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1.
Seasonal fluctuations of zooplankton biomass (dry weight) were determined during a year in two localities of Lake Xolotlán (Managua). Biomass estimations of the most common species of rotifers, cladocerans and copepods were made. The maximal zooplankton biomass was observed in February–April (dry season) in coincidence with the period of highest phytoplankton abundance. Copepods contributed with 78% and 84% to the mean zooplankton biomass at points 1 and 7, respectively. Cladocera biomass was lowest during most of the year, and it was probably controlled by fish predation. Development of rotifer biomass was more intense during the rainy season, when detritus particles were more abundant. Daily fluctuations of zooplankton biomass were not pronounced.  相似文献   

2.
  总被引:1,自引:7,他引:1  
Pauli  Hans Rainer 《Hydrobiologia》1989,186(1):355-361
Body and egg volumes of 12 rotifer species of Lake Constance were calculated from more than 18 000 individually measured animals using geometric approximations. Body (VA) and egg (VE) volumes of various rotifer species have an allometric relationship described by: VE = 1272 · VA0.3379, while the relation VE/VA for each species was constant ranging from 0.016 to 0.87. Dry weight of adult rotifers was assumed to be the sum of the egg dry weight plus a corrected weight increment from egg to adult. It was estimated with the formula WA = WE · (1 + a · FA/FE) where (a) was varied between 0 and 0.1. Egg dry weight content was assumed to be 35 % of fresh weight. The estimates of dry weight to wet weight ratios ranged from 0.57 % (Asplanchna priodonta) to 29.4 % (Kellicottia longispina). Dry weight estimates obtained with this method are comparable to those obtained with direct measurements of dry weight or carbon content.This investigation was supported by the Deutsche Forschungsgemeinschaft within the Special Collaboration Program (SFB) Cycling of Matter in Lake Constance.  相似文献   

3.
This study demonstrates that the pre-emergence herbicide napropamide will enhance plant growth when applied at very low concentrations. Stimulation of shoot elongation, fresh weight, and dry weight was observed when seeds of wheat, corn, raddish, and soybean were soaked in very dilute solutions of napropamide for 6 hr. Biomass synthesis by Red Kidney bean was dramatically increased by 10 m napropamide, a 24.3% increase in fresh weight and a 76% increase in dry weight being observed. It is apparent that napropamide should be listed with those herbicides that have exhibited growth regulator properties.  相似文献   

4.
微藻光密度与细胞密度及生物质的关系   总被引:2,自引:0,他引:2       下载免费PDF全文
梁芳  鸭乔  杜伟春  温晓斌  耿亚洪  李夜光 《生态学报》2014,34(21):6156-6163
以四种常见微藻,小球藻(Chlorella sp.XQ-20044)、栅藻(Scenedesmus sp.SS-200716)、绿球藻(Chlorococcum sp.)和螺旋藻(Spirulina sp.CH-164)为实验材料,用梯度稀释法测定对数生长期不同浓度藻液的光密度(OD)、细胞密度和生物质干重(DW),在光自养分批培养模式下对4种微藻进行OD-波长(350—800 nm)扫描,同时测定细胞密度和生物质干重,分析藻液OD与细胞密度、生物质干重的关系。结果表明:在任何波长下,对数生长期的4种微藻细胞密度与OD值、生物质干重与OD值的变化都不成比例,波长不同其拟合曲线偏离直线的程度不同。但是,在435 nm处这种关系最接近直线,可以用直线方程近似描述(R20.98),其它波长处细胞密度-OD、干重-OD的关系都可以用二项式方程很好地描述(R20.99)。因此,光密度法适用于连续和半连续培养,可以用435 nm处测得的OD值计算细胞密度与干重。但是在分批培养模式下,4种微藻DW/OD比值随着培养时间均逐渐上升。小球藻DW/OD540为0.19—0.44 g/L,栅藻DW/OD540为0.36—0.53 g/L,绿球藻DW/OD540为0.48—0.75 g/L,螺旋藻DW/OD560为0.46—0.74 g/L,因此分批培养模式下采用测定藻液OD值反映细胞密度和生物质的方法不适用,只有直接测定细胞密度和生物质才是准确的。研究结果为正确使用分光光度法监测微藻生长提供依据。  相似文献   

