Structural Organization and Species Composition of a Lotic Periphyton Community in Response to Experimental Acidification

1989 ◽  
Vol 46 (5) ◽  
pp. 827-835 ◽  
Author(s):  
Dolors Planas ◽  
Louise Lapierre ◽  
Guy Moreau ◽  
Martine Allard
Keyword(s):  
Community Structure ◽  
Species Composition ◽  
Cell Density ◽  
Structural Organization ◽  
Spatial Organization ◽  
Algal Cell ◽  
Periphyton Community ◽  
Experimental Acidification ◽  
Density And Biomass ◽  
And Control

Changes in species composition, richness, diversity, biomass (biovolume), and spatial community structure of a lotic periphyton community were observed under experimental acidification (mean pH 4.5) with and without aluminum, in troughs fed from an oligo-dystrophic creek (mean pH 6.7). in experimental and control troughs, the community was dominated by diatoms throughout the treatment. Achnanthes linearis was dominant in all troughs before treatment as well as in the control during the experiment. Eunotia pectinalis, which was rare in all troughs before treatment, became dominant in the acidified troughs. After 3 mo of acidification, algal cell density and biomass were respectively 30 and 40–70 times higher in the treated troughs as compared with that in the control. The Sow diversity (H = 1.45–2.30) characteristic of the control trough, increased to 3.3 in the treated troughs after 1 mo of acidification, but after 3 mo of experiment the diversity was slightly lower in experimental troughs. In the control trough, spatial organization of the community was characterized by monolayered arrangements during the whole experiment, in both acidified troughs (acid and acid plus aluminum) the community became multilayered (3–4 layers). The increased complexity of the community in the acidified troughs seemed to be related to a decrease in the abundance of grazers in the periphytic community, mainly the collector–gatherers Ephemeroptera and Orthocladiinae.

Changes in Periphytic Algae Following Bicarbonate Additions to a Small Stream

1973 ◽  
Vol 30 (12) ◽  
pp. 1882-1884 ◽  
Author(s):  
M. Dickman
Keyword(s):  
Species Composition ◽  
Sodium Bicarbonate ◽  
Green Algae ◽  
Standing Crop ◽  
Small Stream ◽  
Periphytic Algae ◽  
Periphyton Community ◽  
Filamentous Green Algae ◽  
Glass Slides ◽  
And Control

Additions of less than 50 mg/liter sodium bicarbonate significantly increased algal standing crop on glass slides exposed in the treated portion of a small stream during a 2-month period. Filamentous green algae dominated the periphyton community of both bicarbonate treated and control slides when the study was terminated after 63 days. A slight shift in species composition toward the Cyanophycea on the bicarbonate treated slides was also noted.

scholarly journals Community structure of periphytic Zygnematophyceae (Streptophyta) in urban eutrophic ponds from central Brazil (Goiânia, GO)

2018 ◽  
Vol 30 (0) ◽  
Author(s):  
Francielle Karla Lopes da Silva ◽  
Bárbara Medeiros Fonseca ◽  
Sirlene Aparecida Felisberto
Keyword(s):  
Electrical Conductivity ◽  
Community Structure ◽  
Species Composition ◽  
Frequency Of Occurrence ◽  
Substrate Type ◽  
High Similarity ◽  
Central Brazil ◽  
Periphyton Community ◽  
Determinant Factor ◽  
Eutrophic Ponds

Abstract Aim This study aimed to investigate the community structure of Zygnematophyceae algae in the periphyton of nine shallow urban eutrophic ponds from central Brazil. Additionally, we compared two different substrates, hypothesizing that community structure attributes (chlorophyll a; Zygnematophyceae density, composition and richness) would differ between them. Methods Samples were carried out in August 2014. Periphyton was collected from two different substrates, macrophyte (epiphyton) and rocks (epilithon). Results The ponds presented pH ranging from neutral to slightly acidic and electrical conductivity in general higher than 60 µS.cm-1. Zygnematophyceae contributed with 0.82% of total periphyton community density in the epiphyton and 0.02% in the epilithon. Altogether 49 Zygnematophyceae taxa were recorded, distributed in 13 genera. Based on frequency of occurrence, most taxa were classified as rare, being present in less than 25% of the ponds. The taxa with higher densities were Cosmarium regnesii var. regnesii, Cosmarium abbreviatum var. minus, and Mougeotia sp. 3. When each pond was considered individually, other taxa were highlighted as the most abundant among Zygnematophyceae. It was the case of Staurastrum smithii, Cosmarium exiguum, Mougeotia sp. 1 and Mougeotia sp. 2. The two ponds with highest Zygnematophyceae density showed high similarity in the species composition (>70%); however, among the others, it was relatively low (<50%). Conclusions The eutrophic ponds considered in this study presented high periphytic biomass, but with low Zygnematophyceae representativeness. The periphyton attributes were not significantly different between macrophytes and rocks. The substrate type was not a determinant factor for Zygnematophyceae periphytic algae in the studied ponds.

