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1

Environmental toxicology: population modeling of cod larvae shows high sensitivity to loss of zooplankton prey.  

PubMed

Two factors determine whether pollution is likely to affect a population indirectly through loss of prey: firstly, the sensitivity of the prey to the pollutants, and secondly, the sensitivity of the predator population to loss of prey at the given life stage. We here apply a statistical recruitment model for Northeast Arctic cod to evaluate the sensitivity of cod cohorts to loss of zooplankton prey, for example following an oil spill. The calculations show that cod cohorts are highly sensitive to possible zooplankton biomass reductions in the distribution area of the cod larvae, and point to a need for more knowledge about oil-effects on zooplankton. Our study illustrates how knowledge about population dynamics may guide which indirect effects to consider in environmental impact studies. PMID:21194716

Stige, Leif Christian; Ottersen, Geir; Hjermann, Dag Ø; Dalpadado, Padmini; Jensen, Louise K; Stenseth, Nils Chr

2010-12-30

2

Determining dominant scatterers of sound in mixed zooplankton populations.  

PubMed

High-frequency acoustic scattering techniques have been used to investigate dominant scatterers in mixed zooplankton populations. Volume backscattering was measured in the Gulf of Maine at 43, 120, 200, and 420 kHz. Zooplankton composition and size were determined using net and video sampling techniques, and water properties were determined using conductivity, temperature, and depth sensors. Dominant scatterers have been identified using recently developed scattering models for zooplankton and microstructure. Microstructure generally did not contribute to the scattering. At certain locations, gas-bearing zooplankton, that account for a small fraction of the total abundance and biomass, dominated the scattering at all frequencies. At these locations, acoustically inferred size agreed well with size determined from the net samples. Significant differences between the acoustic, net, and video estimates of abundance for these zooplankton are most likely due to limitations of the net and video techniques. No other type of biological scatterer ever dominated the scattering at all frequencies. Copepods, fluid-like zooplankton that account for most of the abundance and biomass, dominated at select locations only at the highest frequencies. At these locations, acoustically inferred abundance agreed well with net and video estimates. A general approach for the difficult problem of interpreting high-frequency acoustic scattering in mixed zooplankton populations is described. PMID:18247742

Lavery, Andone C; Wiebe, Peter H; Stanton, Timothy K; Lawson, Gareth L; Benfield, Mark C; Copley, Nancy

2007-12-01

3

An approach for the assessment of risk from chronic radiation to populations of phytoplankton and zooplankton  

Microsoft Academic Search

A conceptual model of the effects of chronic radiation on a population of phytoplankton and zooplankton in an oceanic nutrient\\u000a layer is presented. The model shows that there are distinct threshold dose rates at which the different plankton populations\\u000a become unsustainable. These are 10,400 µGy h?1 for phytoplankton and 125 µGy h?1 for zooplankton. Both these values are considerably greater than the current screening

R. C. Wilson; J. Vives i Batlle; S. J. Watts; P. McDonald; S. R. Jones; A. Craze

2010-01-01

4

Lake acidification: Effects on crustacean zooplankton populations  

SciTech Connect

The ranked acid sensitivities of six common crustacean zooplankton taxa were determined from a multilake field survey in Ontario and from laboratory bioassays. The two approaches gave the same ranking (from most to least sensitive): Daphnia galeata mendotae, Daphnia retrocurva, and Skistodiaptomus oregonensis > Diaphanosoma birgei > Mesocyclops edax > Bosmina longirostris. This finding suggests that acidification has caused the widespread damage which has been documented for the zooplankton of Ontario and northeastern US lakes. 24 refs., 3 figs., 2 tabs.

Havens, K.E. (Kent State Univ., OH (United States)); Yan, N.D. (Ontario Ministry of the Environment, Dorset (Canada)); Keller, W. (Ontario Ministry of the Environment, Sudbury (Canada))

1993-08-01

5

Interactions between Predation and Resources Shape Zooplankton Population Dynamics  

PubMed Central

Identifying the relative importance of predation and resources in population dynamics has a long tradition in ecology, while interactions between them have been studied less intensively. In order to disentangle the effects of predation by juvenile fish, algal resource availability and their interactive effects on zooplankton population dynamics, we conducted an enclosure experiment where zooplankton were exposed to a gradient of predation of roach (Rutilus rutilus) at different algal concentrations. We show that zooplankton populations collapse under high predation pressure irrespective of resource availability, confirming that juvenile fish are able to severely reduce zooplankton prey when occurring in high densities. At lower predation pressure, however, the effect of predation depended on algal resource availability since high algal resource supply buffered against predation. Hence, we suggest that interactions between mass-hatching of fish, and the strong fluctuations in algal resources in spring have the potential to regulate zooplankton population dynamics. In a broader perspective, increasing spring temperatures due to global warming will most likely affect the timing of these processes and have consequences for the spring and summer zooplankton dynamics.

Nicolle, Alice; Hansson, Lars-Anders; Brodersen, Jakob; Nilsson, P. Anders; Bronmark, Christer

2011-01-01

6

Are closure terms appropriate or necessary descriptors of zooplankton loss in nutrient–phytoplankton–zooplankton type models?  

Microsoft Academic Search

Our current knowledge of plankton ecology ascribes a large proportion of zooplankton losses to zooplankton cannibalism and carnivory, rather than via the activity of higher trophic levels beyond the plankton. However, planktonic ecosystem models, such as the widely used nutrient–phytoplankton–zooplankton (NPZ) type models, typically represent all zooplankton losses by mathematically (rather than biologically) justified closure functions. Even where it is

Aditee Mitra

2009-01-01

7

Modeling vertical carbon flux from zooplankton respiration  

NASA Astrophysics Data System (ADS)

The transport of carbon from ocean surface waters to the deep sea is a critical factor in calculations of planetary carbon cycling and climate change. This vertical carbon flux is currently thought to support the respiration of all the organisms in the water column below the surface, the respiration of the organisms in the benthos, as well as the carbon lost to deep burial. Accordingly, for conditions where the benthic respiration and the carbon burial are small relative to the respiration in the water column, and where horizontal fluxes are known or negligible, the carbon flux can be calculated by integrating the vertical profile of the water-column plankton respiration rate. Here, this has been done for the zooplankton component of the vertical carbon flux from measurements of zooplankton ETS activity south of the Canary Island Archipelago. From zooplankton ETS activity depth profiles, zooplankton respiration depth profiles were calculated and using the equations for the profiles as models, the epipelagic (3.05 ?mol CO2 m-3 h-1), mesopelagic (112.82 nmol CO2 m-3 h-1), and bathypelagic (27.89 nmol CO2 m-3 h-1) zooplankton respiration for these waters were calculated. Then, by integration of the depth-normalized respiration profiles, zooplankton-associated carbon flux profiles below 150 m were calculated. These had an uncertainty of ±40%. At the station level (local regional variation) the variability was ±114% (n = 16). At 150 m and 500 m the average passive carbon flux associated with the zooplankton was 36 (±114%) and 20 (±113%) ?mol C m-2 h-1. The carbon transfer efficiency (Teff) from the 150 to the 500 m levels averaged 51 ± 21% and a new metric, the nutrient retention efficiency (NRE), averaged 49 ± 21%. This metric is an index of the efficiency with which nutrients are maintained in the epipelagic zone and is directly related to the respiration in the water column. The carbon flux equation describing the pooled data (n = 16) was 131.14Z-0.292. Using this as a model for zooplankton-associated carbon flux south of the Canary Islands one can calculate that carbon flux from epipelagic waters at 200 m is 27.91 ?mol C m-2 h-1, and the carbon flux from mesopelagic waters at 1000 m, is 17.45 ?mol C m-2 h-1.

Packard, Theodore T.; Gómez, May

2013-03-01

8

Seasonal variations in the metabolic rates of zooplankton populations in a Thames Valley reservoir  

Microsoft Academic Search

Measurements of metabolic rates of natural populations of zooplankton were made using a closed bottle technique in situ. Results showed a marked seasonality inexplicable in terms of simple temperature functions. For this cladoceran dominated zooplankton, seasonal variations in metabolic response are attributed to a degree of temperature acclimation, to changes in the size structure and species composition of the populations

T. E. Andrew; N. Ireland

1985-01-01

9

Distribution and abundance of zooplankton populations in Crater Lake, Oregon  

USGS Publications Warehouse

The zooplankton assemblages in Crater Lake exhibited consistency in species richness and general taxonomic composition, but varied in density and biomass during the period between 1988 and 2000. Collectively, the assemblages included 2 cladoceran taxa and 10 rotifer taxa (excluding rare taxa). Vertical habitat partitioning of the water column to a depth of 200 m was observed for most species with similar food habits and/or feeding mechanisms. No congeneric replacement was observed. The dominant species in the assemblages were variable, switching primarily between periods of dominance of Polyarthra-Keratella cochlearis and Daphnia. The unexpected occurrence and dominance of Asplanchna in 1991 and 1992 resulted in a major change in this typical temporal shift between Polyarthra-K. cochlearis and Daphnia. Following a collapse of the zooplankton biomass in 1993 that was probably caused by predation from Asplanchna, Kellicottia dominated the zooplankton assemblage biomass between 1994 and 1997. The decline in biomass of Kellicottia by 1998 coincided with a dramatic increase in Daphnia biomass. When Daphnia biomass declined by 2000, Keratella biomass increased again. Thus, by 1998 the assemblage returned to the typical shift between Keratella-Polyarthra and Daphnia. Although these observations provided considerable insight about the interannual variability of the zooplankton assemblages in Crater Lake, little was discovered about mechanisms behind the variability. When abundant, kokanee salmon may have played an important role in the disappearance of Daphnia in 1990 and 2000 either through predation, inducing diapause, or both. ?? 2007 Springer Science+Business Media B.V.

Larson, G. L.; McIntire, C. D.; Buktenica, M. W.; Girdner, S. F.; Truitt, R. E.

2007-01-01

10

The Effect of Rotenone on Zooplankton Populations in Freshwater Lakes  

Microsoft Academic Search

Though the use of rotenone is a common procedure in freshwater fishery management, little is known of its effect on zooplankton. Fern Lake, a shallow dystrophic lake in western Washington, was treated with 0.5 p.p.m. of 5 percent rotenone powder in June 1960. Biweekly sampling of the open water, shore edge, and marsh area prior to and for 6 months

R. W. Kiser; John R. Donaldson; Paul R. Olson

1963-01-01

11

Comparison of acoustic measurements of zooplankton populations using an Acoustic Water Column Profiler and an ADCP  

Microsoft Academic Search

Self-contained, moored echo sounders are a means of monitoring the behavior of populations of zooplankton and small fish over extended periods of time. Such instruments, either moored at or near the seafloor looking upward, or mounted on a surface buoy looking downward, record profiles of acoustic backscatter as a time series, and thus can provide insights into the long-term behavior

D. D. Lemon; D. Billenness; J. Buermans

2008-01-01

12

Use of Zooplankton Size to Assess the Community Structure of Fish Populations in Freshwater Lakes  

Microsoft Academic Search

In this study, we examined the relationship between mean size of zooplankton and fish community structure in 35 New York lakes. The study lakes contained fish populations dominated by percids, centrarchids, or both, and were categorized based on fish species composition and the ratio of predators to panfish. An increase in the predator-to-panfish ratio was matched by an increase in

Edward L. Mills; David M. Green; Albert Schiavone Jr

1987-01-01

13

Estimating release rates of phosphorus from zooplankton: Model and experimental verification  

Microsoft Academic Search

The flux of phosphorus in a zooplankton-phytoplankton system is described by a simple com- partment model, with differential equations for grazing, growth and reproduction of animals, and release and recycling of P. The mean release rates from zooplankton for a given period are derived for cases restricted to animals feeding on algae at densities abcve the incipient limiting food concentration.

YNGVAR OLSEN; KJETILL ØSTGAARD

1985-01-01

14

Population dynamics of pond zooplankton, I. Diaptomus pallidus Herrick  

USGS Publications Warehouse

The simultaneous and lag relationships between 27 environmental variables and seven population components of a perennial calanoid copepod were examined by simple and partial correlations and stepwise regression. The analyses consistently explained more than 70% of the variation of a population component. The multiple correlation coefficient (R) usually was highest in no lag or in 3-week or 4-week lag except for clutch size in which R was highest in 1-week lag. Population control, egg-bearing, and clutch size were affected primarily by environmental components categorized as weather; food apparently was relatively minor in affecting population control or reproduction. ?? 1973 Dr. W. Junk B.V. Publishers.

Armitage, K. B.; Saxena, B.; Angino, E. E.

1973-01-01

15

Spatiotemporal dynamics in a reaction-diffusion toxic-phytoplankton-zooplankton model  

NASA Astrophysics Data System (ADS)

In this paper, we investigate the complex dynamics of a spatial toxic-phytoplankton-zooplankton model with Holling type-II functional response. Through a detailed analytical study of the reaction-diffusion model, we obtain some conditions for local and global stability and for diffusive instability with zero-flux boundary conditions of a positive equilibrium. On the basis of these results, we present the evolutionary processes of pattern formation that involve organism distribution and the interaction of a spatially distributed population with local diffusion. Then, novel numerical evidence of the time evolution of patterns controlled by diffusion and environmental carrying capability in the model are presented, and it is found that the model dynamics exhibits complex pattern replication. Additional studies reveal that pattern formation in the spatially extended model depends on the choice of the initial conditions. These results indicate that the interaction between toxin-producing phytoplankton and zooplankton in marine environments may be partly driven by the forces of diffusion or the environmental carrying capability.

Rao, Feng

2013-08-01

16

Effects of toxic substances on zooplankton populations: a Great Lakes perspective  

SciTech Connect

The chapter discusses how toxic substances can affect zooplankton, both at the species and community level, modifying factors affecting toxicity, the effects of various environmental pertubations, including toxic substances, on Great Lakes zooplankton, and the role of zooplankton in the transport, persistence, and biomagnification of toxic substances.

Evans, M.S.; McNaught, D.

1988-01-01

17

Impact of climate change on zooplankton communities, seabird populations and arctic terrestrial ecosystem—A scenario  

NASA Astrophysics Data System (ADS)

Many arctic terrestrial ecosystems suffer from a permanent deficiency of nutrients. Marine birds that forage at sea and breed on land can transport organic matter from the sea to land, and thus help to initiate and sustain terrestrial ecosystems. This organic matter initiates the emergence of local tundra communities, increasing primary and secondary production and species diversity. Climate change will influence ocean circulation and the hydrologic regime, which will consequently lead to a restructuring of zooplankton communities between cold arctic waters, with a dominance of large zooplankton species, and Atlantic waters in which small species predominate. The dominance of large zooplankton favours plankton-eating seabirds, such as the little auk ( Alle alle), while the presence of small zooplankton redirects the food chain to plankton-eating fish, up through to fish-eating birds (e.g., guillemots Uria sp.). Thus, in regions where the two water masses compete for dominance, such as in the Barents Sea, plankton-eating birds should dominate the avifauna in cold periods and recess in warmer periods, when fish-eaters should prevail. Therefore under future anthropogenic climate scenarios, there could be serious consequences for the structure and functioning of the terrestrial part of arctic ecosystems, due in part to changes in the arctic marine avifauna. Large colonies of plankton-eating little auks are located on mild mountain slopes, usually a few kilometres from the shore, whereas colonies of fish-eating guillemots are situated on rocky cliffs at the coast. The impact of guillemots on the terrestrial ecosystems is therefore much smaller than for little auks because of the rapid washing-out to sea of the guano deposited on the seabird cliffs. These characteristics of seabird nesting sites dramatically limit the range of occurrence of ornithogenic soils, and the accompanying flora and fauna, to locations where talus-breeding species occur. As a result of climate warming favoring the increase of ichthyiofagous cliff-nesting seabirds, we can expect that large areas of ornithogenic tundra around the colonies of plankton-eating seabirds situated far from the sea may disappear, while areas of tundra in the vicinity of cliffs inhabited by fish-eating seabirds, with low total production and supporting few large herbivores, will likely increase, but only imperceptibly. This may lead to habitat fragmentation with negative consequences for populations of tundra-dependent birds and mammals, and the possibility of a substantial decrease in biodiversity of tundra plant and animal communities.

Stempniewicz, Lech; B?achowiak-Samo?yk, Katarzyna; W?s?awski, Jan M.

2007-11-01

18

Modelling the population dynamics of Calanus in the Fair Isle current of northern Scotland  

Microsoft Academic Search

The population dynamics of a marine zooplankton species in the Fair Isle Current off northern Scotland have been investigated by modelling and field study. An age- and weight-structured model of a population of the copepods Calanus finmarchicus and Calanus helgolandicus was embedded in a biomass based ecosystem model comprising nutrients, phytoplankton, and other non-Calanus zooplankton. The model was configured to

M. Heath; W. Robertson; J. Mardaljevic; W. S. G. Gurney

1997-01-01

19

Population dynamics of zooplankton in the upper Potomac Estuary, March through May, 1977. Final report  

Microsoft Academic Search

Densities of zooplankton were measured at seven stations from Sheridan Point (near Washington, DC) to Stuart Point (115 km downstream) from mid-April to early June at weekly intervals. Three stations were sampled in mid-March. Zooplankton biomass was calculated from the measured densities and published estimates of weights of the various species. Production was calculated from instantaneous birth rates based on

D. R. Heinle; P. Pulles; H. S. Millsaps

1979-01-01

20

EFFECTS OF TOXIC SUBSTANCES ON ZOOPLANKTON POPULATIONS: A GREAT LAKES PERSPECTIVES  

EPA Science Inventory

In this chapter, we discuss (1) how toxic substances can affect zooplankton, both at the species and community level, (2) modifying factors affecting toxicity, (3) the effects of various environmental pertubations, including toxic substances, on Great Lakes zooplankton, and (4) t...

21

Evaluation of Fish Communities Through Assessment of Zooplankton Populations and Measures of Lake Productivity  

Microsoft Academic Search

Knowledge of zooplankton size structure and measure of lake productivity can facilitate interpretation of data from fishery surveys. Our findings demonstrate that, for small warm-water lakes containing predominantly centrarchids and percids, the size composition of the zooplankton community and growth and size structure of the fish community are closely correlated. Spatial-temporal differences between lakes suggest the fishery manager can obtain

Edward L. Mills; Albert Schiavone JR

1982-01-01

22

Grazing experiments and model simulations of the role of zooplankton in Phaeocystis food webs  

Microsoft Academic Search

A combined empirical and modelling study was conducted to further examine the potential importance of grazing by zooplankton in pelagic food webs in which Phaeocystis is a significant or dominant component. Laboratory experiments were designed to measure ingestion of Phaeocystis and other potential prey items which co-occur with Phaeocystis. Grazers included copepods and ciliates, and prey included Phaeocystis colonies and

P. G. Verity

2000-01-01

23

Effects of inorganic turbidity and reservoir floods on the feeding and population dynamics of Cladoceran zooplankton  

SciTech Connect

Clearance rates of {sup 32}P-labeled yeast cell tracer particles and gravimetric seston analysis were used to estimate in situ seston ingestion rates of Daphnia parvula and Bosmina along the seston gradient in Tuttle Creek Reservoir, near Manhattan, Kansas. An ingestion rate depression occurred for both species at the highest seston concentration. The smallest animals, Bosmina, had a lower incipient limiting concentration and exhibited a stronger ingestion rate depression. The fecundity and abundance of Daphnia parvula, grown in enclosures along the seston gradient prior to the ingestion rate measurements, were highest at the river inflow region. Reservoir Bosmina, however, were least abundant and had the lowest fecundity at the river inflow region. The abundance of Bosmina, calanoid copepods, and cyclopoid copepods were lower following large storm inflows in the late spring of 1983 and 1984, while the abundance of Diaphanosoma and Moina were similar. Both open reservoir and in situ enclosure populations of Daphnia pulex were reduced following the storm inflow, while only enclosure populations of Daphnia parvula were lower. Diaphanosoma and calanoid copepods dominated the zooplankton during sampling from spring through fall 1984, particularly in midsummer when temperatures were greater than 25{degree}C. Daphnids dominated numerically during the fall baseflow period.

Shuman, J.R.

1988-01-01

24

How far details are important in ecosystem modelling: the case of multi-limiting nutrients in phytoplankton-zooplankton interactions  

PubMed Central

We try to answer the question of to what extent details in nutrient uptake and phytoplankton physiology matter for population and community dynamics. To this end, we study how two nutrients interact in limiting phytoplankton growth. A popular formulation uses a product-rule for nutrient uptake, which we compare with that on the basis of synthesizing units. We first fit different nutrient uptake models to a dataset and conclude that the quantitative differences between the models are small. Then we study the sensitivity of phytoplankton growth and zooplankton–phytoplankton interactions (ZPi) models to uptake formulations. Two population models are compared; they are based on different assumptions on the relation between nutrient uptake and phytoplankton growth. We find that the population and community models are sensitive to uptake formulations. According to the uptake formulation used in the ZPi models, qualitative differences can be observed. Indeed, although two models based on functions with similar shapes have close equilibria, these can differ in stability properties. Since stability involves the derivatives of formulas, even if two formulas provide close values, large numerical differences in the stability criterion may occur after derivation. We conclude that mechanistic details can be of importance for community modelling.

Poggiale, J.-C.; Baklouti, M.; Queguiner, B.; Kooijman, S. A. L. M.

2010-01-01

25

Will reduced summer UV-B levels affect zooplankton populations of temperate humic and clearwater lakes?  

Microsoft Academic Search

We collected zooplankton samples from 4×4 m enclosures located in two acidified lakes (pH?1 (brown water), while the other had values between 2 and 4 mg l?1. In each lake, three enclosures were open to ambient light, while three were covered by Mylar® sheets which removed UVB and UVC wavelengths. Weekly sampling was done at all sites in July and

T. A. Clair; J. Ehrman; I. Kaczmarska; A. Locke; D. W. Tarasick; K. E. Day; G. Maillet

2001-01-01

26

A method to represent seasonal vertical migration of Zooplankton in 3D-Eulerian models  

NASA Astrophysics Data System (ADS)

To understand the vertical distribution of zooplankton, the swimming behavior of the animals in response to physical processes, food conditions etc., has to be taken into account. The active, vertical migration of copepods can be considered as a reaction to external and internal stimuli. The reaction patterns can be covered by a set of behavioral rules. In this paper, we introduce a method based on so-called evaluation functions that assess the local habitats of the copepods at each grid point of the model, and to quantify the probability of their possible reactions in terms of up- or downward migration. The method is tested for the case of the Baltic Sea and considers seasonal vertical migration. Known observational facts of the main mesozooplankton groups are used to define the evaluation functions for two aggregated groups of model copepods, which occupy different habitats. The copepod groups are divided into five developmental stages. Several simulations were carried out with the aid of one- and three-dimensional Eulerian models to constrain the involved set of parameters. It can be shown that a plausible characterization of the behavioral features of copepods, as generally known from observations, mimics the migration patterns of the model copepods in an excellent agreement with the typical behavioral pattern of the main mesozooplankton in the Baltic Sea. The method provides a relatively easy way to introduce aspects of zooplankton behavior in ecosystem models. It can be applied to Eulerian models and allows numerical optimization of the code in a straightforward manner.

Neumann, Thomas; Fennel, Wolfgang

27

Estimating release rates of phosphorus from zooplankton: model and experimental verification  

SciTech Connect

The flux of phosphorus in a zooplankton-phytoplankton system is described by a simple compartment model, with differential equations for grazing, growth and reproduction of animals, and release and recycling of P. The mean release rates from zooplankton for a given period are derived for cases restricted to animals feeding on algae at densities above the incipient limiting food concentration. The model is used to analyze short term incubation experiments with Daphnia pulex feeding on Scenedesmus sp. and Daphnia longispina feeding on Rhodomonas lacustris in dim light. When food organisms were saturated with P. total release rates were in the range 1.1-1.5 ..mu..g P (mg dry wt)/sup -1/h/sup -1/ in accordance with a maximal excretion rate of 0.8 ..mu..g P (mg dry wt)/sup -1/h)/sup 1/ predicted by the model of Peters. Phosphorus-starved phytoplankton, containing less P, gave much lower release rates, about 0.05 ..mu..g P (mg dry wt)/sup -1/h/sup -1/, only 10% of the excretion rate predicted by the model of Peters.

Not Available

1985-07-01

28

Predicting crustacean zooplankton species richness  

Microsoft Academic Search

Data from 66 North American lakes were collected to construct a model for predicting the number of crustacean zooplankton species expected in a lake. The chosen lakes have a range from 4 m* to 80 x lo9 m2 surface area, range from ultra-oligotrophic to hypereutrophic, and have zooplankton species lists based on several years of observation. The number of crustacean

STANLEY DODSON

1992-01-01

29

Lagrangian model of zooplankton dispersion: numerical schemes comparisons and parameter sensitivity tests  

NASA Astrophysics Data System (ADS)

This paper presents two comparisons or tests for a Lagrangian model of zooplankton dispersion: numerical schemes and time steps. Firstly, we compared three numerical schemes using idealized circulations. Results show that the precisions of the advanced Adams-Bashfold-Moulton (ABM) method and the Runge-Kutta (RK) method were in the same order and both were much higher than that of the Euler method. Furthermore, the advanced ABM method is more efficient than the RK method in computational memory requirements and time consumption. We therefore chose the advanced ABM method as the Lagrangian particle-tracking algorithm. Secondly, we performed a sensitivity test for time steps, using outputs of the hydrodynamic model, Symphonie. Results show that the time step choices depend on the fluid response time that is related to the spatial resolution of velocity fields. The method introduced by Oliveira et al. in 2002 is suitable for choosing time steps of Lagrangian particle-tracking models, at least when only considering advection.

Qiu, Zhongfeng; Doglioli, Andrea M.; He, Yijun; Carlotti, Francois

2011-03-01

30

Acoustic classification of zooplankton  

NASA Astrophysics Data System (ADS)

Work on the forward problem in zooplankton bioacoustics has resulted in the identification of three categories of acoustic scatterers: elastic-shelled (e.g. pteropods), fluid-like (e.g. euphausiids), and gas-bearing (e.g. siphonophores). The relationship between backscattered energy and animal biomass has been shown to vary by a factor of ~19,000 across these categories, so that to make accurate estimates of zooplankton biomass from acoustic backscatter measurements of the ocean, the acoustic characteristics of the species of interest must be well-understood. This thesis describes the development of both feature based and model based classification techniques to invert broadband acoustic echoes from individual zooplankton for scatterer type, as well as for particular parameters such as animal orientation. The feature based Empirical Orthogonal Function Classifier (EOFC) discriminates scatterer types by identifying characteristic modes of variability in the echo spectra, exploiting only the inherent characteristic structure of the acoustic signatures. The model based Model Parameterisation Classifier (MPC) classifies based on correlation of observed echo spectra with simplified parameterisations of theoretical scattering models for the three classes. The Covariance Mean Variance Classifiers (CMVC) are a set of advanced model based techniques which exploit the full complexity of the theoretical models by searching the entire physical model parameter space without employing simplifying parameterisations. Three different CMVC algorithms were developed: the Integrated Score Classifier (ISC), the Pairwise Score Classifier (PSC) and the Bayesian Probability Classifier (BPC); these classifiers assign observations to a class based on similarities in covariance, mean, and variance, while accounting for model ambiguity and validity. These feature based and model based inversion techniques were successfully applied to several thousand echoes acquired from broadband (~350 kHz-750 kHz) insonifications of live zooplankton collected on Georges Bank and the Gulf of Maine to determine scatterer class. CMVC techniques were also applied to echoes from fluid-like zooplankton (Antarctic krill) to invert for angle of orientation using generic and animal-specific theoretical and empirical models. Application of these inversion techniques in situ will allow correct apportionment of backscattered energy to animal biomass, significantly improving estimates of zooplankton biomass based on acoustic surveys. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

Martin Traykovski, Linda V.

1998-11-01

31

Zooplankton intermittency and turbulence  

NASA Astrophysics Data System (ADS)

Planktonic organisms usually live in a turbulent world. Since marine turbulence is characterized by very high Reynolds numbers, it possesses very intermittent fluctuations which in turn affect marine life. We consider here such influence on zooplankton on 2 aspects. First we consider zooplankton motion in the lab. Many copepods display swimming abilities. More and more species have been recently recorded using normal or high speed cameras, and many trajectories have been extracted from these movies and are now available for analysis. These trajectories can be complex, stochastic, with random switching from low velocity to high velocity events and even jumps. These complex trajectories show that an adequate modeling is necessary to understand and characterize them. Here we review the results published in the literature on copepod trajectories. We discuss the random walk, Levy walk modeling and introduce also multifractal random walks. We discuss the way to discriminate between these different walks using experimental data. Stochastic simulations will be performed to illustrate the different families. Second, we consider zooplankton contact rates in the framework of intermittent turbulence. Intermittency may have influence on plankton contact rates. We consider the Particle Stokes number of copepods, in a intermediate dissipation range affected by intermittent fluctuations. We show that they may display preferential concentration effects, and we consider the influence on contact rates of this effect in the intermediate dissipation range.

Schmitt, François G.

2010-05-01

32

The effects of juvenile American shad planktivory on zooplankton production in Columbia River food webs  

USGS Publications Warehouse

Columbia River reservoirs support a large population of nonnative American Shad Alosa sapidissima that consume the zooplankton that native fishes also rely on. We hypothesized that the unprecedented biomass of juvenile American Shad in John Day Reservoir is capable of altering the zooplankton community if these fish consume a large portion of the zooplankton production. We derived taxon-specific estimates of zooplankton production using field data and a production model from the literature. Empirical daily ration was estimated for American Shad and expanded to population-level consumption using abundance and biomass data from hydroacoustic surveys. Daphnia spp. production was high in early summer but declined to near zero by September as shad abundance increased. American Shad sequentially consumed Daphnia spp., copepods, and Bosmina spp., which tracked the production trends of these taxa. American Shad evacuation rates ranged from 0.09 to 0.24/h, and daily rations ranged from 0.008 to 0.045 g·g?1·d?1 (dry weight) over all years. We observed peak American Shad biomass (45.2 kg/ha) in 1994, and daily consumption (1.6 kg/ha) approached 30% (5.3 kg/ha) of zooplankton production. On average, American Shad consumed 23.6% of the available zooplankton production (range, <1–83%). The changes in the zooplankton community are consistent with a top-down effect of planktivory by American Shad associated with their unprecedented biomass and consumption, but the effects are likely constrained by temperature, nutrient flux, and the seasonal production patterns of zooplankton in John Day Reservoir. American Shad add to the planktivory exerted by other species like Neomysis mercedis to reduce the capacity of the reservoir to support other planktivorous fishes. The introduction of American Shad and other nonnative species will continue to alter the food web in John Day Reservoir, potentially affecting native fishes, including Pacific salmon Oncorhynchus spp.

Haskell, Craig A.; Tiffan, Kenneth F.; Rondorf, Dennis W.

2013-01-01

33

Use Limnetic Zooplankton Sampling in Assessments of Fish Community Structure in Minnesota Bass-Panfish Lakes.  

National Technical Information Service (NTIS)

Zooplankton and fish were sampled in 42 bass-panfish lakes over a two year period to determine if zooplankton sampling coupled with standard fish population assessments could be a useful fisheries management tool. Correlation analysis was used to identify...

J. E. Westerlund P. C. Jacobson H. K. Van Offelen J. K. Hirsch

1998-01-01

34

Zooplankton in the Arctic outflow  

NASA Astrophysics Data System (ADS)

Climate changes in the Arctic cause the changes in the current system that may have cascading effect on the structure of plankton community and consequently on the interlinked and delicately balanced food web. Zooplankton species are by definition incapable to perform horizontal moving. Their transport is connected with flowing water. There are zooplankton species specific for the definite water masses and they can be used as markers for the different currents. That allows us to consider zooplankton community composition as a result of water mixing in the studied area. Little is known however about the mechanisms by which spatial and temporal variability in advection affect dynamics of local populations. Ice conditions are also very important in the function of pelagic communities. Melting time is the trigger to all "plankton blooming" processes, and the duration of ice-free conditions determines the food web development in the future. Fram Strait is one of the key regions for the Arctic: the cold water outflow comes through it with the East Greenland Current and meets warm Atlantic water, the West Spitsbergen Current, producing complicated hydrological situation. During 2007 and 2008 we investigated the structure functional characteristics of zooplankton community in the Fram Strait region onboard KV "Svalbard" (April 2007, April and May 2008) and RV "Jan Mayen" (May 2007, August 2008). This study was conducted in frame of iAOOS Norway project "Closing the loop", which, in turn, was a part of IPY. During this cruises multidisciplinary investigations were performed, including sea-ice observations, CTD and ADCP profiling, carbon flux, nutrients and primary production measurements, phytoplankton sampling. Zooplankton was collected with the Hydro-Bios WP2 net and MultiNet Zooplankton Sampler, (mouth area 0.25 m2, mesh size 180 um).Samples were taken from the depth strata of 2000-1500, 1500-1000, 1000-500,500-200, 200-100, 100-60, 60-30, 30-0 m. Gut fluorescence content were measured in dominant species to investigate effect of Chl a concentration and phytoplankton composition on ingestion rate. Egg production experiments were carried out under different food conditions. Rare deep water zooplankton species were also investigated to increase our knowledge in the Arctic biodiversity. Copepods Calanus finmarchicus is known as a marker of the Atlantic water mass, Calanus glacialis and Calanus hyperboreus, vice versa, are the coldwater Arctic species. In our study we investigated three Calanus species distribution and analyzed their ecological status. Changes in zooplankton composition results in the alteration of energy transfer within the pelagic food web ("cold" and "warm" scenarios) with potential consequences for growth and survival of seabirds Little Auk (Alle alle) and Black-legged kittiwake (Rissa tridactyla). We discuss the advection effect on the zooplankton community, compare the population development phases with phytoplankton bloom phases (match-mismatch), estimate grazing impact on phytoplankton community and consider different life strategies for the three different Calanus species.

Soloviev, K. A.; Dritz, A. V.; Nikishina, A. B.

2009-04-01

35

Continuous plankton recorder underestimates zooplankton abundance  

NASA Astrophysics Data System (ADS)

A comparison between monthly mean Continuous Plankton Recorder (CPR) data and zooplankton data caught during winter and early spring with different sampling devices in the North Sea is presented to estimate the relative error in abundance of CPR measurements. CPR underestimates the abundance of zooplankton by a factor 25 during winter and early spring and by a factor 18 if Oithona spp. is not considered. This has serious implications for estimation of biomass as well as for modelling ecosystem dynamics.

Dippner, Joachim W.; Krause, Michael

2013-02-01

36

Population dynamics of the ctenophore Mnemiopsis leidyi and its impact on the zooplankton in the coastal regions of the Black Sea of the Crimean coast in 2004-2008  

NASA Astrophysics Data System (ADS)

The abundance, biomasses, and population structure of the ctenophore Mnemiopsis leidyi were monitored in the coastal waters of the northern part of the Black Sea (Sevastopol Bay and the adjacent continental shelf regions) in 2004-2008. The abundance and species composition of the comb jelly's food in the sea were obtained along with experimental data on the digestion time. Based upon these data, the feeding intensity of the ctenophore in situ was estimated. This information was used to calculate the predatory impact of the comb jelly population on certain groups of forage organisms and the forage zooplankton community as a whole. The predatory impact of the M. leidyi population on the bivalve veligers was the highest (up to 90% of the abundance a day) compared to the Copepoda and Cladocera (30% and 40%, respectively). In the summers of 2004-2008, the daily consumption rates of the zooplankton by the ctenophore population in the shelf zone and in the bay were similar to each other: up to 15% and 12% of the abundance a day, respectively. The highest pressure of the ctenophore upon the zooplankton was observed in 2004 and 2008, when M. leidyi was especially abundant in the plankton for a long time.

Finenko, G. A.; Abolmasova, G. I.; Romanova, Z. A.; Datsyk, N. A.; Anninskii, B. E.

2013-02-01

37

Microplastic ingestion by zooplankton.  

PubMed

Small plastic detritus, termed "microplastics", are a widespread and ubiquitous contaminant of marine ecosystems across the globe. Ingestion of microplastics by marine biota, including mussels, worms, fish, and seabirds, has been widely reported, but despite their vital ecological role in marine food-webs, the impact of microplastics on zooplankton remains under-researched. Here, we show that microplastics are ingested by, and may impact upon, zooplankton. We used bioimaging techniques to document ingestion, egestion, and adherence of microplastics in a range of zooplankton common to the northeast Atlantic, and employed feeding rate studies to determine the impact of plastic detritus on algal ingestion rates in copepods. Using fluorescence and coherent anti-Stokes Raman scattering (CARS) microscopy we identified that thirteen zooplankton taxa had the capacity to ingest 1.7-30.6 ?m polystyrene beads, with uptake varying by taxa, life-stage and bead-size. Post-ingestion, copepods egested faecal pellets laden with microplastics. We further observed microplastics adhered to the external carapace and appendages of exposed zooplankton. Exposure of the copepod Centropages typicus to natural assemblages of algae with and without microplastics showed that 7.3 ?m microplastics (>4000 mL(-1)) significantly decreased algal feeding. Our findings imply that marine microplastic debris can negatively impact upon zooplankton function and health. PMID:23692270

Cole, Matthew; Lindeque, Pennie; Fileman, Elaine; Halsband, Claudia; Goodhead, Rhys; Moger, Julian; Galloway, Tamara S

2013-06-06

38

Impacts of reduced pH from ocean CO{sub 2} disposal: Sensitivity of zooplankton mortality to model parameters  

SciTech Connect

The authors have developed a methodology to quantify mortality suffered by marine zooplankton passing through a CO{sub 2}-enriched sea water plume. Here the authors explore model sensitivity to some of the more important biological, physical and engineering design parameters, with particular reference to CO{sub 2} injection as a buoyant droplet plume. Uncertainty in the dose-response relationship, e.g. caused by the use of data for surface organisms, will affect predicted values of total mortality by less than a factor of two for a single point discharge from 10 standard (500 MWe) coal-fired values of total mortality by less than a factor of two for a single point discharge from 10 standard 500 MWe coal-fired electric power plants and a factor of five for a single point discharge from one standard plant. The most important design variable is the number of physically separated discharge points (diffuser ports or groups of ports) used to disperse the CO{sub 2}. Predicted mortality drops to zero as the number of discharge points per standard plants exceeds two. Finally the most important physical parameters are ambient current speed and turbulent diffusivity. As with the dose-response data, most physical oceanographic measurements have been conducted near the ocean surface. Model sensitivity suggests that a factor of 2.5 reduction in current speed or a factor of 3 reduction in ambient diffusivity, relative to the base case, would require that the number of discharge points per standard plant increase from 2 to 12 in order to avoid mortality. Thus, impacts can be strongly site-specific, and additional oceanographic measurements are needed at depths appropriate for CO{sub 2} sequestration. Nonetheless, it should be easy to design an environmentally conservative multi-point discharge system that can disperse CO{sub 2} as a droplet plume without significant mortality, even under adverse environmental conditions.

Adams, E.E.; Caulfield, J.A.; Herzog, H.J.; Auerbach, D.I. [Massachusetts Inst. of Tech., Cambridge, MA (United States)

1998-07-01

39

Mesoscale Structure of Zooplankton in the California Current.  

National Technical Information Service (NTIS)

This collaborative project was designed to improve our quantiative understanding and predicitive abilities for zooplankton population dynamics, especially at the boundaries of distributions, through the use of specifically designed field efforts utilizing...

A. Bucklin D. B. Olson P. H. Wiebe

1999-01-01

40

Mesoscale Structure of Zooplankton in the California Current.  

National Technical Information Service (NTIS)

This collaborative project was designed to improve our quantitative understanding and predicative abilities for zooplankton population dynamics, especially at the boundaries of distributions, through the use of specifically designed field efforts utilizin...

A. Bucklin D. B. Olson P. H. Wiebe

2000-01-01

41

Introduction to Population Modeling.  

ERIC Educational Resources Information Center

|The focus is on the formulation and solution of mathematical models with the idea of a population employed mainly as a pedogogical tool. If the biological setting is stripped away, the material can be interpreted as topics or the qualitative behavior of differential and difference equations. The first group of models investigate the dynamics of a…

Frauenthal, James C.

42

The relationship between the water level of the Amazon River and the fate of the zooplankton population in lago Jacaretinga. A Várzea Lake in the Central Amazon  

Microsoft Academic Search

In a várzea lake of the Central Amazon the planktonic crustaceans disappear almost completely after the inflow of suspension?rich Amazon water. An initial small increase in numbers of individuals is accompanied by increased egg production in Diaphanosoma sarsi and Notodiaptomus amazonicus, suggesting an improved food supply for the Zooplankton. Possible reasons for the complete disappearance of the crustaceans are discussed,

E. R. de Andrade

1978-01-01

43

The growth rate of zooplankton at the edge of chaos: ecological models  

Microsoft Academic Search

This paper tests the hypothesis that systems at the edge of chaos have the highest level of (thermodynamic) information, which supports the hypothesis that systems at the edge of the chaos can coordinate the most complex behavior. This is examined by the use of a realistic ecological lake model describing how an ecological system behaves (i.e. chaotic or ordered), and

Sven Erik Jørgensen

1995-01-01

44

Responses in zooplankton populations to food quality and quantity changes after whole lake nutrient enrichment of an oligotrophic sub-alpine reservoir  

Microsoft Academic Search

.  To sustain production of higher trophic levels in oligotrophic systems it is important that the trophic transfer of energy\\u000a and nutrients is efficient. The phytoplankton-zooplankton interface is of specific interest since nutritional constraints\\u000a can decouple energy flow in this step. Increased nutrient loading to oligotrophic systems with initially low abundance of\\u000a high quality phytoplankton could induce changes in seston composition

Jonas Persson; Tobias Vrede; Staffan Holmgren

2008-01-01

45

Modelling Pseudocalanus elongatus stage-structured population dynamics embedded in a water column ecosystem model for the northern North Sea  

NASA Astrophysics Data System (ADS)

This paper outlines an approach to couple a structured zooplankton population model with state variables for eggs, nauplii, two copepodites stages and adults adapted to Pseudocalanus elongatus into the complex marine ecosystem model ECOHAM2 with 13 state variables resolving the carbon and nitrogen cycle. Different temperature and food scenarios derived from laboratory culture studies were examined to improve the process parameterisation for copepod stage dependent development processes. To study annual cycles under realistic weather and hydrographic conditions, the coupled ecosystem zooplankton model is applied to a water column in the northern North Sea. The main ecosystem state variables were validated against observed monthly mean values. Then vertical profiles of selected state variables were compared to the physical forcing to study differences between zooplankton as one biomass state variable or partitioned into five population state variables. Simulated generation times are more affected by temperature than food conditions except during the spring phytoplankton bloom. Up to six generations within the annual cycle can be discerned in the simulation.

Moll, Andreas; Stegert, Christoph

2007-01-01

46

Modeling Exponential Population Growth  

ERIC Educational Resources Information Center

|The concept of population growth patterns is a key component of understanding evolution by natural selection and population dynamics in ecosystems. The National Science Education Standards (NSES) include standards related to population growth in sections on biological evolution, interdependence of organisms, and science in personal and social…

McCormick, Bonnie

2009-01-01

47

SOME MECHANISTICALLY DERIVED POPULATION MODELS  

Microsoft Academic Search

The purpose of this talk is to mechanistically formulate a series of mathematically tractable population growth models that are implicitly or ex- plicitly dependent on resource dynamics.This series of models include Logistic equation, Holling type II predator prey model, Beddington-DeAngelis model, ratio-dependent model and the more recent stoichiometric population growth models. 1. Introduction. Predator-prey models are arguably the most basic

Yang Kuang

2007-01-01

48

Spatial and Temporal Variability of Zooplankton in a Great Plains Reservoir  

Microsoft Academic Search

Seasonal and daily patterns of zooplankton populations are often predictable in natural lakes. Distinct zonation and geomorphic differences in reservoirs, however, make ecological extrapolations from lakes to reservoirs uncertain. We describe the spatial and temporal distribution of zooplankton, algae, and water clarity across reservoir zones and along a depth gradient in Glen Elder Reservoir, Kansas. Daphnia species were most abundant

Randall J. Bernot; Walter K. Dodds; Michael C. Quist; Christopher S. Guy

2004-01-01

49

Zooplankton community responses to synthetic oil exposure  

SciTech Connect

The responses of microcosm and pond zooplankton communities to oil treatment were quite similar. Their close agreement lends support for using shallow-water pond microcosms as surrogates for field experiments in hazard evaluation. Changes in cladoceran densities were the most sensitive indicators of stress in the zooplankton communities. Copepods were slightly less sensitive, and rotifers were least sensitive to oil treatment. Indirect effects on populations were observed at intermediate treatment levels. The lowest treatment levels at which persistent and significant ecological changes occurred were the same in both systems. These levels were similar to the lowest observed-effect concentration (LOEC) for the Daphnia magna chronic bioassay, or approximately 30% of the D. magna 48-h LC/sub 50/. Community structure responses were generally consistent between systems; however, sensitivity for detecting oil treatment effects varied greatly among the measures of community structure. Species richness and diversity measures were not as sensitive as individual species responses. Cluster and multivariate post-clustering analyses of community similarity values reflected indirect effects and had sufficient sensitivity to allow early impact detection. An expanded principal components technique, which used both zooplankton and water quality data, was also relatively sensitive and would be applicable for routine monitoring.

Hook, L.A.; Franco, P.J.; Giddings, J.M.

1985-01-01

50

Optimal Foraging by Zooplankton  

NASA Astrophysics Data System (ADS)

We describe experiments with several species of the zooplankton, Daphnia, while foraging for food. They move in sequences: hop-pause-turn-hop etc. While we have recorded hop lengths, hop times, pause times and turning angles, our focus is on histograms representing the distributions of the turning angles. We find that different species, including adults and juveniles, move with similar turning angle distributions described by exponential functions. Random walk simulations and a theory based on active Brownian particles indicate a maximum in food gathering efficiency at an optimal width of the turning angle distribution. Foraging takes place within a fixed size food patch during a fixed time. We hypothesize that the exponential distributions were selected for survival over evolutionary time scales.

Garcia, Ricardo; Moss, Frank

2007-03-01

51

Modeling Population Growth and Extinction  

ERIC Educational Resources Information Center

|The exponential growth model and the logistic model typically introduced in the mathematics curriculum presume that a population grows exclusively. In reality, species can also die out and more sophisticated models that take the possibility of extinction into account are needed. In this article, two extensions of the logistic model are…

Gordon, Sheldon P.

2009-01-01

52

Biodiversity and ecosystem function in the Gulf of Maine: pattern and role of zooplankton and pelagic nekton.  

