Effects of Snail Grazing on the Diversity and Structure of a Periphyton Community in a Eutrophic Pond

1989 ◽  
Vol 46 (10) ◽  
pp. 1698-1704 ◽  
Author(s):  
Xavier Swamikannu ◽  
Kyle D. Hoagland
Keyword(s):  
Algal Cell ◽  
Freshwater Snail ◽  
Grazing Pressure ◽  
Intermediate Disturbance Hypothesis ◽  
Community Response ◽  
Intermediate Disturbance ◽  
Low Profile ◽  
Cell Densities ◽  
First Time ◽  
Different Levels

Periphyton diversity was highest at low to intermediate levels of grazing by the freshwater snail Physella and suppressed at high grazer densities, in partial support of the intermediate disturbance hypothesis. For the first time, the response curve of algal biomass versus a range of snail densities was used to establish low, intermediate, and high levels of community disturbance. Physella densities corresponding to these levels were added to net enclosures in a small eutrophic pond, to examine differences in attached algal cell densities and diversity after 20 d. Algal standing crop was enhanced in low and depressed in intermediate and higher grazer treatments. Five categories of attached algal response to grazing were identified: (1) filamentous algae suppressed at high grazing pressure; (2) rosette or filamentous taxa suppressed at moderate to high levels of grazing; (3) algae resistant to grazing via sediment-associated recruitment; (4) low profile algae with highest densities at moderate grazing, and; (5) prostrately attached taxa enhanced at moderate and high grazing levels, in contrast to marine macroalgal communities, the primary mechanism mediating community response to different levels of grazing was the morphology of algal attachment.

A phytoplankton community in a temperate reservoir in New South Wales, Australia: relationships between similarity and diversity indices and measures of hydrological disturbance

2005 ◽  
Vol 56 (2) ◽  
pp. 203 ◽  
Author(s):  
Tsuyoshi Kobayashi ◽  
Brian G. Sanderson ◽  
Geoff N. G. Gordon
Keyword(s):  
Phytoplankton Community ◽  
New South ◽  
Diversity Indices ◽  
Intermediate Disturbance Hypothesis ◽  
Species Number ◽  
Intermediate Disturbance ◽  
Consecutive Sampling ◽  
South Wales ◽  
Cell Densities ◽  
Disturbance Hypothesis

Temporal changes in diversity and similarity of a phytoplankton community were investigated in relation to external hydrological disturbance in the Ben Chifley reservoir from September 1998 to January 2002. Species richness varied by a factor of 4–5 at each of three sites studied during the period (n = 53 at each site). Species diversity (measured using Simpson’s D and Shannon–Wiener’s H, based on primarily genus or species number and cell densities) varied by a factor of 8–10, whereas similarity between two consecutive sampling dates (measured using Hurlbert’s index and Pinkham and Pearson’s B) varied by a factor of 10–46. When diversity was measured with H, it had an approximate quadratic (convex) relationship with similarity, as measured with Hurlbert’s index. However, diversity was seldom related to external hydrological disturbance (measured as intensity and variability of daily inflow rates between two consecutive sampling dates). Similarity was significantly and negatively related to disturbance variability. These results suggest that the mechanisms that regulate diversity and similarity may differ from each other, and question the usefulness of observed approximate quadratic relationships between similarity and diversity indices when assessing the effect of disturbance on diversity. Such relationships may therefore not provide support for Connell’s (1978) intermediate disturbance hypothesis.

scholarly journals Wheat Bread with Grape Seeds Micropowder: Impact on Dough Rheology and Bread Properties

2020 ◽  
Vol 30 (1) ◽  
pp. 138-150
Author(s):  
Veronika Valková ◽  
Hana Ďúranová ◽  
Jana Štefániková ◽  
Michal Miškeje ◽  
Marián Tokár ◽  
...  
Keyword(s):  
Wheat Flour ◽  
Dough Rheology ◽  
Wheat Bread ◽  
Grape Seeds ◽  
Rheological Analysis ◽  
First Time ◽  
Positive Effect ◽  
Bread Properties ◽  
Electronic Eye ◽  
Different Levels