Changes in the Population Density of Pathogenic Microorganisms in Response to the Allelopathic Effect of Thypha Latifolia

2014 ◽  
Vol 1 (1) ◽  
pp. 31-36 ◽  
Author(s):  
O. Zhukorskiy ◽  
O. Gulay ◽  
V. Gulay ◽  
N. Tkachuk
Keyword(s):  
Cell Density ◽  
Allelopathic Effect ◽  
Pathogenic Microorganisms ◽  
Sterile Water ◽  
Erysipelothrix Rhusiopathiae ◽  
Pathogenic Leptospira ◽  
Favorable Conditions ◽  
And Control ◽  
The Impact ◽  
Control Samples

Aim. To determine the response of the populations of Erysipelothrix rhusiopathiae and Leptospira interrogans pathogenic microorganisms to the impact of broadleaf cattail (Thypha latifolia) root diffusates. Methods. Aqueous solutions of T. latifolia root diffusates were sterilized by vacuum fi ltration through the fi lters with 0.2-micron pore diameter. The experimental samples contained cattail secretions, sterile water, and cultures of E. rhusiopathiae or L. interrogans. The same amount of sterile water, as in the experimental samples, was used for the purpose of control, and the same quantity of microbial cultures was added in it. After exposure, the density of cells in the experimental and control samples was determined. Results. Root diffusates of T. latifolia caused an increase in cell density in the populations of E. rhusiopathiae throughout the whole range of the studied dilutions (1:10–1:10000). In the populations of the 6 studied serological variants of L. interrogans spirochetes (pomona, grippotyphosa, copenhageni, kabura, tarassovi, canicola), the action of broadleaf cattail root diffusates caused the decrease in cell density. A stimulatory effect was marked in the experimental samples of the pollonica serological variant of leptospira. Conclusions. The populations of E. rhusiopathiae and L. interrogans pathogenic microorganisms respond to the allelopathic effect of Thypha latifolia by changing the cell density. The obtained results provide the background to assume that broadleaf cattail thickets create favorable conditions for the existence of E. rhusiopathiae pathogen bacteria. The reduced cell density of L. interrogans in the experimental samples compared to the control samples observed under the infl uence of T. latifolia root diffusates suggests that reservoirs with broadleaf cattail thickets are marked by the unfavorable conditions for the existence of pathogenic leptospira (except L. pollonica).

scholarly journals Bringing the Virus Back Home: Media Representations of Ukrainian Labour Migrants in a Time of Pandemic

2021 ◽  
pp. 088832542110187
Author(s):  
Alexander Tymczuk
Keyword(s):  
Spatial Organization ◽  
Frame Analysis ◽  
Media Representations ◽  
Potential Danger ◽  
Economic Resource ◽  
Clear Cut ◽  
And Control ◽  
Globalized World ◽  
The Way

In a globalized world where mobility and movement is at its essence, the movement of viruses paradoxically causes a preoccupation with boundaries, containment, and control over borders, and thus keeping the “dangerous” outside separated from the “safe” inside. Through a qualitative thematic and frame analysis of news articles published on 12 Ukrainian news sites, I found that Ukrainian labour migrants conceptually constitute a challenge to such a clear-cut spatial organization in a time of a pandemic. Labour migrants are part of the national “we,” but their presence in the dangerous outside excludes them from the “imagined immunity.” This ambiguity is evident in the way labour migrants were portrayed during the first months of the outbreak in Ukraine. Initially, Ukrainian labour migrants were depicted as a potential danger, and then blamed for bringing the virus back home. However, the framing of the labour migrants as a danger is only part of the story, and the image of a scapegoat was eventually replaced with images of an economic resource and a victim. Thus, Ukrainian labour migrants have been the object of vilification, heroization, as well as empathy during the various phases of the outbreak. I would argue that these shifting frames are connected to the ambiguous conceptualization of Ukrainian labour migrants in general.

