共查询到20条相似文献,搜索用时 31 毫秒
1.
Glen A. Smith John D. Davis Ann M. Muscat Richard L. Moe David C. White 《Polar Biology》1989,9(8):517-524
Summary Benthic microbial communities of the Arthur Harbor area were described by analysis of their cell membrane phospholipid ester-linked fatty acids (PELFA) and metabolic rates. Analysis revealed a biomass averaging 6 nM (phospholipid) or 3.5×108 cells per gram dry weight (gdw) of sediment for the four sites. Only slight biomass differences were detected between the four peninsula sites. All Arthur Harbor sites were determined to have a biomass similar to the lowest amount reported for a previously described McMurdo Sound site at New Harbor. Community structure based on signature phospholipids indicated only slight differences between the four peninsula sites with greater relative amounts of diatom marker lipids at a deeper site. Bacterial biomarker lipids were also determined in relatively equal proportions for the four Arthur Harbor sites with only one site indicating a somewhat decreased proportion. Metabolic rates of sodium [14C]-acetate and methyl [3H]-thymidine incorporation into lipid and bacterial DNA respectively also indicated only slight relative differences in microbial communities of Arthur Harbor study sites. Lipid metabolism (14C-acetate) ranged between 6 and 12 (x104) DPM/g/h for the four sites with 8 being the average. Bacterial (excluding sulfate-reducing bacteria (SRB)) cell divisions per g per h indicated increased rates at a deeper site with 14×105, compared to the average (5×105) for the three remaining sites. Average estimated total bacterial (excluding SRB's) community turnover was on the order of 0.6%/h for the four sites. Metabolic rate comparisons of Arthur Harbor with those of previously determined McMurdo Sound indicated a somewhat increased lipid metabolism and an order of magnitude greater bacterial cell division rate at Arthur Harbor.This paper is part 4 in the series: Microbial Ecology in Antarctic Sea-Ice and Benthic Communities 相似文献
2.
Daniel M. Alongi 《Microbial ecology》1988,15(1):59-79
Bacterial productivity (3H-thymidine incorporation into DNA) and intertidal microbenthic communities were examined within five mangrove estuaries along the tropical northeastern coast of Australia. Bacteria in mangrove surface sediments (0–2 cm depth) were enumerated by epifluorescence microscopy and were more abundant (mean and range: 1.1(0.02–3.6)×1011 cells·g DW–1) and productive (mean: 1.6 gC·m–2· d–1) compared to bacterial populations in most other benthic environments. Specific growth rates (¯x=1.1) ranged from 0.2–5.5 d–1, with highest rates of growth in austral spring and summer. Highest bacterial numbers occurred in winter (June–August) in estuaries along the Cape York peninsula north of Hinchinbrook Island and were significantly different among intertidal zones and estuaries. Protozoa (105–106·m–2, pheopigments (0.0–24.1g·gDW–1) and bacterial productivity (0.2–5.1 gC·m–2·d–1) exhibited significant seasonality with maximum densities and production in austral spring and summer. Algal biomass (chlorophylla) was low (mean: 1.6g·gDW–1) compared to other intertidal sediments because of low light intensity under the dense forest canopy, especially in the mid-intertidal zone. Partial correlation analysis and a study of possible tidal effects suggest that microbial biomass and bacterial growth in tropical intertidal sediments are regulated primarily by physicochemical factors and by tidal flushing and exposure. High microbial biomass and very high rates of bacterial productivity coupled with low densities of meiofaunal and macroinfaunal consumers observed in earlier studies suggest that microbes may be a sink for carbon in intertidal sediments of tropical mangrove estuaries. 相似文献
3.
