Effects of thermal effluents on the population dynamics of Physa gyrina Say (Mollusca: Gastropoda) at Lake Wabamun, Alberta

1976 ◽  
Vol 54 (4) ◽  
pp. 582-590 ◽  
Author(s):  
Chandra S. Sankurathri ◽  
John C. Holmes
Keyword(s):  
Population Dynamics ◽  
Aquatic Macrophytes ◽  
Reproductive Activity ◽  
Population Densities ◽  
Rate Of Development ◽  
Thermal Effluents ◽  
Thermal Effluent ◽  
Physa Gyrina ◽  
Heated Area ◽  
Summer Temperatures

Effects of thermal effluents on the population dynamics of Physa gyrina Say (Gastropoda: Pulmonata) were studied at Lake Wabamun, Alberta, from May 1971 to August 1973. Thermal effluent increased the rate of development of eggs and the growth of P. gyrina, and allowed continuous reproductive activity throughout the year. These changes, and the increased period of growth of aquatic macrophytes, resulted in increased population densities of P. gyrina in the heated area during summer. Temperatures below 10 °C or small amounts of vegetation appear to limit the population of P. gyrina in winter.

Effects of crop sequence and rainfall on population dynamics of Fusarium solani f.sp. phaseoli in soil

1992 ◽  
Vol 70 (10) ◽  
pp. 2005-2008 ◽  
Author(s):  
Robert Hall ◽  
Lana Gay Phillips
Keyword(s):  
Population Dynamics ◽  
Phaseolus Vulgaris ◽  
Population Density ◽  
Fusarium Solani ◽  
Population Densities ◽  
Total Rainfall ◽  
Colony Forming Units ◽  
Bean Crop ◽  
Previous Summer ◽  
Crop Sequence

Evidence is presented that population dynamics of Fusarium solani f.sp. phaseoli in soil depend on the effects of crop sequence and rainfall on parasitic activities of the pathogen. In a rotation trial started in 1978 and conducted over 14 years, population densities (colony-forming units/g) of the fungus in soil remained below 50 in treatments (fallow, repeated corn, repeated soybean) where the preferred host plant (common bean, Phaseolus vulgaris) was not grown. Where bean was grown every 3rd year or every year, population densities reached 475 and 660, respectively, by 1984. Thereafter, population densities of the fungus fluctuated widely from year to year in both rotation and repeated bean treatments. In the rotation treatment, peaks in population density of the pathogen coincided with the years of bean production. In repeated bean plots between 1985 and 1991, population density of the fungus in June was significantly correlated (r = 0.77, p = 0.04) with total rainfall received during the previous summer (June–August). It is postulated that higher rainfall during the growing season of the bean crop stimulated root growth and root infection, leading to the accumulation of higher levels of potential inoculum in infected tissue and the release of higher levels of inoculum into the soil by the following June. Key words: Fusarium solani f.sp. phaseoli, bean, Phaseolus vulgaris, rainfall, crop rotation.

scholarly journals Population dynamics and net primary production of the aquatic macrophite Nymphaea rudgeana C. F. Mey in a lotic environment of the Itanhaém River basin (SP, Brazil)

2000 ◽  
Vol 60 (1) ◽  
pp. 83-92 ◽  
Author(s):  
A. F. M. CAMARGO ◽  
E. R. FLORENTINO
Keyword(s):  
Population Dynamics ◽  
Primary Production ◽  
Aquatic Macrophytes ◽  
Aquatic Macrophyte ◽  
Net Primary Production ◽  
Growth Period ◽  
Pistia Stratiotes ◽  
Annual Productivity ◽  
Lotic Environment ◽  
Low Levels

In this paper we evaluated the population dynamics and obtained estimates of the net primary production of the aquatic macrophyte Nymphaea rudgeana in an arm of the Itanhaém River (São Paulo State, Brazil). This species presents, in the studied area, a broad seasonal variation of biomass. As from November (13.1 g DW/m²) we observed a gradual increase of biomass that reached a maximum in February (163.1 g DW/m²). Then, the biomass decreased, maintaining low levels until a new growth period. The reduction of biomass is associated to the development of floating aquatic macrophytes (Pistia stratiotes and Salvinia molesta) and, subsequently to environmental factors (higher salinity values) that are unfavorable to their development. The net primary production of N. rudgeana was estimated from the biomass data, and the annual productivity value was estimated between 3.02 and 3.82 t/ha/year.

