青藏高原湿地植物轻金属元素含量特征及其与环境因素的关系研究

以青藏高原湿地植物为研究对象,通过对青藏高原35个采样点的野外调查采样,对青藏高原湿地植物8种轻金属元素(Al、Mg、Ca、Sr、Ba、K、Na、Li)含量的特征及其与环境因素的关系进行分析。结果显示,不同湿地植物对不同轻金属元素的富集能力存在差异。轻金属元素在湿地植物体内的平均含量依次排序为:Li相似文献   

Ecological Risk Assessment of Organochlorine Pesticides in Surface Waters of Lake Taihu,China

The residues of organochlorine pesticides (OCPs) in surface waters from Meiliang Bay, Gonghu Bay, and Xukou Bay of Lake Taihu, China, were investigated, and their ecological risks were assessed using the risk quotient method and probabilistic risk assessment. Environmental concentrations of OCPs in surface water of these bays were relatively lower compared with other rivers or lakes in China. Calculation of risk quotient associated with taxonomic groups indicates moderate ecological risks from OCPs for crustaceans and insects in these bays, while the ecological risks were low for fish and negligible for phytoplankton. The ecological risk quotients associated with individual OCPs were lower than 0.01 in these bays, suggesting a negligible risk to aquatic organisms. Ecological risk from α-HCH was relatively lower compared with DDTs, endosulfans, and γ-HCH. The combined ecological risks were evaluated using probabilistic risk assessment for only eight OCPs owing to a lack of available toxicity data for β-HCH and δ-HCH. The percentage of species with the potential to be at risk from mixture of OCPs was lower than the criteria of 5% in each bay, indicating that the combined ecological risks were acceptable.     

THE LAKE ST. LUCIA SYSTEM—A RESEARCH ASSESSMENT

SUMMARY

This paper assesses the research undertaken at Lake St. Lucia over the past 25 years based on over 300 documents from that period. Trends related to both time and subject matter are evident, and these are considered in relation to the gaps in our current knowledge concerning the system.

A feature evident throughout the period under consideration is that the major portion of documented material available relates to reports and contributions to workshops (77%) with only 23% from scientific publications. Contributions by these two sources to the subject group being considered for St. Lucia are markedly different with research publications dominating the biological field and reports dominating in physical aspects, catchment characteristics, man's activities, management, dredging and hydrological modelling. However, some 55% of all unpublished data related to reviews or assessments of the state of research on St. Lucia.

The importance of the scientific publications group as an indicator of the state of research into the system is considered in the light of an apparent decline in the number of completed projects being published. It is also considered in the light of the recent establishment of a co-ordinated Lake St. Lucia Research Programme, which may provide the impetus for a more concentrated and directed research effort on the Lake System.     

A CONCEPTUAL MODEL OF A SILTATION SYSTEM IN SHALLOW LAKES WITH LITTORAL VEGETATION

SUMMARY

In shallow lakes a siltation system develops when wind driven water turbulence erodes the lake floor, silt is resuspended and transported by means of waterdrift into the littoral vegetation. Here, due to the resistance of the vegetation, the turbulence is reduced and the silt deposited. Through this mechanism, the prevailing winds have a major rôle in the erosion and siltation pattern, lake morphology, vegetation pattern and in the mixing of water and nutrients from the open water and the reedswamp and vice versa. The model explains the uneven distribution of vegetation at the lakes Neusiedlersee (Austria) and Chilwa (Malawi) satisfactorily, if one assumes a positive correlation between siltation and reedswamp growth and spread.     

