Isolation and characterization of 11 polymorphic trinucleotide microsatellite markers in the stonefly Arcynopteryx compacta (Plecoptera: Perlodidae)

We describe the isolation of 11 polymorphic trinucleotide microsatellite loci from the stonefly Arcynopteryx compacta. Loci were highly variable with 3 to 14 alleles (mean = 6.45). Observed heterozygosity ranged from 0 to 0.867. Seven loci showed significant deviation from Hardy–Weinberg equilibrium across both populations. There was no evidence for null alleles, and thus, Hardy–Weinberg departures could have resulted from genetic structure between populations or subpopulations. No linkage between loci was found. The 11 loci should prove highly informative for population genetic studies.     

Lake Kinneret dissolved oxygen regime reflects long term changes in ecosystem functioning

Lake Kinneret (Israel) has undergone several prominent chemical and biological changes since 1970. Between 1970 and 1991 significant, long-term gradual increase were recorded in epilimnetic dissolved oxygen (DO) concentrations (about 20%), and in pH levels (0.2 units). Concomitantly there was a significant increase in hypolimnetic H₂S concentrations (about 75%) and a long-term gradual drop in zooplankton biomass (50%). Since 1994 these trends were reversed and the levels of the three chemical parameters have returned to those found in the 1970's and that of zooplankton to mid 1980's levels. The present study is an attempt to relate some of these long term changes by means of yearly oxygen budgets, based on fluxes of oxygen producing and consuming processes. This analysis raises the possibility that part of the long-term increase in epilimnetic DO and pH between 1970 to 1990 may be attributed to reduced inputs of organic matter from alochthonous sources and possibly to enhanced burial of organic matter in the bed sediments. However, the major cause for the observed increase in epilimnetic DO and pH is increased sedimentation of organic matter to the hypolimnion during stratification. As indicated by the amount of H₂S formed in the hypolimnion during stratification added to the amount of oxygen entrapped in this layer at the onset of thermal stratification, between 1970 to 1991 the sedimentation flux of organic matter increased by approximately 40%. It is estimated that during these two decades hypolimnetic respiration increased from ca. 8% of the annual amount of oxygen evolved due to photosynthesis during the early 1970's to ca. 12.5% during the 1980's. The shift in the layer of oxidative processes is suggested to be the result of a multi-annual decline in zooplankton grazing pressure, which led to increased sedimentation of organic matter. The reversed trends for DO, pH and H₂S since 1994 may have partially been due to the increase in zooplankton activity and partially due to changes in phytoplankton community structure.     

Reaction kinetics in biofilms

A novel in situ microtechnique allows evaluating parameters of diffusion-controlled reactions in biofilms. A microprobe, 15 mum in diameter, was used to simultaneously measure the dissolved oxygen concentration and the optical density at different depths in a submerged biofilm. Based on the results, the biofilm diffusion coefficient for dissolved oxygen, D(f) the dissolved oxygen flux through the biofilm surface, J(02), and the half velocity coefficient, K(s), have been calculated.     

Impact of human activities on stonefly (Insecta,Plecoptera) ecological metrics in the Hron River (Slovakia)

A total of 57 stonefly species have been recorded in the Hron River. The natural gradient (slope and stream width) and pollution gradient of the river were defined using CCA based on physical, chemical and stonefly data. Stonefly metrics (abundance, richness/diversity, sensitivy/tolerance and functional metrics) were used to estimate the quality of the Hron River and the degree of proximity to its natural state. Similar results were obtained using two different methods. The first method was based on the homogeneity of variance and the interquartile range of different groups of stretches of the Hron River and the second was based on deviations from the expected values of biological metrics in a given stretch of the river. These values continuously decreased with increasing distance from the spring area, with the exception of the saprobic index, which increased in a downstream direction, and the stonefly average score, which did not change significantly along the whole river flow. The Stonefly Average Score (SAS) metric is universal for a variety of habitats such as the Hron River upstream and downstream, and is a reliable indicator of water quality and the natural course of a stream.     

