Combined use of bioindicators and passive samplers for the assessment of river water contamination with metals

Mining waste as a cause of increased bioaccumulation of highly toxic metals in liver and gills of Vardar chub (Squalius vardarensis Karaman, 1928)

Freshwater contamination with mining waste can result with high concentrations of toxic metals in the water and in fish organs. In North-Eastern Macedonia, several rivers (e.g., Zletovska, Kriva) are exposed to acid mine drainage from active Pb/Zn mines. Previous studies confirmed high concentrations of dissolved metals in their water. This study was performed in liver and gills of Vardar chub (Squalius vardarensis Karaman, 1928) from three Macedonian rivers (Bregalnica, Kriva and Zletovska) in spring and autumn 2012. The aim was to establish if increased exposure to certain metals have resulted with their increased bioaccumulation. The concentrations of 19 elements were measured in cytosolic tissue fractions, to obtain information on metabolically available metal species. The following ranges of cytosolic concentrations of highly toxic elements were measured in the Vardar chub liver (in μg/L): Cd, 1.18-184; Cs, 0.25-25.4; Tl, 0.02-5.80; Pb, 0.70-61.1. Their ranges measured in the gills (in μg/L) were the following: Cd, 0.24-59.2; Cs, 0.39-24.4; Tl, 0.01-1.00; Pb, 0.65-87.2. Although the water of the mining impacted Zletovska River was highly contaminated with several essential metals, especially with Mn and Zn, the majority of essential elements (Na, K, Ca, Mg, Co, Cu, Fe, Mn, Mo, and Zn) did not reflect the exposure level. In contrast, seven nonessential elements reflected the level of exposure in the water. Significantly increased hepatic and gill concentrations of Cs, Rb, Sr, and Tl were detected in Vardar chub from the Zletovska River compared to the other two rivers, of Cd and Pb in the Zletovska and Kriva River compared to Bregalnica, and of V in the Bregalnica River compared to Zletovska and Kriva rivers. Observed significant metal bioaccumulation, in particular of highly toxic elements, as a consequence of exposure to water contaminated with mining waste points to necessity of intensified supervision of mining impacted rivers.

Potentially toxic elements in muscle tissue of different fish species from the Sava River and risk assessment for consumers

Fish from the Sava River are consumed daily by the local people: therefore, concern has been raised about the health implications of eating contaminated fish. In the present study, potentially toxic elements (PTE), such as Zn, Cu, Cr, Ni, Cd, Pb, As, Hg, and methylmercury (MeHg), were determined in ichthyofauna that are commonly consumed. PTE were determined in the fish muscle tissue. Fish were sampled at 12 locations from the source of the Sava River to its confluence with the Danube River during two sampling campaigns, namely; in 2014 under high water conditions and in 2015 under normal water conditions. Due to the different water regimes, different fish species were collected for chemical analysis. We observed that the concentrations of elements analysed in the fish muscle tissue were generally very low, except for those of Hg. Moreover, more than 90% of Hg present in the fish was in its most toxic form, namely MeHg. Especially in fish from the 2015 sampling campaign, Hg and MeHg concentrations increased with fish size, trophic level, and in the downstream direction. In addition, for Pb and As, and to some extent for Cd and Cr, spatial differences were detected in both years. The highest concentrations of PTE were detected in fish from sites with intensive industrial and agricultural activities. The consumption of fish in general does not pose a health risk for the PTE studied, except for Hg/MeHg at selected contaminated sites.

Total and cytosolic concentrations of twenty metals/metalloids in the liver of brown trout Salmo trutta (Linnaeus, 1758) from the karstic Croatian river Krka

