We evaluated the level of heavy metal pollution in ten species of teleosts from the rare and endemic fishes nature reserve in the upper reaches of the Yangtze River in 2008–2009 using atomic absorption spectropho-tometry and atomic spectrophotofluorimetry.The mean muscle concentrations of heavy metals(Cu,Zn,Pb,Cd,Hg,and As) in the ten species were within the range of 0.39-1.17 mg/kg,29.83-38.68 mg/kg,0.03-0.64 mg/kg,0.015-0.042 mg/kg,0.015-0.074 mg/kg,and 0.031-0.077 mg/kg(wet weight),respectively.The heavy metal concentrations were below the tolerance limit levels established by the ministry of health of China,with the ex-ception of Pb in S.skneri.The concentrations of Pb were higher than the acceptable values for human consumption designated by FAO in six of the ten fish species.Our results suggest that heavy metal concentrations were higher in carnivorous species than in omnivorous fish.The heavy metals pollution index in the muscle of fishes was 0.5.We found no evidence of appreciable pollution in fishes from this study area.Our results provide insight into the health of fish resources in this area and can be used for decision-making regarding environmental management and the protection of endangered species.
The synergistic mechanism of a mixture of chlorpyrifos and emamectin benzoate on the larvae of brown rice planthopper(Nilapavata lugens) was studied by the analysis of interaction between chlorpyrifos and emamectin benzoate on target and Detoxicating enzyme.The result showed that the joint action of chlorpyrifos and emamectin benzoate to acety1cholinesterase(AChE),carboxy1esterase(CarE) and Glutathione-S-ransferase were stronger than independence.Taking chlorpyrifos as standard,the relative toxicity of emamectin benzoate were 0.76,1.52 and 0.75 to AChE,CarE,and Glutathione-S-ransferase respectively.However,the joint relativetoxicity of emamectin benzoate and chlorpyrifos were 10.41,11.68 and 7.28.Graphic analysis on the toxicokinetic mode of action on the acety1cholinesterase of joint treatment indicated that the mixture of chlorpyrifos and emamectin benzoate inhibited the enzyme competitively
Sediment bacterial communities are decisive drivers of nutrient cycling processes in aquaculture ecosystems and are readily affected by surrounding environmental factors. However, the knowledge of sediment nutrient accumulations and bacterial community structure is limited in the emerging polyculture systems. Herein, we investigated the profiles of sediment properties and bacterial communities in six typical polyculture ponds and primarily explored the influence of total nitrogen and phosphorus on the bacterial species and diversity. In almost all sediment samples, Proteobacteria, Chloroflexi, and Bacteroides were the dominant species at the phylum level, and the five most abundant bacterial genera were Sulfurovum , Woeseia , Ilumatobacter , Robiginitalea , and Cyanobium_PCC-6307 . A clear different bacterial community was observed with the most dominant bacterial phylum Firmicutes and the lowest bacterial diversity in TZ1 pond sediment; meanwhile, the TZ1 pond also showed the highest TN and TP concentrations. Notably, sediments from WZ1 and WZ2 ponds in low-latitude regions exhibited higher bacterial richness and diversity. Based on Pearson’s correlation analysis, bacterial α-diversity indices showed significant negative correlation with sediment TP content, and TN content contributed the most to the abundance of sediment dominant bacterial genus, indicating that the bacterial community is highly associated with sediment nutrient concentrations. Moreover, co-occurrence network analysis further revealed some keystone taxa that exhibited high correlations with other bacterial species, especially the high-abundance genus Robiginitalea bridging a large number of connections. Compared to traditional mono-mariculture pattern, our study provided direct evidence of lower nutrient loadings and different bacterial communities in the polyculture ponds. This could assist polyculture practitioners in developing effective strategies for detailed nutritional management.
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