| With the rapid development of productivity and economy,the impact of human activities on the environment is increasing day by day.The massive consumption of fossil fuels such as coal and petroleum has brought about a series of environmental problems such as global warming,soil pollution and water pollution.Polycyclic aromatic hydrocarbons(PAHs)are a group of main persistent organic pollutants with carcinogenic,teratogenic and mutagenic characteristics causing water and soil pollution..They can accumulate in organisms and threaten the life safety of aquatic organisms and humans seriously.Monitoring the pollution status of the water environment can evaluate the quality of the water environment and further assess the health risks of pollutants,which are the primary tasks of water pollution prevention and control.Compared with traditional physical-chemical monitoring methods,biological monitoring has been widely concerned because of its timeliness,sustainability and nondestructive.Therefore,it has been applied widely into river and lake water quality monitoring.With the continuous development and improvement of online biological monitoring technology,the proportion of its application in water quality monitoring continues to increase and at the same time,combined with the traditional physical and chemical monitoring methods,it has gradually become an effective way to monitor and evaluate the impact of water pollution on organisms.In this study,model compounds of polycyclic aromatic hydrocarbons phenanthrene(Phe)and pyrene(Pyr)were used as test pollutants and the model organism zebrafish with small size,sensitive to pollutants,clear genetic background and high similarity to human genes were used as monitoring indicators.Biology,the behavioral intensity,circadian rhythm,oxygen consumption rate,carbon dioxide metabolic rate and ammonia nitrogen metabolic rate of zebrafish were measured,and the behavioral response and metabolism of zebrafish were comprehensively analyzed using SOM and autocorrelation analysis.The main results are as follows:1.There is a dose-effect relationship between the inhibition of Phe and Pyr on the behavioral strength of zebrafish.Under different concentrations of Phe and Pyr exposure,the average zebrafish behavioral intensity was 0.52 ± 0.13(10.2 μg/L Phe),0.42 ± 0.11(102 μg/L Phe),0.35 ± 0.1(1020 μg/L Phe),0.56 ± 0.08(7.6 μg/L Pyr),0.43 ± 0.09(76 μg/L Pyr),0.34 ± 0.12(760 μg/L Pyr),compared with the control group(0.75 ± 0.08).The behavioral intensity of zebrafish was significantly reduced(p <0.001).As the concentration increased,the behavioral intensity of zebrafish decreased significantly(p <0.05).The zebrafish’s behavioral activity law conformed to the graded behavioral response model,which was evident from the stimulation stage to the adjustment and readjustment stage.The behavior intensity of zebrafish is sensitive to pollutants and has a strong regularity,so it is suitable as an indicator for monitoring PAHs in the water environment.2.The short-term exposure of Phe and Pyr did not affect the circadian rhythm of zebrafish.The behavioral intensity of zebrafish was significantly different in different photoperiods(p <0.001).In the control group,the behavioral intensity in the light phase(0.8 ± 0.06)was higher than that in the dark phase(0.68 ± 0.06).When exposed to Phe and Pyr for 8 days,there was a similar difference in the behavioral intensity of zebrafish.Through SOM and autocorrelation analysis,the behavioral intensity of zebrafish showed a trend of increase during the days and decrease during the nights within 24 hours,and showed periodic changes during the exposure period.This can provide a new evaluation index for evaluating the ecotoxicology and health risks of PAHs in the water environment.3.Phe and Pyr had inhibitory effects on the oxygen consumption rate and carbon dioxide metabolism rate of zebrafish,but a promotion effects on the ammonia nitrogen metabolism rate.The oxygen consumption rates of zebrafish exposed to Phe and Pyr were 243.78 ± 72.68 mg/kg/h and 268.52 ± 66.80 mg/kg/h,which were significantly reduced compared with the control group(582.09 mg/kg/h)(p < 0.001).The carbon dioxide metabolic rate of zebrafish under different treatments also had significant differences(p <0.01),which were 242.01 ± 73.54 mg/kg/h(control group),187.33 ± 87.42 mg/kg/h(1020 μg/L Phe)and 203.52 ± 72.17 mg/kg/h(760 μg/L Pyr).Phe and Pyr significantly promoted the ammonia nitrogen metabolism rate of zebrafish(p <0.001),increasing from 309.29 ± 37.34 mg/kg/h(control group)to 530.07 ± 57.37 mg/kg/h(1020 μg/L Phe)and 506.80 ± 60.62 mg/kg/h(760 μg/L Pyr).The three indicators of zebrafish metabolism were significantly different between day and night(p <0.001),and autocorrelation analysis showed that it was also in a circadian rhythm pattern.Oxygen consumption rate and ammonia-nitrogen metabolism rate of zebrafish are more sensitive to pollutants and are suitable for monitoring indicators at the early stage of pollution.Carbon dioxide metabolic rate is suitable for monitoring the increase in pollution and the accumulation and amplification effect of pollutants in organisms.4.Phe and Pyr caused a sharp increase in the respiratory entropy and ammonia entropy of the zebrafish.The respiratory entropy and ammonia entropy of the zebrafish in the control group varied within the range of 0.05-0.48 and 0.19-1.91,and remained stable for 168 h.Under the exposure of Phe and Pyr,the respiratory entropy of zebrafish changed greatly and was higher than that of the control group,from 0.09 to 0.80 and from 0.12 to 0.82,respectively;the change of ammonia entropy of zebrafish was more severe and higher than the control group,from 0.85 to 9.00 and from 0.59 to 7.13,respectively.Respiratory entropy,as a comprehensive indicator of oxygen consumption rate and carbon dioxide metabolic rate,more clearly and intuitively reflects the inhibition of phe and pyr on zebrafish respiration.Ammonia entropy can comprehensively reflect the promotion of zebrafish metabolism.In summary,by monitoring the behavioral intensity and metabolic indicators of zebrafish,the physiological state of the organism can be continuously evaluated,and the degree of pollution of the water environment can be reflected in a timely manner.Combined with the circadian rhythm of the organism,the toxicologi cal evaluation of aquatic organisms and human health risks can be achieved.The effects of Phe and Pyr on zebrafish behavioral response and metabolism will provide a theoretical basis for the future development of online aquatic monitoring technology to monitor PAHs in the environment. |
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