| To investigate heavy metal pollution in fish from the upper reaches of the Yangtze River and the ecotoxicological effects of heavy metal exposed on the fish, field investigation and Laboratory research were carried out. In experimentⅠ, From March to June and September to November in 2012 to 2014, eleven fish species(Silurus meridionalis, Leptobotia elongata, Silurus asotus, Ancherythroculter kurematsui, Carassius auratus auratus, Cyprinus carpio, Pelteobagrus vachellii, Pseudobagrus emarginatus, Myxocyprinus asiaticus, Culter oxycephaloides, and Siniperca knerii) were collected from the Wanzhou section of the Three Gorges Reservoir. Four fish species(S. meridionalis, P. vachellii, Coreius guichenoti, and C. carpio) were collected from the Zhuyang section of the Yangtze River. Five fish species(S. knerii, S. asotus, Hemibagrus macropterus, C. auratus auratus, and C. carpio) were collected from the Fushun section of the Tuo River and seven fish species(L. elongata, C. guichenoti, Pelteobagrus nitidus, S. asotus, C. carpio, C. auratus auratus, and Rhinogobio cylindricus) were collected from the Panzhihua section of the Jinsha River. The sample size for each fish species ranged from 3 to 23, and the total number of samples was 307. The contents of lead(Pb), chromium(Cr), cadmium(Cd), arsenic(As) and mercury(Hg) in muscle tissues and the Contents of Pb, Cr, and Cd in whole fish of the fish species were analyzed using microwave digestion and atomic absorption spectrometry. In experimentⅡ, The contents of Pb, Cr, Cd, As, and Hg were analyzed in the liver(hepatopancreas), kidney, gastrointestinal tract, gill, bone, muscle, skin, and scale tissues of the four fish species(S. meridionalis, P. vachellii, C. guichenoti, and C. carpio) from the Zhuyang section of the Yangtze River using microwave digestion and atomic absorption spectrometry. In experiment Ⅲ, to examine the ecotoxicological effects of Cd expose on the S. meridionalis. The juveniles of southern catfish which were bred using artificial fertilization was exposed to five nominal Cd treatments at the concentrations of 0(control), 62.5, 125, 250 and 500 μg / L for 8 weeks in artificial soft water(25 mg Ca CO3/L) at 27.5℃, respectively. After the waterborne Cd exposure experiment finished, growth performance, the ability of antioxidant, energy metabolism and Cd accumulation were measured. The main results were as follows:1、The metal contents in whole fish of eleven fish species from the Wanzhou section ranged from 46.32 to 220.60 μg/kg for Pb, 41.39 to 125.12 μg/kg for Cr, and 14.57 to 167.67 μg/kg for Cd, respectively. The contents of Pb, Cr and Cd in whole fish of L. elongata were highest. The metal contents in muscle of eleven fish species ranged from12.28 to 89.39 μg/kg for Pb, 24.10 to 75.44 μg/kg for Cr, 0.95 to 44.28 μg/kg for Cd, 24.97 to 84.34 μg/kg for As and ND to 108.10 μg/kg for Hg, respectively. The highest content of Pb、Cr、Cd、As in muscle was found in L. elongate and the highest content of Hg in muscle was found in P. emarginatus.2、The metal contents in whole fish of four fish species from the Zhuyang section ranged from 30.78 to155.98 μg/kg for Pb, 37.49 to 62.44 μg/kg for Cr and 16.66 to 20.37 μg/kg for Cd, respectively. The highest content of Pb and Cr in whole fish was found in C. carpio and the highest content of Cd was found in S. meridionalis. The metal contents in muscle of four fish species ranged from 14.76 to 52.69 μg/kg for Pb, 35.77 to 47.92 μg/kg for Cr, 1.01 to 2.48 μg/kg for Cd, and 23.53 to 33.61 μg/kg for As respectively. The Hg content in muscle of the four tested fish species were below the limit of detection. The highest contents of Pb, Cr and As in muscle was found in C. carpio and the highest contents of Cd in muscle was found in C. guichenoti.3、The metal contents in whole fish of five fish species from the Fushun section of Tuo River ranged from 54.41 to113.44 μg/kg for Pb, 65.50 to121.02 μg/kg for Cr and 13.22 to 25.16 μg/kg for Cd, respectively. The highest content of Pb in whole fish was found in C. auratus auratus and the highest content of Cd and Cr was found in H. macropterus. The metal contents in muscle of five fish species ranged from 30.53 to 47.28 μg/kg for Pb, 35.60 to 85.31 μg/kg for Cr, 1.74 to 3.26 μg/kg for Cd, and 25.82 to 44.96 μg/kg for As, ND to 72.81 μg/kg for Hg, respectively. The highest contents of Pb, Cd and As in muscle was found