溶解氧对虹鳟呼吸机能及红细胞特性的影响

目的：初步研究溶解氧对虹鳟呼吸机能及红细胞特性的影响。方法：设四组溶氧水平,测定呼吸频率、血液中PO2、PCO2和pH值,并以RBC、Hb、脆性、膜粘滞性及丙二醛含量等指标观察溶氧对红细胞的影响。结果：溶解氧升高使鱼呼吸频率降低,血液PO2升高（P〈0.05）;高溶氧导致红细胞数、丙二醛含量降低。红细胞膜粘滞系数在试验第10d时,高氧组明显高于其它组,但30d时各溶氧组差异不显著。结论：在一定范围内溶解氧升高可以改善机体组织氧含量,提高呼吸功能,红细胞对溶氧变化有其生理适应性。     

The determination of desirable and nuisance plant levels in streams

To cope with luxuriant plant growth in the streams of southern Ontario, an approach to determine the desirable and nuisance plant levels was proposed.With a more intensive analysis of the assimilation efficiency of plant communities, which includes the fractionation of community respiration as well as compensation for the plant self-shading effect, the plant biomass of all species component expressed as chlorophyll a can be estimated from the modified growth equation, where B is the biomass, P_max is the photosynthetic growth rate at light saturation, A is the assimilation number and S is the plant shading coefficient. Once comparable biomass values are available, a desirable plant level relative to specified environmental standards can be determined.For instance, to meet the minimum dissolved oxygen criteria of 5 ppm, the desirable and the nuisance crop levels in the North Thames River, Ontario, were found to be 0.15 and 0.75 g chla/m² respectively.     

Gut evacuation of walleye pollock larvae in response to feeding conditions

Gut residence times of first-feeding walleye pollock larvae were measured at 6°C in continuous and discontinuous feeding regimes. Larvae fed tagged copepod prey evacuated their guts more quickly in continuous feeding as compared to the discontinuous feeding treatment. The mean gut residence time was estimated to be 5.0 h for larvae feeding continuously. Gut evacuation by larvae fed tagged prey and then isolated without food (discontinuous treatment) was slower and more variable, with an estimated gut residence time exceeding 8.0 h. Field and laboratory observations suggest that the larval fish gut may be modeled as an intermittent plug-flow reactor (PFR) in response to diel feeding patterns. The cyclical nature of gut dynamics has implications for gut content analyses and the estimation of daily food rations.     

Humoral immune response upon mild heat-shock conditions in Galleria mellonella larvae

Larvae of Galleria mellonella exposed to mild heat-shock (38 degrees C) showed an enhanced humoral immune response after microbial infection in comparison to infected animals grown at 28 degrees C. This enhanced response was manifested by increased expression of antimicrobial peptide (AMP) genes leading to enhanced antimicrobial activity in the hemolymph. We found an increased level of Hsp90 and changes in the level of a 55kDa protein recognized by anti-Hsp90 antibodies in fat bodies of infected animals reared at 28 degrees C as well as in uninfected animals exposed to elevated temperature. Pre-treatment of animals with an inhibitor of Hsp90, 17-DMAG, prior to immunization resulted in increased expression of AMP genes encoding gallerimycin and cecropin at 38 degrees C. This observation was correlated with the changes in Hsp90 protein and increased level of 55kDa protein. Also G. mellonella larvae pre-treated with 17-DMAG and exposed to mild heat-shock for 30min showed an increased survival rate after infection with entomopathogenic bacteria Pseudomonas aeruginosa. We also show the effect of 17-DMAG on the phosphorylation state of ERK MAP kinase. We postulate that Hsp90 may play a significant role in converging pathways involved in the insect immune response and heat-shock.     