Gary Gibson Pamela Nielsen Victoria Mykytyn Ken Carlson John Blass 《Neurochemical research》1989,14(1):17-24
To further elucidate the molecular basis of the selective damage to various brain regions by thiamin deficiency, changes in enzymatic activities were compared to carbohydrate flux through various pathways from vulnerable (mammillary bodies and inferior colliculi) and nonvulnerable (cochlear nuclei) regions after 11 or 14 days of pyrithiamin-induced thiamin deficiency. After 11 days,large decreases (–43 to –59%) in transketolase (TK) occurred in all 3 regions; 2-ketoglutarate dehydrogenase (KGDHC) declined (–45%), but only in mammillary bodies; pyruvate dehydrogenase (PDHC) was unaffected. By day 14, TK remained reduced by 58%–66%; KGDHC was now reduced in all regions (–48 to –55%); PDHC was also reduced (–32%), but only in the mammillary bodies. Thus, the enzyme changes did not parallel the pathological vulnerability of these regions to thiamin deficiency.14CO2 production from14C-glucose labeled in various positions was utilized to assess metabolic flux. After 14 days, CO2 production in the vulnerable regions declined severely (–46 to 70%) and approximately twice as much as those in the cochlear nucleus. Also by day 14, the ratio of enzymatic activity to metabolic flux increased as much as 56% in the vulnerable regions, but decreased 18 to 30% in the cochlear nuclei. These differences reflect a greater decrease in flux than enzyme activities in the two vulnerable regions. Thus, selective cellular responses to thiamin deficiency can be demonstrated ex vivo, and these changes can be directly related to alterations in metabolic flux. Since they cannot be related to enzymatic alterations in the three regions, factors other than decreases in the activity of these TPP-dependent enzymes must underlie selective vulnerability in this model of thiamin deficiency.Abbreviations KGDHC
2-ketoglutarate dehydrogenase complex EC 1.2.4.2., EC 2.3.1.61, EC 1.6.4.3.
- PDHC
pyruvate dehydrogenase complex EC 1.2.4.2., EC 2.3.1.12, EC 1.6.4.3
- TK
transketolase (EC 2.2.1.1)
- TPP
thiamin pyrophosphate 相似文献
4.
D. M. Alongi 《Oecologia》1994,98(3-4):320-327
Benthic oxygen consumption and primary production were measured using the bell jar technique in deltaic and fringing mangrove forests of tropical northeastern Australia. In a deltaic forest, rates of sediment respiration ranged from 197 to 1645 mol O2 m–2 h–1 (mean=836), but did not vary significantly with season or intertidal zone. Gross primary production varied among intertidal zones and seasons, ranging from –281 to 1413 mol O2 m–2 h–1 (mean=258). Upon tidal exposure, rates of gross primary production increased, but respiration rates did not change significantly. In a fringing mangrove forest, benthic respiration and gross primary production exhibited strong seasonality. In both forests, rates of oxygen consumption and production were low compared to salt marshes, but equivalent to rates in other mangrove forests. The production:respiration (P/R) ratio varied greatly over space and time (range:–0.61 to 1.76), but most values were «1 with a mean of 0.15, indicating net heterotrophy. On a bare creek bank and a sandflat, rates of gross primary production and P/R ratios were generally higher than in the adjacent mangroves. Low microalgal standing stocks, low light intensity under the canopy, and differences in gross primary production between mangroves and tidal flats, and with tidal status, indicate that benthic microalgae are light-limited and a minor contributor to primary productivity in these tropical mangrove forests. 相似文献
5.
John G. Farmer 《Hydrobiologia》1994,290(1-3):39-49
The chemical record in Loch Lomond sediments deposited since the end of the last Ice Age provides evidence of the Flandrian marine transgression some 5500–7000 14C years B.P., sedimentation rates and the influence of man's local activities, environmental pollution and its sources since the onset of the Industrial Revolution, and of elemental mobility linked with the reduction-diffusion-oxidation cycle of early sedimentary diagenesis. Information derived from vertical profiles of halogen elements bromine and iodine, radionuclides 14C and 210Pb, heavy metals lead, zinc, and cadmium, stable lead isotopes 206Pb and 207Pb, and redox-sensitive elements manganese, iron and arsenic is reviewed and assessed. 相似文献
6.
