These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Biomass, Growth, and Development of Populations of Herbivorous Zooplankton in the Southeastern Bering Sea During Spring.  

National Technical Information Service (NTIS)

Two distinct communities of herbivorous zooplankton, separated by an oceanographic front, inhabit the continental shelf and slope of the southeastern Bering Sea during spring. The community over the outer shelf and slope is dominated by populations of lar...

J. Vidal, S. L. Smith

1985-01-01

2

Large nonlethal effects of an invasive invertebrate predator on zooplankton population growth rate.  

PubMed

We conducted a study to determine the contribution of lethal and nonlethal effects to a predator's net effect on a prey's population growth rate in a natural setting. We focused on the effects of an invasive invertebrate predator, Bythotrephes longimanus, on zooplankton prey populations in Lakes Michigan and Erie. Field data taken at multiple dates and locations in both systems indicated that the prey species Daphnia mendotae, Daphnia retrocurva, and Bosmina longirostris inhabited deeper portions of the water column as Bythotrephes biomass increased, possibly as an avoidance response to predation. This induced migration reduces predation risk but also can reduce birth rate due to exposure to cooler temperatures. We estimated the nonlethal (i.e., resulting from reduced birth rate) and lethal (i.e., consumptive) effects of Bythotrephes on D. mendotae and Bosmina longirostris. These estimates used diel field survey data of the vertical gradient of zooplankton prey density, Bythotrephes density, light intensity, and temperature with growth and predation rate models derived from laboratory studies. Results indicate that nonlethal effects played a substantial role in the net effect of Bythotrephes on several prey population growth rates in the field, with nonlethal effects on the same order of magnitude as or greater (up to 10-fold) than lethal effects. Our results further indicate that invasive species can have strong nonlethal, behaviorally based effects, despite short evolutionary coexistence with prey species. PMID:17479758

Pangle, Kevin L; Peacor, Scott D; Johannsson, Ora E

2007-02-01

3

LARGE NONLETHAL EFFECTS OF AN INVASIVE INVERTEBRATE PREDATOR ON ZOOPLANKTON POPULATION GROWTH RATE  

Microsoft Academic Search

We conducted a study to determine the contribution of lethal and nonlethal effects to a predator's net effect on a prey's population growth rate in a natural setting. We focused on the effects of an invasive invertebrate predator, Bythotrephes longimanus ,o n zooplankton prey populations in Lakes Michigan and Erie. Field data taken at multiple dates and locations in both

Kevin L. Pangle; Scott D. Peacor; Ora E. Johannsson

2007-01-01

4

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

5

Estimation of mortality for stage-structured zooplankton populations: What is to be done?  

NASA Astrophysics Data System (ADS)

Estimation of zooplankton mortality rates in field populations is a challenging task that some contend is inherently intractable. This paper examines several of the objections that are commonly raised to efforts to estimate mortality. We find that there are circumstances in the field where it is possible to sequentially sample the same population and to resolve biologically caused mortality, albeit with error. Precision can be improved with sampling directed by knowledge of the physical structure of the water column, combined with adequate sample replication. Intercalibration of sampling methods can make it possible to sample across the life history in a quantitative manner. Rates of development can be constrained by laboratory-based estimates of stage durations from temperature- and food-dependent functions, mesocosm studies of molting rates, or approximation of development rates from growth rates, combined with the vertical distributions of organisms in relation to food and temperature gradients. Careful design of field studies guided by the assumptions of specific estimation models can lead to satisfactory mortality estimates, but model uncertainty also needs to be quantified. We highlight additional issues requiring attention to further advance the field, including the need for linked cooperative studies of the rates and causes of mortality of co-occurring holozooplankton and ichthyoplankton.

Ohman, Mark D.

2012-05-01

6

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

7

The acoustic water column profiler: a tool for long-term monitoring of zooplankton populations  

Microsoft Academic Search

Measuring acoustic backscatter in the water column is a low-cost, reliable method for examining the long-term behaviour and distribution of zooplankton populations. Backscatter at acoustic frequencies above 20 kHz is useful for profiling those quantities, which, when tracked over long periods of time, can provide a valuable contribution to understanding and monitoring the state of marine ecosystems. The Water Column

D. D. Lemon; J. F. R. Gower; M. R. Clarke

2001-01-01

8

Role of Zooplankton Diversity in Vibrio cholerae Population Dynamics and in the Incidence of Cholera in the Bangladesh Sundarbans ?  

PubMed Central

Vibrio cholerae, a bacterium autochthonous to the aquatic environment, is the causative agent of cholera, a severe watery, life-threatening diarrheal disease occurring predominantly in developing countries. V. cholerae, including both serogroups O1 and O139, is found in association with crustacean zooplankton, mainly copepods, and notably in ponds, rivers, and estuarine systems globally. The incidence of cholera and occurrence of pathogenic V. cholerae strains with zooplankton were studied in two areas of Bangladesh: Bakerganj and Mathbaria. Chitinous zooplankton communities of several bodies of water were analyzed in order to understand the interaction of the zooplankton population composition with the population dynamics of pathogenic V. cholerae and incidence of cholera. Two dominant zooplankton groups were found to be consistently associated with detection of V. cholerae and/or occurrence of cholera cases, namely, rotifers and cladocerans, in addition to copepods. Local differences indicate there are subtle ecological factors that can influence interactions between V. cholerae, its plankton hosts, and the incidence of cholera. PMID:21764957

de Magny, Guillaume Constantin; Mozumder, Pronob K.; Grim, Christopher J.; Hasan, Nur A.; Naser, M. Niamul; Alam, Munirul; Sack, R. Bradley; Huq, Anwar; Colwell, Rita R.

2011-01-01

9

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

10

Response of predatory zooplankton populations to the experimental acidification of Little Rock Lake, Wisconsin  

SciTech Connect

To assess the effects of lake acidification on large predatory zooplankton, the authors monitored population levels of four limnetic taxa for 6 years in a lake with two basins, one of which was experimentally acidified (2 years at each of three levels: pH 5.6, 5.2 and 4.7). Concentrations of phantom midge (Chaoborus spp.), the most abundant large predator, remained similar in the treatment and reference basins until the fourth year (pH 5.2) when they increased in the treatment basin. In contrast, Epischura lacustris and Leptodora kindtii disappeared from limnetic samples, and water mites declined to near zero upon acidification. Treatment basin populations of E. lacustris declined sharply during the second year of acidification. The nature of the decline suggested sensitivity of an early life stage during the first year at pH 5.6. Leptodora kindtii showed no population response at pH 5.6, but declined to essentially zero at pH 5.2. Treatment basin populations of water mites fluctuated until declining in the fifth and sixth years (pH 4.7). These changes indicate a variety of direct and indirect responses to lake acidification.

Sierszen, M.E.; Frost, T.M.

1993-01-01

11

Exploring a first-principles-based model for zooplankton respiration  

Microsoft Academic Search

accepted version at constant temperature (T )i sR = i0M 0.75 , where i0 is a constant. We argue that, for zooplankton, a F-based, O2- consuming algorithm is more consistent with the cause of respiration. Our point: although biomass is related to respiration, the first- principles cause of respiration is ETS, because it controls O2 consumption. Biomass itself is indirectly

Ted T. Packard; May Gomez

2008-01-01

12

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...

13

Simulated herring growth responses in the Northeastern Pacific to historic temperature and zooplankton conditions generated by the 3-dimensional NEMURO nutrient–phytoplankton–zooplankton model  

Microsoft Academic Search

The infrequent occurrence of climate regime shifts and the long-lived life history of many harvested fish species imply that quantitative understanding of the effects of climate shifts on fish will require long-term data spanning decades. We use the output of the 3-dimensional (3D) NEMURO nutrient–phytoplankton–zooplankton model applied to the Northern Pacific as input to a Pacific herring (Clupea pallasi) bioenergetics

Kenneth A. Rose; Francisco E. Werner; Bernard A. Megrey; Maki Noguchi Aita; Yasuhiro Yamanaka; Douglas E. Hay; Jake F. Schweigert; Matthew Birch Foster

2007-01-01

14

Is there enough zooplankton to feed forage fish populations off Peru? An acoustic (positive) answer  

NASA Astrophysics Data System (ADS)

The Northern Humboldt Current system (NHCS) produces more fish per unit area than any other region in the world. Although the system produces enough macrozooplankton to sustain its high production of forage fish, the paucity of information on macrozooplankton hampers research into the system. In this study, we estimated the biomass of the epipelagic crustacean macrozooplankton from the NHCS during both austral summer and spring 2005. To do this, we developed a bi-frequency acoustic method and extracted high-resolution information on the biomass and the patterns of distribution of crustacean macrozooplankton, fish and other marine compartments. We found that, although macrozooplankton comprises a number of distinct organisms, the euphausiids were the zooplankton group that better fitted the patterns from independent net sampling zooplankton data. Also, the similarities between the nocturnal patterns of size and biomass macrozooplankton distribution from this study and the known patterns of euphausiids, in particular Euphausia mucronata, suggest that euphausiids were the main constituent of the estimated nocturnal acoustic macrozooplankton biomass even if other organisms such as large copepods may have contributed considerably to the macrozooplankton biomass. The total macrozooplankton biomass was estimated to about 105 g m -2, i.e., two to five times more than previous estimates. This direct biomass estimation of macrozooplankton is in agreement with the new findings in trophic ecology indicating that forage fish consume mainly macrozooplankton. This high biomass also supports the current hypotheses explaining the NHCS high fish production. Using the method, we are able to revisit present-day and historical acoustic databases and extract high-resolution data on macrozooplankton, a key ecological compartment of the ecosystem. Since zooplankton is the link between the physically driven primary producers and the biologically driven tertiary consumers, this information is essential to achieve a mechanistic understanding of the system, from physics to top predators.

Ballón, Michael; Bertrand, Arnaud; Lebourges-Dhaussy, Anne; Gutiérrez, Mariano; Ayón, Patricia; Grados, Daniel; Gerlotto, François

2011-12-01

15

Effect of demographic noise in a phytoplankton-zooplankton model of bloom dynamics.  

PubMed

An extension of the Truscott-Brindley model [Bull. Math. Biol. 56, 981 (1994)] is derived to account for the effect of demographic fluctuations. In the presence of seasonal forcing and sufficiently shallow water conditions, the fluctuations induced by the discreteness of the zooplankton component appear sufficient to cause switching between the bloom and no-bloom cycles predicted at the mean-field level by the model. The destabilization persists in the thermodynamic limit of a water basin infinitely extended in the horizontal direction. PMID:23410364

Olla, Piero

2013-01-01

16

The effect of Kingston Harbour outflow on the zooplankton populations of Hellshire, south-east coast, Jamaica  

NASA Astrophysics Data System (ADS)

Zooplankton sampling was conducted at 16 stations located at the mouth of Kingston Harbour and throughout the Hellshire area from November 1985 to March 1987. Parameters examined included total biomass, total numbers and numbers of numerically important zooplankton species. Maximum values were recorded west of the Harbour mouth (station 1) and these gradually decreased with distance from the Harbour especially at the 'offshore' stations, producing a gradient effect in this area. Mean biomass and abundance for the period sampled ranged from 14 g m -3 and 16 313 individuals m -3 at the western side of the Harbour mouth to 0·4 g m -3 and 172 individuals m -3 at Wreck Reef. Stations within the bays of Hellshire occasionally had values similar to those recorded at the mouth of Kingston Harbour and here there was less evidence of a gradual decline. Considerable monthly fluctuation occurred in these parameters but there was no discernible seasonal pattern. Copepods dominated the population at most stations and the sergestid Lucifer faxoni also proved an important member at the western Harbour mouth station.

Lindo, Mona K.

1991-06-01

17

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

18

EXPERIMENTAL EVIDENCE FOR DENSITY-DEPENDENT EFFECTS AND THE IMPORTANCE OF ALGAL PRODUCTION IN DETERMINING POPULATION GROWTH RATES OF RIVERINE ZOOPLANKTON  

Microsoft Academic Search

Food limitation effects on life history traits of lake zooplankton have been well documented but few studies have examined linkages between population growth rates and food resources in riverine environments. In rivers, allochthonous inputs of par- ticulate organic matter may mitigate food limitation effects allowing density-independent mechanisms associated with washout (discharge) and feeding interference (turbidity) to assume greater importance. We

D. L. GUELDA; R. W. KOCH; J. D. JACKa; P. A. BUKAVECKASa

19

Implementation of the zooplankton functional response in plankton models: State of the art, recent challenges and future directions  

E-print Network

Review Implementation of the zooplankton functional response in plankton models: State of the art April 2012 a b s t r a c t The conventional way of describing grazing in plankton models is based and grazer distributions (plankton patchiness) across time and space scales raise questions as to the exis

Poggiale, Jean-Christophe

20

Living on the edge: Populations of two zooplankton species living closer to agricultural fields are more resistant to a common insecticide.  

PubMed

Ecological communities across the globe are exposed to diverse natural and anthropogenic stressors and disturbances that can lead to community-wide impacts. Contaminants are a group of anthropogenic disturbances that are ubiquitous in the environment and can trigger trophic cascades, increased susceptibility to pathogens, reduced biodiversity, and altered ecosystems. In these ecosystems, substantial attention has been given to evolved resistance in targeted pest species, but little attention has been given to the evolution of resistance in nontarget species in nature. For the present study, the authors used laboratory toxicity tests to determine if 2 common, co-occurring species of freshwater zooplankton (Simocephalus vetulus and Daphnia pulex) showed population-level variation in sensitivity to a common insecticide (chlorpyrifos). For both species, it was found that populations living near agricultural fields-a proxy for pesticide use-were more resistant to chlorpyrifos than populations collected from ponds far from agriculture. This finding is consistent with the evolution of resistance to pesticides. To the authors' knowledge, only 1 previous study (using Daphnia magna) has demonstrated this relationship. Collectively, these results suggest that evolved resistance may be common in zooplankton populations located near agriculture. Moreover, because zooplankton play a key role in aquatic food webs, it is expected that population variation in resistance would dramatically alter aquatic food webs, particularly with exposure to low concentrations of insecticides. Environ Toxicol Chem 2014;33:2835-2841. © 2014 SETAC. PMID:25220688

Bendis, Randall J; Relyea, Rick A

2014-12-01

21

A New Trait-Based Auto-Emergent Model for Zooplankton and Confrontation with Size-Structured Observations from the Bay of Biscay  

NASA Astrophysics Data System (ADS)

Zooplankton plays a significant role in marine ecosystems bridging the gap between primary producers and top consumers and interacting with the particle flux through complex dynamics. Scarcity of data and complexity of observing zooplankton make it difficult to integrate it in biogeochemical models where it is most often formulated in a simpler manner, i.e. classic box models with usually two compartments (micro and meso/macro zooplankton). Recent advances in automatic sizing, counting and identification allow better estimates of the dynamics and distribution of zooplankton, notably through the measurement of its size structure, and for zooplankton size matter. Most zooplankton physiological rates as well as predator:prey interactions can be significantly relied to individuals size through allometric relations. Such size-dependency was used in recent models. Yet, these models were neither confronted to observations nor integrated in 3D biogeochemical models. Here we propose a newly developed model of zooplankton dynamics based on size-dependent allometric relations but which allows various diet types regardless of the size. A size and a degree of herbivory is randomly drawn for each zooplankton species generated within the model (up to 400 here, limited by actual computational costs). By generating random degree of herbivory zooplankton species of same size could have various diet (from herbivore to carnivore). Other parameters leading to various reproductive strategies or vertical migration could also be drawn randomly (not tested here). The zooplankton model is coupled to the 3D biogeochemical model MARS3D on a test case representing a simplified view of the Bay of Biscay (i.e., continental shelf, estuary, tides). The model shows auto-emergent properties with the selection of size/diet most adapted to local conditions (here offshore vs. coastal, estuary…). Then, patterns of the modeled size-structure of the zooplankton are confronted to the ones observed during Spring-time cruises in the Bay of Biscay. The usefulness of the proposed zooplankton model for large scale biogeochemical models is further discussed.

Vandromme, Pieter; Sourisseau, Marc; Huret, Martin

2013-04-01

22

Measurement of Zooplankton Biomass by Carbon Analysis for Application in Sound Scattering Models.  

National Technical Information Service (NTIS)

Estimates of zooplankton biomass were made by use of a LECO Carbon Analyzer. The methodology developed in this study is a rapid, precise and accurate measurement of total carbon. Casein and benzoic acid were used interchangeably as standards. The techniqu...

J. C. Radney

1974-01-01

23

The effect of spatial and temporal variation in zooplankton concentrations on larval cod growth and survival on Georges Bank: a sensitivity analysis based on modelling and observations  

Microsoft Academic Search

The U.S. GLOBEC Georges Bank\\/NW Atlantic program has generated an unprecedented body of data on vital rates, abundance and distribution of zooplankton and ichthyoplankton on Georges Bank. Concurrent with the data-gathering activity has been the development and refinement of a coupled physical-trophodynamic model describing growth, survival and distribution of larval cod and haddock. Using the trophodynamic model and zooplankton data

Pavillon Vachon

24

Zooplankton interactions with toxic phytoplankton: Some implications for food web studies and algal defence strategies of feeding selectivity behaviour, toxin dilution and phytoplankton population diversity  

NASA Astrophysics Data System (ADS)

This study focuses on the interactions between toxic phytoplankton and zooplankton grazers. The experimental conditions used are an attempt to simulate situations that have, so far, received little attention. We presume the phytoplankton community to be a set of species where a population of a toxic species is intrinsically diverse by the presence of coexisting strains with different toxic properties. The other species in the community may not always be high-quality food for herbivorous zooplankton. Zooplankton populations may have developed adaptive responses to sympatric toxic phytoplankton species. Zooplankton grazers may perform a specific feeding behaviour and its consequences on fitness will depend on the species ingested, the effect of toxins, and the presence of mechanisms of toxin dilution and compensatory feeding. Our target species are a strain of the dinoflagellate Alexandrium minutum and a sympatric population of the copepod Acartia clausi. Mixed diets were used with two kinds of A. minutum cells: non-toxic and toxic. The flagellate Rhodomonas baltica and the non-toxic dinoflagellate Alexandrium tamarense were added as accompanying species. The effect of each alga was studied in separate diets. The toxic A. minutum cells were shown to have negative effects on egg production, hatching success and total reproductive output, while, in terms of its effect on fitness, the non-toxic A. minutum was the best quality food offered. R. baltica and A. tamarense were in intermediate positions. In the mixed diets, copepods showed a strong preference for toxic A. minutum cells and a weaker one for A. tamarense cells, while non-toxic A. minutum was slightly negatively selected and R. baltica strongly negatively selected. Although the level of toxins accumulated by copepods was very similar, in both the diet with only toxic A. minutum cells and in the mixed diet, the negative effects on fitness in the mixed diet could be offset by toxin dilution mechanisms. The implications of these findings are the fact that mesozooplankton may not play an important role in phytoplankton blooms development. Phytoplankton endotoxin production does not seem to be an evolutionary stable strategy as a defence against some herbivores.

Barreiro, A.; Guisande, C.; Maneiro, I.; Vergara, A. R.; Riveiro, I.; Iglesias, P.

2007-11-01

25

Hydroacoustic estimation of zooplankton biomass at two shoal complexes in the Apostle Islands Region of Lake Superior  

USGS Publications Warehouse

Hydroacoustics can be used to assess zooplankton populations, however, backscatter must be scaled to be biologically meaningful. In this study, we used a general model to correlate site-specific hydroacoustic backscatter with zooplankton dry weight biomass estimated from net tows. The relationship between zooplankton dry weight and backscatter was significant (p < 0.001 ) and explained 76% of the variability in the dry weight data. We applied this regression to hydroacoustic data collected monthly in 2003 and 2004 at two shoals in the Apostle Island Region of Lake Superior. After applying the regression model to convert hydroacoustic backscatter to zooplankton dry weight biomass, we used geostatistics to analyze the mean and variance, and ordinary kriging to create spatial zooplankton distribution maps. The mean zooplankton dry weight biomass estimates from plankton net tows and hydroacoustics were not significantly different (p = 0.19) but the hydroacoustic data had a significantly lower coefficient of variation (p < 0.001). The maps of zooplankton distribution illustrated spatial trends in zooplankton dry weight biomass that were not discernable from the overall means.

Holbrook, B.V.; Hrabik, T.R.; Branstrator, D.K.; Yule, D.L.; Stockwell, J.D.

2006-01-01

26

Model-based acoustic characterization and classification of irregular-shaped targets: Application to fisheries and zooplankton acoustics  

NASA Astrophysics Data System (ADS)

Acoustic scattering by fish and zooplankton is a complicated function of the geometrical and physical properties of the targets, as well as the environmental and sonar system parameters. The shape and anatomy of zooplankton vary significantly from taxa to taxa and their dominant scattering mechanisms can be completely different. As a result, the acoustic classification of such targets is extremely difficult and often nonunique. To reduce the ambiguity and nonuniqueness, a number of model-based methods are presented. These methods use the temporal, spatial, spectral, and statistical signatures of acoustical scattering signals and can be applied to a variety of acoustic systems, including narrow-band, broadband, and multifrequency systems. The methods also depend strongly on whether or not the targets are resolved. Individual targets with different shapes and material properties have their unique characteristics and can be classified acoustically in terms of their size, orientation, scattering mechanisms, as well as their material properties. Results of applying these methods to the laboratory and field data will be presented and analyzed. [Work supported by ONR, NSF, and the Comer Science and Education Foundation.

Chu, Dezhang; Stanton, Timothy K.; Wiebe, Peter H.