The Effect of Trifluralin Applied Preplant on Grass Weed Control and Establishment and Yield of Barley (Hordeum vulgare)

1997 ◽  
Vol 11 (3) ◽  
pp. 515-519 ◽  
Author(s):  
Julio A. Scursoni ◽  
Emilio H. Satorre
Keyword(s):  
Weed Control ◽  
Field Experiments ◽  
Herbicide Application ◽  
Planting Pattern ◽  
Weed Density ◽  
Time Of Application ◽  
Density And Biomass ◽  
And Control ◽  
Crop Planting ◽  
Grass Weed

The objective of this paper was to evaluate the effect of preplant applications of trifluralin on barley stand and yield, and control of grass weeds in field experiments during 1992 and 1993. Factors examined were: (1) crop planting patterns (conventional drill with rows 15 cm apart and deep-seeder drill with rows 25 cm apart), (2) herbicide application times (22 d before sowing and immediately before sowing), and (3) herbicide application. During 1993, hand-weeded plots also were established. Trifluralin applied preplant at 528 g ai/ha reduced weed density and biomass. Weed control was higher under conventional planting than under the deep planting pattern, and there was no effect of the time of application on herbicide efficacy. There was no herbicide injury to the crop, and grain yield was higher in treated than in untreated plots due to successful weed control.

scholarly journals The Relationship between the Community Structure and Function of Bacterioplankton and the Environmental Response in Qingcaosha Reservoir

Water ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3155
Author(s):  
Shumin Liu ◽  
Fengbin Zhao ◽  
Xin Fang
Keyword(s):  
Water Quality ◽  
Community Structure ◽  
High Throughput Sequencing ◽  
Scientific Basis ◽  
Vital Role ◽  
Structure And Function ◽  
Environmental Response ◽  
Temporal And Spatial ◽  
Density And Biomass ◽  
And Function

Phytoplankton and bacterioplankton play a vital role in the structure and function of aquatic ecosystems, and their activity is closely linked to water eutrophication. However, few researchers have considered the temporal and spatial succession of phytoplankton and bacterioplankton, and their responses to environmental factors. The temporal and spatial succession of bacterioplankton and their ecological interaction with phytoplankton and water quality were analyzed using 16S rDNA high-throughput sequencing for their identification, and the functions of bacterioplankton were predicted. The results showed that the dominant classes of bacterioplankton in the Qingcaosha Reservoir were Gammaproteobacteria, Alphaproteobacteria, Actinomycetes, Acidimicrobiia, and Cyanobacteria. In addition, the Shannon diversity indexes were compared, and the results showed significant temporal differences based on monthly averaged value, although no significant spatial difference. The community structure was found to be mainly influenced by phytoplankton density and biomass, dissolved oxygen, and electrical conductivity. The presence of Pseudomonas and Legionella was positively correlated with that of Pseudanabaena sp., and Sphingomonas and Paragonimus with Melosira granulata. On the contrary, the presence of Planctomycetes was negatively correlated with Melosira granulata, as was Deinococcus-Thermus with Cyclotella sp. The relative abundance of denitrifying bacteria decreased from April to December, while the abundance of nitrogen-fixing bacteria increased. This study provides a scientific basis for understanding the ecological interactions between bacteria, algae, and water quality in reservoir ecosystems.

scholarly journals INVERTEBRATE SPECIES COMPOSITION (Invertebrata) PESTS OF AGROCENOSES OF WHITE CLOVER (Trifolium repens L.) AND THE RELEVANCE OF PROTECTIVE MEASURES

2021 ◽  
Vol 2021 (2) ◽  
pp. 57-80
Author(s):  
Vladimir Zolotarev
Keyword(s):  
Species Composition ◽  
White Clover ◽  
Climatic Conditions ◽  
Agricultural Landscapes ◽  
Economic Losses ◽  
Monitoring And Control ◽  
Protective Measures ◽  
Invertebrate Animal ◽  
Seed Crops ◽  
And Control

The area of natural growth and the scale of economic use of white clover among perennial legumes are spatially one of the most global. Due to the constant presence of wild white clover in many natural phyto-cenoses of most agricultural landscapes of different geographical zones, a certain complex of phytophages has evolved from various classes of invertebrate animal organisms that feed on various parts of this plant and reproduce on it. With the introduction of white clover into the culture and the spread of production crops of this plant over large areas, more favorable conditions are created for uncontrolled mass re-production of pests, which can cause already economically and economically significant crop losses. White clover is affected by multi-eating and specialized pests, the damage from which is determined by their biological characteristics and climatic conditions. The high population of white clover crops with a complex of herbivorous invertebrates implies constant monitoring and control of the species composition of the harmful fauna of white clover crops in order to organize, if necessary, protective measures against them. This issue is especially relevant for seed crops. The main pests of seed stands are considered to be weevils of the genera Apion Herbs., Phytonomus Herbs., Sitona Germar., Hypera Germar., which can re-duce seed yield by 50% or more. To reduce the economic losses of the crop on white clover, an integrated protection system should be implemented using chemical, biological and agrotechnical pest control meas-ures based on taking into account their economic harmfulness thresholds. One of the important directions of increasing the efficiency of the production use of white clover is the development of varieties of this crop that are resistant to damage by pathogenic organisms and pests.

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