PubMed

This paper forms part of a broader overview of biodiversity of marine life in the Gulf of Maine area (GoMA), facilitated by the GoMA Census of Marine Life program. It synthesizes current data on species diversity of zooplankton and pelagic nekton, including compilation of observed species and descriptions of seasonal, regional and cross-shelf diversity patterns. Zooplankton diversity in the GoMA is characterized by spatial differences in community composition among the neritic environment, the coastal shelf, and deep offshore waters. Copepod diversity increased with depth on the Scotian Shelf. On the coastal shelf of the western Gulf of Maine, the number of higher-level taxonomic groups declined with distance from shore, reflecting more nearshore meroplankton. Copepod diversity increased in late summer, and interdecadal diversity shifts were observed, including a period of higher diversity in the 1990s. Changes in species diversity were greatest on interannual scales, intermediate on seasonal scales, and smallest across regions, in contrast to abundance patterns, suggesting that zooplankton diversity may be a more sensitive indicator of ecosystem response to inter annual climate variation than zoo plankton abundance. Local factors such as bathymetry, proximity of the coast, and advection probably drive zooplankton and pelagic nekton diversity patterns in the GoMA, while ocean-basin scale diversity patterns probably contribute to the increase in diversity at the Scotian Shelf break, a zone of mixing between the cold-temperate community of the shelf and the warm-water community offshore. Pressing research needs include establishment of a comprehensive system for observing change in zooplankton and pelagic nekton diversity, enhanced observations of "underknown" but important functional components of the ecosystem, population and metapopulation studies, and development of analytical modeling tools to enhance understanding of diversity patterns and drivers. Ultimately, sustained observations and modeling analysis of biodiversity must be effectively communicated to managers and incorporated into ecosystem approaches for management of GoMA living marine resources. PMID:21304990

Johnson, Catherine L; Runge, Jeffrey A; Curtis, K Alexandra; Durbin, Edward G; Hare, Jonathan A; Incze, Lewis S; Link, Jason S; Melvin, Gary D; O'Brien, Todd D; Van Guelpen, Lou

2011-01-31

53

Differential effects of zooplankton species on ciliate community structure  

Microsoft Academic Search

An in situ bioassay experiment using Diacyclops bicuspidatus thomasi, Daphnia rosea, Diaptomus novamexicanus, and Holopedium gibberum single-species treatments was conducted to assess the influence of these zooplankters on the ciliate community structure of Castle Lake, California. At peak ambient abundances for adult individuals, these zooplankters all strongly depressed ciliate population growth rates. The ranking of the zooplankton-imposed ciliate death rates,

KRZYSZTOF WIACKOWSKI; MICHAEL T. BRETT; CHARLES R. GOLDMAN

1994-01-01

54

Modeling sandhill crane population dynamics  

USGS Publications Warehouse

The impact of sport hunting on the Central Flyway population of sandhill cranes (Grus canadensis) has been a subject of controversy for several years. A recent study (Buller 1979) presented new and important information on sandhill crane population dynamics. The present report is intended to incorporate that and other information into a mathematical model for the purpose of assessing the long-range impact of hunting on the population of sandhill cranes.The model is a simple deterministic system that embodies density-dependent rates of survival and recruitment. The model employs four kinds of data: (1) spring population size of sandhill cranes, estimated from aerial surveys to be between 250,000 and 400,000 birds; (2) age composition in fall, estimated for 1974-76 to be 11.3% young; (3) annual harvest of cranes, estimated from a variety of sources to be about 5 to 7% of the spring population; and (4) age composition of harvested cranes, which was difficult to estimate but suggests that immatures were 2 to 4 times as vulnerable to hunting as adults.Because the true nature of sandhill crane population dynamics remains so poorly understood, it was necessary to try numerous (768 in all) combinations of survival and recruitment functions, and focus on the relatively few (37) that yielded population sizes and age structures comparable to those extant in the real population. Hunting was then applied to those simulated populations. In all combinations, hunting resulted in a lower asymptotic crane population, the decline ranging from 5 to 54%. The median decline was 22%, which suggests that a hunted sandhill crane population might be about three-fourths as large as it would be if left unhunted. Results apply to the aggregate of the three subspecies in the Central Flyway; individual subspecies or populations could be affected to a greater or lesser degree.

Johnson, D. H.

1979-01-01

55

Dependence of the rate of release of phosphorus by zooplankton on the P : C ratio in the food supply, as calculated by a recycling model1  

Microsoft Academic Search

In two enclosure experiments, Daphnia pulex ingested cryptophytes, bacteria, and probably detritus particles. The specific clearance rate of the zooplankton increased when the concentration of food decreased. The P : C ratio of the food also increased. More than 92% of the particulate phosphorus was located in the living cells (algae and bacteria); the detritus was practically phos- phorus-free. The

Yngvar Olsen; Arne Jensen; Helge Reinertsen; Knut Yngve Borsheim; Mikal Heldal; Arnjinn Langeland

1986-01-01

56

Planktivory in the changing Lake Huron zooplankton community: Bythotrephes consumption exceeds that of Mysis and fish  

USGS Publications Warehouse

Oligotrophic lakes are generally dominated by calanoid copepods because of their competitive advantage over cladocerans at low prey densities. Planktivory also can alter zooplankton community structure. We sought to understand the role of planktivory in driving recent changes to the zooplankton community of Lake Huron, a large oligotrophic lake on the border of Canada and the United States. We tested the hypothesis that excessive predation by fish (rainbow smelt Osmerus mordax, bloater Coregonus hoyi) and invertebrates (Mysis relicta, Bythotrephes longimanus) had driven observed declines in cladoceran and cyclopoid copepod biomass between 2002 and 2007. We used a field sampling and bioenergetics modelling approach to generate estimates of daily consumption by planktivores at two 91-m depth sites in northern Lake Huron, U.S.A., for each month, May-October 2007. Daily consumption was compared to daily zooplankton production. Bythotrephes was the dominant planktivore and estimated to have eaten 78% of all zooplankton consumed. Bythotrephes consumption exceeded total zooplankton production between July and October. Mysis consumed 19% of all the zooplankton consumed and exceeded zooplankton production in October. Consumption by fish was relatively unimportant - eating only 3% of all zooplankton consumed. Because Bythotrephes was so important, we explored other consumption estimation methods that predict lower Bythotrephes consumption. Under this scenario, Mysis was the most important planktivore, and Bythotrephes consumption exceeded zooplankton production only in August. Our results provide no support for the hypothesis that excessive fish consumption directly contributed to the decline of cladocerans and cyclopoid copepods in Lake Huron. Rather, they highlight the importance of invertebrate planktivores in structuring zooplankton communities, especially for those foods webs that have both Bythotrephes and Mysis. Together, these species occupy the epi-, meta- and hypolimnion, leaving limited refuge for zooplankton prey. Published 2011. This article is a US Government work and is in the public domain in the USA.

Bunnell, D. B.; Davis, B. M.; Warner, D. M.; Chriscinske, M. A.; Roseman, E. F.

2011-01-01

57

Canada's Population Health Model (POHEM)  

Microsoft Academic Search

This paper describes the Population Health Model (POHEM) developed by Statistics Canada and shows its usefulness in the evaluation of cancer control interventions and policy decision-making. Models of the costs of diagnosis and treatment of lung and breast cancer were developed and incorporated into POHEM. Then, POHEM was used to evaluate the economic impact of chemotherapy for advanced non-small cell

B. P Will; J.-M Berthelot; K. M Nobrega; W Flanagan; W. K Evans

2001-01-01

58

Terrorist population dynamics model.  

PubMed

A system that includes a number of terrorist cells is considered. The cells can consist of one or more terrorists. The current number of terrorist cells is further denoted by N(t), where t is a current time counted from any appropriate origin. The objective is to find the evolution of the system in terms of N(t) and some interpretable parameters, such as the initial number of the terrorist cells N0=N(0), the cell disabling rate constant lambda (or the cell half-life t1/2), and the rate of formation of new cells P. The cost-effectiveness analysis, performed in the framework of the model, reveals that the effectiveness of disabling a terrorist cell is getting worse after 2-3 half-lives of a cell, which shows that if the anti-terrorist actions have not reached their goal during that time, the respective policy should be considered for revision, using the risk assessment consideration. Another important issue raised concerns balancing the efforts related to counterterrorism actions inside the system and the efforts protecting its borders. The respective data analysis is suggested and illustrated using simulated data. PMID:16834631

Kaminskiy, Mark P; Ayyub, Bilal M

2006-06-01

59

Zooplankton community responses to chlorpyrifos in mesocosms under Mediterranean conditions.  

PubMed

The effects of chlorpyrifos (organophosphate insecticide) on zooplankton were studied in outdoor experimental tanks (mesocosms) sited in the Mediterranean Region (Madrid, Spain) at two nominal concentrations of chlorpyrifos (0.1 and 1 microg a.s./L applied as Chas 48) and control were used. Five tanks were used as control and the treatments were performed in quintuplicate. A single chlorpyrifos application simulating spray-drift was conducted. The population and community effects were analyzed by means of univariate statistics and through the multivariate principal response curves (PRC) technique. The most affected zooplankton taxa were cladocerans (Daphnia group galeata), copepods (cyclopoids and copepod nauplii) and rotifers (Keratella cochlearis) showing in all the cases significant decreases in abundance at 1 microg chlorpyrifos/L. The calculated NOEC was 0.1 microg/L for these taxa as well as for the community. The zooplankton community was considered to be recovered after 99 days post-application. The results of this experiment were similar to those derived from mesocosm/microcosm studies performed in temperate regions. This indicates that a chlorpyrifos concentration of 0.1 microg chlorpyrifos/L could be the appropriate safe level for zooplankton community in different climatic regions. However, at treatment level of 1.0 microg/L the time required for full recovery of the affected populations (particularly Cladocera) was longer than in the other experiments performed in temperate regions. PMID:17629945

López-Mancisidor, Patricia; Carbonell, Gregoria; Marina, Ana; Fernández, Carlos; Tarazona, José V

2007-08-09

60

A numerical simulation of the role of zooplankton in C, N and P cycling in Lake Kinneret, Israel  

Microsoft Academic Search

We quantify the role of zooplankton in nutrient cycles in Lake Kinneret, Israel, using field data and a numerical model. A coupled ecological and hydrodynamic model (Dynamic Reservoir Model (DYRESM)–Computational Aquatic Ecosystem Dynamics Model (CAEDYM)) was validated with an extensive field data set to simulate the seasonal dynamics of nutrients, three phytoplankton groups and three zooplankton groups. Parameterization of the

Louise C. Bruce; David Hamilton; Jörg Imberger; Gideon Gal; Moshe Gophen; Tamar Zohary; K. David Hambright

2006-01-01

61

Mechanism of phototaxis in marine zooplankton.  

PubMed

The simplest animal eyes are eyespots composed of two cells only: a photoreceptor and a shading pigment cell. They resemble Darwin's 'proto-eyes', considered to be the first eyes to appear in animal evolution. Eyespots cannot form images but enable the animal to sense the direction of light. They are characteristic for the zooplankton larvae of marine invertebrates and are thought to mediate larval swimming towards the light. Phototaxis of invertebrate larvae contributes to the vertical migration of marine plankton, which is thought to represent the biggest biomass transport on Earth. Yet, despite its ecological and evolutionary importance, the mechanism by which eyespots regulate phototaxis is poorly understood. Here we show how simple eyespots in marine zooplankton mediate phototactic swimming, using the marine annelid Platynereis dumerilii as a model. We find that the selective illumination of one eyespot changes the beating of adjacent cilia by direct cholinergic innervation resulting in locally reduced water flow. Computer simulations of larval swimming show that these local effects are sufficient to direct the helical swimming trajectories towards the light. The computer model also shows that axial rotation of the larval body is essential for phototaxis and that helical swimming increases the precision of navigation. These results provide, to our knowledge, the first mechanistic understanding of phototaxis in a marine zooplankton larva and show how simple eyespots regulate it. We propose that the underlying direct coupling of light sensing and ciliary locomotor control was a principal feature of the proto-eye and an important landmark in the evolution of animal eyes. PMID:19020621

Jékely, Gáspár; Colombelli, Julien; Hausen, Harald; Guy, Keren; Stelzer, Ernst; Nédélec, François; Arendt, Detlev

2008-11-20

62

Biological drivers of zooplankton patchiness  

Microsoft Academic Search

Until recently, biological drivers of plankton aggregation were under-appreciated, because most studies concentrated on physical processes. New technological advances, novel experiments and theory have shifted focus to the pivotal role of behaviour in plankton patch dynamics. Our review highlights four biological drivers of zooplankton spatial patchiness and brings together recent research on well studied marine and freshwater taxa, primarily copepods

Carol L. Folt; Carolyn W. Burns

1999-01-01

63

Zooplankton Distribution in Four Western Norwegian Fjords  

NASA Astrophysics Data System (ADS)

A multi-instrumental array constructed in the Laboratoire d'Ecologie du Plancton Marin in Villefranche sur mer, France, named the Underwater Video Profiler (UVP), was used to investigate the vertical distribution of zooplankton in four western Norwegian fjords in the summer 1996. Six distinct zoological groups were monitored. The fauna included: (a) small crustaceans (mainly copepods), (b) ctenophores (mainly lobates), (c) siphonophores (mainly physonects), (d) a scyphomedusa Periphylla periphylla, (e) chaetognaths and (f) appendicularians. The use of the non-disturbing video technique demonstrated that the distribution of large zooplankton is heterogeneous vertically and geographically. Furthermore, the abundance of non-migrating filter feeders in the deep basins of the fjords indicates that there is enough food (living and non-living particulate organic matter) to support their dietary needs. This adaptation may be considered as a strategy for survival in fjords. Specifically, living in dark, deep water reduces visual predation and population loss encountered in the upper layer due to advective processes.

Gorsky, G.; Flood, P. R.; Youngbluth, M.; Picheral, M.; Grisoni, J.-M.

2000-01-01

64

A 15-month study of zooplankton ingestion by farmed mussels ( Mytilus edulis) in Bantry Bay, Southwest Ireland  

NASA Astrophysics Data System (ADS)

There is a growing body of evidence to suggest that bivalve molluscs routinely ingest zooplankton. To elucidate further these observations, a 15-month study of zooplankton ingestion by farmed mussels was conducted using mussel long-lines in Bantry Bay, Ireland. Stomach content analysis of the mussels showed that there was evidence of zooplankton ingestion throughout the sampling period, but that highest mean numbers of zooplankters were ingested by mussels in the spring and summer months. Various zooplankton species were present in mussel stomachs. Harpacticoid copepods were found more often in stomach contents than calanoid copepods, probably due to their proximity to the bivalves' inhalent siphons. Barnacle cyprids featured in large numbers in stomach contents, but only for a period of 3 months which broadly corresponded with their pelagic phase. Sizes of ingested zooplankton ranged from 126 ?m to 6 mm, but more of the smaller zooplankters (e.g. crustacean nauplii) were ingested. When lengths of ingested copepods were compared with those found in plankton net samples, it was found that the net-sampled copepods were significantly larger than those found in mussel stomachs, suggesting that mussels select for smaller categories within the zooplankton available to them. Soft bodied zooplankton was rarely found in mussel stomachs but their absence may be due to rapid digestion or they may have been destroyed in the preservation process. Ingestion of zooplankton by bivalves is discussed in the context of the impacts mussel farms have on resident zooplankton populations.

Lehane, Clare; Davenport, John

2006-05-01

65

Resurrecting the ghost of competition past with dormant zooplankton eggs.  

PubMed

A common prediction of evolutionary theory is that the strength of interspecific competition should decline over time among sympatric populations of competing species. Here we provide experimental evidence of historical declines in competition effects among competing zooplankton populations. Using diapausing eggs, we resurrected clones of three species of zooplankton obtained from different periods of community assembly in a single lake. We show that clones of Daphnia ambigua obtained from early in assembly when D. ambigua was dominant became extinct in competition with clones of Daphnia pulicaria and Daphnia dentifera (the current lake dominants). In contrast, D. ambigua clones obtained from later in the lake's history experienced weaker competition effects and persisted with D. dentifera. While we cannot rule out the role of intraspecific competition within D. ambigua, our results are in line with the view that natural selection favors reduced interaction strength among co-occurring species, facilitating coexistence and population persistence. PMID:17238127

Steiner, Christopher F; Cáceres, Carla E; Smith, Sigrid D P

2007-01-19

66

Environmental variability and the population dynamics of the exotic Daphnia lumholtzi and native zooplankton in Lake Texoma, U.S.A  

Microsoft Academic Search

Daphnia lumholtzi has invaded the U.S. from its original distribution of Africa, southern Asia and Australia. We examined the factors that affected the abundance and distribution of D. lumholtzi during 1994–1995 in Lake Texoma, a large southern plains reservoir. Daphnia lumholtzi was most abundant during summer months when temperatures were highest. The population exhibited a distributional shift in mid July

Kirsten Work; Moshe Gophen

1999-01-01

67

Distribution and feeding of Benthosema glaciale in the western Labrador Sea: Fish-zooplankton interaction and the consequence to calanoid copepod populations  

NASA Astrophysics Data System (ADS)

This study evaluated the distribution of major calanoid copepods in the western Labrador Sea in relation to that of the myctophid Benthosema glaciale, and investigated patterns of prey composition and feeding periodicity by the latter to assess the potential impact of mesopelagic fish on copepod populations that reside in the deep ocean. Hydroacoustic surveys indicated that B. glaciale and the deep-scattering layer are widely distributed throughout the region with limited evidence of patchiness, with an average abundance of 6 fish m-2 and biomass of 9.3 g m-2. There was clear evidence of diurnal variations in feeding activity that was achieved through vertical migration from several hundred meters depths to the surface layer. B. glaciale fed principally on calanoid copepods, with prey size dependent on the length of the fish but the relative variability in prey size was independent of predator length. Average rations were generally less than 1% of body weight per day, and the patterns of diurnal vertical migration by myctophids suggest that individuals fed once every two days rather than daily. The estimated mortality caused by B. glaciale on the calanoid populations, which considers most sources of uncertainty, ranged from 0.002 to 1.8% d-1, with the mid-point of these estimates being ˜0.15% d-1, which is well below the estimated mortality rates of 10-20% d-1 based on vertical life tables. From observations from this and other ecosystems, understanding and contrasting the drivers of population dynamics and productivity of calanoid copepods in different deep basins of the North Atlantic will likely require a more comprehensive characterization of the plankton and pelagic and oceanic fish faunas of the epipelagic and mesopelagic zones and their trophic relationships and interactions.

Pepin, Pierre

2013-05-01

68

[Biochemical composition of crustacean zooplankton and their grazing on phytoplankton and ciliated protozoans in a recently founded reservoir (Sahela, Morocco].  

PubMed

In order to assess the impact of crustacean zooplankton on phytoplankton and protozoan ciliates in the Sahela reservoir under semi-arid climate, we conducted experiments during the period from July to December 1999 at the deepest point in the lake (15 m). Samplings and measurements were carried out in diffusion chambers submerged in situ over a period of 7 h without (control chambers) and with (experimental chambers) crustacean zooplankton. During these experiments, counts were conducted on phytoplankton and ciliates to determine the abundance and the mortality of these organisms due to zooplankton in each diffusion chambers at t = 0 and t = 7 h of incubation. The study showed that the growth rates of phytoplankton and ciliates populations varied between 0.02 and 0.05 h-1 and from 0.01 to 0.07 h-1, respectively. The mortality caused by zooplankton grazing fluctuated from 0.07 to 0.2 h-1 of phytoplankton and from 0.01 to 0.2 h-1 of ciliates. These mortalities were significantly and positively correlated with the growth rates (r = 0.8; p < 0.02; n = 9). Moreover, the heavy predation by the crustacean zooplankton was exerted on small-sized phytoplankton and ciliates and we demonstrated the relationships between protozoans and zooplankton for the transfer of matter and energy in aquatic food webs. Furthermore, the crustacean zooplankton metabolism was different, whether zooplankton was present in diffusion chambers or in the lake. PMID:14608696

Derraz, Khalid; Elalami, Rachid; Atiki, Ilham; Mhamdi, Mohamed Alaoui

2003-08-01

69

In hot water: zooplankton and climate change  

Microsoft Academic Search

An overview is provided of the observed and potential future responses of zooplankton communities to global warming. I begin by describing the importance of zooplankton in ocean ecosystems and the attributes that make them sensitive beacons of climate change. Global warming may have even greater repercussions for marine ecosystems than for terrestrial ecosystems, because temp- erature influences water column stability,

Anthony J. Richardson

2008-01-01

70

Calvert Cliffs zooplankton entrainment study. Final report  

SciTech Connect

Entrainment studies to evaluate plant effects on zooplankton were conducted at the Calvert Cliffs Nuclear Plant. Specific effects tested were (a) the spatial and temporal variation of zooplankton density; (b) pump sampling efficiency; (c) delayed mortality; (d) vital staining as an indicator of mortality.

Bradley, B.P.

1980-01-01

71

Zooplankton data: Vertical distributions of zooplankton in the Norweigian and Greenland Seas during summer, 1989  

SciTech Connect

Recent studies of zooplankton populations in the Greenland Sea have focused on processes at the Marginal Ice Zone (MIZ) and the areas immediately adjacent to it under the ice and in open water. These studies have shown a relatively short period of intense secondary productivity which is closely linked temporally and spatially to phytoplankton blooms occurring near the ice edge in spring and early summer. During the summer of 1989 we participated in a project focusing on benthic and water column processes in the basins of the Norwegian and Greenland Seas. This study allowed us to compare biological processes at the MIZ with those occurring in the open waters of the Greenland Sea, and to compare processes at both of these locations with those in the Norwegian Sea. The data presented in this report are the results of zooplankton net tows covering the upper 1000 meters of the water column over the Norwegian Sea basin and the Greenland Sea basin, and the upper 500 meters of open water adjacent to the MIZ in the Greenland Sea. Sampling was conducted between 12 and 29 July 1989.

Lane, P.V.Z.; Smith, S.L.; Schwarting, E.M.

1993-08-01

72

Fish Population Model for Instream Flow Assessment.  

National Technical Information Service (NTIS)

An age structured fish population model has been proposed that is responsive to flow variations that create changes in the density dependent factor, available habitat. The model was implemented for a smallmouth bass population. Simulation results, shown t...

F. M. Williams

1984-01-01

73

Zooplankton data report: Winter MIZEX, 1987  

SciTech Connect

The Marginal Ice Zone Experiment (MIZEX) was an interdisciplinary, international Arctic research program designed to study the atmospheric, oceanic, and ice interactions in the Fram Strait region of the Greenland Sea. This report focuses on zooplankton data collected during the winter MIZEX program of 1987. The primary objectives of our group during MIZEX 87 were to study the distribution of zooplankton species in relation to the ice-edge, the Polar Front, and the mesoscale eddy field, and to study zooplanktonic physiology just prior to the spring phytoplankton bloom. The data in this report are quantitative analyses of zooplankton samples collected while aboard the research vessel HAKON MOSBY during MIZEX 87. This is the third in a series of data reports on zooplankton collected in the Fram Strait region during the MIZEX project. A complete catalog of the reports generated from the MIZEX program is archived at the National Snow and Ice Data Center in Boulder, Colorado, USA. 1 ref., 3 tabs.

Smith, S.L.; Lane, P.V.Z.; Schwartling, E.M.; Beck, B.

1988-12-01

74

Population balance modeling in Simulink: PCSS  

Microsoft Academic Search

In this work we develop, demonstrate, and distribute the code for a new Simulink block that models the dynamic evolution of the population density function for a physical system which can be modeled by a population balance equation. The name of the block is PCSS, for population balance modeling using the conservation element\\/solution element method in Simulink. The block interfaces

Jeffrey D. Ward; Cheng-ching Yu

2008-01-01

75

Matrix population models from 20 studies of perennial plant populations  

USGS Publications Warehouse

Demographic transition matrices are one of the most commonly applied population models for both basic and applied ecological research. The relatively simple framework of these models and simple, easily interpretable summary statistics they produce have prompted the wide use of these models across an exceptionally broad range of taxa. Here, we provide annual transition matrices and observed stage structures/population sizes for 20 perennial plant species which have been the focal species for long-term demographic monitoring. These data were assembled as part of the 'Testing Matrix Models' working group through the National Center for Ecological Analysis and Synthesis (NCEAS). In sum, these data represent 82 populations with >460 total population-years of data. It is our hope that making these data available will help promote and improve our ability to monitor and understand plant population dynamics.

Ellis, Martha M.; Williams, Jennifer L.; Lesica, Peter; Bell, Timothy J.; Bierzychudek, Paulette; Bowles, Marlin; Crone, Elizabeth E.; Doak, Daniel F.; Ehrlen, Johan; Ellis-Adam, Albertine; McEachern, Kathryn; Ganesan, Rengaian; Latham, Penelope; Luijten, Sheila; Kaye, Thomas N.; Knight, Tiffany M.; Menges, Eric S.; Morris, William F.; den Nijs, Hans; Oostermeijer, Gerard; Quintana-Ascencio, Pedro F.; Shelly, J. Stephen; Stanley, Amanda; Thorpe, Andrea; Ticktin Tamara; Valverde, Teresa; Weekley, Carl W.

2012-01-01

76

Matrix population models from 20 studies of perennial plant populations  

USGS Publications Warehouse

Demographic transition matrices are one of the most commonly applied population models for both basic and applied ecological research. The relatively simple framework of these models and simple, easily interpretable summary statistics they produce have prompted the wide use of these models across an exceptionally broad range of taxa. Here, we provide annual transition matrices and observed stage structures/population sizes for 20 perennial plant species which have been the focal species for long-term demographic monitoring. These data were assembled as part of the "Testing Matrix Models" working group through the National Center for Ecological Analysis and Synthesis (NCEAS). In sum, these data represent 82 populations with >460 total population-years of data. It is our hope that making these data available will help promote and improve our ability to monitor and understand plant population dynamics.

Ellis, Martha M.; Williams, Jennifer L.; Lesica, Peter; Bell, Timothy J.; Bierzychudek, Paulette; Bowles, Marlin; Crone, Elizabeth E.; Doak, Daniel F.; Ehrlen, Johan; Ellis-Adam, Albertine; McEachern, Kathryn; Ganesan, Rengaian; Latham, Penelope; Luijten, Sheila; Kaye, Thomas N.; Knight, Tiffany M.; Menges, Eric S.; Morris, William F.; den Nijs, Hans; Oostermeijer, Gerard; Quintana-Ascencio, Pedro F.; Shelly, J. Stephen; Stanley, Amanda; Thorpe, Andrea; Ticktin Tamara; Valverde, Teresa; Weekley, Carl W.

2012-01-01

77

Optical control of fish and zooplankton populations  

Microsoft Academic Search

Aquatic food webs are affected from the bottom up by light through its effect on photosynthesis and productivity. But light also has a top-down effect, because it is crucial for the visual foraging efficiency in many fish. Here we present data suggesting that marine pelagic food webs are primarily structured top-down by light through its effect on vision in fish.

Dag L. Aksnes; Jens Nejstgaard; Eivind Sædberg; Tom Sørnes

2004-01-01

78

Amerciamysis bahia Stochastic Matrix Population Model for Laboratory Populations  

EPA Science Inventory

The population model described here is a stochastic, density-independent matrix model for integrating the effects of toxicants on survival and reproduction of the marine invertebrate, Americamysis bahia. The model was constructed using Microsoft® Excel 2003. The focus of the mode...

79

Sub-fossils of cladocerans in the surface sediment of 135 lakes as proxies for community structure of zooplankton, fish abundance and lake temperature  

Microsoft Academic Search

To elucidate the possibilities of using zooplankton remains in the surface sediment to describe present-days community structure and population dynamics of zooplankton, fish abundance and temperature, we compared contemporary data sampled in the pelagial during summer with the sediment record from the upper 1 cm of the sediment in 135 lakes covering a latitude gradient from Greenland in the north

Erik Jeppesen; Jens Peder Jensen; Torben L. Lauridsen; Susanne L. Amsinck; Kirsten Christoffersen; Martin Søndergaard; Stuart F. Mitchell

2003-01-01

80

Partitioning of polychlorinated biphenyls between Arctic seawater and size-fractionated zooplankton.  

PubMed

Concentrations of hydrophobic organic contaminants in zooplankton have been hypothesized to be governed by either near-equilibrium partitioning with surrounding water, growth dilution, or biomagnification. Concentrations of 17 polychlorinated biphenyls (PCBs) were measured in size-fractionated zooplankton, in phytoplankton (> 0.7 microm), and in the dissolved water phase (< 0.7 microm) in the surface water of the northern Barents Sea marginal ice zone east and north of Spitsbergen (Norway) and in the central Arctic Ocean at 89 degrees N. The linear partition model was used to indirectly assess if PCBs were equilibrated between water and the extractable organic matter (EOM) of zooplankton. As an independent test, the relation between the EOM-normalized partition coefficient (log K(EOM)) and trophic level (TL) of the zooplankton (based on delta 15N) was investigated. All log K-log K(OW) regressions were significant (n=18, p < 0.05, r2 = 0.65-0.95), being consistent with near-equilibrium partitioning and indirectly suggesting the absence of biomagnification. No correlation was found between log K(EOM) and TL, further supporting the apparent absence of biomagnification in zooplankton. One implication of these results is a reduced uncertainty in modeling of food web uptake, in which kinetic parameterizations of biodilution or biomagnification in zooplankton may be replaced by a simpler parameterization based on equilibrium partitioning. PMID:16833130

Sobek, Anna; Reigstad, Marit; Gustafsson, Orjan

2006-07-01

81

Modelling urban - rural population growth in China  

Microsoft Academic Search

The population of China is still growing despite a dramatic decline in fertility in the past two decades. There are marked urban - rural differentials in fertility and, as a result, the pace of urbanization has significant effects on population growth. In this research an attempt is made to model urban - rural population growth in China. A demoeconomic model

J Shen; N A Spence

1996-01-01

82

Fundamentals of population pharmacokinetic modelling: validation methods.  

PubMed

Population pharmacokinetic modelling is widely used within the field of clinical pharmacology as it helps to define the sources and correlates of pharmacokinetic variability in target patient populations and their impact upon drug disposition; and population pharmacokinetic modelling provides an estimation of drug pharmacokinetic parameters. This method's defined outcome aims to understand how participants in population pharmacokinetic studies are representative of the population as opposed to the healthy volunteers or highly selected patients in traditional pharmacokinetic studies. This review focuses on the fundamentals of population pharmacokinetic modelling and how the results are evaluated and validated. This review defines the common aspects of population pharmacokinetic modelling through a discussion of the literature describing the techniques and placing them in the appropriate context. The concept of validation, as applied to population pharmacokinetic models, is explored focusing on the lack of consensus regarding both terminology and the concept of validation itself. Population pharmacokinetic modelling is a powerful approach where pharmacokinetic variability can be identified in a target patient population receiving a pharmacological agent. Given the lack of consensus on the best approaches in model building and validation, sound fundamentals are required to ensure the selected methodology is suitable for the particular data type and/or patient population. There is a need to further standardize and establish the best approaches in modelling so that any model created can be systematically evaluated and the results relied upon. PMID:22799590

Sherwin, Catherine M T; Kiang, Tony K L; Spigarelli, Michael G; Ensom, Mary H H

2012-09-01

83

The application of a model with dynamic structure to simulate the effect of mass fish mortality on zooplankton structure in Lago di Annone  

Microsoft Academic Search

A mass mortality of the most abundant zooplanktophagous fish due to an infectious gill disease eliminated almost the entire\\u000a population of this species in the Eastern basin of the Lake Annone, Italy in'75-76, while no mortality occurred in the Western\\u000a basin. This event offered the opportunity to study whether a recently developed structural dynamic modelling approach would\\u000a be able to

S. E. Jørgensen; R. de Bernardi

1997-01-01

84

FUNCTIONAL BIOASSAYS UTILIZING ZOOPLANKTON: A COMPARISON  

EPA Science Inventory

Functional zooplankton bioassays based on ingestion, reproduction and respiration are described, with methods for a new ingestion bioassay included. ll bioassays are compared using three indices, including the variability of controls, the range of experimental responses, and a li...

85

Evidences for influence of a heterotrophic dinoflagellate (Noctiluca scintillans) on zooplankton community structure in a highly stratified basin  

NASA Astrophysics Data System (ADS)

Variations in mesozooplankton diversity, community structure, and species assemblage related to environmental variability have been discussed regarding the Sea of Marmara, with particular attention to regulation by the holozoic dinoflagellate Noctiluca scintillans. Temperature stands alone as the most important factor affecting species succession and community structure while Noctiluca significantly influences zooplankton abundance and diversity, and appears as the prevailing factor for non-temperature dependent patterns in the zooplankton community. Competition between Marmara zooplankton and Noctiluca for the same food resources could be an important factor, considering the high production of the species when compared to herbivorous and omnivorous zooplankters. Meanwhile, chlorophyll a recorded throughout the study period indicated a sufficient food supply that could promote continuous mesozooplankton production in the region. Therefore top-down regulation of the zooplankton community by Noctiluca may gain importance. Noctiluca differed from other r-strategists mainly by its high competitive ability, year round occurrence, and large cell size. Therefore, zooplankton could not compete with Noctiluca in the long-term and Noctiluca found an opportunity to increase its abundance before the settlement of distinct summer or winter communities. Enhanced abundance, year-round occurrence, and high condition of Noctiluca population indicated that optimum conditions had been achieved for explosive development of the species in the Sea of Marmara. Increasing dominance of Noctiluca in the Sea of Marmara points out that the species could have a stronger affect on zooplankton in the following years and interrupt trophic pathways by reducing fodder zooplankton biomass.

Y?lmaz, I. Noyan; Okus&,cedil; Erdo?an; Yüksek, Ahsen

2005-08-01

86

Estimating zooplankton biomass through image analysis  

Microsoft Academic Search

Zooplankton biomass can be reliably estimated by a non-destructive method based on the statistical relationship between biovolume and the contents of carbon and nitrogen. Integrated zooplankton biovolume and the corresponding organic C and N contents were analysed in paired fresh and fixed (hexamine-buffered formalin) samples. Sample biovolume was estimated through the integration of individual volumes obtained by semi-automatic image analysis

M. Alcaraz; E. Saiz; A. Calbet; I. Trepat; E. Broglio

2003-01-01

87

Modelling population growth vialaguerre-type exponentials  

Microsoft Academic Search

We use the Laguerre-type exponentials, i.e., eigenfunctions of the Laguerre-type derivatives, in order to construct new models for population growth. Relevant modifications of the classical exponential, logistic, and Volterra-Lotka models are investigated.

S. De Andreis; P. E. Ricci

2005-01-01

88

Fitting population models from field data  

Microsoft Academic Search

The application of population and community ecology to solving real-world problems requires population and community dynamics models that reflect the myriad patterns of interaction among organisms and between the biotic and physical environments. Appropriate models are not hard to construct, but the experimental manipulations needed to evaluate their defining coefficients are often both time consuming and costly, and sometimes environmentally

John M. Emlena; D. C. Freeman; M. D. Kirchhoff; C. L. Alados; J. Escos; J. J. Duda

2003-01-01

89

Delay eect in models of population growth  

Microsoft Academic Search

First, we systematize earlier results on the global stability of the model ? x + µx = f(x(· )) of population growth. Second, we investigate the eect of delay on the asymptotic behavior when the nonlinearity f is a unimodal function. Our results can be applied to several population models (7, 9-13) because the function f does not need to

Dang Vu Giang; Yongwimon Lenbury; Thomas I. Seidman

90

Spatial effects in discrete generation population models  

Microsoft Academic Search

A framework is developed for constructing a large class of discrete generation, continuous space models of evolving single species populations and finding their bifurcating patterned spatial distributions. Our models involve, in separate stages, the spatial redistribution (through movement laws) and local regulation of the population; and the fundamental properties of these events in a homogeneous environment are found. Emphasis is

C. Carrillo; P. Fife

2005-01-01

91

Population Modelling with M&M's[R  

ERIC Educational Resources Information Center

|Several activities in which population dynamics can be modelled by tossing M&M's[R] candy are presented. Physical activities involving M&M's[R] can be modelled by difference equations and several population phenomena, including death and immigration, are studied. (Contains 1 note.)|

Winkel, Brian

2009-01-01

92

Population Genetics Models of Local Ancestry  

PubMed Central

Migrations have played an important role in shaping the genetic diversity of human populations. Understanding genomic data thus requires careful modeling of historical gene flow. Here we consider the effect of relatively recent population structure and gene flow and interpret genomes of individuals that have ancestry from multiple source populations as mosaics of segments originating from each population. This article describes general and tractable models for local ancestry patterns with a focus on the length distribution of continuous ancestry tracts and the variance in total ancestry proportions among individuals. The models offer improved agreement with Wright–Fisher simulation data when compared to the state-of-the art and can be used to infer time-dependent migration rates from multiple populations. Considering HapMap African-American (ASW) data, we find that a model with two distinct phases of “European” gene flow significantly improves the modeling of both tract lengths and ancestry variances.

Gravel, Simon

2012-01-01

93

Climate warming and the decline of zooplankton in the California current  

SciTech Connect

Since 1951, the biomass of macrozooplankton in waters off southern California has decreased by 80 percent. During the same period, the surface layer warmed-by more than 1.5{degrees}C in some places-and the temperature differences across the thermocline increased. Increased stratification resulted in less lifting of the thermocline by wind-driven upwelling. A shallower source of upwelled waters provided less inorganic nutrient for new biological production and hence supported a smaller zooplankton population. Continued warming could lead to further decline of zooplankton. 10 refs., 5 figs.

Roemmich, D.; McGowan, J. [Univ. of California, San Diego, CA (United States)

1995-03-03

94

Zooplankton of the waters adjacent to the C. P. Crane generating station. Final report  

SciTech Connect

Zooplankton population in the Gunpowder River and its tributaries were sampled monthly from July, 1979-March, 1980 in a continuation of similar studies begun in March, 1979. The objective of the study was to determine the effect of the present once-through cooling system of the Crane Power Plant. The principal effect of the C.P. Crane generating station on zooplankton of the area is a displacement of an original freshwater community through the pumping of cooling water from Seneca Creek to Saltpeter Creek.

Grant, G.C.; Womack, C.J.; Olney, J.E.

1980-08-01

95

Dispersal Limitation, Invasion Resistance, and the Structure of Pond Zooplankton Communities  

Microsoft Academic Search

For a species to colonize a site it must both arrive there by dispersal from another site and maintain positive population growth in the local environment. I experi- mentally tested the role of dispersal limitation in structuring the zooplankton communities of fishless ponds in southwestern Michigan. An average of 12.9 new species of rotifers and crustaceans from the region were

Jonathan B. Shurin

2000-01-01

96

Predatory — prey relationships in subtropical zooplankton: water mite against cladocerans in an Argentine lake  

Microsoft Academic Search

In a small lake in northern Argentina pelagic water mite Piona sp. had the maximum of population density in January following with a five-day delay after the peak of zooplankton dominant — Daphnia laevis. The mite density was highly predicted by the previous variations of Daphnia density during 4 months of observation (December–March). Daphnia density was a negative delayed function

V. F. Matveev; C. C. Martinez; S. M. Frutos

1989-01-01

97

Water pollution by insecticides in an agricultural river basin. II. The zooplankton, bottom fauna, and fish  

Microsoft Academic Search

ABSTRACI' In 1959 and 1960, zooplankton, bottom fauna, and Fish populations were studied in a drainage system polluted with insecticides in northern Alabama. Toxaphcnc and BHC (benzene hcxachloridc) were present in all water samples collected in 1959 and 1960 in concentrations considered to be sublethal to aquatic animals in a single dose. There was no convincing cvidcnce that continuous toxaphenc

ALFRED R. GRZENDA; GERALD J. LAUER; H. PAGE NICHOLSON

1964-01-01

98

LIMNETIC ZOOPLANKTON OF LAKES IN KATMAI NATIONAL MONUMENT, ALASKA  

EPA Science Inventory

The limnetic zooplankton in lakes of the Naknek River system in southwestern Alaska was sampled extensively during 1962-63. The numerically dominant forms of limnetic zooplankton were Diaptomus, Cyclops, Daphnia, Bosmina, coregoni, Kellicotia, and Conochilus. Some littoral and be...

99

Zooplankton Community Composition in Nearshore Waters of Southern Lake Michigan.  

National Technical Information Service (NTIS)

Zooplankton samples collected in 1977 in the nearshore waters of southern Lake Michigan (0.4 km from shore) were analyzed to provide a bench mark on zooplankton community composition for comparison with future studies. Species composition, abundance, and ...

J. E. Gannon F. J. Bricker K. S. Bricker

1983-01-01

100

Influence of Pulsed Inflows and Nutrient Loading on Zooplankton and Phytoplankton Community Structure and Biomass in Microcosm Experiments Using Estuarine Assemblages  

Microsoft Academic Search

Productivity and community structure of phytoplankton and zooplankton are influenced by hydrologic disturbances in many ways. In a recent modeling study it was suggested that pulsed inflows might enhance zooplankton performance, curb accumulation of phytoplankton accumulated biomass, and promote phytoplankton species diversity. We tested these predictions by performing microcosm experiments on natural plankton assemblages from the Nueces Delta, TX, USA.

Yesim Buyukates; Daniel Roelke

2005-01-01

101

Speciation patterns and processes in the zooplankton of the ancient lakes of Sulawesi Island, Indonesia  

PubMed Central

Although studies of ancient lake fauna have provided important insights about speciation patterns and processes of organisms in heterogeneous benthic environments, evolutionary forces responsible for speciation in the relatively homogenous planktonic environment remain largely unexplored. In this study, we investigate possible mechanisms of speciation in zooplankton using the freshwater diaptomids of the ancient lakes of Sulawesi, Indonesia, as a model system. We integrate phylogenetic and population genetic analyses of mitochondrial and nuclear genes with morphological and genome size data. Overall, our results support the conclusion that colonization order and local adaptation are dominant at the large, island scale, whereas at local and intralacustrine scales, speciation processes are regulated by gene flow among genetically differentiated and locally adapted populations. In the Malili lakes, the diaptomid populations are homogenous at nuclear loci, but show two highly divergent mitochondrial clades that are geographically restricted to single lakes despite the interconnectivity of the lake systems. Our study, based on coalescent simulations and population genetic analyses, indicates that unidirectional hybridization allows gene flow across the nuclear genome, but prevents the introgression of mitochondria into downstream populations. We suggest that hybridization and introgression between young lineages is a significant evolutionary force in freshwater plankton.

Vaillant, James J; Bock, Dan G; Haffner, G Douglas; Cristescu, Melania E

2013-01-01

102

Speciation patterns and processes in the zooplankton of the ancient lakes of Sulawesi Island, Indonesia.  

PubMed

Although studies of ancient lake fauna have provided important insights about speciation patterns and processes of organisms in heterogeneous benthic environments, evolutionary forces responsible for speciation in the relatively homogenous planktonic environment remain largely unexplored. In this study, we investigate possible mechanisms of speciation in zooplankton using the freshwater diaptomids of the ancient lakes of Sulawesi, Indonesia, as a model system. We integrate phylogenetic and population genetic analyses of mitochondrial and nuclear genes with morphological and genome size data. Overall, our results support the conclusion that colonization order and local adaptation are dominant at the large, island scale, whereas at local and intralacustrine scales, speciation processes are regulated by gene flow among genetically differentiated and locally adapted populations. In the Malili lakes, the diaptomid populations are homogenous at nuclear loci, but show two highly divergent mitochondrial clades that are geographically restricted to single lakes despite the interconnectivity of the lake systems. Our study, based on coalescent simulations and population genetic analyses, indicates that unidirectional hybridization allows gene flow across the nuclear genome, but prevents the introgression of mitochondria into downstream populations. We suggest that hybridization and introgression between young lineages is a significant evolutionary force in freshwater plankton. PMID:24101996

Vaillant, James J; Bock, Dan G; Haffner, G Douglas; Cristescu, Melania E

2013-08-01

103

Analysis of six groups of zooplankton in samples taken in 1978/79 at the proposed OTEC site in the Eastern Gulf of Mexico off Tampa Bay  

SciTech Connect

Zooplankton populations have been sampled from various depths in the region of the proposed Ocean thermal energy conversion site in the Gulf of Mexico. Data are presented on the numbers and species present at each depth sampled. (DMC)

Flock, M.E.; Hopkins T.L.

1981-05-01

104

A Population Health Model for Integrated Assessment Models  

SciTech Connect

This paper presents the initial results of a project to develop a population health model so we can extend the scenarios included in the IPCC's Special Report on Emissions Scenarios to include population health status.

Pitcher, Hugh M.; Ebi, Kristie L.; Brenkert, Antoinette L.

2008-05-01

105

Robust population management under uncertainty for structured population models.  

PubMed

Structured population models are increasingly used in decision making, but typically have many entries that are unknown or highly uncertain. We present an approach for the systematic analysis of the effect of uncertainties on long-term population growth or decay. Many decisions for threatened and endangered species are made with poor or no information. We can still make decisions under these circumstances in a manner that is highly defensible, even without making assumptions about the distribution of uncertainty, or limiting ourselves to discussions of single, infinitesimally small changes in the parameters. Suppose that the model (determined by the data) for the population in question predicts long-term growth. Our goal is to determine how uncertain the data can be before the model loses this property. Some uncertainties will maintain long-term growth, and some will lead to long-term decay. The uncertainties are typically structured, and can be described by several parameters. We show how to determine which parameters maintain long-term growth. We illustrate the advantages of the method by applying it to a Peregrine Falcon population. The U.S. Fish and Wildlife Service recently decided to allow minimal harvesting of Peregrine Falcons after their recent removal from the Endangered Species List. Based on published demographic rates, we find that an asymptotic growth rate lambda > 1 is guaranteed with 5% harvest rate up to 3% error in adult survival if no two-year-olds breed, and up to 11% error if all two-year-olds breed. If a population growth rate of 3% or greater is desired, the acceptable error in adult survival decreases to between 1% and 6% depending of the proportion of two-year-olds that breed. These results clearly show the interactions between uncertainties in different parameters, and suggest that a harvest decision at this stage may be premature without solid data on adult survival and the frequency of breeding by young adults. PMID:18213961

Deines, A; Peterson, E; Boeckner, D; Boyle, J; Keighley, A; Kogut, J; Lubben, J; Rebarber, R; Ryan, R; Tenhumberg, B; Townley, S; Tyre, A J

2007-12-01

106

Seasonal cycles of zooplankton from San Francisco Bay  

USGS Publications Warehouse

The two estuarine systems composing San Francisco Bay have distinct zooplankton communities and seasonal population dynamics. In the South Bay, a shallow lagoon-type estuary, the copepods Acartia spp. and Oithona davisae dominate. As in estuaries along the northeast coast of the U.S., there is a seasonal succession involving the replacement of a cold-season Acartia species (A. clausi s.l.) by a warm-season species (A. californiensis), presumably resulting from the differential production and hatching of dormant eggs. Oithona davisae is most abundant during the fall. Copepods of northern San Francisco Bay, a partially-mixed estuary of the Sacramento-San Joaquin Rivers, organize into discrete populations according to salinity distribution: Sinocalanus doerrii (a recently introduced species) at the riverine boundary, Eurytemora affinis in the oligohaline mixing zone, Acartia spp. in polyhaline waters (18-30\\%), and neritic species (e.g., Paracalanus parvus) at the seaward boundary. Sinocalanus doerrii and E. affinis are present year-round. Acartia clausi s.l. is present almost year-round in the northern reach, and A. californiensis occurs only briefly there in summer-fall. The difference in succession of Acartia species between the two regions of San Francisco Bay may reflect differences in the seasonal temperature cycle (the South Bay warms earlier), and the perennial transport of A. clausi s.l. into the northern reach from the seaward boundary by nontidal advection. Large numbers (>106 m-3) of net microzooplankton (>64 ??m), in cluding the rotifer Synchaeta sp. and three species of tintinnid ciliates, occur in the South Bay and in the seaward northern reach where salinity exceeds about 5-10??? Maximum densities of these microzooplankton are associated with high concentrations of chlorophyll. Meroplankton (of gastropods, bivalves, barnacles, and polychaetes) constitute a large fraction of zooplankton biomass in the South Bay during winter-spring and in the northern reach during summer-fall. Seasonal cycles of zooplankton abundance appear to be constant among years (1978-1981) and are similar in the deep (>10 m) channels and lateral shoals (<3 m). The seasonal zooplankton community dynamics are discussed in relation to: (1) river discharge which alters salinity distribution and residence time of plankton; (2) temperature which induces production and hatching of dormant copepod eggs; (3) coastal hydrography which brings neritic copepods of different zoogeographic affinities into the bay; and (4) seasonal cycles of phytoplankton. ?? 1985 Dr W. Junk Publishers.