2002-11-01

27

Modelling the predation, growth and population dynamics of fish within a spatially-resolved shelf-sea ecosystem model  

Microsoft Academic Search

The development and analysis of a fish population module within the European Regional Seas Ecosystem Model (ERSEM) is described. Fixed predation rates on ERSEM zooplankton and zoobenthos, which may be used in place of this dynamic module of fish, are described also. The dynamic module is age-structured, with state variables for the number of individuals and their weight, the latter

A. D. Bryant; M. R. Heath; N. Broekhuizen; J. G. Ollason; W. S. C. Gurney; S. P. R. Greenstreet

1995-01-01

28

Incorporating complex foraging of zooplankton in models: the role of microscale processes in macroscale patterns  

E-print Network

.E., Brindley, J., 1994, "Ocean Plankton Populations as Excitable Media", (Bull. Math. Biol. 56) #12;Modelling) Consumption rate E of food by predators/grazers: ( ) ( ) 1 11 , FZtq BN BN tqE N i Ti N i TiTN = = = == , N -instantaneous consumption of i; T - averaging along the trajectory Functional Response h ( )TTTN ZPh

29

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

30

Latitudinal comparisons of equatorial Pacific zooplankton  

NASA Astrophysics Data System (ADS)

Zooplankton biomass and rates of ingestion, egestion and production in the equatorial Pacific Ocean along 140°W and 180° exhibit maximum values in the High-Nutrient Low-Chlorophyll (HNLC) zone associated with equatorial upwelling (5°S-5°N) as compared to the more oligotrophic regions to the north and south. Zooplankton biomass and rates are not usually highest on the equator, but increase "downstream" of the upwelling center as the zooplankton populations exhibit a delayed response to enhanced phytoplankton production. The vertical distribution of zooplankton biomass in the equatorial HNLC area tends to be concentrated in surface waters and is more uniform with depth in oligotrophic regions to the north and south of the equatorial upwelling zone. In general, the amount of mesozooplankton (>200 ?m) carbon biomass is approximately 25% of estimated phytoplankton biomass and 30% of bacterial biomass in the HNLC area of the equatorial Pacific Ocean. Zooplankton grazing on phytoplankton is low in the equatorial Pacific Ocean, generally <5% of the total chlorophyll-a standing stock grazed per day. Based on estimates of metabolic demand, it is apparent that zooplankton in the equatorial Pacific Ocean are omnivores, consuming primarily microzooplankton and detritus. Estimated zooplankton growth rates in the warm waters of the HNLC equatorial Pacific Ocean are high, ranging from 0.58 d -1 for 64-200 ?m zooplankton to 0.08 d -1 for 1000-2000 ?m zooplankton. Thus, the numerical and functional response of equatorial zooplankton to increases in phytoplankton production are more rapid than normally occurs in sub-tropical and temperate waters. Potential zooplankton fecal pellet production, estimated from metabolic demand, is approximately 1.6 times the estimated gravitational carbon flux at 150 m in the zone of equatorial upwelling (5°S-5°N) and 1.1 times the export flux in the more oligotrophic regions to the north and south. The active flux of carbon by diel migrant zooplankton in the HNLC zone is a minor fraction of the gravitational flux (2% at 140°W, 4% at 180°) but increases in the more oligotrophic regions to the north and south where there is a deeper mixed layer and a greater relative proportion of diel migrant zooplankton.

Roman, M. R.; Dam, H. G.; Le Borgne, R.; Zhang, X.

31

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

32

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

33

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.

34

Zooplankton mortality in 3D ecosystem modelling considering variable spatial-temporal fish consumptions in the North Sea  

NASA Astrophysics Data System (ADS)

We tested the feasibility of imposing mesozooplankton mortality into a 3D model based on estimated consumption rates of the dominant planktivorous fish in the North Sea-Kattegat area. The spatial biomass distribution of Atlantic herring (Clupea harengus), horse mackerel (Trachurus trachurus), Atlantic mackerel (Scomber scombrus), sandeel (Ammodytidae) and European sprat (Sprattus sprattus) was derived from quarterly scientific trawl surveys and Danish commercial catches. Spatio-temporal indices of mortality were created based on the estimated biomasses and ingestion rates from the literature. The fish larvae grazing pressure was obtained from a spatial, size-based larval community model. In this model, larvae, herring and sandeel were the most important fish predators on mesozooplankton, but these groups had different spatial and temporal (seasonal) distributions. Fish larvae were particularly dominant in the eastern and southern areas in early summer. Herring and sandeel had the highest consumption in the central and north-western areas and were more important in late summer. The fish index changed the perceived annual, seasonal and spatial patterns in modelled mesozooplankton biomass, production and mortality. In the present study, the index was kept relatively simple and can be further developed with respect to the description of fish as well carnivorous zooplankton ingestion rates. The data input required to create the fish index is (i) planktivorous fish stock biomasses and (ii) relative fish spawning distribution information and (iii) physics (ocean currents and temperatures) for the region and situation of interest. The fish index seems promising as a realistic mortality term for lower trophic levels in 3D ecosystem models in areas with available data on fish stocks to improve management of marine resources.

Maar, Marie; Rindorf, Anna; Møller, Eva Friis; Christensen, Asbjørn; Madsen, Kristine S.; van Deurs, Mikael

2014-05-01

35

Density-dependent mortality in an oceanic copepod population  

Microsoft Academic Search

Planktonic copepods are primary consumers in the ocean and are perhaps the most numerous metazoans on earth. Secondary production by these zooplankton supports most food webs of the open sea, directly affecting pelagic fish populations and the biological pump of carbon into the deep ocean. Models of marine ecosystems are quite sensitive to the formulation of the term for zooplankton

M. D. Ohman; H.-J. Hirche

2001-01-01

36

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

2013-06-18

37

A standard protocol for stable isotope analysis of zooplankton in aquatic food web research using mass balance correction models  

Microsoft Academic Search

Stable isotope analysis has become a crucial tool for aquatic food web ecologists, but a lack of methodological standardization hinders comparisons between studies. One methodological inconsistency in stable isotope food web research is the decision whether to extract lipids before stable isotope analysis. The depletion in zooplankton stable carbon isotope values (d13C) due to fatty acid content and the accuracy

Peter M. Smyntek; Mark A. Teece; Kimberly L. Schulz; Stephen J. Thackeray

2007-01-01

38

Ecological Modelling 193 (2006) 412436 A numerical simulation of the role of zooplankton in C, N and  

E-print Network

and P cycling in Lake Kinneret, Israel Louise C. Brucea,, David Hamiltonb, J¨org Imbergera, Gideon Galc online 10 November 2005 Abstract We quantify the role of zooplankton in nutrient cycles in Lake Kinneret seasonally in response to the annual hydrodynamic cycle of stratification and mixing. As a percent of total

Hambright, K. David

39

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

40

Global Dynamics of Zooplankton and Harmful Algae in Flowing Habitats  

E-print Network

Global Dynamics of Zooplankton and Harmful Algae in Flowing Habitats Sze-Bi Hsu Feng-Bin Wang Xiao from the dynamics of harmful algae and zooplankton in flowing- water habitats where a main channel. For the system modeling the dynamics of algae and their toxin that contains little limiting nutrient, we

Hsu, Sze-Bi

41

Phytoplankton-zooplankton dynamics in periodic environments taking into account eutrophication.  

PubMed

In this paper, we derive and analyze a mathematical model for the interactions between phytoplankton and zooplankton in a periodic environment, in which the growth rate and the intrinsic carrying-capacity of phytoplankton are changing with respect to time and nutrient concentration. A threshold value: "Predator's average growth rate" is introduced and it is proved that the phytoplankton-zooplankton ecosystem is permanent (both populations survive cronically) and possesses a periodic solution if and only if the value is positive. We use TP (Total Phosphorus) concentration to mark the degree of eutrophication. Based on experimental data, we fit the growth rate function and the environmental carrying capacity function with temperature and nutrient concentration as independent variables. Using measured data of temperature on water bodies we fit a periodic temperature function of time, and this leads the growth rate and intrinsic carrying-capacity of phytoplankton to be periodic functions of time. Thus we establish a periodic system with TP concentration as parameter. The simulation results reveal a high diversity of population levels of the ecosystem that are mainly sensitive to TP concentration and the death-rate of zooplankton. It illustrates that the eruption of algal bloom is mainly resulted from the increasing of nutrient concentration while zooplankton only plays a role to alleviate the scale of algal bloom, which might be used to explain the mechanism of algal bloom occurrence in many natural waters. What is more, our results provide a better understanding of the traditional manipulation method. PMID:23791607

Luo, Jinhuo

2013-10-01

42

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

43

PUMA (PUMA CONCOLOR) POPULATION MODELING  

E-print Network

PUMA (PUMA CONCOLOR) POPULATION MODELING Wildlife managers recognize that mathematical models can strategies. In this laboratory you will utilize PUMA, a population simulator, to predict the risk of extinction in a Puma population under various developmental scenarios. Development can potentially impact

Cavitt, John F.

44

Population Genetics: Difference Equation Models  

E-print Network

Chapter 3 Population Genetics: Difference Equation Models The diversity of life is a fundamental, genetic diversity. The achievements of genetics and molecular biology, as described in Chapter 1, have. The science of genotypic variation in interbreeding populations is called population genetics. Its goal

Sontag, Eduardo

45

Modeling Mitochondrial Population Genetics  

Microsoft Academic Search

Indirect tests have detected recombination in diverse animal mitochondrial DNA (mtDNA), including mammals. These results have far reaching implications for evolution and ecology, as virtually all animal population genetics studies assume mtDTA is clonally inherited. For the first time, we demonstrated that the molecular patterns detected by these tests could alternatively be explained by mutation rate heterogeneity, or clusters of

Stephanie Sun

2009-01-01

46

Population and Climate Change:Population and Climate Change: Coupling Population Models withCoupling Population Models with  

E-print Network

Coupling Population Models with Earth System ModelsEarth System Models Eugenia Kalnay, Safa Motesharrei, Jorge Rivas Change: Fully Coupling Population and Earth System Models" My research at the U. of Maryland #12

Kalnay, Eugenia

47

Global dynamics of zooplankton and harmful algae in flowing habitats  

NASA Astrophysics Data System (ADS)

This paper is devoted to the study of two advection-dispersion-reaction models arising from the dynamics of harmful algae and zooplankton in flowing-water habitats where a main channel is coupled to a hydraulic storage zone, representing an ensemble of fringing coves on the shoreline. For the system modeling the dynamics of algae and their toxin that contains little limiting nutrient, we establish a threshold type result on the global attractivity in terms of the basic reproduction ratio for algae. For the model with zooplankton that eat the algae and are inhibited by the toxin produced by algae, we show that there exists a coexistence steady state and the zooplankton is uniformly persistent provided that two basic reproduction ratios for algae and zooplankton are greater than unity.

Hsu, Sze-Bi; Wang, Feng-Bin; Zhao, Xiao-Qiang

48

Comparison between zooplankton data collected by the Continuous Plankton Recorder survey in the English  

E-print Network

Comparison between zooplankton data collected by the Continuous Plankton Recorder survey; accepted 28 March 2001 Abstract Zooplankton sampling has been carried out by the Continuous Plankton Recorder (CPR) survey since the 1930s enabling the study of long-term changes in plankton populations

Hays, Graeme

49

Reconstruction of Long-Term Changes in Lake water Chemistry, Zooplankton and Benthos of a Small, Acidified High-Mountain Lake: Magic Modelling and Palaeolimnogical Analysis  

Microsoft Academic Search

Starolesnianske pleso is a small and shallow acid lake in the High Tatra Mountains, situated at 2000 m above sea level, on granitic bedrock, with sparse and thin soil cover. When detailed measurements began in the 1980s Starolesnianske pleso had pH below 5 and only one species of cladoceran zooplankton, the ubiquitous Chydorus sphaericusPalaeolimnological investigations show changes in cladoceran zooplankton

E. Stuchlík; P. Appleby; P. Bitušík; C. Curtis; J. Fott; J. Kopá?ek; M. Pražáková; N. Rose; O. Strunecký; R. F. Wright

2002-01-01

50

Influence of a tidal front on zooplankton abundance, assemblages and life histories in Península Valdés, Argentina  

NASA Astrophysics Data System (ADS)

The complex biophysical interactions that occur in Península Valdés tidal front offer an appropriate scenario to study how zooplankton species respond to the environmental setting. In that sense, we studied why some zooplankton assemblages come to dominate in certain areas, focusing on the differential use that each life history stage makes on the hydrodynamic regimes. Environmental data and zooplankton samples were taken across the tidal front, covering well-mixed, frontal and stratified waters. Zooplankton abundance, assemblage structure, specific composition and life histories were analyzed in relation to depth, temperature, stratification level of the water column and chlorophyll a. Zooplankton-specific composition did not vary across the different zones of the front but, due to differences in relative abundance, three assemblages were detected in coincidence with the three zones analyzed. Most zooplankton adult groups and early life stages were related to the stratification level of the water column. This environmental factor best explained the coupling of the three different zooplankton assemblages with the three zones of the frontal system. This distributional pattern was clearly observed in the copepods group. Despite different copepod species prevailing in different parts of the tidal front, the frontal interface appears to be an important breeding area for all copepod species. The stratification level would be the main factor responsible for the zooplankton distributional pattern across the tidal front, although other physical and biological processes, such as transport, retention and life history strategies could be conditioning the establishment of different zooplankton populations in this complex frontal system.

Derisio, Carla; Alemany, Daniela; Acha, Eduardo M.; Mianzan, Hermes

2014-11-01

51

Sage-Grouse Population Model  

USGS Multimedia Gallery

Changes to greater sage-grouse distribution in the American West predicted by a new scientific model based on extensive study of sage-grouse range contraction. "Likely secure populations" indicates areas where sage-grouse are present and currently stable. "Currently extirpated" indicates areas ...

52

Zooplankton and the total phosphorus chlorophyll a relationship: hierarchical Bayesian  

E-print Network

Zooplankton and the total phosphorus ­ chlorophyll a relationship: hierarchical Bayesian analysis: Zooplankton grazing is important in resolving residual variation around the total phosphorus ­ chlorophyll found consistent effects of total zooplankton biomass, but not zooplankton length, on chlorophyll a

Notre Dame, University of

53

Modeling Political Populations with Bacteria  

NASA Astrophysics Data System (ADS)

Results from lattice-based simulations of micro-environments with heterogeneous nutrient resources reveal that competition between wild-type and GASP rpoS819 strains of E. Coli offers mutual benefit, particularly in nutrient deprived regions. Our computational model spatially maps bacteria populations and energy sources onto a set of 3D lattices that collectively resemble the topology of North America. By implementing Wright-Fishcer re- production into a probabilistic leap-frog scheme, we observe populations of wild-type and GASP rpoS819 cells compete for resources and, yet, aid each other's long term survival. The connection to how spatial political ideologies map in a similar way is discussed.

Cleveland, Chris; Liao, David

2011-03-01

54

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

55

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

56

Omnivorous zooplankton and planktivorous fish  

Microsoft Academic Search

The distance at which Lepomis gibbosus reacts to zooplankton is shown to be a linear fuilction of prey size. If fishes sweep out a cylindrical path as they forage the frequency of prey encountered is then proportional to the square of this reaction distance. With the inclusion of the probability of capture success after a fish pursues a prey, a

JOHN L. CONFER; PAMELA I. BLADES

1975-01-01

57

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

58

Does dispersal limitation impact the recovery of zooplankton communities damaged by a regional stressor?  

PubMed

The acidification and ongoing pH recovery of lakes in Killarney Provincial Park, Canada, provide a unique opportunity to increase our understanding of the role of dispersal as communities respond to environmental change. Time lags in community recovery following pH increases in acidified lakes have typically been attributed to local factors; however, no studies have been conducted to determine if colonist availability could also play a role. Moreover, the rates and mechanisms of dispersal to recovering lakes are poorly understood. In this study, we sought to determine if dispersal limitation could impede the recovery of zooplankton communities affected by a regional stressor. To achieve this objective, we used a combination of empirical data collection along with spatial modeling and variation partitioning techniques. Data were collected by measuring dispersal to four recovering lakes in Killarney Park. Dispersal traps were placed next to lakes to measure immigration overland, drift nets were used to measure immigration via streams, and in situ emergence traps were used to quantify immigration from historically deposited resting eggs. Documented dispersal levels were then compared with the theoretical critical density required for reproduction (N(c)) to determine if adequate numbers were dispersing to establish populations of acid-sensitive species in recovering lakes. Spatial modeling and variation partitioning were conducted using community and physical/chemical data for 45 park lakes that were collected in 1972-1973, 1990, and 2005. Field data demonstrated that a variety of zooplankton species were dispersing to recovering lakes through streams and the egg bank, but few individuals were collected dispersing overland. Although we identified 24 species of zooplankton dispersing, only six species absent from the communities of our study lakes were identified from our traps, and two of these species did not disperse in high enough numbers to surpass N(c). Local environmental variables explained the largest proportion of the variation in zooplankton communities (18-37%); however, spatial variables were also important (7-18%). The significant spatial patterns we found in the park's zooplankton communities, combined with the low overland dispersal levels we documented, suggest that dispersal limitation may be a more important impediment to recovery than was previously thought. PMID:21774427

Gray, Derek K; Arnott, Shelley E

2011-06-01

59

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

60

Effect of main-stem dams on zooplankton communities of the Missouri River (USA)  

Microsoft Academic Search

The persistence of plankton in flowing water presents an enigma, i.e., how can populations be sustained while constantly losing\\u000a individuals downriver? We examined the distribution and abundance of zooplankton from 146 sites on the Missouri River (USA)\\u000a and found large shifts in the dominance of major taxa between management zones of this regulated river. Crustacean zooplankton\\u000a were dominant in the

John E. Havel; Kim A. Medley; Kelli D. Dickerson; Theodore R. Angradi; David W. Bolgrien; Paul A. Bukaveckas; Terri M. Jicha

2009-01-01

61

On parameter estimation in population models.  

PubMed

We describe methods for estimating the parameters of Markovian population processes in continuous time, thus increasing their utility in modelling real biological systems. A general approach, applicable to any finite-state continuous-time Markovian model, is presented, and this is specialised to a computationally more efficient method applicable to a class of models called density-dependent Markov population processes. We illustrate the versatility of both approaches by estimating the parameters of the stochastic SIS logistic model from simulated data. This model is also fitted to data from a population of Bay checkerspot butterfly (Euphydryas editha bayensis), allowing us to assess the viability of this population. PMID:16984803

Ross, J V; Taimre, T; Pollett, P K

2006-12-01

62

Adventures With The Fish Pond: Population Modeling  

NSDL National Science Digital Library

This activity builds on the population decay M&M activity and will introduce students to recursive equations and uses calculators as an efficient tool for exploring population models. Students will describe what happens to the fish population from one year to another. Each pair of students will have an activity sheet to go along with the activity, and a calculator is needed.

Math, Pbs T.; Pbs

2010-01-01

63

Habitat Heterogeneity Determines Climate Impact on Zooplankton Community Structure and Dynamics  

PubMed Central

Understanding and predicting species distribution in space and time and consequently community structure and dynamics is an important issue in ecology, and particularly in climate change research. A crucial factor determining the composition and dynamics of animal populations is habitat heterogeneity, i.e., the number of structural elements in a given locality. In the marine pelagic environment habitat heterogeneity is represented by the distribution of physical oceanographic parameters such as temperature, salinity and oxygen that are closely linked to atmospheric conditions. Little attention has been given, however, to the role of habitat heterogeneity in modulating the response of animal communities to external climate forcing. Here we investigate the long-term dynamics of Acartia spp., Temora longicornis, and Pseudocalanus acuspes, three dominant zooplankton species inhabiting different pelagic habitats in the Central Baltic Sea (CBS). We use the three copepods as indicator species for changes in the CBS zooplankton community and apply non-linear statistical modeling techniques to compare spatial population trends and to identify their drivers. We demonstrate that effects of climate variability and change depend strongly on species-specific habitat utilization, being more direct and pronounced at the upper water layer. We propose that the differential functional response to climate-related drivers in relation to strong habitat segregation is due to alterations of the species’ environmental niches. We stress the importance of understanding how anticipated climate change will affect ecological niches and habitats in order to project spatio-temporal changes in species abundance and distribution. PMID:24614110

Otto, Saskia A.; Diekmann, Rabea; Flinkman, Juha; Kornilovs, Georgs; Mollmann, Christian

2014-01-01

64

A simplified model of spatiotemporal population dynamics  

Microsoft Academic Search

The paper is a development of the Hotelling model of population growth and migration. In the original model, a logistic growth term is combined with linear diffusion. Since man produces his own means of subsistance and himself decides which standard of living per capita is desirable, the 'saturation' population cannot be regarded as a constant, and production technology and technological

T Puu

1985-01-01

65

POPULATION MODELS IN ECOLOGICAL RISK ASSESSMENT  

EPA Science Inventory

A SETAC Pellston Workshop on Population-Level Risk Assessment was held in Roskilde, Denmark on 23-27 August 2003. One aspect of this workshop focused on modeling approaches for characterizing population-level effects of chemical exposure. The modeling work group identified th...

66

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

67

Constraining population synthesis models via the binary neutron star population  

E-print Network

The observed sample of double neutron-star (NS-NS) binaries presents a challenge to population-synthesis models of compact object formation: the parameters entering into these models must be carefully chosen so as to match (i) the observed star formation rate and (ii) the formation rate of NS-NS binaries, which can be estimated from the observed sample and the selection effects related to the discoveries with radio-pulsar surveys. In this paper, we select from an extremely broad family of possible population synthesis models those few (2%) which are consistent with the observed sample of NS-NS binaries. To further sharpen the constraints the observed NS-NS population places upon our understanding of compact-object formation processes, we separate the observed NS-NS population into two channels: (i) merging NS-NS binaries, which will inspiral and merge through the action of gravitational waves within $10 $ Gyr, and (ii) wide NS-NS binaries, consisting of all the rest. With the subset of astrophysically consistent models, we explore the implications for the rates at which double black hole (BH-BH), black hole-neutron star (BH-NS), and NS-NS binaries will merge through the emission of gravitational waves.