5.
The mathematical model introduced by Okazaki & Tanaka (J. Ferment Technol. 1980, 58: 471–476) for estimating fungal growth in solid state fermentations by CO2 evolution, was incorporated into a relationship developed to estimate biomass growth from dry matter weight loss. The proposed equation fitted experimental data very well (R2=0.987, P<0.0001) and allowed accurate predictions of fungal specific growth rate and maximal biomass in the solid substrate fermentation system.  相似文献   

6.
The effect of preservation methods on dry weight (DW) and ash-free dry weight (AFDW) of Radix peregra (Gastropoda), Asellus aquaticus (Isopoda), Erpobdella octoculata (Hirudinea) and Glyptotendipes sp. (Chironomidae) was studied. Ethanol, formaldehyde, and Bouin were used as preservative. In case of preservation of macro-invertebrates in ethanol substancial changes in DW and AFDW biomass were observed. In the four different taxa the loss in DW varied between 7.2–21.9% after a 3 month preservation period in 70% ethanol. A comparatively small range in AFDW loss (16.2–19.7%) was found. Changes in DW and AFDW biomass during preservation were significantly affected by the duration of the preservation, by temperature, light conditions and the volume of the preservative. The changes in AFDW were also significantly affected by the concentration of the preservatives. Preservation in 10% formaldehyde did not cause significant changes in DW and AFDW biomass.Contribution nr. 42 of the nymphalid project.  相似文献   

7.
Sixty-five plant species have been found in Lake Provala (the Vojvodina Province, Serbia) and its riparian zone. Among them, three hydrophytes were dominant: Nymphoides peltata, Myriophyllum spicatum and Ceratophyllum demersum. As interactions between different ecological factors, especially light, temperature and nutrient level, are of prime importance for productivity of macrophytes, we analyzed the main physical and chemical indicators of water quality in the studied location. In the vegetation period of the year 2000, the dominant hydrophytes were analyzed for biomass production dynamics in the studied aquatic ecosystem, including fresh weight (FW), dry weight (DW) and ash free dry weight (AFDW). The studied plant species achieved maximum biomass production in June, with statistical differences among the species at the significance level of α = 0.05.  相似文献   

8.
    
Aims: Microbial biomass is an important biotechnological parameter. The traditional method for its determination involves an oven‐drying step and equilibration to room temperature before weighing, and it is tedious and time consuming. This work studied the utilisation of a moisture analyser consisting of an efficient infrared‐heating module and an analytical balance for the determination of microbial biomass by dry weight. Methods and Results: The method duration depended on the sample volume and was between 7 and 40 min for sample volumes of 1–10 ml. The method precision depended on the total dry weight analysed – 10 mg of total dry weight being sufficient to achieve coefficients of variation of 5% or less. Comparison with the conventional oven method provided a correlation coefficient r2 of 0·99. The recovery of an internal standard ranged between 94·2 and 106·4% with a precision of 1·39–4·53%CV. Conclusions: Validation revealed sufficient method accuracy, precision and robustness and was successfully applied to the study of yeast and bacterial growth kinetics. Techniques are discussed that allow for increased method precision at low biomass concentrations, and equations are provided to estimate required drying time and method precision based on sample volume and total sample dry weight, respectively. Significance and Impact of the Study: This work presents a rapid method for the determination of microbial biomass, allowing for the timely implementation of biomass‐based information in biotechnological and laboratory protocols.  相似文献   

9.
    
Cyanobacteria are photosynthetic microorganisms which can be found in various environmental habitats. These photosynthetic bacteria are considered as promising feedstock for the production of the third- and the fourth-generation biofuels. The main subject of this review is highlighting the significant aspects of the biofuel production from cyanobacteria. The most recent investigations about the extraction or separation of the bio-oil from cyanobacteria are also adduced in the present review. Moreover, the genetic engineering of cyanobacteria for improving biofuel production and the impact of bioinformatics studies on the designing better-engineered strains are mentioned. The large-scale biofuel production is challenging, so the economic considerations to provide inexpensive biofuels are also cited. It seems that the future of biofuels is strongly dependent to the following items; understanding the metabolic pathways of the cyanobacterial species, progression in the construction of the engineered cyanobacteria, and inexpensive large-scale cultivation of them.  相似文献   