AbstractThe current study was designed to enhance the functionality of white bread by replacement of wheat flour with different levels (1%, 2%, 5%, and 8%) of grape seeds micropowder (GSMP) with nanosized particles (10 µm). Chemical composition of GSMP, volume and sensory attributes, evaluated with the panel of evaluators and an electronic nose (e-nose) and an electronic eye (e-eye) were investigated in the tested breads. It has been found out that GSMP contained appreciable amounts of flavonoids including catechin, epicatechin, gallic acid and minerals especially, Ca, K and Mg. The data from rheological analysis showed that the addition of GSMP (mainly at 5% and 8% levels) to the wheat flour had a positive effect on dough manifesting with rheology by increased dough stability. The volume of the experimental breads (above 1% concentration) was demonstrably declined (P < 0.0001) in comparison with the control bread. Sensory rating revealed that the bread fortified with 1% GSMP was judged by the consumer panelists as the most acceptable with the highest scores for all quality attributes which was also confirmed by the data of e-nose and e-eye. Our results suggest for the first time that 1% GSMP addition appears to be a promising functional ingredient to improve bread with required qualitative and sensory properties.

Urban cloverleaves: origin, aesthetics, and contradictions of the Slussen, Stockholm

2021 ◽  
pp. 1-14
Author(s):  
Álvaro Clua Uceda
Keyword(s):  
Traffic Engineering ◽  
City Centre ◽  
Compact City ◽  
The Baltic Sea ◽  
Southern District ◽  
Stockholm Archipelago ◽  
The Baltic ◽  
First Time ◽  
Historic City ◽  
Different Levels

On 11 October 1935, the inauguration of the Slussen urban cloverleaf took place in front of the excited citizens of Stockholm. It had the attributes of a pure traffic machine taken from the most advanced traffic engineering publications, and it expressed the optimistic cultural modernism that five years ago the Stockholm International Exhibition had promoted.1 This urban cloverleaf was made of translucent glass, reinforced concrete, metallic handrails, and reflective tiles and was meant to solve, in one single gesture, the complex urban link between the Lake Mälaren and the Baltic Sea, between Gamla Stan – the historic city centre – and Södermalm – the southern district built on top of the 35-metre-high plateau [1]. The solution made difficult urban compromises between the foothills of the Brunkeberg topography, the smooth water surfaces of the Stockholm archipelago, the architecture of the historic urban tissue, and the demands of a complex articulated mobility. Boats, goods, suburban trains, subways, trams – later buses – pedestrians, cyclists, and automobiles finally converged on this place at different levels, completing the intricacies of a threedimensional geometry which, for the first time in history, was inserted into a compact city.

scholarly journals IMMUNE RESPONSES IN VITRO

1971 ◽  
Vol 134 (2) ◽  
pp. 395-416 ◽  
Author(s):  
Carl W. Pierce ◽  
Barbara M. Johnson ◽  
Harriet E. Gershon ◽  
Richard Asofsky
Keyword(s):  
Culture Conditions ◽  
Antibody Concentration ◽  
Spleen Cells ◽  
Immunoglobulin Class ◽  
Cell Densities ◽  
Erythrocyte Antigen ◽  
First Time ◽  
Kinetics Of

