Bioaccumulation of 35 metal(loid)s in organs of a freshwater mussel (Hyriopsis cumingii) and environmental implications in Poyang Lake, China.

Benthic bioaccumulation of hazardous materials has been a great challenge to the health of lake ecosystems. As representative benthic macroinvertebrates, freshwater mussels and their accumulation characteristics have been regarded as effective indicators for assessing potential risks induced by sedimentary metal(loid)s in lakes. Here we profile organ-specific accumulation of 35 metal(loid)s in a freshwater mussel (Hyriopsis cumingii) and their correlations to metal speciation in sediments of Poyang Lake, the largest lake of China. Significant organ-specific characteristics of metal accumulation were found in gills, though higher thallium (Tl) and selenium (Se) were found in the hepatopancreas, and greater arsenic (As) mostly accumulated in gonads. Pearson correlation analysis revealed that the bioaccumulation of silver (Ag), cobalt (Co), and rare earth elements (ΣREE) in gills and As in gonads were closely associated with those in bioavailable fraction of sediments. Based on the biochemical analysis in the major organs, gills exhibited the highest enzymatic activity compared with hepatopancreas and gonads. Sedimentary metals, particularly for available Ag, Co, and ΣREE, play key roles in causing lipid peroxidation in gills and significantly promote the activities of superoxide dismutase (SOD)/glutathione reductase (GR), while many metals (e.g., cadmium, manganese, Se) inhibit the glutathione (GSH) content in gonads and hepatopancreas. Our study indicates a high physiological sensitivity of mussels to these target metals, which highlights the significance of organ-specific accumulation of metal(loid)s in understanding the potential ecological risks of sedimentary metal(loid)s in lake ecosystems.

Comparison of bacterial and archaeal communities in two fertilizer doses and soil compartments under continuous cultivation system of garlic.

Soil microbial communities are affected by interactions between agricultural management (e.g., fertilizer) and soil compartment, but few studies have considered combinations of these factors. We compared the microbial abundance, diversity and community structure in two fertilizer dose (high vs. low NPK) and soil compartment (rhizosphere vs. bulk soils) under 6-year fertilization regimes in a continuous garlic cropping system in China. The soil contents of NO3- and available K were significantly higher in bulk soil in the high-NPK. The 16S rRNA gene-based bacterial and archaeal abundances were positively affected by both the fertilizer dose and soil compartment, and were higher in the high-NPK fertilization and rhizosphere samples. High-NPK fertilization increased the Shannon index and decreased bacterial and archaeal richness, whereas the evenness was marginally positively affected by both the fertilizer dose and soil compartment. Soil compartment exerted a greater effect on the bacterial and archaeal community structure than did the fertilization dose, as demonstrated by both the nonmetric multidimensional scaling and redundancy analysis results. We found that rhizosphere effects significantly distinguished 12 dominant classes of bacterial and archaeal communities, whereas the fertilizer dose significantly identified four dominant classes. In particular, a Linear Effect Size analysis showed that some taxa, including Alphaproteobacteria, Rhizobiales, Xanthomonadaceae and Flavobacterium, were enriched in the garlic rhizosphere of the high-NPK fertilizer samples. Overall, the fertilizer dose interacted with soil compartment to shape the bacterial and archaeal community composition, abundance, and biodiversity in the garlic rhizosphere. These results provide an important basis for further understanding adaptive garlic-microbe feedback, reframing roots as a significant moderating influence in agricultural management and shaping the microbial community.

[Spatio-temporal distribution of TN and TP in water and evaluation of eutrophic state of Lake Nansi].

Based on the seasonally investigating data from Lake Nansi during 2010 to 2011, the spatial and temporal distribution characteristics of total nitrogen (TN) and total phosphorus (TP) in water were analyzed, and the trophic state was also assessed. The results showed that the average concentrations of TN and TP were 2.617 mg x L(-1) and 0.110 mg x L(-1) respectively. The spatial variations of TN and TP in water were significantly different in four lake regions with the highest value of two parameters (3.830 mg x L(-1) and 0.192 mg x L(-1) respectively) were all found in Lake Nanyang while the lowest value in Lake Dushan (2.106 mg x L(-1)) and Lake Weishan (0.067 mg x L(-1)) respectively. Seasonally, the concentrations of TN in Lake Nansi had no significant difference, but the concentrations of TN in summer (2.805 mg x L(-1)) and spring (3.049 mg x L(-1)) were obviously higher than that in autumn (2.160 mg x L(-1)) and winter (2.452 mg x L(-1)), and that in four lake regions showed no uniform variation trends. While the seasonal change of the concentrations of TP in water were significantly different not only in Lake Nansi but also in its four lake regions, the variation trends were uniform with summer > spring > autumn > winter. Generally, the water quality of Lake Nansi has reached light eutrophication, among which, Lake Nanyang was in middle eutrophic state, while other three lake regions were in light eutrophic state. Integrated analysis indicted that external pollution was still the main influence factors of water quality in Lake Nansi, meanwhile, the pollution caused by pen fish culture was urgent for the control of non-point pollution sources.