Bioaccumulation and biomagnifications of toxic metals and trace elements in freshwater fishes from different trophic levels in the Danube near Belgrade

Иако је и даље у употреби, термин „тешки метал“ различити аутори дефинишу на различите начине бројним параметрима. Извори загађења тешким металима могу бити природни, али су најчешће антропогени. Ова класа загађивача представља значајну претњу за животну средину и врсте које живе у њој, као и потенцијалну претњу за људско здравље. Најбитнија је опасност коју представљају токсични елементи – арсен, жива, кадмијум и олово. Осим токсичних елемената, и елементи у траговима, као и есенцијални микронутријенти, могу показивати токсична својства ако су присутни у великим концентрацијама. У овом раду анализиране су концентрације 18 елемената (Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Ni, Pb, Se, Sr, Zn) у ткивима 11 врста риба – Esox lucius (штука), Alburnus alburnus (укљева), Cyprinus carpio (шаран), Pelecus cultratus (сабљар), Silurus glanis (сом), Lota lota (манић), Gymnocephalus cernua (балавац), Perca fluviatilis (гргеч), Sander lucioperca (смуђ), Babka gymnotrachelus (главоч тркач) и Neogobius melanostomus (главоч округлак). Основни циљ био је да се установи да ли постоје сличности и/или разлике у биоакумулацији елемената у одређеним ткивима код различитих врста. Анализиране врсте су представници различитих трофичких нивоа, што има значајан утицај на биоконцентрацију у ткивима, а може указати и на биомагнификацију појединих елемената дуж трофичког ланца. Врсте су хватане у периоду између 2010. и 2012. године на два локалитета, између 1168. и 1170. речног километра Дунава у Београду. Ови локалитети су бирани због близине ушћа Саве (која доноси додатно загађење) у Дунав, близине урбаног дела Београда, као и близине пољопривредних површина. Анализа 18 елемената у ткивима риба урађена је помоћу индуктивно спрегнуте плазма- оптичке емисионе спектрометрије (ICP-OES). За одређивање старости јединки коришћене су крљушти, жбице пераја (сом) и отолити (манић)...Although still in use, the term “heavy metal” is defined in different ways, based on a number of parameters, by different authors. Sources of heavy metal contamination can be natural, yet they are mostly anthropogenic. This class of pollutants poses a significant threat to environment and species living in it, as well as a potential threat to human health. The most significant threat are the toxic elements – arsenic, mercury, cadmium, and lead. Apart from these toxic elements, both trace elements and essential micronutrients can also show toxic properties if present in large concentrations. The concentrations of 18 elements (Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Ni, Pb, Se, Sr, Zn) in tissues of eleven fish species – Esox lucius (pike), Alburnus alburnus (common bleak), Cyprinus carpio (common carp), Pelecus cultratus (sichel), Silurus glanis (catfish), Lota lota (burbot), Gymnocephalus cernua (ruffe), Perca fluviatilis (perch), Sander lucioperca (pikeperch), Babka gymnotrachelus (racer goby), and Neogobius melanostomus (round goby), were analyzed in this study. The principal aim was to find out if there were any similarities and/or differences in element bioaccumulation in assorted tissues of different species. The analyzed species represent different trophic levels, which has a significant impact on bioconcentration in tissues, and it can as well as point to biomagnification of certain elements along the trophic chain. Species were caught between 2010 and 2012 on two locations, between 1168th and 1170th river kilometer of the Danube River in Belgrade. These locations were selected for their proximity to the confluence of the Sava River (who carries additional pollution) into the Danube, their proximity to the urban area of Belgrade, as well as their proximity to agricultural areas. The analysis of 18 elements in fish tissues was done using an inductively coupled plasma optical emission spectrometry (ICP-OES). For the determination of fish age, scales, ray fins (catfish), and otoliths (burbot) were used..