Ontogenetic changes in food intake and digestion rate of the herbivorous marine iguana (Amblyrhynchus cristatus,Bell) 总被引:1,自引:0,他引:1
Young reptiles have higher relative energy demands than adults, but the proposed ontogenetic changes in diet to fulfil these demands were not found in the algae-eating Galápagos marine iguanas on Santa Fé. Feeding and digestion rates were investigated to analyse how young achieve higher energy intake. Daily food intake of free ranging marine iguana hatchlings (6–11 months old) was about one third that of adults, but relative intake (g dry mass · g–1 wet mass · day–1) was four times higher in the hatchlings. During feeding experiments, relative daily food intake of hatchling marine iguanas was approximately three times higher than that of adults (0.042 vs 0.013 g dry mass · g–0.8 wet mass · day–1), and mean gut passage time was two times shorter (5 vs 10 days). The hatchlings also maintained high body temperatures (36.7° C) even under relatively cool day-time air temperatures of 32° C. Apparent digestibility of algal food measured both during feeding trials and by Mn2+ AAS (atomic absorption spectrometry) for free-ranging iguanas was 70%, independent of body size and temperature. The red algae prevailing in the diet were high in protein (30% dry mass) and energy (12.1 kJ/g dry mass). Diving iguanas had higher rates of energy intake than intertidal foragers, but daily intake was less. Maintenance of high body temperature enabled hatchlings to achieve high digestion rates and, combined with high relative intake, thus achieve sufficient energy intake for rapid growth despite higher mass specific metabolic rates. Estimates of biomass of marine iguanas and their algal food are given for a section of coastline on Santa Fé. 相似文献
7.
Carbon and nitrogen cycling in intertidal mud flat sediments in the Scheldt Estuary was studied using measurements of carbon dioxide, methane and nitrous oxide emission rates and pore-water profiles of CO2, ammonium and nitrate. A comparison between chamber measured carbon dioxide fluxes and those based on CO2 pore-water gradients using Fick's First law indicates that apparent diffusion coefficients are 2 to 28 times higher than bulk sediment diffusion coefficients based on molecular diffusion. Seasonal changes in gaseous carbon fluxes or CO2 pore water concentrations cannot be used directly, or in a simple way, to determine seasonal rates of mineralization, because of marked seasonal changes in pore-water storage and exchange parameters.The annual amount of carbon delivered to the sediment is 42 mol m–2, of which about 42% becomes buried, the remaining being emitted as methane (7%) or carbon dioxide (50%). Each year about 2.6 mol N m–2 of particulate nitrogen reaches the sediment; 1.1 mol m–2 is buried and 1.6 mol m–2 is mineralized to ammonium. Only 0.42 mol m–2 yr–1 of the ammonium produced escapes from the sediments, the remaining being first nitrified (1.2 mol m–2 yr–1) and then denitrified (1.7 mol m–2 yr–1). Simple calculations indicate that intertidal sediments may account for about 14% and 30% of the total estuarine retention of nitrogen and carbon, respectively. 相似文献
8.
Tom Spencer 《Coral reefs (Online)》1985,4(2):59-70
Direct measurements of surface lowering, using the micro-erosion meter technique, have been obtained from Pleistocene and Tertiary limestones in subtidal and intertidal environments on Grand Cayman Island, West Indies. Overall, erosion rates averaged 0.99 mm yr-1; however this figure conceals the fact that the mean erosion rate on open coasts (X=2.77 mm yr–1) was over six times greater than the rate on reef-protected shores (X=0.45 mm yr–1). On lagoonal rocky coasts abrasion and biological action appear to be the dominant erosional processes, but on coasts exposed to high wave surf, bioconstruction dominates over bio-erosion and surface erosion is slight (X=0.17 mm yr–1). Thus, the magnitude and relative importance of physical, chemical and biological erosion processes differ from one locality to the next with variations in coastal exposure and between reef areas with changes in tidal range and wave regime. 相似文献
9.
Patterns of nitrogen accumulation and cycling in riparian floodplain ecosystems along the Green and Yampa rivers 总被引:3,自引:0,他引:3
Patterns of nitrogen (N) accumulation and turnover in riparian systems in semi-arid regions are poorly understood, particularly in those ecosystems that lack substantial inputs from nitrogen fixing vegetation. We investigated sources and fluxes of N in chronosequences of riparian forests along the regulated Green River and the free-flowing Yampa River in semi-arid northwestern Colorado. Both rivers lack significant inputs from N-fixing vegetation. Total soil nitrogen increased through time along both rivers, at a rate of about 7.8 g N m–2 year–1 for years 10–70, and 2.7 g N m–2year–1 from years 70–170. We found that the concentration of N in freshly deposited sediments could account for most of the soil N that accumulated in these floodplain soils. Available N (measured by ion exchange resin bags) increased with age along both rivers, more than doubling in 150 years. In contrast to the similar levels of total soil N along these rivers, N turnover rates, annual N mineralization, net nitrification rates, resin-N, and foliar N were all 2–4 times higher along the Green River than the Yampa River. N mineralization and net nitrification rates generally increased through time to steady or slightly declining rates along the Yampa River. Along the Green River, rates of mineralization and nitrification were highest in the youngest age class. The high levels of available N and N turnover in young sites are not characteristic of riparian chronosequences and could be related to changes in hydrology or plant community composition associated with the regulation of the Green River. 相似文献
10.