Diversity and activity of aquatic fungi under low oxygen conditions

1. The objective was to test whether a decrease in oxygen concentration in streams affects the diversity and activity of aquatic hyphomycetes and consequently leaf litter decomposition. 2. Senescent leaves of Alnus glutinosa were immersed for 7 days in a reference stream, for fungal colonization, and then incubated for 18 days in microcosms at five oxygen concentrations (4%, 26%, 54%, 76% and 94% saturation). Leaf decomposition (as loss of leaf toughness), fungal diversity, reproduction (as spore production) and biomass (ergosterol content) were determined. 3. Leaf toughness decreased by 70% in leaves exposed to the highest O₂ concentration, whereas the decrease was substantially less (from 25% to 45%) in treatments with lower O₂. Fungal biomass decreased from 99 to 12 mg fungi g⁻¹ ash‐free dry mass on exposure to 94% and 4% O₂ respectively. Sporulation was strongly inhibited by reduction of dissolved O₂ in water (3.1 × 10⁴ versus 1.3 × 10³ spores per microcosms) for 94% and 4% saturation respectively. 4. A total of 20 species of aquatic hyphomycetes were identified on leaves exposed to 94% O₂, whereas only 12 species were found in the treatment with 4% O₂ saturation. Multidimensional scaling revealed that fungal assemblages exposed to 4% O₂ were separated from all the others. Articulospora tetracladia, Cylindrocarpon sp. and Flagellospora curta were the dominant species in microcosms with 4% O₂, while Flagellospora curvula and Anguillospora filiformis were dominant at higher O₂ concentrations. 5. Overall results suggest that the functional role of aquatic hyphomycetes as decomposers of leaf litter is limited when the concentration of dissolved oxygen in streams is low.     

Tufa deposition and periphyton overgrowth as factors affecting the ciliate community on travertine barriers in different current velocity conditions

A characteristic of aquatic systems in karstic region is the formation of tufa – the product of calcium carbonate precipitation. Artificial substrata (glass slides) were used to investigate the influence of tufa deposits at two different current velocities (5 cm s^–1 and 50 cm s^–1) on the ciliate assemblages in periphyton. After two-month exposure periods, periphyton biomass and tufa deposit were c. three times greater at 50 cm s^–1 than at 5 cm s^–1. Ciliate population density was also higher on artificial substrata exposed in a lotic than in a lentic microhabitat (the overall mean number of ciliates at 5 cm s^–1 was 122 ind. cm^–2, and at 50 cm s^–1 497 ind. cm^–2). At each of the two observed current velocities, a Principal Components (PCA) ordination of the colonized ciliate associations showed a spatial separation of the associations that developed under two different conditions of tufa deposition. During the period of greater tufa deposit, associated with greater periphyton overgrowth rate, the ciliate communities had higher species diversity (a higher number of species and a lower number of individuals). Species diversity of ciliates had a positive nonlinear relation to tufa deposition rate. These results suggest that artificial surfaces covered by a rough tufa layer associated with greater periphyton biomass offer diverse conditions for colonization by ciliates.     

Monitoring of haploid maize cell suspension culture conditions in bioreactors

Maize (Zea mays L.) haploid cells were cultivated in a 1500 ml aerated and stirred batch bioreactor using modified BM medium. Cell growth was highly affected by pH and dissolved oxygen, and we observed two fairly distinct growth phases. During the first two days after inoculation at pH 5.8, oxygen consumption was high and the cells lowered the pH to a value around 4.3. After this period the pH stabilized at 4.5 and the dissolved oxygen reached a steady level. Decreasing dissolved oxygen concentration leads to lower growth rate and to higher pH. Both events mean stress conditions for the cell culture and probably result in increased genetic variability, and the loss of regeneration capacity. The stress condition during the adaptation phase can be eliminated by decreasing the pH of the medium to 4.7 before inoculation and by keeping dissolved oxygen above 40%. These conditions provide prolonged exponential growth dynamics and the cell suspensions could be the basis of large scale cultures also.Abbreviations 2,4-d 2,4-dichlorophenoxyacetitc acid - NAA naphthalene acetic acid     

Relation between dissolved oxygen concentration and ajmalicine production rate in high-density cultures of Catharanthus roseus

The relation between dissolved oxygen (DO) and the ajmalicine production rate of Catharanthus roseus was investigated in 15-L tank reactors at constant stirrer speed and gas flow rate. Below a DO concentration of 29% of air saturation the ajmalicine production rate was less than 0.06 mumol/g/d. Above a DO of 43% the ajmalicine production rate was constant at 0.21 mumol/g/d. Between a DO of 29% and 43% there was a strong relation between the ajmalicine production rate and the DO concentration. After a period of at least 12 days at DO /=57%. A kinetic equation is proposed for the relation between DO and the specific ajmalicine production rate. (c) 1995 John Wiley & Sons, Inc.     