Relationships of otolith size to fish size – a study on pumpkinseed (Lepomis gibbosus) from Topola Reservoir (Serbia)

Otoliths are calcareous structures commonly used for fish age, size, and taxon determination. Information obtained from the analysis of otoliths can be of great importance for the management of fish populations, including invasive fish species. Pumpkinseed (Lepomis gibbosus) is one of the most successful invaders of Serbian freshwaters. It preys on aquatic invertebrates, fish eggs, and small fish. This species shows high plasticity of life history traits and can tolerate harsh environmental conditions, including hypoxia and high water temperatures. In October of 2020, a total of 28 pumpkinseed individuals from Topola reservoir (44.268229 N, 20.691564 E) were caught with electrofishing device Villager VGI2400 (230 V, 8.7 A, 2.0 kW). In order to determine relationships of otolith to fish size, a total length (TL) and body weight (BW) of each fish were measured as well as otolith area (OA), perimeter (OP), length (OL), and weight (OW). There were no significant differences between left and right otolith regarding OA, OP, OL, and OW (t-test, P>0.94). Significant and strong correlations were recorded for TL and OA (r2=0.936, P<0.0001), TL and OP (r2=0.958, P<0.0001), TL and OL (r2=0.945, P<0.0001), and TL and OW (r2=0.838, P<0.0001). Additionally, significant and strong correlations were recorded for BW and OA (r2=0.844, P<0.0001), BW and OP (r2=0.819, P<0.0001), BW and OL (r2=0.828, P<0.0001), and BW and OW (r2=0.795, P<0.0001). Results indicated that TL-OP relationship is the best predictor of pumpkinseed length, while BW-OW relationship is the weakest predictor of pumpkinseed weight. The common linear regression equations were determined: y = 0.9004x + 3.2643 for OA-TL, y = 0.9079x – 0.4816 for OP-TL, y = 2.4873x – 0.6667 for OL-TL, y = 523.2832x + 5.2364 for OW-TL, y = 3.2985x – 9.6439 for OA-BW, y = 3.2389x – 22.5237 for OP-BW, y = 8.9825x – 23.5786 for OL-BW, and y = 1966.5664x – 2.7114 for OW-BW. The obtained equations allow the calculation of pumpkinseed TL and BW based on the set of data on the morphological characteristics of the otoliths. Of the considered otolith parameters, otolith weight is the least suitable character for estimation of pumpkinseed size

Determination of the development stage of erythrocytes in the common nase (Chondrostoma nasus) using different classification methods.

Fish erythrocytes released from erythropoietic sites are immature. During circulation they increase their own surface while the cell body and nuclei begin to become more elliptical and less spherical during maturaration. The relative abundance of different developmental stages represents an erythron profile which could be a more sensitive indicator of contamination than classic hematological indices. In this study, we analyzed blood smears of the Common Nase (Chodrostoma nasus) with the main goal to identify the determinants of the developmental stage of erythrocytes. Based on parameters developmental stages, erythrocytes are categorized into immature, intermediate or mature. In this investigation we have used four classification methods: the Two Step Cluster analysis, the K-Means Cluster analysis and Neural Neworks - Multilayer Perceptron and an Ordinal Regression Model. Our findings clearly justify that Multilayers Perceptron and ORL models are appropriate to classify the developmental stage of fish erythrocytes

Comparative evaluation of liver enzymes activities in Vimba bream and Common nase living under the same ecotoxicological conditions

The present study was carried out to investigate the differences in some enzymatic components of liver in vimba bream (Vimba vimba) and common nase (Chondrostoma nasus). For this purpose, 33 healthy vimba bream and 20 common nase were collected from commercial catches on the Danube River, near Belgrade (1172-1173 rkm), in 2016. The blood samples were taken and after separation of serum, the values of Aspartate aminotransferase (AST) and Alanine aminotransferase (ALT) enzymes activities were measured. Based on obtained results, the values of AST and ALT enzymes activities were slightly lower in the common nase compared to vimba bream, which is a possible indicator of better health and physiological status, and greater resistance to environmental pollutants present in the habitat. This difference was, however, not statistically confirmed. Considering that the selected fish were captured by the same method, having a similar ecology, living in similar habitats and under similar ecotoxicological conditions, it is not surprising that the differences in the activity of the measured liver enzymes were minimal. Since common nase is important bioindicator species, similar results could indicate that vimba bream could be considered as replacement species for this types of research, if future studies indicate the decline or endangerment of common nase populations