in C. auratus auratus and the highest contents of Cr and Hg in muscle was found in H. macropterus.4、The metal contents in whole fish of seven fish species from the Panzhihua section of Jinsha River ranged from 61.47 to 378.91 μg/kg for Pb, 73.50 to 130.76 μg/kg for Cr and 18.45 to 214.28 μg/kg for Cd, respectively. The highest content of Pb, Cd and Cr in whole fish was found in L. elongate. The metal contents in muscle of seven fish species ranged from 37.10 to 109.56 μg/kg for Pb, 44.97 to 78.41 μg/kg for Cr, 2.92 to 40.79 μg/kg for Cd, and 27.20 to 69.07μg/kg for As, ND to 72.19 μg/kg for Hg, respectively. The highest contents of Pb, Cr, Cd, As, and Hg in muscle was found in L. elongate.5、The Pb content in various tissues of four fish species from Zhuyang ranged from 14.76 to 615.61 μg/kg. The highest content of Pb was found in bone and scale tissues, while, the lowest content of Pb was found in muscle tissues. The Cr content in various tissues of four fish species from Zhuyang ranged from 27.03 to 248.20 μg/kg. The highest Cr content was found in the gastrointestinal tract, with the only exception being C. guichenoti; the lowest Cr content was found in muscle. The Cd content in various tissues of four fish species from Zhuyang ranged from 1.01 to 502.02 μg/kg. The highest Cd content was found in the kidneys, and the lowest in muscle. The As content in various tissues of four fish species from Zhuyang ranged from 19.77 to 84.42 μg/kg. The As content in the gastrointestinal tract was the highest among the tested tissues. The Hg concentrations in all of the organs and tissue samples of the four tested fish species were below the limit of detection.6、With the increasing Cd concentration, the contents of malondialdehyde(MDA) in gill, liver, kidney and intestines increased. The activity of total antioxidant capacity(T-AOC) and superoxide dismutase(SOD) and the content of glutathione(GSH) in gill, liver, and kidney decreased, with the increasing Cd concentration. The activity of T-AOC, catalase(CAT) and the content of GSH in intestines was not significant change with the increasing Cd concentration(P > 0.05).7、With increasing Cd concentration, resting metabolic rate of the exposure groups showed in the trend of first increased then decreased. 62.5 μg Cd /L, 125 μg Cd /L and 250 μg Cd /L experiment groups showed a significant higher resting metabolic rate than that in control group(P < 0.05). No significant differences in the resting metabolic rate was found between highest Cd concentration experiment groups(500 μg Cd /L) and control group(P >0.05).8、Energy expended on SDA and SDA coefficient decreased gradually with the increasing Cd exposed concentration. 250 μg Cd / L and 500 μg Cd / L experiment groups showed a significantly lower SDA consumption energy and SDA coefficient than those in control group(P < 0.05).9、With the increasing Cd exposed concentration, stateⅢ respiration rate of liver decreased. When waterborne Cd concentration was higher than 125 μg /L, Cd exposed groups showed a significant lower state Ⅲ respiration rate than that in control group(P < 0.05).10、The activity of alanine transaminase(ALT)and aspertate aminotransferase(AST)in muscle appeared in the trend of first increased then decreased, with increasing Cd concentration. 125 μg Cd/L, 250 μg Cd /L and 500 μg Cd /L experiment groups showed a significantly higher activity of ALT in muscle than that in control group(P < 0.05). The activity of AST in muscle of 125 μg Cd/L and 250 μg Cd /L experiment group was significantly higher than that in control group(P < 0.05). The activity of AST in liver appeared in the trend of first increased then decreased, with increasing Cd concentration. The activity of AST in liver of 250 μg Cd / L experiment group was significantly higher than that in control group(P < 0.05).11、With increasing Cd concentration, the content of protein in muscle and liver decreased. The content of protein in muscle of each Cd exposed groups was significantly lower than that in control group(P < 0.05). 250 μg Cd /L and 500 μg Cd /L experiment groups showed a significantly lower the content of protein in liver than that in control group(P < 0.05). With increasing Cd concentration, the content of hepatic glycogen decreased. 250 μg Cd /L and 500 μg Cd /L experiment groups showed a significantly lower content of hepatic glycogen than that in control group(P < 0.05). With increasing Cd concentration, the content of glucose in liver increased. 