Ambler, J. W.; Cloern, J. E.; Hutchinson, A.

1985-01-01

107

The Ramsey model with logistic population growth  

Microsoft Academic Search

In standard economic growth theory it is assumed that labor force follows exponential growth, a not realistic assumption. As described in Maynard Smith (1974), the growth of natural populations is more accurately depicted by a logistic growth law. In this paper we analyze how the Ramsey growth model is affected by logistic growth of population, comparing it with the classic

Juan Gabriel Brida; Elvio Accinelli

2007-01-01

108

The Career Counseling with Underserved Populations Model  

ERIC Educational Resources Information Center

|Providing effective career counseling to culturally diverse individuals is not the same as helping those from majority cultures. The Career Counseling With Underserved Populations model aids career counselors in supporting underserved populations as they strive to address their important career counseling issues.|

Pope, Mark

2011-01-01

109

Modeling the Population Dynamics of Pacific Yew.  

National Technical Information Service (NTIS)

A study of Pacific yew (Taxus brevifolia Nutt.) population dynamics in the mountains of western Oregon and Washington was based on a combination of long-term population data and computer modeling. Rates of growth and mortality were low in mature and old-g...

R. T. Busing T. A. Spies

1995-01-01

110

The link between environmental variation and evolutionary shifts in dormancy in zooplankton.  

PubMed

Sex and dormancy are intertwined in organisms that engage in asexual and sexual reproduction. The transition between asexual and sexual reproduction typically results in a dormant stage that provides a mechanism for persisting under harsh environmental conditions. For example, many zooplankton engage in sexual reproduction when environmental conditions deteriorate and produce resting eggs that remain viable for decades. It has long been assumed that observed variation in the timing and magnitude of investment into a dormant stage among populations or species reflects local environmental conditions. Yet, the importance of dormancy for the persistence of a given population can differ dramatically among habitats (i.e., permanent vs. seasonal ponds). As a result, environmental conditions may exert selection on the propensity for zooplankton to engage in sexual reproduction and enter dormancy in natural populations. Here, I highlight a growing body of research illustrating an important link between environmental conditions and divergent reproductive strategies in zooplankton. I specifically: (1) review the environmental cues that initiate a transition between asexual and sexual reproduction in zooplankton and (2) describe recent work demonstrating an evolutionary consequence of ecological selective pressures, such as predation and habitat predictability, on variation in the extent to which organisms engage in sex and enter dormancy. Such results have implications for the genetics and ecology of these organisms. PMID:23630969

Walsh, Matthew R

2013-04-29

111

Population Models: Stability in One Dimension1  

Microsoft Academic Search

Some of the simplest models of population growth are one dimensional nonlinear difference equations. While such models can display wild behavior in- cluding chaos, the standard biological models have the interesting property that they display global stability if they display local stability. Various researchers have sought a simple explanation for this agreement of local and global stability. Here, we show

Paul Cull

2006-01-01

112

Stellar population models at high spectral resolution  

Microsoft Academic Search

We present new, high-to-intermediate spectral resolution stellar population models, based on four popular libraries of empirical stellar spectra, namely Pickles, ELODIE, STELIB and MILES. These new models are the same as our previous models, but with higher resolution and based on empirical stellar spectra, while keeping other ingredients the same including the stellar energetics, the atmospheric parameters and the treatment

C. Maraston; G. Strömbäck

2011-01-01

113

Fluctuations in a coupled population model  

NASA Astrophysics Data System (ADS)

We investigate a discrete Markov process in which the immigration of individuals into one population is controlled by the fluctuations in another. We examine the effect of coupling back the second population to the first through a similar mechanism and derive exact solutions for the generating functions of the population statistics. We show that a stationary state exists over a certain parameter range and obtain expressions for moments and correlation functions in this regime. When more than two populations are coupled, cyclically transient oscillations and periodic behaviour of correlation functions are predicted. We demonstrate that if the initial distribution of either population is stable, or more generally has a power-law tail that falls off like N-(1+?) (0 < ? < 1), then for certain parameter values there exists a stationary state that is also power law but not stable. This stationary state cannot be accessed from a single multiple immigrant population model, but arises solely from the nonlinear interaction of the coupled system.

Jakeman, E.; Hopcraft, K. I.; Matthews, J. O.

2005-07-01

114

Population-expression models of immune response.  

PubMed

The immune response to a pathogen has two basic features. The first is the expansion of a few pathogen-specific cells to form a population large enough to control the pathogen. The second is the process of differentiation of cells from an initial naive phenotype to an effector phenotype which controls the pathogen, and subsequently to a memory phenotype that is maintained and responsible for long-term protection. The expansion and the differentiation have been considered largely independently. Changes in cell populations are typically described using ecologically based ordinary differential equation models. In contrast, differentiation of single cells is studied within systems biology and is frequently modeled by considering changes in gene and protein expression in individual cells. Recent advances in experimental systems biology make available for the first time data to allow the coupling of population and high dimensional expression data of immune cells during infections. Here we describe and develop population-expression models which integrate these two processes into systems biology on the multicellular level. When translated into mathematical equations, these models result in non-conservative, non-local advection-diffusion equations. We describe situations where the population-expression approach can make correct inference from data while previous modeling approaches based on common simplifying assumptions would fail. We also explore how model reduction techniques can be used to build population-expression models, minimizing the complexity of the model while keeping the essential features of the system. While we consider problems in immunology in this paper, we expect population-expression models to be more broadly applicable. PMID:23735782

Stromberg, Sean P; Antia, Rustom; Nemenman, Ilya

2013-06-04

115

Zooplankton van het Veerse Meer in 1987 (Zooplankton of the Veerse Lake in 1987),  

National Technical Information Service (NTIS)

Fourteen zooplankton groups were found in Lake Veere. In 1987 6 groups dominated in numbers as well as in biomass: Rotifera, Polychaeta (larvae of Polydora spp.), Copepoda, Cirripedia (larvae of Balanus spp.), Bivalvia (larvae) and Gastropoda (larvae). Sm...

N. J. P. Revis C. Bakker

1988-01-01

116

Design issues for population growth models  

PubMed Central

We briefly review and discuss design issues for population growth and decline models. We then use a flexible growth and decline model as an illustrative example and apply optimal design theory to find optimal sampling times for estimating model parameters, specific parameters and interesting functions of the model parameters for the model with two real applications. Robustness properties of the optimal designs are investigated when nominal values or the model is mis-specified, and also under a different optimality criterion. To facilitate use of optimal design ideas in practice, we also introduce a website for generating a variety of optimal designs for popular models from different disciplines.

Lopez Fidalgo, J.; Ortiz Rodriguez, I.M.

2010-01-01

117

Exploring Physical and Biological Mechanisms for Zooplankton Retention in the Estuarine Transition Zone of a Riverine Estuary  

NASA Astrophysics Data System (ADS)

In this study, we use a coupled three-dimensional physical-biological model to investigate zooplankton retention in the estuarine transition zone (ETZ) of the St. Lawrence Estuary (SLE). Varying from well-mixed to partially stratified, the hydrodynamic environment of the SLE is defined by a large tidal range, strong salinity gradients, a large freshwater river flow, and complex bathymetry. The physical-biological model used for this study consisted of two parts: a circulation model and a zooplankton transport model. The circulation model is a three-dimensional Eulerian hydrodynamic model (TRIM3D) driven by the wind, tides, and freshwater outflow. The zooplankton transport model is a three-dimensional Lagrangian particle tracking model which simulates zooplankton movement using velocity fields derived from the three-dimensional circulation model. The circulation model is calibrated using field data such as salinity, pressure, and current time series from different locations in the ETZ. The transport and distribution of three zooplankton taxa, non-native zebra mussel veligers, resident mysids, and larval smelt, were simulated for this study. By simulating these three taxa, we were able to investigate the effect of a range of swimming speeds on zooplankton retention in the ETZ. We present the results of simulations exploring the efficiency of tidal vertical migration, a commonly described biological retention mechanism that is characterized by zooplankton migration up to the surface on flood and down to the bottom on ebb. Tidal vertical migration, also known as selective tidal stream transport, was investigated for several swimming speeds and endogenous rhythms.

Simons, R. D.; Monismith, S. G.

2002-12-01

118

ZOOPLANKTON NUTRITIONAL VALUE: NURSERY POND FERTILIZATION EFFECTS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Little information is available on the utilization of natural productivity (i.e. zooplankton) by catfish fry. Although fry and fingerlings survive on prepared diets, many nutrients acquired by fry in ponds are most likely derived from natural food consumption. Experiments were conducted to answer ...

119

COMPARATIVE STUDIES ON ESTUARINE ZOOPLANKTON1  

Microsoft Academic Search

ABSTBACI' The seasonal cycle of zooplankton in Raritan Bay, New Jersey, was compared with Nar- ragansett Bay, Rhode Island, and the York River, Virginia, to determine the effects of local conditions on latitudinal gradients in species distributions. The dominant copepods in each estuary, Acartia cluusi and A. tonsu, alternated cycles of abundance in a similar and predictable manner, and the

120

PM POPULATION EXPOSURE AND DOSE MODELS  

EPA Science Inventory

The overall objective of this study is the development of a refined probabilistic exposure and dose model for particulate matter (PM) suitable for predicting PM10 and PM2.5 population exposures. This modeling research will be conducted both in-house by EPA scientists and through...

121

Modelling activated sludge flocculation using population balances  

Microsoft Academic Search

Activated sludge flocculation was modelled using population balances. The model followed the dynamics of activated sludge flocculation providing a good approximation of the change in mean floc size with time. Increasing the average velocity gradient decreased the final floc size. The breakage rate coefficient and collision efficiency also varied with the average velocity gradient. A power law relationship was found

C. A. Biggs; P. A. Lant

2002-01-01

122

Revisiting binary stars in population synthesis models  

NASA Astrophysics Data System (ADS)

We report results of a population synthesis model that follows the evolution of single and binary stars. In this model, we include the two He white dwarfs merger channel, suggested by Han et al., for the formation of extreme horizontal branch (EHB) stars. The physical parameters of the resulting EHB stars are derived from the Bag of Stellar Tracks and Isochrones data base by Pietrinferni et al., and are thus realistic and observationally supported. The predictions of this model are in good agreement with traditional population synthesis models, except when the spectrum of the stellar population is dominated by binary stars or their products, e.g., EHB stars in the ultraviolet (UV) of early-type galaxies (ETGs). We reproduce successfully the observed colour-magnitude diagram and spectral energy distribution of the metal-rich open cluster NGC 6791. The stellar population in this cluster may be archetypal of the stellar population in ETGs that show the UV excess phenomenon. Our models should be appropriate to study the UV upturn in ETGs.

Hernández-Pérez, Fabiola; Bruzual, Gustavo

2013-05-01

123

A diffusion model for geographically structured populations  

Microsoft Academic Search

Summary  A diffusion model is derived for the evolution of a diploid monoecious population under the influence of migration, mutation,\\u000a selection, and random genetic drift. The population occupies an unbounded linear habitat; migration is independent of genotype,\\u000a symmetric, and homogeneous. The treatment is restricted to a single diallelic locus without dominance. With the customary\\u000a diffusion hypotheses for migration and the assumption

Thomas Nagylaki

1978-01-01

124

Modelling protein crystallisation using morphological population balance models  

Microsoft Academic Search

Protein crystallisation is known to be affected by many factors and inherently difficult to control. Being able to model the crystal growth behaviour, especially at process scale for the population of particles in a crystalliser will no doubt greatly help the formulation and controlled manufacture of protein crystals. In this paper, a morphological population balance model for crystallisation of tetragonal

Jing J. Liu; Cai Y. Ma; Yang D. Hu; Xue Z. Wang

2010-01-01

125

Regulation of Mnemiopsis leidyi dynamics by potential changes in temperature and zooplankton conditions in the Black Sea.  

NASA Astrophysics Data System (ADS)

Providing a comprehensive understanding of the effects that cause formations of ctenophore blooms in the Black Sea is the main objective of this study. In order to analyse ctenophore dynamics in the Black Sea a zero-dimensional population based model of the ctenophore Mnemiopsis leidyi is developed. The stage resolving ctenophore model combines the modified form of stage resolving approach of Fennel, 2001 with the growth dynamics model of Kremer, 1976; Kremer and Reeve, 1989 under 4 stages of model-ctenophore. These stages include the different growth characteristics of egg, juvenile, transitional and adult stages. The dietary patterns of the different stages follows the observations obtained from the literature. The model is able to represent consistent development patterns, while reflecting the physiological complexity of a population of Mnemiopsis leidyi. Model results suggest that different nutritional requirement of each stage may serve as the bottlenecks for population growth and only when growth conditions are favorable for both larval and lobate stages, the high overall population growth rates may occur. Model is also used to analyse the influence of climatic changes on Mnemiopsis leidyi reproduction and outburst. This study presents and discussed how potential changes in temperature and zooplankton conditions in the Black Sea may regulate Mnemiopsis leidyi dynamics.

Salihoglu, B.; Fach, B.; Oguz, T.

2009-04-01

126

Population Models: Stability in One Dimension 1  

Microsoft Academic Search

Some of the simplest models of population growth are one dimensional nonlinear difference equations. While such models can\\u000a display wild behavior including chaos, the standard biological models have the interesting property that they display global\\u000a stability if they display local stability. Various researchers have sought a simple explanation for this agreement of local\\u000a and global stability. Here, we show that

Paul Cull

2007-01-01

127

ROLE OF ZOOPLANKTON IN CATFISH FRY CULTURE: SUMMARY OF NWAC INVESTIGATIONS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Experiments were conducted to answer the following questions: 1) Do catfish fry readily consume zooplankton? 2) If so, are specific zooplankton selected? 3) Within the zooplankton groups consumed, is there size discrimination by fry? 4) What is the nutritional value of zooplankton? 5) Is zooplankton...

128

Effects of ultraviolet radiation and dissolved organic carbon on the survival of subarctic zooplankton  

Microsoft Academic Search

High intensities of ultraviolet radiation are known to be harmful to aquatic biota, especially for species living in shallow, clear water bodies. Zooplankton species from such habitats are good model organisms to study the effect of changes in UV radiation, and how animals deal with this. We tested experimentally the effect of natural UV radiation, which was controlled by different

Milla Rautio; Atte Korhola

2002-01-01

129

Nonlinear stochastic modeling of aphid population growth.  

PubMed

This paper develops a stochastic population size model for the black-margined pecan aphid. Prajneshu [Prajneshu, A nonlinear statistical model for aphid population growth. J. Indian Soc. Agric. Statist. 51 (1998), p. 73] proposes a novel nonlinear deterministic model for aphid abundance. The per capita death rate in his model is proportional to the cumulative population size, and the solution is a symmetric analytical function. This paper fits Prajneshu's deterministic model to data. An analogous stochastic model, in which both the current and the cumulative aphid counts are state variables, is then proposed. The bivariate solution of the model, with parameter values suggested by the data, is obtained by solving a large system of Kolmogorov equations. Differential equations are derived for the first and second order cumulants, and moment closure approximations are obtained for the means and variances by solving the set of only five equations. These approximations, which are simple for ecologists to calculate, are shown to give accurate predictions of the two endpoints of applied interest, namely (1) the peak aphid count and (2) the final cumulative aphid count. PMID:16183082

Matis, James H; Kiffe, Thomas R; Matis, Timothy I; Stevenson, Douglass E

2005-09-23

130

Latent variable modeling in heterogeneous populations  

Microsoft Academic Search

Common applications of latent variable analysis fail to recognize that data may be obtained from several populations with different sets of parameter values. This article describes the problem and gives an overview of methodology that can address heterogeneity. Artificial examples of mixtures are given, where if the mixture is not recognized, strongly distorted results occur. MIMIC structural modeling is shown

Bengt O. Muthén

1989-01-01

131

Modelling the Economic Effects of Population Ageing  

Microsoft Academic Search

In March 2005, the Productivity Commission released a report on the Economic Implications of an Ageing Australia. The report describes projections for a number of economic variables including population, labour force participation rates, labour supply, employment and hours worked per week. The present paper describes a number of simulations with the MONASH model designed to extend the range of the

James Giesecke; G. A. Meagher

2008-01-01

132

Population mixture model for nonlinear telomere dynamics  

NASA Astrophysics Data System (ADS)

Telomeres are DNA repeats protecting chromosomal ends which shorten with each cell division, eventually leading to cessation of cell growth. We present a population mixture model that predicts an exponential decrease in telomere length with time. We analytically solve the dynamics of the telomere length distribution. The model provides an excellent fit to available telomere data and accounts for the previously unexplained observation of telomere elongation following stress and bone marrow transplantation, thereby providing insight into the nature of the telomere clock.

Itzkovitz, Shalev; Shlush, Liran I.; Gluck, Dan; Skorecki, Karl

2008-12-01

133

Power-plant-related estuarine zooplankton studies  

SciTech Connect

In-plant studies examining the effects of entrainment on zooplankton and field studies examining zooplankton abundance, composition, and distribution in the Chesapeake Bay in the vicinity of Calvert Cliffs Nuclear Power Plant have been conducted from 1974 to the present. The evolution of these studies, with particular emphasis on design and statistical treatment, is discussed. Entrainment study designs evolved from discrete sampling episodes at 4-h intervals over 24 h to a time-series sampling design in which sampling took place every 30 min over 24 and 48-h periods. The near-field study design and samping methods have included replicated net tows, using 0.5-m nets, and replicated and nonreplicated pumped sampling, using a high-speed centrifugal pump. 16 refs.

Sage, L.E.; Olson, M.M.

1981-01-01

134

Model population upgrades based on recent observations  

NASA Astrophysics Data System (ADS)

The ESA MASTER model predicts the object flux on an arbitrary object in space by simulating all source terms contributing to the Earth environment in a semi-deterministic way. One of the main problems in the past was the incompatibility of flux predictions returned by the model with detection rates achieved by radar or optical observation campaigns. The ESA PROOF tool lately closed this gap by providing a set of filter mechanisms to simulate the observation campaigns in detail from geometrical crossing up to detection by individual devices. For the first time, this tool allowed a detailed comparison of model predictions with observation data. First evaluations have been made using data from the German TIRA radar system as well as data from the US Haystack radar and the ESA Space Debris Telescope. Although attesting a good conformance in general, the results indicate overestimation of some object families on one hand and a complete neglect of some other population fractions on the other. This paper evaluates modifications of the standard MASTER reference population e.g. by introduction of complementary populations, aiming for a better agreement of the MASTER model with the measurement results. The induced effects of the modifications on detection rates are iteratively analysed with PROOF and possibilities for a future improvement of the debris model are pointed out.

Wegener, Peter; Bendisch, Jörg; Krag, Holger

2001-10-01

135

Fitting population models from field data  

USGS Publications Warehouse

The application of population and community ecology to solving real-world problems requires population and community dynamics models that reflect the myriad patterns of interaction among organisms and between the biotic and physical environments. Appropriate models are not hard to construct, but the experimental manipulations needed to evaluate their defining coefficients are often both time consuming and costly, and sometimes environmentally destructive, as well. In this paper we present an empirical approach for finding the coefficients of broadly inclusive models without the need for environmental manipulation, demonstrate the approach with both an animal and a plant example, and suggest possible applications. Software has been developed, and is available from the senior author, with a manual describing both field and analytic procedures.

Emlen, J. M.; Freeman, D. C.; Kirchhoff, M. D.; Alados, C. L.; Escos, J.; Duda, J. J.

2003-01-01

136

Zooplankton Feeding on Differentially Labelled Algae and Bacteria  

Microsoft Academic Search

HERBIVOROUS zooplankton can graze on planktonic algae, bacteria and detrital particles1. Selective feeding of planktonic crustaceans on algae has been described and attributed to passive size selection by filtration or raptorial feeding1. The ingestion and utilisation of algae, bacteria and detritus by zooplankton has also been noted2-6 but as yet there have been few reports concerning the behaviour of zooplankton

Moshe Gophen; Ben Zion Cavari; Thomas Berman

1974-01-01

137

Quantitative Modeling of Growth and Dispersal in Population Models.  

National Technical Information Service (NTIS)

This document discusses techniques for the estimation of nonlinearities and state-dependent coefficients in parabolic partial differential equations. Applications to density-dependent population dispersal and nonlinear growth/predation models are presente...

H. T. Banks K. A. Murphy

1986-01-01

138

Multiple extinction routes in stochastic population models.  

PubMed

Isolated populations ultimately go extinct because of the intrinsic noise of elementary processes. In multipopulation systems extinction of a population may occur via more than one route. We investigate this generic situation in a simple predator-prey (or infected-susceptible) model. The predator and prey populations may coexist for a long time, but ultimately both go extinct. In the first extinction route the predators go extinct first, whereas the prey thrive for a long time and then also go extinct. In the second route the prey go extinct first, causing a rapid extinction of the predators. Assuming large subpopulation sizes in the coexistence state, we compare the probabilities of each of the two extinction routes and predict the most likely path of the subpopulations to extinction. We also suggest an effective three-state master equation for the probabilities to observe the coexistence state, the predator-free state, and the empty state. PMID:22463185

Gottesman, Omer; Meerson, Baruch

2012-02-24

139

Tidal exchange of zooplankton between Lough Hyne and the adjacent coast  

NASA Astrophysics Data System (ADS)

Plankton samples collected in November 2002, February, May and August 2003 were used to examine seasonal variation in tidal exchange of zooplankton biomass, abundance and species composition between Lough Hyne Marine Nature Reserve and the adjacent Atlantic coast. Micro- to mesozooplankton were collected by pump over 24-h sampling periods during spring and neap tides from the narrow channel connecting the semi-enclosed water body to the Atlantic. Sample biomass (dry weight) and total zooplankton abundance peaked in the summer and were lowest in winter, showing a positive relationship with temperature. Zooplankton biomass, total abundance and numbers of holo- and meroplankton revealed import during some diel cycles and export in others. However, the tidal import of these planktonic components was generally dominant, especially during May. The greatest import of numbers of holoplankters and meroplanktonic larvae occurred during May and August, respectively. There was no significant variation in sample biomass between periods of light and dark, but some variation in zooplankton abundance could be explained by this diel periodicity. Significant differences in sample assemblage composition between flood and ebb tide samples were always observed, except during winter neap tides. There was a net import of the copepods Temora longicornis and Oithona helgolandica and the larval stages of Mytilus edulis during spring and summer. Proceraea cornuta and Capitellid trochophores were imported during winter, and a hydrozoan of the genus Obelia during the spring spring tides. Seasonal export from the lough was shown by Pseudopolydora pulchra larvae (autumn and spring), Serpulid trochophores (autumn) and veligers of the bivalve Anomia ephippium (summer). It is suggested that the direction of tidal exchange of meroplanktonic taxa is related to the distribution of the adult populations. Copepod naupliar stages dominated the assemblages except during May spring tides when the copepod Pseudocalanus elongatus made up over 22% of the abundance. The general import of micro- to mesozooplankton may, in part, explain the higher densities of this size-class of zooplankton within the semi-enclosed system of Lough Hyne.

Rawlinson, K. A.; Davenport, J.; Barnes, D. K. A.

2005-01-01

140

A computational approach to modeling population differences.  

PubMed

Four experiments were conducted to determine whether the Hyperspace Analogue to Language (HAL) model of semantic memory could differentiate between two different populations. An analysis of the differences in densities (or average distances between word neighbors in semantic space) in HAL matrices--generated from text corpora derived from younger and older adults--confirmed that HAL was able to distinguish between the two age groups. This difference was again detected when structured interview data were used to build the corpora. A third experiment, designed to test the specificity of HAL in detecting differences between groups, did not detect any difference in the densities of the memory representations when older adults generated both the test corpora. The final experiment, conducted on the language of adults with Alzheimer's and normal adults, again demonstrated that HAL could discriminate between the two populations. These results suggest that HAL is capable of modeling, on the basis of changes in mean density, some of the differences between populations without modifying the model itself but, rather, by changing the text corpus from which the model creates its representations in semantic space. PMID:10875174

Conley, P; Burgess, C

2000-05-01

141

Inferences from Genomic Models in Stratified Populations  

PubMed Central

Unaccounted population stratification can lead to spurious associations in genome-wide association studies (GWAS) and in this context several methods have been proposed to deal with this problem. An alternative line of research uses whole-genome random regression (WGRR) models that fit all markers simultaneously. Important objectives in WGRR studies are to estimate the proportion of variance accounted for by the markers, the effect of individual markers, prediction of genetic values for complex traits, and prediction of genetic risk of diseases. Proposals to account for stratification in this context are unsatisfactory. Here we address this problem and describe a reparameterization of a WGRR model, based on an eigenvalue decomposition, for simultaneous inference of parameters and unobserved population structure. This allows estimation of genomic parameters with and without inclusion of marker-derived eigenvectors that account for stratification. The method is illustrated with grain yield in wheat typed for 1279 genetic markers, and with height, HDL cholesterol and systolic blood pressure from the British 1958 cohort study typed for 1 million SNP genotypes. Both sets of data show signs of population structure but with different consequences on inferences. The method is compared to an advocated approach consisting of including eigenvectors as fixed-effect covariates in a WGRR model. We show that this approach, used in the context of WGRR models, is ill posed and illustrate the advantages of the proposed model. In summary, our method permits a unified approach to the study of population structure and inference of parameters, is computationally efficient, and is easy to implement.

Janss, Luc; de los Campos, Gustavo; Sheehan, Nuala; Sorensen, Daniel

2012-01-01

142

Stellar population models at high spectral resolution  

NASA Astrophysics Data System (ADS)

We present new, high-to-intermediate spectral resolution stellar population models, based on four popular libraries of empirical stellar spectra, namely Pickles, ELODIE, STELIB and MILES. These new models are the same as our previous models, but with higher resolution and based on empirical stellar spectra, while keeping other ingredients the same including the stellar energetics, the atmospheric parameters and the treatment of the thermally pulsating asymptotic giant branch and the horizontal branch morphology. We further compute very high resolution (R= 20 000) models based on the theoretical stellar library MARCS which extends to the near-infrared. We therefore provide merged high-resolution stellar population models, extending from ˜1000 to 25 000 Å, using our previously published high-resolution theoretical models which extended to the ultraviolet. We compare how these libraries perform in stellar population models and highlight spectral regions where discrepancies are found. We confirm our previous findings that the flux around the V band is lower (in a normalized sense) in models based on empirical libraries than in those based on the BaSeL-Kurucz library, which results in a bluer B-V colour. Most noticeably the theoretical library MARCS gives results fully consistent with the empirical libraries. This same effect is also found in other models using MILES, namely Vazdekis et al. and Conroy & Gunn, even though the latter authors reach the opposite conclusion. The bluer predicted B-V colour (by 0.05 mag in our models) is in better agreement with both the colours of luminous red galaxies and globular cluster data. We test the models on their ability to reproduce, through full spectral fitting, the ages and metallicities of Galactic globular clusters as derived from colour-magnitude diagram (CMD) fitting and find overall good agreement. We also discuss extensively the Lick indices calculated directly on the integrated MILES-based spectral energy distributions (SEDs) and compare them with element ratio-sensitive index models. We find a good agreement between the two models, if the metallicity-dependent chemical pattern of the Milky Way stars is properly taken into account in this comparison. As a consequence, the ages and metallicities of Galactic globular clusters are not well reproduced when one uses straight the MILES-based indices, because subtle chemical effects on individual lines dominate the age derivation. The best agreement with the ages of the calibrating globular clusters is found with either element ratio-sensitive absorption-line models or the full SED fitting, for which no particular weight is given to selected lines.

Maraston, C.; Strömbäck, G.

2011-12-01

143

Toxicant-induced fecundity compensation: A model of population responses  

Microsoft Academic Search

A mathematical model widely applied in population studies and in assessment of the impact of exploitation on fish populations was applied to assess cadmium toxicity in laboratory populations ofDaphnia galeata mendotae. Over a range of toxicant concentrations, the birth rate of the population increased to balance the death rate and the population compensated for the increased mortality. The model describes

A. L. Jensen; J. S. Marshall

1983-01-01

144

Toxicant-induced fecundity compensation: A model of population responses  

Microsoft Academic Search

A mathematical model widely applied in population studies and in assessment of the impact of exploitation on fish populations was applied to assess cadmium toxicity in laboratory populations of Daphnia galeata mendotae. Over a range of toxicant concentrations, the birth rate of the population increased to balance the death rate and the population compensated for the increased mortality. The model

A. L. Jensen; J. S. Marshall

1983-01-01

145

Zooplankton species composition, abundance and biomass on the eastern Bering Sea shelf during summer: The potential role of water-column stability and nutrients in structuring the zooplankton community  

Microsoft Academic Search

The southeastern Bering Sea sustains one of the largest fisheries in the United States, as well as wildlife resources that support valuable tourist and subsistence economies. The fish and wildlife populations in turn are sustained by a food web linking primary producers to apex predators through the zooplankton community. Recent shifts in climate toward warmer conditions may threaten these resources

Kenneth O. Coyle; Alexei I. Pinchuk; Lisa B. Eisner; Jeffrey M. Napp

2008-01-01

146

Spatial Interaction Among Nontoxic Phytoplankton, Toxic Phytoplankton, and Zooplankton: Emergence in Space and Time  

Microsoft Academic Search

In homogeneous environments, by overturning the possibility of competitive exclusion among phytoplankton species, and by regulating\\u000a the dynamics of overall plankton population, toxin-producing phytoplankton (TPP) potentially help in maintaining plankton\\u000a diversity—a result shown recently. Here, I explore the competitive effects of TPP on phytoplankton and zooplankton species\\u000a undergoing spatial movements in the subsurface water. The spatial interactions among the species

Shovonlal Roy

2008-01-01

147

Are blue-green algae a suitable food for zooplankton? An overview  

Microsoft Academic Search

One of the reasons suggested to explain the dominance of blue-greens in eutrophic lakes is that they are not used as food\\u000a by zooplankton; and even when ingested, they are poorly utilized.\\u000a \\u000a An increase in herbivores might be the expected result of biomanipulation of the aquatic food chain. This attempt at controlling\\u000a the algae population is, however, destined to fail

R. de Bernardi; G. Giussani

1990-01-01

148

Interaction among Non-toxic Phytoplankton, Toxic Phytoplankton and Zooplankton: Inferences from Field Observations  

Microsoft Academic Search

We explore the mutual dependencies and interactions among different groups of species of the plankton population, based on\\u000a an analysis of the long-term field observations carried out by our group in the North–West coast of the Bay of Bengal. The\\u000a plankton community is structured into three groups of species, namely, non-toxic phytoplankton (NTP), toxic phytoplankton\\u000a (TPP) and zooplankton. To find

Shovonlal Roy; Sabyasachi Bhattacharya; Partha Das; Joydev Chattopadhyay

2007-01-01

149

Calibration of the NEMURO nutrient–phytoplankton–zooplankton food web model to a coastal ecosystem: Evaluation of an automated calibration approach  

Microsoft Academic Search

A one spatial-box version of the NEMURO oceanic lower trophic food web model was applied to a coastal upwelling environment typified by West Coast Vancouver Island. We used both ad hoc calibration and the automatic calibration program PEST. NEMURO was first calibrated to 1 year of monthly field data using the usual ad hoc approach of trial and error changes

Kenneth A. Rose; Bernard A. Megrey; Francisco E. Werner; Dan M. Ware

2007-01-01

150

Effects of piscivore-mediated habitat use on growth, diet and zooplankton consumption of roach: an individual-based modelling approach  

Microsoft Academic Search

SUMMARY 1. We used an individual based modelling approach for roach to (i) simulate observed diel habitat shifts between the pelagic and littoral zone of a mesotrophic lake; (ii) analyse the relevance of these habitat shifts for the diet, activity costs and growth of roach; and (iii) quantify the effects of a hypothetical piscivore-mediated (presence of pikeperch) confinement of roach

FRANZ H OLKER; S. H AERTEL; S ILKE S TEINER; T HOMAS M EHNER

151

Increasing zooplankton variance in the late 1990s unveils hydroclimate modifications in the Balearic Sea, Western Mediterranean.  

PubMed

We examined seasonal and interannual patterns of zooplankton functional groups in the Balearic Sea from 1994 to 2003 and revealed a conspicuous increase in zooplankton variance at community and population levels. The change occurred in 1999-2000, and paralleled modifications in the North Atlantic climate that cascaded down affecting the water column thermal gradient in the Balearic Sea. The observed modifications in both hydroclimate and ecological compartments raise the question of a potential ecological shift in the pelagic ecosystem of the Western Mediterranean in the late 1990s. PMID:23433612

Fernández de Puelles, Ma Luz; Molinero, Juan Carlos

2013-02-06

152

Response of zooplankton to the reduction and elimination of submerged vegetation by grass carp and herbicide in four Florida lakes  

Microsoft Academic Search

Zooplankton populations were monitored monthly for a three year period in four Florida lakes. Each lake received an aquatic vegetation control program using grass carp (Ctenopharyngodon idella Val.) and herbicide, either alone or in combination. All aquatic vegetation was eliminated in the three lakes with grass carp; it was severely reduced and exhibited qualitative shifts in the lake treated with

David I. Richard; James W. Small; John A. Osborne

1985-01-01

153

Fitting a predator prey model to zooplankton time-series data in the Gironde estuary (France): Ecological significance of the parameters  

NASA Astrophysics Data System (ADS)

The relationships between the seasonal fluctuations of the copepod Eurytemora affinis and the mysid Neomysis integer were studied from observed data and experimental results, using a predator prey model in the oligo-mesohaline area of the Gironde estuary. Mean seasonal fluctuations of abundances were derived from long term data series collected from 1978 to 2003 for both species. In situ predator prey experiments over a seasonal cycle were used to estimate the seasonal variation of the consumption rate of N. integer on E. affinis and to verify the order of magnitude of the biological parameters given by the model. Predator prey experiments revealed a high seasonal variation in maximum consumption rates with a mean of 56 ± 9 ind. pred-1 d-1. Maximum consumption rates were always higher for adults than for juveniles of Neomysis integer. Recorded selectivities were higher on nauplii than on copepodids + adults of Eurytemora affinis, both for the juveniles and the adults of N. integer. Neomysis integer mainly fed on meroplanktonic larvae, when they were available in higher abundances, than E. affinis in their environment. Spring increases of abundance for Eurytemora affinis copepodids + adults seemed to be mainly controlled by temperature whereas its decreasing abundance in summer was more related to Neomysis integer predation, suggesting that summer fluctuations of E. affinis abundance are probably controlled by mysid predation at summer times. Using a Lotka Volterra predator prey model, the seasonal peak of abundance of the mysid N. integer was well reproduced considering a predation on copepodids + adults of E. affinis, and suggested a dependence between mysid and copepod seasonal variations. However, the seasonal peak amplitude could not be explained solely by a predation on copepodids + adults or on nauplii of the copepod. Thus, N. integer is probably dependent on the seasonal fluctuations of the copepod's abundance, complementing its diet with macrophytal detritus during periods of scarce food.

David, Valérie; Chardy, Pierre; Sautour, Benoît

2006-05-01

154

Asymptotic Analysis of Structured Population Models  

NASA Astrophysics Data System (ADS)

Describing real world phenomena we produce models with ever increasing complexity. While very accurate, such models are very costly and cumbersome to analyse and often require data hard to obtain and tend to yield information which is redundant in specific applications. It is thus important to be able to derive simplified sub-models which still contain relevant information in a particular context but are more tractable. In biological applications this process is called `aggregation' of variables and is often based on separation of multiple time scales in the model. In this paper we describe how techniques of asymptotic analysis of singularly perturbed problems can be used to obtain in a systematic way a complete system of approximating equations and illustrate this approach on a example of a population equation of McKendrick type with age and space structure.

Banasiak, Jacek; Goswami, Amartya; Shindin, Sergey

2008-09-01

155

Manifold modeling for brain population analysis.  

PubMed

This paper describes a method for building efficient representations of large sets of brain images. Our hypothesis is that the space spanned by a set of brain images can be captured, to a close approximation, by a low-dimensional, nonlinear manifold. This paper presents a method to learn such a low-dimensional manifold from a given data set. The manifold model is generative-brain images can be constructed from a relatively small set of parameters, and new brain images can be projected onto the manifold. This allows to quantify the geometric accuracy of the manifold approximation in terms of projection distance. The manifold coordinates induce a Euclidean coordinate system on the population data that can be used to perform statistical analysis of the population. We evaluate the proposed method on the OASIS and ADNI brain databases of head MR images in two ways. First, the geometric fit of the method is qualitatively and quantitatively evaluated. Second, the ability of the brain manifold model to explain clinical measures is analyzed by linear regression in the manifold coordinate space. The regression models show that the manifold model is a statistically significant descriptor of clinical parameters. PMID:20579930

Gerber, Samuel; Tasdizen, Tolga; Thomas Fletcher, P; Joshi, Sarang; Whitaker, Ross

2010-06-04

156

COMPARISONS OF ZOOPLANKTON COMMUNITY SIZE STRUCTURE IN THE GREAT LAKES  

EPA Science Inventory

Zooplankton mean-size and size-spectra distribution potentially reflect the condition of trophic interactions and ecosystem health because they are affected by both resource availability and planktivore pressure. We assessed zooplankton mean-size and size-spectra using an optical...

157

Harvesting and Processing Zooplankton for Use as Supplemental Fry Feed  

Technology Transfer Automated Retrieval System (TEKTRAN)

We present the methods that we used to capture and dry large zooplankton from ponds to feed to channel catfish Ictalurus punctatus fry. Using a submersible pump and canister filter, we were able to capture about 1.0 kg (wet weight; 200 g in terms of dry weight) of zooplankton from well-fertilized po...

158

Evaluation of Zooplankton in Hatchery Diets for Channel Catfish Fry  

Technology Transfer Automated Retrieval System (TEKTRAN)

The efficacy of zooplankton as a supplemental hatchery diet for fry of channel catfish Ictalurus punctatus was evaluated. When a commercial diet is used as a reference, fry fed exclusively on zooplankton–either live or dried–performed poorly in their growth rate. However, when live or dried zooplan...

159

Thermal stress studies on selected zooplankton species and an isopod  

SciTech Connect

Laboratory determination of temperature stress levels and assessment of their ecological consequences was carried out for selected zooplankton species to develop data for ecological impact associated with industrial use of natural water for cooling. An included literature search revealed substantial fish and benthos data, but little on stress temperature effects on zooplankton. Information was gathered on two cladocerans, four copepods and an isopod.

Bunting, D.L.; Cheper, N.J.

1980-06-01

160

Empirical analysis of zooplankton filtering and feeding rates  

Microsoft Academic Search

Multiple regression analysis of published zooplankton filtering and feeding rates yielded separate regression equations for cladocerans, marine Calanoid copepods, and all zooplankton. Ingestion rate was found to increase significantly with animal size, food concentration, and temperature. Filtering rate also increased with animal size and temperature, but declined as food concentration increased. The analysis suggests a difference in particle size preference

ROBERT HENRY PETERS; JOHN A. DOWNING

1984-01-01

161

Limnetic crustacean zooplankton of Lake Oahe, May-October 1969  

USGS Publications Warehouse

The limnetic crustacean zooplankton of Lake Oahe was dominated by copepods. Cyclops bicuspidatus thomasi was the dominant crustacean throughout the lake. Mesocyclops edax, Diaptomus ashlandi and Daphnia pulex were major components of the zooplankton in the deep, downstream portion of the lake while Bosmina longirostris and Daphnia retrocurva were important constituents in the river-like, upstream section of the lake.

Selgeby, James H.

1974-01-01

162

Estimating the grazing impact of marine micro-zooplankton  

Microsoft Academic Search

This paper describes a dilution technique for estimating the micro-zooplankton grazing impact on natural communities of marine phytoplankton. Experiments performed in coastal waters off Washington, USA (October, 1980), yield estimates of micro-zooplankton impact equivalent to 6 to 24% of phytoplankton standing biomass and 17 to 52% of production per day. Indirect evidence suggests that most of this impact is due

M. R. Landry; R. P. Hassett

1982-01-01

163

Net-zooplankton biomass of the Adriatic Sea  

Microsoft Academic Search

On the basis of 1 107 plankton samples collected during 1971–1981 in the different parts of the Adriatic Sea, the horizontal distribution of net zooplankton biomass, expressed as dry weight and ash-free dry weight, is discussed. The northern Adriatic combined with the Gulf of Trieste usually had the highest standing crop of zooplankton. Biomass in other regions was lower and

A. Benovi?; S. Fonda-Umani; A. Malej; M. Specchi

1984-01-01

164

POPULATION BOTTLENECKS AND NONEQUILIBRIUM MODELS IN POPULATION GENETICS  

Microsoft Academic Search

ABSTRACT The amount,of variability in a population,that experiences,repeated,restric- tions in population,size has been,calculated. The,restrictions in size occur cyclically with a fixed cycle length. Analytical formulas,for describing,the gene identity at any specific time in the expanded and restricted phases of the cycle, and for the average and second moment of the gene identity, have been derived. It is shown,that the level

Paul A. Fuerstt

165

Functional bioassays utilizing zooplankton: A comparison  

SciTech Connect

Functional zooplankton bioassays based on ingestion, reproduction and respiration are described, with methods for a new ingestion bioassay included. All bioassays are compared using three indices, including the variability of controls, the range of experimental responses, and a listing of contaminants causing inhibition/stimulation of response. The ingestion bioassay showed the greatest range of response, and was sensitive to pesticides, PCBs and heavy metals. It was also commonly characterized by a hormesis response. The reproduction bioassay showed the lowest variability, illustrated a reduced range of response, and was sensitive to nutrients and heavy metals. In one study, the respiration bioassay was sensitive only to PCBs.

McNaught, D.C.

1989-01-01

166

Effects of a synthetic oil on zooplankton community structure  

SciTech Connect

This study assessed the effects of a coal-derived oil on the structure of zooplankton communities of laboratory pond microcosms and outdoor experimental ponds. Several measures of community structure and multivariate statistical techniques were used to reveal changes in the patterns of zooplankton community structure caused by the perturbation. From these results the basic ecological mechanisms responsible for maintenance of zooplankton community structure were inferred. The comparison of the field, laboratory microcosm, and laboratory bioassay results for the effects of oil provided an empirical basis for predicting pollutant effects on aquatic ecosystems. The responses of the microcosm and pond zooplankton communities to oil treatment were quite similar. Changes in cladoceran densities were the most sensitive indicators of stress in the zooplankton communities. Copepods were slightly less sensitive, and rotifers were least sensitive to oil treatment.

Hook, L.A.

1988-01-01

167

Estimating population trends with a linear model  

USGS Publications Warehouse

We describe a simple and robust method for estimating trends in population size. The method may be used with Breeding Bird Survey data, aerial surveys, point counts, or any other program of repeated surveys at permanent locations. Surveys need not be made at each location during each survey period. The method differs from most existing methods in being design based, rather than model based. The only assumptions are that the nominal sampling plan is followed and that sample size is large enough for use of the t-distribution. Simulations based on two bird data sets from natural populations showed that the point estimate produced by the linear model was essentially unbiased even when counts varied substantially and 25% of the complete data set was missing. The estimating-equation approach, often used to analyze Breeding Bird Survey data, performed similarly on one data set but had substantial bias on the second data set, in which counts were highly variable. The advantages of the linear model are its simplicity, flexibility, and that it is self-weighting. A user-friendly computer program to carry out the calculations is available from the senior author.

Bart, J.; Collins, B.; Morrison, R. I. G.

2003-01-01

168

Modeling denominator populations for mental health care.  

PubMed Central

Difficulties in using basic epidemiologic survey techniques in estimating the prevalence of disease in the community have led health services researchers to develop alternative methods using routinely collected health care data. The purpose of this paper is to illustrate the application of a model that estimates the prevalence of diagnosable mental disorder in a community, including the proportion of untreated cases. A mathematical model is developed based on a well-known probability distribution (the negative binomial) and simple calculation formulae are presented. This model has been used to estimate total practice population size. This paper extends that work by illustrating the utility of the model vis-a vis a specific type of disorder and shows pitfalls when caseness is not well established. An application of the model to data from two studies in an organized health care setting shows that the estimated period prevalence (one year) of mental disorder is between 17.4% and 21.8%. Of those individuals, it is estimated that 28.6% seek no health care during the year. The implications of these findings and the utility of the model are discussed.

Kessler, L

1983-01-01

169

Globally attracting fixed points in higher order discrete population models  

Microsoft Academic Search

We address the global stability properties of the positive equilibrium in a general delayed discrete population model. Our results are used to investigate in detail a well-known model for baleen whale populations.

Hassan A. El-Morshedy; Eduardo Liz

2006-01-01

170

Globally attracting fixed points in higher order discrete population models.  

PubMed

We address the global stability properties of the positive equilibrium in a general delayed discrete population model. Our results are used to investigate in detail a well-known model for baleen whale populations. PMID:16865365

El-Morshedy, Hassan A; Liz, Eduardo

2006-07-25

171

Biological processes in the water column of the South Atlantic Bight: Zooplankton responses: Progress report, June 1988--June 1989  

SciTech Connect

It is our objective to determine the major processes governing the abundance, composition and disruption of zooplankton as part of the interdisciplinary southeastern US continental shelf program of the Department of Energy. We will study the effects of physical processes such as along- and cross shelf advection and frontogenesis, on the development and fate of zooplankton populations during winter. Our proposed research consists of shipboard sampling, laboratory experiments and in situ determination of zooplankton abundance over time. The last objective represents a novel approach because the observations are (a) non-destructive with great spatial resolution, and (b) occur on current meter arrays at similar scales as measurements of current velocity and direction. Results to date show prolonged residence times of upwelled water masses on the middle and inner shelf during summer which results in the development of massive copepod and tunicate populations. During spring, the extent of displacement of nearshore zooplankton was a function of wind stress. Our results can be used to predict the impact of energy-related technology on the ecosystem of the southeastern continental shelf. 8 refs., 6 figs.

Paffenhoefer, G.A.

1989-02-07

172

Zooplankton and Micronekton Studies at Bermuda: An Historical Perspective.  