R. O'Shaughnessy; C. Kim; T. Frakgos; V. Kalogera; K. Belczynski

2005-04-21

68

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

69

Modelling the predation, growth and population dynamics of fish within a spatially-resolved shelf-sea ecosystem model  

NASA Astrophysics Data System (ADS)

The development and analysis of a fish population module within the European Regional Seas Ecosystem Model (ERSEM) is described. Fixed predation rates on ERSEM zooplankton and zoobenthos, which may be used in place of this dynamic module of fish, are described also. The dynamic module is age-structured, with state variables for the number of individuals and their weight, the latter partitioned into structural (skeletal, essentially) and remobilizable 'reserve' components. It is capable of prediction of observed patterns of both positive and negative changes in individual weight. The fish are modelled as one population for the whole North Sea, superimposed on the ERSEM box structure. Parameters have been derived from the literature where possible and, for herring, certain parameters have been adjusted to match independent estimates of growth in the field. Preliminary results show that herring growth rate depends inversely on biomass, when changes in the latter are caused by altered fishing mortality. The magnitude of these effects is in agreement with historical data for herring in the North Sea. The model is discussed in relation to previous attempts to model fish population dynamics, particularly in the North Sea.

Bryant, A. D.; Heath, M. R.; Broekhuizen, N.; Ollason, J. G.; Gurney, W. S. C.; Greenstreet, S. P. R.

70

Assimilation of organic matter by zooplankton  

Microsoft Academic Search

A method for direct measurcmcnt of percentage of assimilation of organic matter by zooplankton that does not require the quantitative recovery of feces and can be adapted for USC in the field as well as in laboratory investigations is described. If it is assumed that only the organic fraction of the food ingested by a zooplankton animal is affected by

ROBERT J. CONOVER

1966-01-01

71

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

72

Density-dependent mortality in an oceanic copepod population.  

PubMed

Planktonic copepods are primary consumers in the ocean and are perhaps the most numerous metazoans on earth. Secondary production by these zooplankton supports most food webs of the open sea, directly affecting pelagic fish populations and the biological pump of carbon into the deep ocean. Models of marine ecosystems are quite sensitive to the formulation of the term for zooplankton mortality, although there are few data available to constrain mortality rates in such models. Here we present the first evidence for nonlinear, density-dependent mortality rates of open-ocean zooplankton. A high-frequency time series reveals that per capita mortality rates of eggs of Calanus finmarchicus Gunnerus are a function of the abundance of adult females and juveniles. The temporal dynamics of zooplankton populations can be influenced as much by time-dependent mortality rates as by variations in 'bottom up' forcing. The functional form and rates chosen for zooplankton mortality in ecosystem models can alter the balance of pelagic ecosystems, modify elemental fluxes into the ocean's interior, and modulate interannual variability in pelagic ecosystems. PMID:11493921

Ohman, M D; Hirche, H J

2001-08-01

73

A simulation model of an insect population  

NSDL National Science Digital Library

An insect life table simulation developed by Hein Bijlmakers. The above URL gets you to the introduction of the simulation model where various aspects of an insect population dynamics are explained. The link to the simulation brings you to the model itself with a myriad of variables including population development; egg; larval; pupal and adult mortality by parasitoids and predators amongst others. This is a great tool to investigate various aspects of insect population dynamics allowing one to investigate the impact of a number of variables on a population and may help students understand the function of insect life tables. Up to 40 generations can be iterated.

0002-11-30

74

Hidden process models for animal population dynamics.  

PubMed

Hidden process models are a conceptually useful and practical way to simultaneously account for process variation in animal population dynamics and measurement errors in observations and estimates made on the population. Process variation, which can be both demographic and environmental, is modeled by linking a series of stochastic and deterministic subprocesses that characterize processes such as birth, survival, maturation, and movement. Observations of the population can be modeled as functions of true abundance with realistic probability distributions to describe observation or estimation error. Computer-intensive procedures, such as sequential Monte Carlo methods or Markov chain Monte Carlo, condition on the observed data to yield estimates of both the underlying true population abundances and the unknown population dynamics parameters. Formulation and fitting of a hidden process model are demonstrated for Sacramento River winter-run chinook salmon (Oncorhynchus tshawytsha). PMID:16705962

Newman, K B; Buckland, S T; Lindley, S T; Thomas, L; Fernández, C

2006-02-01

75

On parameter estimation in population models  

Microsoft Academic Search

We describe methods for estimating the parameters of Markovian population processes in continuous time, thus increasing their utility in modelling real biological systems. A general approach, applicable to any finite-state continuous-time Markovian model, is presented, and this is specialised to a computationally more efficient method applicable to a class of models called density-dependent Markov population processes. We illustrate the versatility

J. V. Ross; T. Taimre; P. K. Pollett

2006-01-01

76

Some population and epidemic models revisited.  

PubMed

Three problems of population and epidemic models formulated between ten and thirty years ago are reconsidered. In each case, a modified approach to the problem leads to its solution. For the two-sex population model, the solution of a Riccati equation results in an expression for the generating function of the process. The fully stochastic, as against the previously studied semistochastic, model of population growth with random catastrophes yields to hard analysis. Finally a generalized form of the general stochastic epidemic is solved using matrix geometric methods. PMID:6600106

Gani, J

1984-01-01

77

A simplified model of spatiotemporal population dynamics.  

PubMed

This paper is an extension of the model of population growth and migration originally developed by H. Hotelling in 1921. This model consists of two ingredients, a logistic growth function and a linear spatial diffusion term. The author notes that the saturation population can be affected by the development of new technology and that improvements in transportation have increased the possibilities for migration. "Basic nonlinearities are introduced by use of a production technology with increasing-decreasing returns to scale. It is demonstrated how industrial takeoffs, population transitions, and agglomerative spatial patterns can emerge by changing the model parameters." PMID:12267309

Puu, T

1985-09-01

78

Modelling Biological Populations in Space and Time  

NASA Astrophysics Data System (ADS)

Preface; A list of symbols and notation; 1. Introductory remarks; 2. Simple birth-death processes; 3. General birth-death processes; 4. Time-lag models of population growth; 5. Competition processes; 6. Predator-prey processes; 7. Spatial predator-prey systems; 8. Fluctuating environments; 9. Spatial population dynamics; 10. Epidemic processes; 11. Linear and branching architectures; References; Author index; Subject index.

Renshaw, Eric

1993-08-01

79

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

80

Effect of advection on variations in zooplankton at a single location near Cabo Nazca, Peru  

SciTech Connect

Temporal variations in the biomass and species composition of zooplankton at a single midshelf station in an upwelling area off Peru can be explained to a large extent by onshore-offshore advection in the upper 20 m of the water column. During periods of strong or sustained near-surface onshore flow, peaks in biomass of zooplankton were observed at midshelf and typically oceanic species of copepod were collected. In periods of offshore flow at the surface, a copepod capable of migrating into oxygen-depleted layers deeper than 30 m was collected. A simple translocation model of advection applied to the cross-shelf distribution of Paracalanus parvus suggests that the fluctuations in P. pavus observed in the midshelf time-series were closely related to onshore-offshore flow in the upper 20 m. Fluctuations in abundance of the numerically dominant copepod, Acartia tonsa, were apparently affected by near surface flow also. The population age-structure suggests that A. tonsa was growing at maximal rates, due in part to its positive feeding response to the dinoflagellate/diatom assemblage of phytoplankton.

Smith, S L; Brink, K H; Santander, H; Cowles, T J; Huyer, A

1980-04-01

81

Modelling Interacting Epidemics in Overlapping Populations  

E-print Network

Modelling Interacting Epidemics in Overlapping Populations Marily Nika1 , Dieter Fiems2 , Koen de-Pietersnieuwstraat 41, 9000 Gent, Belgium Email: {dieter.fiems,kdeturck}@telin.ugent.be Abstract. Epidemic modelling-syndemic effects. In this paper we model the dynamics of two types of epidemics with syndemic and counter

Knottenbelt, William J.

82

Population-expression models of immune response  

NASA Astrophysics Data System (ADS)

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.

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

2013-06-01

83

Next Generation Sequencing Reveals the Hidden Diversity of Zooplankton Assemblages  

PubMed Central

Background Zooplankton play an important role in our oceans, in biogeochemical cycling and providing a food source for commercially important fish larvae. However, difficulties in correctly identifying zooplankton hinder our understanding of their roles in marine ecosystem functioning, and can prevent detection of long term changes in their community structure. The advent of massively parallel next generation sequencing technology allows DNA sequence data to be recovered directly from whole community samples. Here we assess the ability of such sequencing to quantify richness and diversity of a mixed zooplankton assemblage from a productive time series site in the Western English Channel. Methodology/Principle Findings Plankton net hauls (200 µm) were taken at the Western Channel Observatory station L4 in September 2010 and January 2011. These samples were analysed by microscopy and metagenetic analysis of the 18S nuclear small subunit ribosomal RNA gene using the 454 pyrosequencing platform. Following quality control a total of 419,041 sequences were obtained for all samples. The sequences clustered into 205 operational taxonomic units using a 97% similarity cut-off. Allocation of taxonomy by comparison with the National Centre for Biotechnology Information database identified 135 OTUs to species level, 11 to genus level and 1 to order, <2.5% of sequences were classified as unknowns. By comparison a skilled microscopic analyst was able to routinely enumerate only 58 taxonomic groups. Conclusions Metagenetics reveals a previously hidden taxonomic richness, especially for Copepoda and hard-to-identify meroplankton such as Bivalvia, Gastropoda and Polychaeta. It also reveals rare species and parasites. We conclude that Next Generation Sequencing of 18S amplicons is a powerful tool for elucidating the true diversity and species richness of zooplankton communities. While this approach allows for broad diversity assessments of plankton it may become increasingly attractive in future if sequence reference libraries of accurately identified individuals are better populated. PMID:24244737

Harmer, Rachel A.; Somerfield, Paul J.; Atkinson, Angus

2013-01-01

84

Formalisms for Specifying Markovian Population Models  

NASA Astrophysics Data System (ADS)

We compare several languages for specifying Markovian population models such as queuing networks and chemical reaction networks. These languages —matrix descriptions, stochastic Petri nets, stoichiometric equations, stochastic process algebras, and guarded command models— all describe continuous-time Markov chains, but they differ according to important properties, such as compositionality, expressiveness and succinctness, executability, ease of use, and the support they provide for checking the well-formedness of a model and for analyzing a model.

Henzinger, Thomas A.; Jobstmann, Barbara; Wolf, Verena

85

Melatonin signaling controls circadian swimming behavior in marine zooplankton.  

PubMed

Melatonin, the "hormone of darkness," is a key regulator of vertebrate circadian physiology and behavior. Despite its ubiquitous presence in Metazoa, the function of melatonin signaling outside vertebrates is poorly understood. Here, we investigate the effect of melatonin signaling on circadian swimming behavior in a zooplankton model, the marine annelid Platynereis dumerilii. We find that melatonin is produced in brain photoreceptors with a vertebrate-type opsin-based phototransduction cascade and a light-entrained clock. Melatonin released at night induces rhythmic burst firing of cholinergic neurons that innervate locomotor-ciliated cells. This establishes a nocturnal behavioral state by modulating the length and the frequency of ciliary arrests. Based on our findings, we propose that melatonin signaling plays a role in the circadian control of ciliary swimming to adjust the vertical position of zooplankton in response to ambient light. PMID:25259919

Tosches, Maria Antonietta; Bucher, Daniel; Vopalensky, Pavel; Arendt, Detlev

2014-09-25

86

Melatonin Signaling Controls Circadian Swimming Behavior in Marine Zooplankton  

PubMed Central

Summary Melatonin, the “hormone of darkness,” is a key regulator of vertebrate circadian physiology and behavior. Despite its ubiquitous presence in Metazoa, the function of melatonin signaling outside vertebrates is poorly understood. Here, we investigate the effect of melatonin signaling on circadian swimming behavior in a zooplankton model, the marine annelid Platynereis dumerilii. We find that melatonin is produced in brain photoreceptors with a vertebrate-type opsin-based phototransduction cascade and a light-entrained clock. Melatonin released at night induces rhythmic burst firing of cholinergic neurons that innervate locomotor-ciliated cells. This establishes a nocturnal behavioral state by modulating the length and the frequency of ciliary arrests. Based on our findings, we propose that melatonin signaling plays a role in the circadian control of ciliary swimming to adjust the vertical position of zooplankton in response to ambient light. PMID:25259919

Tosches, Maria Antonietta; Bucher, Daniel; Vopalensky, Pavel; Arendt, Detlev

2014-01-01

87

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...

88

Cell population modelling of yeast glycolytic oscillations.  

PubMed Central

We investigated a cell-population modelling technique in which the population is constructed from an ensemble of individual cell models. The average value or the number distribution of any intracellular property captured by the individual cell model can be calculated by simulation of a sufficient number of individual cells. The proposed method is applied to a simple model of yeast glycolytic oscillations where synchronization of the cell population is mediated by the action of an excreted metabolite. We show that smooth one-dimensional distributions can be obtained with ensembles comprising 1000 individual cells. Random variations in the state and/or structure of individual cells are shown to produce complex dynamic behaviours which cannot be adequately captured by small ensembles. PMID:12206713

Henson, Michael A; Müller, Dirk; Reuss, Matthias

2002-01-01

89

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...

90

Predation by estuarine zooplankton on tintinnid ciliates  

NASA Astrophysics Data System (ADS)

Laboratory experiments were conducted to determine the feeding performances of Uca zoeae and the estuarine copepods Acartia tonsa and Tortanus setacaudatus when these zooplankton preyed upon the co-occurring tintinnids Favella panamensis (length 265 ?m) and Tintinnopsis tubulosa (length 148 ?m). Predation by Favella on Tintinnopsis was also studied. Over the range of experimental prey densities used, Acartia ingested Tintinopsis at rates linearly related to prey density. Favella was ingested by Aractia at higher rates than was Tintinnopsis. Tortamus ingested Favella more readily than did Acartia, but Tortanus did not ingest Tintinnopsis. Uca ingested both Tintinnopsis and Favella while Tintinnopsis was also ingested by the larger tintinnid Favella. Comparisons of Acartia predation on tintinnids with published data on ingestion of nauplii and phytoplankton showed that when the phytoplankton are dominated by small (diameters < 10 ?m) species, tintinnids in concentrations exceeding 10 3 organisms 1 -1 can be important items in the diets of Acartia. At lower tintinnid concentrations or when algal species with diameters > 10 ?m are present in significant concentrations, tintinnids merely supplement algae in the diet of Acartia. Generally, tintinnids are more important food items for Acartia than are comparably sized nauplii. Only at concentrations exceeding 10 4 cop. m -3 can Acartia depress tintinid population growth.

Robertson, J. Roy

1983-01-01

91

A Population Model of Integrative Cardiovascular Physiology  

PubMed Central

We present a small integrative model of human cardiovascular physiology. The model is population-based; rather than using best fit parameter values, we used a variant of the Metropolis algorithm to produce distributions for the parameters most associated with model sensitivity. The population is built by sampling from these distributions to create the model coefficients. The resulting models were then subjected to a hemorrhage. The population was separated into those that lost less than 15 mmHg arterial pressure (compensators), and those that lost more (decompensators). The populations were parametrically analyzed to determine baseline conditions correlating with compensation and decompensation. Analysis included single variable correlation, graphical time series analysis, and support vector machine (SVM) classification. Most variables were seen to correlate with propensity for circulatory collapse, but not sufficiently to effect reasonable classification by any single variable. Time series analysis indicated a single significant measure, the stressed blood volume, as predicting collapse in situ, but measurement of this quantity is clinically impossible. SVM uncovered a collection of variables and parameters that, when taken together, provided useful rubrics for classification. Due to the probabilistic origins of the method, multiple classifications were attempted, resulting in an average of 3.5 variables necessary to construct classification. The most common variables used were systemic compliance, baseline baroreceptor signal strength and total peripheral resistance, providing predictive ability exceeding 90%. The methods presented are suitable for use in any deterministic mathematical model. PMID:24058546

Pruett, William A.; Husband, Leland D.; Husband, Graham; Dakhlalla, Muhammad; Bellamy, Kyle; Coleman, Thomas G.; Hester, Robert L.

2013-01-01

92

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

93

The effects of haloclines on the vertical distribution and migration of zooplankton  

Microsoft Academic Search

While the influence of horizontal salinity gradients on the distribution and abundance of planktonic organisms in estuaries is relatively well known, the effects of vertical salinity gradients (haloclines) are less well understood. Because biological, chemical, and physical conditions can vary between different salinity strata, an understanding of the behavioral response of zooplankton to haloclines is crucial to understanding the population

Laurence A. Lougee; Stephen M. Bollens; Sean R. Avent

2002-01-01

94

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

Microsoft Academic Search

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

K. D. Malloy; M. A. Holman; D. Mitchell

1997-01-01

95

Comparison between zooplankton data collected by the Continuous Plankton Recorder survey in the English Channel and by WP-2 nets at station L4, Plymouth (UK)  

NASA Astrophysics Data System (ADS)

Zooplankton sampling has been carried out by the Continuous Plankton Recorder (CPR) survey since the 1930s enabling the study of long-term changes in plankton populations, the elucidation of seasonal patterns of abundance, and more recently providing zooplankton biomass estimates for ecosystem models. Data for zooplankton abundance collected by CPR tows in the Western English Channel (between 1988 and 1998) were compared to vertically integrated samples collected from station L4 off Plymouth, UK. Comparisons were made for locally abundant copepods (including Acartia, Calanus, Para/ Pseudocalanus, Centropages, Oithona and Temora) collected by CPR and WP-2 nets. All dominant species recorded at L4 were also common to the CPR data. However, the position of the taxa in the two datasets was not equivalent. Seasonal cycles revealed by CPR data were significantly similar to those recorded throughout the water column at L4 for most taxa. However, absolute levels of abundance differed for the two datasets: abundances were underestimated by CPR samples when compared to those of vertically integrated samples by a factor of between 2 and 35, with the exception of Centropages. The differing mesh sizes (200 and 270 ?m) of the WP-2 net and CPR mesh could only partially explain these differences in abundance, implying that the behaviour of individual taxa and their depth in the water column also influenced the abundance recorded.

John, Eurgain H.; Batten, Sonia D.; Harris, Roger P.; Hays, Graeme C.

2001-12-01

96

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. PMID:24101996

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

2013-01-01

97

Examination of the role of detritus food quality, phytoplankton intracellular storage capacity, and zooplankton stoichiometry on planktonic dynamics  

E-print Network

, and zooplankton stoichiometry on planktonic dynamics Gurbir Perhar, George B. Arhonditsis Ecological Modeling nutrient storage Seston food quality Stoichiometric theory Highly unsaturated fatty acids Plankton dynamics Nutrient stoichiometric ratios are primary driving factors of planktonic food web dynamics. Ecological

Arhonditsis, George B.

98

Using occupancy and population models to assess habitat conservation opportunities for an isolated carnivore population  

Microsoft Academic Search

An isolated population of the fisher (Martes pennanti) in the southern Sierra Nevada, California, is threatened by small size and habitat alteration from wildfires, fuels management, and other factors. We assessed the population’s status and conservation options for its habitat using a spatially explicit population model coupled with a fisher probability of occurrence model. The fisher occurrence model was selected

Wayne Spencer; Heather Rustigian-Romsos; James Strittholt; Robert Scheller; William Zielinski; Richard Truex

2011-01-01

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

Short communication Continuous plankton recorder underestimates zooplankton abundance  

E-print Network

Short communication Continuous plankton recorder underestimates zooplankton abundance Joachim W online 25 September 2012 Keywords: Mesozooplankton North Sea Continuous plankton recorder A comparison between monthly mean Continuous Plankton Recorder (CPR) data and zooplankton data caught during winter

Dippner, Joachim W.

101

Zooplankton Competition and Plankton Community Structure Michael Lynch  

E-print Network

Zooplankton Competition and Plankton Community Structure Michael Lynch Limnology and Oceanography. Biol. In press. Zooplankton competition and plankton community structure Recent attempts to resolve in plankton communities (Dodson 1974; Dodson et al. 1976). However, con- sideration of several assumptions

Lynch, Michael

102

Material properties of zooplankton and nekton from the California current  

NASA Astrophysics Data System (ADS)

This study measured the material properties of zooplankton, Pacific hake (Merluccius productus), Humboldt squid (Dosidicus gigas), and two species of myctophids (Symbolophorus californiensis and Diaphus theta) collected from the California Current ecosystem. The density contrast (g) was measured for euphausiids, decapods (Sergestes similis), amphipods (Primno macropa, Phronima sp., and Hyperiid spp.), siphonophore bracts, chaetognaths, larval fish, crab megalopae, larval squid, and medusae. Morphometric data (length, width, and height) were collected for these taxa. Density contrasts varied within and between zooplankton taxa. The mean and standard deviation for euphausiid density contrast were 1.059 +/- 0.009. Relationships between zooplankton density contrast and morphometric measurements, geographic location, and environmental conditions were investigated. Site had a significant effect on euphausiid density contrast. Density contrasts of euphausiids collected in the same geographic area approximately 4-10 days apart were significantly higher (p < 0.001). Sound speed contrast (h) was measured for euphausiids and pelagic decapods (S. similis) and it varied between taxa. The mean and standard deviation for euphausiid sound speed were 1.019 +/- 0.009. Euphausiid mass was calculated from density measurements and volume, and a relationship between euphausiid mass and length was produced. We determined that euphausiid from volumes could be accurately estimated two dimensional measurements of animal body shape, and that biomass (or biovolume) could be accurately calculated from digital photographs of animals. Density contrast (g) was measured for zooplankton, pieces of hake flesh, myctophid flesh, and of the following Humboldt squid body parts: mantle, arms, tentacle, braincase, eyes, pen, and beak. The density contrasts varied within and between fish taxa, as well as among squid body parts. Effects of animal length and environmental conditions on nekton density contrast were investigated. The sound speed contrast (h) was measured for Pacific hake flesh, myctophid flesh, Humboldt squid mantle, and Humboldt squid braincase. Sound speed varied within and between nekton taxa. The material properties reported in this study can be used to improve target strength estimates from acoustic scattering models which would increase the accuracy of biomass estimates from acoustic surveys for these zooplankton and nekton.