10.
Specific leaf area in barley: individual leaves versus whole plants   总被引:1,自引:0,他引:1  
We have explored the relationships between specific leaf area calculated for a whole plant and its individual leaves. Barley was grown in hydroponics in controlled environment cabinets. Plants were harvested on the basis of physiological age (defined as the number of days after full expansion of leaves on the main stem) and the area and weight of whole, fully expanded, leaves measured and specific leaf area (SLA) of individual leaves or whole plants calculated. Specific leaf area calculated for individual leaves (SLAL) varied with leaf position and with leaf age after full expansion whereas SLA calculated for whole plants (SLAP) varied with plant age. The same conclusions were reached whether the results were based on total dry weight or dry weight minus soluble carbohydrates ('structural weight'). Transferring plants to shade on the day of full expansion of the third leaf on the main stem increased the SLAP, and also SLAL of leaves 3 and 4 on the main stem (leaf 4 being the younger leaf of the two), because of a decrease in the 'structural weight' of these leaves. However SLAL of leaf 2 (which was older than leaf 3) was not affected by shading; the effect was confined to leaves developing in the new conditions.  相似文献   

11.
    
Regression equations relating length to dry weight have been derived for the four larval instars of Chaoborus flavicans (Meigen). A general equation, in which all instars are lumped, was also developed, but produces biased results outside a rather narrow central interval.The rate of increase, in terms of weight, is minimal in first instar larvae and maximal in fourth instar larvae, while the second and third instars are both intermediate and very closely related to one another.Three critical points have been defined, corresponding to body lengths at which a particular instar has to molt in order to be able to continue growing optimally.
Résumé Des équations de régression longueur-poids sec ont été établies pur les différents stades aquatiques de développement de Chaoborus flavicans (MEIGEN).La croissance pondérale, minimale pour les larves de premier stade, est maximale au cours du quatrième stade; les larves de deuxième et de troisième stade présentent des croissances comparables.L'emploi des équations propres à chaque stade est préférable à celui de l'équation moyenne établie pour l'ensemble des quatre stades larvaires.
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12.
The freeze-dried (extracted and non-extracted) biomass of 15 microalgal species grown in axenic mass culture and belonging to the Cyanobacteria, Chloro-, Eustigmato-, Phaeo-, Rhodo- and Tribophyceae were investigated for their ability to adsorb cadmium (Cd) ions from aqueous solutions. For comparison, other standard adsorbing materials (activated carbon, silica gel, siliceous earth) were included in the studies. The biomass of 11 microalgae exhibited a higher Cd adsorption than the standard materials. Extraction of the algal biomass increased the Cd adsorption capability of some, but not all microalgae. High Cd adsorption was found inAnabaena lutea, Nodularia harveyana, andNostoc commune (Cyanobacteria),Chlamydomonas sp. (Chlorophyceae),Bumilleriopsis filiformis (Tribophyceae), and inEctocarpus siliculosus, Halopteris scoparia andSpermatochnus paradoxus (Phaeophyceae). The specific surface (m2 cm–3) of the various microalgae was determined by means of laser diffractometry.Anabaena inaequalis andA. lutea (Cyanobacteria) and the Phaeophyceae had especially high Cd adsorption per surface unit. Most of the Cd adsorbed to these various materials could be desorbed subsequently with diluted mineral acid (pH 2).  相似文献   

