The effect of environmental factors on coliphages in the Welsh River Dee

In a l-year study at Ironbridge on the Welsh River Dee the Escherichia coli popu-lation varied over a 200-fold range and the coliphage populations grown at 37°C (H. T. phage) and at 22°C (L. T. phage) each varied by over 100-fold. Both the E. coli and H. T. phage counts were shown to have highly signiflcant seasonal fluctuations, which included troughs in summer and peaks in winter. The L. T. phage count appeared to maintain a baseline population in summer and had a 20-fold less sig-nificant association with temperature than the H. T. phage population.     

The effect of various environmental factors on the ethidium monazite and quantitative PCR method to detect viable bacteria

Aims: Ethidium monoazide in combination with quantitative PCR (EMA–qPCR) has been considered as a promising method to enumerate viable cells; however, its efficacy can be significantly affected by disinfection conditions and various environments. In this study, thermal disinfection, osmotic pressure and acids with different pH values were systematically investigated to achieve the optimum conditions. Methods and Results: EMA treatment of pure cultures at low concentration (10 μg ml^?1) for 20 min resulted in effective differentiation between viable and nonviable bacteria and had no effect on viable cells. Heating at 85°C for 35 min was the optimum condition that yields inactivated Escherichia coli (E. coli) cells that were not detected with EMA–qPCR. Performing EMA treatment in high‐salt ion environment (sodium chloride concentration ≥4%) could weaken EMA inhibition effect. Both strong and weak acid solutions could react with EMA, change its absorption spectra and influence EMA inhibition effect. Because of the sublethal acidification injury, underestimation of cell counts were found using EMA–qPCR method, and 40‐min incubation in Luria–Bertani medium could completely offset this error. Conclusion: Our results provided optimum EMA treatment, thermal disinfection and environment conditions for EMA–qPCR and demonstrated the feasibility of this method when enumerating viable cells under varied osmotic pressure and pH environment. Significance and Impact of the Study: Optimum EMA treatment, thermal disinfection and EMA‐treated environment will be successfully applied in EMA–qPCR. Osmotic pressure and acid‐induced injury can be detected by EMA–qPCR with optimization.     

The effect of cosmo-helio-geophysical factors on the agglutination of bacteria in vitro

A correlation between intensity of neutronal component of cosmic rays and typhoid bacteria agglutination was revealed. Agglutination speed dependence on season, polarity of interplanetary magnetic field, geomagnetic storms, Sun's revolution was shown. An assumption is made about an important role of the magnetic fields in the phenomena observed.     

The effect of environmental factors on estimated viable and total populations of planktonic bacteria in lakes and experimental enclosures

SUMMARY. The difference between the results of viable and total counting procedures for bacteria are exemplified by vertical profiles from a deep and a shallow lake and from seasonal changes in the epilimnion and hypolimnion of a shallow eutrophic lake. The viable count was, on average, 0.25% of the total count, the greatest difference being noted in the anoxic hypolimnion, probably due to the inadequacy of the viable counting procedure for the isolation of bacteria from such samples. There was a general trend for the more nutrient-rich waters to support larger bacterial populations but such observations did not provide any further information on the factors responsible for the population changes observed. Seasonal fluctuations in the counts are studied and the qualitative and quantitative changes resulting from artificial enclosure of water are discussed. Not all the temporal changes could be explained and short-term changes resulting from nutrient additions to the experimental enclosures were not always reproducible. Horizontal variability was examined, found to be significant and could play an important role where water movement and turbulence is considerable. Results from six sites sampled between 1969 and 1974, representing total and viable bacterial population estimates and a total of eighteen independent or regressor variables were then subjected to principal components analysis. Results taken from the whole water column showed the overwhelming effect of the process of stratification on the bacterial population accounting for 30%-60% of its variability. Secondary components representing algal productivity could account for 10% to 20% of the variability. Many of the chosen regressor variables were acting as measures of the same phenomenon without providing significant information on what affected the bacterial population. To overcome this problem results from the hypolimnion and epilimnion were analysed separately. The analysis demonstrated the importance of seasonal changes in nutrient concentrations in the epilimnion and the development of anoxic conditions in the hypolimnion. Algal biomass, phosphate concentration and the interaction of pH and ammonia appeared to be important. It was concluded that most of the variability in the bacterial population estimates could have been explained by five of the regressor variables and that the factors most likely to provide more information would include some measure of predation and lake retention time.     