Becker, Kaylyn

103

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

104

USING POPULATION MODELS TO EVALUATE RISK IN POPULATION OF BIRDS  

EPA Science Inventory

Wildlife populations are exposed to varying habitat structure and quality, as well as an array of human-induced environmental stressors. Predicting the consequences to a real population of one perturbation (e.g. a pesticide application) without considering other human activities ...

105

Population models of low-mass binaries  

NASA Astrophysics Data System (ADS)

I review the current understanding of the formation and evolutionary history of binaries with low-mass companions, focusing on systems that contain a white dwarf, or a component that will evolve into a white dwarf. I will highlight the potential and pitfalls of binary catalogues emerging from exoplanet transit searches, and review the state of the art of population models for low-mass binaries.

Kolb, Ulrich

2014-09-01

106

Preliminary study on the occurrence and risk arising from bacteria internalized in zooplankton in drinking water.  

PubMed

In this study, an environmental sampling campaign was conducted to detect internalized E. coli and C. jejuni bacteria in zooplankton and amoebae samples collected at various stages of three water treatment plants in Amsterdam, the Netherlands. Eight sampling locations were selected and sampling was performed twice, at a two-week interval, at each location. Chlorination was used to inactivate free (external) bacteria in the concentrated zooplankton samples and sonication was used to disrupt zooplankton organisms in order to release and recover internalized bacteria. Zooplankton enumeration was performed by microscopy. No internalized E. coli or C. jejuni bacteria were recovered from all of the samples analyzed. The occurrence of internalized E. coli or C. jejuni bacteria in drinking water was estimated to be lower than one internalized bacteria in 10? zooplankton organisms, as derived from the detection limit of the sampling campaign. By using the QMRA approach and the Beta-Poisson model, a risk of infection of less than 9.2E-6 and 5.9E-5 was estimated for internalized E. coli and C. jejuni in drinking water, respectively. This study remains preliminary due to the limited number of samples taken at each location. PMID:21245561

Bichai, F; Hijnen, W; Baars, Eric; Rosielle, M; Dullemont, Y; Barbeau, B

2011-01-01

107

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

108

Aggregate Input Output Models of Neuronal Populations  

PubMed Central

An extraordinary amount of electrophysiological data has been collected from various brain nuclei to help us understand how neural activity in one region influences another region. In this paper, we exploit the point process modeling (PPM) framework and describe a method for constructing aggregate input-output (IO) stochastic models that predict spiking activity of a population of neurons in the “output” region as a function of the spiking activity of a population of neurons in the “input” region. We first build PPMs of each output neuron as a function of all input neurons, and then cluster the output neurons using the model parameters. Output neurons that lie within the same cluster have the same functional dependence on the input neurons. We first applied our method to simulated data, and successfully uncovered the predetermined relationship between the two regions. We then applied our method to experimental data to understand the input-output relationship between motor cortical neurons and (i) somatosensory and (ii) premotor cortical neurons during a behavioral task. Our aggregate IO models highlighted interesting physiological dependencies including relative effects of inhibition/excitation from input neurons and extrinsic factors on output neurons. PMID:22552544

Saxena, Shreya; Schieber, Marc H.; Thakor, Nitish V.; Sarma, Sridevi V.

2014-01-01

109

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

110

Functional responses for zooplankton feeding on multiple resources: a review of assumptions and biological dynamics  

Microsoft Academic Search

Modelers often need to quantify the rates at which zooplankton consume a variety of species, size classes and trophic types. Implicit in the equations used to describe the multiple resource functional response (i.e. how nutritional intake varies with resource densities) are assumptions that are not often stated, let alone tested. This is problematic because models are sensitive to the details

Wendy Gentleman; Andrew Leising; Bruce Frost; Suzanne Strom; James Murray

2003-01-01

111

SIMULATING TEMPORAL VARIATIONS IN NUTRIENT, PHYTOPLANKTON, AND ZOOPLANKTON ON THE INNER OREGON SHELF  

EPA Science Inventory

The objective of this study is to use a numerical model to examine the linkages between physical processes and temporal variability in the plankton dynamics in a coastal upwelling system. We used a nutrient-phytoplankton-zooplankton model coupled to a two-dimensional circulation...

112

Trait-based approaches to zooplankton communities  

E-print Network

are major primary consumers and predators in most aquatic ecosys- tems. They exhibit tremendous diversity. Zooplankton are among the most abundant aquatic organisms and they occupy key trophic positions in most marine in marine and fresh- water environments exhibit significant diversity of eco- logical strategies, dominance

113

Bacteria dispersal by hitchhiking on zooplankton  

PubMed Central

Microorganisms and zooplankton are both important components of aquatic food webs. Although both inhabit the same environment, they are often regarded as separate functional units that are indirectly connected through nutrient cycling and trophic cascade. However, research on pathogenic and nonpathogenic bacteria has shown that direct association with zooplankton has significant influences on the bacteria's physiology and ecology. We used stratified migration columns to study vertical dispersal of hitchhiking bacteria through migrating zooplankton across a density gradient that was otherwise impenetrable for bacteria in both upward and downward directions (conveyor-belt hypothesis). The strength of our experiments is to permit quantitative estimation of transport and release of associated bacteria: vertical migration of Daphnia magna yielded an average dispersal rate of 1.3 × 105·cells·Daphnia?1·migration cycle?1 for the lake bacterium Brevundimonas sp. Bidirectional vertical dispersal by migrating D. magna was also shown for two other bacterial species, albeit at lower rates. The prediction that diurnally migrating zooplankton acquire different attached bacterial communities from hypolimnion and epilimnion between day and night was subsequently confirmed in our field study. In mesotrophic Lake Nehmitz, D. hyalina showed pronounced diel vertical migration along with significant diurnal changes in attached bacterial community composition. These results confirm that hitchhiking on migrating animals can be an important mechanism for rapidly relocating microorganisms, including pathogens, allowing them to access otherwise inaccessible resources. PMID:20547852

Grossart, Hans-Peter; Dziallas, Claudia; Leunert, Franziska; Tang, Kam W.

2010-01-01

114

Estimating the predatory impact of gelatinous zooplankton  

Microsoft Academic Search

We propose a new approach to assess the predatory impact of gelatinous zooplankton on their prey, in which information from field samples and laboratory experiments allows us to estimate predator ingestion rates from analyses of predator gut contents. The feasibility of this approach was tested in laboratory experiments with the ctenophore Pleurobrachia bachei feeding on adult stages of the copepods

SHONALI T. CHANDY; CHARLES H. GREENE

1995-01-01

115

A Mesoscale Diffusion Model in Population Genetics with  

E-print Network

' & $ % A Mesoscale Diffusion Model in Population Genetics with Dynamic Fitness Mike O'Leary Towson University Judith R. Miller Georgetown University 1 #12;A mesoscale diffusion model in population genetics diffusion model in population genetics with dynamic fitness ' & $ % The Discrete Model · Let the fraction

O'Leary, Michael

116

Modeling Daphnia population dynamics and demography under natural conditions  

Microsoft Academic Search

Various approaches to modeling the population dynamics and demography of Daphnia have been published. These methods range from the simple egg-ratio method, to mathematically complex models based on partial differential equations and numerically complex individual-based Daphnia population models. The usefulness of these models in unraveling the population dynamics and demography of Daphnia under natural conditions is discussed. Next to this,

W. M. Mooij; S. Hülsmann; J. Vijverberg; A. Veen; E. H. R. R. Lammens

2003-01-01

117

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

118

Mathematics and physics Biology Modelling a population Immunology Modelling T cell immunology  

E-print Network

Mathematics and physics Biology Modelling a population Immunology Modelling T cell immunology;Mathematics and physics Biology Modelling a population Immunology Mathematics is a special science! #12;Mathematics and physics Biology Modelling a population Immunology Classical mechanics (Newton) Figure

Wirosoetisno, Djoko

119

Increasing zooplankton size diversity enhances the strength of top-down control on phytoplankton in the East China Sea  

NASA Astrophysics Data System (ADS)

Body size is one of the fundamental characteristics of organisms linking many ecosystem properties and functions. Recent studies suggest that environmental changes alter the size structure of pelagic food webs; however, ecosystem consequences of such changes remain unclear. Here we tested our main hypothesis that increasing zooplankton size diversity enhances top-down control on phytoplankton in the East China Sea (H1), as well as five conventional hypotheses explaining the top-down control: shallower zooplankton size spectrum enhances the strength of top-down control (H2); nutrient enrichment lessens the strength of top-down control (H3); increasing zooplankton taxonomic diversity enhances the strength of top-down control (H4); increasing fish predation is linked to decreasing the strength of top-down control of zooplankton on phytoplankton (H5); increasing temperature intensifies the strength of top-down control (H6). While the results of our univariate analyses support H1, H2, H3, and H4, more in depth analyses indicate that zooplankton size diversity is the most important factor in determining the strength of top-down control on phytoplankton in East China Sea. Our results suggest a new potential mechanism that increasing predator size diversity enhances the strength of top-down control on prey through diet niche partitioning. This mechanism can be explained by the concept of optimal predator-prey body-mass ratio concept. Suppose each size group of zooplankton predators has its own optimal phytoplankton prey size, increasing size diversity of zooplankton would promote diet niche partitioning of predators and thus elevates the top-down control.Fig. 1 Scatter plots the relationship between zooplankton/phytoplankton biomass ratio versus (A) zooplankton size diversity, (B) slope of zooplankton size spectrum, (C) Zoolankton Shannon diversity, (D) NO3, (E) PO4, (F) SiO3, (G) water temperature, and (H) fish larvae density in the East China Sea. Table 1. Results of the generalized linear mixed-effect model in investigating the effect of each factor on the spatiotemporal dynamics of zooplankton/phytoplankton biomass ratio in the East China Sea, with sampling cruises as a random effect. A lower value of AIC represents better goodness of fit of the model. The p-value was estimated based on MCMC sampling.

Ye, L.; Chang, C.; García-Comas, C.; Gong, G.; Hsieh, C.

2012-12-01

120

UV radiation and freshwater zooplankton: damage, protection and recovery  

PubMed Central

While many laboratory and field studies show that zooplankton are negatively affected when exposed to high intensities of ultraviolet radiation (UVR), most studies also indicate that zooplankton are well adapted to cope with large variations in their UVR exposure in the pelagic zone of lakes. The response mechanisms of zooplankton are diverse and efficient and may explain the success and richness of freshwater zooplankton in optically variable waters. While no single behavioural or physiological protection mechanism seems to be superior, and while several unexplained and contradictory patterns exist in zooplankton UVR ecology, recent increases in our understanding are consistent with UVR playing an important role for zooplankton. This review examines the variability in freshwater zooplankton responses to UVR, with a focus on crustacean zooplankton (Cladocera and Copepoda). We present an overview of UVR-induced damages, and the protection and recovery mechanisms freshwater zooplankton use when exposed to UVR. We review the current knowledge of UVR impact on freshwater zooplankton at species and community levels, and discuss briefly how global change over the last three decades has influenced the UVR milieu in lakes. PMID:21516254

Rautio, Milla; Tartarotti, Barbara

2011-01-01

121

Correlations between zooplankton assemblages and environmental factors in the downtown rivers of Shanghai, China  

NASA Astrophysics Data System (ADS)

Most urban rivers play an important role in urban flood control and drainage in China, but pollution is fast becoming an issue of greater importance in water management. In this study, 63 zooplankton species were recorded in four downtown rivers in Shanghai between November 2007 and October 2008. Of these, 44 species belonged to the Rotifera, 13 to Cladocera, and six to Copepoda. The three most frequently occurring zooplankton ( Brachionus calyciflorus, Microcyclops leuckarti, and Asplanchna priodonta) accounted for 80.00%, 76.84%, and 53.68%, respectively. Rotifera were found to be dominant, comprising 86.26% of total zooplankton, while cladoceran and copepod abundance amounted to 5.08% and 8.67%, respectively. Water temperature, salinity, electrical conductivity, and total nitrogen were of the greatest significance in the occurrence of zooplankton. Two species ( Schmackeria forbesi and Lepadella ovalis) were notably more sensitive to environmental factors such as salinity and electrical conductivity than other species. The population size and community were inversely correlated with the increasing nutrient levels of the four rivers, suggesting that the water quality of the four rivers had been gradually recovering from a severe eutrophic state and that water conditions of the rivers had been gradually improved.

Yu, Na; Li, Erchao; Feng, Dexiang; Xiao, Baicai; Wei, Chaoqun; Zhang, Meiling; Chen, Liqiao

2014-11-01

122

The interplay between environmental conditions and allee effects during the recovery of stressed zooplankton communities.  

PubMed

Many important ecological phenomena depend on the success or failure of small introduced populations. Several factors are thought to influence the fate of small populations, including resource and habitat availability, dispersal levels, interspecific interactions, mate limitation, and demographic stochasticity. Recent field studies suggest that Allee effects resulting from mate limitation can prevent the reestablishment of sexual zooplankton species following a disturbance. In this study, we explore the interplay between Allee effects and local environmental conditions in determining the population growth and establishment of two acid-sensitive zooplankton species that have been impacted by regional anthropogenic acidification. We conducted a factorial design field experiment to test the impact of pH and initial organism densities on the per capita population growth (r) of the sexual copepod Epischura lacustris and the seasonally parthenogenetic cladoceran Daphnia mendotae. In addition, we conducted computer simulations using r values obtained from our experiments to determine the probability of extinction for small populations of acid-sensitive colonists that are in the process of colonizing recovering lakes. The results of our field experiment demonstrated that local environmental conditions can moderate the impacts of Allee effects for E. lacustris: Populations introduced at low densities had a significantly lower r at pH 6 than at pH 7. In contrast, r did not differ between pH 6 and 7 environments when E. lacustris populations were introduced at high densities. D. mendotae was affected by pH levels, but not by initial organism densities. Results from our population growth simulations indicated that E. lacustris populations introduced at low densities to pH 6 conditions had a higher probability of extinction than those introduced at low densities to a pH 7 environment. Our study indicates that environmental conditions and mate limitation can interact to determine the fate of small populations of sexually reproducing zooplankton species. If a more rapid recovery of acid-damaged zooplankton communities is desired, augmentation of dispersal levels may be needed during the early phases of pH recovery in order to increase the probability of establishment for mate-limited zooplankton species. PMID:22073650

Gray, Derek K; Arnott, Shelley E

2011-10-01

123

Detrital feeding in natural zooplankton communities: Discrimination between live and dead algal foods  

Microsoft Academic Search

Freshwater zooplankton species differ in their consumption of live and dead algal cells when tested in situ. Using isotopically-labeled living and heat-killed Chlamydomonas reinhardti as models for phytoplankton and detrital seston, respectively, we tested differential feeding on these foods by 3 rotifers and 2 microcrustaceans. Keratella cochlearis selectively feeds on ‘detrital’ materials while 2 sympatric rotifer species, Conochilus dossuarius and

Peter L. Starkweather; Kenneth G. Bogdan

1980-01-01

124

Vertical Distribution of Herbivorous Zooplankton in a Well-Mixed Lake System in Which the Main Predator is a Non-Selective Filter-Feeding Fish  

Microsoft Academic Search

The vertical distribution of herbivorous zooplankton was examined over a 24-hr period in Lake Somerville, Texas, a shallow, well-mixed, warrn-water reservoir in which temperature and oxygen gradients rarely occur. While no consistent preference for surface or bottom water was found, diel zooplankton population deficits were observed. Activity of the main planktivore, the non-visual, filter feeding gizzard shad, did not correspond

Elizabeth Fejes; Jenny Birnbaum; Frances Gelwick; Daniel Roelke

2003-01-01

125

A spatial ecosystem and populations dynamics model (SEAPODYM) – Modeling of tuna and tuna-like populations  

Microsoft Academic Search

An enhanced version of the spatial ecosystem and population dynamics model SEAPODYM is presented to describe spatial dynamics of tuna and tuna-like species in the Pacific Ocean at monthly resolution over 1° grid-boxes. The simulations are driven by a bio-physical environment predicted from a coupled ocean physical–biogeochemical model. This new version of SEAPODYM includes expanded definitions of habitat indices, movements,

Patrick Lehodey; Inna Senina; Raghu Murtugudde

2008-01-01

126

Modelling the dynamics of the North Sea's Mesozooplankton  

NASA Astrophysics Data System (ADS)

A simple biomass-only zooplankton submodel is presented, describing the dynamics of copepods and carnivorous zooplankton in the North Sea. This submodel together with the other process-oriented submodels ( viz. phytoplankton dynamics, the microbial food web, benthic processes, fish dynamics and large-scale advective transport) forms a spatially resolved simulation model of the North Sea ecosystem, the European Regional Seas Ecosystem Model (ERSEM). A large set of field measurements of zooplankton abundance has been assembled against which to compare the ERSEM's performance. These data are not only internally consistent, but have also gathered at the large spatial scales appropriate to the ERSEM. In addition to the spatially resolved, monthly estimates of zooplankton abundance, several instantaneous, in situ estimates of the carbon fluxes between different components of the planktonic web in the northern North Sea are presented. Simulated dynamics are in good agreement with the data only during the mid-summer to mid-winter period. During the latter part of the winter and throughout the spring period zooplankton abundance is underpredicted and the simulated zooplankton growth rate is overpredicted during spring. The excessive decline of mesozooplankton biomass during winter may be caused by failing to capture many of the behavioural/physiological changes which zooplankton manifest during winter. It is suggested that the excessive spring growth is a consequence of a. a failure to properly distinguish between somatic and population growth, b. an inadequate representation of the small scale processes which influence feeding success, and c. an excessive spring phytoplankton bloom. The large phytoplankton bloom is, in part at least, a consequence of the excessively low simulated standing crop of omnivorous zooplankton in spring.

Broekhuizen, N.; Heath, M. R.; Hay, S. J.; Gurney, W. S. C.

127

Trade-offs in the vertical distribution of zooplankton: ideal free distribution with costs?  

PubMed Central

Zooplankton vertical migratory patterns are a classic example of optimal habitat choice. We hypothesize that zooplankton distribute themselves vertically in the water column according to an ideal free distribution (IFD) with costs such as to optimize their fitness. In lakes with a deep-water chlorophyll maximum, zooplankton are faced with a trade-off, either experiencing high food (high reproductive potential) but low temperature (slow development) in the hypolimnion or high temperature and low food in the epilimnion. Thus, in the absence of fish predation (e.g. at night) they should allocate the time spent in the different habitats according to fitness gain dependent on the temperature gradient and distribution of food. We tested this hypothesis with a Daphnia hyalina x galeata clone in large indoor columns (Plön Plankton Towers) and with a dynamic energy budget model. In the tower experiments, we simulated a deep-water algal maximum below the thermocline with epilimnetic/hypolimnetic temperature differences of 2, 5 and 10 degrees C. Experimental data supported the model. We found a significantly larger proportion of daphniids in the hypolimnion when the temperature difference was smaller. Our results are consistent with the concept of IFD with costs originally developed for stream fishes. This concept can be applied to predict the vertical distribution of zooplankton in habitats where fish predation is of minor importance. PMID:12713752

Lampert, Winfried; McCauley, Edward; Manly, Bryan F J

2003-01-01

128

Evaluation of the zooplankton community of Livingston Reservoir, Texas, as related to paddlefish food resources  

E-print Network

soon after impoundment (Unkenholz 1986). Out of 26 states that contained paddlefish populations historically, 16 still have active paddlefish fishing (Gengerke 1986). Paddlefish are protected in 6 states, but have been extirpated in New York... include larger crustacean zooplankton (Dephnia sp. , larger cyclopoid and calanoid copepods), aquatic insects, and terrestrial insects (Ruelle and Hudson 1977). As paddlefish mature they begin to develop gill rakers, which are rows of fine filaments...

Moore, Casey Kenneth

2012-06-07

129

The Effects of Differential Digestion Rates of Zooplankton by Alewife, Alosa pseudoharengus, on Determinations of Selective Feeding  

Microsoft Academic Search

Ivlev's electivity index (E) was used to assess selective feeding by the alewife (Alosa pseudoharengus) on crustacean zooplankton in southern Green Bay, Lake Michigan. Alewives positively selected larger species of Copepoda, especially Mesocyclops edax. Alewives appeared to negatively select all Cladocera. However, field data from Lake Michigan and other lakes containing abundant populations of alewives indicate positive selection may be

John E. Gannon

1976-01-01

130

How zooplankton feed: mechanisms, traits and trade-offs.  

PubMed

Zooplankton is a morphologically and taxonomically diverse group and includes organisms that vary in size by many orders of magnitude, but they are all faced with the common problem of collecting food from a very dilute suspension. In order to maintain a viable population in the face of mortality, zooplankton in the ocean have to clear daily a volume of ambient water for prey particles that is equivalent to about 10(6) times their own body volume. While most size-specific vital rates and mortality rates decline with size, the clearance requirement is largely size-independent because food availability also declines with size. There is a limited number of solutions to the problem of concentrating dilute prey from a sticky medium: passive and active ambush feeding; feeding-current feeding, where the prey is either intercepted directly, retained on a filter, or individually perceived and extracted from the feeding current; cruise feeding; and colonization of large particles and marine snow aggregates. The basic mechanics of these food-collection mechanisms are described, and it is shown that their efficiencies are inherently different and that each of these mechanisms becomes less efficient with increasing size. Mechanisms that compensate for this decline in efficiency are described, including inflation of feeding structures and development of vision. Each feeding mode has implications beyond feeding in terms of risk of encountering predators and chance of meeting mates, and they partly target different types of prey. The main dichotomy is between (inefficient) ambush feeding on motile prey and the more efficient active feeding modes; a secondary dichotomy is between (efficient) hovering and (less efficient) cruising feeding modes. The efficiencies of the various feeding modes are traded off against feeding-mode-dependent metabolic expenses, predation risks, and mating chances. The optimality of feeding strategies, evaluated as the ratio of gain over risk, varies with the environment, and may explain both size-dependent and spatio-temporal differences in distributions of various feeding types as well as other aspects of the biology of zooplankton (mating behaviour, predator defence strategies). PMID:20682007

Kiørboe, Thomas

2011-05-01

131

MODELING OF GENE REGULATORY PROCESSES BY POPULATION MEDIATED SIGNALING. NEW APPLICATIONS OF POPULATION BALANCES  

PubMed Central

Population balance modeling is considered for cell populations in gene regulatory processes in which one or more intracellular variables undergo stochastic dynamics as determined by Ito stochastic differential equations. This paper addresses formulation and computational issues with sample applications to the spread of drug resistance among bacterial cells. It is shown that predictions from population balances can display qualitative differences from those made with single cell models which are usually encountered in the literature. Such differences are deemed to be important. PMID:22581980

Shu, Che-Chi; Chatterjee, Anushree; Hu, Wei-Shou

2011-01-01

132

Integrated population models: a novel analysis framework for deeper insights into population dynamics  

E-print Network

estimates become more precise, and this enhances statistical power. Finally, all sources of uncer- tainty State-space model Zusammenfassung Integrierte Populationmodelle (IPM) sind universelle population models allow the estimating of more demographic quantities, because there is information about all

Richner, Heinz

133

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...

