scholarly journals The Species-Specific Responses of Freshwater Diatoms to Elevated Temperatures Are Affected by Interspecific Interactions

2018 ◽  
Vol 6 (3) ◽  
pp. 82 ◽  
Author(s):  
Yun Zhang ◽  
Chengrong Peng ◽  
Zhicong Wang ◽  
Jinli Zhang ◽  
Lijie Li ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Interspecific Interactions ◽  
Seasonal Succession ◽  
Early Spring ◽  
Mixed Cultures ◽  
Specific Response ◽  
Diatom Species ◽  
Interspecies Interactions ◽  
Spring Warming ◽  
Temperature Ranges

Numerous experimental simulations with different warming scenarios have been conducted to predict how algae will respond to warming, but their conclusions are sometimes contradictory to each other. This might be due to a failure to consider interspecific interactions. In this study, the dominant diatom species in a seasonal succession were isolated and verified to adapt to different temperature ranges by constant temperature experiment. Both unialgal and mixed cultures were exposed to two fluctuant temperature treatments that simulated the temperature variations from early spring to summer, with one treatment 4 °C higher (warming scenario) than the other. We found that the specific response of diatoms to warming was affected by interspecific interactions. Spring warming had no significant effect on eurythermal species and had a positive effect on the abundance of warm-adapted diatom species, but interspecific interactions reduced this promotional effect. Cold-adapted species had a negative response to spring warming in the presence of other diatom species but had a positive response to early spring warming in the absence of interspecific interactions. In addition, warming resulted in the growth of all diatom species peaking earlier in unialgal cultures, but this effect could be weakened or amplified by interspecies interactions in mixed cultures. Our results suggest that the specific diatom species with different optimal growth temperature ranges responding to warming were expected if there were no interspecific interactions. However, in natural environments, the inevitable and complex interspecific interactions will influence the responses of diatoms to warming. This important factor should not be ignored in the prediction of organism responses to climate warming.

Postemergence Control of Italian Ryegrass in Hazelnut Orchards

2021 ◽  
pp. 1-22
Author(s):  
Marcelo L. Moretti
Keyword(s):  
Weed Control ◽  
Weed Management ◽  
Field Studies ◽  
Early Spring ◽  
Italian Ryegrass ◽  
Specific Response ◽  
Record Keeping ◽  
Effective Option ◽  
Contrast Analysis ◽  
Herbicide Use

Abstract Italian ryegrass has become a problematic weed in hazelnut orchards of Oregon because of the presence of herbicide-resistant populations. Resistant and multiple-resistant Italian ryegrass populations are now the predominant biotypes in Oregon; there is no information on which herbicides effectively control Italian ryegrass in hazelnut orchards. Six field studies were conducted in commercial orchards to evaluate Italian ryegrass control with POST herbicides. Treatments included flazasulfuron, glufosinate, glyphosate, paraquat, rimsulfuron, and sethoxydim applied alone or in selected mixtures during early spring when plants were in the vegetative stage. Treatment efficacy was dependent on the experimental site. The observed range of weed control 28 d after treatment was 13 to 76 % for glyphosate, 1 to 72% for paraquat, 58 to 88% for glufosinate, 16 to 97 % for flazasulfuron, 8 to 94% for rimsulfuron, and 25 to 91% for sethoxydim. Herbicides in mixtures improved control of Italian ryegrass compared to single active ingredients based on contrast analysis. Herbicides in mixture increased control by 27% compared to glyphosate, 18% to rimsulfuron, 15% to flazasulfuron, 19% to sethoxydim, and 12% compared to glufosinate when averaged across all sites, but mixture not always improved ground coverage of biomass reduction. This complex site-specific response highlights the importance of record-keeping for efficient herbicide use. Glufosinate is an effective option to manage Italian ryegrass. However, the glufosinate-resistant biotypes documented in Oregon may jeopardize this practice. Non-chemical weed control options are needed for sustainable weed management in hazelnuts.

scholarly journals Effects of climate change on fish reproduction and early life history stages