Intestinal content analyses of pumpkinseed Lepomis gibbosus (Linnaeus, 1785) in five small reservoirs – central Serbia

Lepomis gibbosus (pumpkinseed) was first recorded as a non-native fish in Serbia in the 1930s in the Tisza River. The species currently inhabits almost the entire region of the Black Sea basin in Serbia, but has no economic value. The current range of the pumpkinseed covers more than 50% of the total Serbian area and is also naturalised in Serbian waters. The pumpkinseed feeds on bottom fauna, small fish, fish roe and juvenile fish, which together with competition for habitat and spawning sites can have a negative impact on native species. The most common prey of younger specimens is zooplankton, while adult specimens feed on larger organisms such as larvae and pupae of insects, molluscs or crustaceans. The composition of the prey varies seasonally and depends on the composition of the community. The main objective of the study was to analyse the differences in the feeding habits of pumpkinseed in five reservoir. Samples were collected from five reservoirs in central Serbia (<200 asl, Markovačko, Topola, Vlaški Do, Jatagan, Kudreč) using standard electrofishing equipment. All sampled reservoirs had mud substrate, except Jatagan Reservoir, which had gravel substrate. The sampled fish were identified on site based on morphological characteristics using identification keys. The sampled fish were measured using total body length and weight. The total sample consisted of 354 pumpkinseed individuals whose body weight ranged from 3.66–9.52 g and body length from 6.01–8.41 cm. The number of individuals with intestinal content was 282, while the number of individuals with empty stomachs was 72. The following macroinvertebrate taxa were identified during the examination of the gut contents: aquatic insects (Chironomidae, Chironomidae-pupae, Diptera, Ceratopogonidae, Trichoptera, Ephemeroptera, Odonata, Heteroptera, Coleoptera), Gammaridae, Mollusca, Bivalvia, Gastropoda, Nematoda. Undetermined terrestrial insects were also recorded. Most prey were found in the Kudreč Reservoir, and the greatest diversity was in the Topola Reservoir. Jatagan Reservoir had the lowest number of prey items, which may be due to the substrate type. The high number of aquatic insect taxa could be explained by the small surface area of the reservoir and the presence of aquatic vegetation

Age, growth, and length-weight relationship of common nase (Chondrostoma nasus) in the Danube River near Belgrade (Serbia).

Growth parameters, length-weight relationship, and condition of the common nase (Chondrostoma nasus) in the Danube River near Belgrade were analyzed on a sample (n=30) from the commercial catch, caught between March and May 2017. The total body length of the sampled individuals ranged from 268 to 401 mm, and body weight from 195 to 875 g. Age was determined from scales and individuals aged 5+, 6+ and 7+ were present in the sample, in approximately the same percentage. The regression coefficient of the length-weight relationship was b = 3.28. The value of b > 3 indicates a positive allometry, which denotes that the weight growth rate is greater than the length growth rate. The Fulton’s condition factor ranged from 0.90 and 1.36, with the mean value of 1.07. The parameters of the von Bertalanffy growth function were L∞ = 697.84, k = 0.08, and t0 = -1.72. The estimated phi-prime growth performance index (j') was 4.60. The lengths were back-calculated using the method of Monastyrsky, and the greatest relative growth increment was observed in the first and second year of life

Age, growth, and length-weight relationship of common nase (Chondrostoma nasus) in the Danube River near Belgrade (Serbia).

Growth parameters, length-weight relationship, and condition of the common nase (Chondrostoma nasus) in the Danube River near Belgrade were analysed on a sample (n=30) from the commercial catch, caught between March and May 2017. The total body length of the sampled individuals ranged from 26.8 to 40.1 cm, and body weight from 195 to 875 g. Age was determined from scales and individuals aged 5+, 6+ and 7+ were present in the sample, in approximately the same percentage. The regression coefficient of the length-weight relationship was b = 3.28. The value of b > 3 indicates a positive allometry, which denotes that the weight growth rate is greater than the length growth rate. The Fulton’s condition factor ranged from 0.90 and 1.36, with the mean value of 1.07. The parameters of the von Bertalanffy function were L∞ = 697.84, K = 0.08, and t0 = -1.72. The estimated phi-prime growth performance index (') was 4.60. The lengths were back-calculated using the method of Monastirsky, and the greatest relative growth increment was observed in the first and second year of life