scholarly journals Interannual variation in the epibenthic megafauna at the shallowest station of the HAUSGARTEN observatory (79° N, 6° E)

2012 ◽  
Vol 9 (12) ◽  
pp. 18039-18081 ◽  
Author(s):  
K. S. Meyer ◽  
M. Bergmann ◽  
T. Soltwedel
Keyword(s):  
Population Dynamics ◽  
Deep Sea ◽  
Interannual Variation ◽  
Suspension Feeding ◽  
Fram Strait ◽  
Population Densities ◽  
Camera System ◽  
Sea Floor ◽  
Time Period ◽  
Food Input

Abstract. Epibenthic megafauna play an important role in the deep-sea environment and contribute significantly to benthic biomass, but their population dynamics are still understudied. We used a towed deep-sea camera system to assess the population densities of epibenthic megafauna in 2002, 2007 and 2012 at the shallowest station (HG I, ~ 1300 m) of the deep-sea observatory HAUSGARTEN, in the eastern Fram Strait. Our results indicate that the overall density of megafauna was significantly lower in 2007 than in 2002, but was significantly higher in 2012, resulting in overall greater megafaunal density in 2012. Different species showed different patterns in population density, but the relative proportions of predator/scavengers and suspension-feeding individuals were both higher in 2012. Variations in megafaunal densities and proportions are likely due to variation in food input to the sea floor, which decreased slightly in the years preceding 2007 and was greatly elevated in the years preceding 2012. Both average evenness and diversity increased over the time period studied, which indicates that HG I may be food-limited and subject to bottom-up control. The varying dynamics of different species may have been caused by differential capacities of populations to respond to increased food input through either recruitment or migration.

Population dynamics and production of a brine shrimp, Parartemia zietziana Sayce (Crustacea : Anostraca), in two salt lakes in westren Victoria, Australia

1977 ◽  
Vol 28 (4) ◽  
pp. 417 ◽  
Author(s):  
R Marchant ◽  
WD Williams
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Temperature Stress ◽  
Brine Shrimp ◽  
Dry Weight ◽  
Salt Lakes ◽  
Confidence Limits ◽  
Length Frequency ◽  
Population Densities ◽  
The Mean

Quantitative samples of P. zietziana were taken monthly for two years from Pink Lake and Lake Cundare. Shrimps were usually contagiously distributed. To reduce error, samples were stratified resulting in confidence limits of 40-50% for the mean population density. Despite this variability, stable trends emerged, and variation was not so great as to mask significant differences. Length-frequency analyses distinguished cohorts; a regression was established between length and dry weight, enabling growth to be estimated from samples. By combining growth with population densities in Allen curves, production was computed. In Pink Lake and Lake Cundare mean pro- duction was 11.3 and 1.0 g dry weight m-2 year-1 respectively. Generally there were two or three generations per year, but time and extent of recruitment were not predictable. Each generation suffered continuous mortality, the death of young shrimps accounting for most of the production. This mortality remains unexplained; there are no significant predators and salinity and temperature stress would occur only during summer.

Emergence of seedlings of aquatic macrophytes from lake sediments

1983 ◽  
Vol 61 (1) ◽  
pp. 148-156 ◽  
Author(s):  
Richard W. Haag
Keyword(s):  
Lake Sediments ◽  
Initial Treatment ◽  
Aquatic Macrophytes ◽  
Potamogeton Pectinatus ◽  
Sediment Texture ◽  
Substantial Variation ◽  
Initial Exposure ◽  
Sediment Samples ◽  
Thermal Effluent ◽  
Myriophyllum Exalbescens

Sediment samples were collected in May 1980 from 11 stations at five sites in Lake Wabamun. Emergence of seedlings was recorded in a greenhouse at 19 °C for 120 days. The sediments were then chilled at 4 °C for 120 days and reexposed to greenhouse conditions for a further 90 days. Total seedling densities varied from 0 to 2335 m−2. Depth and sediment texture each accounted for 20% of the variance in seedling numbers. Discharge of thermal effluent from the Wabamun generating station also caused substantial variation in seedling number; seedling numbers at the shallowest Wabamun Outlet station were over four times those at any other site. Chilling of the sediment samples in the laboratory caused further emergence of seedlings from the four sites with the highest seedling densities in the initial treatment. Total numbers were up to 50% of those for seedlings that emerged during the initial exposure to greenhouse conditions. Potamogeton pectinatus and P. pusillus were most common among the seedlings of six species. Two of the three most common macrophytes in the lake were rare as seedlings, while no seedlings were recorded for the most common angiosperm, Myriophyllum exalbescens. Reproduction by seed makes a secondary contribution to the dynamics of the vegetation of Lake Wabamun.