Simulating nitrogen response of irrigated rice

A dynamic model to simulate the growth and yield of irrigated, transplanted rice in relation to daily solar radiation, mean temperature and shoot nitrogen concentration was applied to rice crops in western Java, Indonesia.Observations of shoot nitrogen concentration throughout the life-cycles of experimental crops were used as input to the simulation. The experiments consisted of 23 treatments representing different forms of nitrogen fertilizer, and different rates, times and methods of application. The model accurately fitted the growth and yield of 12 of these treatments and was successfully tested on the 11 treatments which were not involved in the filting.The parts of the model dealing with nitrogen simulate daily growth as a non-linear function of nitrogen concentration of non-grain shoot tissue relative to upper and lower limits. During the grain-filling phase the model simulates the competition for plant nitrogen between grain and assimilating tissue.The model was used to simulate the effects of increases in nitrogen status of a rice crop in the environmental conditions of western Java. Simulations with the model suggest an interaction between the timing and amount of nitrogen accumulation in plant tissue, with little effect of timing on yield for small increases in nitrogen status, but an advantage for early over late application for large increases in nitrogen status.     

Continuous, real-time monitoring of the oxygen uptake rate (OUR) in animal cell bioreactors

A new method for real-time monitoring of the oxygen uptake rate (OUR) in bioreactors, based on dissolved oxygen (DO) measurement at two points, has been developed and tested extensively. The method has several distinct advantages over known techniques.It enables the continuous and undisturbed monitoring of OUR, which is conventionally impossible without gas analyzers. The technique does not require knowledge of k(L)a. It provides smooth, robust, and reliable signal. The monitoring scheme is applicable to both microbial and mammalian cell bioprocesses of laboratory or industrial scale. The method was successfully used in the cultivation of NSO-derived murine myeloma cell line producing monoclonal antibody. It was found that while the OUR increased with the cell density, the specific OUR decreased to approximately one-half at cell concentrations of 16 x 10(6) cells/mL, indicating gradual reduction of cell respiration activity. Apart from the laboratory scale cultivation, the method was applied to industrial scale perfusion culture, as well as to processes using other cell lines. (c) 1994 John Wiley & Sons, Inc.     

Breeding waterbird wetland habitat availability and response to water-level management in Saint John River floodplain wetlands, New Brunswick

Vegetated areas of rivers and estuaries are capable of affecting the concentration of dissolved and particulate matter in water masses traversing those plant beds. We examined whether different sizes of water chestnut (Trapa natans) beds in the Hudson River, USA, alter dissolved oxygen, nutrients and turbidity of water masses. Ebb–tide water was sampled from four water chestnut beds in the tidal freshwater portion of the Hudson River estuary and each site was sampled multiple times during the growing season and once following plant senescence. Water quality variables included dissolved oxygen, turbidity, dissolved organic carbon, and inorganic nutrients. Samples from the small beds (575 m² and 624 m²) were compared with large beds (16 600 m² and 24 820 m²). Dissolved oxygen of water flooding vegetated beds in the hour before high tide was 7.18±1.03 mg/l (mean±standard deviation) with a range of 5.5–9.8 mg/l throughout the growing season. Water samples collected as water ebbed from the plant beds showed that only the large beds had an effect on dissolved oxygen with the largest declines in oxygen exhibited by the largest bed. Decline of dissolved oxygen in the water ebbing from the largest bed averaged 1.5±0.4 mg/l/h with a minimum of 4.5 mg/l, equivalent to 54% of saturation, a level at which sensitive fauna are negatively affected. There were no significant relationships between bed size or plant presence and inorganic nutrients, turbidity or DOC. Ebb–tide nitrate was never lower than 87% of flood tide means. Effective management of invasive plants must consider both the variability in effects among plant beds and the areal coverage of plant bed sizes.     