NASA Astrophysics Data System (ADS)

Studies of zooplankton and fishes around Bermuda have a fairly long history, with collections and descriptions dating back to the late 19th century, at least. This talk reviews the history of these studies at Bermuda, and looks for long-term generalizations about diversity, biomass and seasonality. The first organized sampling program was probably the Bermuda Oceanographic Expedition led by William Beebe in 1929-1931. Beebe worked on mesopelagic fishes and zooplankton for many years at Bermuda, making the first manned dives to the midwater zone in the Bathysphere. More systematic investigations began in 1940 with the work of Moore who used (fairly) consistent sampling methods and reported on the diversity and distribution of zooplankton around the island. Moore paid particular attention to vertical migrations and seasonal shifts in species dominance, but did not provide quantitative data in the modern sense. From the 1960's onward there were a series of programs to sample and quantify zooplankton around Bermuda, mainly in the upper water layers. Since 1994, the BATS program has made monthly zooplankton collections in the top 200 m that are analyzed for biomass and species composition. This sampling, combined with the various historical records of zooplankton occurrence, other sampling efforts at the Bermuda Biological Station, and physical and biogeochemical datasets of the BATS program, forms a valuable time-series of zooplankton dynamics, which should be continued as part of a Sargasso Observatory program.

Madin, L. P.; Steinberg, D. K.

2001-12-01

173

Characterization of Lake Michigan coastal lakes using zooplankton assemblages  

USGS Publications Warehouse

Zooplankton assemblages and water quality were examined bi-weekly from 17 April to 19 October 1998 in 11 northeastern Lake Michigan coastal lakes of similar origin but varied in trophic status and limnological condition. All lakes were within or adjacent to Sleeping Bear Dunes National Lakeshore, Michigan. Zooplankton (principally microcrustaceans and rotifers) from triplicate Wisconsin net (80 I?m) vertical tows taken at each lake's deepest location were analyzed. Oxygen-temperature-pH-specific conductivity profiles and surface water quality were concurrently measured. Bray-Curtis similarity analysis showed small variations among sample replicates but large temporal differences. The potential use of zooplankton communities for environmental lake comparisons was evaluated by means of BIOENV (Primer 5.1) and principal component analyses. Zooplankton analyzed at the lowest identified taxonomic level yielded greatest sensitivity to limnological variation. Taxonomic and ecological aggregations of zooplankton data performed comparably, but less well than the finest taxonomic analysis. Secchi depth, chlorophyll a, and sulfate concentrations combined to give the best correlation with patterns of variation in the zooplankton data set. Principal component analysis of these variables revealed trophic status as the most influential major limnological gradient among the study lakes. Overall, zooplankton abundance was an excellent indicator of variation in trophic status.

Whitman, Richard L.; Nevers, Meredith B.; Goodrich, Maria L.; Murphy, Paul C.; Davis, Bruce M.

2004-01-01

174

Dynamic analysis of a parasite population model  

NASA Astrophysics Data System (ADS)

We study the dynamics of a model that describes the competitive interaction between an invading species (a parasite) and its antibodies in an living being. This model was recently used to examine the dynamical competition between Tripanosoma cruzi and its antibodies during the acute phase of Chagas' disease. Depending on the antibody properties, the model yields three types of outcomes, corresponding, respectively, to healing, chronic disease, and host death. Here, we study the dynamics of the parasite-antibody interaction with the help of simulations, obtaining phase trajectories and phase diagrams for the system. We show that, under certain conditions, the size of the parasite inoculation can be crucial for the infection outcome and that a retardation in the stimulated production of an antibody species may result in the parasite gaining a definitive advantage. We also find a criterion for the relative sizes of the parameters that are required if parasite-generated decoys are indeed to help the invasion. Decoys may also induce a qualitatively different outcome: a limit cycle for the antibody-parasite population phase trajectories.

Sibona, G. J.; Condat, C. A.

2002-03-01

175

Effect of various intake designs on zooplankton entrainment  

SciTech Connect

Field studies were conducted at the intakes of three Tennessee Valley Authority electric power plants to determine whether intake design is a feasible means of mitigating effects on zooplankton by minimizing the quantity entrained. Three intake designs were evaluated: one with a shallow skimmer wall, one with a deep skimmer wall, and one with no skimmer wall. Several studies indicated possible differences between day and night in the quantity of zooplankton entrained. None of these studies indicated that the intake designs studied minimized the quantity of zooplankton entrained because the quantities in the intake canals were similar to the quantities in the source water body.

Dycus, D.L.

1983-03-01

176

Phytoplankton limitation by phosphorus and zooplankton grazing in an acidic Adirondack lake  

SciTech Connect

Lakes which are believed to have been acidified by atmospheric deposition of anthropogenic substances are known for their unusually high water clarity and low nutrient concentrations. Some evidence indicates that alterations in predator/prey relationships, an indirect effect of acidification, bring about the increase in water clarity. Enclosures were used to study the effects of phosphorus addition and zooplankton removal on the phytoplankton of an acidic lake in the Adirondack Mountains of New York. Fertilized enclosures had significantly lower alkalinities and contained significantly more dissolved oxygen after the incubation period than did unfertilized enclosures. The P concentration remained at or near the limit of detection in the unfertilized enclosures. The phytoplankton population bloomed after the addition of 80 micro g/liter of phosphate as KH/sub 2/PO/sub 4/. The response was measured by cell counts of the dominant phytoplankton. Chlamydomonas, and by changes in chlorophyll a concentration. About half the number of algal cells were present after the two week incubation when zooplankton were not removed, indicating that zooplankton herbivory can influence, but not totally control, the algal production. 46 references.

Singer, R.; Evans, G.L.; Pratt, N.C.

1984-08-01

177

Entrainment and advection in an island's tidal wake, as revealed by light attenuance, zooplankton, and ichthyoplankton  

Microsoft Academic Search

Spatial and temporal patterns of light attenuance, zooplankton abundance, and larval fish assemblages observed at night in the flood tide wake of a 2-km-wide, steep-sided island within the Great Barrier Reef lagoon (40-45-m local depth) are compared with two simple models. Eddy upwelling is shown to be slow relative to erosion, vertical entrainment, and advection (EA) arising near the flanks

Iain M. Suthers; C. T. Taggart; D. Kelley; D. Rissik; J. H. Middleton

2004-01-01

178

Dynamics of inhomogeneous populations and global demography models  

Microsoft Academic Search

The dynamic theory of inhomogeneous populations developed during the last decade predicts several essential new dynamic regimes applicable even to the well-known, simple population models. We show that, in an inhomogeneous population with a distributed reproduction coefficient, the entire initial distribution of the coefficient should be used to investigate real population dynamics. In the general case, neither the average rate

Georgy P. Karev

2005-01-01

179

Modeling the behavior of the northern anchovy, Engraulis mordax, as a schooling predator exploiting patchy prey  

NASA Astrophysics Data System (ADS)

Extensive data sets on the bioenergetics of the northern anchovy, Engraulis mordax, and the patchy food distribution in its natural habitat allow its foraging dynamics to be inferred by modeling using techniques from population biology and behavioral ecology. The behavioral model consistently predicts that E. mordax grows much more slowly than would be expected with a pure, net-energy intake rate maximization strategy. The reduced growth rates could result from the fish avoiding zooplankton patches, where they are under increased predation risk, by swimming slowly in the waters between zooplankton patches. The combinations of growth rates and daily instantaneous mortality rates generated by the behavioral model are internally consistent with a Lefkovitch matrix population model, which includes an early juvenile stage of a stable and stationary population. Several novel and testable predictions are made by the behavioral model, including: (1) anchovies swim very slowly between zooplankton patch encounters; (2) within a patch fish swim very rapidly while searching for prey; and (3) fish often leave zooplankton patches before totally filling their stomachs. Given these encouraging initial results, the behavioral modeling approach appears to be a valuable technique for examining how potential habitat changes due to global warming may affect fish behavior and populations. Several such scenarios are proposed and discussed.

Nonacs, Peter; Smith, Paul E.; Bouskila, Amos; Luttbeg, Barney

180

A new piezoelectric response model for population growth of bacteria  

Microsoft Academic Search

A piezoelectric response model on the population growth of microorganism is proposed. This model is based on a novel population growth model, which has a more obvious ecological meaning and the fact that the series piezoelectric quartz crystal (SPQC) sensor responses to conductivity changes of the medium during the growth of the microorganism. From the response model four parameters can

Lili Bao; Huwei Tan; Le Deng; Wanzhi Wei

1998-01-01

181

Population viability analysis for Hector's dolphin (Cephalorhynchus hectori): A stochastic population model for local populations  

Microsoft Academic Search

Mortality of Hector's dolphin (Cephalorhynchus hectori) in gill?net fisheries is a threat to local populations throughout its range. This population viability analysis extends previous work by exploring a wider range of fishing levels and population growth rates, by incorporating year?to?year and environmental variability and by reporting results for smaller population units. Ten of the 16 populations are likely to continue

Stephanie M. Burkhart; Elisabeth Slooten

2003-01-01

182

A mathematical model for resource allocation in population programs  

Microsoft Academic Search

The reduction of population growth rates through family planning programs is being attempted in many of the developing nations\\u000a of the world. This activity lends itself aptly to mathematical modeling. Building from the well-known difference equation\\u000a model of population growth, a model is constructed which integrates population dynamics, program activities, and resource\\u000a consumption. The model may be used predictively to

Charles E. Lawrence; Axel I. Mundigo; Charles S. ReVelle

1972-01-01

183

Influence on phytoplankton biomass in lakes of different trophy by phosphorus in lake water and its regeneration by zooplankton  

Microsoft Academic Search

In 49 unpolluted lakes of north-eastern Poland the biomass of algae in summer is significantly related to the concentration of total phosphorus and to the rate of phosphorus regeneration by zooplankton. Using a model with equations describing these relationships, the biomass of blue-green algae and other phytoplankton groups was predicted for 14 polluted lakes. A good approximation of actual values

Jolanta Ejsmont-Karabin; Irena Spodniewska

1990-01-01

184

Discriminating zooplankton assemblages in neritic and oceanic waters: a case for the northeast coast of India, Bay of Bengal.  

PubMed

Zooplankton species distribution and abundance data at 17 locations in the inshore (10-30 m), shelf (50-200 m) and oceanic (2,500-2,800 m) regions off northeast India (Bay of Bengal) during January 1999-April 2001 revealed 112 taxa represented by 30 divergent groups. Copepods (58 species) dominated (87%) the population numerically. In general zooplankton diversity (Margalef richness d, Shannon-Wiener H', Pielou's evenness J') increased in the direction of the open sea relative to coastal locations with a concomitant decrease both in abundance (ind m(-3)) and biomass (dry mass m(-3)). Based on multivariate analyses, it was possible to distinguish the zooplankton community into different assemblages according to their location (e.g., inshore, shelf, oceanic) and seasonality. While Acrocalanus sp., Oithona sp., Corycaeus danae, Euterpina acutifrons, Paracalanus sp., and Acartia sp. were found characterizing the coastal locations, Oncaea venusta was the discriminating species for shelf waters. In oceanic areas, there was a clear dominance of Labidocera sp., Candacia sp., Euchaeta rimana, Centropages calaninus, Copilia mirabilis and Corycella gibbula. The investigations revealed that changes in zooplankton community structure across water bodies could be associated with differing salinity. During November 1999 (post-monsoon), when salinity in the coastal waters was relatively low (26-28.9 PSU), the zooplankton community consisted of mainly Acrocalanus sp., Salpa, Corycaeus danae, Oikopleura sp., Acartia sp., Evadne tergestina, and Creseis sp. In January 2000 (salinity 32.4-34.1), additionally Corycella gibbula, Labidocera sp., Centropages sp., Microsetella sp., Euterpina acutifrons, Canthocalanus pauper, and Oncaea venusta represented the population discriminating the assemblage from others. In May 2000 (pre-monsoon) when salinity was highest (34.7-35.3), Oithona sp., Paracalanus sp., and Acrocalanus gibber were found important. Chaetognaths formed a distinct group during this period. Results presented during this investigation are considered significant since no previous studies exist for this locale drawing comparisons of the kind made during this study between coastal and oceanic situations. PMID:16125769

Rakhesh, M; Raman, A V; Sudarsan, D

2005-08-25

185

GUIDELINES FOR ZOOPLANKTON SAMPLING IN QUANTITATIVE BASELINE AND MONITORING PROGRAMS  

EPA Science Inventory

Methods applicable to zooplankton sampling and analysis in quantitative baseline and monitoring surveys are evaluated and summarized. Specific recommendations by managers must take into account characteristics of the water mass under investigation, the abundance of contained zoop...

186

Studies on abundance of zooplanktons in lakes of Mysore, India.  

PubMed

This is the first comprehensive ecological study on the abundance of zooplankton in Kalale, Alanahalli and Dalvoy lakes of Mysore. The abundance of zooplankton as well as their relation with physico-chemical parameters was analyzed, every month in these lakes from June 2008-May 2010. The mean abundance of Rotifer (281 Org (l-1)), Cladocerans (27 Org l(-1)) and total abundance of zooplankton (343 Org l(-1)) were more and significantly different in Dalvoy lake; whereas, in Kalale lake the mean abundance of Rotifer (19 Org l(-1)), Cladocerans (3 Org l(-1)) and total abundance of zooplankton (79 Org l(-1)) and in Alanahalli lake the mean abundance of Rotifer (84 Org l(-1)), Cladocerans (9 Org l(-1)) and total abundance of zooplankton (149 Org l(-1)) were significantly less. However, the abundance of Copepods and Ostracods was similar in all the three lakes studied. The water bodies of Kalale lake were less polluted when compared toAlanahalli and Dalvoy lakes. The increases in conductivity, Chl a, turbidity, phosphate, carbon-di-oxide and total anions in Alanahalli and Dalvoy lakes may be attributed to the various anthropogenic activities in the catchment areas. Interrelationships between zooplankton variables and physico-chemical parameters were calculated using Pearson's correlation co-efficient (r) which revealed (25) significant (P < 0.05) relationships (More (11) in Dalvoy lake and moderate (7) in Alanahalli and Kalale lakes). The stepwise multiple regression analysis (r2) showed out of 21 physico-chemical parameters studied, as many as 12 were positively controlling the abundance of zooplankton, where as the phosphate and chloride were negatively controlling the total abundance of zooplankton and the abundance of ostracods respectively. The results obtained have been discussed in the light of the present literature available in the field of aquatic microbial ecology. PMID:23741805

Savitha, N; Yamakanamardi, Sadanand M

2012-11-01

187

Zooplankton data report: the Marginal Ice Zone Experiment MIZEX, 1984  

SciTech Connect

The Marginal Ice Zone Experiment (MIZEX 84) concentrated on atmospheric, oceanic, and ice interactions in the Fram Strait region of the Greenland Sea, specifically the effect of the retreating ice margin on the productivity in the area and the use of zooplanktonic species as indicators of Arctic and North Atlantic water masses. The data in this report are the quantitative analyses of zooplankton collected while aboard the research vessel Polarstern.

Smith, S.L.; Lane, P.V.Z.; Schwarting, E.M.

1986-03-01

188

Role of parthenogenetic natality and emergence from diapausing eggs in the dynamics of some rotifer populations  

Microsoft Academic Search

There are few quantitative data on the role of emergence from diapausing eggs in population dynamics of natural populations of zooplankton species; to our knowledge, all these concern copepods and ‘cladocerans’. We present here direct estimates of emergence from bottom resting eggs for another important category of freshwater zooplankton, namely rotifers. Three populations of rotifers of the genus Brachionus were

Elena A. Mnatsakanova; Leonard V. Polishchuk

1996-01-01

189

Maximum likelihood estimation of population divergence times and population phylogenies under the infinite sites model.  

PubMed

In this paper, a maximum likelihood estimator of population divergence time based on the infinite sites model is developed. It is demonstrated how this estimator may be applied to obtain maximum likelihood estimates of the topology of population phylogenies. This approach addresses several classical problems occurring in the inference of the phylogenetic relationship of populations, most notably the problem of shared ancestral polymorphisms. The method is applied to previously published data sets of human African populations and of Caribbean hawksbill turtles. PMID:9615473

Nielsen, R

1998-04-01

190

Time series sampling and data assimilation in a simple marine ecosystem model  

Microsoft Academic Search

Simulated distributions of nutrients, phytoplankton and zooplankton were obtained from a simple marine ecosystem model that included nutrient inputs from episodic events. These distributions were then used in numerical identical twin experiments to test the ability of an adjoint data assimilation method to recover rate parameters, such as population growth and death rates, component initial conditions, and the amplitude of

Linda M. Lawson; Eileen E. Hofmann; Yvette H. Spitz

1996-01-01

191

COMBINED METABOLIC AND CELL POPULATION MODELING FOR YEAST BIOREACTOR CONTROL  

Microsoft Academic Search

Several investigators recently have explored the use of cell population balance equation (PBE) models for the design of biochemical reactor control strategies. A major disadvantage of the PBE modeling approach is that the incorporation of intracellular reactions needed to accurately describe cellular pro- cesses leads to substantial computational diculties. We investigate an alternative modeling technique in which the cell population

Michael A. Henson; Dirk Muller; Matthias Reuss

192

Population dynamics of infectious diseases: A discrete time model  

Microsoft Academic Search

Mathematical models of infectious diseases can provide important insight into our understanding of epidemiological processes, the course of infection within a host, the transmission dynamics in a host population, and formulation or implementation of infection control programs. We present a framework for modeling the dynamics of infectious diseases in discrete time, based on the theory of matrix population models. The

Madan K. Oli; Meenakshi Venkataraman; Paul A. Klein; Lori D. Wendland; Mary B. Brown

2006-01-01

193

AN INDIVIDUAL-BASED MODEL OF COTTUS POPULATION DYNAMICS  

EPA Science Inventory

We explored population dynamics of a southern Appalachian population of Cottus bairdi using a spatially-explicit, individual-based model. The model follows daily growth, mortality, and spawning of individuals as a function of flow and temperature. We modeled movement of juveniles...

194

World population growth—a general model  

Microsoft Academic Search

National populations currently fall into two categories, those in or closely approaching a stationary “K” phase, those still in an “r” phase of exponential growth. Throughout human history the “K” phase, in which populations match their available resource bases, has generally predominated. The exploitive “r” phase has intermittently occurred, and has then normally featured some revolutionary improvement in extractive capacity,

A. S. Boughey

1974-01-01

195

Stable isotope analysis of 1987-1991 zooplankton samples and bowhead whale tissues. Final report  

SciTech Connect

Stable isotope analyses of bowhead whale tissue samples and bowhead whale prey organisms collected over the years 1987 to 1991 were used to provide detail on the isotope ratio gradients evident in the arctic Alaskan zooplankton and to verify previous findings regarding the growth rates and age determination techniques developed for bowhead whales. Zooplankton of the Bering and Chukchi seas are enriched in (13)C relative to the eastern Beaufort Sea. The analysis of baleen from bowhead whales taken between 1987 to 1990 indicate that the whales are slow-growing and the young animals between year one and about six to seven years of age, undergo a period of little or no linear growth. The authors estimate that bowheads require 16-18 years to reach the length of sexual maturity, i.e., 13-14 m. From baleen Delta(13C) cycles, a 20 year record of the isotope ratios in the phytoplankton of the northern Bering and Chukchi seas was constructed. The long-term record has been compared with the temperature anomalies in surface waters of the Bering Sea. The Delta(13C) of the zooplankton is inversely correlated with temperature and refutes current models attempting to relate ocean temperature, and atmospheric carbon dioxide levels with the Delta(13C) of ocean sediment organic matter.

Schell, D.M.

1992-06-01

196

World population projections using metabolic GM (1,1) model  

Microsoft Academic Search

Forecasts of population size allow city planners, economists, public agencies, environmentalists, and social scientists to prepare for what is to come, so the research on population projections has become a focus of demographers' research. In the study, population system is regarded as a grey system and a method based on GM (1,1) model from Grey system theory is introduced to

Caimei Lu; Yonghong Hao; Xuemeng Wang

2007-01-01

197

Dynamic models of infectious diseases as regulators of population sizes  

Microsoft Academic Search

Five SIRS epidemiological models for populations of varying size are considered. The incidences of infection are given by mass action terms involving the number of infectives and either the number of susceptibles or the fraction of the population which is susceptible. When the population dynamics are immigration and deaths, thresholds are found which determine whether the disease dies out or

Jaime Mena-Lorcat; Herbert W. Hethcote

1992-01-01

198

A simple mathematical model of rodent population cycles  

Microsoft Academic Search

A simple mathematical rate equation model is presented, which describes the observed cycles in rodent populations. The population is assumed to consist of two different genotypes. One type is called “emigrants”, having a high reproductive rate and reacting on the stress due to dense populations by dispersal. The other type may be referred to as “tolerants”, being insensitive to overpopulation

H. Dekker

1975-01-01

199

SMALL POPULATIONS REQUIRE SPECIFIC MODELING APPROACHES FOR ASSESSING RISK  

EPA Science Inventory

All populations face non-zero risks of extinction. However, the risks for small populations, and therefore the modeling approaches necessary to predict them, are different from those of large populations. These differences are currently hindering assessment of risk to small pop...

200

L-Lake zooplankton: L-Lake/Steel Creek Biological Monitoring Program, November 1985--December 1991  

SciTech Connect

The L- Lake Biological Monitoring Program was designed to meet environmental regulatory requirements associated with the restart of L-Reactor and address portions of Section 316(a) of the Clean Water Act, which requires an applicant for a discharge permit to provide scientific evidence that the discharge causes no significant impact on the indigenous ecosystem. The Department of Energy (DOE) must demonstrate that the discharge of L-Reactor affluent into L Lake will not inhibit the eventual establishment of a ``Balanced Biological Community`` (BBC) in at least 50% of the lake. This report details results of monitoring zooplankton populations in L-Lake.

Bowers, J.A. [Westinghouse Savannah River Co., Aiken, SC (United States); Bowen, M. [Normandeau Associates, Inc., New Ellenton, SC (United States)

1992-03-01

201

Population model for Alaska Peninsula sea otters. Final report  

SciTech Connect

This study was conducted to provide a basis for assessing risks of oil spills to sea otter populations along the Alaska Peninsula. The principal efforts were devoted to analyzing the available data on population dynamics. Curves characterizing survivorship and reproduction for sea otters were devised and fitted to several data sets. A detailed review was conducted of methods of assessing population dynamics data, and several new techniques (e.g., bootstrapping) were applied to available data. A simplified model for use with Alaska Peninsula sea otter populations was devised and implemented in a 'spreadsheet' format. Various aspects of model development and data on population size in Alaska Peninsula areas were reviewed.

Eberhardt, L.L.; Siniff, D.B.

1988-12-31

202

Analysis of six groups of zooplankton in samples taken in 1978/79 at the proposed OTEC site in the eastern Gulf of Mexico off Tampa Bay  

SciTech Connect

Continued analysis has been made of the 33 zooplankton collections made at the proposed OTEC site in the Gulf of Mexico off Tampa Bay. Six groups of zooplankton - siphonophores (Calycophora), pteropods (Thecosomata), chaetognaths, thaliaceans, euphausiids and amphipods were quantitatively investigated. Numbers and biomass were determined for all taxa and diurnal, seasonal and depth trends were discussed. Considering the present study and the previous investigation of the copepod population, this proposed OTEC site is probably one of the faunistically better known locales in the Gulf of Mexico and Caribbean.

Flock, M.E.; Hopkins, T.L.

1981-05-01

203

Generalized modeling of ecological population dynamics  

Microsoft Academic Search

Over the past years several authors have used the approach of generalized modeling to study the dynamics of food chains and food webs. Generalized models come close to the efficiency of random matrix models, while being as directly interpretable as conventional differential-equation-based models. Here we present a pedagogical introduction to the approach of generalized modeling. This introduction places more emphasis

Justin D. Yeakel; Dirk Stiefs; Mark Novak; Thilo Gross

2010-01-01

204

PC BEEPOP, an Ecotoxicological Simulation Model for Honey Bee Populations.  

National Technical Information Service (NTIS)

PC BEEPOP is a computer model that simulates honey bee (Apis mellifera L.) colony population dynamics. The model consists of a feedback system of interdependent elements, including colony condition (e.g., initial size, reproductive potential of the queen ...

J. J. Bromenshenk J. Doskocil G. J. Olbu G. DeGrandi-Hoffman S. A. Roth

1991-01-01

205

PC BEEPOP - AN ECTOXICOLOGICAL SIMULATION MODEL FOR HONEY BEE POPULATIONS  

EPA Science Inventory

PC BEEPOP is a computer model that simulates honey bee colony population dynamics. he model consists of a feedback system of interdependent elements, including colony condition, environmental variability, and contaminant exposures. t includes a mortality module (BEEKILL) and a ch...

206

A model for line transect sampling clustered populations  

Microsoft Academic Search

A model is presented for the estimation of population density using line-transect methods on clustered individuals. The model assumes independent sighting of clusters but does not require all individuals in a cluster to be sighted.

P. V. Rao; K. M. Portier

1985-01-01

207

PC BEEPOP - A PERSONAL COMPUTER HONEY BEE POPULATION DYNAMICS MODEL  

EPA Science Inventory

PC BEEPOP is a computer model that simulates honey bee (Apis mellifera L.) colony population dynamics. he model consists of a system of interdependent elements, including colony condition, environmental variability, colony energetics, and contaminant exposure. t includes a mortal...

208

Response of zooplankton to improving water quality in the Scheldt estuary (Belgium)  

NASA Astrophysics Data System (ADS)

Data obtained from 14 years of monthly samplings (1996-2009) were used to investigate the response of the crustacean zooplankton community to improving water quality in the Scheldt estuary. A strong reduction of poor water quality indicators, such as NH 4+ and BOD 5, as well as an increase in oxygen and in chlorophyll a concentrations were observed during the study period. During the study period, important changes were observed in the zooplankton community composition and spatial distribution. From 2007 onwards, most of the calanoid population, previously mainly found in the brackish water reach of the estuary, moved to the freshwater, where they reached higher abundances than previously observed. Simultaneously, cyclopoids populations strongly decreased in freshwater while cladocerans did not change their abundance, except during years with high chlorophyll a concentrations. Redundancy analyses (RDA) showed that the variability within the calanoid population can be explained by the improvement in water quality. Variability within the cyclopoids and cladoceran community is mainly explained by chlorinity and chlorophyll a concentrations. Their presence in the most polluted upstream area until 2007 suggests they are more tolerant to poor water quality than calanoids. Several hypotheses to explain the disappearance of cyclopoids after the move of calanoids to the freshwater are presented and discussed.

Mialet, B.; Gouzou, J.; Azémar, F.; Maris, T.; Sossou, C.; Toumi, N.; Van Damme, S.; Meire, P.; Tackx, M.

2011-05-01

209

Influence of spatial heterogeneity on the type of zooplankton functional response: A study based on field observations  

NASA Astrophysics Data System (ADS)

Mathematical models of plankton dynamics are sensitive to the choice of type of zooplankton functional response, i.e., to how the rate of intake of food varies with the food density. Conventionally, the conclusion on the actual type of functional response for a given zooplankton species is made based upon laboratory analysis on experimental feeding. In this paper, we show that such an approach can be too simplistic and misleading. Based on real ocean data obtained from three expeditions of R/V Jan Mayen in the Barents Sea in 2003-2005, we demonstrate that vertical heterogeneity in algal distribution as well as active vertical movement of herbivorous zooplankton can modify the type of trophic response completely. In particular, we found that the rate of average intake of algae by Calanus glacialis exhibits a Holling type III response, instead of Holling type I or II found previously in laboratory experiments. We argue that this conceptual discrepancy is due to the ability of the zooplankton to feed in layers with high algal density and to avoid depths with lower algal density. Since theoretical studies would predict enhancing in system stability in the case of Holling type III, our results may be of importance for understanding the main factors controlling plankton dynamics.

Morozov, Andrew; Arashkevich, Elena; Reigstad, Marit; Falk-Petersen, Stig

2008-10-01

210

Population-Based Continuous Optimization, Probabilistic Modelling and Mean Shift  

Microsoft Academic Search

Evolutionary algorithms perform optimization using a population of sample solution points. An interesting development has been to view population-based optimization as the process of evolving an explicit, probabilistic model of the search space. This pa- per investigates a formal basis for continuous, population-based optimization in terms of a stochastic gradient descent on the Kullback-Leibler divergence between the model probability density

Marcus Gallagher; Marcus R. Frean

2005-01-01

211

Interpolation solution in generalized stochastic exponential population growth model  

Microsoft Academic Search

In this paper, first we consider model of exponential population growth, then we assume that the growth rate at time t is not completely definite and it depends on some random environment effects. For this case the stochastic exponential population growth model is introduced. Also we assume that the growth rate at time t depends on many different random environment

M. Khodabin; K. Maleknejad; M. Rostami; M. Nouri

212

Population balance model for mixing in continuous flow systems  

Microsoft Academic Search

A population balance model is developed for describing macromixing–micromixing hierarchy of continuous flow systems based on the concept of interactive populations of fluid elements. Macromixing is represented as motion of fluid elements in the physical space described by convection–dispersion models while micromixing is described as motion in the composition space induced by randomised mass exchange interactions of fluid elements. A

Béla G. Lakatos

2008-01-01

213

ZOOPLANKTON POPULATION DYNAMICS IN EXPERIMENTALLY TOXIFIED POND ECOSYSTEMS  

EPA Science Inventory

The response of aquatic systems to toxic contaminants cannot easily be predicted from laboratory bioassays. In ecosystems, contamination can occur in the concert of natural system processes and could have more or less dramatic effects, depending upon conditions such as system sta...

214

Population dynamics of pond zooplankton II Daphnia ambigua Scourfield  

USGS Publications Warehouse

Calcium was the most important of 27 environmental components affecting density for a 50 week period. Simultaneous stepwise regression accounted for more variability in total number/1 and in the number of ovigerous females/1 than did any of the lag analyses; 1-week lag accounted for the greatest amount of variability in clutch size. Total number and clutch size were little affected by measures of food. ?? 1973 Dr. W. Junk b.v. Publishers.

Angino, E. E.; Armitage, K. B.; Saxena, B.

1973-01-01

215

Changes in fatty acid and hydrocarbon composition of zooplankton assemblages related to environmental conditions  

SciTech Connect

Changes in zooplankton fatty acid and hydrocarbon patterns are described in relation to changes in environmental conditions and species composition. The regulation of zooplankton abundance by sea nettle-ctenophore interaction was examined in a small Rhode Island coastal pond. Sea nettles were nettles were able to eliminate ctenophores from the pond and subsequently zooplankton abundance increased. During one increase in zooplankton abundance, it was found that polyunsaturated fatty acids decreased while monounsaturated fatty acids increased. It was concluded that this shift in biochemical pattern was due to food limitation. In addition, zooplankton fatty acids were used in multivariate discriminant analysis to classify whether zooplankton were from coastal or estuarine environments. Zooplankton from coastal environments were characterized by higher monounsaturate fatty acids. Zooplankton hydrocarbon composition was affected by species composition and by pollution inputs. The presence of Calanus finmarchicus was detected by increased levels of pristane.

Lambert, R.M.

1989-01-01

216

Seasonal and Spatial Distribution of Zooplankton in a Flood Control Reservoir and Tailwater.  

National Technical Information Service (NTIS)

Zooplankton, when available, may be an important food source for fish fry in lotic habitats. The effects of flood control reservior operation on the downstream transport of reservior zooplankton (both microcrustaceans and rotifers) were quantified by exam...

J. R. Novotny R. D. Hoyt

1983-01-01

217

Nitrogen isotopic ratios in fecal pellets produced by marine zooplankton  

SciTech Connect

At each site and in every season studied, zooplankton in the upper ocean produced fecal pellets that were 1.3% lower in {delta}{sup 15}N than their body tissue but 2.2% higher than their apparent food source. {sup 14}N-containing molecules are evidently preferentially assimilated in zooplankton intestinal tracts, though other isotopic effects must account for the enrichment in {sup 15}N of these organisms relative to their food. These results also show zooplankton to be important modifiers of nitrogen isotopic ratios for marine particulate matter. {delta}{sup 15}N values for sinking particles and fecal pellets are similar, supporting the perspective that macrozooplankton are important factors in producing and processing particles that sink into the ocean's interior and sediments. In contrast, the relationship in {delta}{sup 15}N between fecal pellets and suspended particles in the euphotic zone is more variable. It appears that zooplankton select food particles of varying {delta}{sup 15}N from the suspended particle pool. These results suggest that both zooplankton feeding behavior and their digestive chemistry are important in determining the composition of sinking particulate matter in the ocean with respect to the suspended particle source in the euphotic zone.

Altabet, M.A. (Woods Hole Oceanographic Institution, MA (USA)); Small, L.F. (Oregon State Univ., Corvallis (USA))

1990-01-01

218

Zooplankton communities of a new pumped storage reservoir  

SciTech Connect

Zooplankton colonization was followed for 16 months in Lake Oconee, Georgia, a new pumped storage reservoir. Data were interpreted to identify differences among stations and seasons, as a function of the reservoir's early stage of development and of pumped storage operations. Colonization was rapid, and the zooplankton community was characterized by a high species diversity; approximately 40 rotifer species and 14 cladoceran genera were recorded. Zooplankton density varied along an environmental gradient from riverine to lentic conditions. Rotifer abundance varied from 10/sup 4/-10/sup 6/ individuals/m/sup 3/, with maxima in the summers. Copepod and cladoceran densities ranged from 10/sup 3/ to nearly 10/sup 5/ individuals/m/sup 3/; maxima for stations other than the dam were observed in the summer and early fall, but high values at the dam station occurred throughout winter 1980. When pumped storage operations began in December 1979, zooplankton densities increased at the dam station. Pumpback decreased the intensity of the environmental gradient from riverine to lentic conditions, and led to a more similar zooplankton community structure throughout the reservoir.

Potter, D.U. (Water Quality Control Bureau, Santa Fe, NM); Meyer, J.L.

1982-08-01

219

Generalized modeling of ecological population dynamics  

Microsoft Academic Search

Over the past 7 years, several authors have used the approach of generalized modeling to study the dynamics of food chains\\u000a and food webs. Generalized models come close to the efficiency of random matrix models, while being as directly interpretable\\u000a as conventional differential-equation-based models. Here, we present a pedagogical introduction to the approach of generalized\\u000a modeling. This introduction places more emphasis

Justin D. Yeakel; Dirk Stiefs; Mark Novak; Thilo Gross

2011-01-01

220

Modeling and prediction of cell population dynamics  

Microsoft Academic Search

Oscillatory yeast cell dynamics are observed in glucose-limited growth environments. Under such conditions, both glucose and the excreted product ethanol can serve as substrates for cell growth. The cell dynamics is described by a PDE (partial differential equation) system containing one PDE for the cell population and 8 ODEs for 8 substrates variations (extracellular glucose, extracellular ethanol, intracellular glucose, intracellular

Youngil Lima

221

Modeling and prediction of cell population dynamics  

Microsoft Academic Search

Oscillatory yeast cell dynamics are observed in glucose-limited growth environments. Under such conditions, both glucose and the excreted product ethanol can serve as substrates for cell growth. The cell dynamics is described by a PDE (partial differential equation) system containing one PDE for the cell population and 8 ODEs for 8 substrates variations (extracellular glucose, extracellular ethanol, intracellular glucose, intracellular

Youngil Lim

2005-01-01

222

Isolation by distance in a continuous population: reconciliation between spatial autocorrelation analysis and population genetics models  

Microsoft Academic Search

Analysis of the spatial genetic structure within continuous populations in their natural habitat can reveal acting evolutionary processes. Spatial autocorrelation statistics are often used for this purpose, but their relationships with population genetics models have not been thoroughly established. Moreover, it has been argued that the dependency of these statistics on variation in mutation rates among loci strongly limits their

OLIVIER J. HARDY; XAVIER VEKEMANS

1999-01-01

223

Two stressors and a community: effects of hydrological disturbance and a toxicant on freshwater zooplankton.  

PubMed

Climate change models predict an increase in the frequency and intensity of extreme fluctuations in water level in aquatic habitats. Therefore, it is necessary to understand the combined effects of hydrological fluctuations and toxicants on aquatic biological communities. We investigated the individual and combined effects of the insecticide esfenvalerate and recurring fluctuations in water level on zooplankton communities in a system of 55 outdoor pond microcosms. The communities were exposed to esfenvalerate contamination as a single pulse (at 0.03, 0.3, or 3?g/L) and gradual removal of water and its subsequent replacement over three cycles and monitored until 84 days after contamination. The results showed that the sensitivities of the community and its constituent populations to the toxicant were increased by the hydrological stress. Specifically, for both the community structure and abundance of Daphnia spp. the lowest-observed-effect concentrations (LOEC) were 0.03 and 0.3?g/L for the series with fluctuating and constant water levels, respectively. Despite these differences in sensitivity, the interactive effects of the two stressors were found to be additive for both the community structure and the abundance of the most affected species. Presumably, it was not possible to detect synergism due to the strong individual effects of the water level fluctuations. Recovery times in the series exposed to the highest pesticide concentration were 64 and 55 days under fluctuating and constant water level regimes, respectively. Competition and water quality are suggested to be the major factors that underlie the observed effects of fluctuations in the water level. For the ecological risk assessment of toxicants, the present results suggest that (i) community sensitivity may vary substantially, depending on the environmental context, and (ii) this variability can be assessed experimentally to derive safety factors (coefficients used to avoid unexpected effects and define safe concentrations of toxicants) based on empirical findings. This contrasts with the current approach where such factors are usually defined arbitrarily. PMID:23063066

Stampfli, Nathalie C; Knillmann, Saskia; Liess, Matthias; Noskov, Yury A; Schäfer, Ralf B; Beketov, Mikhail A

2012-09-13

224

A quantitative model of honey bee colony population dynamics.  

PubMed

Since 2006 the rate of honey bee colony failure has increased significantly. As an aid to testing hypotheses for the causes of colony failure we have developed a compartment model of honey bee colony population dynamics to explore the impact of different death rates of forager bees on colony growth and development. The model predicts a critical threshold forager death rate beneath which colonies regulate a stable population size. If death rates are sustained higher than this threshold rapid population decline is predicted and colony failure is inevitable. The model also predicts that high forager death rates draw hive bees into the foraging population at much younger ages than normal, which acts to accelerate colony failure. The model suggests that colony failure can be understood in terms of observed principles of honey bee population dynamics, and provides a theoretical framework for experimental investigation of the problem. PMID:21533156

Khoury, David S; Myerscough, Mary R; Barron, Andrew B

2011-04-18

225

A Quantitative Model of Honey Bee Colony Population Dynamics  

PubMed Central

Since 2006 the rate of honey bee colony failure has increased significantly. As an aid to testing hypotheses for the causes of colony failure we have developed a compartment model of honey bee colony population dynamics to explore the impact of different death rates of forager bees on colony growth and development. The model predicts a critical threshold forager death rate beneath which colonies regulate a stable population size. If death rates are sustained higher than this threshold rapid population decline is predicted and colony failure is inevitable. The model also predicts that high forager death rates draw hive bees into the foraging population at much younger ages than normal, which acts to accelerate colony failure. The model suggests that colony failure can be understood in terms of observed principles of honey bee population dynamics, and provides a theoretical framework for experimental investigation of the problem.

Khoury, David S.; Myerscough, Mary R.; Barron, Andrew B.

2011-01-01

226

Modeling the growth of individuals in crowded plant populations  

Microsoft Academic Search

Aims We present an improved model for the growth of individuals in plant populations experiencing competition. Methods Individuals grow sigmoidally according to the Birch model, which is similar to the more commonly used Richards model, but has the ad- vantage that initial plant growth is always exponential. The individual plant growth models are coupled so that there is a maximum

Christian Damgaard; Jacob Weiner

2008-01-01

227

A population growth model forced by random, episodic disturbances  

NASA Astrophysics Data System (ADS)

As a first step to quantify and better understand the nature of thresholds in ecosystems, a prototype population dynamics model has been developed and analyzed for the case where a population is subjected to random, episodic disturbances. This model assumes that disturbances occur at random times (following a Poisson event process) and have random magnitudes that determine the fraction of the population that survives the disturbance. Disturbances may be events such as fire, drought, disease or infestation. Between disturbances, the model assumes that population growth is deterministic and can be modeled by an exponential or logistic equation. The model is characterized by time, t, and four other parameters: the initial population size, N0, the per capita growth rate, r, the expected number of disturbance events per unit time, ? , and ? = E(X), where X is the random fraction (between 0 and 1) of the population that survives a given disturbance. What is nice about this simple, stochastic model is that it is mathematically tractable and clearly exhibits threshold behavior that can be computed explicitly in terms of the model parameters. In particular, the long-term behavior of the model is characterized by an easily-computed indicator that is a function of the model parameters. Whenever the model parameters are such that this indicator is less than zero, the expected value of the random population size declines over time and is unsustainable. But whenever it is greater than zero, the expected population size grows, despite the random disturbances. The case where the indicator is zero therefore represents a type of critical threshold for this problem that determines whether or not the population is likely to survive the disturbances. A number of analytic results will be presented along with numerical results from a large number of simulations.

Peckham, S. D.

2011-12-01

228

Impact of zooplankton grazing on Alexandrium blooms in the offshore Gulf of Maine  

NASA Astrophysics Data System (ADS)

Zooplankton grazing was investigated by shipboard experiments during natural blooms of Alexandrium spp. in the offshore Gulf of Maine in spring and/or summer of 1998, 2000, and 2001. Grazing studies were done in conjunction with studies of accumulation of Alexandrium toxins in the zooplankton, as part of the ECOHAB-Gulf of Maine regional program. Several species of copepods, marine cladocerans, and appendicularians were allowed to graze upon natural phytoplankton assemblages, at ambient temperatures (14-17 °C). Grazing was measured by quantitative microscopic analyses of disappearance of phytoplankton cells in initial, control, and experimental food suspensions. Thus, we were able to examine grazing upon Alexandrium in comparison to grazing on other co-occurring phytoplankton taxa. Even during Alexandrium "blooms," this dinoflagellate was a minor component of the overall phytoplankton assemblage. It was present at stations where grazing experiments were conducted at levels of 0.12-7.57×10 3 cells l -1, or 0.03-3.93% of total phytoplankton cells. Maximum ingestion of Alexandrium accounted for only up to 3.2% of total cells ingested. Phytoplankton assemblages were dominated by athecate microflagellates, and to a lesser extent by diatoms and non-toxic dinoflagellates. Microflagellates were present at abundances of 159.62-793.93 cells ml -1, or 60.6-95.56% of total cells. Grazing on microflagellates accounted for 35.59-98.21% of total grazing. Grazing on Alexandrium spp. and microflagellates was generally non-selective, with these taxa being ingested in similar proportions to their availability in food assemblages. Grazing on diatoms was selective, with diatoms being disproportionately ingested, compared to their proportions in food assemblages. There were no apparent adverse effects of Alexandrium on grazers during incubations of 18-24 h, and grazer survival was 100%. Estimated daily zooplankton grazing impact on Alexandrium spp. field populations by field populations of experimental grazers averaged 5.79% (range=0-117%). Extrapolating experimentally determined grazing rates to total zooplankton assemblages increased potential grazing impact to 0-667.77% (mean=114.7%). However, these potential impacts are likely overestimations, because toxin accumulation data indicated that many of the most-abundant zooplankters ( Oithona similis copepodites and copepod nauplii) likely graze only minimally upon Alexandrium spp. Thus, antipredation effects of high concentrations of Alexandrium on some grazers reported from some laboratory studies may only occur rarely in nature, because of low individual zooplankter grazing rates on Alexandrium, and dilution of grazing upon it by grazing on other food sources such as abundant microflagellates and diatoms.

Turner, Jefferson T.; Borkman, David G.

2005-09-01

229

A stochastic computer model for simulating population growth  

Microsoft Academic Search

Summary  A model is described for investigating the interactions of age-specific birth and death rates, age distribution and density-governing\\u000a factors determining the growth form of single-species populations. It employs Monte Carlo techniques to simulate the births\\u000a and deaths of individuals while density-governing factors are represented by simple algebraic equations relating survival\\u000a and fecundity to population density. In all respects the model’s

Frank J. Sonleitner

1977-01-01

230

Competition models with niche for squirrel population dynamics  

NASA Astrophysics Data System (ADS)

In this paper we investigate squirrel competition models. More precisely, at first we consider a competition model between red native and grey exotic squirrels, then a model with competition among red native, red indigenous and grey exotic squirrels. We assume that a part of red squirrels can hide in a niche. By adding this hypothesis, we analize if, independently from initial conditions, the grey exotic squirrel population could be prevented from invading the ecosystem and displacing the native populations.

De Rossi, Alessandra; Ferrua, Ilaria; Perracchione, Emma; Ruatta, Giulia; Venturino, Ezio

2013-10-01

231

Sensitivity analysis of periodic matrix population models.  

PubMed

Periodic matrix models are frequently used to describe cyclic temporal variation (seasonal or interannual) and to account for the operation of multiple processes (e.g., demography and dispersal) within a single projection interval. In either case, the models take the form of periodic matrix products. The perturbation analysis of periodic models must trace the effects of parameter changes, at each phase of the cycle, on output variables that are calculated over the entire cycle. Here, we apply matrix calculus to obtain the sensitivity and elasticity of scalar-, vector-, or matrix-valued output variables. We apply the method to linear models for periodic environments (including seasonal harvest models), to vec-permutation models in which individuals are classified by multiple criteria, and to nonlinear models including both immediate and delayed density dependence. The results can be used to evaluate management strategies and to study selection gradients in periodic environments. PMID:23316494

Caswell, Hal; Shyu, Esther

2012-12-01

232

Comparisons of zooplankton community size structure in the Great Lakes  

NASA Astrophysics Data System (ADS)

Zooplankton mean size and size spectra distribution potentially reflect the condition of trophic interactions and ecosystem health because they are affected by both resource availability and planktivore pressure. We assessed zooplankton mean size and size spectra using an optical plankton counter (OPC) on 35 site visits among lakes Superior, Michigan, Huron, Erie, and Ontario (2002-2003). The surveys were conducted in both nearshore regions (5-20 m depth) and on associated transects to offshore regions either greater than 8 km from shore or greater than 100 m depth. The survey sites were distributed across a gradient of land use disturbance in watersheds adjacent to the nearshore regions. The mean size, biomass density, statistical size distribution, and normalized biomass size spectra of zooplankton were determined from OPC measurements for all locations. Significant differences among lakes were observed in mean size, biomass, and the parameters of size spectra distributions for both nearshore and offshore regions. Significant differences within lakes were observed in some parameters that also allowed for significant discrimination between nearshore and offshore zooplankton communities in lakes Michigan (mean size, biomass, one spectral parameter), Ontario (mean size, three spectral parameters), and Superior (one spectral parameter). Similarly, some parameters allowed for discrimination between offshore epilimnion and hypolimnion waters in lakes Michigan (mean size, biomass, and four spectral parameters), Huron (biomass), and Ontario (two spectral parameters). The use of OPC technology and parameters that characterize spectral shape may have potential as an efficient and economic way for developing a size-based zooplankton metric to discriminate among zooplankton communities in the Great Lakes.

Yurista, Peder M.; Kelly, John R.; Miller, Samuel E.