scholarly journals Interannual variation in the epibenthic megafauna at the shallowest station of the HAUSGARTEN observatory (79° N, 6° E)

2013 ◽  
Vol 10 (6) ◽  
pp. 3479-3492 ◽  
Author(s):  
K. S. Meyer ◽  
M. Bergmann ◽  
T. Soltwedel
Keyword(s):  
Population Dynamics ◽  
Deep Sea ◽  
Interannual Variation ◽  
Suspension Feeding ◽  
Fram Strait ◽  
Population Densities ◽  
Camera System ◽  
Sea Floor ◽  
Time Period ◽  
Food Input

Abstract. Epibenthic megafauna play an important role in the deep-sea environment and contribute significantly to benthic biomass, but their population dynamics are still understudied. We used a towed deep-sea camera system to assess the population densities of epibenthic megafauna in 2002, 2007, and 2012 at the shallowest station (HG I, ∼1300 m) of the deep-sea observatory HAUSGARTEN, in the eastern Fram Strait. Our results indicate that the overall density of megafauna was significantly lower in 2007 than in 2002, but was significantly higher in 2012, resulting in overall greater megafaunal density in 2012. Different species showed different patterns in population density, but the relative proportions of predator/scavengers and suspension-feeding individuals were both higher in 2012. Variations in megafaunal densities and proportions are likely due to variation in food input to the sea floor, which decreased slightly in the years preceding 2007 and was greatly elevated in the years preceding 2012. Both average evenness and diversity increased over the time period studied, which indicates that HG I may be food-limited and subject to bottom-up control. The community of HG I may be unique in its response to elevated food input, which resulted in higher evenness and diversity in 2012.

scholarly journals Spatiotemporal Distribution and Population Structure ofMonokalliapseudes schubarti(Tanaidacea: Kalliapseudidae) in an Estuary in Southern Brazil

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Felipe Freitas-Júnior ◽  
Martin Lindsey Christoffersen ◽  
Joafrâncio Pereira de Araújo ◽  
Joaquim Olinto Branco
Keyword(s):  
Organic Matter ◽  
Domestic Wastewater ◽  
Reproductive Activity ◽  
Low Energy ◽  
Trophic Levels ◽  
Southeastern Brazil ◽  
Southern Brazil ◽  
Population Densities ◽  
Anthropic Impact ◽  
Swimming Crabs

Monokalliapseudes schubartiis an endemic tanaidacean microcrustacean from southeastern Brazil to Uruguay inhabiting low energy estuaries. Saco da Fazenda is located in the estuary of the Itajaí-Açú River, state of Santa Catarina, Brazil. It is exposed to strong anthropic impact and receives intensive flows of domestic wastewater, solid residues, and drainage activities. Specimens ofM. schubartiwere collected monthly, in the intertidal and subtidal regions of Saco da Fazenda, in four stations defined as a function of the physiography of the environment during the period of July 2003 to June 2004. Fecundity values were high, with continuous reproductive activity during the whole period of study. The greatest population densities were observed in the intertidal region, where they are nevertheless intensely consumed by birds, swimming crabs, and fish. This species represents a fundamental link in the food chain of Saco da Fazenda, transferring energy from the detritus level to higher trophic levels. Habitat disturbance and high organic matter may represent factors controlling the distribution of populations ofM. schubarti. For this reason, the species may be used to monitor anthropic effects in estuarine areas.