Total and cytosolic concentrations of twenty metals/metalloids in the liver of brown trout Salmo trutta (Linnaeus, 1758) were studied in the period from April 2015 to May 2016 at two sampling sites on Croatian river Krka, to establish if river water contamination with metals/metalloids downstream of Knin town has influenced metal bioaccumulation in S. trutta liver. Differences were observed between two sites, with higher concentrations of several elements (Ag, As, Ca, Co, Na, Se, Sr, V) found downstream of Knin town, whereas few others (Cd, Cs, Mo, Tl) were, unexpectedly, increased at the Krka River spring. However, total metal/metalloid concentrations in the liver of S. trutta from both sites of the Krka River were still mainly below previously reported levels for pristine freshwaters worldwide. The analysis of seasonal changes of metal/metalloid concentrations in S. trutta liver and their association with fish sex and size mostly indicated their independence of fish physiology, making them good indicators of water contamination and exposure level. Metal/metalloid concentrations in the metabolically available hepatic cytosolic fractions reported in this study are the first data of that kind for S. trutta liver, and the majority of analyzed elements were present in the cytosol in the quantity higher than 50% of their total concentrations, thus indicating their possible availability for toxic effects. However, the special attention should be directed to As, Cd, Cs, and Tl, which under the conditions of increased exposure tended to accumulate more within the cytosol. Although metal/metalloid concentrations in S. trutta liver were still rather low, monitoring of the Krka River water quality and of the health status of its biota is essential due to a trend of higher metal/metalloid bioaccumulation downstream of Knin town, especially taking into consideration the proximity of National Park Krka and the need for its conservation.

Accumulation of metals relevant for agricultural contamination in gills of European chub (Squalius cephalus)

The study of metal bioaccumulation in the gills of European chub (Squalius cephalus) was conducted in September 2009 at the medium-sized rural river Sutla, characterized by agricultural and municipal type of water contamination. The concentration ranges were established for the first time in the soluble, metabolically available fractions of chub gills for 12 metals, which are environmentally extremely relevant and yet only seldom studied, as follows in a decreasing order: K, 225-895 mg L(-1); Na, 78-366 mg L(-1); Ca, 19-62 mg L(-1); Mg, 13-47 mg L(-1); Rb, 164-1762 μg L(-1); Sr, 24-81 μg L(-1); Ba, 13-67 μg L(-1); Mo, 1.3-16 μg L(-1); Co, 0.7-2.7 μg L(-1); Li, 0.4-2.2 μg L(-1); Cs, 0.2-1.9 μg L(-1); and V, 0.1-1.8 μg L(-1). The concentrations of Fe (1.6-6.4 mg L(-1)) and Mn (16-69 μg L(-1)) were also determined and were in agreement with previous reports. By application of general linear modelling, the influence of different abiotic (metal exposure level) and biotic parameters (fish sex, age, size and condition) on metal bioaccumulation was tested. It was established that bioaccumulation of many metals in fish depended on various physiological conditions, wherein Ba could be singled out as metal exhibiting the strongest association with one of biotic parameters, being significantly higher in smaller fish. However, it was also undoubtedly demonstrated that the concentrations of three metals can be applied as reliable indicators of metal exposure even in the conditions of low or moderate water contamination, such as observed in the Sutla River, and those were nonessential elements Li and Cs and essential element Fe. The results of our study present an important contribution to maintenance of high ecological status of European freshwaters, through enrichment of knowledge on the bioaccumulation of various metals in gills of European chub as frequently applied bioindicator species in monitoring of water pollution.

High-throughput screening assay for the environmental water samples using cellular response profiles

Chemical and physical analyses are commonly used as screening methods for the environmental water. However, these methods can only look for the targeted substance but may miss unexpected toxicants. Furthermore, the synergistic effects of mixture cannot be detected. In order to set up the assay criteria for determining various biological activities at a cellular level that could potentially lead to toxicity of environmental water samples, a novel test based on cellular response by using Real-Time Cellular Analyzer (RTCA) is proposed in this study. First, the water sample is diluted to a series of strengths (80%, 60%, 40%, 30%, 20% and 10%) to get the multi-concentration cellular response profile. Then, the area under the cellular response profile (AUCRP) is calculated. Comparing to the normal cell growth of negative control, a new biological activity index named Percentage of Effect (PoE) has been presented which reflects the cumulative inhibitory activity of cell growth over the log-phase. Finally, a synthetical index PoE50 is proposed to evaluate the intensity of biological activities in water samples. The biological experiment demonstrates the effectiveness of the proposed method.