2006-05-01

233

Effects of hydrology on zooplankton communities in high-mountain ponds, Mount Rainier National Park, USA  

USGS Publications Warehouse

Ten high-mountain ponds in Mount Rainier National Park, Washington State, were studied from ice-out in June through September1992 to investigate the influences of fluctuating pond volumes on zooplankton communities. All of the ponds were at maximum volume immediately after ice-out. The temporary pond with the shortest wet phase was inhabited by rotifer taxa with short generation times and a crustacean taxon with the ability to encyst as drought-resistant resting bodies at immature stages of development. Dominant zooplankton taxa in three other temporary ponds and six permanent ponds were similar. Rotifer densities typically were lower in temporary ponds relative to those in permanent ponds, although Brachionus urceolaris was abundant shortly before the temporary ponds dried. Large volume loss was associated with large declines in total abundances of crustacean populations. Daphnia rosea was not present in temporary ponds following fall recharge. In deep-permanent ponds, copepods had slower developmental rates, smaller temporal changes in total abundances of crustacean populations and two additional large-bodied crustacean taxa were present relative to the characteristics of crustacean communities in shallow-permanent ponds. Owing to their small sizes and sensitivity to environmental change, collectively ponds such as these may provide an early signal of long-term climate change in aquatic systems.

Girdner, Scott; Larson, Gary L.

1995-01-01

234

A Hierarchical Bayesian Model for Next-Generation Population Genomics  

PubMed Central

The demography of populations and natural selection shape genetic variation across the genome and understanding the genomic consequences of these evolutionary processes is a fundamental aim of population genetics. We have developed a hierarchical Bayesian model to quantify genome-wide population structure and identify candidate genetic regions affected by selection. This model improves on existing methods by accounting for stochastic sampling of sequences inherent in next-generation sequencing (with pooled or indexed individual samples) and by incorporating genetic distances among haplotypes in measures of genetic differentiation. Using simulations we demonstrate that this model has a low false-positive rate for classifying neutral genetic regions as selected genes (i.e., ?ST outliers), but can detect recent selective sweeps, particularly when genetic regions in multiple populations are affected by selection. Nonetheless, selection affecting just a single population was difficult to detect and resulted in a high false-negative rate under certain conditions. We applied the Bayesian model to two large sets of human population genetic data. We found evidence of widespread positive and balancing selection among worldwide human populations, including many genetic regions previously thought to be under selection. Additionally, we identified novel candidate genes for selection, several of which have been linked to human diseases. This model will facilitate the population genetic analysis of a wide range of organisms on the basis of next-generation sequence data.

Gompert, Zachariah; Buerkle, C. Alex

2011-01-01

235

Models of plant populations and communities  

SciTech Connect

This document is the overview of the plant section in the book, {und Individual-Based Models and Approaches in Ecology}. A brief description of each of the chapters is provided, as well as a comparison of the models presented in each chapter. Four of the six chapters deal with single species interactions, one dealt with a two species system (plants and pollinators) and one deals with multispecies interactions. Both i-state distribution models and i-state configuration models are discussed. (MHB)

Huston, M.

1990-01-01

236

Tidally oriented vertical migration and position maintenance of zooplankton in a temperate estuary  

USGS Publications Warehouse

In many estuaries, maxima in turbidity and abundance of several common species of zooplankton occur in the low salinity zone (LSZ) in the range of 0.5-6 practical salinity units (psu). Analysis of zooplankton abundance from monitoring in 1972-1987 revealed that historical maxima in abundance of the copepod Eurytemora affinis and the mysid Neomysis mercedis, and in turbidity as determined from Secchi disk data, were close to the estimated position of 2 psu bottom salinity. The copepod Sinocalanus doerrii had a maximum slightly landward of that of E. affinis. After 1987 these maxima decreased and shifted to a lower salinity, presumably because of the effects of grazing by the introduced clam Potamocorbula amurensis. At the same time, the copepod Pseudodiaptomus forbesi, the mysid Acanthomysis sp., and amphipods became abundant with peaks at salinity around 0.2-0.5 psu. Plausible mechanisms for maintenance of these persistent abundance peaks include interactions between variation in flow and abundance, either in the vertical or horizontal plane, or higher net population growth rate in the peaks than seaward of the peaks. In spring of 1994, a dry year, we sampled in and near the LSZ using a Lagrangian sampling scheme to follow selected isohalines while sampling over several complete tidal cycles. Acoustic Doppler current profilers were used to provide detailed velocity distributions to enable us to estimate longitudinal fluxes of organisms. Stratification was weak and gravitational circulation nearly absent in the LSZ. All of the common species of zooplankton migrated vertically in response to the tides, with abundance higher in the water column on the flood than on the ebb. Migration of mysids and amphipods was sufficient to override net seaward flow to produce a net landward flux of organisms. Migration of copepods, however, was insufficient to reverse or even greatly diminish the net seaward flux of organisms, implying alternative mechanisms of position maintenance.

Kimmerer, W. J.; Burau, J. R.; Bennett, W. A.

1998-01-01

237

Dynamics of inhomogeneous populations and global demography models  

Microsoft Academic Search

The dynamic theory of inhomogeneous populations developed during the last\\u000adecade predicts several essential new dynamic regimes applicable even to the\\u000awell-known, simple population models. We show that, in an inhomogeneous\\u000apopulation with a distributed reproduction coefficient, the entire initial\\u000adistribution of the coefficient should be used to investigate real population\\u000adynamics. In the general case, neither the average rate

Georgy P. Karev

2005-01-01

238

Modeling population dynamics and conservation of arapaima in the Amazon  

Microsoft Academic Search

To promote understanding of fish population dynamics in tropical river-floodplains, we have synthesized existing information\\u000a by developing a largely empirical population model for arapaima (Arapaima sp.). Arapaima are characterized by very large bodies, relatively late sexual maturity, small clutches, and large parental\\u000a investment per offspring, and their populations are overexploited and even declining due to overfishing. We used unparalleled\\u000a time

L. CastelloD; D. J. Stewart; C. C. Arantes

239

Zooplankton species composition, abundance and biomass on the eastern Bering Sea shelf during summer: The potential role of water-column stability and nutrients in structuring the zooplankton community  

NASA Astrophysics Data System (ADS)

The southeastern Bering Sea sustains one of the largest fisheries in the United States, as well as wildlife resources that support valuable tourist and subsistence economies. The fish and wildlife populations in turn are sustained by a food web linking primary producers to apex predators through the zooplankton community. Recent shifts in climate toward warmer conditions may threaten these resources by altering productivity and trophic relationships in the ecosystem on the southeastern Bering Sea shelf. We examined the zooplankton community near the Pribilof Islands and on the middle shelf of the southeastern Bering Sea in summer of 1999 and 2004 to document differences and similarities in species composition, abundance and biomass by region and year. Between August 1999 and August 2004, the summer zooplankton community of the middle shelf shifted from large to small species. Significant declines were observed in the biomass of large scyphozoans ( Chrysaora melanaster), large copepods ( Calanus marshallae), arrow worms ( Sagitta elegans) and euphausiids ( Thysanoessa raschii, T. inermis) between 1999 and 2004. In contrast, significantly higher densities of the small copepods ( Pseudocalanus spp., Oithona similis) and small hydromedusae ( Euphysa flammea) were observed in 2004 relative to 1999. Stomach analyses of young-of-the-year (age 0) pollock ( Theragra chalcogramma) from the middle shelf indicated a dietary shift from large to small copepods in 2004 relative to 1999. The shift in the zooplankton community was accompanied by a 3-fold increase in water-column stability in 2004 relative to 1999, primarily due to warmer water above the thermocline, with a mean temperature of 7.3 °C in 1999 and 12.6 °C in 2004. The elevated water-column stability and warmer conditions may have influenced the zooplankton composition by lowering summer primary production and selecting for species more tolerant of a warm, oligotrophic environment. A time series of temperature from the middle shelf indicates that the warmer conditions in 2004 are part of a trend rather than an expression of interannual variability. These results suggest that if climate on the Bering Sea shelf continues to warm, the zooplankton community may shift from large to small taxa which could strongly impact apex predators and the economies they support.

Coyle, Kenneth O.; Pinchuk, Alexei I.; Eisner, Lisa B.; Napp, Jeffrey M.

2008-08-01

240

An Inbreeding Model of Associative Overdominance During a Population Bottleneck  

Microsoft Academic Search

Associative overdominance, the fitness difference between heterozygotes and homozygotes at a neutral locus, is classically described using two categories of models: linkage disequilibrium in small populations or identity disequilibrium in infinite, partially selfing populations. In both cases, only equilibrium situations have been considered. In the present study, associative overdominance is related to the distribution of individual inbreeding levels (i.e., genomic

Nicolas Bierne; Anne Tsitrone; Patrice David

2000-01-01

241

Bayesian Computation and Model Selection in Population Genetics  

Microsoft Academic Search

Until recently, the use of Bayesian inference in population genetics was lim- ited to a few cases because for many realistic population genetic models the likelihood function cannot be calculated analytically . The situation changed with the advent of likelihood-free inference algorithms, often subsumed under the term Approximate Bayesian Computation (ABC). A key innovation was the use of a post-sampling

Christoph Leuenberger; Daniel Wegmann; Laurent Excoer

242

Modeling seasonal interactions in the population dynamics of migratory birds  

USGS Publications Warehouse

Understanding the population dynamics of migratory birds requires understanding the relevant biological events that occur during breeding, migratory, and overwintering periods. The few available population models for passerine birds focus on breeding-season events, disregard or oversimplify events during nonbreeding periods, and ignore interactions that occur between periods of the annual cycle. Identifying and explicitly incorporating seasonal interactions into population models for migratory birds could provide important insights about when population limitation actually occurs in the annual cycle. We present a population model for the annual cycle of a migratory bird, based on the American Redstart (Setophaga ruticilla) but more generally applicable, that examines the importance of seasonal interactions by incorporating: (1) density dependence during the breeding and winter seasons, (2) a carry-over effect of winter habitat on breeding-season productivity, and (3) the effects of behavioral dominance on seasonal and habitat specific demographic rates. First, we show that habitat availability on both the wintering and breeding grounds can strongly affect equilibrium population size and sex ratio. Second, sex ratio dynamics, as mediated by behavioral dominance, can affect all other aspects of population dynamics. Third, carry-over effects can be strong, especially when winter events are limiting. These results suggest that understanding the population dynamics of migratory birds may require more consideration of the seasonal interactions induced by carry-over effects and density dependence in multiple seasons. This model provides a framework in which to explore more fully these seasonal dynamics and a context for estimation of life history parameters.

Runge, M.C.; Marra, P.P.

2005-01-01

243

A Role for M-Matrices in Modelling Population Growth  

ERIC Educational Resources Information Center

|Adopting a discrete-time cohort-type model to represent the dynamics of a population, the problem of achieving a desired total size of the population under a balanced growth (contraction) and the problem of maintaining the desired size, once achieved, are studied. Properties of positive-time systems and M-matrices are used to develop the results,…

James, Glyn; Rumchev, Ventsi

2006-01-01

244

Late-summer zooplankton community structure, abundance, and distribution in the Hudson Bay system (Canada) and their relationships with environmental conditions, 2003-2006  

NASA Astrophysics Data System (ADS)

Zooplankton communities were examined for the first time in three different hydrographic regions of the Hudson Bay system (HBS) in early August to early September from 2003 to 2006. Sampling was conducted at 50 stations distributed along different transects located in Hudson Bay (HB), Hudson Strait (HS), and Foxe Basin (FB). Variations in zooplankton biomass, abundance, taxonomic composition, and diversity in relation to environmental variables were studied using multivariate techniques. During all sampling years, the total zooplankton biomass was on average four times lower in HB than in HS and FB. Clustering samples by their relative species compositions revealed no interannual variation in zooplankton community but showed a marked interregional variability between the three regions. Water column stratification explained the greatest proportion (25%) of this spatial variability. According to redundancy analysis (RDA), the zooplankton taxa that contribute most to the separation of the three regions are Microcalanus spp., Oithona similis, Oncaea borealis, Aeginopsis laurentii, Sagitta elegans, Fritillaria sp., and larvae of cnidaria, chaetognatha, and pteropoda in HB; hyperiid amphipods in FB; and Pseudocalanus spp. CI-CV, Calanus glacialis CI-CVI, Calanus finmarchicus CI-CVI, Calanus hyperboreus CV-CVI, Acartia longiremis CI-CV, Metridia longa N3-N6 CI-CIII CVIf, Eukrohnia hamata, larvae of echinodermata, mollusca, cirripedia, appendicularia, and polychaeta in the northwestern and southeastern HS transects. For the HB transect, the RDA analyzed allowed us to distinguish three regions (HB west, central, and east) with different environmental gradients and zooplankton assemblages, in particular higher concentration of Pseudocalanus spp. nauplii and CI-CVI, as well as benthic macrozooplankton and meroplankton larvae in western HB. In HS, Calanoid species (mainly C. finmarchicus and C. glacialis) were mostly observed at the north shore stations associated with the weakly stratified Arctic-North Atlantic waters coming from southwestern Davis Strait (inflow). In general, the RDA models tested among the HBS regions were very consistent with its general surface circulation pattern for summer conditions in terms of environmental variables and distinct zooplankton assemblages. Overall, zooplankton biomass and diversity indices (H?, J?, and S) were lower in the most stratified environment (i.e., HB) than in the deeper (FB) and more dynamic (HS) regions. The results of this work clearly show that the spatial differentiation and structure of the zooplankton communities are strongly influenced by the hydrodynamic conditions in the HBS that, trough their actions on temperature, salinity, stratification, mixing conditions and depth strata, lead to the spatial differentiation of these communities.

Estrada, Rafael; Harvey, Michel; Gosselin, Michel; Starr, Michel; Galbraith, Peter S.; Straneo, Fiammetta

2012-08-01

245

Use of molecular markers as indicators for winter zooplankton grazing on toxic benthic cyanobacteria colonies in an urban Colorado lake  

Microsoft Academic Search

Laboratory experiments provide no general answer to the question of whether zooplankton affects cyanobacteria or are affected by prokaryotes. A cyanobacterium may be grazed upon as small colonies, and the same species, as larger colonies, may inhibit zooplankton feeding. Within zooplankton, different species or groups may be affected differently. With this background we set out to detect winter zooplankton grazing

P. J. Oberholster; A.-M. Botha; T. E. Cloete

2006-01-01

246

Population models of burrowing mayfly recolonization in Western Lake Erie  

USGS Publications Warehouse

Burrowing mayflies, Hexagenia spp. (H. limbata and H. rigida), began recolonizing western Lake Erie during the 1990s. Survey data for mayfly nymph densities indicated that the population experienced exponential growth between 1991 and 1997. To predict the time to full recovery of the mayfly population, we fitted logistic models, ranging in carrying capacity from 600 to 2000 nymphs/m2, to these survey data. Based on the fitted logistic curves, we forecast that the mayfly population in western Lake Erie would achieve full recovery between years 1998 and 2000, depending on the carrying capacity of the western basin. Additionally, we estimated the mortality rate of nymphs in western Lake Erie during 1994 and then applied an age-based matrix model to the mayfly population. The results of the matrix population modeling corroborated the exponential growth model application in that both methods yielded an estimate of the population growth rate, r, in excess of 0.8 yr-1. This was the first evidence that mayfly populations are capable of recolonizing large aquatic ecosystems at rates comparable with those observed in much smaller lentic ecosystems. Our model predictions should prove valuable to managers of power plant facilities along the western basin in planning for mayfly emergences and to managers of the yellow perch (Perca flavescens) fishery in western Lake Erie.

Madenjian, C. P.; Schloesser, D. W.; Krieger, K. A.

1998-01-01

247

A basic population balance model for fluid bed spray granulation  

Microsoft Academic Search

A basic population balance approach is developed for a granulation process in a fluid bed spray granulator. The particle size distribution predicted by the model is confirmed by plant data. Hence this model is considered to be useful to describe and optimize an industrial process. The model depends on a limited number of parameters (most of these factors can be

A. W. Vreman; C. E. van Lare; M. J. Hounslow

2009-01-01

248

Parameter Estimates in Differential Equation Models for Population Growth  

ERIC Educational Resources Information Center

|We estimate the parameters present in several differential equation models of population growth, specifically logistic growth models and two-species competition models. We discuss student-evolved strategies and offer "Mathematica" code for a gradient search approach. We use historical (1930s) data from microbial studies of the Russian biologist,…

Winkel, Brian J.

2011-01-01

249

Toward linking ocean models to fish population dynamics  

Microsoft Academic Search

We discuss Lehodey et al.’s (2009) approach to linking ocean models to population dynamics of large marine predators, consider its benefits and limitations, and outline alternative approaches. We advocate a middle ground between Lehodey et al.’s pragmatic, phenomenological approach and the detailed mechanistic approach common to most individual based models. These models should capture the essence of critical processes controlling

Lawrence J. Buckley; Lauren B. Buckley

2010-01-01

250

A stochastic population model for Lepidium papilliferum - Treesearch  

Treesearch

We modeled the population dynamics of the Snake River Plains ephemeral ... This enabled us to incorporate realistic levels of environmental variability into ... If every year were average in this desert environment, the species could not persist .

251

Demographics of reintroduced populations: estimation, modeling, and decision analysis  

USGS Publications Warehouse

Reintroduction can be necessary for recovering populations of threatened species. However, the success of reintroduction efforts has been poorer than many biologists and managers would hope. To increase the benefits gained from reintroduction, management decision making should be couched within formal decision-analytic frameworks. Decision analysis is a structured process for informing decision making that recognizes that all decisions have a set of components—objectives, alternative management actions, predictive models, and optimization methods—that can be decomposed, analyzed, and recomposed to facilitate optimal, transparent decisions. Because the outcome of interest in reintroduction efforts is typically population viability or related metrics, models used in decision analysis efforts for reintroductions will need to include population models. In this special section of the Journal of Wildlife Management, we highlight examples of the construction and use of models for informing management decisions in reintroduced populations. In this introductory contribution, we review concepts in decision analysis, population modeling for analysis of decisions in reintroduction settings, and future directions. Increased use of formal decision analysis, including adaptive management, has great potential to inform reintroduction efforts. Adopting these practices will require close collaboration among managers, decision analysts, population modelers, and field biologists.

Converse, Sarah J.; Moore, Clinton T.; Armstrong, Doug P.

2013-01-01

252

Invariants for models of interacting populations  

NASA Astrophysics Data System (ADS)

The generalised Lotka-Volterra system is studied. We use a modification of the Carleman embedding method. The position of the equilibrium point, the possibility of obtaining invariants, the asymptotic cyclic motions and the connection to the Volterra model are discussed.

Cairó, L.; Feix, M. R.; Goedert, J.

1989-10-01

253

Invariants for models of interacting populations  

Microsoft Academic Search

The generalised Lotka-Volterra system is studied. We use a modification of the Carleman embedding method. The position of the equilibrium point, the possibility of obtaining invariants, the asymptotic cyclic motions and the connection to the Volterra model are discussed.

M. R. Feix; J. Goedert

1989-01-01

254

THEORETICAL MODELS IN THE HOMELESS POPULATION  

Microsoft Academic Search

Ever since the early eighties, the study of homeless people has been addressed from many theoretical viewpoints. The purpose of this work is, first, to carry out a review of the main studies that have addressed the phenomenon of homelessness from an explicit theoretical model; and second, to study in depth one of the theoretical frameworks that has received the

Manuel Muñoz; Carmelo Vázquez; Sonia Panadero; Aida de Vicente

255

Effects of Climate on the Zooplankton of the California Current  

Microsoft Academic Search

Almost six decades of sampling of the California Current system, carried out by the CalCOFI program (California Cooperative Fisheries Investigation) complemented by a decade of observations from the IMECOCAL program (Investigaciones Mexicanas de la Corriente de California), have revealed changing patterns in zooplankton abundances, species composition, and distributions over interannual through multidecadal time scales. Interannual changes associated with ENSO variability

B. E. Lavaniegos

2007-01-01

256

Grazing by rotifers and crustacean zooplankton on nanoplanktonic protists  

Microsoft Academic Search

Predation on nanoflagellates by metazoan zooplankton was investigated using a radioactively labeled flagellate, Poterioochromonas malhamensis, as a tracer cell in laboratory incubations of freshly collected plankton assemblages. Experiments conducted in the fall, winter and spring indicated that rotifers dominated the grazing on nanoflagellates by metazoans in the winter (68%) and spring (92%). Rotifer grazing was not determined in the autumn.

Robert W. Sanders; Douglas A. Leeper; C. Harold King; Karen G. Porter

1994-01-01

257

Zooplankton as Potential Indicators of Biotic Condition in Large Rivers  

Microsoft Academic Search

As part of the Environmental Monitoring and Assessment Program (EMAP), supported by the U.S. Environmental Protection Agency, we are examining zooplankton diversity and abundance in three large rivers (Missouri, Ohio, and upper Mississippi). These rivers are particularly interesting because of large differences in their hydrologic patterns, resulting primarily from their different management strategies. Preliminary data from summer 2004 surveys of

K. A. Medley; J. E. Havel; J. D. Jack

2005-01-01

258

Effect of various intake designs on zooplankton entrainment  

SciTech Connect

Field studies were conducted at the intakes of three Tennessee Valley Authority electric power plants to determine whether intake design is a feasible means of mitigating effects on zooplankton by minimizing the quantity entrained. Three intake designs were evaluated: one with a shallow skimmer wall, one with a deep skimmer wall, and one with no skimmer wall. Many sample sets from these studies were highly variable because of inadequate sample replication, thus precluding the use of statistical tests on some of the data. Where possible, an analysis of variance and a Student, Newman, Keuls multiple range test were computed and tested at the 0.05 level. Several studies indicated possible differences between day and night in the quantity of zooplankton entrained. The greater quantities entrained at night were related to a greater abundance in the source water body at night rather than to intake design. These results indicate that time-of-day differences might be used to mitigate effects on zooplankton at some intakes if the intake could be operated to require less cooling water when concentrations were greatest. None of these studies indicated that the intake designs studied minimized the quantity of zooplankton entrained because the quantities in the intake canals were similar to the quantities in the source water body.

Dycus, D.L.

1983-03-01

259

Lake St. Clair zooplankton: Evidence for post-dreissena changes  

USGS Publications Warehouse

We surveyed the zooplankton of Lake St. Clair at 12 sites over ten dates from May to October 2000. Mean zooplankton density by site and date was 168.6 individuals/L, with Dreissena spp. veligers the most abundant taxon at 122.7 individuals/L. Rotifers, copepods, and cladocerans were far lower in mean abundance than in the early 1970s (rotifers, 20.9/L; copepods, 18.1/L; and cladocerans, 6.8/L). Species richness of zooplankton taxa in 2000 was 147, which was virtually unchanged from that of the first reported survey in 1894. Overall, the decline in abundance was greatest for rotifers (-90%) and about equal for cladocerans (-69%) and copepods (-66%). The decrease in abundance of Daphnia spp. was especially dramatic in Canadian waters. The decline in the southeastern region was significant for all three major groups of zooplankton, whereas in the northwestern region the decline was significant only for rotifers. From June to August 2000, Lake St. Clair open waters were numerically dominated by Dreissena spp. veligers, with a reduced abundance of rotifers and crustaceans compared to pre-Dreissena spp. surveys. Mean nutrient concentrations were not different from the 1970s, but Secchi depth (greater) and chlorophyll a concentration (lower) were. Disproportionate reduction in rotifer abundance is consistent with hypotheses implicating direct consumption by settled Dreissena spp. Reduction of crustaceans is likely due to more complex interactions including removal of nauplii as well as resource competition for phytoplankton.

David, K. A.; Davis, B. M.; Hunter, R. D.

2009-01-01

260

Zooplankton fecal pellets link fossil fuel and phosphate deposits  

SciTech Connect

Fossil zooplankton fecal pellets found in thinly bedded marine and lacustrine black shales associated with phosphate, oil, and coal deposits, link the deposition of organic matter and biologically associated minerals with planktonic ecosystems. The black shales were probably formed in the anoxic basins of coastal marine waters, inland seas, and rift valley lakes where high productivity was supported by runoff, upwelling, and outwelling.

Porter, K.G. (Univ. of Georgia, Athens); Robbins, E.I.

1981-05-22

261

Toxic marine phytoplankton, zooplankton grazers, and pelagic food webs  

Microsoft Academic Search

Interactions between toxic phytoplankton and their zooplankton grazers are complex. Some zooplanktcrs ingest some toxic phytoplankters with no apparent harm, whereas others are deleteriously affected. Phycotoxins vary in their modes of action, levels of toxicity and solubility, and affect grazers in different ways. Beyond effects on direct grazers, toxins may accumulate in and be transfcrrcd through marine food webs, affecting

JefSerson T. Turner; Patricia A. Tester

1997-01-01

262

Zooplankton abundance and diversity in Central Florida grass carp ponds  

Microsoft Academic Search

The effect of the Asian grass carp (Ctenopharyngodon idella Val.) upon the zooplankton in three adjacent experimental ponds (0.139 ha each) was studied for one year. The ponds contained nine species of aquatic macrophytes. Grass carp were stocked into Pond 1 (65 per ha) and Pond 2 (611 per ha) three months after the study was started. At the time

Douglas L. Fry; John A. Osborne

1980-01-01

263

Chemical composition of antarctic zooplankton during austral fall and winter  

Microsoft Academic Search

Water level, ash content, proximate (protein, lipid, carbohydrate and chitin) and elemental (carbon and nitrogen) composition were analyzed in twentythree species of Antarctic Zooplankton collected during the austral fall (1986) and winter (1988) from the Scotia\\/Weddell Sea region. Extremes in water level, ash content and organic components were typified by copepods and gelatinous forms. Ostracods and polychaetes were generally similar

J. Donnelly; J. J. Torres; T. L. Hopkins; T. M. Lancraft

1994-01-01

264

Evolutionary adaptation of marine zooplankton to global change.  

PubMed

Predicting the response of the biota to global change remains a formidable endeavor. Zooplankton face challenges related to global warming, ocean acidification, the proliferation of toxic algal blooms, and increasing pollution, eutrophication, and hypoxia. They can respond to these changes by phenotypic plasticity or genetic adaptation. Using the concept of the evolution of reaction norms, I address how adaptive responses can be unequivocally discerned from phenotypic plasticity. To date, relatively few zooplankton studies have been designed for such a purpose. As case studies, I review the evidence for zooplankton adaptation to toxic algal blooms, hypoxia, and climate change. Predicting the response of zooplankton to global change requires new information to determine (a) the trade-offs and costs of adaptation, (b) the rates of evolution versus environmental change, (c) the consequences of adaptation to stochastic or cyclic (toxic algal blooms, coastal hypoxia) versus directional (temperature, acidification, open ocean hypoxia) environmental change, and (d) the interaction of selective pressures, and evolutionary and ecological processes, in promoting or hindering adaptation. PMID:22809192

Dam, Hans G

2012-07-31

265

Quantifying Linkages among Gizzard Shad, Zooplankton, and Phytoplankton in Reservoirs  

Microsoft Academic Search

Food webs in northern temperate lakes frequently exhibit tightly linked interactions between adjacent trophic levels that lead to top-down effects from piscivores to phytoplankton . To determine if these interactions occur in reservoirs dominated by an omnivorous planktivore, gizzard shad Dorosoma cepedianum, we experimentall y quantified crustacean zooplankton and phytoplankton responses to age-0 gizzard shad (23-90 mm total length) at

JOHN M. DETTMERS; ROY A. STEIN

1996-01-01

266

Zooplankton responses to acidification: A review of laboratory bioassays  

Microsoft Academic Search

This literature review summarizes laboratory bioassays of the effects of acidification on 32 zooplankton taxa. Low pH adversely affected survival, longevity, reproduction, Na flux, heart rate, growth rate, feeding or filtering rate, and respiration rate. The organisms most studied have been daphnids, specifically Daphnia magna and D. pulex. Recommendations for further research include analyses of sublethal effects on zooplankters other

Andrea Locke

1991-01-01

267

From home range dynamics to population cycles: validation and realism of a common vole population model for pesticide risk assessment.  

PubMed

Despite various attempts to establish population models as standard tools in pesticide risk assessment, population models still receive limited acceptance by risk assessors and authorities in Europe. A main criticism of risk assessors is that population models are often not, or not sufficiently, validated. Hence the realism of population-level risk assessments conducted with such models remains uncertain. We therefore developed an individual-based population model for the common vole, Microtus arvalis, and demonstrate how population models can be validated in great detail based on published data. The model is developed for application in pesticide risk assessment, therefore, the validation covers all areas of the biology of the common vole that are relevant for the analysis of potential effects and recovery after application of pesticides. Our results indicate that reproduction, survival, age structure, spatial behavior, and population dynamics reproduced from the model are comparable to field observations. Also interannual population cycles, which are frequently observed in field studies of small mammals, emerge from the population model. These cycles were shown to be caused by the home range behavior and dispersal. As observed previously in the field, population cycles in the model were also stronger for longer breeding season length. Our results show how validation can help to evaluate the realism of population models, and we discuss the importance of taking field methodology and resulting bias into account. Our results also demonstrate how population models can help to test or understand biological mechanisms in population ecology. PMID:23086922

Wang, Magnus

2013-02-19

268

The role of zooplankton in the cycling and remineralization of chemical materials in the Southern California Bight  

SciTech Connect

The overall objective of our research is to understand the transport pathways and mass balances of selected metabolically active and inactive chemical species in the Santa Monica/San Pedro Basins. One focus of our study is to examine the role of zooplankton and micronekton in the cycling and remineralization of chemical materials in the Southern California Bight, with particular reference to C, N and certain radionuclides and trace metals. A second focus is to examine these same radionuclides and trace metals in other important reservoirs. Knowledge of the rates and routes of transfer of these nuclides and metals through these reservoirs should lead to a cogent model for these elements in SM/SP Basins. Our zooplankton C and N data, should lead ultimately to a model of C and N cycling in the upper water column. Our sediment core data will lead to the construction of mass balances and budgets in the SM/SP Basins. 4 refs.

Small, L.F.; Huh, Chih-An.

1988-01-01

269

Effects of Climate on the Zooplankton of the California Current  

NASA Astrophysics Data System (ADS)

Almost six decades of sampling of the California Current system, carried out by the CalCOFI program (California Cooperative Fisheries Investigation) complemented by a decade of observations from the IMECOCAL program (Investigaciones Mexicanas de la Corriente de California), have revealed changing patterns in zooplankton abundances, species composition, and distributions over interannual through multidecadal time scales. Interannual changes associated with ENSO variability are manifested as strong but transitory perturbations in the mean annual cycle in seasonal abundances (and distributions) of particular species. An investigation of longer- term change, limited to the region off southern California, shows a persistent decline in zooplankton volumes (a proxy for overall biomass of macrozooplankton) between 1977 and 1998 that is considered to be a response to the well documented shift in basin-scale climate forcing that occurred in 1976-77. Further examination of this decline in zooplankton volumes indicates that it was due principally to the disappearance of several salp species after 1977. Other species and functional groups did not decline after the change in climate regime, while some species have followed persistent secular trends that appear to be associated more with the phenomenon of long-term global warming. Differences in the regional responses to climate change throughout the California Current system have also been observed recently in the spatial distribution of zooplankton biomass and changes in latitudinal ranges of certain species. For example, zooplankton biomass in the Baja California region show typical values for the 1997-98 El Niño that were followed by a decrease during the sharp transition to the cool La Niña conditions in 1999. This contrasts with the nearby region off southern California that was characterized by reduced biomass during the El Niño period and the subsequent recovery during the La Niña. Another regional contrast in zooplankton distribution observed recently was the significant presence of subarctic euphausiid species off Baja California during July 2005, while the krill collapsed in the region off Oregon in the same period. It is reasonable to suspect that regional contrasts in the zooplankton abundance and species distributions may increase as a response to latitudinal shifts in habitat character due to global warming.

Lavaniegos, B. E.

2007-05-01

270

Nonstationary modeling of neural population dynamics.  

PubMed

A stochastic state point-process adaptive filter was used to track the temporal evolution of several simulated nonlinear dynamical systems. The estimated Laguerre coefficients and Laguerre poles were used to reconstruct the feedforward and feedback kernels in the system. Simulations showed that the proposed method could track the actual underlying changes of nonlinear kernels using spike input and spike output information alone. The estimated models also converge quickly to the actual models after abrupt step changes in kernels. The proposed method can be used to track the functional input-output properties of neural systems as a result of learning, changes in context, aging or other factors in the natural flow of behavioral events. PMID:19963837

Chan, Rosa H M; Song, Dong; Berger, Theodore W

2009-01-01

271

Stochastic dynamic population model for northern corn rootworm (Coleoptera: Chrysomelidae).  

PubMed

A stochastic dynamic population model for the complete life cycle of northern corn rootworm, Diabrotica barberi Smith & Lawrence, is described. Adult population dynamics from emergence to oviposition are based on a published single-season model for which temperature-dependent development and age-dependent advancement determine adult population dynamics and oviposition. Randomly generated daily temperatures make this model component stochastic. Stochastic hatch is 50+/-8%. A stochastic nonlinear density-dependent larval survival model is estimated using field data from artificial infestation experiments. A regional model of corn phenology is estimated to incorporate the effect of dispersal on adult mortality. Random daily weather is generated using parameters for Brookings, SD. Model performance is evaluated with deterministic simulations, which show that the population converges to zero unless adult mortality is reduced by the availability of corn pollen from the regional model of corn phenology. Stochastic model performance is evaluated with stochastic daily weather, egg hatch, and larval survival in various combinations. Sensitivity analysis is conducted to evaluate model responsiveness to each parameter. Model results are generally consistent with published data. PMID:11425012

Mitchell, P D; Riedell, W E

2001-06-01

272

Population genetics models of transposable elements  

Microsoft Academic Search

The control of transposable element copy number is of considerable theoretical and empirical interest. Under simple models,\\u000a copy numbers may increase without limit. Mechanisms that can prevent such an increase include those in which the effect of\\u000a selection increases with copy number, those in which the rate of transposition decreases with copy number, and those where\\u000a unlimited increase in copy

John F. Y. Brookfield; Richard M. Badge

1997-01-01

273

Convergence to equilibria in discrete population models  

Microsoft Academic Search

For a family of difference equations where and is continuous and decreasing, we find sufficient conditions for the convergence of all solutions to the unique positive equilibrium. In particular, we improve, up to our knowledge, all previous results on the global asymptotic stability of the equilibrium in the particular cases of the discrete Mackey–Glass and Lasota–Wazewska models in blood-cells production.

Hassan A. El-Morshedy; Eduardo Liz

2005-01-01

274

Population Pharmacokinetic-Pharmacodynamic Model of Craving in an Enforced Smoking Cessation Population: Indirect Response and Probabilistic Modeling  

Microsoft Academic Search

Purpose. A population pharmacokinetic-pharmacodynamic model accounting for placebo effect was used to relate nicotine concentration and enforced smoking cessation craving score measured by the Tiffany rating scale short form.

Roberto Gomeni; Vincenzo Teneggi; Laura Iavarone; Lisa Squassante; Alan Bye

2001-01-01

275

Finite element approximation of a population spatial adaptation model.  

PubMed

In [18], Sighesada, Kawasaki and Teramoto presented a system of partial differential equations for modeling spatial segregation of interacting species. Apart from competitive Lotka-Volterra (reaction) and population pressure (cross-diffusion) terms, a convective term modeling the populations attraction to more favorable environmental regions was included. In this article, we study numerically a modification of their convective term to take account for the notion of spatial adaptation of populations. After describing the model, in which a time non-local drift term is considered, we propose a numerical discretization in terms of a mass-preserving time semi-implicit finite element method. Finally, we provied the results of some biologically inspired numerical experiments showing qualitative differences between the original model of [18] and the model proposed in this article. PMID:23906141

Galiano, Gonzalo; Velasco, Julian

2013-06-01

276

Solar UVB-induced DNA damage and photoenzymatic DNA repair in antarctic zooplankton  

PubMed Central

The detrimental effects of elevated intensities of mid-UV radiation (UVB), a result of stratospheric ozone depletion during the austral spring, on the primary producers of the Antarctic marine ecosystem have been well documented. Here we report that natural populations of Antarctic zooplankton also sustain significant DNA damage [measured as cyclobutane pyrimidine dimers (CPDs)] during periods of increased UVB flux. This is the first direct evidence that increased solar UVB may result in damage to marine organisms other than primary producers in Antarctica. The extent of DNA damage in pelagic icefish eggs correlated with daily incident UVB irradiance, reflecting the difference between acquisition and repair of CPDs. Patterns of DNA damage in fish larvae did not correlate with daily UVB flux, possibly due to different depth distributions and/or different capacities for DNA repair. Clearance of CPDs by Antarctic fish and krill was mediated primarily by the photoenzymatic repair system. Although repair rates were large for all species evaluated, they were apparently inadequate to prevent the transient accumulation of substantial CPD burdens. The capacity for DNA repair in Antarctic organisms was highest in those species whose early life history stages occupy the water column during periods of ozone depletion (austral spring) and lowest in fish species whose eggs and larvae are abundant during winter. Although the potential reduction in fitness of Antarctic zooplankton resulting from DNA damage is unknown, we suggest that increased solar UV may reduce recruitment and adversely affect trophic transfer of productivity by affecting heterotrophic species as well as primary producers.

Malloy, Kirk D.; Holman, Molly A.; Mitchell, David; Detrich, H. William

1997-01-01

277

Estimation of population size using open capture-recapture models  

USGS Publications Warehouse

One of the most important needs for wildlife managers is an accurate estimate of population size. Yet, for many species, including most marine species and large mammals, accurate and precise estimation of numbers is one of the most difficult of all research challenges. Open-population capture-recapture models have proven useful in many situations to estimate survival probabilities but typically have not been used to estimate population size. We show that open-population models can be used to estimate population size by developing a Horvitz-Thompson-type estimate of population size and an estimator of its variance. Our population size estimate keys on the probability of capture at each trap occasion and therefore is quite general and can be made a function of external covariates measured during the study. Here we define the estimator and investigate its bias, variance, and variance estimator via computer simulation. Computer simulations make extensive use of real data taken from a study of polar bears (Ursus maritimus) in the Beaufort Sea. The population size estimator is shown to be useful because it was negligibly biased in all situations studied. The variance estimator is shown to be useful in all situations, but caution is warranted in cases of extreme capture heterogeneity.

McDonald, T. L.; Amstrup, S. C.

2001-01-01

278

Predicting Random Effects with an Expanded Finite Population Mixed Model  

PubMed Central

Prediction of random effects is an important problem with expanding applications. In the simplest context, the problem corresponds to prediction of the latent value (the mean) of a realized cluster selected via two-stage sampling. Recently, Stanek and Singer (JASA, 2004) developed best linear unbiased predictors (BLUP) under a finite population mixed model that outperform BLUPs from mixed models and superpopulation models. Their setup, however, does not allow for unequally sized clusters. To overcome this drawback, we consider an expanded finite population mixed model based on a larger set of random variables that span a higher dimensional space than those typically applied to such problems. We show that BLUPs for linear combinations of the realized cluster means derived under such a model have considerably smaller mean squared error (MSE) than those obtained from mixed models, superpopulation models, and finite population mixed models. We motivate our general approach by an example developed for two-stage cluster sampling and show that it faithfully captures the stochastic aspects of sampling in the problem. We also consider simulation studies to illustrate the increased accuracy of the BLUP obtained under the expanded finite population mixed model.

Stanek, Edward J.; Singer, Julio M.

2008-01-01

279

Trophic accumulation of PSP toxins in zooplankton during Alexandrium fundyense blooms in Casco Bay, Gulf of Maine, April June 1998. I. Toxin levels in A. fundyense and zooplankton size fractions  

NASA Astrophysics Data System (ADS)

The transfer of marine algal toxins involving a range of phytoplanktivorous vectors is well documented as a means of exposing organisms at higher trophic levels (including humans) to these naturally occurring yet harmful compounds. While previous studies have examined the potential for, and dynamics of, algal toxin accumulation by individual zooplankton species, few have attempted to distinguish the contribution of various grazer size classes to toxin trophic transfer in natural communities and characterize some of the factors that can influence this process. The current investigation was aimed at describing the size-fractioned (64-100, 100-200, 200-500, >500 ?m) accumulation of paralytic shellfish poisoning (PSP) toxins by zooplankton in Casco Bay and the adjacent coastal waters of the Gulf of Maine during a series of cruises from April to June 1998. Several variables, including the abundance of PSP toxin-producing Alexandrium fundyense, in-water toxin concentrations associated with this dinoflagellate, and algal toxin cell quotas, were measured and their relationship to zooplankton toxin accumulation assessed. A principal finding of this work was the ability of any grazer size class examined (including grazers present in the 20-64 ?m A. fundyense-containing fraction) to serve as an initial vector for introducing PSP toxins into the Casco Bay food web at various times during the sampling period, thereby providing multiple potential routes of toxin trophic transfer. In addition, trends observed in the coincident mapping of A. fundyense cells and their associated toxin were generally in agreement, yet did not remain closely coupled at all times. Therefore, although A. fundyense abundance can be a reasonable indicator of PSP toxin presence in the phytoplankton, this relationship can vary considerably and lead to situations where elevated toxin levels occur at low cell concentrations and vice versa. The uncoupling of A. fundyense cell and in-water toxin concentrations in the 20-64 ?m, A. fundyense-containing size fraction implied fluctuations in the algal toxin cell quota, which ranged from ca. 10 to 2000 fmol STX equiv. cell -1. Some of this variability may reflect the changing presence in this size fraction of grazers (e.g., tintinnids) capable of toxin accumulation, causing an upward bias in A. fundyense toxin cell quota estimates. Overall, the extent of PSP toxin transfer into zooplankton will be determined by a complex interaction among several factors, including A. fundyense and grazer abundance, algal toxin cell quota, and zooplankton community composition. An ability to predict zooplankton toxin accumulation will require further investigation of the relationships between these and other factors, aimed specifically at modeling the process of toxin trophic transfer to grazers and ultimately to their predators.

Doucette, Gregory J.; Turner, Jefferson T.; Powell, Christine L.; Keafer, Bruce A.; Anderson, Donald M.

2005-09-01

280

Appropriate Error Models: the Unseen Population  

NASA Astrophysics Data System (ADS)

Surveys and catalogs are often generated with a specific purpose in mind. This is an advantage in the short run, but can be crippling in the long run, because questions will be asked of these data that were not envisioned by the creators. When new analyses are performed, if the proper error model is not available for the data, the results of the analyses will be subject to biases and will be unreliable. The obvious solution to this problem is to retain all of the raw data, but that is not always feasible. This is especially troublesome for undetected sources, which can only be characterized by upper limits to their intensities. We discuss what is required to estimate these upper limits, what kind of information must be stored to enable it, and how much the storage could be decimated before systematic errors in the estimates become important. This work is supported by the NASA/AISRP grant NNG06GF17G.

Kashyap, Vinay

2009-01-01

281

An aerial sightability model for estimating ferruginous hawk population size  

USGS Publications Warehouse

Most raptor aerial survey projects have focused on numeric description of visibility bias without identifying the contributing factors or developing predictive models to account for imperfect detection rates. Our goal was to develop a sightability model for nesting ferruginous hawks (Buteo regalis) that could account for nests missed during aerial surveys and provide more accurate population estimates. Eighteen observers, all unfamiliar with nest locations in a known population, searched for nests within 300 m of flight transects via a Maule fixed-wing aircraft. Flight variables tested for their influence on nest-detection rates included aircraft speed, height, direction of travel, time of day, light condition, distance to nest, and observer experience level. Nest variables included status (active vs. inactive), condition (i.e., excellent, good, fair, poor, bad), substrate type, topography, and tree density. A multiple logistic regression model identified nest substrate type, distance to nest, and observer experience level as significant predictors of detection rates (P < 0.05). The overall model was significant (??26 = 124.4, P < 0.001, n = 255 nest observations), and the correct classification rate was 78.4%. During 2 validation surveys, observers saw 23.7% (14/59) and 36.5% (23/63) of the actual population. Sightability model predictions, with 90% confidence intervals, captured the true population in both tests. Our results indicate standardized aerial surveys, when used in conjunction with the predictive sightability model, can provide unbiased population estimates for nesting ferruginous hawks.

Ayers, L. W.; Anderson, S. H.

1999-01-01

282

Matrix Population Models as Relevant Modeling Tools in Ecotoxicology  

Microsoft Academic Search

\\u000a Nowadays, one of the big challenge in ecotoxicology is to understand how individually measured effects can be used as predictive\\u000a indices at the population level. A particular interesting aspect is to evaluate how individual measures of fitness and survival\\u000a under various toxic conditions can be used to estimate the asymptotic population growth rate known as one of the most robust

Sandrine Charles; Elise Billoir; Christelle Lopes; Arnaud Chaumot

283

A Dose-Structured Population Dynamics Model for Outmigrant Salmon  

NASA Astrophysics Data System (ADS)

The response of fish populations to differing levels of exposure to stressor chemical is commonly characterized using canonical dose-response models that are calibrated in laboratory (e.g., toxicological) studies. Use of such information in the study of migrating populations is difficult because dose received in the environment can vary greatly within a population due to the heterogeneity of the mixing between population members and stressor chemicals. Thus direct use of dose-response models is often predicated on assumptions of complete mixing in the environment. To relax this assumption it is required to devise an approach that keeps track of dose as a distributed quantity over a population. Here such a method is described that uses an added dimension of exposure-time to keep track of the mixing time, or dose, between outmigrant Fall Chinook Salmon and stressor organic contaminants. A mathematical model for the fish population dynamics is developed in the form of a first-order partial differential equation in multiple structural dimensions of dose, size, and age, in addition to space and time. A method-of-characteristics solution to the model under some simplifying conditions is presented and described. The results shed light on the nature of the distribution of outmigrant salmon over structural variables on arrival at the ocean.

Ginn, T. R.; Loge, F. J.

2004-12-01

284

FISHERY-ORIENTED MODEL OF MARYLAND OYSTER POPULATIONS  

EPA Science Inventory

We used time series data to calibrate a model of oyster population dynamics for Maryland's Chesapeake Bay. Model parameters were fishing mortality, natural mortality, recruitment, and carrying capacity. We calibrated for the Maryland bay as a whole and separately for 3 salinity z...