13.
14.
目的:干眼已成为影响人们生活质量的主要眼表疾病之一。有关干眼的研究已成为当今眼科的研究热点,本文通过激光共焦显微镜对蒸发过强型干眼患者眼表结构特征进行观察,从细胞层面对干眼进行研究。方法:海德堡激光共焦显微镜(HRT3)对35例(60只眼)干眼患者及35名(60只眼)正常人的角膜上皮层朗格汉斯细胞,睑板腺腺泡密度,睑板腺开口直径及形态进行观察,并对观察结果进行描述记录。结果:正常眼角膜中央上皮层朗格汉斯细胞(LC)个数的平均密度为58±19个/mm2,干眼组为(137±29)个/mm2,两者比较差异具有统计学意义(P0.05)。正常眼组角膜上皮下朗格汉斯细胞突起较短,分支较少,干眼患者角膜上皮下朗格汉斯细胞突起呈树支状,其突起较正常眼组数量多且长度较长,正常组睑板腺(MG)腺泡的平均密度为115±28个/mm2,干眼患者的睑板腺腺泡的平均密度59±16个/mm2,两者比较差异具有统计学意义(P0.05)。干眼组睑板腺腺泡内呈中等程度反光,对照组腺泡内呈低反光。正常组睑板腺开口呈圆形,内壁光滑,直径为62±14μm,干眼组睑板腺开口欠光滑,直径35±11μm,两者比较差异具有统计学意义(P0.05)。结论:共聚焦显微镜观察到在蒸发过强型干眼患者中,睑板腺腺泡直径增大,密度降低,睑板腺的开口直径变小,同时,角膜朗格汉斯细胞活化,数量增多,共聚焦显微镜可从细胞层面观察蒸发过强性干眼的眼表结构改变,使干眼病理变化的研究更为直观,为今后的进一步研究提供了更为准确的材料。  相似文献   

15.
Perennial microbial mats can be the dominant autotrophic community in Antarctic lakes. Their seasonal growth results in clearly discernible annual growth layering. We examined features of live microbial mats from a range of depths in Lake Hoare, Antarctica, that are likely to be preserved in these layers to determine their potential as proxies of past growth performance. Cyanobacteria dominated the mat for all but the deepest depth sampled. Changes in areal concentrations of phycobilin pigments, organic matter and extracellular polysaccharide and in species composition did not correspond to changes in various water column properties, but showed a linear relationship with irradiance. Carbonate accumulation in the mats correlated with biomass markers and may be inferred as an index of mat performance. We examined the carbonate content of annual layers laid down from 1958–1959 to 1994–1995 in sediment cores from 12 m depth. The carbonate content in the layer showed a significant correlation with the mean summer air temperature. These data suggest a link between air temperature and microbial mat growth performance, and suggest that it is mediated via irradiance. Laminated microbial mats in Antarctic lakes have the potential to act as fine-resolution records of environmental conditions in the recent past, although interpretation is complex.  相似文献   

16.
With a view to assess the bioactive potential of the unexploited marine cyanobacteria available in abundance in the marine habitat, water-soluble fraction of the ethanolic extract of 12 different strains of marine cyanobacteria were administered to male rats and their impact on food intake, body weight and certain haematological characters including RBC counts, WBC-TC and DC, platelet counts, haemoglobin content and mean corpuscular haemoglobin was studied. The results suggest prospective applications as feed/nutritional supplements; among them, Spirulina subsalsa BDU 30311, Oscillatoria salina BDU 10142 and Phormidium valderianum BDU 20571 appear highly promising in this regard. Lyngbya sp. BDU 30601 and Pseudanabaena schmidlei BDU 30313 appear to contain one or more toxins and deter food intake and cause decrease in body weight. With Synechococcus elongatus BDU 30312 food intake increased over the control which was not commensurate with the change in body weight. The results relating to the haematological characters indicate bioactivity of the cyanobacteria in the animal-based systems, some of which are positive, whereas a few strains like Lyngbya BDU 30601 are negative, implying their pharmaceutical application.  相似文献   

17.
    
Given that fish are considered as one of the best pollution indicators of aquatic ecosystems, numerous studies have been carried out on metal pollution in fish. Metal concentrations are commonly expressed either per unit of wet or dry tissue weight. However, there is a lack of standardized reporting of elemental concentrations, with the majority publications using dry tissue weight as a measurement unit. Moreover, a significant number of papers also does not clearly report which of the two measurement units is used. Lack of standardized reporting obstructs comparability of studies that use different measurement units, which could be resolved either by reporting elemental concentrations using both types of measurement units (i.e., with one of them provided in the supplementary material, or alternatively to provide wet to dry weight conversion factors). This issue, while being of substantial importance for the scientific community, has not received proper attention so far.  相似文献   

18.
Individual dry weights of various crustacean zooplankton in Lake Kariba were determined. All the zooplankters were collected from pelagic waters. Regression equations relating dry weight to body length were computed for those species or groups in which size classes could be separated: Bosmina longirostris, Ceriodaphnia cornuta, and copepod copepodites and adults. The mean individual dry weights obtained for most of these zooplankters are similar to those reported in other studies.  相似文献   

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20.
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