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Heavy metal distribution in aquatic ecosystems can be influenced by a variety of factors. In this study, the spatial distribution and seasonal variation of heavy metals (Cd, Ni, Cu, Zn, Cr, and Pb) in lake water and sediments of different lake zones of a large, shallow, eutrophic freshwater lake, Taihu Lake, were investigated. Metal concentrations in the river water, bloom assemblages, and macrophyte materials were also determined. The results demonstrated that metal distribution in Taihu Lake showed distinct patterns in different seasons. Metal concentrations in rivers around Taihu Lake showed some peaks that may contribute to the elevated metal concentrations in lake water and sediments. However, the metal concentrations in the river water did not fluctuate significantly with months (March, July, and December). The dissolved metal concentrations in the phytoplankton-dominated zone of the lake were significantly higher than those in the macrophyte-dominated lake zone in summer, which could be attributed to the different dominated primary producers in the two lake zones. Statistical analysis results demonstrated that the dissolved metal concentrations were positively correlated with water turbidity for all metals in July. However, the positive correlations disappeared for most metals of March and December samples. The results of this study could provide useful information for further understanding of the transportation and fates of heavy metals in different freshwater lake ecosystems.
We investigated the effects of nutrient levels on the abundance and diversity of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB), seven surface sediment samples from small reservoirs at different nutrient levels were collected from the eastern, central, and western parts of Huashan watershed in Chuzhou, Anhui Province to determine the abundance and community composition of AOA and AOB. The results showed that the abundance of bacterial amoA gene (1.85×107 to 2.86×108 g/dry sediment) was higher than that of archaeal amoA gene (1.25×105 to 1.23×106 g/dry sediment) in all sediment samples. The abundance of the archaeal amoA gene exhibited significant positive correlations with total nitrogen concentrations, whereas the abundance of bacterial amoA gene showed significantly negative correlation with pH. Archaeal amoA gene sequences included Nitrososphaera and Nitrosopumilus clusters and the majority of Nitrosospira and Nitrosomonas oligotropha lineages.
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