[Metagenomic Analysis of Resistance Genes in Membrane Cleaning Sludge].

Wastewater treatment plants (WWTPs) are considered important reservoirs of antibiotic resistance genes (ARGs) and function as the main sources of ARGs in the environment. Membrane bioreactors (MBRs) have been recognized as effective tools for removing ARGs in WWTPs.There are a large number of pathogens and resistance genes in colloids, particulate matter, suspended matter, and microbial metabolites in intercepted wastewater by MBR. However, the distribution characteristics of resistance genes in membrane cleaning sludge remains unclear. In this study, resistance genes of membrane cleaning sludge were analyzed using a metagenomic technique. The results showed that there were 39 phyla in the membrane cleaning sludge. Proteobacteria, Nitrospirae, and Actinobacteria were the dominant phyla. The dominant genera were Nitrospira, Pseudomonas, and Bradyrhizobium. The pathogens accounted for 10.54% of all bacteria in the sample, among which Pseudomonas had the highest abundance, accounting for 3.94%. A total of 17 types of antibiotic resistance genes and 16 types of metal resistance genes (MRGs) (15 types of single metal resistance genes and 1 types of multi-heavy metal resistance gene) were identified. Multidrug resistance genes had the highest abundance, accounting for 49.08%. Multi-heavy metal resistance genes were the most abundant, accounting for 34.58%. The copper resistance genes were the most abundant of the single metal resistance genes, accounting for 19.99%. The most important functional pathway of microbial community in the membrane cleaning sludge was metabolic related, and many genes identified were related to human diseases. The numbers of genes related to bacterial resistance and bacterial infectious diseases were the largest, accounting for 34.50% and 16.62%, respectively. These results indicate that there were abundant ARGs, MRGs, and pathogens in the membrane cleaning sludge, which has potential environmental health risks. It is necessary to strengthen the control of ARGs, MRGs, and pathogens in membrane cleaning sludge to provide guidance for selecting appropriate technologies for effectively removing ARGs, MRGs, and pathogens.

[Temporal and Spatial Variation of Zooplankton Community Structure and Its Relationship with Environmental Factors in Dianshan Lake, Shanghai].

Dianshan Lake, a subtropical shallow lake, is the largest freshwater body located in Shanghai. To reveal the temporal and spatial variation of zooplankton community structure and its relationships with environmental factors, monthly data of zooplankton and phytoplankton content and associated physicochemical parameters for 2017 were analyzed using multivariate regression trees (MRT) and principal coordinates analysis (PCoA). The results indicated that there were significant seasonal differences in the community structure of zooplankton (P<0.05). However, spatial variations were significant only in spring and summer (P<0.05). The results indicated that water temperature (WT), chlorophyll-a (Chla), ammonia nitrogen, and cyanobacteria were the key driving factors in the observed spatial and temporal variations in the zooplankton community structure. The MRT analysis illustrated that zooplankton community structure varied strongly across four groups, including spring (13.07℃ ≤ WT<19.57℃), summer (WT ≥ 19.57℃, Chla ≥ 9.03 µg·L-1), autumn (WT ≥ 19.57℃, Chla<9.03 µg·L-1), and winter (WT<13.07℃). In addition, three distinct regions were identified by the cluster analysis. The MRT analysis illustrated that the zooplankton community structure was distinct between samples with relatively lower (<1.11 mg·L-1) and higher concentrations (≥ 1.11 mg·L-1) of ammonia nitrogen in spring. Furthermore, cyanobacteria were identified as a major stressor on zooplankton in summer. These observations further show that that zooplankton community structure in area I (with a cyanobacterial biomass of ≥ 2.58 mg·L-1) was significantly different from other regions (with a cyanobacterial biomass of <2.58 mg·L-1).

[Effects of Nutrient Addition on the Growth and Competition of Bloom Forming Cyanobacterium Chrysosporum ovalisporum: An In-situ Experiment].

An in-situ mesocosm experiment was conducted to study the growth dynamic of Chrysosporum ovalisporum and the other phytoplankton organisms under accelerated eutrophication conditions by using 39 buckets (100 L) in Lake Dishui, Shanghai. The results showed that the growth of both filamentous cyanobacteria (C. ovalisporum) and green algae were promoted with nutrient enrichment. The increase in the algal biomass rate in N plus P addition treatments was significantly higher than in treatments with N or P alone (P<0.05). Although the increasing biomass rate with P addition alone was higher than with N alone, there was no statistically significant difference (P>0.05). The relevant abundance of C. ovalisporum showed a significantly decreasing trend with N addition treatments and N plus P additions treatments (P<0.05), although it was slightly increased with the treatments with P alone (P>0.05). Nutrient addition could significantly improve the growth of small sized algae organisms (Chroococcus spp., Coelastrum spp., Chlorella spp., Tetraedron spp., and Scenedesmus spp.) rather than C. ovalisporum in all treatments (P<0.05). The small sized green algae overcoming C. ovalisporum indicated that small sized algae were more favored by hyper-eutrophicated, high water temperature and relatively undisturbed conditions. This is because small sized algal organisms have higher metabolic and growth rates compared to other sized algae, especially in stationary water regimens and high, light density conditions. We foresee that the small sized algae, Chlorophyte, dominating the small hyper-eutrophic aquatic system may be a potential succession pattern in the high water temperature seasons.