285

Mathematical Modelling of Droplet Atomization Using the Population Balance Equation  

Microsoft Academic Search

This study investigates numerically the atomization process occurring in a plain jet airblast atomizer. The population balance equation is solved for the dispersed phase coupled with a CFD Eulerian multi-fluid model. The Sauter mean diameter values obtained numerically compare favorably with previous experimental data only at certain flow conditions. Finally, this study proposes some enhancements on using the numerical model

Hossam S. Aly; Tholudin M. Lazim; Yehia A. Eldrainy; Mohammad Nazri Mohd Jaafar

2009-01-01

286

Computer models of parasite populations and anthelmintic resistance  

Microsoft Academic Search

1. Summary Computer models of parasite epidemiology can be used to investigate integrated parasite management programs and their effects on worm control and anthelmintic resistance. Models for Trichostrongylus, Ostertagia and Haemonchus incorporate worm parasite populations, climate, grazing management, host immunity, drug use and selection for drug resistance, and can be used to explore how treatment frequency, pasture rotation, drug persistency

RJ Dobson; EH Barnes

287

Modeling Of Honey Bee And Varroa Mite Population Dynamics  

Microsoft Academic Search

The life history of the honey bee Apis mellifera and the bee mite Farroa jacobsoni and their interactions were modeled using a commercial software package known as Stella II. Stella II provides a non- mathematically intensive modeling technique that allows the user to generate a series of differential equations that can track a population through time with a minimum set

Roger Hoopingarner

288

Dealing with Uncertainty in Spatially Explicit Population Models  

Microsoft Academic Search

It has been argued that spatially explicit population models (SEPMs) cannot provide reliable guidance for conservation biology because of the difficulty of obtaining direct estimates for their demographic and dispersal parameters and because of error propagation. We argue that appropriate model calibration procedures can access additional sources of information, compensating the lack of direct parameter estimates. Our objective is to

Thorsten Wiegand; Eloy Revilla; Felix Knauer

2004-01-01

289

Population dynamics of denitrifying bacteria in a model biocommunity  

Microsoft Academic Search

Accumulation of toxic nitrite is frequently observed during waste water treatment. In this study, a model biocommunity was established to investigate alterations in the population of nitrate reducing bacteria affecting the reduction of nitrate and nitrite. The model biocommunity contained a Pseudomonas pseudoalcaligenes strain, which reduced nitrate to N2O or N2 without any nitrite accumulation, Bacillus niacini which reduced nitrate

M Martienssen; R Schöps

1999-01-01

290

Population size dependent incidence in models for diseases without immunity  

Microsoft Academic Search

Epidemiological models of SIS type are analyzed to determine the thresholds, equilibria, and stability. The incidence term in these models has a contact rate which depends on the total population size. The demographic structures considered are recruitment-death, generalized logistic, decay and growth. The persistence of the disease combined with disease-related deaths and reduced reproduction of infectives can greatly affect the

Jinshi Zhou; Herbert W. Hethcote

1994-01-01

291

A sharp global stability result for a discrete population model  

NASA Astrophysics Data System (ADS)

We get a sharp global stability result for a first order difference equation modelling the growth of bobwhite quail populations. The corresponding higher-dimensional model is also discussed, and our stability conditions improve other recent results for the same equation.

Liz, Eduardo

2007-06-01

292

The population model of bone remodelling employed the optimal control.  

PubMed

Several models have been developed in recent years which apply population dynamics methods to describe the mechanisms of bone remodelling. This study incorporates the population kinetics model of bone turnover (including the osteocyte loop regulation) with the optimal control technique. Model simulations have been performed with a wide range of rate parameters using the Monte Carlo method. The regression method has also been used to investigate the interdependence of the location of equilibrium and the characteristics of the equilibrium/relaxation time on the rate parameters employed. The dynamic optimal control outlook for the regulation of bone remodelling processes, in the context of the osteocyte-control population model, has been discussed. Optimisation criteria have been formulated from the perspective of the energetic and metabolic losses in the tissue, with respect to the performance of the bone multicellular unit. PMID:22941201

Moroz, Adam

2012-08-31

293

Population synthesis models in 2D/3D: some rules  

NASA Astrophysics Data System (ADS)

Population synthesis models are a tool extensively used to make inferences about the evolutionary status of stellar populations. In this work I examine the implicit priors assumed to obtain inferences by comparing observational data with populations synthesis models. As a result from this kind of study, I show how a higher spatial resolution can be used to obtain better global (but not spatially detailed) properties of the system. I also show that a pixel-by-pixel (or IFU by IFU) analysis would provide biased results unless they take into account the correlations of stellar populations between different resolution elements (pixels or IFUs) and a prior hypothesis on the projected stellar mass distribution (equivalent to a prior hypothesis on the star formation history)

Cerviño, M.

2013-05-01

294

Penna Bit-String Model with Constant Population  

NASA Astrophysics Data System (ADS)

We removed from the Penna model for biological aging any random killing Verhulst factor. Deaths are due only to genetic diseases and the population size is fixed, instead of fluctuating around some constant value. We show that these modifications give qualitatively the same results obtained in an earlier paper, where the random killings (used to avoid an exponential increase of the population) were applied only to newborns.

de Oliveira, P. M. C.; de Oliveira, S. Moss; Sá Martins, J. S.

295

Econometric model for age- and population-dependent radiation exposures  

SciTech Connect

The economic impact associated with ionizing radiation exposures in a given human population depends on numerous factors including the individual's mean economic status as a function age, the age distribution of the population, the future life expectancy at each age, and the latency period for the occurrence of radiation-induced health effects. A simple mathematical model has been developed that provides an analytical methodology for estimating the societal econometrics associated with radiation effects are to be assessed and compared for economic evaluation.

Sandquist, G.M.; Slaughter, D.M. (Univ. of Utah, Salt Lake City (United States)); Rogers, V.C.

1991-01-01

296

Sample Size Computations for PK\\/PD Population Models  

Microsoft Academic Search

We describe an accurate, yet simple and fast sample size computation method for hypothesis testing in population PK\\/PD studies. We use a first order approximation to the nonlinear mixed effects model and chi-square distributed Wald statistic to compute the minimum sample size to achieve given degree of power in rejecting a null hypothesis in population PK\\/PD studies. The method is

Dongwoo Kang; Janice B. Schwartz; Davide Verotta

2005-01-01

297

Estimating genetic parameters in natural populations using the "animal model".  

PubMed Central

Estimating the genetic basis of quantitative traits can be tricky for wild populations in natural environments, as environmental variation frequently obscures the underlying evolutionary patterns. I review the recent application of restricted maximum-likelihood "animal models" to multigenerational data from natural populations, and show how the estimation of variance components and prediction of breeding values using these methods offer a powerful means of tackling the potentially confounding effects of environmental variation, as well as generating a wealth of new areas of investigation.

Kruuk, Loeske E B

2004-01-01

298

On population size estimators in the poisson mixture model.  

PubMed

Estimating population sizes via capture-recapture experiments has enormous applications. The Poisson mixture model can be adopted for those applications with a single list in which individuals appear one or more times. We compare several nonparametric estimators, including the Chao estimator, the Zelterman estimator, two jackknife estimators and the bootstrap estimator. The target parameter of the Chao estimator is a lower bound of the population size. Those of the other four estimators are not lower bounds, and they may produce lower confidence limits for the population size with poor coverage probabilities. A simulation study is reported and two examples are investigated. PMID:23865502

Mao, Chang Xuan; Yang, Nan; Zhong, Jinhua

2013-07-19

299

The Impact of Fish Predation and Cyanobacteria on Zooplankton Size Structure in 96 Subtropical Lakes  

PubMed Central

Zooplankton are relatively small in size in the subtropical regions. This characteristic has been attributed to intense predation pressure, high nutrient loading and cyanobacterial biomass. To provide further information on the effect of predation and cyanobacteria on zooplankton size structure, we analyzed data from 96 shallow aquaculture lakes along the Yangtze River. Contrary to former studies, both principal components analysis and multiple regression analysis showed that the mean zooplankton size was positively related to fish yield. The studied lakes were grouped into three types, namely, natural fishing lakes with low nutrient loading (Type1), planktivorous fish-dominated lakes (Type 2), and eutrophic lakes with high cyanobacterial biomass (Type 3). A marked difference in zooplankton size structure was found among these groups. The greatest mean zooplankton size was observed in Type 2 lakes, but zooplankton density was the lowest. Zooplankton abundance was highest in Type 3 lakes and increased with increasing cyanobacterial biomass. Zooplankton mean size was negatively correlated with cyanobacterial biomass. No obvious trends were found in Type 1 lakes. These results were reflected by the normalized biomass size spectrum, which showed a unimodal shape with a peak at medium sizes in Type 2 lakes and a peak at small sizes in Type 3 lakes. These results indicated a relative increase in medium-sized and small-sized species in Types 2 and 3 lakes, respectively. Our results suggested that fish predation might have a negative effect on zooplankton abundance but a positive effect on zooplankton size structure. High cyanobacterial biomass most likely caused a decline in the zooplankton size and encouraged the proliferation of small zooplankton. We suggest that both planktivorous fish and cyanobacteria have substantial effects on the shaping of zooplankton community, particularly in the lakes in the eastern plain along the Yangtze River where aquaculture is widespread and nutrient loading is high.

Zhang, Jing; Xie, Ping; Tao, Min; Guo, Longgen; Chen, Jun; Li, Li; XueZhen Zhang; Zhang, Lu

2013-01-01

300

The impact of fish predation and cyanobacteria on zooplankton size structure in 96 subtropical lakes.  

PubMed

Zooplankton are relatively small in size in the subtropical regions. This characteristic has been attributed to intense predation pressure, high nutrient loading and cyanobacterial biomass. To provide further information on the effect of predation and cyanobacteria on zooplankton size structure, we analyzed data from 96 shallow aquaculture lakes along the Yangtze River. Contrary to former studies, both principal components analysis and multiple regression analysis showed that the mean zooplankton size was positively related to fish yield. The studied lakes were grouped into three types, namely, natural fishing lakes with low nutrient loading (Type1), planktivorous fish-dominated lakes (Type 2), and eutrophic lakes with high cyanobacterial biomass (Type 3). A marked difference in zooplankton size structure was found among these groups. The greatest mean zooplankton size was observed in Type 2 lakes, but zooplankton density was the lowest. Zooplankton abundance was highest in Type 3 lakes and increased with increasing cyanobacterial biomass. Zooplankton mean size was negatively correlated with cyanobacterial biomass. No obvious trends were found in Type 1 lakes. These results were reflected by the normalized biomass size spectrum, which showed a unimodal shape with a peak at medium sizes in Type 2 lakes and a peak at small sizes in Type 3 lakes. These results indicated a relative increase in medium-sized and small-sized species in Types 2 and 3 lakes, respectively. Our results suggested that fish predation might have a negative effect on zooplankton abundance but a positive effect on zooplankton size structure. High cyanobacterial biomass most likely caused a decline in the zooplankton size and encouraged the proliferation of small zooplankton. We suggest that both planktivorous fish and cyanobacteria have substantial effects on the shaping of zooplankton community, particularly in the lakes in the eastern plain along the Yangtze River where aquaculture is widespread and nutrient loading is high. PMID:24124552

Zhang, Jing; Xie, Ping; Tao, Min; Guo, Longgen; Chen, Jun; Li, Li; Xuezhen Zhang; Zhang, Lu

2013-10-04

301

Fossil zooplankton and the historical status of westslope cutthroat trout in a headwater lake of Glacier National Park, Montana  

USGS Publications Warehouse

Surviving pure-strain populations of westslope cutthroat trout Oncorhynchus clarki lewisi in headwater lakes of Glacier National Park could play an important role in the managed recovery of regional cutthroat trout fisheries. However, uncertainty exists about whether native trout could have naturally invaded several park lakes where they now occur. This study used paleolimnological techniques to address the question of whether the population of native trout in Avalanche Lake is indigenous or became established through an undocumented introduction. The validity of using fossil diapause eggs (ephippia) of the fish-sensitive cladocerans Daphnia spp. as indicators for the historical presence of zooplanktivorous fish was tested with a survey of live zooplankton and corresponding surface-sediment fossil assemblages in eight Glacier Park lakes with or without trout. Analysis of a sediment core from Avalanche Lake dated by lead radioisotopes, historical wildfires, and a flood allowed reconstruction of zooplankton dynamics from about 1700 A.D. to the present. Fossil Daphnia ephippia were rare or absent in Avalanche Lake sediments deposited before 1910, suggesting intense zooplanktivory due to sustained presence of an indigenous population of native cutthroat trout. Fossil evidence for larger Daphnia populations in the 1930s and early 1940s revealed a temporary disturbance of the lake's normal food web interactions during which zooplanktivory was significantly reduced. This disturbance may have resulted from a collapse of the native trout population caused indirectly by failed attempts between 1915 and 1943 to stock Avalanche Lake with Yellowstone cutthroat trout O. clarki bouvieri.

Verschuren, D.; Marnell, L. F.

1997-01-01

302

Population resistance to climate change: modelling the effects of low recruitment in open populations  

Microsoft Academic Search

Isolated populations or those at the edge of their distribution are usually more sensitive to changes in the environment, such as climate change. For the barnacle Semibalanus balanoides (L.), one possible effect of climate change is that unpredictable spring weather could lead to the mismatching of larval release with spring phytoplankton bloom, hence reducing the recruitment. In this paper, model

Carl Johan Svensson; Stuart R. Jenkins; Stephen J. Hawkins; Per Åberg

2005-01-01

303

Bifurcation analysis of a population model and the resulting SIS epidemic model with delay  

NASA Astrophysics Data System (ADS)

This paper deals with the model for matured population growth proposed in Cooke et al. [Interaction of matiration delay and nonlinear birth in population and epidemic models, J. Math. Biol. 39 (1999) 332-352] and the resulting SIS epidemic model. The dynamics of these two models are still largely undetermined, and in this paper, we perform some bifurcation analysis to the models. By applying the global bifurcation theory for functional differential equations, we are able to show that the population model allows multiple periodic solutions. For the SIS model, we obtain some local bifurcation results and derive formulas for determining the bifurcation direction and the stability of the bifurcated periodic solution.

Wei, Junjie; Zou, Xingfu

2006-12-01

304

Models and model selection uncertainty in estimating growth rates of endangered freshwater mussel populations  

Microsoft Academic Search

Appropriate inference of population status for endangered species is extremely important. Using a single model for estimating population growth rates is typically inadequate for assessing endangered species because inferences based on only one ''best'' model ignore model uncertainty. In this study, the endangered dromedary pearlymussel (Dromus dro- mas) in the Clinch and Powell rivers of eastern Tennessee, USA, was used

Yan Jiao; Richard Neves; Jess Jones

2008-01-01

305

Multi-population model of a microbial electrolysis cell.  

PubMed

This work presents a multi-population dynamic model of a microbial electrolysis cell (MEC). The model describes the growth and metabolic activity of fermentative, electricigenic, methanogenic acetoclastic, and methanogenic hydrogenophilic microorganisms and is capable of simulating hydrogen production in a MEC fed with complex organic matter, such as wastewater. The model parameters were estimated with the experimental results obtained in continuous flow MECs fed with acetate or synthetic wastewater. Following successful model validation with an independent data set, the model was used to analyze and discuss the influence of applied voltage and organic load on hydrogen production and COD removal. PMID:21534584

Pinto, R P; Srinivasan, B; Escapa, A; Tartakovsky, B

2011-05-02

306

Populations for a divine-based space debris model  

NASA Astrophysics Data System (ADS)

A new analytical tool to calculate flux and spatial density resulting from space debris was developed with the aim to allow fast and accurate analysis for any target orbit and altitudes ranging from LEO to GEO. The model is based on the approach presented by N. Divine in 1993, which was developed for the meteoroid flux analysis. This approach was adapted to the Earth's debris environment, and is implemented in ESA's meteoroid and space debris reference model MASTER'99 as so called 'Standard application'. An extended version of the model called DIADEM, which is restricted to flux and spatial density analysis at high altitudes, includes a debris particle cloud model. This model may be applied to known cloud generation events, e.g. solid rocket motor (SRM) firings. The accuracy of the analysis results of the Divine-based model is essentially depending on the implementation of the underlying debris population. This applies to both the background population and to particle clouds. This paper is intended to describe the adaptation of the MASTER reference population to the needs of the new model, and to give a survey of its cloud modelling capabilities.

Bunte, K. D.; Klinkrad, H.; Drolshagen, G.

2001-10-01

307

The MIUSCAT stellar population models: constraints from optical photometry  

NASA Astrophysics Data System (ADS)

We present the spectral extension of our stellar population synthesis models based on the MILES and CaT empirical stellar spectral libraries. For this purpose we combine these two libraries with the Indo-US to construct composite stellar spectra to feed our models. The spectral energy distributions (SEDs) computed with these models and the originally published models are combined to construct composite SEDs for single-age, single-metallicity stellar populations (SSPs) covering the range ??3465 -- 9469 Å at resolution FWHM =2.51 Å. We also show a comprehensive comparison of the MIUSCAT models with photometric data of globular clusters and early-type galaxies. The models compare remarkably well with the integrated colours of Milky Way globular clusters in the optical range. On the other hand we find that the colour relations of nearby early-type galaxies are still a challenge for present-day stellar population synthesis models. We investigate a number of possible explanations and establish the importance of ?-enhanced models to bring down the discrepancy with observations.

Ricciardelli, E.; Vazdekis, A.; Cenarro, A. J.; Falcón-Barroso, J.

2013-05-01

308

Model estimation of energy flow in Oregon coastal seabird populations  

USGS Publications Warehouse

A computer simulation model was used to explore the patterns and magnitudes of population density changes and population energy demands in Oregon populations of Sooty Shear-waters, Leach?s Storm-Petrels, Brandt?s Cormorants, and Common Murres. The species differ in seasonal distribution and abundance, with shearwaters attaining high densities during their migratory movements through Oregon waters, and murres exhibiting the greatest seasonal stability in population numbers. On a unit area basis, annual energy flow is greatest through murre and cormorant populations. However, because shearwaters occupy a larger area during their transit, they dominate the total energy flow through the four-species seabird ?community.?.....Consumption of various prey types is estimated by coupling model output of energy demands with information on dietary habits. This analysis suggests that murres annually consume nearly twice as many herring as any other prey and consume approximately equal quantities of anchovy, smelt, cod, and rockfish. Cormorants consume a relatively small quantity of bottom-dwelling fish, while stormpetrels take roughly equal quantities of euphausiids and hydrozoans. Anchovies account for 43% of the 62,506 metric tons of prey the four species are estimated to consume annually; 86% of this anchovy consumption is by shearwaters. The consumption of pelagic fishes by these four populations within the neritic zone may represent as much as 22% of the annual production of these fish.

Wiens, J.A.; Scott, J.M.

1976-01-01

309

An inbreeding model of associative overdominance during a population bottleneck.  

PubMed Central

Associative overdominance, the fitness difference between heterozygotes and homozygotes at a neutral locus, is classically described using two categories of models: linkage disequilibrium in small populations or identity disequilibrium in infinite, partially selfing populations. In both cases, only equilibrium situations have been considered. In the present study, associative overdominance is related to the distribution of individual inbreeding levels (i.e., genomic autozygosity). Our model integrates the effects of physical linkage and variation in inbreeding history among individual pedigrees. Hence, linkage and identity disequilibrium, traditionally presented as alternatives, are summarized within a single framework. This allows studying nonequilibrium situations in which both occur simultaneously. The model is applied to the case of an infinite population undergoing a sustained population bottleneck. The effects of bottleneck size, mating system, marker gene diversity, deleterious genomic mutation parameters, and physical linkage are evaluated. Bottlenecks transiently generate much larger associative overdominance than observed in equilibrium finite populations and represent a plausible explanation of empirical results obtained, for instance, in marine species. Moreover, the main origin of associative overdominance is random variation in individual inbreeding whereas physical linkage has little effect.

Bierne, N; Tsitrone, A; David, P

2000-01-01

310

Modelling the effect of conjugate vaccines in pneumococcal disease: Cohort or population models?  

Microsoft Academic Search

Cohort and population models estimate vaccine impact on disease events, and yield different estimates in countries with different demographic compositions. We compared administration of the new 10-valent pneumococcal Haemophilus influenzae–protein D conjugate vaccine (PHiD-CV) with no vaccination in two countries, the United Kingdom (UK) and Mexico, using two modelling strategies: a cohort model and a population model. The cohort model

Baudouin Standaert; Nadia Demarteau; Sandra Talbird; Josephine Mauskopf

2010-01-01

311

Biomass of zooplankton estimated by acoustical sensors in the Arabian sea. Final report  

SciTech Connect

The long term goal of our overall research program is the development of data-based models to predict ecological relationships of zooplankton, phytoplankton and the physical environment in the sea. The overall objective of the work carried out within the scope of this particular contract was to acoustically measure the dynamics of zooplankton and micronekton in the northern Arabian Sea during several seasons. The scientific focus was to examine the impact, if any, of the two annual monsoons that are thought to drive the ecosystem response in the area. This particular project involved the design and construction of two sensors which were then deployed in the Arabian Sea by several of our co-PIVs in the ONR ARI on Forced Upper Ocean Dynamics during the time period in which the JGOFS program also focused their efforts on the northern Arabian Sea. This contract involved only the development, calibration and maintenance of the instrumentation. The data processing, other than that which has been necessary for the purposes of quality assurance, was not induded in our original proposal.

Holliday, D.V.

1996-11-22

312

Phytoplankton, not allochthonous carbon, sustains herbivorous zooplankton production.  

PubMed

Terrestrial organic matter inputs have long been thought to play an important role in aquatic food web dynamics. Results from recent whole lake (13)C addition experiments suggest terrestrial particulate organic carbon (t-POC) inputs account for a disproportionate portion of zooplankton production. For example, several studies concluded that although t-POC only represented approximately 20% of the flux of particulate carbon available to herbivorous zooplankton, this food source accounted for approximately 50% of the C incorporated by zooplankton. We tested the direct dietary impact of t-POC (from the leaves of riparian vegetation) and various phytoplankton on Daphnia magna somatic growth, reproduction, growth efficiency, and lipid composition. By itself, t-POC was a very poor quality resource compared to cryptophytes, diatoms, and chlorophytes, but t-POC had similar food quality compared to cyanobacteria. Small additions of high quality Cryptomonas ozolinii to t-POC-dominated diets greatly increased Daphnia growth and reproduction. When offered alone, t-POC resulted in a Daphnia growth efficiency of 5 +/- 1%, whereas 100% Cryptomonas and Scenedesmus obliquus diets resulted in growth efficiencies of 46 +/- 8% (+/- SD) and 36 +/- 3%, respectively. When offered in a 50:50 mixed diet with Cryptomonas or Scenedesmus, the t-POC fraction resulted in a partial growth efficiency of 22 +/- 9% and 15 +/- 6%, respectively. Daphnia that obtained 80% of their available food from t-POC assimilated 84% of their fatty acids from the phytoplankton component of their diet. Overall, our results suggest Daphnia selectively allocate phytoplankton-derived POC and lipids to enhance somatic growth and reproduction, while t-POC makes a minor contribution to zooplankton production. PMID:19934044

Brett, Michael T; Kainz, Martin J; Taipale, Sami J; Seshan, Hari

2009-11-23

313

Zooplankton grazing on Phaeocystis : a quantitative review and future challenges  

Microsoft Academic Search

The worldwide colony-forming haptophyte phytoplankton Phaeocystis spp. are key organisms in trophic and biogeochemical processes in the ocean. Many organisms from protists to fish ingest\\u000a cells and\\/or colonies of Phaeocystis. Reports on specific mortality of Phaeocystis in natural plankton or mixed prey due to grazing by zooplankton, especially protozooplankton, are still limited. Reported\\u000a feeding rates vary widely for both crustaceans

Jens C. Nejstgaard; Kam W. Tang; Michael Steinke; Jörg Dutz; Marja Koski; Elvire Antajan; Jeremy D. Long

2007-01-01

314

Mesoscale physical variability affects zooplankton production in the Labrador Sea  

Microsoft Academic Search

Surface distribution (0–100m) of zooplankton biomass and specific aminoacyl-tRNA synthetases (AARS) activity, as a proxy of structural growth, were assessed during winter 2002 and spring 2004 in the Labrador Sea. Two fronts formed by strong boundary currents, several anticyclonic eddies and a cyclonic eddy were studied. The spatial contrasts observed in seawater temperature, salinity and fluorescence, associated with those mesoscale

L. Yebra; R. P. Harris; E. J. H. Head; I. Yashayaev; L. R. Harris; A. G. Hirst

2009-01-01

315

Crustacean zooplankton assemblages in freshwaters of tropical Australia  

Microsoft Academic Search

Throughout tropical Australia eulimnetic zooplankton is composed of 7 calanoid copepods, 5 cyclopoid copepods and 12 cladocerans. A further 10 cyclopoids and 9 cladocerans occur as littoral ‘strays’, making 43 species in all. Dominants include Diaptomus lumholtzi, Mesocyclops notius, Thermocyclops decipiens, Diaphanosoma excisum, Ceriodaphnia cornuta, and Moina micrura. Momentary species composition averages 1.0 calanoids, 1.3 cyclopoids and 2.0 cladocerans. These

B. V. Timms; D. W. Morton

1988-01-01

316

The Zooplankton community of Croker Passage, Antarctic Peninsula  

Microsoft Academic Search

Zooplankton species composition, abundance and vertical distribution were investigated in the upper 1000 m of Croker Passage, Antarctic Peninsula during the austral fall (March–April, 1983). 106 species were identified, many being mesopelagic and reported previously from the Southern Ocean. The most numerous species (>1000\\/100 m3) were the copepodsMetridia gerlachei, Microcalanus pygmaeus, Oncaea antarctica andOncaea curvata. Oncaea curvata alone constituted half

T. L. Hopkins

1985-01-01

317

Zooplankton fecal pellets link fossil fuel and phosphate deposits  

USGS Publications Warehouse

Fossil zooplankton fecal pellets found in thinly bedded marine and lacustrine black shales associated with phosphate, oil, and coal deposits, link the deposition of organic matter and biologically associated minerals with planktonic ecosystems. The black shales were probably formed in the anoxic basins of coastal marine waters, inland seas, and rift valley lakes where high productivity was supported by runoff, upwelling, and outwelling. Copyright ?? 1981 AAAS.

Porter, K. G.; Robbins, E. I.

1981-01-01

318

Small-scale pattern of a California current zooplankton assemblage  

Microsoft Academic Search

The small-scale vertical (10's of meters) and horizontal (100's to 1000's of meters) distribution of zooplankton in the California Current near Guadalupe Island, Baja California, Mexico was studied. Vertical distributions were sampled using a vertically-towed Longhurst-Hardy Plankton Recorder (LHPR) which gave a sequence of samples, each integrated over about 5 m, from 250 m to the surface. Because of the

L. R. Haury; Woods Hole

1976-01-01

319

Zooplankton grazing in a Potomac River cyanobacteria bloom  

Microsoft Academic Search

During summer, bloom-forming cyanobacteria, including Anacystis, Aphanizomenon, and Microcystis aeruginosa, dominate tidal-fresh waters of the upper Potomac River estuary with densities exceeding 108 cells l?1. In an attempt to determine the importance of these high cyanobacteria densities to planktonic herbivory in the system, short-term\\u000a grazing experiments were conducted in July and August 1987. Using size-fractionated river phytoplankton assemblages, zooplankton\\u000a grazing

K. G. Sellner; D. C. Brownlee; M. H. Bundy; S. G. Brownlee; K. R. Braun

1993-01-01

320

Zooplankton Avoidance Behavior Following Spray Drift Exposure to Fenpyroximate  

Microsoft Academic Search

A 28-d zooplankton community level study with Fenpyroximate was performed in indoor microcosms of 1 m volume including water and sediment from natural sources. The microcosms were treated by simulating spray-drift of the formulated product. The nominal concentrations (0.1, 0.32, 0.56, 1.0, 3.2, and 10 ? g\\/L) were confirmed by chemical analysis of the application solutions. At a water depth

Christoph Schäfers; Helmut Klöppel; Yoshinori Takahashi

2007-01-01

321

Attachment of Vibrio cholerae serogroup O1 to zooplankton and phytoplankton of Bangladesh waters.  

PubMed Central

Vibrio cholerae serogroup O1, the causative agent of cholera, is capable of surviving in aquatic environments for extended periods and is considered an autochthonous species in estuarine and brackish waters. These environments contain numerous elements that may affect its ecology. The studies reported here examined physical interactions between V. cholerae O1 and natural plankton populations of a geographical region in Bangladesh where cholera is an endemic disease. Results showed that four of five clinical V. cholerae O1 strains and endogenous bacterial flora were attached preferentially to zooplankton molts (exuviae) rather than to whole specimens. One strain attached in approximately equal numbers to both exuviae and whole specimens. V. cholerae O1 also attached to several phytoplankton species. The results show that V. cholerae O1 can bind to diverse plankton species collected from an area where cholera is an endemic disease, with potentially significant effects on its ecology. Images

Tamplin, M L; Gauzens, A L; Huq, A; Sack, D A; Colwell, R R

1990-01-01

322

Stirring effects in models of oceanic plankton populations  

NASA Astrophysics Data System (ADS)

We present an overview and extend previous results on the effects of large scale oceanic transport processes on plankton population dynamics, considering different types of ecosystem models. We find that increasing stirring rate in an environment where the carrying capacity is non-uniformly distributed leads to an overall decrease of the effective carrying capacity of the system. This may lead to sharp regime shifts induced by stirring in systems with multiple steady states. In prey-predator type systems, stirring leads to resonant response of the population dynamics to fluctuations enhancing the spatial variability--patchiness--in a certain range of stirring rates. Oscillatory population models produce strongly heterogeneous patchy distribution of plankton blooms when the stirring is weak, while strong stirring may either synchronise the oscillatory dynamics, when the inhomogeneity is relatively weak, or suppress oscillations completely (oscillator death) by reducing the effective carrying capacity below the bifurcation point.

Neufeld, Zoltan

2012-09-01

323

Shifts in Zooplankton Community Structure: Implications for Food Web Processes in the Upper San Francisco Estuary  

Microsoft Academic Search

Zooplankton are an important trophic link and a key food source for many larval fish species in estuarine ecosystems. The\\u000a present study documents temporal and spatial zooplankton dynamics in Suisun Bay and the Sacramento–San Joaquin Delta—the landward\\u000a portion of the San Francisco Estuary (California, USA)—over a 37-year period (1972–2008). The zooplankton community experienced\\u000a major changes in species composition, largely associated

Monika Winder; Alan D. Jassby

2011-01-01

324

Mercury biomagnification in marine zooplankton food webs in Hudson Bay.  

PubMed

While much research has been carried out on mercury in large marine mammals and associated food webs in northern regions, comparatively less has been conducted on lower trophic levels including zooplankton and the subsequent transfer to predators, which marks the entry of mercury into northern marine food webs. We present here the first database for mercury uptake and transfer exclusively within zooplankton food webs in northern marine waters. We have investigated both total (THg) and monomethylmercury (MMHg) concentrations, and isotopic signatures (?(15)N and ?(13)C) in individual zooplankton taxa collected over a period of eight years (2003-2010) from across Hudson Bay (including Hudson Strait and Foxe Basin) as part of research icebreaker cruises. ?(15)N values ranged from 3.4 to 14.0‰, implying trophic levels ranging from 1 to 4, and THg concentrations ranged from 5 to 242 ng g(-1) dw. Food web linkages were identified within the data set, and mercury biomagnification was evident both with THg and MMHg concentrations increasing from prey to predator, and with trophic magnification factors (TMFs). Total mercury and MMHg transfer in a unique prey-predator linkage (Limacina helicina-Clione limacina) are investigated and discussed with regard to known physiological and biochemical characteristics. The results suggest that exposure to mercury at higher trophic levels including humans can be affected by processes at the bottom of Arctic marine food webs. PMID:23157666

Foster, Karen L; Stern, Gary A; Pazerniuk, Monica A; Hickie, Brendan; Walkusz, Wojciech; Wang, Feiyue; Macdonald, Robie W

2012-11-16

325

Effects of temperature on the metabolic stoichiometry of Arctic zooplankton  

NASA Astrophysics Data System (ADS)

We assessed the relationship between zooplankton metabolism (respiration and inorganic N and P excretion) and "in situ" temperature through a grid of stations representing a range of natural temperature variation during the ATOS-Arctic cruise (July 2007). The objective was to explore not only the direct effects of temperature on zooplankton carbon respiratory losses (hereafter CR) and NH4-N and PO4-P excretion rates (hereafter NE and PE, respectively), but also to investigate whether these metabolic pathways responded similarly to temperature, and so how temperature could affect the stoichiometry of the metabolic products. Metabolic rates, normalised to per unit of zooplankton carbon biomass, increased with increasing temperature following the Arrhenius equation. However, the activation energy differed for the various metabolic processes considered. Respiration, CR, was the metabolic activity least affected by temperature, followed by NE and PE, and as a consequence the values of the CR : NE, CR : PE and NE : PE atomic quotients were inversely related to temperature. The effects of temperature on the stoichiometry of the excreted N and P products would contribute to modifying the nutrient pool available for phytoplankton and induce qualitative and quantitative shifts in the size, community structure and chemical composition of primary producers that could possibly translate to the whole Arctic marine food web.

Alcaraz, M.; Almeda, R.; Saiz, E.; Calbet, A.; Duarte, C. M.; Agustí, S.; Santiago, R.; Alonso, A.

2013-02-01

326

Avoidance of towed nets by zooplankton  

Microsoft Academic Search

Expcrimcnts wcrc condnctcd to dctcrminc the effect of behavior on the accuracy oE sampling populations composed of several spccics of marine copepods and mysids held in a large, cncloscd scawnter pool. Plankton nets having mouth arcas of 1,600, 800, and 400 cm\\

ABRAHAM FLEMINGER; ROBERT I. CLUTTER

1965-01-01

327

Modeling the population lens effect in thermal lens spectrometry.  

PubMed

We report a theoretical model and experimental results for laser-induced lensing in solids. The model distinguishes and quantifies the contributions from population and thermal effects. Laser-induced lensing in ytterbium-doped fluorozirconate glass ZBLAN:Yb(3+) is measured, and the thermal and optical properties obtained from analyzing the data with the proposed model agree well with published values. Photothermal techniques are used extensively for the investigation of laser and laser-cooling materials, and the model developed here enables the interpretation of convoluted laser-induced lensing signals that have contributions from different sources. PMID:23455089

Silva, J R; Malacarne, L C; Baesso, M L; Lima, S M; Andrade, L H C; Jacinto, C; Hehlen, M P; Astrath, N G C

2013-02-15

328

Predicting population dynamics with analytical, simulation and supercomputer models  

SciTech Connect

A set of epizootiological models describing the influence of a microsporidian disease on the population dynamics of an herbivorous insect demonstrate the similarities and differences between the three major approaches now available for ecological modeling. Simulation modeling allows the incorporation of randomness or the timing of discrete events in the temporal dynamics. More complex models incorporating both temporal and spatial dynamics in variable and heterogeneous environments require the use of supercomputers. Under a number of realistic circumstances, the qualitative predictions of the approaches may differ.

Onstad, D.W.

1987-07-01

329

Considerations on the crystallization modeling: Population balance solution  

Microsoft Academic Search

In crystallization processes, the need to improve the product quality and to minimize production cost requires understanding and optimization on how to obtain an appropriate particle-size distribution. In order to achieve this goal, a model of the process is necessary and the distribution of particles must be represented, which is made through the population balance. This latter constitutes a strongly

Caliane Bastos Borba Costa; Maria Regina Wolf Maciel; Rubens Maciel Filho

2007-01-01

330

Population modeling of the emergence and development of scientific fields  

Microsoft Academic Search

We analyze the temporal evolution of emerging fields within several scientific disciplines in terms of numbers of authors and publications. From bibliographic searches we construct databases of authors, papers, and their dates of publication. We show that the temporal development of each field, while different in detail, is well described by population contagion models, suitably adapted from epidemiology to reflect

Lu'is M. A. Bettencourt; David I. Kaiser; Jasleen Kaur; Carlos Castillo-Chavez; David E. Wojick

2008-01-01

331

GENERAL: Exact Solutions of Fractional-Order Biological Population Model  

NASA Astrophysics Data System (ADS)

In this paper, the Adomian's decomposition method (ADM) is presented for finding the exact solutions of a more general biological population models. A new solution is constructed in power series. The fractional derivatives are described in the Caputo sense. To illustrate the reliability of the method, some examples are provided.

El-Sayed, A. M. A.; Rida, S. Z.; Arafa, A. A. M.

2009-12-01

332

Key parameters for modeling information diffusion in populations  

Microsoft Academic Search

Modeling and simulation can be an important tool in helping develop techniques to better communicate safety-critical information for disaster preparation and recovery. However, these tools are only moderately useful if they do not capture both the social component (how information diffuses in a population through communication between individuals) and the cognitive component (how individuals integrate information and change behavior). The

Kiran Lakkaraju; Ann Elizabeth Speed

2010-01-01

333

Population clinical pharmacology of children: modelling covariate effects  

Microsoft Academic Search

Introduction  Population modelling using mixed effects models provides a means to study variability in paediatric drug responses among individuals representative of those in whom the drug will be used clinically.Discussions  Explanatory covariates explain the predictable part of the between-individual variability. Growth and development are two major aspects of children not seen in adults. These aspects can be investigated by using size and

Brian J. Anderson; Karel Allegaert; Nicholas H. G. Holford

2006-01-01

334

Parsimonious snow model explains reindeer population dynamics and ranging behavior  

NASA Astrophysics Data System (ADS)

Winter snow is a key factor affecting polar ecosystems. One example is the strong negative correlation of winter precipitation with fluctuations in population in some high-arctic animal populations. Ice layers within and at the base of the snowpack have particularly deleterious effects on such populations. Svalbard reindeer have small home ranges and are vulnerable to local "locked pasture" events due to ground-ice formation. When pastures are locked, reindeer are faced with the decision of staying, living off a diminishing fat store, or trying to escape beyond the unknown spatial borders of the ice. Both strategies may inhibit reproduction and increase mortality, leading to population declines. Here we assess the impact of winter snow and ice on the population dynamics of an isolated herd of Svalbard reindeer near Ny-Ålesund, monitored annually since 1978, with a retrospective analysis of the winter snowpack. Because there are no long-term observational records of snow or snow properties, such as ice layers, we must recourse to snowpack modeling. A parsimonious model of snow and ground-ice thickness is driven with daily temperature and precipitation data collected at a nearby weather station. The model uses the degree-day concept and has three adjustable parameters which are tuned to correlate model snow and ground-ice thicknesses to the limited observations available: April snow accumulation measurements on two local glaciers, and a limited number of ground-ice observations made in recent years. Parameter values used are comparable to those reported elsewhere. We find that modeled mean winter ground-ice thickness explains a significant percentage of the observed variance in reindeer population growth rate. Adding other explanatory parameters, such as modeled mean winter snowpack thickness or previous years' population size does not significanly improve the relation. Furthermore, positioning data from a small subset of reindeer show that model icing events are highly correlated to an immediate increase in range displacement between 5-day observations, suggesting that Svalbard reindeer use space opportunistically in winter, a behavioral trait that may buffer some of the negative effects of the expected climate change in the Arctic.

Kohler, J.; Aanes, R.; Hansen, B. B.; Loe, L.; Severinsen, T.; Stien, A.

2008-12-01

335

Yonsei Evolutionary Population Synthesis (YEPS) Model. I. Spectroscopic Evolution of Simple Stellar Populations  

NASA Astrophysics Data System (ADS)

We present a series of papers on the 2012 version of the Yonsei Evolutionary Population Synthesis (YEPS) model, which was constructed based on over 20 years of research. This first paper delineates the spectroscopic aspect of integrated light from stellar populations older than 1 Gyr. The standard YEPS is based on the most up-to-date Yonsei-Yale stellar evolutionary tracks and BaSel 3.1 flux libraries, and provides absorption line indices of the Lick/IDS system and high-order Balmer lines for simple stellar populations as functions of stellar parameters, such as metallicity, age, and ?-element mixture. Special care has been taken to incorporate a systematic contribution from horizontal-branch (HB) stars, which alters the temperature-sensitive Balmer lines significantly, resulting in up to a 5 Gyr difference in the age estimation of old, metal-poor stellar populations. We also find that HBs exert an appreciable effect not only on the Balmer lines but also on the metallicity-sensitive lines, including the magnesium index. This is critical in explaining the intriguing bimodality found in index distributions of globular clusters in massive galaxies and to accurately derive spectroscopic metallicities from various indices. A full set of the spectroscopic and photometric YEPS model data of the entire parameter space is currently downloadable at http://web.yonsei.ac.kr/cosmic/data/YEPS.htm.

Chung, Chul; Yoon, Suk-Jin; Lee, Sang-Yoon; Lee, Young-Wook

2013-01-01

336

Selenium in San Francisco Bay zooplankton: Potential effects of hydrodynamics and food web interactions  

USGS Publications Warehouse

The potential toxicity of elevated selenium (Se) concentrations in aquatic ecosystems has stimulated efforts to measure Se concentrations in benthos, nekton, and waterfowl in San Francisco Bay (SF Bay). In September 1998, we initiated a 14 mo field study to determine the concentration of Se in SF Bay zooplankton, which play a major role in the Bay food web, but which have not previously been studied with respect to Se. Monthly vertical plankton tows were collected at several stations throughout SF Bay, and zooplankton were separated into two operationally defined size classes for Se analyses: 73-2,000 ??m, and ???2,000 ??m. Selenium values ranged 1.02-6.07 ??g Se g-1 dry weight. No spatial differences in zooplankton Se concentrations were found. However, there were inter- and intra-annual differences. Zooplankton Se concentrations were enriched in the North Bay in Fall 1999 when compared to other seasons and locations within and outside SF Bay. The abundance and biovolume of the zooplankton community varied spatially between stations, but not seasonally within each station. Smaller herbivorous-omnivorous zooplankton had higher Se concentrations than larger omnivorous-carnivorous zooplankton. Selenium concentrations in zooplankton were negatively correlated with the proportion of total copepod biovolume comprising the large carnivorous copepod Tortanus dextrilobatus, but positively correlated with the proportion of copepod biovolume comprising smaller copepods of the family Oithonidae, suggesting an important role of trophic level and size in regulating zooplankton Se concentrations.

Purkerson, D. G.; Doblin, M. A.; Bollens, S. M.; Luoma, S. N.; Cutter, G. A.

2003-01-01

337

A frictional population model of seismicity rate change  

USGS Publications Warehouse

We study models of seismicity rate changes caused by the application of a static stress perturbation to a population of faults and discuss our results with respect to the model proposed by Dieterich (1994). These models assume distribution of nucleation sites (e.g., faults) obeying rate-state frictional relations that fail at constant rate under tectonic loading alone, and predicts a positive static stress step at time to will cause an immediate increased seismicity rate that decays according to Omori's law. We show one way in which the Dieterich model may be constructed from simple general idead, illustratted using numerically computed synthetic seismicity and mathematical formulation. We show that seismicity rate change predicted by these models (1) depend on the particular relationship between the clock-advanced failure and fault maturity, (2) are largest for the faults closest to failure at to, (3) depend strongly on which state evolution law faults obey, and (4) are insensitive to some types of population hetrogeneity. We also find that if individual faults fail repeatedly and populations are finite, at timescales much longer than typical aftershock durations, quiescence follows at seismicity rate increase regardless of the specific frictional relations. For the examined models the quiescence duration is comparable to the ratio of stress change to stressing rate ????/??,which occurs after a time comparable to the average recurrence interval of the individual faults in the population and repeats in the absence of any new load may pertubations; this simple model may partly explain observations of repeated clustering of earthquakes. Copyright 2005 by the American Geophysical Union.

Gomberg, J.; Reasenberg, P.; Cocco, M.; Belardinelli, M. E.

2005-01-01

338

Modeling oyster growth rate by coupling oyster population and hydrodynamic models for Apalachicola Bay, Florida, USA  

Microsoft Academic Search

The eastern oyster (Crassostrea virginica) plays an important role both ecologically and economically in Apalachicola Bay, Florida. Oyster population features such as population size, age structure, spawning, growth, and reproduction are closely related to bay salinity, which is often affected by freshwater flows from the Apalachicola River. Existing modeling approaches have used statistical models to examine the effects of changing

Hongqing Wang; Wenrui Huang; Mark A. Harwell; Lee Edmiston; Elijah Johnson; Ping Hsieh; Katherine Milla; John Christensen; Jessica Stewart; Xiaohai Liu

2008-01-01

339

Stable carbon isotopes of zooplankton lipid components as a tool to differentiate between pelagic and ice algae as a food source for zooplankton in the Arctic Ocean  

NASA Astrophysics Data System (ADS)

Every summer in the Arctic, the ice cover melts and releases sea-ice algae into the surrounding waters. How important are these algae, consisting mostly of diatoms, as a major food source for zooplankton and higher trophic levels? The answer to this question is timely, given predictions for the loss of summer sea ice cover this century. We are investigating the use of compound specific carbon isotopes as a tool to differentiate between lipids found in zooplankton which feed on diatoms living in the open ocean and zooplankton which feed on diatoms derived from the ice. To this effect we analyse the carbon isotopic signature of the major fatty acids and alcohols and that of the major sterols collected during the Arctic ICE CHASER expedition aboard the RRV James Clark Ross in 2008. Twenty three zooplankton samples comprised of 11 different species were collected in four different depth intervals at three different sites around Svalbard. The sites had variable ice cover, from open water to solid ice. We analysed the lipid composition of the zooplankton samples with special emphasis on the fatty acids and fatty alcohols bound as esters. Esters are produced by zooplankton to function as an energy reservoir. Initial results such as the occurrence of Brassicasterol, 24 methylencholest 5 en-3?-ol and Desmosterol, high amounts of the C20:5?3 fatty acid and high C16:1?7/C16:0-fatty acid ratios suggest that diatoms are an important part of the zooplankton diet.

Bendle, J. A.; Moossen, H.; Jamieson, R.; Wold, A.; Falk-Peterson, S.

2009-12-01

340

Exact Solution of Population Redistributions in a Migration Model  

NASA Astrophysics Data System (ADS)

We study a migration model, in which individuals migrate from one community to another. The choices of the source community i and the destination one j are proportional to some power of the population of i (k? i) and j (k? j), respectively. Both analytical calculation and numerical simulation show that the population distribution of communities in stationary states is determined by the parameters ? and ?. The distribution is widely homogeneous with a characteristic size if ? > ?. Whereas, for ? < ?, the distribution is highly heterogeneous with the emergence of condensing phenomenon. Between the two regimes, ? = ?, the distribution gradually shifts from the nonmonotonous (? < 0) to scale-free (? > 0).

Wang, Xue-Wen; Zhang, Li-Jie; Yang, Guo-Hong; Xu, Xin-Jian

2013-10-01

341

Inbreeding Estimation from Population Data: Models, Procedures and Implications  

PubMed Central

Four different estimation procedures for models of population structure are compared. The parameters of the models are shown to be equivalent and, in most cases, easily expressed in terms of the parameters Wright calls "F-statistics." We have estimated the parameters of each of these models with data on nine codominant allele pairs in 47 Yanomama villages, and we find that the different estimators for a given parameter all yield more or less equivalent results. F-statistics are often equated to inbreeding coefficients that are defined as the probability of identity by descent from alleles taken to be unique in some founding population. However, we are led to infer from computer simulation and general historical considerations that all estimates from genotype frequencies greatly underestimate the inbreeding coefficient for alleles in the founding population of American Indians in the western hemisphere. We surmise that in the highly subdivided tribal populations which prevailed until the recent advent of civilization, the probability of identity by descent for homologous alleles was roughly 0.5. We consider some consequences of working with the customary, much lower, estimates—0.005 to 0.01—if, on the time scale of human evolution, these represent only a very recent departure from the inbreeding intensity that prevailed before civilization.

Spielman, Richard S.; Neel, James V.; Li, Francis H. F.

