Historically as part of its national security mission, the U.S. Department of Energy's Y-12 National Security Facility in Oak Ridge, TN acquired a significant fraction of the world's supply of elemental mercury. During the 1950s and 1960s, a large amount of elemental mercury escaped confinement and is still present in the watershed surrounding the Y-12 facility. Earthworms are key components in natural food chains, providing a food source for many small mammals and important food sources for small birds. The objectives of this study were to investigate the current status of mercury distribution and speciation and determination of mercury bioavailability to native earthworms in floodplain soils of East Fork Poplar Creek (EFPC) after decades of U.S. Department of Energy's remediation. The present study clearly shows that the total mercury in a tested floodplain field of EFPC was significantly below the US Department of Energy target 400 mg Hg/kg. The major mercury form in the current floodplain soils of EFPC is mainly the non-cinnabar mercury bound form in soil silicates (4 M HNO3-extractable residual fraction). The results show strong linear relationships between mercury concentrations in native earthworms (both mature and immature groups) and the non-cinnabar mercury form. Native earthworms may be used as a potential mercury ecological bio-indicator (bio-marker) for demonstrating mercury bioavailability and ecotoxicity in the ecosystem. 相似文献
To investigate the differences in gut bacterial community of Parabramis pekinensis at different growth stages, we collected wild P. pekinensis from the Jingjiang region of the Yangtze River, and detected the intestinal microflora structure using high-throughput sequencing technology. Results show that during stage I the dominant bacteria were Proteobacteria, Actinobacteria, and Firmicutes. During stage II, the proportion of Proteobacteria and Actinobacteria decreased, while the proportion of Firmicutes and Fusobacteria increased, especially Clostridium and Cetobacteria increased significantly. During stage III, Cetobacterium had a dominant position, while the proportion of Firmicutes decreased slightly. In stage IV, the male and female fish showed obvious differences. In the female gut, the proportion of Proteobacteria increased to the first place, while Fusobacteria decreased to the second place. In the male fish, the proportion of Fusobacteria dropped to the fifth, especially that of Cetobacterium decreased significantly, and that of Verrucomicrobia increased. In stage V, the proportion of Fusobacteria increased again to the first place, while Proteobacteria did not decrease significantly in the female gut. The gut bacterial community in males changed into a structure similar to stage I. In stage VI, the gut bacterial community in both females and males changed into a structure similar to stage I. There were significant differences in the intestinal microflora structure of P. pekinensis at different gonad development stages and sexes. To some extent, the changes in intestinal microflora structure reflect the changes in the nutritional requirements of P. pekinensis.
A study on Chlamys nobilis sperm cryopreservation by a programmable freezing method was conducted under laboratory condition. Four cryoprotectant agents (dimethyl sulfoxide [DMSO], methanol [MET], propanediol[PG] and ethylene glycol [EG]) and four concentrations (5%, 10%, 20% and 30%) were evaluated for their ability to retain sperm motility, movement characteristics and fertility. Results showed that cryopreserved sperm total motility produced by DMSO and MET at 5%, 10% and 20% were higher than other cryoprotectant treatment groups (CPA groups), as well as rapid sperm percentage. The curvilinear (VCL) and straight line (VSL) velocity produced by DMSO at 5% significantly higher than other CPA groups (p < 0.05), while no significant differences were found for average path (VAP) velocity. The lateral head displacement (ALH) in all CPA groups was similar and without significant difference (p > 0.05), as well as the beat‐cross frequency (BCF). A significant higher fertilization rate was produced in DMSO than that in MET at same concentration (p < 0.05), and no significant differences were found for differing concentrations of the same cryoprotectant (p > 0.05). Overall, 5%‐20% DMSO was more suitable for Chlamys nobilis sperm programmable cryopreservation when the calcium‐free Hanks’ balanced salt solution was used as the extender, and 10°C/min from 0°C to ?80°C was used as freezing rate. The findings presented in this study will benefit conservation programs for Chlamys nobilis.相似文献