Difference in element accumulation and histopathology of Pontic shad (Alosa immaculata) migrants caught in the Danube River in interval of one decade

Pontic shad (Alosa immaculata) is an anadromous species that lives in the Black Sea and Sea of Azov and migrates into the Danube, Don and other rivers to spawn. It is still economically important fish species in the Danube River. As the North-Western part of the Black Sea is heavily polluted investigation was performed to determine heavy metal and element accumulation in muscle tissue of Pontic shad as well as to record the level of histopathological changes. Pontic shad specimens were caught on 863 river kilometer of the Danube and the first investigation was performed during 2007 and repeated one decade later in the period 2017-2019. Element analysis was performed by inductively-coupled plasma – optic emission spectroscopy (ICPOES). In both sampling periods, only concentrations of arsenic (As), copper (Cu), iron (Fe), magnesium (Mg), strontium (Sr), and zinc (Zn) were above detection limit. Higher concentrations of As, Cu, and Zn were detected in 2007, while higher concentrations of Fe, Mg, and Sr were measured in 2019. Differences in concentrations of these elements, between sampling periods, were statistically significant. The gills of sampled fish were assessed using histopathology as a marker of general fish health state, using semi-quantitative scoring system. The histopathological results revealed different pattern of histopathological alterations in the gills of fish sampled during two distinct time periods. According to the method used, there were no difference in total gill histopathological index, but alterations were specific for fish sampled at two time points. Hyperemia and hyperplasia of respiratory epithelium dominated in fish sampled at the year 2007, while necrosis of branchial tissue prevailed in fish sampled a decade later

Growth parameters of vimba bream (Vimba vimba) in the Danube River near Belgrade (Serbia).

Age, growth, and length-weight relationship of the vimba bream (Vimba vimba) were analysed on a sample of 43 individuals from a commercial catch, caught between March and May 2017 in the Danube River near Belgrade. Total body length of the sampled fish ranged from 26.3 to 34.5 cm, and body weight from 223 to 554 g. Age of the sampled fish, determined from scales, ranged from 5+ to 8+, with the largest percentage of individuals in the age class 6+. The regression coefficient of the length-weight relationship was b = 3.28, which indicates a positive allometry. The parameters of the von Bertalanffy function were L∞ = 543.82, K = 0.09, and t0 = -2.41. The estimated phi-prime growth performance index (') was 4.44. The Fulton’s condition factor ranged from 1.04 to 1.42, with the mean value of 1.23. The length-at-age was back-calculated with the method of Monastyrsky, and the greatest relative growth increment was observed during the first two years of life

Literature survey on fish tissues contamination by heavy metals and elements in the Danube River, from 1433-845rkm.

Heavy metals have high potential to enter and accumulate in food chains and therefore are considered as critical contaminants of aquatic ecosystems (Erdoğrul and Erbilir 2007). Given that fish are situated at the top of the food chain they can accumulate large amount of heavy metals (Yilmaz et al. 2007). Heavy metals are taken up through different organs of the fish because of the affinity between them, and then are concentrated at different levels in different organs of the body (Bervoets et al. 2001). Accumulation of heavy metals in muscle tissues was the most studied, given that muscle tissue is the main fish part that is consumed by humans (Begum et al. 2013; Storelli et al. 2006). However, it is important to analyze other tissues since muscles are not always a good indicator of the whole fish body contamination (Has-Schön et al. 2006). The Danube River is the second longest river in Europe and runs through Serbia at a length of 587.4 km. The biggest industrial capacities are largely located on the Danube river banks - Belgrade, Novi Sad, Pančevo and Smederevo (Petrović 2015). The main problem is that none of them has any kind of system for treating municipal wastewaters (Veljković 2005). Within this study, published articles regarding heavy metal accumulation in different tissues of fish in the Danube in Serbia were analyzed in order to evaluate which species, tissues and elements were the most represented in the analyses. The main aim was to assess present practices in research of heavy metal pollution in this region, as well as to identify key gaps regarding the particular river sections, types of pollutants, tissues, and trophic and functional groups of fish communities that were inadequately represented in research