苏云金杆菌溶氧控制发酵

利用BIOSTATC10自控发酵罐 ,研究了Bt菌种Gc - 91进行间歇培养时氧的供需特性。研究表明 ,以生产培养基配方进行发酵时 ,生长高峰期的临界氧浓度在DO12 .0 %～ 17.5%之间 ,控制溶氧接近于临界氧浓度进行发酵 ,Bt晶体含量和毒力效价有大幅提高。     

Effects of oxygen and nutrients limitation on ajmalicine production and related enzyme activities in high density cultures of Catharanthus roseus

Oxygen and nutrient limitation was investigated in order to identify the origin of a lower specific ajmalicine production in Catharanthus roseus cultures at high cell densities in an induction medium. The effect of oxygen limitation was explored by comparing two identically aerated and agitated high cell density bioreactor cultures with dissolved oxygen (DO) concentration of 15% and 85% of air saturation, with respect to alkaloid formation and related enzymes activities. Oxygen had an evident effect on ajmalicine production: in the high DO cultures production was more than 5 times higher than in the low DO cultures. The difference in ajmalicine production between high and low DO could not be explained by the enzyme activity profiles. Moreover, the productivity in the high density culture could not restored to the level of a low density culture (at a high DO) by increasing the DO alone. The effect of nutrient limitation was studied with response surface methodology in shake flask cultures. Nutrient limitation could not be demonstrated to be responsible for the productivity loss. Alkaloid and enzyme measurements in the shake flask cultures supported previous findings that the tryptamine pathway may regulate alkaloid production, provided that the terpenoid pathway is sufficiently active. (c) 1994 John Wiley & Sons, Inc.     

Factors governing the spatial and temporal distribution of Chironomid larvae in the Maarsseveen lakes with special emphasis on the role of oxygen conditions

Distribution patterns of the larvae of Chironomidae are compared in three water systems in The Netherlands, which vary in trophic state and oxygen regimes. The life cycles and flying periods of some dominant chironomid species in two of the investigated lakes, Lakes Maarsseveen I and II, are determined by comparing data on the seasonal variations in larval densities with existing literature on Chironomidae in the Maarsseveen lakes. In the oligo-mesotrophic Lake Maarsseveen I (LM I), hypoxic or anoxic conditions in the hypolimnion are observed only at the end of the stratification period. A clear zonation of the chironomid fauna is present in this lake. The littoral zone is dominated byCladotanytarsus gr.mancus andStictochironomus sticticus, the littoriprofundal zone byTanytarsus bathophilus, and the profundal zone byChironomus anthracinus. In comparison with the other species in LM I,T. bathophilus larvae show the most variable distribution patterns over time. Larvae are found in all depths from July to September, but disappear from the hypolimnion as soon as oxygen conditions deteriorate. In the eutrophic Lake Maarsseveen II (LM II), oxygen depletion of the hypolimnion starts immediately after the onset of the thermal stratification in June, and continues until autumnal turnover in November. In this lake, the chironomid community consists primarily ofS. sticticus andCl. gr.mancus, and is confined to the narrow littoral zone. No chironomid larvae are found in the deeper parts of the lake. The eutrophic Lake Gijster in the Brabantse Biesbosch is a deep, man-made reservoir, that is artificially destratified during the summer. In this lakeTanytarsus bathophilus is found in the profundal sediments, whereas almost noChironomus is found in this zone. It is concluded that oxygen conditions existing in the deeper regions of the investigated lakes in large part determine the occurrence and distribution of chironomid species. The distribution ofT. bathophilus is limited by unfavorable oxygen conditions and not by the trophic state of the lake. These findings are part of a thesis (HEINIS, 1993).