油藏微生物群落结构解析

微生物采油(Microbial enhanced oil recovery,MEOR)以其费用低廉、无环境污染、施工简单、应用范围广等优点得到学者以及油田开发者的认同。油藏中的微生物类型多样且功能各异,可促进原油的开采,大幅度提高油气资源的利用率。因此分析油藏中微生物的类型和组成,了解土     

绿海龟卫星追踪报道

自2001年来,惠东港口海龟国家级自然保护区已成功地利用卫星追踪了21只海龟的洄游路线。本文利用美国卫星信号发射器(Tag)和法国Argos系统追踪3只成年雌性绿海龟。跟踪海龟"西沙"和"南沙"26d,二者均在海口市附近海域消失;"东沙"从阳江市海陵岛出发,取东南向至菲律宾,然后沿菲律宾西海岸向南,最后在巴拉望岛西侧海域逗留,共追踪111d。该试验说明港口海龟具有不同的洄游线路,偏爱沿岸的浅海洄游;洄游路线与等温线之间无显著关系;海龟洄游具有明确的目的地。建议政府相关部门采取科学策略来保护海龟。     

Phytoplankton equilibrium phases during thermal stratification in a deep subtropical reservoir

1. Equilibrium and non-equilibrium hypotheses have often been used to explain observations in community ecology. Published case studies have demonstrated that steady state phytoplankton assemblages are more likely to occur in deep lakes than in shallow mixed ones.
2. Phytoplankton seasonal succession was studied by weekly sampling in Faxinal Reservoir (S Brazil), a subtropical deep, clear, warm monomictic and slightly eutrophic reservoir. This study demonstrated an alternation of steady and non-steady state phases of phytoplankton assemblages with different dominant species during the steady states.
3. During the studied period, three steady states were identified with different dominant algal species: Anabaena crassa (Cyanobacteria), Nephrocytium sp. (green algae) and Asterionella (diatoms).
4. Each steady state in Faxinal Reservoir developed under stratified conditions of the water column according to the predictions of the disturbance concepts. Apparently, the major forces driving the development and persistence of these steady-state phases were closely related to thermal stratification and its consequences.
5. This study is the first report on development of more than one steady state within a year in a stratified water body. The development of three steady states might be the result of the relatively long stratification period in the Faxinal Reservoir and to its unique geochemical features.     

Altering the balance between bacterial production and protistan bacterivory triggers shifts in freshwater bacterial community composition

Bacterivorous protists are known to induce changes in bacterial community composition (BCC). We hypothesized that changes in BCC could be related quantitatively to a measure of grazing: the ratio of bacterial mortality to growth rate. To test this hypothesis, we analyzed time-course changes in BCC, protistan grazing rate, and bacterial production from 3 in situ studies conducted in a freshwater reservoir and three laboratory studies. In the field experiments, samples were manipulated to yield different levels of protistan bacterivory and incubated in dialysis bags. Laboratory investigations were continuous cultivation studies in which different bacterivorous protists were added to bacterial communities. BCC was assessed using 4–6 different rRNA-targeted oligonucleotide probes for community analysis. Change in BCC (Δ BCC) was estimated as the sum of changes in the proportions of the two phylogenetic groups that showed the largest shifts. Analysis of a set of 22 estimates of shifts in the ratio of grazing to production rate over periods of 48–72 h and Δ BCC showed that Δ BCC was positively and tightly correlated (r ² = 0.784) with shifts in the ratio of grazing mortality to cell production. While the nature of a shift in BCC is unpredictable, the magnitude of the change can be related to changes in the balance between bacterial production and protistan grazing. This revised version was published online in August 2006 with corrections to the Cover Date.     

Microbiological Processes in a High-Temperature Oil Field

Thermophilic sulfate-reducing bacteria (SRB) oxidizing lactate, butyrate, and C₁₂–C₁₆ n-alkanes of oil at a temperature of 90°C were isolated from samples of water and oil originating from oil reservoirs of the White Tiger high-temperature oil field (Vietnam). At the same time, no thermophiles were detected in the injected seawater, which contained mesophilic microorganisms and was the site of low-temperature processes of sulfate reduction and methanogenesis. Thermophilic SRB were also found in samples of liquid taken from various engineering reservoirs used for oil storage, treatment, and transportation. These samples also contained mesophilic SRB, methanogens, aerobic oil-oxidizing bacteria, and heterotrophs. Rates of bacterial production of hydrogen sulfide varied from 0.11 to 2069.63 at 30°C and from 1.18 to 173.86 at 70°C g S/(l day); and those of methane production, varied from 58.4 to 100 629.8 nl CH₄/(l day) (at 30°C). The sulfur isotopic compositions of sulfates contained in reservoir waters and of hydrogen sulfide of the accompanying gas indicate that bacterial sulfate reduction might be effective in the depth of the oil field.     