Conservation status of the two cryptic species of Hamatocaulis vernicosus (Bryophyta) in Sweden

Cryptic species are rarer than their combined, morphologically recognisable species. Each cryptic species may have its own habitat requirements and distribution, and each should be considered separately in biodiversity conservation. This investigation explores how well the two cryptic species of the wetland moss Hamatocaulis vernicosus (Mitt.) Hedenäs s.l., included in Annex II of the EU Habitat Directive, are safeguarded in existing protected sites in Sweden. Further, the northern distribution limit of the southern of the two cryptic species is explored. The distributions of the two cryptic species and their intraspecific variation are judged by the nuclear ITS1?+?2 and the two chloroplast markers rpl16 and trnL-trnF for a set of 89 specimens. The genetic differences between the two cryptic species are significant, but there are no differences between the protected and non-protected subsets within the respective species. The protected areas therefore represent these two species’ genetic variation well. The populations of both cryptic species appear stable, according to their genetic signals. One of the two cryptic species occurs almost throughout Sweden, whereas the other occurs only to the south of the southern limit of the southern boreal zone, except for two finds slightly further north in climatically mild areas.     

Further reading in geomicrobiology

In the wetland rhizosphere, high densities of lithotrophic Fe(II)-oxidizing bacteria (FeOB) and a favorable environment (i.e., high Fe(II) availability and microaerobic conditions) suggest that these organisms are actively contributing to the formation of Fe plaque on plant roots. We manipulated the presence/absence of an Fe(II)-oxidizing bacterium (Sideroxydans paludicola, strain BrT) in axenic hydroponic microcosms containing the roots of intact Juncus effusus (soft rush) plants to determine if FeOB affected total rates of rhizosphere Fe(II) oxidation and Fe plaque accumulation. Our experimental data highlight the importance of both FeOB and plants in influencing short-term rates of rhizosphere Fe oxidation. Over time scales ca. 1 wk, the FeOB increased Fe(II) oxidation rates by 1.3 to 1.7 times relative to FeOB-free microcosms. Across multiple experimental trials, Fe(II) oxidation rates were significantly correlated with root biomass, reflecting the importance of radial O ₂ loss in supporting rhizosphere Fe(II) oxidation. Rates of root Fe(III) plaque accumulation (time scales: 3 to 6 wk) were ～ 70 to 83% lower than expected based on the short-term Fe(II) oxidation rates and were unaffected by the presence/absence of FeOB. Decreasing rates of Fe(II) oxidation and Fe(III) plaque accumulation with increasing time scales indicate changes in rates of Fe(II) diffusion and radial O ₂ loss, shifts in the location of Fe oxide accumulation, or temporal changes in the microbial community within the microcosms. The microcosms used herein replicated many of the environmental characteristics of wetland systems and allowed us to demonstrate that FeOB can stimulate rates of Fe(II) oxidation in the wetland rhizosphere, a finding that has implications for the biogeochemical cycling of carbon, metals, and nutrients in wetland ecosystems.     

Effect of Physical Factors on Bacterial Distribution in the Jordan River Mouth Area in Israel

The Jordan River mouth is an area of complicated hydrography and variable and vulnerable ecology. It has changeable water and sediment regimes, for example, large spatial gradients of biological, chemical, physical, and hydrological characteristics. The Jordan River enters Lake Kinneret in the north and carries with it sewage from the Upper Galilee; thus the river is the major source of enteric bacteria in the lake. This research is based on theoretical analysis as well as on biological-hydrodynamical measurements along a discharging free, turbulent jet flow. Three components of velocities were recorded downstream from the exit cross-section for a distance of 700 m, and the mean streamwise velocity turbulence intensity and the turbulence scale were calculated. The measuring devices were an original three-dimensional velocity-fluctuation meter. Results of these measurements show that the Jordan River flows through the whole transect until it reaches the crest of a bar. After this, there is a separated exponential flow from the bottom and upper layers for ~100m after the bar. Fecal coliforms, Escherichia coli, and Klebsiella spp. were enumerated as colony-forming units from samples taken along the Jordan River path as it entered Lake Kinneret. Bacterial numbers were similar in surface and bottom waters in front of the bar. Behind the bar, however, there was a sharp decrease of bacterial numbers in the surface water, probably because of photooxidative stress. Despite the more protective environment of the bottom waters, the numbers here also decreased, indicating that the bar is a physical barrier for bacterial distribution. Furthermore, we found a significant effect of the flow velocity of Jordan River water on the bacterial distribution in Lake Kinneret. When the velocity is high, bacteria are distributed over a longer distance, regardless of their numbers in Jordan River mouth.     

