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Summary. Lake Ludaš is a protected nature reserve in Serbia that has been the focus of scientific interest, due to perpetual water quality deterioration that has led to consistent cyanobacterial blooms for almost five decades. To describe the possible effects of cyanotoxins on fish (Carrasius gibelio) inhabiting Lake Ludaš, several examinations were performed in November of 2018, including: assessment of water quality (physical and chemical parameters, as well as water microbiology), and assessment of several tissues of C. gibelio (micronucleus test, comet assay, and histopathological analyses). The water quality of Lake Ludaš has been categorized as class III, indicating moderate pollution. Physical and chemical parameters from November of 2018 seemed to be within acceptable levels. Examined fish tissues showed signs of DNA damage (highest in the blood, followed by the liver and gills), and histological alterations (in the liver and gills). Although other xenobiotics can induce similar changes, cyanotoxins could be the most likely cause of the observed alterations in C. gibelio tissues. The present study demonstrates the need to monitor this important wetland of international significance, since the living organisms in Lake Ludaš are showing signs of environmental stress suggesting that the preservation and natural balance of this ecosystem could be in danger.

Biomonitoring predstavlja neophodnu komponentu tradicionalnih tehnika monitoringa, sa ciljem da se uspostavi veza izmeŤu spoljašnjih koncentracija zagaŤivaţa, koncentracija zagaŤivaţa u tkivima bioindikatora i ranih štetnih efekata po ispitivane organizme. Ribe su korisni bioindikatori i ţesto se primenjuju u ekogenotoksikološkim ispitivanjima. U ovoj studiji, procena stanja kvaliteta površinske vode vršena je na reci Savi na lokalitetu Duboko i na reci Dunav na lokalitetu Višnjica tokom 2014. godine, kako bi se procenio uticaj razliţitih sezona na variranje parametara kvaliteta i odgovor biomarkera deverike, krupatice i crnooke deverike. Procena kvaliteta vode vršena je merenjem fiziţko-hemijskih i mikrobioloških parametara fekalnog i organskog zagaŤenja. Procena genotoksiţnog potencijala vršena je primenom alkalnog komet testa za kvantifikaciju DNK oštešenja u šelijama krvi, jetre i škrga riba, kao biomarkera izlaganja. Histopatološke promene u jetri i škrgama prašene su kao biomarker efekta. Paralelno, prašene su koncentracije metala i metaloida u jetri, škrgama, gonadama i mišišu, primenom metode ICP-OES. Na lokalitetu Višnjica zabeleţen je viši nivo fekalnog i organskog zagaŤenja. Na lokalitetu Duboko zabeleţene su više koncentracije ispitivanih elemenata u sva ţetiri tkiva, u poreŤenju sa lokalitetom Višnjica. Na oba lokaliteta škrge su akumulirale najviše koncentracije metala i metaloida, a mišiš najniţe. Na oba lokaliteta, krv je bila tkivo sa najvišim nivoom DNK oštešenja, dok je jetra tokom vešine meseci imala najniţe DNK oštešenje. Na lokalitetu Višnjica zabeleţene su više vrednosti DNK oštešenja krvi, na lokalitetu Duboko više vrednosti DNK oštešenja škrga, dok je nivo DNK oštešenja u šelijama jetre na oba lokaliteta bio pribliţno jednak. Na lokalitetu Duboko pri najvešim vrednostima histopatološkog indeksa škrga zabeleţeno je blago do umereno oštešenje, a na lokalitetu Višnjica umereno do teško oštešenje škrga. Na oba lokaliteta, jetra je bila organ sa vešim obimom histopatoloških promena u odnosu na škrge. Sveukupno, škrge kao prvi organ u direktnom kontaktu sa zagaŤivaţima iz vode pokazale su vešu akumulaciju ispitivanih elemenata i viši nivo DNK oštešenja, dok je jetra kao glavni organ za procesuiranje zagaŤivaţa iz vode i hrane pokazala viši nivo histopatoloških promena. Odabrane vrste pokazale su se kao pogodni bioindikatori za in situ ispitivanja efekata zagaŤenja. Biomonitoring represents an essential part of traditional monitoring techniques with the aim to establish relationship between external concentrations of pollutants, concentrations of pollutants in the tissues of bioindicators and early adverse effects in examined organisms. Fish are useful bioindicators often used in ecogenotoxicological studies. In this study, assessment of the surface water quality was performed on the Sava River locality Duboko and on the Danube River locality Višnjica during 2014 in order to examine the impact of different seasons on the variation of the quality parameters and biomarker response in common bream, white bream and white-eye bream. Assessment of the water quality was performed based on the physico-chemical parameters and microbiological parameters of fecal and organic pollution. Genotoxic potential was assessed by using the alkaline comet assay in order to quantify DNA damage level, in blood, liver and gill cells, as a biomarker of exposure. Histopathological analyses of liver and gill tissue were monitored as a biomarker of effect. Additionally, concentrations of metals and metalloids in liver, gills, gonads and muscle were performed by the ICP-OES method. The higher level of fecal and organic pollution was present on the locality Višnjica. The higher concentrations of examined elements in all four tissues were present in fish from the locality Duboko, in comparison to the locality Višnjica. At both sites gills accumulated the highest concentrations of metals and metalloids, while muscle accumulated the lowest concentrations. Blood was the tissue with the highest level of DNA damage, while liver had the lowest level of DNA damage during most of the months at both sites. Higher DNA damage level in blood cells was observed at the locality Višnjica, in gill cells at the locality Duboko, while the level of DNA damage in liver was approximately the same at both localities. Based on the highest level of histopathological index of gills at the locality Duboko gills were slightly to moderately damaged, while at the locality Višnjica gills were moderately to heavily damaged. At both localities liver had higher level of histopathological alterations in comparison to gills. Overall, gills as the first organ in direct contact with contaminants form water showed higher level of examined elements and DNA damage, while the liver as the main organ for processing contaminants from water and food showed higher level of histopathological alterations. Examined fish species proved to be useful bioindicators for in situ assessment of the pollution effects.