Control of biogenic H(2)S production with nitrite and molybdate

The effects of the metabolic inhibitors, sodium nitrite and ammonium molybdate, on production of H₂S by a pure culture of the sulfate-reducing bacterium (SRB) Desulfovibrio sp. strain Lac6 and a consortium of SRB, enriched from produced water of a Canadian oil field, were investigated. Addition of 0.1 mM nitrite or 0.024 mM molybdate at the start of growth prevented the production of H₂S by strain Lac6. With exponentially growing cultures, higher levels of inhibitors, 0.25 mM nitrite or 0.095 mM molybdate, were required to suppress the production of H₂S. Simultaneous addition of nitrite and molybdate had a synergistic effect: at time 0, 0.05 mM nitrite and 0.01 mM molybdate, whereas during the exponential phase, 0.1 mM nitrite and 0.047 mM molybdate were sufficient to stop H₂S production. With an exponentially growing consortium of SRB, enriched from produced water of the Coleville oil field, much higher levels of inhibitors, 4 mM nitrite or 0.47 mM molybdate, were needed to stop the production of H₂S. The addition of these inhibitors had no effect on the composition of the microbial community, as shown by reverse sample genome probing. The results indicate that the efficiency of inhibitors in containment of SRB depends on the composition and metabolic state of the microbial community. Journal of Industrial Microbiology & Biotechnology (2001) 26, 350–355. Received 02 August 2000/ Accepted in revised form 17 April 2001     

Distribution pattern of the dinoflagellateCeratium hirundinella (O. F. Müller) Bergh in a reservoir

Horizontal distribution of the dinoflagellateCeratium hirundinella (O. F. Müller) Bergh in the Ishitegawa Reservoir, Ehime Prefecture, Japan, was investigated. Water quality was also surveyed. It was observed that the population ofC. hirundinella exponentially decreased in number from the head of the reservoir to the dam site. Further investigation proved thatC. hirundinella initiated growth at the head of the reservoir, and later gradually expanded downstream. It was found during the period of increase in water temperature that the cell density ofC. hirundinella at the uppermost station exponentially increased.     

Relative importance of temporal and spatial heterogeneity in the zooplankton community of an artificial reservoir

Zooplankton samples were collected monthly at three stations in Ogochi Reservoir during 1980, and the temporal and horizontal variations in the density of dominant taxa were evaluated by a standard 2-way ANOVA with random effects. The analysis revealed that horizontal is greater than temporal variation in the warm water season (> 18 °C), whereas temporal variation is greater in the cold water season (< 18 °C). Horizontal heterogeneity of the zooplankton community found in the warm water season seems to be associated with differences in site-specific conditions.     

Estimating the effective clearance rate and refiltration by zebra mussels, Dreissena polymorpha, in a stratified reservoir

1. The grazing impact of zebra mussels, Dreissena polymorpha Pallas, is often evaluated by applying the individual filtration rate measured in the laboratory to the field abundance and then by comparing the total volume of water filtered with the whole lake volume. Since this approach overlooks refiltration, it overestimates the grazing impact of zebra mussels. To deal with this problem, the present authors developed an in situ method for collecting faeces and pseudofaeces to measure the actual volume of water that is cleared of suspended particles by Dreissena in a unit time under a given set of environmental conditions. This is termed the effective clearance rate (ECR). 2. The experiment was conducted in Hargus Lake, OH, U.S.A., a small thermally stratified reservoir, to test the effects of spatial aggregation, mussel density and the concentration of particulate inorganic matter (PIM) on the effective clearance rate of Dreissena. 3. Over 40 measurements, the ECR values ranged from 15.3 to 68.6 mL ind^??1 h^??1. Much of the variation can be explained by colony form, mussel density and seston concentration. The effects of these variables were all statistically significant. The average ECR for isolated individuals was higher than that for those in clumps (40.4 versus 32.8 mL ind^??1 h^??1), which is attributed to increased refiltration in the cores of the clumps. The ECR decreased with increased zebra mussel density because of intensified competition for food particles within the group. The ECR increased with increased PIM concentration in the lake water, which may be interpreted as a result of enhanced water mixing which ultimately caused increases in both sediment resuspension and particle delivery to the mussels. 4. Taking the filtration rates for a 20-mm mussel to be between 116 and 234 mL ind^??1 h^??1, based on data from the literature, the clumped mussels under the present experimental conditions would have a refiltration ratio between 3.4 and 6.9. 5. The present authors developed an areal clearance model which predicts that seston removal by the Dreissena population is limited by the particle delivery from the ambient water to the mussel bed and will reach a maximum value beyond which no further increase will occur with increased population density. 6. It is concluded that the direct grazing impact of zebra mussel on phytoplankton in thermally stratified lakes is much less effective than predicted from simple filtration rate estimation.     

Long-term variations of epilimnetic phytoplankton in an artificial reservoir during a 10-year survey

Vieux-Pré is an artificial reservoir in the north-east part of France (61 Mm³), created in 1986 for hydraulic management. The phytoplankton and several environmental parameters in the upper part of the lake were monitored at a mid-lake station, from 1988 to 1997. The specific composition of the community changed during this period, from a predominantly pennate-diatom phytoplankton (Asterionella formosa, Fragilaria crotonensis), the lake passed to dominance by a sparse, motile nanoplankton (Mallomonas akrokomos, M. caudata, Cryptomonas erosa, Chroomonas/Rhodomonas, a.o.) and then by large colonies of small-celled species (Uroglena americana, Dinobryon spp., Radiocystis geminata, Aphanothece clathrata, Coelosphaerium kuetzingianum a.o.). This paper describes the algal successions involved and shows the decisive effects of the decrease of trophic level from an eutrophic stage to an oligo-mesotrophic condition. In the beginning, externally imposed disturbances (flooding and dewatering) were frequent, while now the lake has stabilised as a deep, stratified pelagic system. Under these conditions, autogenic phytoplankton appear to dominate.