2011 ◽  
Vol 62 (9) ◽  
pp. 1015 ◽  
Author(s):  
Ned W. Pankhurst ◽  
Philip L. Munday
Keyword(s):  
Climate Change ◽  
Elevated Temperatures ◽  
Endocrine System ◽  
Developmental Rate ◽  
Early Life History ◽  
Egg Survival ◽  
Life History Stages ◽  
Larval Fishes ◽  
Larval Behaviour ◽  
Temperature Ranges

Seasonal change in temperature has a profound effect on reproduction in fish. Increasing temperatures cue reproductive development in spring-spawning species, and falling temperatures stimulate reproduction in autumn-spawners. Elevated temperatures truncate spring spawning, and delay autumn spawning. Temperature increases will affect reproduction, but the nature of these effects will depend on the period and amplitude of the increase and range from phase-shifting of spawning to complete inhibition of reproduction. This latter effect will be most marked in species that are constrained in their capacity to shift geographic range. Studies from a range of taxa, habitats and temperature ranges all show inhibitory effects of elevated temperature albeit about different environmental set points. The effects are generated through the endocrine system, particularly through the inhibition of ovarian oestrogen production. Larval fishes are usually more sensitive than adults to environmental fluctuations, and might be especially vulnerable to climate change. In addition to direct effects on embryonic duration and egg survival, temperature also influences size at hatching, developmental rate, pelagic larval duration and survival. A companion effect of marine climate change is ocean acidification, which may pose a significant threat through its capacity to alter larval behaviour and impair sensory capabilities. This in turn impacts on population replenishment and connectivity patterns of marine fishes.

Seasonal succession of diatom epiphyton on dense mats of Lemna minor

1985 ◽  
Vol 63 (12) ◽  
pp. 2332-2339 ◽  
Author(s):  
L. G. Goldsborough ◽  
G. G. C. Robinson
Keyword(s):  
Lemna Minor ◽  
Algal Growth ◽  
Seasonal Succession ◽  
Ambient Air ◽  
Early Spring ◽  
Early Summer ◽  
Algal Community ◽  
Light Limitation ◽  
Total Biomass

Annual sequences of biomass, species diversity, and community composition of epiphytic diatoms on a dense mat of Lemna minor L. growing in a freshwater marsh are described. In 2 successive years, maximum biomass occurred in early spring prior to occlusion of the water surface by the mat, while diversity reached relative maxima in the early summer (during a period of declining total biomass) and late fall. Ambient air temperature (possibly through a relationship with in situ metabolic activity and nutrient availability) was significantly correlated with community ordination scores on a temporal basis. Depth profile maxima of diatom abundance on vertically positioned artificial substrata occurred below the mat, suggesting that light limitation of algal growth within dense mats may be of lesser importance. Dominant diatom species in the spring and fall were generally ubiquitous in the surrounding marsh, while the major taxa in midsummer, Achnanthes hungarica, Amphora veneta, and Navicula twymaniana, may be specific to the Lemna microhabitat. The development of algal community specificity within a defined seasonal range is discussed in terms of the relative importance of host exudates versus exogenous nutrients as the basis for algal-substratum associations.

Cycles vitaux de quelques Plécoptères des Laurentides (insectes)

1969 ◽  
Vol 47 (4) ◽  
pp. 483-494 ◽  
Author(s):  
Peter Harper ◽  
Etienne Magnin
Keyword(s):  
Larval Growth ◽  
Seasonal Succession ◽  
Single Species ◽  
Common Species ◽  
Early Spring ◽  
The Other ◽  
Paragnetina Media

Twenty-four species of stoneflies (Plecoptera) were collected in the streams of the Station de Biologie de l'Université de Montréal, at Saint-Hippolyte in Terrebonne county (46°00′ N, 74°00′ W). Sampling of larvae and adults at regular intervals showed the distribution of the species in the stream and the seasonal succession of the adults. The Capniidae and the Taeniopterygidae appear in early spring; the remaining species emerge in May and June. The emergence of a single species Leuctra tenuis extends into July and August. No true autumnal species was found. Larval growth of the more common species is described; these are Taeniopteryx burksi, Paracapnia opis, Isoperla frisoni, Isoperla lata, Hastaperla brevis, and Paragnetina media. Biological notes concerning the other species are included.

scholarly journals Dynamic interspecies interactions and robustness in a four-species model biofilm