Population dynamics of Newfoundland beaver

1977 ◽  
Vol 55 (9) ◽  
pp. 1480-1492 ◽  
Author(s):  
Arthur T. Bergerud ◽  
Donald R. Miller
Keyword(s):  
Population Dynamics ◽  
Mortality Rate ◽  
Litter Size ◽  
Food Resources ◽  
Territorial Behaviour ◽  
Population Densities ◽  
Adult Females ◽  
Annual Mortality

The demography of beaver was studied in Newfoundland from 1956 to 1965. Population densities were low and seldom exceeded one colony per 2.6 km2 (1 mi2). About 80% of the adult females were fertile and the number of young per litter averaged 2.7. The annual mortality rate of beavers was about 30% in southeastern Newfoundland. A more detailed study was made of a population living in a 39-km2 (15-mi2) study area. This population had 20, 23, and 24 active colonies, 1958–1960. In 1961 it declined to 18 colonies. We removed the beavers in 1962. The replacement colonies, resulting initially from ingress, were 7 in 1962, 12 in 1963, 17 in 1964, and 15 in 1965. When the population was high in 1958–1960, the fertility of females was high (78%) but the litter size in 1960 appeared to be less than elsewhere. When the population declined in 1960–1961, productivity declined and some animals may have starved over winter. It was concluded that territorial behaviour spaces colonies, dispersing the population within the limits dictated by the availability of water and food resources. However, such a system did not prevent overutilization of food resources and decline of the population from reduced reproduction and increased mortality.

scholarly journals Population Dynamics of the Sting Nematode in California Turfgrass

Plant Disease ◽  
2000 ◽  
Vol 84 (10) ◽  
pp. 1081-1084 ◽  
Author(s):  
Sadia Bekal ◽  
J. Ole Becker
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Golf Course ◽  
Golf Courses ◽  
Population Densities ◽  
Sampling Area ◽  
Coachella Valley ◽  
Belonolaimus Longicaudatus ◽  
Country Club ◽  
Desert Island

Population densities of Belonolaimus longicaudatus were monitored at monthly intervals at the Tamarisk country club golf course (1993 to 1994) and at the Annenburg Estates and Desert Island golf courses (1998). All three courses are located at Rancho Mirage, Coachella Valley, CA. The bermuda grass in the sampling area typically exhibited chlorosis at the beginning of April when the sting nematode populations began to increase. At the Tamarisk golf course, population density peaked in October, with 1,000 nematodes per 100 cm3 of soil, but declined rapidly, with the lowest population density occurring in December with approximately 50 nematodes per 100 cm3 of soil. At the Annenburg Estates and Desert Island golf courses, the nematode population densities peaked in June and July but declined rapidly to less than half of that density, presumably because of B. longicaudatus-caused host decline. Soil temperature and fluctuation of nematode densities were significantly correlated at all locations. Nematode distribution was greatest in the top 15 cm of soil except during the hottest summer months, when the population was higher at depths of 15 to 30 cm.

scholarly journals Fluctuations in population densities inform stability mechanisms in host-parasitoid interactions

2021 ◽  
Author(s):  
Abhyudai Singh
Keyword(s):  
Population Dynamics ◽  
Population Density ◽  
Functional Response ◽  
Discrete Time ◽  
Host Population ◽  
Reproduction Rate ◽  
Population Densities ◽  
Type Iii ◽  
Time Formalism ◽  
Large Fluctuations

AbstractPopulation dynamics of host-parasitoid interactions has been traditionally studied using a discrete-time formalism starting from the classical work of Nicholson and Bailey. It is well known that differences in parasitism risk among individual hosts can stabilize the otherwise unstable equilibrium of the Nicholson-Bailey model. Here, we consider a stochastic formulation of these discrete-time models, where the host reproduction is a random variable that varies from year to year and drives fluctuations in population densities. Interestingly, our analysis reveals that there exists an optimal level of heterogeneity in parasitism risk that minimizes the extent of fluctuations in the host population density. Intuitively, low variation in parasitism risk drives large fluctuations in the host population density as the system is on the edge of stability. In contrast, high variation in parasitism risk makes the host equilibrium sensitive to the host reproduction rate, also leading to large fluctuations in the population density. Further results show that the correlation between the adult host and parasitoid densities is high for the same year, and gradually decays to zero as one considers cross-species correlations across different years. We next consider an alternative mechanism of stabilizing host-parasitoid population dynamics based on a Type III functional response, where the parasitoid attack rate accelerates with increasing host density. Intriguingly, this nonlinear functional response makes qualitatively different correlation signatures than those seen with heterogeneity in parasitism risk. In particular, a Type III functional response leads to uncorrelated adult and parasitoid densities in the same year, but high cross-species correlation across successive years. In summary, these results argue that the cross-correlation function between population densities contains signatures for uncovering mechanisms that stabilize consumer-resource population dynamics.

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