cytosolic proteins (TP) and metallothioneins (MTs). All biomarkers were analyzed spectrophotometrically, except for MTs, which were determined electrochemically. The study was performed in two sampling campaigns (October 2015 and May 2016) at two sampling sites, the Krka River spring as a reference site, and the location downstream of Knin, as a contaminated site, which was confirmed by analyses of dissolved trace element concentrations in the river water. The concentrations of As, Co, Fe, Mn, Rb, Se, Sr, V, and Zn were higher downstream of Knin in comparison to the reference site, whereas the concentrations of Cd, Cs, Cu, and Tl were comparable at both sites 2. Higher cytosolic concentrations of As, Co, Mn, Se, and Sr in brown trout gills downstream of Knin town in both seasons confirmed the influence of water contamination on trace element bioaccumulation. However, higher concentrations of Cd, Cs, Tl and Fe in brown trout gills were observed at the reference site, which could not be associated to the exposure from the water, and thus association with food and sediment should be considered. The activities and concentrations of biomarkers were generally comparable at both sites in both campaigns, with the exception of higher GSH (biomarker of oxidative stress) and TP (biomarker of general stress) downstream of Knin town in the October sampling. The obtained results confirmed the contamination of the Krka River water with trace elements and consequently higher trace element bioaccumulation in the gills of brown trout downstream of Knin town. However, general absence of the changes in biomarker levels was an indication that observed contamination level was still not high enough to cause observable effects in fish.

biomarkers ; brown trout ; gills ; metal bioaccumulation ; metal pollution ; Krka River

nije evidentirano