134

Evaluating habitat as a surrogate for population viability using a spatially explicit population model.  

PubMed

Because data for conservation planning are always limited, surrogates are often substituted for intractable measurements such as species richness or population viability. We examined the ability of habitat quality to act as a surrogate for population performance for both Red-shouldered Hawks (Buteo lineatus) and Northern Goshawks (Accipiter gentilis). We compared simple measures of habitat quality to estimates of population growth rates obtained from a spatially explicit model of population dynamics. We found that habitat quality was a relatively poor predictor of simulated population growth rates for several reasons. First, a relatively small proportion of the potential habitat for each species served as population sources in our simulations--15% for Red-shouldered Hawks and 2% for Goshawks. Second, when habitat quality correctly predicted demographic sources on the landscape, it consistently underestimated the contribution of these areas to the population. In areas where habitat quality correctly anticipated the presence of demographic sinks, we found no useful quantitative relationship between the two measures. Our simulation model captured the influence of habitat quality on the hawk populations, but it also incorporated interactions between dispersing individuals and landscape patterns. Thus, the discrepancies we observed likely reflected the influence of forest fragmentation and the spatial arrangement of forest patches on the populations. We conclude that simple measures of habitat quality will often be poor surrogates for population persistence, but that spatially explicit population models can help inform the development of better indices. PMID:15141448

Lawler, Joshua J; Schumaker, Nathan H

2004-06-01

135

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...

136

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

137

RESEARCH ARTICLE Modeling population connectivity by ocean currents,  

E-print Network

RESEARCH ARTICLE Modeling population connectivity by ocean currents, a graph-theoretic approach species, population connectivity is determined largely by ocean currents transporting larvae and juveniles this connectivity between distant populations is key to their effective conservation and management. For many marine

Queensland, University of

138

Predation, Competition, and Zooplankton Community Structure: An Experimental Michael Lynch  

E-print Network

not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR-prey interactions are on does not allow a mechanistic interpre- of major significance in structuring fresh- tation of zooplankton community struc- water zooplankton communities (see Hall ture. For instance, while it is well docu

Lynch, Michael

139

COMBO: a defined freshwater culture medium for algae and zooplankton  

Microsoft Academic Search

In order to conduct experiments on interactions between animals and food organisms, it is necessary to develop a medium that adequately supports the growth of both algae and zooplankton without the need to alter the medium to accommodate either the algae or the animals. We devised a freshwater medium, named COMBO, that supports excellent growth of both algae and zooplankton.

Susan S. Kilham; A. Kreeger; Scott G. Lynn; Clyde E. Goulden; Lazaro Herrera

1998-01-01

140

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

141

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

142

Zooplankton of Lake Titicaca on the Bolivian side  

Microsoft Academic Search

The zooplankton, especially the Cladocera and the Copepoda, of Lake Titicaca on the Bolivian side is reported on the basis of a collection made in April 1961. The zooplankton at that time was sparse, consisting only of seven species. Boeckella titicacaeHarding is the dominant copepod and B. occidentalisMarsh is also abundant, as in the previous records obtained by the Percy

Masuzo Uéno

1967-01-01

143

Zooplankton communities of a new pumped storage reservoir  

Microsoft Academic Search

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

Deborah Ulinski Potter; Judy L. Meyer

1982-01-01

144

Temperature effects on phytoplankton diversity - The zooplankton link  

NASA Astrophysics Data System (ADS)

Recent climate warming is expected to affect phytoplankton biomass and diversity in marine ecosystems. Temperature can act directly on phytoplankton (e.g. rendering physiological processes) or indirectly due to changes in zooplankton grazing activity. We tested experimentally the impact of increased temperature on natural phytoplankton and zooplankton communities using indoor mesocosms and combined the results from different experimental years applying a meta-analytic approach. We divided our analysis into three bloom phases to define the strength of temperature and zooplankton impacts on phytoplankton in different stages of bloom development. Within the constraints of an experiment, our results suggest that increased temperature and zooplankton grazing have similar effects on phytoplankton diversity, which are most apparent in the post-bloom phase, when zooplankton abundances reach the highest values. Moreover, we observed changes in zooplankton composition in response to warming and initial conditions, which can additionally affect phytoplankton diversity, because changing feeding preferences of zooplankton can affect phytoplankton community structure. We conclude that phytoplankton diversity is indirectly affected by temperature in the post-bloom phase through changing zooplankton composition and grazing activities. Before and during the bloom, however, these effects seem to be overruled by temperature enhanced bottom-up processes such as phytoplankton nutrient uptake.

Lewandowska, Aleksandra M.; Hillebrand, Helmut; Lengfellner, Kathrin; Sommer, Ulrich

2014-01-01

145

ZOOPLANKTON SIZE-SPECTRA IN GREAT LAKES COASTAL WATERS  

EPA Science Inventory

Zooplankton mean size and size-distribution are affected by planktivore pressure and potentially reflect the condition of trophic interactions and ecosystem health. We used an optical plankton counter (OPC) to survey and assess zooplankton size-spectra for twenty locations in Lak...

146

The role of trophic bottlenecks in stunting: a field test of an allocation model of growth and reproduction in yellow perch, Perca flavescens  

Microsoft Academic Search

Synopsis Stunting in freshwater fish populations may be due to low availability of one or more prey components within their diet. If the limiting prey constitute a trophic level (i.e. zooplankton, benthos, or fish), we define the phenomenon as a trophic bottleneck. Growth of a non-stunted population of yellow perch, Perca flavescens, was simulated using an allocation model based on

Daniel D. Heath; Derek A. Roff

1996-01-01

147

Survival models for harvest management of mourning dove populations  

USGS Publications Warehouse

Quantitative models of the relationship between annual survival and harvest rate of migratory game-bird populations are essential to science-based harvest management strategies. I used the best available band-recovery and harvest data for mourning doves (Zenaida macroura) to build a set of models based on different assumptions about compensatory harvest mortality. Although these models suffer from lack of contemporary data, they can be used in development of an initial set of population models that synthesize existing demographic data on a management-unit scale, and serve as a tool for prioritization of population demographic information needs. Credible harvest management plans for mourning dove populations will require a long-term commitment to population monitoring and iterative population analysis.

Otis, D. L.

2002-01-01

148

Population Growth - Exponential and Logistic Models vs. Complex Reality  

NSDL National Science Digital Library

This analysis and discussion activity is designed to help students develop an intuitive understanding of the exponential and logistic models of population growth, including the biological processes that result in exponential or logistic population growth. Students learn about the simplifying assumptions built into the exponential and logistic models and explore how deviations from these assumptions can result in discrepancies between the predictions of these models and actual trends in population size for natural populations. This activity is designed to help high school students meet the Next Generation Science Standards and the Common Core State Standards.

Waldron, Ingrid

149

Proliferation in Cell Population Models with Age Structure  

NASA Astrophysics Data System (ADS)

We study proliferation in tissues from the point of view of physiologically structured partial differential models, focusing on age synchronisation in the cell division cycle in cell populations and its control at phase transition checkpoints. We show how a recent fluorescence-based technique (FUCCI) performed at the single cell level in proliferating cell populations allows identifying model parameters and how it may be applied to investigate healthy and cancer cell populations. We show how this modelling approach allows designing original optimisation methods for cancer chronotherapeutics, by controlling eigenvalues of differential operators underlying proliferation dynamics, in tumour and in healthy cell populations.

Billy, Frédérique; Clairambault, Jean; Fercoq, Olivier; Gaubert, Stéphane; Lepoutre, Thomas; Ouillon, Thomas

2011-09-01

150

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...

151

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...

152

GIS and plume dispersion modeling for population exposure assessment  

E-print Network

that can prove extremely valuable in the modeling process. This data can serve to extend the capabilities of air pollution dispersion modeling from mere estimation of concentrations to comprehensive exposure assessment of neighboring populations (Lowry, et...

Archer, Jeffrey Keith

2012-06-07

153

Estimation of immigration rate using integrated population models  

E-print Network

Estimation of immigration rate using integrated population models Fitsum Abadi1 *, Olivier Gimenez2 Summary 1. The dynamics of many populations is strongly affected by immigrants. However, estimating and modelling immigration is a real challenge. In the past, several methods have been developed to esti- mate

Richner, Heinz

154

MODELING APPROACHES TO POPULATION-LEVEL RISK AESSESSMENT  

EPA Science Inventory

A SETAC Pellston Workshop on Population-Level Risk Assessment was held in Roskilde, Denmark on 23-27 August 2003. One aspect of this workshop focused on modeling approaches for characterizing population-level effects of chemical exposure. The modeling work group identified th...

155

A spatial ecosystem and populations dynamics model (SEAPODYM) Modeling of tuna and tuna-like populations  

NASA Astrophysics Data System (ADS)

An enhanced version of the spatial ecosystem and population dynamics model SEAPODYM is presented to describe spatial dynamics of tuna and tuna-like species in the Pacific Ocean at monthly resolution over 1° grid-boxes. The simulations are driven by a bio-physical environment predicted from a coupled ocean physical-biogeochemical model. This new version of SEAPODYM includes expanded definitions of habitat indices, movements, and natural mortality based on empirical evidences. A thermal habitat of tuna species is derived from an individual heat budget model. The feeding habitat is computed according to the accessibility of tuna predator cohorts to different vertically migrating and non-migrating micronekton (mid-trophic) functional groups. The spawning habitat is based on temperature and the coincidence of spawning fish with presence or absence of predators and food for larvae. The successful larval recruitment is linked to spawning stock biomass. Larvae drift with currents, while immature and adult tuna can move of their own volition, in addition to being advected by currents. A food requirement index is computed to adjust locally the natural mortality of cohorts based on food demand and accessibility to available forage components. Together these mechanisms induce bottom-up and top-down effects, and intra- (i.e. between cohorts) and inter-species interactions. The model is now fully operational for running multi-species, multi-fisheries simulations, and the structure of the model allows a validation from multiple data sources. An application with two tuna species showing different biological characteristics, skipjack ( Katsuwonus pelamis) and bigeye ( Thunnus obesus), is presented to illustrate the capacity of the model to capture many important features of spatial dynamics of these two different tuna species in the Pacific Ocean. The actual validation is presented in a companion paper describing the approach to have a rigorous mathematical parameter optimization [Senina, I., Sibert, J., Lehodey, P., 2008. Parameter estimation for basin-scale ecosystem-linked population models of large pelagic predators: application to skipjack tuna. Progress in Oceanography]. Once this evaluation and parameterization is complete, it may be possible to use the model for management of tuna stocks in the context of climate and ecosystem variability, and to investigate potential changes due to anthropogenic activities including global warming and fisheries pressures and management scenarios.

Lehodey, Patrick; Senina, Inna; Murtugudde, Raghu

2008-09-01

156

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

157

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

158

Modelling climate-related variability of tuna populations from a coupled ocean-biogeochemical-populations dynamics model  

E-print Network

fields from a 3D coupled physical-biogechemical model. The hypothesis that the spatial dynamics of Marine Science, University of Maine, 5471 Libby Hall, Orono, Maine 04469-5741, USA (fchai populations, a spatial environmental population dynamic model (SEPODYM) has been developed (Bertignac et al

Maine, University of

159

Numerical integration of population models satisfying conservation laws: NSFD methods.  

PubMed

Population models arising in ecology, epidemiology and mathematical biology may involve a conservation law, i.e. the total population is constant. In addition to these cases, other situations may occur for which the total population, asymptotically in time, approach a constant value. Since it is rarely the situation that the equations of motion can be analytically solved to obtain exact solutions, it follows that numerical techniques are needed to provide solutions. However, numerical procedures are only valid if they can reproduce fundamental properties of the differential equations modeling the phenomena of interest. We show that for population models, involving a dynamical conservation law the use of nonstandard finite difference (NSFD) methods allows the construction of discretization schemes such that they are dynamically consistent (DC) with the original differential equations. The paper will briefly discuss the NSFD methodology, the concept of DC, and illustrate their application to specific problems for population models. PMID:22876826

Mickens, Ronald E

2007-10-01

160

Augmenting superpopulation capture-recapture models with population assignment data.  

PubMed

Ecologists applying capture-recapture models to animal populations sometimes have access to additional information about individuals' populations of origin (e.g., information about genetics, stable isotopes, etc.). Tests that assign an individual's genotype to its most likely source population are increasingly used. Here we show how to augment a superpopulation capture-recapture model with such information. We consider a single superpopulation model without age structure, and split each entry probability into separate components due to births in situ and immigration. We show that it is possible to estimate these two probabilities separately. We first consider the case of perfect information about population of origin, where we can distinguish individuals born in situ from immigrants with certainty. Then we consider the more realistic case of imperfect information, where we use genetic or other information to assign probabilities to each individual's origin as in situ or outside the population. We use a resampling approach to impute the true population of origin from imperfect assignment information. The integration of data on population of origin with capture-recapture data allows us to determine the contributions of immigration and in situ reproduction to the growth of the population, an issue of importance to ecologists. We illustrate our new models with capture-recapture and genetic assignment data from a population of banner-tailed kangaroo rats?Dipodomys spectabilis?in Arizona. PMID:21155745

Wen, Zhi; Pollock, Kenneth; Nichols, James; Waser, Peter

2011-09-01

161

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

162

ASYMPTOTICS OF SYMMETRIC COMPOUND POIS-SON POPULATION MODELS  

E-print Network

June 25, 2013 Abstract Compound Poisson population models are particular conditional branching process models. A formula for the transition probabilities of the backward process for general compound Poisson that 1 > 0. Compound Poisson models are particular conditional branching process models where each random

Möhle, Martin

163

ASYMPTOTICS OF SYMMETRIC COMPOUND POIS-SON POPULATION MODELS  

E-print Network

September 10, 2012 Abstract Compound Poisson population models are particular conditional branching process models. A formula for the transition probabilities of the backward process for general compound Poisson-11Sep2012 #12;that 1 > 0. Compound Poisson models are particular conditional branching process models

Paris-Sud XI, Université de

164

Genealogy and subpopulation differentiation under various models of population structure  

Microsoft Academic Search

.  ?The structured coalescent is used to calculate some quantities relating to the genealogy of a pair of homologous genes and\\u000a to the degree of subpopulation differentiation, under a range of models of subdivided populations and assuming the infinite\\u000a alleles model of neutral mutation. The classical island and stepping-stone models of population structure are considered,\\u000a as well as two less symmetric

Hilde M. Wilkinson-Herbots

1998-01-01

165

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

166

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

167

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

168

Stimulus-dependent Maximum Entropy Models of Neural Population Codes  

PubMed Central

Neural populations encode information about their stimulus in a collective fashion, by joint activity patterns of spiking and silence. A full account of this mapping from stimulus to neural activity is given by the conditional probability distribution over neural codewords given the sensory input. For large populations, direct sampling of these distributions is impossible, and so we must rely on constructing appropriate models. We show here that in a population of 100 retinal ganglion cells in the salamander retina responding to temporal white-noise stimuli, dependencies between cells play an important encoding role. We introduce the stimulus-dependent maximum entropy (SDME) model—a minimal extension of the canonical linear-nonlinear model of a single neuron, to a pairwise-coupled neural population. We find that the SDME model gives a more accurate account of single cell responses and in particular significantly outperforms uncoupled models in reproducing the distributions of population codewords emitted in response to a stimulus. We show how the SDME model, in conjunction with static maximum entropy models of population vocabulary, can be used to estimate information-theoretic quantities like average surprise and information transmission in a neural population. PMID:23516339

Segev, Ronen; Schneidman, Elad

2013-01-01

169

Stimulus-dependent maximum entropy models of neural population codes.  

PubMed

Neural populations encode information about their stimulus in a collective fashion, by joint activity patterns of spiking and silence. A full account of this mapping from stimulus to neural activity is given by the conditional probability distribution over neural codewords given the sensory input. For large populations, direct sampling of these distributions is impossible, and so we must rely on constructing appropriate models. We show here that in a population of 100 retinal ganglion cells in the salamander retina responding to temporal white-noise stimuli, dependencies between cells play an important encoding role. We introduce the stimulus-dependent maximum entropy (SDME) model-a minimal extension of the canonical linear-nonlinear model of a single neuron, to a pairwise-coupled neural population. We find that the SDME model gives a more accurate account of single cell responses and in particular significantly outperforms uncoupled models in reproducing the distributions of population codewords emitted in response to a stimulus. We show how the SDME model, in conjunction with static maximum entropy models of population vocabulary, can be used to estimate information-theoretic quantities like average surprise and information transmission in a neural population. PMID:23516339

Granot-Atedgi, Einat; Tka?ik, Gašper; Segev, Ronen; Schneidman, Elad

2013-01-01

170

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

171

A probabilistic model to evaluate population dietary recommendations.  

PubMed

Food-based dietary recommendations (FBR) play an essential role in promoting a healthy diet. To support the process of formulating a set of population-specific FBR, a probabilistic model was developed specifically to predict the changes in the percentage of a population at risk of inadequate nutrient intakes after the adoption of alternative sets of FBR. The model simulates the distribution of the number of servings per week from food groups or food items at baseline and after the hypothetical successful adoption of alternative sets of FBR, while ensuring that the population's energy intake distribution remains similar. The simulated changes from baseline in median nutrient intakes and the percentage of the population at risk of inadequate nutrient intakes are calculated and compared across the alternative sets of FBR. The model was illustrated using a hypothetical population of 12- to 18-month-old breast-feeding children consuming a cereal-based diet low in animal source foods. PMID:24779993

Chalabi, Zaid; Ferguson, Elaine; Stanley, Robert; Briend, André

2014-07-01

172

Modeling the population dynamics of Gulf Coast sandhill cranes  

USGS Publications Warehouse

The Midcontinental population of sandhill cranes (Grus canadensis) has a large geographic range, contains nearly 500,000 birds, and is hunted in much of its range. The population includes three subspecies; the numbers of two of these are uncertain, and they should be afforded protection from hunting that would be detrimental to their population. The two subspecies of concern tend to concentrate in the eastern part of the Great Plains during fall and spring and to winter along the Gulf Coast in Texas. This paper uses the limited information available about the Gulf Coast subpopulation in a model. We included in the model five input parameters: population size, annual survival rate in absence of hunting, the number of birds taken by hunters, the extent of additivity of hunting mortality, and recruitment rate, measured as the fraction of juveniles in the winter population. Using three widely ranging estimates of each parameter, we examined the general behavior of the simulated population. Realistic population projections occurred with medium (60,000) or large (166,000) population sizes, low (2000) or moderate (4000) harvests, and recruitment rates of 0.07 and 0.11. All values of survival in the absence of hunting and additivity of hunting yielded some realistic projections. Results of modelling suggest that the variables warranting closer monitoring are population size and recruitment rate.

Johnson, D.H.; Kendall, W.L.

1997-01-01

173

Population balance models for the thermal degradation of PMMA  

Microsoft Academic Search

A widely accepted view of the thermal degradation of polymers such as PMMA is that an initiation reaction produces radical fragments that undergo rapid depropagation and are also converted back to molecules by a termination reaction. This mechanism is applied to a population of linear molecules and radicals and the evolution of the population is modelled by appropriate discrete sets

J. E. J. Staggs

2007-01-01

174

Dispersion population models discrete in time and continuous in space  

Microsoft Academic Search

We analyze a discrete-time model of populations that grow and disperse in separate phases. The growth phase is a nonlinear process that allows for the effects of local crowding. The dispersion phase is a linear process that distributes the population throughout its spatial habitat. Our study quantifies the issues of survival and extinction, the existence and stability of nontrivial steady

D. P. Hardin; P. Taká?; G. F. Webb

1990-01-01

175

Deterministic mathematical modelling for cancer chronotherapeutics: cell population  

E-print Network

and cancer cell populations in their responses to drugs. To this aim, clear biological evidenceDeterministic mathematical modelling for cancer chronotherapeutics: cell population dynamics for more than twenty years as an effective treatment against cancer by a few teams around the world, among

176

Deterministic mathematical modelling for cancer chronotherapeutics: cell population  

E-print Network

procedures should have little to do with circa- dian biology, i.e., emergence of drug resistance in cancer and cancer cell populations in their responses to drugs. To this aim, clear biological evidenceDeterministic mathematical modelling for cancer chronotherapeutics: cell population dynamics

Paris-Sud XI, Université de

177

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

178

Parasitic chytrids sustain zooplankton growth during inedible algal bloom  

PubMed Central

This study assesses the quantitative impact of parasitic chytrids on the planktonic food web of two contrasting freshwater lakes during different algal bloom situations. Carbon-based food web models were used to investigate the effects of chytrids during the spring diatom bloom in Lake Pavin (oligo-mesotrophic) and the autumn cyanobacteria bloom in Lake Aydat (eutrophic). Linear inverse modeling was employed to estimate undetermined flows in both lakes. The Monte Carlo Markov chain linear inverse modeling procedure provided estimates of the ranges of model-derived fluxes. Model results confirm recent theories on the impact of parasites on food web function through grazers and recyclers. During blooms of “inedible” algae (unexploited by planktonic herbivores), the epidemic growth of chytrids channeled 19–20% of the primary production in both lakes through the production of grazer exploitable zoospores. The parasitic throughput represented 50% and 57% of the zooplankton diet, respectively, in the oligo-mesotrophic and in the eutrophic lakes. Parasites also affected ecological network properties such as longer carbon path lengths and loop strength, and contributed to increase the stability of the aquatic food web, notably in the oligo-mesotrophic Lake Pavin. PMID:24904543

Rasconi, Serena; Grami, Boutheina; Niquil, Nathalie; Jobard, Marlene; Sime-Ngando, Telesphore

2014-01-01

179

How predictable : modeling rates of change in individuals and populations  

E-print Network

This thesis develops methodologies to measure rates of change in individual human behavior, and to capture statistical regularities in change at the population level, in three pieces: i) a model of individual rate of change ...