The effect of exposure to different concentrations of food and suspended silt on filtration, respiration and condition were studied in the freshwater mussel Hyridella menziesi. Using a milk solids-based food and kaolin to simulate silt, mussels were maintained at different combinations of food and silt concentrations for 3 weeks. Between treatments mean filtration rates ranged from 0.97–1.66 l g–1 h–1, and respiration from 0.50–1.35 mg O2 g–1 h–1. Silt (non-volatile suspended solids up to 35 mg l–1) failed to have a significant effect on filtration rate or condition, but with increasing food levels (volatile suspended solids up to 35 mg l–1) filtration rate was reduced, and condition was reduced at the lowest food concentration (<5 mg l–1). Respiration showed a food × silt interaction between treatment blocks. When food was low respiration increased with increasing silt concentrations, and when silt was low (<5 mg l–1) respiration increased with increasing food concentrations. The observed effects of food and silt on filtration, respiration and condition are discussed in terms of their potential for affecting contaminant bioaccumulation. In low-food situations (i.e., <5 mg l–1), if mussels are pumping large volumes of water, contaminant uptake rates could be enhanced, whereas abundant food would result in lower pumping rates and lower uptake rates. Changes in metabolism with food concentration have implications for contaminant elimination, and changes in biochemical composition associated with changing condition could affect the tissue distribution and retention of contaminants. 相似文献
11.
Depending on the biomass yield on glucose and the cell morphology ofBacillus thuringiensis, three different metabolic states were observed in continuous culture. At dilution rates between 0.18 h–1 and 0.31 h–1 vegetative cells, sporulating bacteria and spores coexisted, while glucose and amino acids were consumed. Only vegetative cells were observed at dilution rates between 0.42 h–1 and 0.47 h–1 and glucose was used as the main carbon and energy source. AtD = 0.50 h–1 the biomass yield on glucose decreases sharply. To define better the specific growth rate range in which the microorganism uses mainly glucose, a dilution rate of 0.25–0.45 h–1 was studied. The experimental data could be adjusted to a Monod model and the following rate coefficients and growth yields were determined: maximum specific growth rate 0.54 h–1, saturation constant 0.56 mg glucose ml–1, biomass growth yields 0.43 g cells (g glucose)–1, and 0.76 g cells (g oxygen)–1, and maintenance coefficients 0.065 g glucose (g cells)–1 h–1 and 0.039 g oxygen (g cells)–1 h–1. 相似文献
12.
Simultaneous removal of benzene, toluene and xylenes mixture by a constructed microbial consortium during biofiltration 总被引:1,自引:0,他引:1
A bacterial consortium with complementary metabolic capabilities was formulated and specific removal rates were 0.14, 0.35, 0.04, and 0.39 h–1 for benzene, toluene, o-xylene, and m,p-xylene, respectively. When immobilized on a porous peat moss biofilter, removal of all five (= BTX) components was observed with rates of 1.8–15.4 g m–3 filter bed h–1. Elimination capacities with respect to the inlet gas concentrations of BTX and airflow rates showed diffusive regimes in the tested concentration range of (0.1–5.3 g m–3) and airflow (0.55–1.82 m3 m–2 h–1) except for o-xylene which reached its critical gas concentration at 0.3 g m–3. 相似文献
13.