The effect of unfavorable environmental factors on the mother-fetus system]

The paper provides a generalization of data and the results of own experiments with Wistar rats in the conditions of hypokinesia, immobilization, water deprivation, hypergravity, weightlessness and other factors affecting mother and fetus as a system. It gives a comparison of reactivity of pregnant and non-pregnant animals under stress, and also of the effects of unfavorable impacts sustained during various phases of ontogenesis: in pubertation period, directly before pregnancy and during various phases of pregnancy. It demonstrated that exposition of pregnant animals to unfavorable conditions is accompanied by significant stress of the compensatory-adaptive possibilities of mother aiming to support of homeostasis of the developing fetus. Clear changes develop in fetus only in case the adaptive possibilities of mother turn out inadequate or when the developing organs of fetus become active components of adaptive reaction of mother-fetus system and compensate for functional inadequacy of some mother's organ. The paper discusses the problem of individual features of resistivity and reactivity.     

The effect of environmental factors on circulation and respiration in teleost fish

Summary Anesthesia, handling and activity can produce large variations in some of the parameters of circulation and breathing movements in fish. Handling and MS222 anesthesis cause a large increase in heart rate in the tench, but have the reverse effect on the trout. Hypoxia causes a decreased heart rate and changes in dorsal aortic blood pressure. Serial sampling of the blood appears to have little effect on the parameters of circulation if the blood is replaced with saline. Removal of blood without replacement causes a decrease in blood pressure and a slowing of the heart. It is suggested that much of the variability observed in the measurement of circulatory parameters in fish can be accounted for by the experimental procedure, rather than demonstrating large inter-specific variations in teleost fish.     

The effect of environmental factors on floating fresh marsh end-of-season biomass

We used both stepwise and quantile regression to determine the sources of environmental variation that explained the observed inter-annual variation in end-of-season freshwater floating marsh aboveground biomass over an 18-year period. The vegetation at our study site had high species diversity with an average of 20 species recorded from 10 0.25 m⁻² plots. However, Panicum hemitomon was clearly the dominant contributing 74% of the total biomass. Only three other species (Solidago sempervirens, Vigna luteola, and Thelypteris palustris) were so common that they were sampled in all years. We expected that the most important factors controlling interannual variation in aboveground biomass are temperature and nitrogen availability. We also expected that nitrogen availability to the plants is affected by water movement through and under the mat driven by precipitation (lower N), evaporation (transportation of higher N waters to roots), and local runoff (higher N). Stepwise regression analysis indicated that P. hemitomon average biomass was negatively related to average water level and positively related to maximum water level and had a curvilinear response with TKN. Using quantile regression the best fit for P. hemitomon maximum-biomass with two parameters was obtained using hot days (positive relationship) and maximum water level (negative relationship). Both analytical methods showed maximum water level (negative relationship) and cold front passage (positive relationship) to be the environmental parameters that best explained interannual variation in S. sempervirens biomass. V. luteola biomass was positively related to temperature. Stepwise regression added chloride concentration as an additional positive parameter explaining V. luteola biomass, while quantile regression identified nitrogen as an important positive parameter. Both analytical methods identified pH, TKN, and water level as environmental parameters that were negatively correlated with T. palustris biomass. The overall negative effect of water level on all species was unexpected in this floating mat system. We initially assumed that higher water levels were due to higher runoff which should have a positive effect on biomass. However, higher water levels may also be related to a higher retention time in this fresh-water tidal system, which decreases water exchange and nutrient replenishment.     