We have demonstrated for the first time that mouse spleen cells stimulated in vitro with heterologous erythrocytes developed immunoglobulin class-specific γM, γ1, γ2a+2b, and γA plaque-forming cell (PFC) responses. A modification of the hemolytic plaque technique, the addition of goat anti-mouse µ-chain antibody to the assay preparation, specifically prevented development of all γM PFC and enabled accurate and reproducible enumeration of immunoglobulin class-specific PFC after treatment with appropriate monospecific anti-globulins and complement. Culture conditions, with regard to medium, atmosphere, agitation, and spleen cell densities, were similar to those previously shown to support only γM PFC responses. Evaluation of the kinetics of appearance of PFC showed that γM PFC reached maximum numbers on days 4–5; the magnitude of this response was 3–10 times greater than γ1 γ2a+2b, or γA PFC which reached maximum numbers on days 5–6. Optimal erythrocyte antigen dose for γM PFC responses was 107/culture, whereas a dose of 106 erythrocytes/culture consistently stimulated optimal γ1 γ2a+2b, or γA PFC responses. Investigations of the effects of anti-erythrocyte antibody on γM and γG PFC responses indicated that antibody suppressed these responses by neutralizing the effective antigenic stimulus at the macrophage-dependent phase of the response. At the same antibody concentration, γG PFC responses were more effectively suppressed than γM PFC responses. Further, γG responses could be almost completely suppressed by antibody as long as 48 hr after initiation of cultures, whereas γM PFC responses could only be completely suppressed during the first 24 hr. These results were discusssed in terms of the role of antigen in the stimulation γM and γG antibody.

scholarly journals Diversity–disturbance relationships: frequency and intensity interact

2012 ◽  
Vol 8 (5) ◽  
pp. 768-771 ◽  
Author(s):  
Alex R. Hall ◽  
Adam D. Miller ◽  
Helen C. Leggett ◽  
Stephen H. Roxburgh ◽  
Angus Buckling ◽  
...  
Keyword(s):  
Species Diversity ◽  
Empirical Evidence ◽  
Empirical Studies ◽  
Ecological Theory ◽  
Intermediate Disturbance Hypothesis ◽  
Intermediate Disturbance ◽  
Disturbance Frequency ◽  
Theoretical Predictions ◽  
Experimental Populations ◽  
Disturbance Hypothesis

An influential ecological theory, the intermediate disturbance hypothesis (IDH), predicts that intermediate levels of disturbance will maximize species diversity. Empirical studies, however, have described a wide variety of diversity–disturbance relationships (DDRs). Using experimental populations of microbes, we show that the form of the DDR depends on an interaction between disturbance frequency and intensity. We find that diversity shows a monotonically increasing, unimodal or flat relationship with disturbance, depending on the values of the disturbance aspects considered. These results confirm recent theoretical predictions, and potentially reconcile the conflicting body of empirical evidence on DDRs.

scholarly journals THE FORMATION OF THE FINANCIAL AND BUDGETARY SPHERE IN NORTH OSSETIA IN THE TRANSITION PERIOD (1917-1931)

2020 ◽  
Author(s):  
Е.И. КОБАХИДЗЕ
Keyword(s):  
Financial Management ◽  
Transition Period ◽  
Socialist Economy ◽  
New Economic Policy ◽  
Economic Space ◽  
Political Transformations ◽  
Economic Strategies ◽  
First Time ◽  
North Ossetia ◽  
Different Levels

В статье впервые анализируются раннесоветские практики формирования финансово-бюджетной сферы Северной Осетии в контексте государственной политики управления финансами. Их изучение представляется актуальным в связи с очевидным параллелизмом с процессами первого постсоветского десятилетия, когда в России формировалось новое политическое и экономическое пространство, в котором были активно задействованы восстановительные хозяйственно-экономические механизмы, применявшиеся в 20-х гг. XX в. Становление финансовой и бюджетной системы в Северной Осетии рассматривается в ее тесной связи с ходом государственного строительства; отдельное внимание уделено вопросам налогообложения, формирования бюджетов разных уровней, конкретным показателям хозяйственно-экономического развития Осетии на разных этапах переходного периода и в рамках политико-экономических стратегий «военного коммунизма» и «новой экономической политики». Общая специфика исследуемых процессов обусловлена значительными политическими трансформациями, переживаемыми страной в ходе построения советского государства и социалистической экономики. В то же время анализ документов и материалов, в том числе впервые вводимых в научный оборот, показывает, что Осетия, оказавшись в советской системе власти и управления, приобрела собственный опыт построения основ государственности и ее институтов, в том числе в финансовой сфере. For the first time, the article analyzes the early Soviet practices of the formation of the financial and budgetary sphere of North Ossetia in the context of the state policy of financial management. Their study is relevant in connection with the obvious parallelism with the processes of the first post-Soviet decade, when a new political and economic space was formed in Russia, in which the restorative economic mechanisms used in the 1920s were actively involved. The formation of the financial and budgetary system in North Ossetia is considered in its close connection with the progress of state building; special attention is paid to the issues of taxation, the formation of budgets of different levels, specific indicators of economic development of Ossetia at different stages of the transition period and within the framework of political and economic strategies of “war communism” and “new economic policy”. The general specificity of the processes under study is due to the significant political transformations experienced by the country in the course of building the Soviet state and socialist economy. At the same time, the analysis of documents and materials, including those introduced into scientific circulation for the first time, shows that Ossetia, having found itself in the Soviet system of power and administration, has acquired its own experience in building the foundations of statehood and its institutions, in the financial sphere as well.