D. L. Jones L. C. -H. Wang 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1976,105(2):219-231
Summary The metabolic and cardiac responses to temperature were studied in two species (four subspecies) of western chipmunks (genusEutamias), inhabiting boreal and alpine environments. A specially designed (Fig. 1) implantable biopential radiotransmitter was used to measure heart rate in unrestrained animals. The estimated basal metabolic rates (EBMR) were 1.78 (E. minimus borealis), 1.64 (E. m. oreocetes), 1.50 (E. m. operarius), and 1.69 ml O2 g–1 h–1 (E. amoenus luteiventris), or 839, 752, 698, and 628 ml O2 kg–0.75 h–1, respectively, for the four subspecies (Table 1). The two alpine species (E.m.or. andE.m.op.) had significantly lower EBMR than both of their boreal counterparts. The EBMR from all animals are 120–135% of the predicted values based on body weights of the animals. The thermal neutral zone for the four subspecies ranged from 23.5 to 32°C and the minimum thermal conductances were 0.113, 0.111, 0.112 and 0.112 ml O2 g–1 h–1 °C–1, respectively, or 54.4, 54.0, 50.4 and 52.1 ml O2 kg–0.75 h–1 °C–1, respectively (Fig. 2). No interspecific diffence in conductance was observed. These values are 72 to 85% of their weight specific values. The body temperature ranged between 35.0 and 39.5°C and was usually maintained between 36 and 38°C in all subspecies between ambient temperatures of 3 and 32°C. The estimated basal heart rates were 273, 296, 273 and 264 beats/min, respectively, for the four subspecies, 49–55% of their predicted weight specific values. The resultant oxygen pulses (metabolic rate/heart rate) were 5.49, 4.50, 4.48 and 5.56×10–3 ml O2/beat, respectively, which are 2 to 2.4 times their weight specific values (Table 2).The observed reduction of basal heart rate without the corresponding decreases of basal metabolic rate and body temperature indicate sufficient compensatory increases in stroke volume and/or A-V oxygen difference at rest. Such cardiovascular modifications provide extra reserves when demand for aerobic metabolism rises during bursts of activity typically observed in the western chipmunk.Abbreviations A-V
arterio-venous
- EBMR
estimated basal metabolic rate (ml O2 g–1 h–1)
- HR
heart rate (beats/min)
- MR
metabolic rate (ml O2 g–1 h–1)
- OP
oxygen pulse (ml O2/heart beat)
- Ta, Tb
ambient and body temperature (°C) 相似文献
14.
Atmospheric deposition of nutrients to the North Atlantic Basin 总被引:18,自引:6,他引:12
J. M. Prospero K. Barrett T. Church F. Dentener R. A. Duce J. N. Galloway H. Levy II J. Moody P. Quinn 《Biogeochemistry》1996,35(1):27-73
Atmospheric chemical models are used to estimate the deposition rate of various inorganic oxides of nitrogen (NOy), reduced nitrogen species (NHx) and mineral dust to the North Atlantic Ocean (NAO). The estimated deposition of NOy to the NAO (excluding the coastal ocean) and the Caribbean is 360 × 109 Moles-N m–2 yr–1 (5.0 Tg N); this is equivalent to about 13% of the estimated global emission rate (natural and anthropogenic) and a quarter of the emission rate from sources in North America and Europe. In the case of NHx, 258 Moles-N m–2 yr–1 (3.6 Tg N) are deposited to the NAO and the Caribbean; this is about 6% of the global continental emissions. There is relatively little data on the deposition rate of organic nitrogen species; nonetheless, this evidence suggests that concentrations and deposition rates are comparable to those for inorganic nitrogen.Because of anthropogenic emissions, the present-day deposition rate of NOy to the NAO is about five times greater than pre-industrial times largely due to emissions from energy production and biomass burning. The present-day emissions of NHx from continental anthropogenic sources are about four-to-five times greater than natural sources, mostly due to the impact of emissions from animal wastes associated with food production. Indeed, present-day emissions of NHx from animal waste are estimated to be about 10 times greater than the pre-human era. The deposition rate of mineral dust to the NAO is about 170 Tg yr–1; deposited with the dust (assuming average crustal abundances) is about 6 Tg yr–1 of Fe and 0.2 Tg yr–1 of P. Dust deposition in the NAO is almost completely attributable to transport from North African sources; a substantial fraction of the dust over the NAO is probably mobilized as a consequence of land use practices in arid regions and, consequently, it should be regarded as a pollutant. 相似文献
15.
Bradley J. Pusey 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1986,156(5):701-705
Summary Measurement of the rates of oxygen consumption and nitrogen excretion in fed and starvedLepidogalaxias salamandroides showed that starvation has no effect on these basal metabolic parameters. A low metabolic rate (50 ml O2 kg–1 h–1) is suggested to account for the lack of such an effect.A high proportion of the total waste nitrogen is excreted as urea and the magnitude of this fraction is also unaffected by starvation. The importance of urea synthesis is consistent with this species' ability to aestivate.The results are discussed with reference to current concepts in fish aestivation. 相似文献
16.