Krumme, Katherine

2013-01-01

180

Zooplankton Community Metabolic Requirements and the Effect on Particle  

E-print Network

in the Ocean's Twilight Zone Deborah Steinberg Ken Buesseler #12;Sinking particle loss in the "twilight zone" 0 in the twilight zo -microbial decomposition -zooplankton grazing Sinking particles Copepod feeding on aggregate

Buesseler, Ken

181

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...

182

Zooplankton community structure, micro-zooplankton grazing impact, and seston energy content in the St. Johns river system, Florida as influenced by the toxic cyanobacterium Cylindrospermopsis raciborskii  

Microsoft Academic Search

Zooplankton can influence the phytoplankton community through preferential grazing. In turn, nuisance cyanobacteria may affect zooplankton community structure by allowing certain species to out-compete others. We examined zooplankton-phytoplankton interactions, micro-zooplankton (m) grazing, and biochemical components of the seston in the St. Johns River System (SJR), Florida in the presence and absence of the toxin-producing cyanobacterium Cylindrospermopsis raciborskii. We tested whether

Jeremy A. Leonard; Hans W. Paerl

2005-01-01

183

Multiscale modeling of oscillations and spiral waves in Dictyostelium populations  

E-print Network

Unicellular organisms exhibit elaborate collective behaviors in response to environmental cues. These behaviors are controlled by complex biochemical networks within individual cells and coordinated through cell-to-cell communication. Describing these behaviors requires new mathematical models that can bridge scales -- from biochemical networks within individual cells to spatially structured cellular populations. Here, we present a family of multiscale models for the emergence of spiral waves in the social amoeba Dictyostelium discoideum. Our models exploit new experimental advances that allow for the direct measurement and manipulation of the small signaling molecule cAMP used by Dictyostelium cells to coordinate behavior in cellular populations. Inspired by recent experiments, we model the Dictyostelium signaling network as an excitable system coupled to various pre-processing modules. We use this family of models to study spatially unstructured populations by constructing phase diagrams that relate the properties of population-level oscillations to parameters in the underlying biochemical network. We then extend our models to include spatial structure and show how they naturally give rise to spiral waves. Our models exhibit a wide range of novel phenomena including a density dependent frequency change, bistability, and dynamic death due to slow cAMP dynamics. Our modeling approach provides a powerful tool for bridging scales in modeling of Dictyostelium populations.

Javad Noorbakhsh; David Schwab; Allyson Sgro; Thomas Gregor; Pankaj Mehta

2014-07-30

184

Hierarchical Bayesian Modelling for Saccharomyces cerevisiae population dynamics  

Microsoft Academic Search

Hierarchical Bayesian Modelling is powerful however under-used to model and evaluate the risks associated with the development of pathogens in food industry, to predict exotic invasions, species extinctions and development of emerging diseases, or to assess chemical risks. Modelling population dynamics of Saccharomyces cerevisiae considering its biodiversity and other sources of variability is crucial for selecting strains meeting industrial needs.

Aymé Spor; Christine Dillmann; Shaoxiao Wang; Dominique de Vienne; Delphine Sicard; Eric Parent

2010-01-01

185

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

186

A STAGE-BASED MODEL OF MANATEE POPULATION DYNAMICS  

Microsoft Academic Search

A stage-structured population model for the Florida manatee (Trichechus manatus latirostris) was developed that explicitly incorporates uncertainty in parameter estimates. The growth rates calculated with this model reflect the status of the regional populations over the most recent 10-yr period. The Northwest and Upper St. Johns River regions have growth rates (k) of 1.037 (95% interval, 1.016- 1.056) and 1.062

Michael C. Runge; Catherine A. Langtimm; William L. Kendall

2004-01-01

187

Model stars for the modelling of galaxies: $?$-enhancement in stellar populations models  

E-print Network

Stellar population (SP) models are an essential tool to understand the observations of galaxies and clusters. One of the main ingredients of a SP model is a library of stellar spectra, and both empirical and theoretical libraries can been used for this purpose. Here I will start by giving a short overview of the pros and cons of using theoretical libraries, i.e. model stars, to produce our galaxy models. Then I will address the question on how theoretical libraries can be used to model stellar populations, in particular to explore the effect of $\\alpha$-enhancement on spectral observables.

P. Coelho

2008-02-19

188

Habitat structure and juvenile fish ontogeny shape zooplankton spring dynamics  

Microsoft Academic Search

Macrophytes in shallow lakes have the potential to alter fish–zooplankton interactions considerably. How far predation effects\\u000a by newly hatched fish (0+ fish) on zooplankton are influenced by different types of aquatic vegetation, and how effects change\\u000a during the first weeks of fish ontogeny remains, however, less clear. In order to address these issues, we examined the predation\\u000a effects of 0+

Alice Nicolle; Lars-Anders Hansson; Christer Brönmark

2010-01-01

189

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

190

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

191

Towards a Model of the Trans-Neptunian Binary Population  

NASA Astrophysics Data System (ADS)

The trends of binary properties across all classes of trans-Neptunian Objects and all size and separation regimes provide important constraints on the dynamical environment and history of the outer Solar System. To date, no population model has been developed, tested, and published that simultaneously considers binary mutual orbit distributions, component size ratios, photometric colors, and conditional occurrence frequency depending on primary size and host population. Here I present the first efforts to develop such a model, and apply it to existing catalogs of trans-Neptunian binaries to extract new estimates of the characteristics of this valuable population.

Parker, Alex H.; Noll, Keith S.

2014-11-01

192

A model of northern pintail productivity and population growth rate  

USGS Publications Warehouse

Our objective was to synthesize individual components of reproductive ecology into a single estimate of productivity and to assess the relative effects of survival and productivity on population dynamics. We used information on nesting ecology, renesting potential, and duckling survival of northern pintails (Anas acuta) collected on the Yukon-Kuskokvim Delta (Y-K Delta), Alaska, 1991-95, to model the number of ducklings produced under a range of nest success and duckling survival probabilities. Using average values of 25% nest success, 11% duckling survival, and 56% renesting probability from our study population, we calculated that all young in our population were produced by 13% of the breeding females, and that early-nesting females produced more young than later-nesting females. Further, we calculated, on average, that each female produced only 0.16 young females/nesting season. We combined these results with estimates of first-year and adult survival to examine the growth rate (??) of the population and the relative contributions of these demographic parameters to that growth rate. Contrary to aerial survey data, the population projection model suggests our study population is declining rapidly (?? = 0.6969). The relative effects on population growth rate were 0.1175 for reproductive success, 0.1175 for first-year survival, and 0.8825 for adult survival. Adult survival had the greatest influence on ?? for our population, and this conclusion was robust over a range of survival and productivity estimates. Given published estimates of annual survival for adult females (61%), our model suggested nest success and duckling survival need to increase to approximately 40% to achieve population stability. We discuss reasons for the apparent discrepancy in population trends between our model and aerial surveys in terms of bias in productivity and survival estimates.

Flint, P.L.; Grand, J.B.; Rockwell, R.F.

1998-01-01

193

Modeling bacterial population growth from stochastic single-cell dynamics.  

PubMed

A few bacterial cells may be sufficient to produce a food-borne illness outbreak, provided that they are capable of adapting and proliferating on a food matrix. This is why any quantitative health risk assessment policy must incorporate methods to accurately predict the growth of bacterial populations from a small number of pathogens. In this aim, mathematical models have become a powerful tool. Unfortunately, at low cell concentrations, standard deterministic models fail to predict the fate of the population, essentially because the heterogeneity between individuals becomes relevant. In this work, a stochastic differential equation (SDE) model is proposed to describe variability within single-cell growth and division and to simulate population growth from a given initial number of individuals. We provide evidence of the model ability to explain the observed distributions of times to division, including the lag time produced by the adaptation to the environment, by comparing model predictions with experiments from the literature for Escherichia coli, Listeria innocua, and Salmonella enterica. The model is shown to accurately predict experimental growth population dynamics for both small and large microbial populations. The use of stochastic models for the estimation of parameters to successfully fit experimental data is a particularly challenging problem. For instance, if Monte Carlo methods are employed to model the required distributions of times to division, the parameter estimation problem can become numerically intractable. We overcame this limitation by converting the stochastic description to a partial differential equation (backward Kolmogorov) instead, which relates to the distribution of division times. Contrary to previous stochastic formulations based on random parameters, the present model is capable of explaining the variability observed in populations that result from the growth of a small number of initial cells as well as the lack of it compared to populations initiated by a larger number of individuals, where the random effects become negligible. PMID:24928885

Alonso, Antonio A; Molina, Ignacio; Theodoropoulos, Constantinos

2014-09-01

194

Role of two toxin-producing plankton and their effect on phytoplankton-zooplankton system--a mathematical study supported by experimental findings.  

PubMed

Plankton is the basis of the entire aquatic food chain. Phytoplankton, in particular, occupies the first trophic level. Plankton performs services for the Earth: it serves as food for marine life, gives off oxygen and also absorbs half of the carbon dioxide from the Earth's atmosphere. The dynamics of a rapid (or massive) increase or decrease of plankton populations is an important subject in marine plankton ecology and generally termed as a 'bloom'. Harmful algal blooms (HABs) have adverse effects on human health, fishery, tourism, and the environment. In recent years, considerable scientific attention has been given to HABs. Toxic substances released by harmful plankton play an important role in this context. In this paper, a mathematical model consisting of two harmful phytoplankton and zooplankton system will be discussed. The analytical findings will be verified through our experimental observations which were carried out on the eastern part of Bay of Bengal for the last three years. PMID:15740831

Sarkar, R R; Pal, S; Chattopadhyay, J

2005-04-01

195

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

196

A hierarchical model for estimating change in American Woodcock populations  

USGS Publications Warehouse

The Singing-Ground Survey (SGS) is a primary source of information on population change for American woodcock (Scolopax minor). We analyzed the SGS using a hierarchical log-linear model and compared the estimates of change and annual indices of abundance to a route regression analysis of SGS data. We also grouped SGS routes into Bird Conservation Regions (BCRs) and estimated population change and annual indices using BCRs within states and provinces as strata. Based on the hierarchical model?based estimates, we concluded that woodcock populations were declining in North America between 1968 and 2006 (trend = -0.9%/yr, 95% credible interval: -1.2, -0.5). Singing-Ground Survey results are generally similar between analytical approaches, but the hierarchical model has several important advantages over the route regression. Hierarchical models better accommodate changes in survey efficiency over time and space by treating strata, years, and observers as random effects in the context of a log-linear model, providing trend estimates that are derived directly from the annual indices. We also conducted a hierarchical model analysis of woodcock data from the Christmas Bird Count and the North American Breeding Bird Survey. All surveys showed general consistency in patterns of population change, but the SGS had the shortest credible intervals. We suggest that population management and conservation planning for woodcock involving interpretation of the SGS use estimates provided by the hierarchical model.

Sauer, J.R.; Link, W.A.; Kendall, W.L.; Kelley, J.R.; Niven, D.K.

2008-01-01

197

[Firing-rate model of a population of adaptive neurons].  

PubMed

A firing rate (FR) model for a population of adaptive integrate-and-fire (IF) neurons has been proposed. Unlike known FR models, it describes more precisely the unsteady firing regimes and takes into account the effect of slow potassium currents of spike-time adaptation. Approximations of the adaptive channel conductances are rewritten from voltage-dependent to spike-dependent and then to rate-dependent ones. The proposed FR model is compared to the very detailed population model, namely, the conductance-based refractory density model. The comparison of this model with the full RD model shows the coincidence of the first peak of activity after the start of stimulation as well as the stationary state. As an example of the simulation of coupled adaptive neuronal populations, a ring model has been constructed, which reproduces a visual illusion named tilt after-effect. The FR model is recommended for the mathematical analysis of neuronal population activity as well as for computationally expensive large-scale simulations. PMID:20968079

Buchin, A Iu; Chizhov, A V

2010-01-01

198

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

199

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

200

Modeling structured population dynamics using data from unmarked individuals.  

PubMed

The study of population dynamics requires unbiased, precise estimates of abundance and vital rates that account for the demographic structure inherent in all wildlife and plant populations. Traditionally, these estimates have only been available through approaches that rely on intensive mark-recapture data. We extended recently developed N-mixture models to demonstrate how demographic parameters and abundance can be estimated for structured populations using only stage-structured count data. Our modeling framework can be used to make reliable inferences on abundance as well as recruitment, immigration, stage-specific survival, and detection rates during sampling. We present a range of simulations to illustrate the data requirements, including the number of years and locations necessary for accurate and precise parameter estimates. We apply our modeling framework to a population of northern dusky salamanders (Desmognathus fuscus) in the mid-Atlantic region (USA) and find that the population is unexpectedly declining. Our approach represents a valuable advance in the estimation of population dynamics using multistate data from unmarked individuals and should additionally be useful in the development of integrated models that combine data from intensive (e.g., mark-recapture) and extensive (e.g., counts) data sources. PMID:24649642

Zipkin, Elise F; Thorson, James T; See, Kevin; Lynch, Heather J; Grant, Evan H Campbell; Kanno, Yoichiro; Chandler, Richard B; Letcher, Benjamin H; Royle, J Andrew

2014-01-01

201

Population stratification using a statistical model on hypergraphs  

NASA Astrophysics Data System (ADS)

Population stratification is a problem encountered in several areas of natural science, engineering, and public health. We tackle this problem by mapping a population and its element attributes onto a hypergraph, a natural extension of the concept of graph or network to encode associations among any number of elements. On this hypergraph, we construct a statistical model reflecting our intuition about how the element attributes can emerge from a postulated population structure. Finally, we introduce the concept of stratification representativeness as a mean to identify the simplest stratification already containing most of the information about the population structure. We demonstrate the power of this framework stratifying an animal and a human population based on phenotypic and genotypic properties, respectively.

Vazquez, Alexei

2008-06-01

202

Population stratification using a statistical model on hypergraphs  

E-print Network

Population stratification is a problem encountered in several areas of biology and public health. We tackle this problem by mapping a population and its elements attributes into a hypergraph, a natural extension of the concept of graph or network to encode associations among any number of elements. On this hypergraph, we construct a statistical model reflecting our intuition about how the elements attributes can emerge from a postulated population structure. Finally, we introduce the concept of stratification representativeness as a mean to identify the simplest stratification already containing most of the information about the population structure. We demonstrate the power of this framework stratifying an animal and a human population based on phenotypic and genotypic properties, respectively.

Vazquez, Alexei

2007-01-01

203

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

204

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

205

A Diffusion Model in Population Genetics with Mutation and Dynamic  

E-print Network

A Diffusion Model in Population Genetics with Mutation and Dynamic Fitness Mike O'Leary Department of Mathematics Towson University May 24, 2008 Mike O'Leary (Towson University) A Diffusion Model in Genetics May determine the long-time behavior of the total genetic variance? Portions of this work are joint with Judith

O'Leary, Michael

206

A POPULATION EXPOSURE MODEL FOR PARTICULATE MATTER: SHEDS-PM  

EPA Science Inventory

The US EPA National Exposure Research Laboratory (NERL) has developed a population exposure and dose model for particulate matter (PM) that will be publicly available in Fall 2002. The Stochastic Human Exposure and Dose Simulation (SHEDS-PM) model uses a probabilistic approach ...

207

Permanence of delayed population model with dispersal loss  

Microsoft Academic Search

Permanence of a dispersal single-species population model where environment is partitioned into several patches is considered. The species not only requires some time to disperse between the patches but also has some possibility to die during its dispersion. The model is described by delay differential equations. The existence of ‘super’ food-rich patch is proved to be sufficient to ensure partial

Yasuhiro Takeuchi; Jing’an Cui; Rinko Miyazaki; Yasuhisa Saito

2006-01-01

208

Population balance based modelling of nickel laterite agglomeration behaviour  

Microsoft Academic Search

Agglomeration of fine mineral particles as a precursor to heap leaching is an important means of enhancing leaching rates and metal recoveries, particularly in processing low grade ores. In this paper, the modelling of a batch drum agglomeration process applied to nickel laterite using population balance model is explored. The coalescence kernels which are linked to feed material and agglomerator

L. X. Liu; D. J. Robinson; J. Addai-Mensah

209

Aquatic mesocosm assessments of a neem (azadirachtin) insecticide at environmentally realistic concentrations—2: zooplankton community responses and recovery  

Microsoft Academic Search

A neem-based insecticide, Neemix 4.5, was applied to forest pond enclosures at environmentally realistic concentrations (i.e., below the worst-case expected environmental concentration of 35?gL?1). Crustacean zooplankton communities were examined by multivariate ordination (nonmetric multidimensional scaling) and time-course analyses of population trends among indicator taxa over two field seasons to determine application effects on community structure and recovery patterns. Significant effects

David P. Kreutzweiser; Richard C. Back; Trent M. Sutton; Kevin L. Pangle; Dean G. Thompson

2004-01-01

210

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

211

A non-linear population model of diabetes mellitus  

Microsoft Academic Search

A mathematical study of the size of a population ofdiabetes mellitus patients is carried out in this paper. The study also monitors the number of patients with complications. By appropriate\\u000a definition of a parameter, the mathematical model may be classified as linear or non-linear. The non-linear case is discussed\\u000a and the critical values of the population are analysed for stability.

A. Boutayeb; A. Chetouani; A. Achouyab; E. H. Twizell

2006-01-01

212

A model for dengue disease with variable human population  

Microsoft Academic Search

.  ?A model for the transmission of dengue fever with variable human population size is analyzed. We find three threshold parameters\\u000a which govern the existence of the endemic proportion equilibrium, the increase of the human population size, and the behaviour\\u000a of the total number of human infectives. We prove the global asymptotic stability of the equilibrium points using the theory\\u000a of

Lourdes Esteva; Cristobal Vargas

1999-01-01

213

Demographic modeling of transient amplifying cell population growth.  

PubMed

Quantitative measurement for the timings of cell division and death with the application of mathematical models is a standard way to estimate kinetic parameters of cellular proliferation. On the basis of label-based measurement data, several quantitative mathematical models describing short-term dynamics of transient cellular proliferation have been proposed and extensively studied. In the present paper, we show that existing mathematical models for cell population growth can be reformulated as a specific case of generation progression models, a variant of parity progression models developed in mathematical demography. Generation progression ratio (GPR) is defined for a generation progression model as an expected ratio of population increase or decrease via cell division. We also apply a stochastic simulation algorithm which is capable of representing the population growth dynamics of transient amplifying cells for various inter-event time distributions of cell division and death. Demographic modeling and the application of stochastic simulation algorithm presented here can be used as a unified platform to systematically investigate the short term dynamics of cell population growth. PMID:24245725

Nakaoka, Shinji; Inaba, Hisashi

2014-04-01

214

Modeling population patterns of chemotactic bacteria in homogeneous porous media.  

PubMed

The spatio-temporal distribution of subsurface microorganisms determines their efficiency in providing essential ecosystem services such as the degradation of organic matter, the remineralization of carbon and nitrogen, or the remediation of anthropogenic contaminants. Populations of motile, chemotactic bacteria have been shown to be capable of pattern formation even in the absence of environmental heterogeneities. Focusing on the water saturated domain of the subsurface (e.g., aquatic sediments, porous aquifers), we analyze this innate capability of bacterial populations in an idealized model of a homogeneous, saturated porous medium. Considering a linear array of connected, identical microhabitats populated by motile, chemotactic bacterial cells, we identify prerequisites for pattern formation, analyze types of patterns, and assess their impact on substrate utilization. In our model, substrate supplied to the microhabitats facilitates bacterial growth, and microbial cells can migrate between neighboring microhabitats due to (i) random motility, (ii) chemotaxis towards substrate, and (iii) self-attraction. A precondition for inhomogeneous population patterns is analytically derived, stating that patterns are possible if the self-attraction exceeds a threshold defined by the random motility and the steady state population density in the microhabitats. An individual-based implementation of the model shows that static and dynamic population patterns can unfold. Degradation efficiency is highest for homogeneous bacterial distributions and decreases as pattern formation commences. If during biostimulation efforts the carrying capacity of the microhabitats is successively increased, simulation results show that degradation efficiency can unexpectedly decrease when the pattern formation threshold is crossed. PMID:21824482

Centler, Florian; Fetzer, Ingo; Thullner, Martin

2011-10-21

215

[Non-predatory mortality of the crustacean zooplankton and its possible causes (a literature review)].  