1977-01-01

342

Stochastic population oscillations in spatial predator-prey models  

NASA Astrophysics Data System (ADS)

It is well-established that including spatial structure and stochastic noise in models for predator-prey interactions invalidates the classical deterministic Lotka-Volterra picture of neutral population cycles. In contrast, stochastic models yield long-lived, but ultimately decaying erratic population oscillations, which can be understood through a resonant amplification mechanism for density fluctuations. In Monte Carlo simulations of spatial stochastic predator-prey systems, one observes striking complex spatio-temporal structures. These spreading activity fronts induce persistent correlations between predators and prey. In the presence of local particle density restrictions (finite prey carrying capacity), there exists an extinction threshold for the predator population. The accompanying continuous non-equilibrium phase transition is governed by the directed-percolation universality class. We employ field-theoretic methods based on the Doi-Peliti representation of the master equation for stochastic particle interaction models to (i) map the ensuing action in the vicinity of the absorbing state phase transition to Reggeon field theory, and (ii) to quantitatively address fluctuation-induced renormalizations of the population oscillation frequency, damping, and diffusion coefficients in the species coexistence phase.

Täuber, Uwe C.

2011-09-01

343

Stochastic population oscillations in spatial predator-prey models  

NASA Astrophysics Data System (ADS)

It is well-established that including spatial structure and stochastic noise in models for predator-prey interactions invalidates the classical deterministic Lotka-Volterra picture of neutral population cycles. In contrast, stochastic models yield long-lived, but ultimately decaying erratic population oscillations, which can be understood through a resonant amplification mechanism for density fluctuations. In Monte Carlo simulations of spatial stochastic predator-prey systems, one observes striking complex spatio-temporal structures. These spreading activity fronts induce persistent correlations between predators and prey. In the presence of local particle density restrictions (finite prey carrying capacity), there exists an extinction threshold for the predator population. The accompanying continuous non-equilibrium phase transition is governed by the directed-percolation universality class. We employ field-theoretic methods based on the Doi-Peliti representation of the master equation for stochastic particle interaction models to (i) map the ensuing action in the vicinity of the absorbing state phase transition to Reggeon field theory, and (ii) to quantitatively address fluctuation-induced renormalizations of the population oscillation frequency, damping, and diffusion coefficients in the species coexistence phase. [See Preprint arXiv:1105.4242, and further refs. therein.

Tauber, Uwe C.

2011-10-01

344

Interacting planetary nebulae. II. Galactic population and interaction models  

NASA Astrophysics Data System (ADS)

In the present paper, we discuss the classification of planetary nebulae that show interaction with the interstellar medium in terms of Galactic population. Furthermore, we investigate the case of interaction of each object in the framework of the isothermal and adiabatic shock models and we derive the mean critical, leading, and stopping densities of the nebulae located in the Galactic thin and thick disks. A sample of 34 objects with available proper motions, radial velocities, and reliable distances in the literature was used for these purposes. The results show that 16 and 10 objects are classified as Galactic thin-disk and thick-disk populations, respectively. Seven objects are classified as probable thin-disk populations, and one as a probable thick-disk population. The flow and cooling time of the post-shock nebular gas are derived and the cooling/flow time ratio shows a linear correlation versus the Galactic height of the interacting planetary nebulae. The results reveal that there is a tendency for the interacting planetary nebulae belonging to the thin disk to follow an isothermal shock model, whilst those belonging to the thick disk to follow an adiabatic shock model.

Ali, A.; Ismail, H. A.; Snaid, S.; Sabin, L.

2013-10-01

345

Learning stable, regularised latent models of neural population dynamics.  

PubMed

Ongoing advances in experimental technique are making commonplace simultaneous recordings of the activity of tens to hundreds of cortical neurons at high temporal resolution. Latent population models, including Gaussian-process factor analysis and hidden linear dynamical system (LDS) models, have proven effective at capturing the statistical structure of such data sets. They can be estimated efficiently, yield useful visualisations of population activity, and are also integral building-blocks of decoding algorithms for brain-machine interfaces (BMI). One practical challenge, particularly to LDS models, is that when parameters are learned using realistic volumes of data the resulting models often fail to reflect the true temporal continuity of the dynamics; and indeed may describe a biologically-implausible unstable population dynamic that is, it may predict neural activity that grows without bound. We propose a method for learning LDS models based on expectation maximisation that constrains parameters to yield stable systems and at the same time promotes capture of temporal structure by appropriate regularisation. We show that when only little training data is available our method yields LDS parameter estimates which provide a substantially better statistical description of the data than alternatives, whilst guaranteeing stable dynamics. We demonstrate our methods using both synthetic data and extracellular multi-electrode recordings from motor cortex. PMID:22663075

Buesing, Lars; Macke, Jakob H; Sahani, Maneesh

2012-01-01

346

Modeling spatiotemporal dynamics of vole populations in Europe and America.  

PubMed

The mathematical models proposed and studied in the present paper provide a unified framework to understand complex dynamical patterns in vole populations in Europe and North America. We have extended the well-known model provided by Hanski and Turchin by incorporating the diffusion term and spatial heterogeneity and performed several mathematical and numerical analyses to explore the dynamics in space and time of the model. These models successfully predicted the observed rodent dynamics in these regions. An attempt has been made to bridge the gap between the field and theoretical studies carried out by Turchin and Hanski (1997) and Turchin and Ellner (2000). Simulation experiments, mainly two-dimensional parameter scans, show the importance of spatial heterogeneity in order to understand the poorly understood fluctuations in population densities of voles in Fennoscandia and Northern America. This study shed new light upon the dynamics of voles in these regions. The nonlinear analysis of vole data suggests that the dynamical shift is from stability to chaos. Diffusion driven model systems predict a new type of dynamics not yet observed in the field studies of vole populations carried out so far. This has been termed as chaotic in time and regular in space (CTRS). We observed CTRS dynamics in several simulation experiments. This directs us to expect that dynamics of this animal would be de-correlated in time and simultaneously mass extinctions might be possible at many spatial locations. PMID:19861132

Upadhyay, Ranjit Kumar; Kumari, Nitu; Rai, Vikas

2009-10-25

347

Two-population dynamics in a growing network model  

NASA Astrophysics Data System (ADS)

We introduce a growing network evolution model with nodal attributes. The model describes the interactions between potentially violent V and non-violent N agents who have different affinities in establishing connections within their own population versus between the populations. The model is able to generate all stable triads observed in real social systems. In the framework of rate equations theory, we employ the mean-field approximation to derive analytical expressions of the degree distribution and the local clustering coefficient for each type of nodes. Analytical derivations agree well with numerical simulation results. The assortativity of the potentially violent network qualitatively resembles the connectivity pattern in terrorist networks that was recently reported. The assortativity of the network driven by aggression shows clearly different behavior than the assortativity of the networks with connections of non-aggressive nature in agreement with recent empirical results of an online social system.

Ivanova, Kristinka; Iordanov, Ivan

2012-02-01

348

On the Cumulants of Population Size for the Stochastic Power Law Logistic Model  

Microsoft Academic Search

The deterministic power law logistic model is used to describe density-dependent population growth in cases where the ordinary logistic model is insufficient. This paper investigates an analogous stochastic power law logistic model. The exact (unconditional) population size distributions and the cumulant functions for this stochastic model are intractable for large population sizes. Approximating cumulant functions are derived for populations of

James H Matis; Thomas R Kiffe; P. R. Parthasarathy

1998-01-01

349

Individual-based model of young-of-the-year striped bass population dynamics. II. Factors affecting recruitment in the Potomac River, Maryland  

SciTech Connect

An individual-based model of the population dynamics of young-of-the-year striped bass Morone saxatilis in the Potomac River, Maryland, was used to test the hypothesis that historically high recruitment variability can be explained by changes in environmental and biological factors that result in relatively small changes in growth and mortality rates of striped bass larvae. The four factors examined were (1) size distribution of female parents, (2) zooplankton prey density during the development of striped bass larvae, (3) density of completing larval white perch M. americana, and (4) temperature during larval development. Simulation results suggest that variations in female size and in prey for larvae alone could cause 10-fold variability in recruitment. But no single factor alone caused changes in vital rates of age-0 fish that could account for the 145-fold variability in the Potomac River index of juvenile recruitment. However, combined positive or negative effects of two or more factors resulted in more than a 150-fold simulated recruitment variability, suggesting that combinations of factors can account for the high observed annual variability in striped bass recruitment success. Higher cumulative mortality of feeding larvae and younger life stages than of juveniles was common to all simulations. supporting the contention that striped bass year-class strength is determined prior to metamorphosis. 76 refs., 7 figs., 4 tabs.

Cowan, J.H. (Univ. of South Alabama, Mobile, AL (United States)); Rose, K.A. (Oak Ridge National Lab., TN (United States)); Rutherford, E.S.; Houde, E.D. (Univ. of Maryland System, Solomons, MD (United States))

1993-05-01

350

CHIMP: A SIMPLE POPULATION MODEL FOR USE IN INTEGRATED ASSESSMENT OF GLOBAL ENVIRONMENTAL CHANGE  

Microsoft Academic Search

We present the Canberra-Hamburg Integrated Model for Population (CHIMP), a new global population model for long-term projections. Distinguishing features of this model, compared to other model for secular population projections, are that (a) mortality, fertility, and migration are partly driven by per capita income; (b) large parts of the model have been estimated rather than calibrated; and (c) the model

Brian S. Fisher; Guy Jakeman; Hom M. Pant; Malte Schwoon; Richard S.J. Tol

2005-01-01

351

The validity of bioelectrical impedance models in clinical populations.  

PubMed

Bioelectrical impedance analysis (BIA) is the most commonly used body composition technique in published studies. Herein we review the theory and assumptions underlying the various BIA and bioelectrical impedance spectroscopy (BIS) models, because these assumptions may be invalidated in clinical populations. Single-frequency serial BIA and discrete multifrequency BIA may be of limited validity in populations other than healthy, young, euvolemic adults. Both models inaccurately predict total body water (TBW) and extracellular water (ECW) in populations with changes in trunk geometry or fluid compartmentalization, especially at the level of the individual. Single-frequency parallel BIA may predict body composition with greater accuracy than the serial model. Hand-to-hand and leg-to-leg BIA models do not accurately predict percent fat mass. BIS may predict ECW, but not TBW, more accurately than single-frequency BIA. Segmental BIS appears to be sensitive to fluid accumulation in the trunk. In general, bioelectrical impedance technology may be acceptable for determining body composition of groups and for monitoring changes in body composition within individuals over time. Use of the technology to make single measurements in individual patients, however, is not recommended. This has implications in clinical settings, in which measurement of individual patients is important. PMID:16215137

Buchholz, Andrea C; Bartok, Cynthia; Schoeller, Dale A

2004-10-01

352

Using stage-based system dynamics modeling for demographic management of captive populations  

Microsoft Academic Search

Management of captive populations relies on a complex synthesis of genetic and demographic analyses to guide populations toward sustainability. Demographic analyses of captive populations currently utilize age-based matrix projections to predict a population's trajectory. An alternate approach is to use a stage-based, system dynamics model for captive systems. Such models can more easily incorporate complex captive systems in which population

Lisa J. Faust; Steven D. Thompson; Joanne M. Earnhardt; Ellen Brown; Sadie Ryan; Michelle Sherman; Meghan Yurenka

2003-01-01

353

Effects of stochastic population fluctuations in two models of biological macroevolution  

Microsoft Academic Search

Two mathematical models of macroevolution are studied. These models have population dynamics at the species level, and mutations and extinction of species are also included. The population dynamics are updated by difference equations with stochastic noise terms that characterize population fluctuations. The effects of the stochastic population fluctuations on diversity and total population sizes on evolutionary time scales are studied.

Yohsuke Murase; Takashi Shimada; Nobuyasu Ito; Per Arne Rikvold

2008-01-01

354

Effects of stochastic population fluctuations in two models of biological macroevolution  

Microsoft Academic Search

Two mathematical models of macroevolution are studied. These models have population dynamics at the species level, and mutations and extinction of species are also included. The population dynamics are updated by difference equations with stochastic noise terms that characterize population fluctuations. The effects of the stochastic population fluctuations on diversity and total population sizes on evolutionary time scales are studied.

Yohsuke Murase; Takashi Shimada; Nobuyasu Ito; Per Arne Rikvold

2010-01-01

355

Spatial and Temporal Variability of Zooplankton Thin Layers: The Effects of Composition and Orientation on Acoustic Detection of Layers.  

National Technical Information Service (NTIS)

Our primary long-term objective is to better understand the physical and biological mechanisms of formation and maintenance of thin layers of zooplankton. Because zooplankton can be strong sound scatterers, acoustic instruments are effective at detecting ...

A. Lavery C. Ashjian D. Fratantoni M. Sutor P. Wiebe

2006-01-01

356

Spatial and Temporal Variability of Zooplankton Thin Layers: The Effects of Composition and Orientation on Acoustic Detection of Layers.  

National Technical Information Service (NTIS)

Our primary long-term objective is to better understand the physical and biological mechanisms of formation and maintenance of thin layers of zooplankton. Because zooplankton can be strong sound scatterers, acoustic instruments are effective at detecting ...

A. Lavery C. Ashjian D. Fratantoni M. Sutor P. Wiebe

2008-01-01

357

Spatial and Temporal Variability of Zooplankton Thin Layers: The Effects of Composition and Orientation on Acoustic Detection of Layers.  

National Technical Information Service (NTIS)

Our primary long-term objective is to better understand the physical and biological mechanisms of formation and maintenance of thin layers of zooplankton. Because zooplankton can be strong sound scatterers, acoustic instruments are effective at detecting ...

A. Lavery C. Ashijian D. Fratantoni M. Sutor P. Wiebe

2007-01-01

358

Numerical behavior of a multiscale aggregation model—coupling population balances and discrete element models  

Microsoft Academic Search

The aggregation-rate kernel of shear-induced aggregation introduced by Smoluchowski (1917) is accurately reproduced by a discrete element model to investigate the behavior of a multiscale approach that couples discrete element simulations concurrently to a population balance model. The analyzed model comprises nucleation, growth and aggregation. From the analysis of the discrete element model an estimation for the coefficient of variation

Alexander Reinhold; Heiko Briesen

359

Matching Stellar Population Models to Bulge Globular Clusters.  

NASA Astrophysics Data System (ADS)

We compare observed color-magnitude diagrams (CMDs) of the three metal-rich bulge globular clusters NGC 6553, NGC 6528 and Terzan 5, and integrated spectral energy distributions (SEDs) of NGC 6528 and 47 Tuc, to theoretical isochrones and model SEDs computed with the code of Bruzual & Charlot (1997, hereafter BC97). The BC97 models provide the evolution in time of the spectrophotometric properties of simple stellar populations (SSPs) for a wide range of stellar metallicity. These models allow us to compare predictions based on different sets of evolutionary tracks and various choices of the stellar spectral libraries with observational data. We conclude that: (a) At least for solar metallicity models, the semi-empirical flux corrections applied by Lejeune et al. (1997a,b) to available grids of synthetic stellar spectra improve the agreement between population model predictions and observations. (b) The adopted reddening and distance moduli for the three clusters seem well determined, since the theoretical isochrones fit quite well the observed CMDs. (c) The overall metallicity of these clusters is close to solar. (d) Based on our CMD and SED models we estimate that the ages of NGC 6553 and NGC 6528 must be ~ 12 +/- 2 Gyr. These are the only two clusters in our sample with main sequence photometry. From the UV-optical SED of 47-Tuc we estimate an age of ~ 14 +/- 2 Gyr.

Bruzual, G.; Barbuy, B.; Ortolani, S.; Bica, E.; Cuisinier, F.; Lejeune, T.; Schiavon, R. P.

1997-10-01

360

Agents in GIS environment - Modeling Urban Population Distribution  

Microsoft Academic Search

The recent intensive developments of multi-agent socio-economic simulations still lack real- world examples. The purpose of this paper is to develop spatially explicit model of residen- tial dynamics in urban space, which accounts for the infrastructure of a specific city and is aimed at comprehending and forecasting its population dynamics. The agent-based simula- tion of the residential distribution dynamics of

Itzhak Benenson; Itzhak Omer; Erez Hatna

361

Homotopy Analysis Method for Solving Biological Population Model  

NASA Astrophysics Data System (ADS)

In this paper, the homotopy analysis method (HAM) is applied to solve generalized biological population models. The fractional derivatives are described by Caputo's sense. The method introduces a significant improvement in this field over existing techniques. Results obtained using the scheme presented here agree well with the analytical solutions and the numerical results presented in Ref. [6]. However, the fundamental solutions of these equations still exhibit useful scaling properties that make them attractive for applications.

A. A. M., Arafa; S. Z., Rida; H., Mohamed

2011-11-01

362

Impact of Channelization on Oyster Production: A Hydrodynamic-Oyster Population Model for Galveston Bay, Texas  

Microsoft Academic Search

A hydrodynamic-oyster population dynamics model was developed to assess the effect of a change in ship channel configuration under different freshwater inflow regimes and different future hydrologies on oyster (Crassostrea virginica) populations in Galveston Bay, Texas. The population dynamics model includes the effects of environmental conditions, predators, and the oyster parasite Perkinsus marinus on oyster populations. The hydrodynamic model includes

John M. Klinck; Eileen E. Hofmann; Eric N. Powell; Margaret M. Dekshenieks

2002-01-01

363

Impact of channelization on oyster production: a hydrodynamic-oyster population model for Galveston Bay, Texas  

Microsoft Academic Search

A hydrodynamic-oyster population dynamics model was developed to assess the effect of a change in ship channel configuration under different freshwater inflow regimes and different future hydrologies on oyster (Crassostrea virginica) populations in Galveston Bay, Texas. The population dynamics model includes the effects of environmental conditions, predators, and the oyster parasite Perkinsus marinus on oyster populations. The hydrodynamic model includes

John M. Klinck; Eileen E. Hofmann; N. Powellb; Margaret M. Dekshenieks

2002-01-01

364

A Stochastic Super-Exponential Growth Model for Population Dynamics  

NASA Astrophysics Data System (ADS)

A super-exponential growth model with environmental noise has been studied analytically. Super-exponential growth rate is a property of dynamical systems exhibiting endogenous nonlinear positive feedback, i.e., of self-reinforcing systems. Environmental noise acts on the growth rate multiplicatively and is assumed to be Gaussian white noise in the Stratonovich interpretation. An analysis of the stochastic super-exponential growth model with derivations of exact analytical formulae for the conditional probability density and the mean value of the population abundance are presented. Interpretations and various applications of the results are discussed.

Avila, P.; Rekker, A.

2010-11-01

365

CHIMP: A simple population model for use in integrated assessment of global environmental change  

Microsoft Academic Search

We present the Canberra-Hamburg Integrated Model for Population (CHIMP), a new global population model for long-term projections. Dis- tinguishing features of this model, compared to other models for secular population projections, are that (a) mortality, fertility, and migration are partly driven by per capita income; (b) large parts of the model have been estimated rather than calibrated; and (c) the

Brian S. Fisher; Guy Jakeman; Malte Schwoon

2006-01-01

366

Zooplankton anomalies in the California Current system before and during the warm ocean conditions of 2005  

Microsoft Academic Search

Zooplankton in the California Current had large anomalies in biomass and composition in 2005. The zone most strongly affected extended from northern California to southern British Columbia, where zooplankton biomass was low from spring through autumn, community composition showed reduced dominance by northern origin taxa, and life cycles of some species shifted to earlier in the year. Although similar anomalies

D. L. Mackas; W. T. Peterson; M. D. Ohman; B. E. Lavaniegos

2006-01-01

367

A review of zooplankton investigations of the Black Sea over the last decade  

Microsoft Academic Search

Investigations performed in the last decade indicate that there have been important changes in the zooplankton composition and structure in the Black Sea. However, contrasting events taking place in different regions of the Black Sea indicate a non-uniform structure of its ecosystem.Several fodder zooplankton species have either disappeared from or substantially decreased in number at different sampling sites of the

Ahmet E. Kideys; Alexander V. Kovalev; Gregory Shulman; Anna Gordina; Ferit Bingel

2000-01-01

368

Metabolic rates of epipelagic marine zooplankton as a function of body mass and temperature  

Microsoft Academic Search

The metabolic rates (oxygen uptake, ammonia excretion, phosphate excretion) of epipelagic marine zooplankton have been expressed as a function of body mass (dry, carbon, nitrogen and phosphorus weights) and habitat temperature, using the multiple-regression method. Zooplankton data used for this analysis are from phylogenetically mixed groups (56 to 143 species, representing 7 to 8 phyla, body mass range: 6 orders

T. Ikeda

1985-01-01

369

Fish larvae – zooplankton relationships in microcosm simulations of earthen nursery ponds. I. Freshwater system  

Microsoft Academic Search

To address the commercial nurseries problem of obtaining enough zooplankton of adequate species composition and size when fish larvae start to feed, a simulation of the effects of predation intensity on zooplankton composition in freshwater nursery ponds was carried out in an experimental system of twelve 130-liter containers. Treatments consisted of two densities (1 or 2 larvae l?1) of common carp

Ana Milstein; Arie Valdenberg; Sheenan Harpaz

2006-01-01

370

Fish larvae: zooplankton relationships in microcosm simulations of earthen nursery ponds. II. brackish water system  

Microsoft Academic Search

A simulation of the effects of predation intensity on zooplankton composition in brackish water nursery ponds was carried out in order to address the problem that commercial fish nurseries encounter in obtaining enough zooplankton of adequate species composition and size when fish larvae start to feed. The experimental system consisted of twelve 130 l containers with treatments of four densities (0,

Ana Milstein; Arie Valdenberg; Sheenan Harpaz

2006-01-01

371

CONSTANT, NOCTURNAL OR NO AERATION: EFFECTS ON WATER QUALITY AND ZOOPLANKTON IN HEAVILY FERTILIZED NURSERY PONDS.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Sunshine bass fingerling production depends upon an initial high concentration of rotifers followed by high densities in crustacean zooplankton in culture ponds. Increased fertilization promotes increased amounts of zooplankton but often causes poor water quality which aeration may alleviate. The e...

372

Sonication of bacteria, phytoplankton and zooplankton: Application to treatment of ballast water  

Microsoft Academic Search

We investigated the effect of high power ultrasound, at a frequency of 19kHz, on the survival of bacteria, phytoplankton and zooplankton, in order to obtain estimates of effective exposure times and energy densities that could be applied to design of ultrasonic treatment systems for ballast water. Efficacy of ultrasonic treatment varied with the size of the test organism. Zooplankton required

Eric R. Holm; David M. Stamper; Robert A. Brizzolara; Laurie Barnes; Nora Deamer; JoAnn M. Burkholder

2008-01-01

373

The role of climate in shaping zooplankton communities of shallow lakes  

Microsoft Academic Search

We analyzed data from 81 shallow European lakes, which were sampled with standardized methods, for combined effects of climatic, physical, and chemical features of food-web interactions, with a specific focus on zooplankton biomass and community structure. Multiple-regression analysis showed that total phosphorus (TP) generally was the most important predictor of zooplankton biomass and community structure. Climate was the next most

M. Gyllström; L.-A. Hansson; E. Jeppesen; F. Garcia-Criado; E. M. Gross; K. Irvine; T. Kairesalo; R. Kornijow; Miracle Rosa M; M. Nykänen; T. Nõges; S. Romo; D. Stephen; E. Van Donk; B. Moss

2005-01-01

374

Distribution, abundance, and substrate preferences of demersal reef zooplankton at Lizard Island Lagoon, Great Barrier Reef  

Microsoft Academic Search

Demersal zooplankton, those plankton which hide within reef sediments during the day but emerge to swim freely over the reef at night, were sampled quantitatively using emergence traps planced over the substrate at Lizard Island Lagoon, Great Barrier Reef. Densities of zooplankton emerging at night from 6 substrate types (fine, medium, and coarse sand, rubble, living coral and reef rock)

A. L. Alldredge; J. M. King

1977-01-01

375

Effects of water color on predation regimes and zooplankton assemblages in freshwater lakes  

Microsoft Academic Search

Northern temperate lakes often have high water color because of high concentrations of dissolved organic carbon (DOC). Altered light, temperature, and oxygen profiles in these brown-water lakes should reduce the foraging abilities of planktivorous fish and reduce predation on zooplankton and invertebrate predators such as Chaoborus. Additionally, reduced diurnal vertical migration should limit exposure to cold temperatures and increase zooplankton

B. Wissel; W. J. Boeing; C. W. Ramcharan

2003-01-01

376

Near bottom depletion of zooplankton over coral reefs: I: diurnal dynamics and size distribution  

Microsoft Academic Search

Changes in the near-bottom abundance of zooplankton on scales of centimeters to meters and hours to seasons are of great importance to corals and other benthic zooplanktivores. Our objective was to characterize such spatio-temporal changes over several coral reefs in the Gulf of Aqaba, Red Sea. Using arrays of underwater pumps, we found a substantial depletion of zooplankton near the

Ruthy Yahel; Gitai Yahel; Amatzia Genin

2005-01-01

377

Spatial Patterns in Assemblage Structures of Pelagic Forage Fish and Zooplankton in Western Lake Superior  

Microsoft Academic Search

We assessed abundance, size, and species composition of forage fish and zooplankton communities of western Lake Superior during August 1996 and July 1997. Data were analyzed for three ecoregions (Duluth-Superior, Apostle Islands, and the open lake) differing in bathymetry and limnological and biological patterns. Zooplankton abundance was three times higher in the Duluth-Superior and Apostle Islands regions than in the

Timothy B. Johnson; Michael H. Hoff; Anett S. Trebitz; Charles R. Bronte; Timothy D. Corry; James F. Kitchell; Stephen J. Lozano; Doran M. Mason; Jill V. Scharold; Stephen T. Schram; Donald R. Schreiner

2004-01-01

378

Dynamics of Summer Biomass of Zooplankton in Lakes of the Zone of Temperate Climate  

Microsoft Academic Search

There is presently a large body of experimental data concerning the seasonal dynamics of zooplankton in lakes of the zone of temperate climate. These data were obtained in many studies and provided hydrobiologists with a sufficiently deep insight into the processes of zooplankton development in these lakes during the vegetation season. The onset of intense development of Protozoa and Rotatoria

M. B. Ivanova

2003-01-01

379

Zooplankton diversity analysis through single-gene sequencing of a community sample  

Microsoft Academic Search

BACKGROUND: Oceans cover more than 70% of the earth's surface and are critical for the homeostasis of the environment. Among the components of the ocean ecosystem, zooplankton play vital roles in energy and matter transfer through the system. Despite their importance, understanding of zooplankton biodiversity is limited because of their fragile nature, small body size, and the large number of

Ryuji J Machida; Yasuyuki Hashiguchi; Mutsumi Nishida; Shuhei Nishida

2009-01-01

380

Zooplankton responses to sandbar opening in a tropical eutrophic coastal lagoon  

Microsoft Academic Search

The effects of a disturbance by sandbar opening on the zooplankton community were evaluated through a long-term study in an eutrophic and oligohaline system, Imboassica Lagoon, Rio de Janeiro, Brazil. Zooplankton samples and limnological data were collected monthly from March 2000 to February 2003. Before the sandbar was opened in February 2001, the lagoon showed eutrophic conditions, with high mean

Jayme M. Santangelo; Adriana de M. Rocha; Reinaldo L. Bozelli; Luciana S. Carneiro; Francisco de A. Esteves

2007-01-01

381

AKKUYU KOYU (MERSIN) ZOOPLANKTONUNDAKI MEVSIMSEL DEGISIMLER THE SEASONAL CHANGES OF ZOOPLANKTON IN  

Microsoft Academic Search

In this study, seasonal changes in zooplankton diversity were investigated in Akkuyu Bay and near surroundings where it is being discussed to build the nuclear power plant, the coast of Mediterranean Sea, Mersin. The horizontal sampling was made with the standart zooplankton net of which mesh is 200µm. in May, August, November 1999 and February 2000. At the end of

Ayse DÖNMEZ; Ercan SARIHAN

382

Diel trophic interactions between vertically-migrating zooplankton and their fish predators in an eelgrass community  

Microsoft Academic Search

Diel changes in the composition of crustacean zooplankton and the diets of fish predators from an intertidal eelgrass flat were monitored concurrently. The zooplankton is characterized by two major components. The obligate zooplankters (holoplanktonic calanoid copepods and meroplanktonic decapod larvae) appear to exhibit vertical migration, being present in higher densities near the surface of the water column at night. The

A. I. Robertson; R. K. Howard

1978-01-01

383

Effect of Main-stem Dams on Zooplankton Communities of the Missouri River (USA)  

EPA Science Inventory

We examined the distribution and abundance of zooplankton from 146 sites on the Missouri River and found large shifts in the dominance of major taxa between management zones of this regulated river. Crustacean zooplankton were dominant in the inter-reservoir zone of the river, an...

384

Exploring Zooplankton Changes in Southern Lake Michigan: Implications for Yellow Perch Recruitment  

Microsoft Academic Search

Recruitment of fishes frequently depends in part on availability of appropriate densities and sizes of zooplankton prey. In Lake Michigan, yellow perch (Perca flavescens) have experienced poor recruitment since 1989, although the mechanisms driving this poor recruitment have not been identified. To explore the possible influence of zooplankton density available for yellow perch larvae shortly after hatching on eventual recruitment

John M. Dettmers; Matthew J. Raffenberg; Amy K. Weis

2003-01-01

385

Simplified zooplankton-net cod-end  

SciTech Connect

A simplified plankton-net cod-end has been field-tested in the tropical Atlantic Ocean and has proved to be both easy to use and effective in reducing the time needed to complete a net-station. The model tested was attached to a 75 cm net of 202 um mesh hauled vertically, but modifications to suit other needs are slight.

Duncan, C.P.

1980-12-01

386

A habitat-based population model for the Great Lakes population of the piping plover ( Charadrius melodus)  

Microsoft Academic Search

We created a stochastic habitat-based population model to compare the relative effectiveness of potential conservation strategies to increase the endangered Great Lakes population of piping plovers. Initial model parameters were based on an extensive 14-year dataset obtained by annual studies of breeding pairs in Michigan and 6 years of observations of color-marked individuals. Cumulative persistence probability curves and population trends

Lauren C Wemmer; Uygar Özesmi; Francesca J Cuthbert

2001-01-01

387

Human population dynamics revisited with the logistic model: How much can be modeled and predicted?  

Microsoft Academic Search

Decrease or growth of population comes from the interplay of death and birth (and locally, migration). We revive the logistic\\u000a model, which was tested and found wanting in early-20th-century studies of aggregate human populations, and apply it instead\\u000a to life expectancy (death) and fertility (birth), the key factors totaling population. For death, once an individual has legally\\u000a entered society, the

C. Marchetti; P. S. Meyer; J. H. Ausubel

2004-01-01

388

Factors associated with health care utilization among vulnerable populations: Using Gelberg's and Andersen's behavioral model for vulnerable populations  

Microsoft Academic Search

In 2001 Andersen and Gelberg introduced the Behavioral Model for Vulnerable Populations which enables the identification of factors that might be particularly relevant to health care utilization among vulnerable populations. This dissertation uses this model along with the Health Services Research Data to conduct secondary data analysis to evaluate the factors that are most likely to influence health utilization outcomes

La Fleur Small

2005-01-01

389

A computational model for populations of dividing cells.  

PubMed

A mathematical model of the cell movements due to cell division is presented. In the model we assume that every cell is a computational object with a given volume, and that the cell pushes the neighbouring cells in order to acquire the space for this volume. The Force that each cell exerts over the other cells is derived from a harmonic arbitrary Potential. The main parameter of the model is the average distance among the cells, that checks if the system is in spatial equilibrium or not. We show that just changing the physical constraints we can model two different systems, a two-dimensional culture on a plate and a three-dimensional early embryo. In both cases the patterns of the cell populations we obtain are similar to the real ones. PMID:12449685

Mersi, Giuseppe; Buiatti, Marcello

390

Calibrating Stellar Population Models with Magellanic Cloud Star Clusters  

NASA Astrophysics Data System (ADS)

Stellar population models are commonly calculated using star clusters as calibrators for those evolutionary stages that depend on free parameters. However, discrepancies exist among different models, even if similar sets of calibration clusters are used. With the aim of understanding these discrepancies, and of improving the calibration procedure, we consider a set of 43 Magellanic Cloud (MC) clusters, taking age and photometric information from the literature. We carefully assign ages to each cluster based on up-to-date determinations, ensuring that these are as homogeneous as possible. To cope with statistical fluctuations, we stack the clusters in five age bins, deriving for each of them integrated luminosities and colors. We find that clusters become abruptly red in optical and optical-infrared colors as they age from ~0.6 to ~1 Gyr, which we interpret as due to the development of a well-populated thermally pulsing asymptotic giant branch (TP-AGB). We argue that other studies missed this detection because of coarser age binnings. Maraston and Girardi et al. models predict the presence of a populated TP-AGB at ~0.6 Gyr, with a correspondingly very red integrated color, at variance with the data; Bruzual & Charlot and Conroy models run within the error bars at all ages. The discrepancy between the synthetic colors of Maraston models and the average colors of MC clusters results from the now obsolete age scale adopted. Finally, our finding that the TP-AGB phase appears to develop between ~0.6 and 1 Gyr is dependent on the adopted age scale for the clusters and may have important implications for stellar evolution.

Noël, N. E. D.; Greggio, L.; Renzini, A.; Carollo, C. M.; Maraston, C.

2013-07-01

391

Zooplankton of the Sandy Hook Bay area, N.J  

Microsoft Academic Search

The distribution and abundance of surface zooplankton in the Sandy Hook Bay area were studied biweekly from May 1969 through\\u000a May 1970. This embayment is located within the commercially valuable New York Bight. The volumetric mean of the plankton ranged\\u000a from 0.2–5.3 cc\\/m3, with a survey mea of 1.8 cc\\/m3. A maximum crop of 52,002 organisms\\/m3 was collected in May

L. E. Sage; S. S. Herman

1972-01-01

392

Cladoceran zooplankton abundance under clear and snow-covered ice  

USGS Publications Warehouse

We described the distribution of cladoceran zooplankton under the ice in a natural, glacial lake. Local light availability apparently altered the spatial distribution of cladocerans. Light levels measured under snow-covered areas (0.178 lux) were an order of magnitude less than those measured at the same depth under clear ice (1.750 lux). Cladoceran density under snow-covered areas was significantly higher (Bosmina spp.=3.34/L; Daphnia spp.=0.61/L) than cladoceran abundance under clear ice (Bosmina spp.=0.91/L; Daphnia spp.=0.19/L).

DeBates, T. J.; Chipps, S. R.; Ward, M. C.; Werlin, K. B.; Lorenzen, P. B.

2003-01-01

393

MIUSCAT: extended MILES spectral coverage - I. Stellar population synthesis models  

NASA Astrophysics Data System (ADS)

We extend the spectral range of our stellar population synthesis models based on the MILES and CaT empirical stellar spectral libraries. For this purpose, we combine these two libraries with the Indo-U.S. to construct composite stellar spectra to feed our models. The spectral energy distributions (SEDs) computed with these models and the originally published models are combined to construct composite SEDs for single-age, single-metallicity stellar populations (SSPs) covering the range ??3465-9469 Å at moderately high and uniform resolution (full width at half-maximum = 2.51 Å). The colours derived from these SSP SEDs provide good fits to Galactic globular cluster data. We find that the colours involving redder filters are very sensitive to the initial mass function (IMF), as well as a number of features and molecular bands throughout the spectra. To illustrate the potential use of these models, we focus on the Na I doublet at 8200 Å and with the aid of the newly synthesized SSP model SEDs, we define a new IMF-sensitive index that is based on this feature, which overcomes various limitations from previous index definitions for low-velocity dispersion stellar systems. We propose an index-index diagram based on this feature and the neighbouring Ca II triplet at 8600 Å, to constrain the IMF if the age and [Na/Fe] abundance are known. Finally we also show a survey-oriented spectrophotometric application which evidences the accurate flux calibration of these models for carrying out reliable spectral fitting techniques. These models are available through our user-friendly website.

Vazdekis, A.; Ricciardelli, E.; Cenarro, A. J.; Rivero-González, J. G.; Díaz-García, L. A.; Falcón-Barroso, J.

2012-07-01

394

Stylolite Populations in Limestone: Field Observations and Formation Models  

NASA Astrophysics Data System (ADS)

Stylolites are rough surfaces formed by localized dissolution, mostly in carbonates and sandstones. They often account for a large degree of dissolution, and their impact on porosity and permeability is well recognized. Still, many open questions remain regarding the formation mechanism of these Localized Volume Reduction features. We analyze stylolite formation using a new approach that examines them as populations, rather than as distinct features. A meso-scale field study of sedimentary stylolites in carbonates is combined with numerical modeling of their formation, to show that stylolite populations may be classified into three distinct end-members: isolated, long-parallel, and interconnected networks. Part of our fieldwork includes measurements conducted on >km long stylolites, the largest stylolite lateral distribution ever reported in the literature. Our numerical simulations show that different distributions of some catalyzing heterogeneity, which might be clay, can explain the emergence of the three different observed populations. Single, isolated, stylolites form in rocks containing small initial clay-rich "defects". In contrast, long parallel stylolite populations are formed when the initial rock contains long laterally continuous clay-rich bedding planes. Interconnected networks of stylolites or stylolite-fracture networks can form by joining of close-enough stylolites of either the isolated or the long parallel types. The observations and simulations together suggest that the combination of clay enhancement of dissolution and stress enhancement of dissolution create a feedback that localizes chemical compaction into stylolites.

Aharonov, E.; Laronne Ben-Itzhak, L.; Katsman, R.; Karcz, Z.; Kadori, M.

2011-12-01

395

Interacting trophic forcing and the population dynamics of herring.  

PubMed

Small pelagic fish occupy a central position in marine ecosystems worldwide, largely by determining the energy transfer from lower trophic levels to predators at the top of the food web, including humans. Population dynamics of small pelagic fish may therefore be regulated neither strictly bottom-up nor top-down, but rather through multiple external and internal drivers. While in many studies single drivers have been identified, potential synergies of multiple factors, as well as their relative importance in regulating population dynamics of small pelagic fish, is a largely unresolved issue. Using a statistical, age-structured modeling approach, we demonstrate the relative importance and influence of bottom-up (e.g., climate, zooplankton availability) and top-down (i.e., fishing and predation) factors on the population dynamics of Bothnian Sea herring (Clupea harengus) throughout its life cycle. Our results indicate significant bottom-up effects of zooplankton and interspecific competition from sprat (Sprattus sprattus), particularly on younger age classes of herring. Although top-down forcing through fishing and predation by grey seals (Halichoerus grypus) and Atlantic cod (Gadus morhua) also was evident, these factors were less important than resource availability and interspecific competition. Understanding key ecological processes and interactions is fundamental to ecosystem-based management practices necessary to promote sustainable exploitation of small pelagic fish. PMID:21870614

Lindegren, Martin; Ostman, Orjan; Gårdmark, Anna

2011-07-01

396

Medaka: a promising model animal for comparative population genomics  

PubMed Central

Background Within-species genome diversity has been best studied in humans. The international HapMap project has revealed a tremendous amount of single-nucleotide polymorphisms (SNPs) among humans, many of which show signals of positive selection during human evolution. In most of the cases, however, functional differences between the alleles remain experimentally unverified due to the inherent difficulty of human genetic studies. It would therefore be highly useful to have a vertebrate model with the following characteristics: (1) high within-species genetic diversity, (2) a variety of gene-manipulation protocols already developed, and (3) a completely sequenced genome. Medaka (Oryzias latipes) and its congeneric species, tiny fresh-water teleosts distributed broadly in East and Southeast Asia, meet these criteria. Findings Using Oryzias species from 27 local populations, we conducted a simple screening of nonsynonymous SNPs for 11 genes with apparent orthology between medaka and humans. We found medaka SNPs for which the same sites in human orthologs are known to be highly differentiated among the HapMap populations. Importantly, some of these SNPs show signals of positive selection. Conclusion These results indicate that medaka is a promising model system for comparative population genomics exploring the functional and adaptive significance of allelic differentiations.

Matsumoto, Yoshifumi; Oota, Hiroki; Asaoka, Yoichi; Nishina, Hiroshi; Watanabe, Koji; Bujnicki, Janusz M; Oda, Shoji; Kawamura, Shoji; Mitani, Hiroshi

2009-01-01

397

Reduced growth and survival of larval razorback sucker fed selenium-laden zooplankton  

USGS Publications Warehouse

Four groups of larval razorback sucker, an endangered fish, were exposed to selenium-laden zooplankton and survival, growth, and whole-body residues were measured. Studies were conducted with 5, 10, 24, and 28-day-old larvae fed zooplankton collected from six sites adjacent to the Green River, Utah. Water where zooplankton were collected had selenium concentrations ranging from <0.4 to 78 ??g/L, and concentrations in zooplankton ranged from 2.3 to 91 ??g/g dry weight. Static renewal tests were conducted for 20 to 25 days using reference water with selenium concentrations of <1.1 ??g/L. In all studies, 80-100% mortality occurred in 15-20 days. In the 28-day-old larvae, fish weight was significantly reduced 25% in larvae fed zooplankton containing 12 ??g/g selenium. Whole-body concentrations of selenium ranged from 3.7 to 14.3 ??g/g in fish fed zooplankton from the reference site (Sheppard Bottom pond 1) up to 94 ??g/g in fish fed zooplankton from North Roadside Pond. Limited information prior to the studies suggested that the Sheppard pond 1 site was relatively clean and suitable as a reference treatment; however, the nearly complete mortality of larvae and elevated concentrations of selenium in larvae and selenium and other elements in zooplankton indicated that this site was contaminated with selenium and other elements. Selenium concentrations in whole-body larvae and in zooplankton from all sites were close to or greater than toxic thresholds where adverse effects occur in fish. Delayed mortality occurred in larvae fed the two highest selenium concentrations in zooplankton and was thought due to an interaction with other elements. ?? 2004 Elsevier Inc. All rights reserved.

Hamilton, S. J.; Buhl, K. J.; Bullard, F. A.; McDonald, S. F.

2005-01-01

398

Zooplankton size selection relative to gill raker spacing in rainbow trout  

USGS Publications Warehouse

Rainbow trout Oncorhynchus mykiss are one of the most widely stocked salmonids worldwide, often based on the assumption that they will effectively utilize abundant invertebrate food resources. We evaluated the potential for feeding morphology to affect prey selection by rainbow trout using a combination of laboratory feeding experiments and field observations in Flaming Gorge Reservoir, Utah-Wyoming. For rainbow trout collected from the reservoir, inter-gill raker spacing averaged 1.09 mm and there was low variation among fish overall (SD = 0.28). Ninety-seven percent of all zooplankton observed in the diets of rainbow trout collected in the reservoir were larger than the interraker spacing, while only 29% of the zooplankton found in the environment were larger than the interraker spacing. Over the size range of rainbow trout evaluated here (200-475 mm), interraker spacing increased moderately with increasing fish length; however, the size of zooplankton found in the diet did not increase with increasing fish length. In laboratory experiments, rainbow trout consumed the largest zooplankton available; the mean size of zooplankton observed in the diets was significantly larger than the mean size of zooplankton available. Electivity indices for both laboratory and field observations indicated strong selection for larger-sized zooplankton. The size threshold at which electivity switched from selection against smaller-sized zooplankton to selection for larger-sized zooplankton closely corresponded to the mean interraker spacing for both groups (???1-1.2 mm). The combination of results observed here indicates that rainbow trout morphology limits the retention of different-sized zooplankton prey and reinforces the importance of understanding how effectively rainbow trout can utilize the type and sizes of different prey available in a given system. These considerations may improve our ability to predict the potential for growth and survival of rainbow trout within and among different systems. ?? Copyright by the American Fisheries Society 2005.

Budy, P.; Haddix, T.; Schneidervin, R.

2005-01-01

399

Population balance model versus lumped model for emulsion polymerisation: Semi-batch and continuous operation  

Microsoft Academic Search

In this article, a systematic comparison is made of a detailed population balance model of the emulsion polymerisation process that accounts for the dynamic evolution of the entire particle size distribution with a simple model of the process that accounts only for the dynamic evolution of the average particle size and the total particles. Both models account for the underlying

Charles D. Immanuel; Mark A. Pinto; John R. Richards; John P. Congalidis

2008-01-01

400

Modelling the cyclic behaviour in a DTB crystallizer—a two-population balance model approach  

Microsoft Academic Search

A novel approach is introduced here to improve the description of the dynamic behaviour of industrial crystallizers using a two-population balance model to discriminate between primary and secondary nuclei. A heterogeneous primary nucleation model is implemented in a rigorous crystallizer model framework to explain the sustained oscillatory behaviour observed in industrial draft-tube baffle (DTB) crystallizers. The distinction between primary and

A. R. Menon; H. J. M. Kramer; J. Grievink; P. J. Jansens

2005-01-01

401

Modelling Multi-Pulse Population Dynamics from Ultrafast Spectroscopy  

PubMed Central

Current advanced laser, optics and electronics technology allows sensitive recording of molecular dynamics, from single resonance to multi-colour and multi-pulse experiments. Extracting the occurring (bio-) physical relevant pathways via global analysis of experimental data requires a systematic investigation of connectivity schemes. Here we present a Matlab-based toolbox for this purpose. The toolbox has a graphical user interface which facilitates the application of different reaction models to the data to generate the coupled differential equations. Any time-dependent dataset can be analysed to extract time-independent correlations of the observables by using gradient or direct search methods. Specific capabilities (i.e. chirp and instrument response function) for the analysis of ultrafast pump-probe spectroscopic data are included. The inclusion of an extra pulse that interacts with a transient phase can help to disentangle complex interdependent pathways. The modelling of pathways is therefore extended by new theory (which is included in the toolbox) that describes the finite bleach (orientation) effect of single and multiple intense polarised femtosecond pulses on an ensemble of randomly oriented particles in the presence of population decay. For instance, the generally assumed flat-top multimode beam profile is adapted to a more realistic Gaussian shape, exposing the need for several corrections for accurate anisotropy measurements. In addition, the (selective) excitation (photoselection) and anisotropy of populations that interact with single or multiple intense polarised laser pulses is demonstrated as function of power density and beam profile. Using example values of real world experiments it is calculated to what extent this effectively orients the ensemble of particles. Finally, the implementation includes the interaction with multiple pulses in addition to depth averaging in optically dense samples. In summary, we show that mathematical modelling is essential to model and resolve the details of physical behaviour of populations in ultrafast spectroscopy such as pump-probe, pump-dump-probe and pump-repump-probe experiments.

van Wilderen, Luuk J. G. W.; Lincoln, Craig N.; van Thor, Jasper J.

2011-01-01

402

Matrix population models as a tool in development of habitat models  

Treesearch

Matrix population models represent a powerful tool to aid in designing habitat research. ... focus field efforts toward measuring the most important demographic parameters, ... During the capture process some typographical errors may occur.

403

Modeling the population dynamics of phytoplankton in lacustrine ecosystems  

NASA Astrophysics Data System (ADS)

Phytoplankton are microscopic plants, diverse in shape, and form the basis of aquatic ecosystems. Through both photosynthesis and respiration, they produce organic compounds and contribute notably to the Earth's carbon cycle, which make the population dynamics of phytoplankton important in discussions on climate change. In this talk, we introduce a model that predicts the vertical distribution of phytoplankton in freshwater lakes. The growth of phytoplankton is intimately connected to nutrient and light availability. Quantifying the growth due to light availability requires quantifying the seasonal settling velocity of the particles. Careful consideration is paid to the interaction between the forces of buoyancy, gravity, and drag. To accurately formulate settling velocity, the low Reynolds nature of the system is exploited and added to an experimental, laboratory component. The laboratory research is guided by the use of a sedimentation tank and a collection of vertical cylinders that allow the characterization of particle separation and settling velocity for sparse phytoplankton populations of both spherical and slender shape.