Munn AJ Dawson TJ 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2003,173(7):575-582
Generally, young growing mammals have resting metabolic rates (RMRs) that are proportionally greater than those of adult animals. This is seen in the red kangaroo (Macropus rufus), a large (>20 kg) herbivorous marsupial common to arid and semi-arid inland Australia. Juvenile red kangaroos have RMRs 1.5–1.6 times those expected for adult marsupials of an equivalent body mass. When fed high-quality chopped lucerne hay, young-at-foot (YAF) kangaroos, which have permanently left the mother's pouch but are still sucking, and recently weaned red kangaroos had digestible energy intakes of 641±27 kJ kg–0.75
day–1 and 677±26 kJ kg–0.75
day–1, respectively, significantly higher than the 385±37 kJ kg–0.75
day–1 ingested by mature, non-lactating females. However, YAF and weaned red kangaroos had maintenance energy requirements (MERs) that were not significantly higher than those of mature, non-lactating females, the values ranging between 384 kJ kg–0.75
day–1 and 390 kJ kg–0.75
day–1 digestible energy. Importantly, the MER of mature female red kangaroos was 84% of that previously reported for similarly sized, but still growing, male red kangaroos. Growth was the main factor affecting the proportionally higher energy requirements of the juvenile red kangaroos relative to non-reproductive mature females. On a good quality diet, juvenile red kangaroos from permanent pouch exit until shortly after weaning (ca. 220–400 days) had average growth rates of 55 g body mass day–1. At this level of growth, juveniles had total daily digestible energy requirements (i.e. MER plus growth energy requirements) that were 1.7–1.8 times the MER of mature, non-reproductive females. Our data suggest that the proportionally higher RMR of juvenile red kangaroos is largely explained by the additional energy needed for growth. Energy contents of the tissue gained by the YAF and weaned red kangaroos during growth were estimated to be 5.3 kJ g–1, within the range found for most young growing mammals.Abbreviations BMR
basal metabolic rate
- DEI
digestible energy intake
- MER
maintenance energy requirement
- MERg
maintenance plus growth energy requirement
- PPE
permanent pouch exit
- RMR
resting metabolic rate
- YAF
young-at-foot
Communicated by I.D. Hume 相似文献
17.
Pore water phosphorus and iron concentrations in a shallow,eutrophic lake — indications of bacterial regulation 总被引:1,自引:0,他引:1
Peak pore water SRP and iron(II) concentrations were found during summer in surface sediments in the shallow and eutrophic L. Finjasjön, Sweden, and the concentrations generally increased with water depth. The SRP variation in surface sediments (0–2 cm) was correlated with temperature (R2 = 0.82–0.95) and iron(II) showed a correlation with sedimentary carbon on all sites (R2 = 0.42–0.96). In addition, sedimentary Chla, bacterial abundances and production rates in surface sediments (0–2 cm) varied seasonally, with peaks during spring and fall sedimentation. Bacterial production rates were correlated with phosphorus and carbon in the sediment (R2 = 0.90–0.95 and R2 = 0.31–0.95, respectively), indicating a coupling with algal sedimentation. A general increase in sediment Chla and bacterial abundances towards sediments at greater water depth was found. Further, data from 1988–90 reveal that TP and TFe concentrations in the lake were significantly correlated during summer (R2 = 0.81 and 0.76, in the hypolimnion and epilimnion, respectively). The results indicate that the increase in pore water SRP and Fe(II) in surface sediments during summer is regulated by bacterial activity and the input of organic matter. In addition, spatial and temporal variations in pore water composition are mainly influenced by temperature and water depth and the significant correlation between TP and TFe in the water suggests a coupled release from the sediment. These findings support the theory of anoxic microlayer formation at the sediment-water interface. 相似文献
18.