Pomphorhynchus laevis (Acanthocephala) from the Sava River basin: New insights into strain formation, mtDNA-like sequences and dynamics of infection

Here we report the genetic variability and presence of mtDNA-like sequences of Pomphorhynchus laevis from the chub, Squalius cephalus, caught at the sampling sites along the Sava River and its tributary the Sutla River in Croatia. Sequences of the cytochrome c oxidase subunit 1 (COI) gene of the recovered P. laevis specimens were used for haplotype network construction and phylogenetic analysis. These analyses showed that some specimens contained mitochondrial-like sequences, and they uncovered the existence of a Sava River basin strain different from known strains of P. laevis. This is the first time that P. laevis has been shown to contain mtDNA-like sequences, suggesting the need to exercise caution during COI analyses of P. laevis using universal primers. Highly conserved sequences of two nuclear markers, the ITS region and 18S rRNA, were not helpful for understanding genetic variability or differentiating strains. Furthermore, analysis of the dynamics of P. laevis infections in S. cephalus from the Sava and Sutla Rivers showed decreased prevalence and abundance at sites with inferior water quality, positive association of parasite abundance with fish size, and no clear association of parasite abundance with fish condition index or sex.

Combined use of DGT and transplanted shrimp (Litopenaeus vannamei) to assess the bioavailable metals of complex contamination: implications for implementing bioavailability-based water quality criteria

The diffusive gradients in thin films (DGT) were field deployed alongside the shrimp Litopenaeus vannamei at seven sites with different levels of contamination to assess the potentially bioavailable and toxic fraction of metal contaminants. After 7 days of exposure, several antioxidant biomarkers were quantified in hepatopancreas of exposed shrimps, and tissue levels as well as the total, dissolved, and DGT-labile concentrations of metal contaminants were determined in the pooled site samples. The results showed that the caged shrimps had high tissue contaminant concentrations and significantly inhibited antioxidant responses at the more contaminated sites. DGT-labile metal concentrations provided better spatial resolution of differences in metal contamination when compared with traditional bottle sampling and transplanted shrimp. The total, dissolved, and DGT-labile metal fractions were used to evaluate the potential bioavailability of metal contaminants, comparing with metal accumulation and further linking to antioxidant biomarker responses in tissues of exposed shrimps. Regression analysis showed the significant correlations between DGT-Cu concentrations and tissue-Cu and activities of some biomarker responses in the shrimp hepatopancreas. This indicated that DGT-labile Cu concentrations provided the better prediction of produced biological effects and of the bioavailability than the total or dissolved concentrations. The study supports the use of methods combining transplanted organisms and passive sampling for assessing the chemical and ecotoxicological status of aqueous environments and demonstrates the capability of the DGT technique as a powerful tool for measuring the bioavailability-based water quality in variable coastal environments.

Multielement analysis in the fish hepatic cytosol as a screening tool in the monitoring of natural waters

The possibility of direct measurement of trace elements in hepatic cytosol of European chub (Squalius cephalus) by high-resolution inductively coupled plasma mass spectrometry (HR ICP-MS) after cytosol dilution with Milli-Q water and subsequent acidification was investigated. Due to low detection limits of this procedure, determination of 13 elements (As, Cd, Co, Cu, Fe, Mn, Mo, Pb, Sb, Sn, Sr, V and Zn) was possible in the chub hepatic cytosol, exhibiting excellent measurement repeatability in duplicates. Some of these elements were also measured by HR ICP-MS in acid digested cytosols (Cd, Co, Cu, Fe, Mn, Mo, Sr, V and Zn). Good agreement of the results obtained after sample dilution and sample digestion indicated that complex organic matrix of hepatic cytosol did not affect measurement reliability. Cytosolic concentrations of 13 trace elements in the chub liver were quantified in the following order: Fe, Zn>Cu>Mn>Mo>Sr, V, Cd>Co>As, Pb>Sn>Sb. Unlike Cd, Cu, Fe, Mn and Zn for which the cytosolic concentrations were previously reported after measurement by AAS, cytosolic concentrations of eight additional trace elements characteristic for the liver of chubs inhabiting the low contaminated river water were reported here for the first time (in nanogrammes per gramme)-Mo, 136.8-183.6; Sr, 32.7-63.0; V, 17.5-69.0; Co, 24.3-30.7; As, 9.9-29.5; Pb, 5.8-35.6; Sn, 5.5-12.4; and Sb, 0.9-2.6. The simultaneous measurement of large number of trace elements in the cytosolic fractions of fish tissues, which comprise potentially metal-sensitive sub-cellular pools, could be beneficial as a screening tool in the monitoring of natural waters, because it would enable timely recognition of increased fish exposure to metals.