Authigenic mineralization and detrital clay binding by freshwater biofilms: The Brahmani river,India

This study sought to understand the origin and fate of one of the bitumen mounds found on the bottom of Lake Baikal. These mounds are located at a depth of 900 m beneath oil spots detected on the surface of Lake Baikal (53° 18′24^″, 108° 23′20^″). The two mounds were sampled with a manipulator from a “MIR” deep-water manned submersible. Mature mound No. 8 was subjected to chemical and microbiological studies. Mound No. 3 was subjected only to chemical studies; we failed to perform microbiological analyses of this mound for logistic reasons. Oil spots collected from the water surface, samples of mound No. 3 and No. 8, were subjected to GC/MS analysis. The water contained aliphatic hydrocarbons with chains between C₈ and C₂₃, with the most abundant chain length being C₁₈. Mound No. 3 with the most abundant chain length being C₁₈ actively released oil droplets into the water. It contained 770 mg/g of C₁₃-C₃₂ n-alkanes, with a maximum at C₂₃ (160 mg/g). Mound No. 8 was inactive and contained 148 mg/g of aliphatic C₂₂-C₃₄ n-alkanes, with a maximum at C₂₅. Mound No. 8 also consisted of 3% inorganic matter, 48% unresolved complex mixture (UCM) and less than 1% other compounds (polyaromatic hydrocarbons, isoprenoids, carotenoids, and hopanes). The core of this sample used as inoculate, yielded Rhodococci when cultivated on oil as the only source of carbon. Cultivation of the sample on agar-containing Raymond inorganic medium with crude West Siberian oil as the only source of carbon revealed colonies of these bacteria, which all appeared identical. PCR was performed with DNA isolated from 5 colonies, using primers for 16S rRNA genes. Comparison of the sequences of the 5 PCR products over a length of 714 bp revealed that they were almost identical. Phylogenetic analysis of these homologous sequences showed that they were similar to the corresponding sequences of the genus Rhodococcus. Substrate demands, the morphology of the colonies, and SEM and TEM data confirmed that the isolates obtained could indeed be Rhodococci. All of the isolates could grow in bulk cultures with inorganic medium supplemented with crude oil. Moreover, all of the isolates degraded aliphatic hydrocarbons with lengths between C₁₁ and C₂₉. C₂₃-C₂₉ hydrocarbons were degraded completely. The isolates could grow at 4–37°C. The most unexpected finding was that of the many microorganisms capable of consuming oil, only Rhodococci exhibited this ability in the inactive bitumen mound. The possible mechanisms of how crude oil is transformed into bitumen mounds and mature bitumen are discussed.     

Ontogenetic shifts in phenotype–environment associations in Nile perch,Lates niloticus (Perciformes: Latidae) from Lake Nabugabo,Uganda

Habitat‐associated trait divergence may vary across ontogeny if there are strong size‐related shifts in selection pressures. We quantified patterns of phenotypic divergence in Nile perch (Lates niloticus) from ecologically distinct wetland edge and forest edge habitats in Lake Nabugabo, Uganda, and we compared patterns of divergence across three size classes to determine whether trends are consistent through Nile perch ontogeny. We predicted that inter‐habitat variation in biotic (e.g. vegetation structure) and abiotic (e.g. dissolved oxygen concentration) variables may create divergent selective regimes. We compared body morphology using geometric morphometrics and found substantial differences between habitats, although not all trends were consistent across size classes. The most striking aspects of divergence in small Nile perch were in mouth orientation, head size, and development of the caudal region. Medium‐sized Nile perch also showed differences in mouth orientation. Differences in large individuals were related to eye size and orientation, as well as caudal length. The observed patterns of divergence are consistent with functional morphological predictions for fish across divergent trophic regimes, high and low predation environments, and complex and simple habitats. Although this suggests adaptive divergence, the source of phenotypic variation is unknown and may reflect phenotypic plasticity and/or genetic differences. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 449–465.