Leiterman, Terry Jo

2011-11-01

404

Spectral models for solar-scaled and ?-enhanced stellar populations  

NASA Astrophysics Data System (ADS)

We present the first models allowing one to explore in a consistent way the influence of changes in the ?-element-to-iron abundance ratio on the high-resolution spectral properties of evolving stellar populations. The models cover the wavelength range from 3000 Å to 1.34?m at a constant resolution of full width at half-maximum (FWHM) = 1 Å and a sampling of 0.2 Å, for overall metallicities in the range 0.005 <= Z <= 0.048 and for stellar population ages between 3 and 14 Gyr. These models are based on a recent library of synthetic stellar spectra and a new library of stellar evolutionary tracks, both computed for three different iron abundances ([Fe/H] = -0.5, 0.0 and 0.2) and two different ?-element-to-iron abundance ratios ([?/Fe] = 0.0 and 0.4). We expect our fully synthetic models to be primarily useful for evaluating the differential effect of changes in the ?/Fe ratio on spectral properties such as broad-band colours and narrow spectral features. In addition, we assess the accuracy of absolute model predictions in two ways: first, by comparing the predictions of models for scaled-solar metal abundances ([?/Fe] = 0.0) to those of existing models based on libraries of observed stellar spectra; and secondly, by comparing the predictions of models for ?-enhanced metal abundances ([?/Fe] = 0.4) to observed spectra of massive early-type galaxies in the Sloan Digital Sky Survey Data Release 4. We find that our models predict accurate strengths for those spectral indices that are strongly sensitive to the abundances of Fe and ? elements. The predictions are less reliable for the strengths of other spectral features, such as those dominated by the abundances of C and N, as expected from the fact that the models do not yet allow one to explore the influence of these elements in an independent way. We conclude that our models are a powerful tool for extracting new information about the chemical properties of galaxies for which high-quality spectra have been gathered by modern surveys.

Coelho, P.; Bruzual, G.; Charlot, S.; Weiss, A.; Barbuy, B.; Ferguson, J. W.

2007-12-01

405

Temperature dependence of Arctic zooplankton metabolism and excretion stoichiometry  

NASA Astrophysics Data System (ADS)

We assessed the relationship between zooplankton metabolism (respiration and inorganic N and P excretion) and "in situ" temperature through a grid of stations representing a range of natural temperature variation during the ATOS-Arctic cruise (July 2007). The objective was to explore not only the direct effects of temperature on O2 consumption and NH4-N and PO4-P excretion, but also to investigate the possible relationships between temperature and the stoichiometry of the metabolic products. Zooplankton metabolic rates increased according to the rising temperature conditions, following the Arrhenius equation. However, the activation energy differed for the various metabolic processes considered. Respiration was the metabolic activity less affected by temperature, followed by NH4-N and PO4-P excretion, and as a consequence the values of the C : N, C : P and N : P quotients of the metabolic products were inversely related to temperature. The effects of temperature on the stoichiometry of the excretion products would contribute to modify the nutrient pool available for phytoplankton and induce qualitative and quantitative shifts in the characteristics of primary producers that could possibly translate into the whole Arctic marine food web.

Alcaraz, M.; Almeda, R.; Saiz, E.; Calbet, A.; Duarte, C. M.; Agustí, S.; Santiago, R.; Alonso, A.

2012-06-01

406

Individual-based modeling, population dynamics, and fisheries recruitment success  

SciTech Connect

Prediction of recruitment success is a critical problem in fisheries research. From a theoretical perspective, the ability to predict the number and characteristics of reproducing survivors underlies the field of quantitative population dynamics. Form a practical perspective, rationale and efficient management of fisheries resources requires the ability to accurately forecast the effects of disturbances, both natural and anthropogenic in origin, on fish populations. The objective of this paper is to advocate individual- based modelling as an alternative to the more traditional approaches for predicting recruitment success. First, some reasons for the limited success to date in making long-term predictions of fisheries recruitment are summarized. The importance of information on individuals, rather than on the average individual, is then illustrated as the fallacy of the average'' using two sets of experimental data. The general ideas behind individual-based modelling, and four examples of individual-based models involving fish, are then briefly described. Finally, we make some concluding remarks. Two caveats are necessary. This paper is a summary of a workshop presentation; we therefore take many liberties and make gross generalizations throughout the paper. Also, although not explicitly stated, our discussion is based more on estuarine and marine, than on freshwater, fishes. 8 refs., 6 figs.

Rose, K.A.; DeAngelis, D.L.; Barnthouse, W.; Van Winkle, W.

1990-01-01

407

The model of fungal population dynamics affected by nystatin  

NASA Astrophysics Data System (ADS)

Fungal diseases are acute problems of the up-to-day medicine. Significant increase of resistance of microorganisms to the medically used antibiotics and a lack of new effective drugs follows in a growth of dosage of existing chemicals to solve the problem. Quite often such approach results in side effects on humans. Detailed study of fungi-antibiotic dynamics can identify new mechanisms and bring new ideas to overcome the microbial resistance with a lower dosage of antibiotics. In this study, the dynamics of the microbial population under antibiotic treatment was investigated. The effects of nystatin on the population of Saccharomyces cerevisiae yeasts were used as a model system. Nystatin effects were investigated both in liquid and solid media by viability tests. Dependence of nystatin action on osmotic gradient was evaluated in NaCl solutions. Influences of glucose and yeast extract were additionally analyzed. A "stepwise" pattern of the cell death caused by nystatin was the most intriguing. This pattern manifested in periodical changes of the stages of cell death against stages of resistance to the antibiotic. The mathematical model was proposed to describe cell-antibiotic interactions and nystatin viability effects in the liquid medium. The model implies that antibiotic ability to cause a cells death is significantly affected by the intracellular compounds, which came out of cells after their osmotic barriers were damaged

Voychuk, Sergei I.; Gromozova, Elena N.; Sadovskiy, Mikhail G.

408

Zooplankton stable isotopes as integrators of bottom-up variability in coastal margins: A case study from the Strait of Georgia and adjacent coastal regions  

NASA Astrophysics Data System (ADS)

We correlate zooplankton stable isotopes and environmental variables in coastal margins.In the Strait of Georgia, isotopes are correlated with chlorophyll and zooplankton biomass in the spring.On the west coast of Vancouver Island ?15N is correlated with temperature.Interannual variability in zooplankton isotopes reflects oceanographic conditions.Zooplankton isotopes can potentially link environmental conditions and higher trophic levels.

El-Sabaawi, Rana; Trudel, Marc; Mazumder, Asit

2013-08-01

409

EVALUATION OF OPTICALLY ACQUIRED ZOOPLANKTON SIZE-SPECTRUM DATA AS A POTENTIAL TOOL FOR ASSESSMENT OF CONDITION IN THE GREAT LAKES  

EPA Science Inventory

An optical zooplankton counter (OPC) potentially provides as assessment tool for zooplankton condition in ecosystems that is rapid, economical, and spatially extensive. We collected zooplankton data with an optical zooplankton counter in 20 near-shore regions of four of the Laure...

410

The two populations' cellular automata model with predation based on the Penna model  

NASA Astrophysics Data System (ADS)

In Penna's single-species asexual bit-string model of biological ageing, the Verhulst factor has too strong a restraining effect on the development of the population. Danuta Makowiec gave an improved model based on the lattice, where the restraining factor of the four neighbours take the place of the Verhulst factor. Here, we discuss the two populations' Penna model with predation on the planar lattice of two dimensions. A cellular automata model containing movable wolves and sheep has been built. The results show that both the quantity of the wolves and the sheep fluctuate in accordance with the law that one quantity increases while the other one decreases.

He, Mingfeng; Lin, Jing; Jiang, Heng; Liu, Xin

2002-09-01

411

A cell population balance model describing positive feedback loop expression dynamics  

Microsoft Academic Search

Biological systems are inherently heterogeneous in the sense that cellular content is unevenly distributed amongst the cells of the population. In this work, we develop a cell population balance-modeling framework, which integrates biological detail at the single-cell level to accurately predict the dynamics of the distribution of cellular properties at the cell population level. The developed cell population balance model

Nikos V. Mantzaris

2005-01-01

412

Estimating effects of adult male mortality on grizzly bear population growth and persistence using matrix models  

Microsoft Academic Search

We radio monitored a hunted, sexually segregated grizzly bear (Ursus arctos) population and an unhunted, unsegregated population for demographics and constructed a stage- and age-classified matrix model to test for the effects of adult male mortality and resulting sexual segregation on population growth and persistence. Population parameters in the model were adult female survival, subadult female survival, offspring survival, probability

Robert B. Wielgus; Francois Sarrazin; Regis Ferriere; Jean Clobert

2001-01-01

413

The evolutionary potential of paramutation: a population-epigenetic model.  

PubMed

Paramutation involves an interaction between homologous alleles resulting in a heritable change in gene expression without altering the DNA sequence. Initially believed to be restricted to plants, paramutation has recently been observed in animal models, and a paramutation-like event has been noted in humans. Despite the accumulating evidence suggesting that trans-acting epigenetic effects can be inherited transgenerationally and therefore generate non-genomic phenotypic variation, these effects have been largely ignored in the context of evolutionary theory. The model presented here incorporates paramutation into the standard model of viability selection at one locus and demonstrates that paramutation can create long-term biological diversity in the absence of genetic change, and even in the absence of the original paramutagenic allele. Therefore, if paramutation is present, attributing evolution to only a traditional genetic model may fail to encompass the broad scope of phenotypic differences observed in nature. Moreover, we show also that an unusual mathematical behaviour, analogous to "Ewens' gap" of the two-locus two-allele symmetric-selection model, occurs: when the rate of one parameter-for example, the rate of paramutation-is increased, a pair of equilibria may disappear only to reappear as this parameter increases further. In summary, by incorporating even the simplest epigenetic parameters into the standard population-genetic model of selection, we show how this type of inheritance system can profoundly alter the course of evolution. PMID:23751219

Geoghegan, Jemma L; Spencer, Hamish G

2013-06-07

414

A “Rosetta Stone” for metazoan zooplankton: DNA barcode analysis of species diversity of the Sargasso Sea (Northwest Atlantic Ocean)  

NASA Astrophysics Data System (ADS)

Species diversity of the metazoan holozooplankton assemblage of the Sargasso Sea, Northwest Atlantic Ocean, was examined through coordinated morphological taxonomic identification of species and DNA sequencing of a ˜650 base-pair region of mitochondrial cytochrome oxidase I (mtCOI) as a DNA barcode (i.e., short sequence for species recognition and discrimination). Zooplankton collections were made from the surface to 5,000 meters during April, 2006 on the R/V R.H. Brown. Samples were examined by a ship-board team of morphological taxonomists; DNA barcoding was carried out in both ship-board and land-based DNA sequencing laboratories. DNA barcodes were determined for a total of 297 individuals of 175 holozooplankton species in four phyla, including: Cnidaria (Hydromedusae, 4 species; Siphonophora, 47); Arthropoda (Amphipoda, 10; Copepoda, 34; Decapoda, 9; Euphausiacea, 10; Mysidacea, 1; Ostracoda, 27); and Mollusca (Cephalopoda, 8; Heteropoda, 6; Pteropoda, 15); and Chaetognatha (4). Thirty species of fish (Teleostei) were also barcoded. For all seven zooplankton groups for which sufficient data were available, Kimura-2-Parameter genetic distances were significantly lower between individuals of the same species (mean=0.0114; S.D. 0.0117) than between individuals of different species within the same group (mean=0.3166; S.D. 0.0378). This difference, known as the barcode gap, ensures that mtCOI sequences are reliable characters for species identification for the oceanic holozooplankton assemblage. In addition, DNA barcodes allow recognition of new or undescribed species, reveal cryptic species within known taxa, and inform phylogeographic and population genetic studies of geographic variation. The growing database of "gold standard" DNA barcodes serves as a Rosetta Stone for marine zooplankton, providing the key for decoding species diversity by linking species names, morphology, and DNA sequence variation. In light of the pivotal position of zooplankton in ocean food webs, their usefulness as rapid responders to environmental change, and the increasing scarcity of taxonomists, the use of DNA barcodes is an important and useful approach for rapid analysis of species diversity and distribution in the pelagic community.

Bucklin, Ann; Ortman, Brian D.; Jennings, Robert M.; Nigro, Lisa M.; Sweetman, Christopher J.; Copley, Nancy J.; Sutton, Tracey; Wiebe, Peter H.

2010-12-01

415

Strong spatial influence on colonization rates in a pioneer zooplankton metacommunity.  

PubMed

The magnitude of community-wide dispersal is central to metacommunity models, yet dispersal is notoriously difficult to quantify in passive and cryptic dispersers such as many freshwater invertebrates. By overcoming the problem of quantifying dispersal rates, colonization rates into new habitats can provide a useful estimate of the magnitude of effective dispersal. Here we study the influence of spatial and local processes on colonization rates into new ponds that indicate differential dispersal limitation of major zooplankton taxa, with important implications for metacommunity dynamics. We identify regional and local factors that affect zooplankton colonization rates and spatial patterns in a large-scale experimental system. Our study differs from others in the unique setup of the experimental pond area by which we were able to test spatial and environmental variables at a large spatial scale. We quantified colonization rates separately for the Copepoda, Cladocera and Rotifera from samples collected over a period of 21 months in 48 newly constructed temporary ponds of 0.18-2.95 ha distributed in a restored wetland area of 2,700 ha in Doñana National Park, Southern Spain. Species richness upon initial sampling of new ponds was about one third of that in reference ponds, although the rate of detection of new species from thereon were not significantly different, probably owing to high turnover in the dynamic, temporary reference ponds. Environmental heterogeneity had no detectable effect on colonization rates in new ponds. In contrast, connectivity, space (based on latitude and longitude) and surface area were key determinants of colonization rates for copepods and cladocerans. This suggests dispersal limitation in cladocerans and copepods, but not in rotifers, possibly due to differences in propagule size and abundance. PMID:22792241

Frisch, Dagmar; Cottenie, Karl; Badosa, Anna; Green, Andy J

2012-07-06

416

Population.  

ERIC Educational Resources Information Center

In an effort to help meet the growing interest and concern about the problems created by the rapid growth of population, The International Planned Parenthood Federation has prepared this booklet with the aim of assisting the study of the history and future trends of population growth and its impact on individual and family welfare, national,…

International Planned Parenthood Federation, London (England).

417

Vertical distribution and diel patterns of zooplankton abundance and biomass at Conch Reef, Florida Keys (USA)  

PubMed Central

Zooplankton play an important role in the trophic dynamics of coral reef ecosystems. Detailed vertical and temporal distribution and biomass of zooplankton were evaluated at four heights off the bottom and at six times throughout the diel cycle over a coral reef in the Florida Keys (USA). Zooplankton abundance averaged 4396 ± 1949 SD individuals m?3, but temporal and spatial distributions varied for individual zooplankton taxa by time of day and by height off the bottom. Copepods comprised 93–96% of the abundance in the samples. Taxon-based zooplankton CHN values paired with abundance data were used to estimate biomass. Average daily biomass ranged from 3.1 to 21.4 mg C m?3 and differed by both height off the bottom and by time of day. While copepods were the numerically dominant organisms, their contribution to biomass was only 35% of the total zooplankton biomass. Our findings provide important support for the new emerging paradigm of how zooplankton are distributed over reefs.

Heidelberg, Karla B.; O'Neil, Keri L.; Bythell, John C.; Sebens, Kenneth P.

2010-01-01

418

First evidence for zooplankton feeding sustaining key physiological processes in a scleractinian cold-water coral.  

PubMed

Scleractinian cold-water corals (CWC) represent key taxa controlling deep-sea reef ecosystem functioning by providing structurally complex habitats to a high associated biodiversity, and by fuelling biogeochemical cycles via the release of organic matter. Nevertheless, our current knowledge on basic CWC properties, such as feeding ecology and key physiological processes (i.e. respiration, calcification and organic matter release), is still very limited. Here, we show evidence for the trophic significance of zooplankton, essentially sustaining levels of the investigated key physiological processes in the cosmopolitan CWC Desmophyllum dianthus (Esper 1794). Our results from laboratory studies reveal that withdrawal (for up to 3 weeks) of zooplankton food (i.e. Artemia salina) caused a significant decline in respiration (51%) and calcification (69%) rates compared with zooplankton-fed specimens. Likewise, organic matter release, in terms of total organic carbon (TOC), decreased significantly and eventually indicated TOC net uptake after prolonged zooplankton exclusion. In fed corals, zooplankton provided 1.6 times the daily metabolic C demand, while TOC release represented 7% of zooplankton-derived organic C. These findings highlight zooplankton as a nutritional source for D. dianthus, importantly sustaining respiratory metabolism, growth and organic matter release, with further implications for the role of CWC as deep-sea reef ecosystem engineers. PMID:21993785

Naumann, Malik S; Orejas, Covadonga; Wild, Christian; Ferrier-Pagès, Christine

2011-11-01

419

Modelling the Growing Population of ?-ray Millisecond Pulsars  

NASA Astrophysics Data System (ADS)

TheFermiLarge Area Telescope, in collaboration with several groups from the radio community, have had marvellous success at uncovering new ?-ray millisecond pulsars (MSPs). In fact, MSPs now make up a sizable fraction of the total number of known ?-ray pulsars. The MSP population is characterized by a variety of pulse profile shapes, peak separations, and radio-to-? phase lags, with some members exhibiting nearly phase-aligned radio and ?-ray light curves (LCs). The MSPs' short spin periods underline the importance of including special relativistic effects in LC calculations, even for emission originating from near the stellar surface. We present results on modelling and classification of MSP LCs using standard pulsar model geometries.

Venter, C.; Harding, A. K.; Johnson, T. J.

420

Modelling Oyster Population Response to Variation in Freshwater Input  

NASA Astrophysics Data System (ADS)

This paper describes the linkage of a three-dimensional hydrodynamic circulation model with descriptive and experimental biological data concerning oyster ( Crassostrea virginica) population dynamics in the Apalachicola Estuary (Florida, U.S.A.). Our intent was to determine the direct and indirect role of Apalachicola River flow in the maintenance of oyster production. Results of a monthly field sampling programme conducted on the oyster reefs in the Apalachicola system during 1985-1986 were used to develop statistical models relating several life-history characteristics of oysters to physical-chemical aspects of water quality. The same life-history characteristics were related statistically to output from a circulation model of Apalachicola Bay. Highest oyster densities and overall bar growth were found in the vicinity of the confluence of high salinity water moving westwards from St George Sound and river-dominated (low salinity) water moving south and eastwards from East Bay. With the exception of models for oyster mortality, the predictive capability of results from the parallel modelling efforts was low. A time-averaged model was developed for oyster mortality during the summer of 1985 by running a regression analysis with averaged predictors derived from the hydrodynamic model and observed (experimental) mortality rates throughout the estuary. A geographic information system was then used to depict the results spatially and to compare the extent of expected mortality in 1985 and 1986. High salinity, relatively low-velocity current patterns, and the proximity of a given oyster bar to entry points of saline Gulf water into the bay were important factors that contribute to increased oyster mortality. Mortality was a major determinant of oyster production in the Apalachicola Estuary with predation as a significant aspect of such mortality. By influencing salinity levels and current patterns throughout the bay, the Apalachicola River was important in controlling such mortality. Oyster production rates in the Apalachicola system depend on a combination of variables that are directly and indirectly associated with freshwater input as modified by wind, tidal factors, and the physiography of the bay. River flow reduction, whether through naturally occurring droughts, through increased upstream anthropogenous (consumptive) water use, or a combination of the two, could have serious adverse consequences for oyster populations. By coupling hydrodynamic modelling with descriptive and experimental biological data, we were able to determine the effects of potential freshwater diversions on oyster production in Apalachicola Bay.

Livingston, R. J.; Lewis, F. G.; Woodsum, G. C.; Niu, X.-F.; Galperin, B.; Huang, W.; Christensen, J. D.; Monaco, M. E.; Battista, T. A.; Klein, C. J.; Howell, R. L.; Ray, G. L.

2000-05-01

421

Skeeter Buster: A Stochastic, Spatially Explicit Modeling Tool for Studying Aedes aegypti Population Replacement and Population Suppression Strategies  

PubMed Central

Background Dengue is the most important mosquito-borne viral disease affecting humans. The only prevention measure currently available is the control of its vectors, primarily Aedes aegypti. Recent advances in genetic engineering have opened the possibility for a new range of control strategies based on genetically modified mosquitoes. Assessing the potential efficacy of genetic (and conventional) strategies requires the availability of modeling tools that accurately describe the dynamics and genetics of Ae. aegypti populations. Methodology/Principal findings We describe in this paper a new modeling tool of Ae. aegypti population dynamics and genetics named Skeeter Buster. This model operates at the scale of individual water-filled containers for immature stages and individual properties (houses) for adults. The biology of cohorts of mosquitoes is modeled based on the algorithms used in the non-spatial Container Inhabiting Mosquitoes Simulation Model (CIMSiM). Additional features incorporated into Skeeter Buster include stochasticity, spatial structure and detailed population genetics. We observe that the stochastic modeling of individual containers in Skeeter Buster is associated with a strongly reduced temporal variation in stage-specific population densities. We show that heterogeneity in container composition of individual properties has a major impact on spatial heterogeneity in population density between properties. We detail how adult dispersal reduces this spatial heterogeneity. Finally, we present the predicted genetic structure of the population by calculating FST values and isolation by distance patterns, and examine the effects of adult dispersal and container movement between properties. Conclusions/Significance We demonstrate that the incorporated stochasticity and level of spatial detail have major impacts on the simulated population dynamics, which could potentially impact predictions in terms of control measures. The capacity to describe population genetics confers the ability to model the outcome of genetic control methods. Skeeter Buster is therefore an important tool to model Ae. aegypti populations and the outcome of vector control measures.

Puente, Molly E.; Focks, Dana A.; Scott, Thomas W.; Lloyd, Alun L.; Gould, Fred

2009-01-01

422

Image-driven Population Analysis through Mixture Modeling  

PubMed Central

We present iCluster, a fast and efficient algorithm that clusters a set of images while co-registering them using a parameterized, nonlinear transformation model. The output of the algorithm is a small number of template images that represent different modes in a population. This is in contrast with traditional, hypothesis-driven computational anatomy approaches that assume a single template to construct an atlas. We derive the algorithm based on a generative model of an image population as a mixture of deformable template images. We validate and explore our method in four experiments. In the first experiment, we use synthetic data to explore the behavior of the algorithm and inform a design choice on parameter settings. In the second experiment, we demonstrate the utility of having multiple atlases for the application of localizing temporal lobe brain structures in a pool of subjects that contains healthy controls and schizophrenia patients. Next, we employ iCluster to partition a data set of 415 whole brain MR volumes of subjects aged 18 through 96 years into three anatomical subgroups. Our analysis suggests that these subgroups mainly correspond to age groups. The templates reveal significant structural differences across these age groups that confirm previous findings in aging research. In the final experiment, we run iCluster on a group of 15 patients with dementia and 15 age-matched healthy controls. The algorithm produces two modes, one of which contains dementia patients only. These results suggest that the algorithm can be used to discover sub-populations that correspond to interesting structural or functional “modes.”

Sabuncu, Mert R.; Balci, Serdar K.; Shenton, Martha E.; Golland, Polina

2009-01-01

423

Estimating population trends with a linear model: technical comments  

USGS Publications Warehouse

Controversy has sometimes arisen over whether there is a need to accommodate the limitations of survey design in estimating population change from the count data collected in bird surveys. Analyses of surveys such as the North American Breeding Bird Survey (BBS) can be quite complex; it is natural to ask if the complexity is necessary, or whether the statisticians have run amok. Bart et al. (2003) propose a very simple analysis involving nothing more complicated than simple linear regression, and contrast their approach with model-based procedures. We review the assumptions implicit to their proposed method, and document that these assumptions are unlikely to be valid for surveys such as the BBS. One fundamental limitation of a purely design-based approach is the absence of controls for factors that influence detection of birds at survey sites. We show that failure to model observer effects in survey data leads to substantial bias in estimation of population trends from BBS data for the 20 species that Bart et al. (2003) used as the basis of their simulations. Finally, we note that the simulations presented in Bart et al. (2003) do not provide a useful evaluation of their proposed method, nor do they provide a valid comparison to the estimating- equations alternative they consider.

Sauer, J.R.; Link, W.A.; Royle, J.A.

2004-01-01

424

Modelling the Populations of Trans-Neptunian Objects.  

NASA Astrophysics Data System (ADS)

The trans-neptunian region is yet another example of a collisional system of small bodies in the Solar System. In the last decade the number of TNOs with reliable orbital elements is steadily increasing and we can begin to try and compare collisional evolution models to observed populations. With this aim we are developing a model that takes into account the known physics of the fragmentation of icy/rocky bodies, including recently published experimental results, and that considers the different orbital characteristics of the different zones of the trans-neptunian region: plutinos, classical belt and scattered disk. What was the primordial distribution in this region? Is the trans-neptunian belt collisionally relaxed? What fraction of the TNO population is likely constituted by gravitational aggregates? These are just some of the questions we would like to help and give an answer to with this research. Preliminary results are presented. We thank our home institution, the Universidad de Alicante, Alicante (Spain), for supporting this research.

Campo Bagatin, A.; Benavidez, P. G.

2005-08-01

425

Stable isotope and signature Fatty Acid analyses suggest reef manta rays feed on demersal zooplankton.  

PubMed

Assessing the trophic role and interaction of an animal is key to understanding its general ecology and dynamics. Conventional techniques used to elucidate diet, such as stomach content analysis, are not suitable for large threatened marine species. Non-lethal sampling combined with biochemical methods provides a practical alternative for investigating the feeding ecology of these species. Stable isotope and signature fatty acid analyses of muscle tissue were used for the first time to examine assimilated diet of the reef manta ray Manta alfredi, and were compared with different zooplankton functional groups (i.e. near-surface zooplankton collected during manta ray feeding events and non-feeding periods, epipelagic zooplankton, demersal zooplankton and several different zooplankton taxa). Stable isotope ?(15)N values confirmed that the reef manta ray is a secondary consumer. This species had relatively high levels of docosahexaenoic acid (DHA) indicating a flagellate-based food source in the diet, which likely reflects feeding on DHA-rich near-surface and epipelagic zooplankton. However, high levels of ?6 polyunsaturated fatty acids and slightly enriched ?(13)C values in reef manta ray tissue suggest that they do not feed solely on pelagic zooplankton, but rather obtain part of their diet from another origin. The closest match was with demersal zooplankton, suggesting it is an important component of the reef manta ray diet. The ability to feed on demersal zooplankton is likely linked to the horizontal and vertical movement patterns of this giant planktivore. These new insights into the habitat use and feeding ecology of the reef manta ray will assist in the effective evaluation of its conservation needs. PMID:24167562

Couturier, Lydie I E; Rohner, Christoph A; Richardson, Anthony J; Marshall, Andrea D; Jaine, Fabrice R A; Bennett, Michael B; Townsend, Kathy A; Weeks, Scarla J; Nichols, Peter D

2013-10-22

426

Stable Isotope and Signature Fatty Acid Analyses Suggest Reef Manta Rays Feed on Demersal Zooplankton  

PubMed Central

Assessing the trophic role and interaction of an animal is key to understanding its general ecology and dynamics. Conventional techniques used to elucidate diet, such as stomach content analysis, are not suitable for large threatened marine species. Non-lethal sampling combined with biochemical methods provides a practical alternative for investigating the feeding ecology of these species. Stable isotope and signature fatty acid analyses of muscle tissue were used for the first time to examine assimilated diet of the reef manta ray Manta alfredi, and were compared with different zooplankton functional groups (i.e. near-surface zooplankton collected during manta ray feeding events and non-feeding periods, epipelagic zooplankton, demersal zooplankton and several different zooplankton taxa). Stable isotope ?15N values confirmed that the reef manta ray is a secondary consumer. This species had relatively high levels of docosahexaenoic acid (DHA) indicating a flagellate-based food source in the diet, which likely reflects feeding on DHA-rich near-surface and epipelagic zooplankton. However, high levels of ?6 polyunsaturated fatty acids and slightly enriched ?13C values in reef manta ray tissue suggest that they do not feed solely on pelagic zooplankton, but rather obtain part of their diet from another origin. The closest match was with demersal zooplankton, suggesting it is an important component of the reef manta ray diet. The ability to feed on demersal zooplankton is likely linked to the horizontal and vertical movement patterns of this giant planktivore. These new insights into the habitat use and feeding ecology of the reef manta ray will assist in the effective evaluation of its conservation needs.

Couturier, Lydie I. E.; Rohner, Christoph A.; Richardson, Anthony J.; Marshall, Andrea D.; Jaine, Fabrice R. A.; Bennett, Michael B.; Townsend, Kathy A.; Weeks, Scarla J.; Nichols, Peter D.

2013-01-01

427

Horizontal distribution of Fukushima-derived radiocesium in zooplankton in the northwestern Pacific Ocean  

NASA Astrophysics Data System (ADS)

The magnitude of the 9.0 Tohoku earthquake and the ensuing tsunami on 11 March 2011, inflicted heavy damage on the Fukushima Dai-ichi nuclear power plant (FNPP1). Fission products were emitted, falling over a broad range in the Northern Hemisphere, and water contaminated with radionuclides leaked into the ocean. In this study, we described the horizontal distribution of the Fukushima-derived radiocesium in zooplankton and in seawater in the western North Pacific Ocean (500-2100 km from the FNPP1) 10 months after the accident. 134Cs and 137Cs were detected in zooplankton and seawater from all the stations. Because of its short half-life, the 134Cs detected in our samples could only be derived from the FNPP1 accident. The highest 137Cs activity in zooplankton was the same order of magnitude as it was one month after the accident, and average activity was one or two orders of magnitude higher than 137Cs activities observed before the accident around Japan. Horizontally, the radiocesium activity concentrations in zooplankton were high at around 25° N while those in surface seawater were high at around the transition area between the Kuroshio and the Oyashio currents (36-40° N). We observed subsurface radiocesium maxima in density range of the North Pacific Subtropical Mode Water and the occurrence of many diel vertical migratory zooplankton. These suggested that the high activity concentrations in the subtropical zooplankton at around 25° N were connected to the subsurface radiocesium and active vertical migration of zooplankton. However, the high activity concentrations of radiocesium in subsurface seawater did not necessarily correlate with the higher radiocesium activity in zooplankton. Activity concentrations of radiocesium in zooplankton might be influenced not only by the environmental radiocesium activity concentrations but also by other factors, which are still unknown.

Kitamura, M.; Kumamoto, Y.; Kawakami, H.; Cruz, E. C.; Fujikura, K.

2013-08-01

428

A lumped discrete population balance model for shear flocculation—model development  

Microsoft Academic Search

In the shear flocculation process, flocculation of ultrafine (size In this paper, a lumped discrete population balance model is presented considering both processes of coalescence and breakage of flocs. A method is also proposed to convert discrete kernels to lumped discrete kernels by satisfying the constraints on them. The numerical solution of the model is compared with some special analytical

D. P. Patil; J. R. G. Andrews; P. H. T. Uhlherr

1997-01-01

429

Nuisance Source Population Modeling for Radiation Detection System Analysis  

SciTech Connect

A major challenge facing the prospective deployment of radiation detection systems for homeland security applications is the discrimination of radiological or nuclear 'threat sources' from radioactive, but benign, 'nuisance sources'. Common examples of such nuisance sources include naturally occurring radioactive material (NORM), medical patients who have received radioactive drugs for either diagnostics or treatment, and industrial sources. A sensitive detector that cannot distinguish between 'threat' and 'benign' classes will generate false positives which, if sufficiently frequent, will preclude it from being operationally deployed. In this report, we describe a first-principles physics-based modeling approach that is used to approximate the physical properties and corresponding gamma ray spectral signatures of real nuisance sources. Specific models are proposed for the three nuisance source classes - NORM, medical and industrial. The models can be validated against measured data - that is, energy spectra generated with the model can be compared to actual nuisance source data. We show by example how this is done for NORM and medical sources, using data sets obtained from spectroscopic detector deployments for cargo container screening and urban area traffic screening, respectively. In addition to capturing the range of radioactive signatures of individual nuisance sources, a nuisance source population model must generate sources with a frequency of occurrence consistent with that found in actual movement of goods and people. Measured radiation detection data can indicate these frequencies, but, at present, such data are available only for a very limited set of locations and time periods. In this report, we make more general estimates of frequencies for NORM and medical sources using a range of data sources such as shipping manifests and medical treatment statistics. We also identify potential data sources for industrial source frequencies, but leave the task of estimating these frequencies for future work. Modeling of nuisance source populations is only useful if it helps in understanding detector system performance in real operational environments. Examples of previous studies in which nuisance source models played a key role are briefly discussed. These include screening of in-bound urban traffic and monitoring of shipping containers in transit to U.S. ports.

Sokkappa, P; Lange, D; Nelson, K; Wheeler, R

2009-10-05

430

Yunnan-III models for evolutionary population synthesis  

NASA Astrophysics Data System (ADS)

We build the Yunnan-III evolutionary population synthesis (EPS) models by using the mesa stellar evolution code, BaSeL stellar spectra library and the initial mass functions (IMFs) of Kroupa and Salpeter, and present colours and integrated spectral energy distributions (ISEDs) of solar-metallicity stellar populations (SPs) in the range of 1 Myr to 15 Gyr. The main characteristic of the Yunnan-III EPS models is the usage of a set of self-consistent solar-metallicity stellar evolutionary tracks (the masses of stars are from 0.1 to 100 M?). This set of tracks is obtained by using the state-of-the-art mesa code. mesa code can evolve stellar models through thermally pulsing asymptotic giant branch (TP-AGB) phase for low- and intermediate-mass stars. By comparisons, we confirm that the inclusion of TP-AGB stars makes the V - K, V - J and V - R colours of SPs redder and the infrared flux larger at ages log(t/yr) ? 7.6 [the differences reach the maximum at log(t/yr) ˜ 8.6, ˜0.5-0.2 mag for colours, approximately two times for K-band flux]. We also find that the colour-evolution trends of Model with-TPAGB at intermediate and large ages are similar to those from the starburst99 code, which employs the Padova-AGB stellar library, BaSeL spectral library and the Kroupa IMF. At last, we compare the colours with the other EPS models comprising TP-AGB stars (such as CB07, M05, V10 and POPSTAR), and find that the B - V colour agrees with each other but the V-K colour shows a larger discrepancy among these EPS models [˜1 mag when 8 ? log(t/yr) ? 9]. The stellar evolutionary tracks, isochrones, colours and ISEDs can be obtained on request from the first author or from our website (http://www1.ynao.ac.cn/~zhangfh/). Using the isochrones, you can build your EPS models. Now the format of stellar evolutionary tracks is the same as that in the starburst99 code; you can put them into the starburst99 code and get the SP's results. Moreover, the colours involving other passbands or on other systems (e.g. HST F439W - F555W colour on AB system) can also be obtained on request.

Zhang, F.; Li, L.; Han, Z.; Zhuang, Y.; Kang, X.

2013-02-01

431

An assessment of integrated population models: bias, accuracy, and violation of the assumption of independence  

Microsoft Academic Search

Understanding population dynamics requires accurate estimates of demo- graphic rates. Integrated population models combine demographic and survey data into a single, comprehensive analysis and provide more coherent estimates of vital rates. Integrated population models rely on the assumption that different data sets are independent, which is frequently violated in practice. Moreover, the precision that can be gained using integrated modeling

Fitsum Abadi; Olivier Gimenez; Raphaël Arlettaz; Michael Schaub

2010-01-01

432

R- And K-Selection in a Completely Chaotic Population Model.  

National Technical Information Service (NTIS)

A model of discrete-generations population dynamics originally due to M. H. Williamson is analyzed. In this model, the negative effect of population density acts suddenly and completely as the population size passes a threshold. The model almost always yi...

J. Felsenstein

1978-01-01

433

Evaluation of a system to automatically sample zooplankton from the discharge of dams  

SciTech Connect

Automatic plankton samplers installed at two dams on the Connecticut River continuously monitored crustacean zooplankton from October 1977 through 1979 and allowed a significant reduction in man-hours involved in an extensive sampling program. Automatic samplers efficiently sampled most species and size classes of crustacean zooplankton in a similar, but not consistently identical manner as a commonly used towed-net plankton sampler. The smallest sized zooplankton were captured more efficiently than the largest. Mesh selection and sampler avoidance exerted different influences on automatic samplers and towed nets. Future use of the samplers and direct comparison of results to results obtained by other methods was supported.

Rosen, R.A.

1982-02-01

434

Modeling expression quantitative trait loci in data combining ethnic populations  

Microsoft Academic Search

BACKGROUND: Combining data from different ethnic populations in a study can increase efficacy of methods designed to identify expression quantitative trait loci (eQTL) compared to analyzing each population independently. In such studies, however, the genetic diversity of minor allele frequencies among populations has rarely been taken into account. Due to the fact that allele frequency diversity and population-level expression differences

Ching-Lin Hsiao; Ie-Bin Lian; Ai-Ru Hsieh; Cathy S. J. Fann

2010-01-01

435

POPULATION BOTTLENECKS AND NONEQUILIBRIUM MODELS IN POPULATION GENETICS. 111. GENIC HOMOZYGOSITY IN POPULATIONS WHICH EXPERIENCE PERIODIC BOTTLENECKS  

Microsoft Academic Search

The amount of variability in a population that experiences repeated restric- tions in population size has been calculated. The restrictions in size occur cyclically with a fixed cycle length. Analytical formulas for describing the gene identity at any specific time in the expanded and restricted phases of the cycle, and for the average and second moment of the gene identity,

PAUL A. FUERSTt

436

A comparison of carbon-specific respiration rates in gelatinous and non-gelatinous zooplankton: A search for general rules in zooplankton metabolism  

NASA Astrophysics Data System (ADS)

Using 470 data from the literature the dry weight-specific respiration rates of gelatinous zooplankton (cnidarians, ctenophores and salps) and non-gelatinous zooplankton (mainly crustacea) were converted to carbon-specific values. The resulting carbon-specific respiration rates showed no significant differences between the two groups of zooplankton, indicating similar oxygen requirements per gram of carbon biomass. From this finding, it can be suggested that the differences in the rates of oxygen consumption measured in the two types of zooplankton in the sea can be explained by the carbon biomass ratio between gelatinous and non-gelatinous zooplankton. Furthermore, the low rate of metabolism of gelatinous species compared with that of non-gelatinous animals of the same volume can be attributed predominantly to the relatively low organic matter content in the former. It is recommended that all weight-specific metabolism rates be expressed using carbon as body mass unit (e.g. mg O2 gC-1 d-1) which enables more accurate comparisons between individuals exhibiting different dry weight/carbon ratios.

Schneider, G.

1992-12-01

437

Effects of zooplankton herbivory on biomarker proxy records  

NASA Astrophysics Data System (ADS)

The stable carbon isotopic compositions of cholesterol, generally the most dominant sterol in the copepod Temora, bears the ?13C "signature" of its dietary precursor sterol when fed on Isochrysis galbana and Rhodomonas sp. The ?13C of cholesterol in the faecal pellets released from Temora longicornis fed on Rhodomonas sp. is identical to the ?13C of the sterols in the diet, indicating that no significant carbon isotopic fractionation effects occur when the copepod modifies eukaryotic precursor sterols to cholesterol. Furthermore, the ratio of long-chain alkenones and their stable carbon isotopic compositions in I. galbana were identical to those egested in faecal material. Thus Zooplankton herbivory does not invalidate the use of these alkenones as a proxy for sea surface temperature and pCO2.

Grice, Kliti; Klein Breteler, Wim C. M.; Schouten, Stefan; Grossi, Vincent; de Leeuw, Jan W.; Sinninghe Damsté, Jaap S.

1998-12-01

438

Benthic origins of zooplankton: An environmentally determined macroevolutionary effect  

NASA Astrophysics Data System (ADS)

Zooplankton show a unique pattern of evolution with successive waves of invasion into the water column from the benthos. We have found that 18 of 21 planktonic groups whose ancestry can be traced originated in the benthos. New recruits have survived and radiated if preadapted to remain in the plankton, but no major clades have evolved there (with the possible exception of some protists). The innovative steps into the planktic realm do not coincide with major global events such as mass extinctions. Recruitment into the plankton can occur either at the larval stage or in adulthood. No groups have returned to a benthic mode of life from a planktic one, except possibly some of the cnidarians. This unusual pattern of evolution, a one-way track into a particular environment, demonstrates the profound effect of the ecosystem on large-scale patterns and processes of evolution.

Rigby, Susan; Milsom, Clare

1996-01-01

439

Factors affecting zooplankton feeding by the sea anemone Aiptasia pallida  

NASA Astrophysics Data System (ADS)

Effects of various treatments on prey capture, prey ingestion and ingestion time of individual Artemia salina nauplii by the sea anemone Aiptasia pallida Verrill were studied in the laboratory. Exposure to crude Artemia homogenate, 5 × 10-4 M reduced glutathione or 5 × 10-4 M proline significantly decreased the number of Artemia that were captured and ingested but had no significant effect on the ingestion time of individual Artemia. Multiple captures increased the total ingestion time but decreased ingestion time per prey item. Results suggest that, under these conditions, the prey capture phase of zooplankton feeding was somewhat distinct from the ingestion phase since chemical stimuli that significantly reduced prey capture had no significant effect on ingestion time.

Clayton, William S.

1986-03-01

440

Explaining the Linguistic Diversity of Sahul Using Population Models  

PubMed Central

The region of the ancient Sahul continent (present day Australia and New Guinea, and surrounding islands) is home to extreme linguistic diversity. Even apart from the huge Austronesian language family, which spread into the area after the breakup of the Sahul continent in the Holocene, there are hundreds of languages from many apparently unrelated families. On each of the subcontinents, the generally accepted classification recognizes one large, widespread family and a number of unrelatable smaller families. If these language families are related to each other, it is at a depth which is inaccessible to standard linguistic methods. We have inferred the history of structural characteristics of these languages under an admixture model, using a Bayesian algorithm originally developed to discover populations on the basis of recombining genetic markers. This analysis identifies 10 ancestral language populations, some of which can be identified with clearly defined phylogenetic groups. The results also show traces of early dispersals, including hints at ancient connections between Australian languages and some Papuan groups (long hypothesized, never before demonstrated). Systematic language contact effects between members of big phylogenetic groups are also detected, which can in some cases be identified with a diffusional or substrate signal. Most interestingly, however, there remains striking evidence of a phylogenetic signal, with many languages showing negligible amounts of admixture.

Reesink, Ger; Singer, Ruth; Dunn, Michael

2009-01-01

441

Toward population management in an integrated care model.  

PubMed

Under the Patient Protection and Affordable Care Act of 2010, accountable care organizations (ACOs) will be the primary mechanism for achieving the dual goals of high-quality patient care at managed per capita costs. To achieve these goals in the newly emerging health care environment, the nephrology community must plan for and direct integrated delivery and coordination of renal care, focusing on population management. Even though the ESRD patient population is a complex group with comorbid conditions that may confound integration of care, the nephrology community has unique experience providing integrated care through ACO-like programs. Specifically, the recent ESRD Management Demonstration Project sponsored by the Centers for Medicare & Medicaid Services and the current ESRD Prospective Payment System with it Quality Incentive Program have demonstrated that integrated delivery of renal care can be accomplished in a manner that provides improved clinical outcomes with some financial margin of savings. Moving forward, integrated renal care will probably be linked to provider performance and quality outcomes measures, and clinical integration initiatives will share several common elements, namely performance-based payment models, coordination of communication via health care information technology, and development of best practices for care coordination and resource utilization. Integration initiatives must be designed to be measured and evaluated, and, consistent with principles of continuous quality improvement, each initiative will provide for iterative improvements of the initiative. PMID:23539229

Maddux, Franklin W; McMurray, Stephen; Nissenson, Allen R

2013-03-28

442

Complex Transition to Cooperative Behavior in a Structured Population Model  

PubMed Central

Cooperation plays an important role in the evolution of species and human societies. The understanding of the emergence and persistence of cooperation in those systems is a fascinating and fundamental question. Many mechanisms were extensively studied and proposed as supporting cooperation. The current work addresses the role of migration for the maintenance of cooperation in structured populations. This problem is investigated in an evolutionary perspective through the prisoner's dilemma game paradigm. It is found that migration and structure play an essential role in the evolution of the cooperative behavior. The possible outcomes of the model are extinction of the entire population, dominance of the cooperative strategy and coexistence between cooperators and defectors. The coexistence phase is obtained in the range of large migration rates. It is also verified the existence of a critical level of structuring beyond that cooperation is always likely. In resume, we conclude that the increase in the number of demes as well as in the migration rate favor the fixation of the cooperative behavior.

Miranda, Luciano; de Souza, Adauto J. F.; Ferreira, Fernando F.; Campos, Paulo R. A.

2012-01-01

443

Modeling population exposures to outdoor sources of hazardous air pollutants.  

PubMed

Accurate assessment of human exposures is an important part of environmental health effects research. However, most air pollution epidemiology studies rely upon imperfect surrogates of personal exposures, such as information based on available central-site outdoor concentration monitoring or modeling data. In this paper, we examine the limitations of using outdoor concentration predictions instead of modeled personal exposures for over 30 gaseous and particulate hazardous air pollutants (HAPs) in the US. The analysis uses the results from an air quality dispersion model (the ASPEN or Assessment System for Population Exposure Nationwide model) and an inhalation exposure model (the HAPEM or Hazardous Air Pollutant Exposure Model, Version 5), applied by the US. Environmental protection Agency during the 1999 National Air Toxic Assessment (NATA) in the US. Our results show that the total predicted chronic exposure concentrations of outdoor HAPs from all sources are lower than the modeled ambient concentrations by about 20% on average for most gaseous HAPs and by about 60% on average for most particulate HAPs (mainly, due to the exclusion of indoor sources from our modeling analysis and lower infiltration of particles indoors). On the other hand, the HAPEM/ASPEN concentration ratio averages for onroad mobile source exposures were found to be greater than 1 (around 1.20) for most mobile-source related HAPs (e.g. 1, 3-butadiene, acetaldehyde, benzene, formaldehyde) reflecting the importance of near-roadway and commuting environments on personal exposures to HAPs. The distribution of the ratios of personal to ambient concentrations was found to be skewed for a number of the VOCs and reactive HAPs associated with major source emissions, indicating the importance of personal mobility factors. We conclude that the increase in personal exposures from the corresponding predicted ambient levels tends to occur near locations where there are either major emission sources of HAPs or when individuals are exposed to either on- or nonroad sources of HAPs during their daily activities. These findings underscore the importance of applying exposure-modeling methods, which incorporate information on time-activity, commuting, and exposure factors data, for the purposes of assigning exposures in air pollution health studies. PMID:17878926