Assessment of copper and zinc levels in fish from freshwater ecosystems of Moldova

PURPOSE

The aim of this work was to assess the levels of copper and zinc in fish from the main freshwater ecosystems of Moldova, in relation with species, habitat, age, sex, season, and development stage.

METHODS

Fish from Cyprinidae and Percidae families (Cyprinus carpio, Carassius auratus gibelio, Rutilus rutilus heckeli, Abramis brama, Aristichthys nobilis, Hypophtalmichthys molitrix, Sander lucioperca) were collected from Prut and Dniester rivers, Cuciurgan, Dubasari, and Costesti-Stanca reservoirs, and ponds of farms in the Dniester delta. The Cu and Zn content of fish tissues (skeletal muscles, liver, gonads, gills, skin, and scales) was determined by flame atomic absorption spectrophotometer AAS-3, of water by graphite furnace HGA 900 of AAnalist 400.

RESULTS

The level of heavy metals accumulation in muscles of immature fish follows their dynamics in water. The highest concentration of zinc was registered in the gonads of mature fish, and of copper-in the liver. The lowest Cu and Zn contents were recorded in the muscles and are in the United Nations Food and Agriculture Organization safety-permissible levels for human consumption. Cu and Zn contents in muscles of fish depend on specimen age. Their level in fish gonads was sharply increasing during pre-spawning period. During the early developmental stages, the metal concentration in fish eggs and larvae varies within wide limits, but the accumulation pattern is similar in the investigated species.

CONCLUSIONS

The fish represent one of the most indicative factors for the estimation of trace metals pollution in freshwater systems and this is important not only for monitoring purposes, but also for the fish culture ones.

The assessment of natural causes of metallothionein variability in the gills of European chub (Squaliuscephalus L.)

The possible causes of the variability of gill metallothionein (MT) levels were studied on 182 specimens of 2- and 3-year old European chub (Squaliuscephalus L.) from the Sava River in Croatia. The most pronounced differences in MT levels were obtained between three sampling campaigns, and especially between periods with presumably different metabolic activities (April/May 2006 vs. September 2005 and 2006). Next to the probable influence of metabolic activity on MT level, the correlation analysis indicated a significant association between MTs and the fish size. Differences between males and females, as well as between mature and non-mature fish, were not observed in the young group of studied chub even in the spring reproductive season. Based on the analysis of the site-specific MT variability, it could be concluded that, under the conditions of low dissolved metal concentrations in the river water (as reported for the Sava River), MTs seem to be more affected by different biotic factors than by metal exposure. Therefore, MTs measured in this study were considered as the constitutive gill MT levels of young European chub. The constitutive MT ranges were defined separately for the season of lower metabolic rate (autumn: 1.31-2.00 mg g(-1)) and the season of higher metabolic activity (spring: 2.15-2.95 mg g(-1)).

Protein and metal concentrations in two fractions of hepatic cytosol of the European chub (Squalius cephalus L.)

Indigenous specimens of European chub were caught at five sites in Sava River during two successive non-reproductive periods and used as bioindicator organisms for the assessment of metal accumulation. Liver was selected as a target organ and the metal concentrations (Zn, Cu, Fe, Mn, and Cd) were determined in two fractions of hepatic cytosol, namely in untreated (S50) and heat-treated (HT S50) fraction. In addition, the concentrations of total cytosolic proteins were measured in untreated (S50) fractions, whereas the concentrations of specific metal-binding proteins, i.e. metallothioneins, were determined in the heat-treated fractions. Concentrations of Zn and Fe were significantly higher in the untreated compared to heat-treated cytosol, because these metals are associated to the heat-sensitive metalloenzyme and high molecular mass proteins. On the contrary, Cu, Mn and Cd were predominantly present in the heat-treated cytosol, which contains metallothioneins. In both fractions of hepatic cytosol, nonessential metal Cd showed statistically significant increase from the upstream sites (median 5 ng mL(-1)) toward the downstream site Jasenovac (median 11 ng mL(-1)). The metallothionein concentrations, on the contrary, did not differ between sites, probably due to low dissolved and labile concentrations of metals known as metallothionein inducers (Zn, Cu, and especially Cd) in river water. Therefore, Cd concentrations in hepatic cytosol of European chub can be recommended as an early-warning marker of fish chronic exposure to Cd from combined sources, water and ingested food.