2021 ◽  
Author(s):  
Aurélie Baliarda ◽  
Michèle Winkler ◽  
Laurent Tournier ◽  
Colin Tinsley ◽  
Stéphane Aymerich
Keyword(s):  
Mutational Analysis ◽  
Interspecific Interactions ◽  
Bacterial Species ◽  
Species Abundance ◽  
Growth Dynamics ◽  
Equilibrium Composition ◽  
Interspecies Interactions ◽  
Molecular Determinant ◽  
And Function ◽  
Final Composition

Interspecific interactions within biofilms determine relative species abundance, growth dynamics, community resilience, and success or failure of invasion by an extraneous organism. However, deciphering interspecific interactions and assessing their contribution to biofilm properties and function remain a challenge. Here, we describe the constitution of a model biofilm composed of four bacterial species belonging to four different genera (Rhodocyclus sp., Pseudomonas fluorescens, Kocuria varians, and Bacillus cereus), derived from a biofilm isolated from an industrial milk pasteurization unit. We demonstrate that the growth dynamics and equilibrium composition of this biofilm are highly reproducible. Based on its equilibrium composition, we show that the establishment of this 4-species biofilm is highly robust against initial, transient perturbations but less so towards continuous perturbations. By comparing biofilms formed from different numbers and combinations of the constituent species and by fitting a growth model to the experimental data, we reveal a network of dynamic, positive, and negative interactions that determine the final composition of the biofilm. Furthermore, we reveal that the molecular determinant of one negative interaction is the thiocillin I synthesized by the B. cereus strain, and demonstrate its importance for species distribution and its impact on robustness by mutational analysis of the biofilm ecosystem.

Epoxy Resin Exhibits Long-Term Durability and Chemical Stability as a Well Sealant

2021 ◽  
Author(s):  
Fred Sabins ◽  
Allen Apblett ◽  
Randall Shafer ◽  
Larry Watters
Keyword(s):  
Epoxy Resin ◽  
Fresh Water ◽  
Chemical Stability ◽  
Elevated Temperatures ◽  
Mechanical Degradation ◽  
Gravimetric Analysis ◽  
Degradation Reactions ◽  
Temperature Ranges ◽  
One Year

Abstract The necessity to verify epoxy resin sealant's reliability for well applications is amplified as its use increases. Limited data exists to confirm resin's long-term durability or chemical stability under exposure to well fluids at temperature and pressure. This paper presents laboratory results illustrating durability and stability of epoxy resin exposed to a range of well fluids over a span of temperatures. Additionally, results of accelerated thermal degradation testing further quantify long-term thermal and chemical stability. Epoxy resins formulated for a range of remedial and abandonment applications were cured in fresh water, CaCl2 brine, and hydrocarbon at 170°F up to one year. Additional samples cured in fresh water and water containing CO2 and H2S at elevated temperatures (220°F to 320°F) for up to six weeks to produce accelerated degradation reactions allowed the assessment of resin degradation verses temperature. Thermal Gravimetric Analysis (TGA) evaluated chemical and mechanical degradation verses time at temperatures ranging from 200°C to 400°C. Arrhenius calculations were performed to forecast long term stability of resins across their intended temperature ranges. Resulting data were analyzed to develop an inclusive assessment of resin stability and durability in well environments. Results indicate properly formulated epoxy resin is a mechanically, chemically, and thermally durable sealant for well applications.

Intra- and interspecific competition between biotypes B and Q of Bemisia tabaci (Hemiptera: Aleyrodidae) from Spain

2004 ◽  
Vol 94 (4) ◽  
pp. 369-375 ◽  
Author(s):  
S. Pascual ◽  
C. Callejas
Keyword(s):  
Sex Ratio ◽  
Interspecific Competition ◽  
Bemisia Tabaci ◽  
Interspecific Interactions ◽  
Developmental Rate ◽  
Mixed Cultures ◽  
Progeny Size ◽  
Moderate Effect ◽  
Single And Mixed Cultures ◽  
Biotype B