The environmental significance of Lingula in the Ludlow Series of the Welsh Borderland and Wales

Cherns. Lesley 1979 01 15: The environmental significance of Lingula in the Ludlow Series of the Welsh Borderland and Wales. Lethaia . Vol. 12. pp. 35–46, Oslo. ISSN 0024–1164.
The inarticulate brachiopod Lingula is commonly regarded as an indicator of very nearshore environments, particularly when found in monospecific assemblages. However, neither of the two common species in the Lower Leintwardine Beds, L. lewisii and L. lata . which occur commonly in such associations, have distributions indicative of such an environment. Their Occurrence correlates closely with the Leintwardinian palaeogeography. The former species is concentrated in shelf areas, the latter is confined to the basin; the two distributions overlap little. Individuals of both species are found articulated and perpendicular to the bedding, apparently in situ . Hence, the species may be inferred to have equivalent, infaunal modes of life comparable to living representatives of the family. The basinal distribution of L. lara is an original feature. The depth of the actively subsiding basin was relatively great, judging from sedimentological and palaeogeographical evidence. Therefore, L. lata was a species adapted to 'deep-water' environments. The lingulid distributions, reviewed against the concept of brachiopod depth-related communities previously defined for the Ludlow show the latter to be inapplicable in the Leintwardinian. The depth significance postulated for the recurrent species associations typical of the shelf sequences cannot be accepted.     

Life history changes in Atlantic salmon from the River Dee,Wales

The change in life history of Atlantic salmon (Salmo salar L.) on the River Dee over the last 60 years is described. Over the last 60 years, salmon have shown a change in run timing, the majority currently entering the river between August and October compared with prior to June. This has coincided with a change in the sea age composition, which was dominated by multi-sea winter salmon prior to the 1980s after which the proportion of 1sea-winter fish increased until they now dominate the mature population. Growth rates of salmon in fresh water remained relatively stable until the mid-1980s and then increased. By the end of the 1990s juvenile salmon were, by the end of their first and second year, respectively, ∼60 and ∼19%, on average, larger than they were between the late 1930s and mid-1980s. This has been reflected in a change in the age composition of smolts where the mean smolt age has declined from ∼2 years prior to the 1980s to ∼1.6 years in the late 1990s. There was no observed trend in post-smolt (marine) growth for salmon. Size at return for 1SW salmon appeared stable while there is some evidence of an increase in mean length of 2SW salmon at the end of the 1990s. A steady state life history model was developed which suggests an increase in the instantaneous rate of mortality by 2.9% from 1.495 year⁻¹ in 1937/1938 to 1.538 year⁻¹ in 1967/1969 and by 21.6% to 1.870 year⁻¹ in 1997/1999. This is considered to explain the shift in mean age at maturity from 5.2 to 4.8 to 3.9 years for the three periods examined. There is close agreement between the observed mean age at maturity and that predicted by the model suggesting optimal lifetime reproductive success. Guest editors: S. Dufour, E. Prévost, E. Rochard & P. Williot Fish and diadromy in Europe (ecology, management, conservation)     

The effect of physicochemical environmental factors on the growth of gram-positive bacterial dissociants]

The growth of R-, S- and M (g)-dissociants of Streptococcus lactis, Bacillus coagulans, Rhodococcus rubropertinctus under the action of some physico-chemical factors: temperature, pH, ultraviolet (UV) rays, high concentration of NaCl and storage have been compared. R-variants gain selective advantage under the influence of UV-irradiation, high temperature and storage; S-variants--at decreasing of active pH of medium; M (g)-variants--at decreasing of growth temperature, high values of pH, increased NaCl concentration. The dissociation has been concluded to enlarge the limits of the species survival.     

The effect of size-dependent growth and environmental factors on animal size variability

The origin of variation in animal growth rate and body size is not well understood but central to ecological and evolutionary processes. We develop a relationship that predicts the change in relative body size variation within a cohort will be approximately equal to the relative change in mean per unit size growth rate, when only size-dependent factors affect growth. When modeling cohort growth, relative size variation decreased, remained unchanged, or increased, as a function of growth rate-size scaling relationships, in a predictable manner. We use the approximation to predict how environmental factors (e.g., resource level) affect body size variation, and verified these predictions numerically for a flexible growth model using a wide range of parameter values. We also explore and discuss the assumptions underlying the approximation. We find that factors that similarly affect mean growth rate may differently affect size variation, and competition may increase body size variation without changing size-independent relationships. We discuss implications of our results to the choice of growth equations used in models where body size variation is an important variable or output.     