PubMed

General mortality (death rate, d) in natural populations of the crustacean zooplankton is calculated as difference between birth rate (b) and population growth rate (r). The mortality includes both predatory (consumptive) and non-predatory (non-consumptive), or "natural", deaths of individuals due to senescence, diseases and parasites, starvation, limiting physical and chemical factors of anthropogenic or natural origin. Modem methods of evaluation of non-predatory mortality of the plankton crustaceans, including direct method based on live/dead sorting by special staining of samples and measurements of sedimentation rate of dead individuals using a sedimentation trap are briefly characterized. Possible causes of non-predatory mortality of crustacean are examined based on different (mainly fresh) temperate water bodies. The possible causes are classified as: physical conditions including temperature, wind effects, ultraviolet radiation, water turbidity, current velocity; chemical conditions including concentration of dissolved oxygen, pH value, water toxicity of both anthropogenic (due to pollutant inflow) and natural (due to cyanobacterial bloom and ingestion of some toxic diatoms by copepods) origin; parasites and epibionts; bottom-up factors or food limitation including quantity and quality of food, the former as content of carbon (energy) and the latter as content of essential compounds in food. It is concluded that, for the populations of crustacean herbivorous zooplankton, the biotic factors appeared to be more important and more probable causes of non-predatory mortality than the abiotic ones, under conditions of non-acid water bodies of the temperate zone when the current speed is less than critical one (0.25 m/c) and in absence of the anthropogenic toxicants. These factors are primarily a food poor quality due to low content of phosphorus, nitrogen, polyunsaturated fatty acids of omega3 family and others, as well as microparasites causing infections and, to a lesser extent (just in blooming water bodies), natural toxicity of cyanobacteria. Non-optimal for the zooplankton physical and chemical factors, as causes of non-predatory mortality of plankton crustaceans, appeared to be less important because of their acting episodically in time locally in space, so the zooplankton is able to avoid their effects and to regenerate fast. PMID:19425353

Dubovskaia, O P

2009-01-01

216

Carbon intake by zooplankton. Importance and role of zooplankton grazing in the Indian sector of the Southern Ocean  

NASA Astrophysics Data System (ADS)

Ingestion by mesozooplankton and micronekton was monitored during two of the ANTARES cruises in the Indian sector of the Southern Ocean in spring and summer. The composition of the mesozooplankton populations varied in space and with season. Copepods always dominated in number and biomass, but salps and pteropods were present in the northern part of the transect in summer. Five species of large copepod ( Calanus simillimus, Calanoides acutus, Rhincalanus gigas, Calanus propinquus and Metridia gerlachei) dominated the biomass with a North-South gradient. Smaller species ( Oithona spp., Ctenocalanus citer, Clausocalanus laticeps) were also present. Biomass showed a definite trend with highest levels towards the polar front zone and permanent open-ocean area. Feeding activity was monitored either for the total population (summer) or specific individuals (spring). In summer, depending on the area considered, grazing rates by mesozooplankton appeared to have a significant impact on phytoplankton primary production. In the northern part of the transect (polar front zone or PFZ), salps and to a minor extent pteropods and copepods contributed mostly to the feeding pressure. Maximum intensity was observed in the Coastal Antarctic Zone (CCSZ) where Euphausia superba (adults and calyptopis larvae) could ingest more than 100% of the daily primary production. In spring, the impact of copepods dominated the zooplankton community. Small calanoids and young stages of large species of copepods rather than adult stages were the dominant contributors to grazing pressure. In summer, respiration rates of the dominant copepod species showed that energy expenditure exceeded by far chlorophyll ingestion. This is generally interpreted as the consequence of ingestion of alternate non-chlorophyll food source. The inverse correlation between the biomass of microzooplankton and the area of maximum difference between grazing and respiration confirmed that in summer the protozoans are strongly controlled by the copepod community.

Mayzaud, P.; Tirelli, V.; Errhif, A.; Labat, J. P.; Razouls, S.; Perissinotto, R.

217

Time-delayed coupled logistic capacity model in population dynamics  

NASA Astrophysics Data System (ADS)

This study proposes a delay-coupled system based on the logistic equation that models the interaction of a population with its varying environment. The integro-diferential equations of the model are presented in terms of a distributed time-delayed coupled logistic-capacity equation. The model eliminates the need for a prior knowledge of the maximum saturation environmental carrying capacity value. Therefore the dynamics toward the final attractor in a distributed time-delayed coupled logistic-capacity model is studied. Exact results are presented, and analytical conclusions have been done in terms of the two parameters of the model.

Cáceres, Manuel O.

2014-08-01

218

Time-delayed coupled logistic capacity model in population dynamics.  

PubMed

This study proposes a delay-coupled system based on the logistic equation that models the interaction of a population with its varying environment. The integro-diferential equations of the model are presented in terms of a distributed time-delayed coupled logistic-capacity equation. The model eliminates the need for a prior knowledge of the maximum saturation environmental carrying capacity value. Therefore the dynamics toward the final attractor in a distributed time-delayed coupled logistic-capacity model is studied. Exact results are presented, and analytical conclusions have been done in terms of the two parameters of the model. PMID:25215718

Cáceres, Manuel O

2014-08-01

219

Population based models of cortical drug response: insights from anaesthesia  

PubMed Central

A great explanatory gap lies between the molecular pharmacology of psychoactive agents and the neurophysiological changes they induce, as recorded by neuroimaging modalities. Causally relating the cellular actions of psychoactive compounds to their influence on population activity is experimentally challenging. Recent developments in the dynamical modelling of neural tissue have attempted to span this explanatory gap between microscopic targets and their macroscopic neurophysiological effects via a range of biologically plausible dynamical models of cortical tissue. Such theoretical models allow exploration of neural dynamics, in particular their modification by drug action. The ability to theoretically bridge scales is due to a biologically plausible averaging of cortical tissue properties. In the resulting macroscopic neural field, individual neurons need not be explicitly represented (as in neural networks). The following paper aims to provide a non-technical introduction to the mean field population modelling of drug action and its recent successes in modelling anaesthesia. PMID:19003456

Bojak, Ingo; Liley, David T. J.

2008-01-01

220

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

2013-02-01

221

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

222

Modeling population access to New Zealand public hospitals  

PubMed Central

This paper demonstrates a method for estimating the geographical accessibility of public hospitals. Cost path analysis was used to determine the minimum travel time and distance to the closest hospital via a road network. This analysis was applied to 38,000 census enumeration district centroids in New Zealand allowing geographical access to be linked to local populations. Average time and distance statistics have been calculated for local populations by modeling the total travel of a population if everybody visited a hospital once. These types of statistics can be generated for different population groups and enable comparisons to be made between regions. This study has shown that the northern and southern parts of New Zealand have high average travel times to hospital services. PMID:12459048

Brabyn, Lars; Skelly, Chris

2002-01-01

223

GIS-Based Population Model Applied to Nevada Transportation Routes  

SciTech Connect

Recently, a model based on geographic information system (GIS) processing of US Census Block data has made high-resolution population analysis for transportation risk analysis technically and economically feasible. Population density bordering each kilometer of a route may be tabulated with specific route sections falling into each of three categories (Rural, Suburban or Urban) identified for separate risk analysis. In addition to the improvement in resolution of Urban areas along a route, the model provides a statistically-based correction to population densities in Rural and Suburban areas where Census Block dimensions may greatly exceed the 800-meter scale of interest. A semi-automated application of the GIS model to a subset of routes in Nevada (related to the Yucca Mountain project) are presented, and the results compared to previous models including a model based on published Census and other data. These comparisons demonstrate that meaningful improvement in accuracy and specificity of transportation risk analyses is dependent on correspondingly accurate and geographically-specific population density data.

Mills, G.S.; Neuhauser, K.S.

1999-03-04

224

Birth-death branching models. Application to African elephant populations.  

PubMed

Branching models have a long history of biological applications, particularly in population dynamics. In this work, our interest is the development of mathematical models to describe the demographic dynamics of socially structured animal populations, focusing our attention on lineages, usually matrilines, as the basic structure in the population. Significant efforts have been made to develop models based on the assumption that all individuals behave identically with respect to reproduction. However, the reproduction phase has a large random component that involves not only demographic but also environmental factors that change across range distribution of species. In the present work, we introduce new classes of birth-death branching models which take such factors into account. We assume that both, the offspring probability distribution and the death probabilities may be different in each generation, changing either predictably or unpredictably in relation to habitat features. We consider the genealogical tree generated by observation of the process until a pre-set generation. We determine the probability distributions of the random variables representing the number of dead or living individuals having at least one ancestor alive, living individuals whose ancestors are all dead, and dead individuals whose ancestors are all dead, explicitly obtaining their principal moments. Also, we derive the probability distributions corresponding to the partial and total numbers of such biological variables, obtaining in particular the distribution of the total number of matriarchs in the genealogical tree. We apply the proposed models to describe the demographic dynamics of African elephant populations living in different habitats. PMID:23648183

Corbacho, Casimiro; Molina, Manuel; Mota, Manuel; Ramos, Alfonso

2013-09-01

225

YONSEI EVOLUTIONARY POPULATION SYNTHESIS (YEPS) MODEL. I. SPECTROSCOPIC EVOLUTION OF SIMPLE STELLAR POPULATIONS  

SciTech Connect

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 {alpha}-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, E-mail: ywlee2@yonsei.ac.kr [Department of Astronomy and Center for Galaxy Evolution Research, Yonsei University, Seoul 120-749 (Korea, Republic of)

2013-01-15

226

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

227

A population balance model for high shear granulation  

Microsoft Academic Search

In a previous paper, Hoornaert et al. ( Powder Technol. 96 (1998); 116-128) presented data from granulation experiments performed in a 50 L Lödige high shear mixer. In this study that same data was simulated with a population balance model. Based on an analysis of the experimental data, the granulation process was divided into three separate stages: nucleation, induction, and

Philippe A. L. Wauters; Brian Scarlett; L. X. Liu; James D. Litster; Gabrie M. H. Meesters

2003-01-01

228

Lie algebra method for solving biological population model  

NASA Astrophysics Data System (ADS)

In this paper, the Lie algebraic method is applied to solve biological population models described by time-inhomogeneous birth-death processes. Notwithstanding no obvious symmetry, the solution is expressed by matrix exponentials through suitably generated low-dimensional Lie algebras. This methodology may offer useful insights for other biological and ecological applications.

Shang, Yilun

2013-12-01

229

Stochastic description of the deterministic Ricker's population model  

E-print Network

We adopt the '0-1' test for chaos using Brownian motion chains to identify the dynamics of the Ricker's population model. In the '0-1' test '0' is related to regular motion while '1' is associated with chaotic motion. The identified regular and chaotic types of solutions have been confirmed by means of recurrence plots.

Arkadiusz Syta; Grzegorz Litak

2006-10-09

230

Modeling the Evolutionary Dynamics of Plasmids in Spatial Populations  

E-print Network

or misunderstood phenomena. However, such models rarely incorporate horizontal gene transfer, so they may be inca conjugation, one mechanism of horizontal gene transfer, can be maintained in populations. We investigate how, horizontal gene transfer, antibiotic resistance, digital evolution Permission to make digital or hard copies

231

Survival, extinction and ergodicity in a spatially continuous population model  

E-print Network

Survival, extinction and ergodicity in a spatially continuous population model N. Berestycki, A of varying intensity allows for the possibility of large-scale extinction and recoloni- sation, ergodicity, survival, extinction, diffusion approximation 1 #12;of the number of offspring of each individual

Berestycki, Nathanaël

232

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

233

High Mortality of Red Sea Zooplankton under Ambient Solar Radiation  

PubMed Central

High solar radiation along with extreme transparency leads to high penetration of solar radiation in the Red Sea, potentially harmful to biota inhabiting the upper water column, including zooplankton. Here we show, based on experimental assessments of solar radiation dose-mortality curves on eight common taxa, the mortality of zooplankton in the oligotrophic waters of the Red Sea to increase steeply with ambient levels of solar radiation in the Red Sea. Responses curves linking solar radiation doses with zooplankton mortality were evaluated by exposing organisms, enclosed in quartz bottles, allowing all the wavelengths of solar radiation to penetrate, to five different levels of ambient solar radiation (100%, 21.6%, 7.2%, 3.2% and 0% of solar radiation). The maximum mortality rates under ambient solar radiation levels averaged (±standard error of the mean, SEM) 18.4±5.8% h?1, five-fold greater than the average mortality in the dark for the eight taxa tested. The UV-B radiation required for mortality rates to reach ½of maximum values averaged (±SEM) 12±5.6 h?1% of incident UVB radiation, equivalent to the UV-B dose at 19.2±2.7 m depth in open coastal Red Sea waters. These results confirm that Red Sea zooplankton are highly vulnerable to ambient solar radiation, as a consequence of the combination of high incident radiation and high water transparency allowing deep penetration of damaging UV-B radiation. These results provide evidence of the significance of ambient solar radiation levels as a stressor of marine zooplankton communities in tropical, oligotrophic waters. Because the oligotrophic ocean extends across 70% of the ocean surface, solar radiation can be a globally-significant stressor for the ocean ecosystem, by constraining zooplankton use of the upper levels of the water column and, therefore, the efficiency of food transfer up the food web in the oligotrophic ocean. PMID:25309996

Al-Aidaroos, Ali M.; El-Sherbiny, Mohsen M. O.; Satheesh, Sathianeson; Mantha, Gopikrishna; Agusti, Susana; Carreja, Beatriz; Duarte, Carlos M.

2014-01-01

234

High Mortality of Red Sea Zooplankton under Ambient Solar Radiation.  

PubMed

High solar radiation along with extreme transparency leads to high penetration of solar radiation in the Red Sea, potentially harmful to biota inhabiting the upper water column, including zooplankton. Here we show, based on experimental assessments of solar radiation dose-mortality curves on eight common taxa, the mortality of zooplankton in the oligotrophic waters of the Red Sea to increase steeply with ambient levels of solar radiation in the Red Sea. Responses curves linking solar radiation doses with zooplankton mortality were evaluated by exposing organisms, enclosed in quartz bottles, allowing all the wavelengths of solar radiation to penetrate, to five different levels of ambient solar radiation (100%, 21.6%, 7.2%, 3.2% and 0% of solar radiation). The maximum mortality rates under ambient solar radiation levels averaged (±standard error of the mean, SEM) 18.4±5.8% h-1, five-fold greater than the average mortality in the dark for the eight taxa tested. The UV-B radiation required for mortality rates to reach ½of maximum values averaged (±SEM) 12±5.6 h-1% of incident UVB radiation, equivalent to the UV-B dose at 19.2±2.7 m depth in open coastal Red Sea waters. These results confirm that Red Sea zooplankton are highly vulnerable to ambient solar radiation, as a consequence of the combination of high incident radiation and high water transparency allowing deep penetration of damaging UV-B radiation. These results provide evidence of the significance of ambient solar radiation levels as a stressor of marine zooplankton communities in tropical, oligotrophic waters. Because the oligotrophic ocean extends across 70% of the ocean surface, solar radiation can be a globally-significant stressor for the ocean ecosystem, by constraining zooplankton use of the upper levels of the water column and, therefore, the efficiency of food transfer up the food web in the oligotrophic ocean. PMID:25309996

Al-Aidaroos, Ali M; El-Sherbiny, Mohsen M O; Satheesh, Sathianeson; Mantha, Gopikrishna; Agust?, Susana; Carreja, Beatriz; Duarte, Carlos M

2014-01-01

235

A nonlinear structured population model of tumor growth with quiescence  

Microsoft Academic Search

A nonlinear structured cell population model of tumor growth is considered. The model distinguishes between two types of cells\\u000a within the tumor: proliferating and quiescent. Within each class the behavior of individual cells depends on cell size, whereas\\u000a the probabilities of becoming quiescent and returning to the proliferative cycle are in addition controlled by total tumor\\u000a size. The asymptotic behavior

M. Gyllenberg; G. F. Webb

1990-01-01

236

Effect of cadmium level and exposure time on the competition between zooplankton species Moina macrocopa (Cladocera) and Brachionus calyciflorus (Rotifera).  

PubMed

Competition among zooplankton is a natural phenomenon and often cladocerans are competitively superior to rotifers. However, anthropogenic factors including the release of industrial effluents, may influence this interaction. In this study, we evaluated the effect of cadmium (0.05 and 0.1 mg L(-1) as CdCl(2)) on competition between the cladoceran Moina macrocopa and the rotifer Brachionus calyciflorus. Since the release of industrial effluents is generally pulsed, we also exposed the test zooplankton species at different exposure periods (3, 6, 12 and 24 h) to the heavy metal. Regardless of exposure time and the presence of competing species, an increase in concentration of Cd resulted in decreased population growth of M. macrocopa and B. calyciflorus. Regardless of presence of the competing species and Cd concentration, an increase in exposure period resulted in decreased population growth rates of both the zooplankton species. In mixed cultures, in general, M. macrocopa outcompeted B. calyciflorus and completely eliminated it under conditions of high toxicant concentrations and longer exposure time. PMID:16760085

Gama-Flores, Jose Luis; Sarma, S S S; Nandini, S

2006-01-01

237

Recovery of zooplankton assemblages in mountain lakes from the effects of introduced sport fish  

Microsoft Academic Search

Impacts of introduced fish on zooplankton assemblages of lakes may persist for decades following fish removal. We tested this hypothesis by comparing zooplankton assemblages from four categories of lakes located in western Canadian mountain parks including lakes without and with fish that differed in their fish community complex- ity and fish-stocking history. Zooplankton species richness was greatest in lakes with

David B. Donald; Rolf D. Vinebrooke; R. Stewart Anderson; Jim Syrgiannis; Mark D. Graham

2001-01-01

238

Can modeling improve estimation of desert tortoise population densities?  

USGS Publications Warehouse

The federally listed desert tortoise (Gopherus agassizii) is currently monitored using distance sampling to estimate population densities. Distance sampling, as with many other techniques for estimating population density, assumes that it is possible to quantify the proportion of animals available to be counted in any census. Because desert tortoises spend much of their life in burrows, and the proportion of tortoises in burrows at any time can be extremely variable, this assumption is difficult to meet. This proportion of animals available to be counted is used as a correction factor (g0) in distance sampling and has been estimated from daily censuses of small populations of tortoises (6-12 individuals). These censuses are costly and produce imprecise estimates of g0 due to small sample sizes. We used data on tortoise activity from a large (N = 150) experimental population to model activity as a function of the biophysical attributes of the environment, but these models did not improve the precision of estimates from the focal populations. Thus, to evaluate how much of the variance in tortoise activity is apparently not predictable, we assessed whether activity on any particular day can predict activity on subsequent days with essentially identical environmental conditions. Tortoise activity was only weakly correlated on consecutive days, indicating that behavior was not repeatable or consistent among days with similar physical environments. ?? 2007 by the Ecological Society of America.

Nussear, K. E.; Tracy, C. R.

2007-01-01

239

Avoiding Extinction in a Managed Single Species Population Model by means of Anticipative Control  

E-print Network

Avoiding Extinction in a Managed Single Species Population Model by means of Anticipative Control which end in a population collapse and consequent extinction. In a managed environment, it might population models, Allee effect, extinction, anticipative control 1 ANTICIPATORY SYSTEMS Traditionally

Burke, Mark

240

Populations  

NSDL National Science Digital Library

This chapter introduces population as a group of the same kind of organisms in a given space at a given time. The activities in this section will provide students with the opportunity to define population, estimate populations in a community, and count and compare populations within a community. Students will gain the knowledge in describing plant and animal populations living in a community. They will also experiment with plant populations to control growth and development, not to mention discuss the effects of abiotic conditions on a community.

Galle, Janet R.; Warren, Patricia A.

2005-01-01

241

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

242

Ciliate Epibionts Associated with Crustacean Zooplankton in German Lakes: Distribution, Motility, and Bacterivory  

PubMed Central

Ciliate epibionts associated with crustacean zooplankton are widespread in aquatic systems, but their ecological roles are little known. We studied the occurrence of ciliate epibionts on crustacean zooplankton in nine German lakes with different limnological features during the summer of 2011. We also measured the detachment and re-attachment rates of the ciliates, changes in their motility, and the feeding rates of attached vs. detached ciliate epibionts. Epibionts were found in all lakes sampled except an acidic lake with large humic inputs. Epibiont prevalence was as high as 80.96% on the cladoceran Daphnia cucullata, 67.17% on the cladoceran Diaphanosoma brachyurum, and 46.67% on the calanoid copepod Eudiaptomus gracilis. Both cladoceran groups typically had less than 10 epibionts per individual, while the epibiont load on E. gracilis ranged from 1 to >30 epibionts per individual. After the death of the zooplankton host, the peritrich ciliate epibiont Epistylis sp. detached in an exponential fashion with a half-life of 5?min, and 98% detached within 30?min, leaving behind the stalks used for attachment. Immediately after detachment, the ciliates were immotile, but 62% became motile within 60?min. When a new host was present, only 27% reattached after 120?min. The average measured ingestion rate and clearance rate of Epistylis were 11,745 bacteria ciliate?1?h?1 and 24.33??l ciliate?1?h?1, respectively. Despite their high feeding rates, relatively low epibiont abundances were observed in the field, which suggests either diversion of energy to stalk formation, high metabolic loss by the epibionts, or high mortality among the epibiont populations. PMID:22783247

Bickel, Samantha L.; Tang, Kam W.; Grossart, Hans-Peter

2012-01-01

243

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

244

A Hierarchical Model for Estimating Change in American Woodcock Populations  

Microsoft Academic Search

ABSTRACT The Singing-Ground,Survey (SGS) is a primary,source of information,on population,change,for American,woodcock (Scolopax minor). We analyzed the SGS using a hierarchical log-linear model,and compared,the estimates of change,and annual,indices of abundance,to a route regression analysis of SGS data. We also grouped,SGS routes into Bird Conservation,Regions (BCRs) and estimated population change and annual indices using BCRs within states and provinces as strata. Based

John R. Sauer; William A. Link; William L. Kendall; James R. Kelley; Daniel K. Niven

2008-01-01

245

Modelling binary rotating stars by new population synthesis code bonnfires  

NASA Astrophysics Data System (ADS)

bonnfires, a new generation of population synthesis code, can calculate nuclear reaction, various mixing processes and binary interaction in a timely fashion. We use this new population synthesis code to study the interplay between binary mass transfer and rotation. We aim to compare theoretical models with observations, in particular the surface nitrogen abundance and rotational velocity. Preliminary results show binary interactions may explain the formation of nitrogen-rich slow rotators and nitrogen-poor fast rotators, but more work needs to be done to estimate whether the observed frequencies of those stars can be matched.

Lau, H. H. B.; Izzard, R. G.; Schneider, F. R. N.

2013-02-01

246

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

247

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. PMID:15306404

Kruuk, Loeske E B

2004-01-01

248

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

249

Model or meal? Farm animal populations as models for infectious diseases of humans.  