AbstractBiotypes B and Q of Bemisia tabaci (Gennadius), collected from the islands of Tenerife and Majorca respectively, were exposed to competition conditions on tomato cv. Marmande in the laboratory. Both biotypes were established in single and mixed cultures at different densities. Increased mortality of biotype Q females and immature instars was observed together with a lower rate of fecundity and progeny size compared to biotype B, when reared in single or mixed cultures. The female:male sex ratio of F1 individuals of biotype Q was higher in single than in mixed cultures. However, the sex ratio of F1 individuals of biotype B was the same in single and mixed cultures, suggesting reproductive interference. Whitefly density did not affect interspecific interactions. It had a moderate effect on developmental rate of both biotypes, and on mortality of immature instars and progeny size of biotype B only. The results indicate that under laboratory conditions the studied biotype B should displace biotype Q.

scholarly journals The Temperature Gradient-Forming Device, an Accessory Unit for Normal Light Microscopes To Study the Biology of Hyperthermophilic Microorganisms

2014 ◽  
Vol 80 (15) ◽  
pp. 4764-4770 ◽  
Author(s):  
Maximilian Mora ◽  
Annett Bellack ◽  
Matthias Ugele ◽  
Johann Hopf ◽  
Reinhard Wirth
Keyword(s):  
Temperature Gradient ◽  
Elevated Temperatures ◽  
Strictly Anaerobic ◽  
Heating Rates ◽  
Content Type ◽  
Custom Made ◽  
Temperature Ranges ◽  
Limited Degree ◽  
Normal Light ◽  
First Time

ABSTRACTTo date, the behavior of hyperthermophilic microorganisms in their biotope has been studied only to a limited degree; this is especially true for motility. One reason for this lack of knowledge is the requirement for high-temperature microscopy—combined, in most cases, with the need for observations under strictly anaerobic conditions—for such studies. We have developed a custom-made, low-budget device that, for the first time, allows analyses in temperature gradients up to 40°C over a distance of just 2 cm (a biotope-relevant distance) with heating rates up to ∼5°C/s. Our temperature gradient-forming device can convert any upright light microscope into one that works at temperatures as high as 110°C. Data obtained by use of this apparatus show how very well hyperthermophiles are adapted to their biotope: they can react within seconds to elevated temperatures by starting motility—even after 9 months of storage in the cold. Using the temperature gradient-forming device, we determined the temperature ranges for swimming, and the swimming speeds, of 15 selected species of the genusThermococcuswithin a few months, related these findings to the presence of cell surface appendages, and obtained the first evidence for thermotaxis inArchaea.

Interactions of Pseudomonas aeruginosa in predominant biofilm or planktonic forms of existence in mixed culture with Escherichia coli in vitro

2013 ◽  
Vol 59 (9) ◽  
pp. 604-610 ◽  
Author(s):  
Marina V. Kuznetsova ◽  
Irina L. Maslennikova ◽  
Tamara I. Karpunina ◽  
Larisa Yu. Nesterova ◽  
Vitaly A. Demakov
Keyword(s):  
Escherichia Coli ◽  
Pseudomonas Aeruginosa ◽  
Total Concentration ◽  
Single Species ◽  
Mixed Cultures ◽  
Interspecies Interactions ◽  
E Coli ◽  
Predominant Form ◽  
The One

Pseudomonas aeruginosa and Escherichia coli are known to be involved in mixed communities in diverse niches. In this study we examined the influence of the predominant form of cell existence of and the exometabolite production by P. aeruginosa strains on interspecies interactions, in vitro. Bacterial numbers of P. aeruginosa and E. coli in mixed plankton cultures and biofilms compared with their numbers in single plankton cultures and biofilms changed in a different way, but were in accordance with the form of P. aeruginosa cell existence. The mass of a mixed-species biofilm was greater than the mass of a single-species biofilm. Among the mixed biofilms, the one with the “planktonic” P. aeruginosa strain had the least biomass. The total pyocyanin and pyoverdin levels were found to be lower in all mixed plankton cultures. Despite this, clinical P. aeruginosa strains irrespective of the predominant form of existence (“biofilm” or “planktonic”) had a higher total concentration of exometabolites than did the reference strain in 12–24 h mixed cultures. The metabolism of E. coli, according to its bioluminescence, was reduced in mixed cultures, and the decrease was by 20- to 100-fold greater with the clinical Pseudomonas strains than the reference Pseudomonas strain. Thus, both the predominant form of existence of and the exometabolite production by distinct P. aeruginosa strains should be considered to fully understand the interspecies relationship and bacteria survival in natural communities.

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