To understand the genetic diversity and population changes in cyanophages in the coastal waters of Shantou,northeast South China Sea,we used the capsid assembly protein gene g 20 as a marker of the abundance and phylogeny of natural cyanomyovirus communities. The abundance of total viruses,heterotrophic bacteria,and picophytoplankton in the coastal waters was monitored with flow cytometry. Hydrological parameters(NO ˉ 3,NO ˉ 2,NH 3,soluble reactive phosphorus,total dissolved nitrogen,total dissolved phosphorus,dissolved oxygen,chemical oxygen demand,temperature,salinity,and chlorophyll a concentration) and microbial abundance(total viruses,total bacteria,P rochlorococcus,Synechococcus,and eukaryotes) were measured in the upper and lower layers at four sampling sites in the research area. In the direct viral counts,cyanomyoviruses accounted for 1.92% to 10% of the total viral community. A phylogenetic analysis showed that the g 20 sequences in the Shantou coastal waters were very diverse,distributed in eight distinct operational taxonomic units,including the newly formed Cluster W. The g 20 gene copies inferred from real time PCR assay indicated that cyanomyoviruses were correlated significantly with the heterotrophic bacteria numbers and the nitrate and chlorophyll a concentrations. These results suggest that cyanomyoviruses are ubiquitous and are an abundant component of the virioplankton in Shantou coastal waters. 相似文献
The marine–estuarine polychaete Capitella is an indicator of organic pollution and plays important roles in sewage waste cycling. The antidepressant fluoxetine can be accumulated in streams and sewage effluents and it could pose a hazard to infauna. Effects of fluoxetine on feeding and growth of Capitella teleta were investigated through the exposure to 0, 0.001, 0.03, 0.3 and 3.3 μg/g dry weight sediment-spiked fluoxetine during 18 days. No effects of fluoxetine concentrations were observed on egestion rates, body weight and size-specific egestion rates. Fluoxetine favoured the occurrence of males with abnormal genital spines. This suggests that fluoxetine can have important reproductive implications. Further studies are recommended to assess potential detrimental effects on benthic infauna inhabiting close to sewage treatment plants. 相似文献
Immersed tube tunnels are usually placed on soft soil layers in cross-sea tunnelling engineering. Owing to the influence of stratum conditions and slope design, the longitudinal distribution of substratum layers is generally uneven. Thus, the inhomogeneous deformation of the element-joint becomes the key factor in the failure of the immersed tube tunnel. Therefore, a corresponding calculation method for joint deformation is needed to explore the deformation law of immersed tube tunnels. By constructing a three-section immersed tube tunnel analysis model (TTM), the relationship between the two types of deformation of the immersed tube tunnel structure in a longitudinal nonuniform soft soil foundation is described, and the deformation characteristics of the immersed structure under different boundaries are discussed. Based on the mechanical behaviour of the joint and foundation, according to the Timoshenko beam on the Vlasov two-parameter foundation (VTM), considering the tidal cyclic load during the operation and maintenance period, an example analysis is given. Moreover, the deformation characteristics and development trend of the immersed tube tunnel under the influence of different soil layers are discussed. The obtained results have a certain guiding significance for the deformation calculation of immersed tube tunnels.
Upper ocean responses to the passage of sequential tropical cyclones over the northwestern South China Sea(SCS) in 2011 were investigated using satellite remote sensing data,Argo reanalysis data,and an array of mooring data.We found that the sea surface low temperature region lasted for more than 38 days and two phytoplankton blooms occurred after the passage of sequential tropical cyclones.The upper ocean cooling reached 2-5℃ with a right-side bias was observed along the typhoon track to about 200 km.The maintenance of low temperature region and the two phytoplankton blooms were mainly driven by upwelling and near-inertial turbulence mixing induced by the sequential tropical cyclones.The first phytoplankton bloom appeared on the 7~(th) day after the passage of the three tropical cyclones,and the chlorophyll-a(chl-a) concentration increased by 226%,which may be mainly driven by typhoons induced upwelling.The second phytoplankton bloom occurred on the 30~(th) day,the chl-a concentration increased by290%.Further analysis suggested that only the typhoons with similar characteristics as Nesat and Nalgae can induce strong near-inertial oscillation(NIO).Strong turbulent mixing associated with the near-inertial baroclinic shear instability lasted for 26 days.The measured mean eddy diffusivity in the upper ocean was above 10~(-4) m~2/s after typhoon Nesat.Enhancement of the turbulent mixing in the upper ocean helped to transport nutrient-rich cold waters from the deep layer to the euphotic layer,and is a maj or mechanism for the long-term maintenance of low temperature region as well as the second phytoplankton bloom. 相似文献
The siliceous skeletal remains of diatoms are a primary component of sediments, covering vast areas of the sea floor. We used high performance liquid chromatography–electrospray ionization–tandem mass spectrometry (HPLC–ESI–MSn) under high resolution time-of-flight MS (TOF-MS) conditions, as well as nuclear magnetic resonance spectroscopy (NMR) and Fourier transform infrared spectroscopy (FTIR), to investigate the distribution and molecular diversity of long chain polyamines (LCPAs) entrapped in sedimentary diatom biosilica in sediments from the Indian sector of the Southern Ocean, the Bering Sea and the Northeast Pacific. This revealed the existence of complex polyamine populations with both known and unknown structural features, including the presence of ketone and carboxylic acid groups in the LCPA backbone, functional groups that likely modulate the silica precipitating properties of LCPAs in the environment and which may constitute points of initial silica deposition (Wallace, A.F., De Yoreso, J.J., Dove, P.M., 2009. Kinetics of silica nucleation on carboxy- and amine-terminated surfaces: insights for biomineralization. Journal of the American Chemical Society 131, 5244–5250). Although various LCPA species overlapped between samples (putrescine-based LCPAs with various degrees of methylation and N-methyl propylamine repeat units were ubiquitous in all samples), clear regional differences were shown in composition and structural characteristics, likely reflecting the various diatom species contributing to the total LCPA pool for each sedimentary environment. We further show, using scanning electron microscopy and energy dispersive X-ray analysis (SEM–EDX) that LCPAs purified from diatom skeletal remains rapidly re-direct the formation of silica nanospheres in vitro, and become embedded in the precipitated silicified matrix, forming an LCPA–silica composite material. The results show that aliphatic polyamines produced by diatoms for morphogenesis of their cell walls are widespread in sediments where the fossil frustules are preserved. These newly assigned components constitute useful biological markers of diatom input to sediments. 相似文献
Acta Geotechnica - This paper proposes a framework to identify geological characteristics (GC) based on borehole data and operational data during shield tunnelling using a fuzzy C-means... 相似文献