scholarly journals Activity density of carabid beetles along an urbanisation gradient

2020 ◽  
Vol 66 (Suppl.) ◽  
pp. 21-36
Author(s):  
Simone Fattorini ◽  
Cristina Mantoni ◽  
Davide Bergamaschi ◽  
Lorenzo Fortini ◽  
Francisco J. Sánchez ◽  
...  
Keyword(s):  
Intermediate Disturbance Hypothesis ◽  
Urban Environments ◽  
Carabid Beetles ◽  
City Centre ◽  
Intermediate Disturbance ◽  
Rural Environments ◽  
Activity Density ◽  
Urban Rural ◽  
The Impact ◽  
The City

Several works have investigated the impact of urbanisation on carabid activity density using urban-rural gradients. Such works compared activity density recorded from green spaces located in different parts of a city and assigned to categories of increasing urban intensity, which poses two problems: (1) since the gradient is divided into categories, it is impossible to model continuous variations in biotic responses, and (2) sites representative of different urbanisation levels are not true segments of the same ecological continuum. To surpass these problems, we modelled variations in carabid activity density along an urban-rural transect within a single green space extending from the city centre of Rome to rural environments. Carabids were sampled by pitfall traps from sites distributed along the entire gradient. We used breakpoint regressions to model how (1) carabid activity density, (2) carabids/beetles ratio, (3) carabids/insects ratio and (3) carabids/arthropods ratio varied along the gradient. As already observed for various organisms in urban environments, we found that activity density of carabids and their contribution to the abundance of beetles, insects and arthropods, peaked in the middle of the gradient. This supports the intermediate disturbance hypothesis, according to which moderate urbanisation may favour diversity by increasing habitat heterogeneity.

Social representations of students with different suggestibility levels on a socially profitable person

2021 ◽  
pp. 59-72
Author(s):  
Ekaterina S. Romanova
Keyword(s):  
Human Behavior ◽  
Social Representations ◽  
Well Being ◽  
Cognitive Factor ◽  
Practical Significance ◽  
Positive Image ◽  
Gender Characteristics ◽  
First Time ◽  
Further Development ◽  
Different Levels

The issue of the interrelation of social representations of students with different levels of suggestibility about a socially profitable person is discussed. The content of the concept of a “socially profitable person” is revealed. The analysis of theoretical and methodological literature concretizes the content of the concepts of “social representations”, “suggestibility”. In the study we take into account the gender characteristics of the subjects. The obtained results have a scientific novelty, since this kind of work was carried out for the first time. It was found that the sample has mainly an average suggestibility level, is malleable and tends to allow other people’s ideas into their consciousness. Semantic units (descriptors) describing the ideas of a socially profitable person in boys and girls do not have significant differences. Factors were formed from the obtained descriptors: 12 – in boys, 13 – in girls, 11 factors coincided. The dominant factors were “Social and material well-being”, “Benevolence”, “Cultural and cognitive factor”. The practical significance of the study is in the possibility of organizing purposeful work on the formation of a positive image of a person in demand by society. Representations determine the assessment of one’s own qualities, regulate human behavior. Further development of the problem can be aimed at expanding the sample of subjects and creating a psychological and pedagogical program.

Sign in / Sign up

Export Citation Format

Share Document