500 μg Cd /L experiment groups showed a significantly higher content of hepatic glycogen than that in control group(P < 0.05).12、Final body mass, Specific weight growth rate(SGR)decreased with the increasing Cd exposed concentration. 250 μg Cd /L and 500 μg Cd / L experiment groups showed a significantly lower final body mass and SGR than those in control group(P < 0.05). The content of crude protein and crude fat and energy density in whole fish decreased with the increasing Cd exposed concentration. 250 μg Cd /L and 500 μg Cd / L experiment groups showed a significantly lower the content of crude protein in whole fish than that in control group(P < 0.05). 125μg Cd /L, 250 μg Cd /L and 500 μg Cd / L experiment groups showed a significantly lower the content of crude fat and energy density in whole fish than those in control group(P < 0.05).13、Total feed intake, feed conversion rate, apparent digestibility and protein apparent digestibility decreased, with the increasing Cd exposed concentration. Each Cd tested groups showed a significantly lower total feed intake and feed conversion rate than those in control group(P < 0.05). Apparent digestibility and protein apparent digestibility of 250 μg Cd /L and 500 μg Cd/ L experiment groups was significantly lower than that of the control group(P < 0.05).14、Growth energy(G) of test fish decreased along with the increasing Cd exposed concentration. Each Cd treatment groups showed significantly lower growth energy than that in control group(P < 0.05). Resting metabolic energy(RMR) of test fish in each Cd experiment groups was significantly higher than that in control group(P < 0.05). 250 μg Cd / L and 500 μg Cd /L experiment groups showed a significantly lower SDA consumption energy than that in control group(P < 0.05). 250 μg Cd / L and 500 μg Cd /L experiment groups showed a significantly higher feces energy(F) than that in control group(P < 0.05). The excretion energy(U) in each Cd treatment groups was significantly higher than that in control group(P < 0.05). The conclusions suggested in this study were as follows:1、Fish we tested, that reside in inhabiting the Wanzhou section of the Three Gorges Reservoir, the Zhuyang section of the Yangtze River, the Fushun section of the Tuo River and the Panzhihua section of the Jinsha River, are suffered from the different extent of Pb, Cr, Cd, As, and Hg pollution. The Pb, Cr, Cd, As, and Hg contents in fish muscles from the four sample sites are lower than the safety limits established by China and the European Union and so are likely safe for human consumption.2、Metals accumulate in the bodies of fish in a tissue-specific manner. The main target organs for Pb accumulation are the skeleton and the scales, the main target organs for Cd accumulation are the kidneys and the liver, and the main target organ for Cr and As accumulation is the gastrointestinal tract. The heavy metal content in fish muscle is lower than that in other tissues and organs, and it might be inappropriate to use the heavy metal content in fish muscle as an indicator of the extent of environmental heavy metal pollution or as a way to determine the impacts of heavy metal exposure on different fish species.3、Waterborne cadmium exposure causes the oxidative damage of tissues and organs, and interferes with antioxidant system of fish. The gill was most sensitive to oxidative damage, followed by the liver and the kidney, intestines was the least affected tissue. The increasing or maintaining antioxidant response failed to prevent lipid peroxidation of Cd to fish body organs.4、Under certain Cd concentration stress conditions, southern catfish, that may adjust physiological function can enhance the strength of metabolism and utilize energy substance reserved in body to supply the extra energy requirement for resisting the Cd toxicological stress.5、After waterborne Cd exposure, decreasing protein apparent digestibility of southern catfish lead to decrease energy expended on SDA and SDA coefficient.6、 After waterborne Cd exposure, excretion energy and feces energy of southern catfish increase and assimilation energy reduce. Moreover, in the assimilation energy, the energetic proportion for metabolism is increased while the energetic proportion for growth is reduced. |
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