The combined effect of environmental and host factors on the emergence of viral RNA recombinants

Viruses are masters of evolution due to high frequency mutations and genetic recombination. In spite of the significance of viral RNA recombination that promotes the emergence of drug-resistant virus strains, the role of host and environmental factors in RNA recombination is poorly understood. Here we report that the host Met22p/Hal2p bisphosphate-3'-nucleotidase regulates the frequency of viral RNA recombination and the efficiency of viral replication. Based on Tomato bushy stunt virus (TBSV) and yeast as a model host, we demonstrate that deletion of MET22 in yeast or knockdown of AHL, SAL1 and FRY1 nucleotidases/phosphatases in plants leads to increased TBSV recombination and replication. Using a cell-free TBSV recombination/replication assay, we show that the substrate of the above nucleotidases, namely 3'-phosphoadenosine-5'-phosphate pAp, inhibits the activity of the Xrn1p 5'-3' ribonuclease, a known suppressor of TBSV recombination. Inhibition of the activity of the nucleotidases by LiCl and NaCl also leads to increased TBSV recombination, demonstrating that environmental factors could also affect viral RNA recombination. Thus, host factors in combination with environmental factors likely affect virus evolution and adaptation.     

Influence of environmental factors on reductive bioprecipitation of uranium by sulfate reducing bacteria

Microbial reduction of soluble uranyl [U (VI)] to insoluble uraninite by sulfate reducing bacteria (SRB) is a promising remediation strategy for uranium-contaminated groundwater. Effects of environmental factors, including pH and coexisting ions, on U (VI) bioreduction processes (UBP) remain unknown. Anaerobic batch experiments were performed to evaluate impact on UBP. Kinetic investigations with varied pH demonstrated that U (VI) was reduced mostly within 48 h. The bioprecipitation yields depended strongly on pH, increasing from 12.9% to 99.4% at pH 2.0 and 6.0, respectively. Sulfate concentration 4000 mg l⁻¹ did not affect UBP; however, sulfate concentration 5000 mg l⁻¹ significantly slowed UBP. Biogenic H₂S produced during sulfate reduction was not directly involved in UBP. At 20 mg l⁻¹ Zn or 10 mg l⁻¹ Cu, no UBP inhibition was observed and uraninite was detected in metal sulfide precipitate. However, 25 mg l⁻¹ Zn or 15 mg l⁻¹ Cu stopped UBP completely. Cu toxicity mechanism probably differed from Zn. The ability to reduce U (VI) was lost permanently with exposure to 15 mg l⁻¹ Cu, but not for Zn 25 mg l⁻¹. No uraninite could be detected before nitrate removal, suggesting nitrate strongly inhibited UBP, which may possibly be related to denitrification intermediates controlling the solution redox potential.     

The ordination of benthic invertebrate communities in the South Platte River Basin in relation to environmental factors

1. Spatial patterns of benthic-invertebrate communities were examined in the 62 900 km² South Platte River Basin in Colorado, Nebraska and Wyoming, U.S.A., to determine major environmental factors associated with invertebrate distribution. Stable substrates were sampled semiquantitalively for invertebrates from 27 July to 7 August 1992, at twenty-one sites. Data on physical and chemical variables were collected concurrently at each site. 2. Four site groups were identified using derrended correspondence analysis (DCA), one in the mountains and three in the plains (braided channels, tributaries near the confluence with the main stem, and sites affected by effluent from wastewater-treatment plants). DCA axis 1 separated sites into the two major ecoregions (Southern Rocky Mountains and Western High Plains), and regression of DCA axis 1 with environmental variables indicated significant relationships primarily with slope, water temperature, specific conductance, and concentrations of organic nitrogen + ammonia and total phosphorus in surface water. Regression of DCA axis 2 with environmental variables indicated significant relationships with channel width and concentrations of nitrate + nitrite in surface water. 3. Invertebrate community composition and structure varied between ecoregions with greater number of taxa and number of insect families in mountain streams than in plains streams. Within an ecoregion, land use affected the invertebrate community. 4. Factors affecting invertebrate community distribution in stream ecosystems are scale dependent.