Marija Babi Sandra Radi Petra Cvjetko Vibor Roje Branka Pevalek-Kozlina Mirjana Pavlica 《Aquatic Botany》2009,91(3):166-172
The physiological effects of thallium(I)-acetate on the duckweed Lemna minor after 1-, 4-, 7- and 14-d exposure were analyzed. High bioaccumulation of Tl (221 mg kg−1 dry wt at 2.0 μM Tl-acetate) caused an inhibition of plant growth. After 14-d exposure, 0.2, 0.5, 1.0 and 2.0 μM Tl-acetate reduced the frond-number growth rate by 21.1%, 39.4%, 66% and 83.1%, respectively. Tl-acetate also induced a modulation of the antioxidative response by depleting the ascorbate content and affecting the antioxidative enzymes activities. Superoxide dismutase showed a continuous increase of activity (31–67%) after Tl-acetate exposure. Other antioxidative enzymes displayed a biphasic response to both the concentration and the exposure period. Exposure up to 7 d decreased the catalase activity (up to 40%) in plants treated with higher Tl-acetate concentrations. In contrast, 14-d exposure increased the activity of the enzyme (≥90%). Short-term exposure increased ascorbate peroxidase activity (13–41%), except in plants exposed to the highest Tl-acetate concentration. However, 14-d exposure decreased the enzyme activity at all concentrations tested (38–60%). Although pyrogallol peroxidase activity increased (up to 26%) during 4-d exposure, longer exposures to the highest two concentrations decreased the activity of the enzyme (25–48%). In general, short-term exposure to Tl-acetate activated the antioxidant capacity, which resulted in recovery of the frond-number growth rates in Tl-treated plants. In spite of the activation of the antioxidative response during short-term exposure, higher Tl-acetate concentrations increased the hydrogen peroxide level (up to 45%) and induced marked oxidative damage to lipids, proteins and DNA. Longer exposure induced a decline of the antioxidative response, and plants showed the symptoms of oxidative damage even at lower Tl-acetate concentrations. The genotoxic effect was evaluated by an alkaline version of the cellular and acellular Comet assay, which revealed an indirect genotoxic effect of Tl-acetate, suggesting oxidatively induced damage to DNA. 相似文献
19.
Microbial diversity, numbers, and metabolic activities in Minnesota peatlands were investigated using a variety of microbial enrichment and enumeration procedures together with radioisotopic measurements of microbial degradative processes. Minnesota peatlands were shown to contain large microbial populations of wide metabolic diversity. Direct counts of bacteria using epifluorescence microscopy indicated bacterial populations of about 108 ml–1 of peatland water, irrespective of depth. Radioisotopic most-probable-number (MPN) counts of heterotrophs able to mineralize14C-labeled substrates to14CO2 showed significant populations of glucose degraders (104–106 ml–1) as well as degraders of benzoate (102–103 ml–1), 2,4-dichlorophenoxyacetate (102–105 ml–1), and sphagnum (103–107 ml–1) in the various peatlands examined. The MPNs of NO3
– reducers varied from 103–106 ml–1, SO4
– reducers from 102–103 ml–1, methanogenic bacteria from 103–106 ml–1, and methane oxidizers from 103–104 ml–1, depending on sampling site and depth. Eighty pure cultures of aerobic bacteria and fungi were isolated from Minnesota peats. Most of those cultures tested were able to grow on at least 20 organic compounds (carbohydrates, aromatic molecules, hydrocarbons, etc.) as sole sources of carbon and energy. One isolate, aBacillus, was able to fix atmospheric N2. Several of the isolates were able to mineralize14C-labeled lignin. 相似文献
20.
Fluff deposition on intertidal sediments: effects on benthic biota, ammonium fluxes and nitrification rates 总被引:1,自引:0,他引:1
Mario Laima Dorota Maksymowska-Brossard Pierre-Guy Sauriau Pierre Richard Michelle Girard Dominique Gouleau Lucette Joassard 《Biogeochemistry》2002,61(2):115-133
The effects of fluff deposit on benthic biota,NH4
+ fluxes and nitrification was studied in thelaboratory using waterlogged and reflooded intertidal sediments fromMarennes-Oléron Bay, France. The fluff deposit was enriched inNH4
+ compared to underlying sediments, and promotedchanges of the sediment pH, Eh, C:N ratio, C:chla ratio and the NH4
+ efflux tooverlying water. Statistical analysis showed that pore waterNH4
+ concentrations were strongly influenced byinteractions between fluff, drying, depth and bioturbation. The fluff depositresulted in anoxia in the top sediments and moved the nitrification zone tosurface layers in fluff. However, the NH4
+ enrichment influff did not significantly change actual nitrification rates (range 0–1mmol m–2 d–1) or potentialnitrification rates (range 3–11 mmolNO3
– m–2d–1). 相似文献