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The assessment of metal availability and the effects on feral fish in the rivers under the impact of mining activities

Ramani, Sheriban (2019) The assessment of metal availability and the effects on feral fish in the rivers under the impact of mining activities. Doctoral thesis, Faculty of Veterinary Medicine, University of "Ss. Cyril and Methodius" in Skopje.

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Abstract

Mine waste is recognized as one of the most serious threats to freshwater ecosystems, and it still represents one of the greatest environmental concerns in North Macedonia. Contamination of freshwater ecosystems with mining waste can result with high concentrations of toxic metals in the water, and their bioaccumulation in the organs of aquatic organisms, especially after long-term exposures, consequently causing various sub-toxic and toxic effects in those organisms. In this study, the impact of active Pb/Zn mines Zletovo and Toranica on the water quality of three rivers (Bregalnica, Zletovska, and Kriva) in the northeastern part of North Macedonia was assessed during spring and autumn 2012, by analysis in the surface water and in two target organs (gills and liver) of selected aquatic bioindicator organism (Vardar chub, Squalius vardarensis). The aim of the study was to deepen the understanding of the mining influence on freshwater ecosystems based on the assessment of metal exposure, by determining dissolved metal concentrations in the surface water, on the assessment of metal bioaccumulation, by determining metal concentrations in the cytosols of liver and gills of Vardar chub, and the assessment of final effects of water contamination on Vardar chub, by defining histopathological changes in the fish liver and gonads, as well as fish general health status. The Bregalnica River, near Shtip, was characterized mainly by weak contamination with As, Ba, Fe, Mo, Ti, U, V, nitrates, and phosphates, which all together indicated the impact of agricultural activities; however, an impact of the mines was not observed. Contrary, in both Zletovska and Kriva rivers a clear impact of Pb/Zn mines on water quality was observed. In the Zletovska River water, increased concentrations of Cd, Co, Cs, Cu, Li, Mn, Ni, Pb, Rb, Sn, Sr, Tl, Zn, sulphates, and chlorides were found, and they were especially high in autumn (e.g., Cd 2.0 µg L -1; Mn 2.5 mg L-1; Zn 1.5 mg L-1) during the extremely low water level, confirming the severe impact of the mine waste on the water quality of the Zletovska River. In the Kriva River, increased Cd (0.270 µg L-1) and Pb (1.85 µg L-1) concentrations, indicating the impact of the mining waste, were found only in spring, possibly due to sediment resuspension during greater water discharge. Contrary, in autumn, high increase of nutrients was recorded in the surface water of the Kriva River, revealing the additional impact of the waste from cultivated land. For the assessment of metal bioaccumulation in the organs of Vardar chub, 19 elements were measured in the cytosolic fractions of the gills and liver, to obtain information on metabolically available metal species. The following ranges of cytosolic concentrations of few highly toxic elements were measured in the Vardar chub gills from all three rivers (in µg L-1): Cd, 0.24-59.2; Cs, 0.39-24.4; Tl, 0.01-1.00; and Pb, 0.65-87.2. Their ranges measured in the liver (in µg L-1) were the following: Cd, 1.18-184; Cs, 0.25-25.4; Tl, 0.02-5.80; and Pb, 0.70-61.1. The majority of essential elements (Na, K, Ca, Mg, Co, Cu, Fe, Mn, Mo, and Zn) did not reflect the exposure levels, indicating the strict physiological regulation of their concentrations. The only exception was essential element Se, which was present in the highest concentrations in both seasons and in both organs at the Kriva River, probably due to increased exposure in the river water. With the exception of Ba, all studied nonessential elements (Cd, Cs, Pb, Rb, Sr, Tl, and V) reflected the level of exposure in the river water. Significantly increased gill and hepatic concentrations of Cs, Rb, Sr, and Tl were always 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, depending on the season, and of V in the Bregalnica River compared to Zletovska and Kriva rivers in both seasons. For the assessment of the health of Vardar chub, general indicators of exposure to environmental stressors were used, such as condition factor, organo-somatic indices and external/internal macroscopic lesions, as well as histopathological assessment of liver and gonads. In both seasons, the smallest fish, the lowest Fulton condition indices, the lowest hepatosomatic indices and the lowest gill masses were observed for Vardar chub at the Zletovska River, most likely associated to severe metal contamination of surface water. Total prevalence of external/internal lesions was similar in all three rivers and relatively low, around 20%. However, several external/internal lesions were more pronounced in severely metal contaminated Zletovska River. The spectrum of histological lesions observed in Vardar chub liver varied from non-specific minor degenerative conditions, such as lymphocyte infiltration, fibrosis, parasites, granulomas and lipidosis, to extensive and more severe changes such as bile duct proliferation, necrosis, megalocytosis, light-dark hepatocytes and hepatocytes regeneration. Prevalence of hepatic lesions was higher in the mining impacted rivers (in Kriva, 70%; in Zletovska, 59%) compared to agriculturally impacted Bregalnica River (38%). Histological assessment of gonads revealed good reproductive health in all three rivers, indicating higher tolerance of gonads than liver to contaminant exposure. Although the results of histopathological assessment cannot be directly associated to a single contaminant, some lesions observed in this study were probably a consequence of environmental metal contamination. This study has clearly demonstrated detrimental effect that mining pollution has on water quality and health of native freshwater fish. Such information is essential in a process of creating water management plans, with an aim to protect, as well as to improve, quality of freshwater ecosystems worldwide, and especially in areas affected by active mining.

Item Type: Thesis (Doctoral thesis)
Uncontrolled Keywords: agricultural activities; condition factor; cytosolic fraction; essential metals; mine waste; fish, gills; gonads; histopatology; liver; bioaccumulation; nonessential metals; organo-somatic indices; rivers; Vardar chub
Subjects: NATURAL SCIENCES > Chemistry
NATURAL SCIENCES > Biology
NATURAL SCIENCES > Interdisciplinary Natural Sciences
BIOMEDICINE AND HEALTHCARE > Veterinary Medicine
Divisions: UNSPECIFIED
Projects:
Project titleProject leaderProject codeProject type
Croatian-Macedonian bilateral project “The assessment of the availability and effects of metals on fish in the rivers under the impact of mining activities”Zrinka DragunUNSPECIFIEDBilateral
Depositing User: Zrinka Dragun
Date Deposited: 27 Feb 2020 13:00
Last Modified: 27 Feb 2020 13:00
URI: http://fulir.irb.hr/id/eprint/5287

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