PubMed

In recent decades, theory addressing the processes that underlie the dynamics of infectious diseases has progressed considerably. Unfortunately, the availability of empirical data to evaluate these theories has not grown at the same pace. Although laboratory animals have been widely used as models at the organism level, they have been less appropriate for addressing issues at the population level. However, farm animal populations can provide empirical models to study infectious diseases at the population level. PMID:20040917

Lanzas, Cristina; Ayscue, Patrick; Ivanek, Renata; Gröhn, Yrjö T

2010-02-01

250

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

251

A stochastic population model of mid-continental mallards  

USGS Publications Warehouse

We developed a simulation model that integrates infonnation on factors affecting the population dynamics of mallards in the mid-continental region of the United States. In the model we vary age, body mass, and reproductive and molt status of simulated females. Females use several types of nesting and foraging habitat in 15 geographic areas. Deterministic and stochastic events cause mortality or attribute changes on a daily basis, depending on current attributes, habitat, area, calendar date, wetland conditions, temperature, and various mortality agents. Because the model encompasses the entire year, it can be used to examine cross-seasonal effects. A simulated increase in nest success from 0.14 to 0.17 changed the annual rate of population growth from -6% to -1 %. A simulated 75% reduction in lead poisoning changed the rate from -6% to -3%.

Koford, R.R.; Sauer, J.R.; Johnson, D.H.; Nichols, J.D.; Samuel, M.D.

1992-01-01

252

Stimulus-dependent maximum entropy models of neural population codes  

E-print Network

Neural populations encode information about their stimulus in a collective fashion, by joint activity patterns of spiking and silence. A full account of this mapping from stimulus to neural activity is given by the conditional probability distribution over neural codewords given the sensory input. To be able to infer a model for this distribution from large-scale neural recordings, we introduce a stimulus-dependent maximum entropy (SDME) model---a minimal extension of the canonical linear-nonlinear model of a single neuron, to a pairwise-coupled neural population. The model is able to capture the single-cell response properties as well as the correlations in neural spiking due to shared stimulus and due to effective neuron-to-neuron connections. Here we show that in a population of 100 retinal ganglion cells in the salamander retina responding to temporal white-noise stimuli, dependencies between cells play an important encoding role. As a result, the SDME model gives a more accurate account of single cell re...

Granot-Atedgi, Einat; Segev, Ronen; Schneidman, Elad

2012-01-01

253

Spatial-temporal scales of synchrony in marine zooplankton biomass and abundance patterns: A world-wide comparison  

NASA Astrophysics Data System (ADS)

Large scale synchrony in the fluctuations of abundance or biomass of marine fish populations in regions on opposite sides of an ocean basin or in different oceans have been viewed as externally forced by correlated environmental stochasticity (e.g., common external forcing), most often as atmospheric teleconnections of basin-to-global scale atmospheric forcing, such as the Arctic Oscillation, North Atlantic Oscillation or the Pacific Decadal Oscillation. Specific causal mechanisms have been difficult to unequivocally discover, but possible mechanisms include influences on habitat temperatures, productivity operating through bottom-up (trophodynamic) mechanisms or direct climate influence on the fish populations (top-down mechanisms). For small pelagic fishes (sardines and anchovies) in widely separated large marine ecosystems that lack obvious ocean interconnectivity, it has been argued that the teleconnections may be atmospheric, acting on the fishes directly and propagating to the ecosystem from the middle out (wasp-waist species). Zooplankton biomass or abundance time series data from >100 sites world-wide are used to examine the spatial scales of coherent temporal synchrony. If spatially correlated environmental factors (like climate) are important for creating synchrony in fish populations via bottom-up effects (trophic interactions involving fish prey, e.g., zooplankton), then we would expect to observe synchrony in fluctuations of zooplankton biomass/numbers at spatial scales similar to those found for fish species. Zooplankton biomass/abundance have 50% spatial decorrelation scales of ca. 700-1400 km and scales of significant coherence that extend to separation distances of ca. 3000 km. These are also the spatial scales of environmental (sea surface temperature) synchrony from our global analysis. These scales are slightly greater than the 50% decorrelation scales of ca. 150-700 km for recruitment synchrony in Atlantic marine fish and survival and recruitment synchrony of Northeast Pacific salmonids (150-1000 km depending on species). However, the spatial scales of synchrony of annual zooplankton biomass anomalies in the Humboldt Current, California Current and Kuroshio ecosystems of the Pacific are much too small (ca. 2000 km) to be directly causal of the basin-scale (7000-15,000 km) synchrony exhibited by sardine and/or anchovy populations in those ecosystems.

Batchelder, Harold P.; Mackas, David L.; O'Brien, Todd D.

2012-05-01

254

Resource Requirements of the Pacific Leatherback Turtle Population  

PubMed Central

The Pacific population of leatherback sea turtles (Dermochelys coriacea) has drastically declined in the last 25 years. This decline has been linked to incidental capture by fisheries, egg and meat harvesting, and recently, to climate variability and resource limitation. Here we couple growth rates with feeding experiments and food intake functions to estimate daily energy requirements of leatherbacks throughout their development. We then estimate mortality rates from available data, enabling us to raise food intake (energy requirements) of the individual to the population level. We place energy requirements in context of available resources (i.e., gelatinous zooplankton abundance). Estimated consumption rates suggest that a single leatherback will eat upward of 1000 metric tonnes (t) of jellyfish in its lifetime (range 924–1112) with the Pacific population consuming 2.1×106 t of jellyfish annually (range 1.0–3.7×106) equivalent to 4.2×108 megajoules (MJ) (range 2.0–7.4×108). Model estimates suggest 2–7 yr-old juveniles comprise the majority of the Pacific leatherback population biomass and account for most of the jellyfish consumption (1.1×106 t of jellyfish or 2.2×108 MJ per year). Leatherbacks are large gelatinous zooplanktivores with consumption to biomass ratios of 96 (up to 192 if feeding strictly on low energy density Cnidarians); they, therefore, have a large capacity to impact gelatinous zooplankton landscapes. Understanding the leatherback's needs for gelatinous zooplankton, versus the availability of these resources, can help us better assess population trends and the influence of climate induced resource limitations to reproductive output. PMID:23071518

Jones, T. Todd; Bostrom, Brian L.; Hastings, Mervin D.; Van Houtan, Kyle S.; Pauly, Daniel; Jones, David R.

2012-01-01

255

Resource requirements of the Pacific leatherback turtle population.  

PubMed

The Pacific population of leatherback sea turtles (Dermochelys coriacea) has drastically declined in the last 25 years. This decline has been linked to incidental capture by fisheries, egg and meat harvesting, and recently, to climate variability and resource limitation. Here we couple growth rates with feeding experiments and food intake functions to estimate daily energy requirements of leatherbacks throughout their development. We then estimate mortality rates from available data, enabling us to raise food intake (energy requirements) of the individual to the population level. We place energy requirements in context of available resources (i.e., gelatinous zooplankton abundance). Estimated consumption rates suggest that a single leatherback will eat upward of 1000 metric tonnes (t) of jellyfish in its lifetime (range 924-1112) with the Pacific population consuming 2.1×10(6) t of jellyfish annually (range 1.0-3.7×10(6)) equivalent to 4.2×10(8) megajoules (MJ) (range 2.0-7.4×10(8)). Model estimates suggest 2-7 yr-old juveniles comprise the majority of the Pacific leatherback population biomass and account for most of the jellyfish consumption (1.1×10(6) t of jellyfish or 2.2×10(8) MJ per year). Leatherbacks are large gelatinous zooplanktivores with consumption to biomass ratios of 96 (up to 192 if feeding strictly on low energy density Cnidarians); they, therefore, have a large capacity to impact gelatinous zooplankton landscapes. Understanding the leatherback's needs for gelatinous zooplankton, versus the availability of these resources, can help us better assess population trends and the influence of climate induced resource limitations to reproductive output. PMID:23071518

Jones, T Todd; Bostrom, Brian L; Hastings, Mervin D; Van Houtan, Kyle S; Pauly, Daniel; Jones, David R

2012-01-01

256

A Bayesian approach to identifying and compensating for model misspecification in population models.  

PubMed

State-space estimation methods are increasingly used in ecology to estimate productivity and abundance of natural populations while accounting for variability in both population dynamics and measurement processes. However, functional forms for population dynamics and density dependence often will not match the true biological process, and this may degrade the performance of state-space methods. We therefore developed a Bayesian semiparametric state-space model, which uses a Gaussian process (GP) to approximate the population growth function. This offers two benefits for population modeling. First, it allows data to update a specified "prior" on the population growth function, while reverting to this prior when data are uninformative. Second, it allows variability in population dynamics to be decomposed into random errors around the population growth function ("process error") and errors due to the mismatch between the specified prior and estimated growth function ("model error"). We used simulation modeling to illustrate the utility of GP methods in state-space population dynamics models. Results confirmed that the GP model performs similarly to a conventional state-space model when either (1) the prior matches the true process or (2) data are relatively uninformative. However, GP methods improve estimates of the population growth function when the function is misspecified. Results also demonstrated that the estimated magnitude of "model error" can be used to distinguish cases of model misspecification. We conclude with a discussion of the prospects for GP methods in other state-space models, including age and length-structured, meta-analytic, and individual-movement models. PMID:24669727

Thorson, James T; Ono, Kotaro; Munch, Stephan B

2014-02-01

257

Influence of mesoscale anticyclonic eddies on zooplankton distribution south of the western Aleutian Islands during summer  

NASA Astrophysics Data System (ADS)

Mesoscale anticyclonic eddies have been observed south of the Aleutian Islands located between the Bering Sea and the subarctic Pacific. Eddies farther east, in the Gulf of Alaska, are known to transport coastal water and coastal zooplankton to offshore open ocean. The impacts of mesoscale anticyclonic eddies formed south of the western Aleutian Islands (Aleutian eddies) on the zooplankton community are not fully understood. In the present study, we describe zooplankton population structures within an Aleutian eddy and outside the eddy during July 2010. Our field study was conducted at seven stations along 51°15?N from 171°21?E to 174°38?E (western line) and at four stations along 50°40?N from 176°24?E to 178°44?E (eastern line) on 7-8 July 2010. At each station, environmental data (temperature, salinity and fluorescence were measured by CTD/XCTD. Zooplankton samples were collected by vertical tow of 150 m depth to the surface using 100 ?m mesh size plankton net. Based on the sea level anomaly (SLA), the western line crossed an anticyclonic eddy but the eastern line did not cross the eddy (Fig. 1). This Aleutian eddy was formed south of Attu Island (52°54?N, 172°54?E) in mid-February 2010, and it moved southeastward in the next five months. The SLA near the eddy center, representing the strength of the eddy, continuously increased, and the area oscillated at one to two month periods overlain on a general increase from ~7,000 to ~18,000 km2. Large oceanic copepods, Neocalanus cristatus, Eucalanus bungii and Metridia pacifica were more abundant inside the eddy than the outside. Inside the eddy, the life stage distribution of N. cristatus was advanced than that outside, and Neocalanus spp. had accumulated more lipids. These conditions probably reflect the greater primary production in the eddy, production enhanced by nutrients advected into the eddy. Since the Aleutian eddy was formed in offshore waters and/or eddy-eddy interaction occurred after its formation, it contained mostly oceanic copepods. The sufficient food condition in the eddy presumably induced higher growth and survival rates of these oceanic copepods, resulting in the greater abundance, advanced development stages and greater lipid accumulation. Fig. 1. Sea level anomaly along the sampling lines on 7 July 2010 south of the western Aleutian Islands.

Saito, R.; Yamaguchi, A.; Yasuda, I.; Ueno, H.; Ishiyama, H.; Imai, I.

2013-12-01

258

Moving across the border: modeling migratory bat populations  

USGS Publications Warehouse

The migration of animals across long distances and between multiple habitats presents a major challenge for conservation. For the migratory Mexican free-tailed bat (Tadarida brasiliensis mexicana), these challenges include identifying and protecting migratory routes and critical roosts in two countries, the United States and Mexico. Knowledge and conservation of bat migratory routes is critical in the face of increasing threats from climate change and wind turbines that might decrease migratory survival. We employ a new modeling approach for bat migration, network modeling, to simulate migratory routes between winter habitat in southern Mexico and summer breeding habitat in northern Mexico and the southwestern United States. We use the model to identify key migratory routes and the roosts of greatest conservation value to the overall population. We measure roost importance by the degree to which the overall bat population declined when the roost was removed from the model. The major migratory routes—those with the greatest number of migrants—were between winter habitat in southern Mexico and summer breeding roosts in Texas and the northern Mexican states of Sonora and Nuevo Leon. The summer breeding roosts in Texas, Sonora, and Nuevo Leon were the most important for maintaining population numbers and network structure – these are also the largest roosts. This modeling approach contributes to conservation efforts by identifying the most influential areas for bat populations, and can be used as a tool to improve our understanding of bat migration for other species. We anticipate this approach will help direct coordination of habitat protection across borders.

Ruscena, Wiederholt; Lopez-Hoffman, Laura; Cline, Jon; Medellin, Rodrigo; Cryan, Paul; Russell, Amy; McCracken, Gary; Diffendorfer, Jay; Semmens, Darius J.

2013-01-01

259

Bayesian Modeling of Haplotype Effects in Multiparent Populations  

PubMed Central

A general Bayesian model, Diploffect, is described for estimating the effects of founder haplotypes at quantitative trait loci (QTL) detected in multiparental genetic populations; such populations include the Collaborative Cross (CC), Heterogeneous Socks (HS), and many others for which local genetic variation is well described by an underlying, usually probabilistically inferred, haplotype mosaic. Our aim is to provide a framework for coherent estimation of haplotype and diplotype (haplotype pair) effects that takes into account the following: uncertainty in haplotype composition for each individual; uncertainty arising from small sample sizes and infrequently observed haplotype combinations; possible effects of dominance (for noninbred subjects); genetic background; and that provides a means to incorporate data that may be incomplete or has a hierarchical structure. Using the results of a probabilistic haplotype reconstruction as prior information, we obtain posterior distributions at the QTL for both haplotype effects and haplotype composition. Two alternative computational approaches are supplied: a Markov chain Monte Carlo sampler and a procedure based on importance sampling of integrated nested Laplace approximations. Using simulations of QTL in the incipient CC (pre-CC) and Northport HS populations, we compare the accuracy of Diploffect, approximations to it, and more commonly used approaches based on Haley–Knott regression, describing trade-offs between these methods. We also estimate effects for three QTL previously identified in those populations, obtaining posterior intervals that describe how the phenotype might be affected by diplotype substitutions at the modeled locus. PMID:25236455

Zhang, Zhaojun; Wang, Wei; Valdar, William

2014-01-01

260

Bayesian modeling of haplotype effects in multiparent populations.  

PubMed

A general Bayesian model, Diploffect, is described for estimating the effects of founder haplotypes at quantitative trait loci (QTL) detected in multiparental genetic populations; such populations include the Collaborative Cross (CC), Heterogeneous Socks (HS), and many others for which local genetic variation is well described by an underlying, usually probabilistically inferred, haplotype mosaic. Our aim is to provide a framework for coherent estimation of haplotype and diplotype (haplotype pair) effects that takes into account the following: uncertainty in haplotype composition for each individual; uncertainty arising from small sample sizes and infrequently observed haplotype combinations; possible effects of dominance (for noninbred subjects); genetic background; and that provides a means to incorporate data that may be incomplete or has a hierarchical structure. Using the results of a probabilistic haplotype reconstruction as prior information, we obtain posterior distributions at the QTL for both haplotype effects and haplotype composition. Two alternative computational approaches are supplied: a Markov chain Monte Carlo sampler and a procedure based on importance sampling of integrated nested Laplace approximations. Using simulations of QTL in the incipient CC (pre-CC) and Northport HS populations, we compare the accuracy of Diploffect, approximations to it, and more commonly used approaches based on Haley-Knott regression, describing trade-offs between these methods. We also estimate effects for three QTL previously identified in those populations, obtaining posterior intervals that describe how the phenotype might be affected by diplotype substitutions at the modeled locus. PMID:25236455

Zhang, Zhaojun; Wang, Wei; Valdar, William

2014-09-01

261

A stage-based model of manatee population dynamics  

USGS Publications Warehouse

A stage-structured population model for the Florida manatee (Trichechus manatus latirostris) was developed that explicitly incorporates uncertainty in parameter estimates. The growth rates calculated with this model reflect the status of the regional populations over the most recent 10-yr period. The Northwest and Upper St. Johns River regions have growth rates (8) of 1.037 (95% interval, 1.016?1.056) and 1.062 (1.037?1.081), respectively. The Southwest region has a growth rate of 0.989 (0.946?1.024), suggesting this population has been declining at about 1.1% per year. The estimated growth rate in the Atlantic region is 1.010 (0.988?1.029), but there is some uncertainty about whether adult survival rates have been constant over the last 10 yr; using the mean survival rates from the most recent 5-yr period, the estimated growth rate in this region is 0.970 (0.938?0.998). Elasticity analysis indicates that the most effective management actions should seek to increase adult survival rates. Decomposition of the uncertainty in the growth rates indicates that uncertainty about population status can best be reduced through increased monitoring of adult survival rate.

Runge, M.C.; Langtimm, C.A.; Kendall, W.L.

2004-01-01

262

Zooplankton and Micronekton Studies at Bermuda: An Historical Perspective  

Microsoft Academic Search

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

L. P. Madin; D. K. Steinberg

2001-01-01

263

Recovery of acid damaged zooplankton communities: measurement, extent, and limiting  

E-print Network

of lakes in eastern North America and Europe. To measure the degree and extent of biological recoveryRecovery of acid damaged zooplankton communities: measurement, extent, and limiting factors Derek K) reference-lakes; and (3) temporal. Within these study designs, the most commonly used metrics include

Arnott, Shelley

264

Zooplankton nutrition: recent progress and a reality check  

Microsoft Academic Search

Evidence suggests that marine and freshwater zooplankton generally experience food levels above subsistence values in terms of carbon. However, the quality of this food may be poor due to an insufficiency of other essential nutrients. In this review, we examine recent progress in three main areas of food quality research: (1) elemental (especially P) limitation, (2) digestion resistance, and (3)

Robert W. Sterner; Kimberly L. Schulz

1998-01-01

265

Response of zooplankton, benthos, and fish to acidification: An overview  

Microsoft Academic Search

This paper presents an overview of the response to acidification of aquatic fauna with special emphasis on Zooplankton, benthos, and fishes. Changes in behavior, body chemistry, reproduction, and species diversity are presented based on laboratory experiments and field studies in both Europe and North America. Differences in species sensitivity are discussed as they relate, not only to acidification but also

Magda Havas; Bjørn Olav Rosseland

1995-01-01

266

Accumulation of heavy metals by freshwater zooplankton - a toxicological study  

Microsoft Academic Search

So far many toxicologic studies are made earlier; we studied the acute toxicity estimation related to some specific identified freshwater zooplanktons of Paradip (Harbour City) area of Jagatsingpur District, Orissa, India which is situated on the bank of Mahanadi River. The study area is prone to heavy metal pollution because mineral based industries in relation to zinc, lead and cadmium

S. K. Baliarsingh; S. Srichandan; T. Padmavati; Subrat Naik; K. C. Sahu

2010-01-01

267

Zooplankton and Karenia brevis in the Gulf of Mexico  

NASA Astrophysics Data System (ADS)

Blooms of the toxic dinoflagellate Karenia brevis are common in the Gulf of Mexico, yet no in situ studies of zooplankton and K. brevis have been conducted there. Zooplankton abundance and taxonomic composition at non-bloom and K. brevis bloom stations within the Ecology of Harmful Algal Blooms (ECOHAB) study area were compared. At non-bloom stations, the most abundant species of zooplankton were Parvocalanus crassirostris, Oithona colcarva, and Paracalanus quasimodo at the 5-m isobath and P. quasimodo, O. colcarva, and Oikopleura dioica at the 25-m isobath. There was considerable overlap in dominance of zooplankton species between the 5 and 25-m isobaths, with nine species contributing to 90% of abundance at both isobaths. At stations within K. brevis blooms however, Acartia tonsa, Centropages velificatus, Temora turbinata, Evadne tergestina, O. colcarva, O. dioica, and P. crassirostris were dominant. Variations in abundance between non-bloom and bloom assemblages were evident, including the reduction in abundance of three key species within K. brevis blooms.

Lester, Kristen M.; Heil, Cynthia A.; Neely, Merry B.; Spence, Danylle N.; Murasko, Susan; Hopkins, Thomas L.; Sutton, Tracey T.; Burghart, Scott E.; Bohrer, Richard N.; Remsen, Andrew W.; Vargo, Gabriel A.; Walsh, John J.

2008-01-01

268

Correlates of Zooplankton Beta Diversity in Tropical Lake Systems  

PubMed Central

The changes in species composition between habitat patches (beta diversity) are likely related to a number of factors, including environmental heterogeneity, connectivity, disturbance and productivity. Here, we used data from aquatic environments in five Brazilian regions over two years and two seasons (rainy and dry seasons or high and low water level periods in floodplain lakes) in each year to test hypotheses underlying zooplankton beta diversity variation. The regions present different levels of hydrological connectivity, where three regions present lakes that are permanent and connected with the main river, while the water bodies of the other two regions consist of permanent lakes and temporary ponds, with no hydrological connections between them. We tested for relationships between zooplankton beta diversity and environmental heterogeneity, spatial extent, hydrological connectivity, seasonality, disturbance and productivity. Negative relationships were detected between zooplankton beta diversity and both hydrological connectivity and disturbance (periodic dry-outs). Hydrological connectivity is likely to affect beta diversity by facilitating dispersal between habitats. In addition, the harsh environmental filter imposed by disturbance selected for only a small portion of the species from the regional pool that were able to cope with periodic dry-outs (e.g., those with a high production of resting eggs). In summary, this study suggests that faunal exchange and disturbance play important roles in structuring local zooplankton communities. PMID:25330034

Lopes, Paloma M.; Bini, Luis M.; Declerck, Steven A. J.; Farjalla, Vinicius F.; Vieira, Ludgero C. G.; Bonecker, Claudia C.; Lansac-Toha, Fabio A.; Esteves, Francisco A.; Bozelli, Reinaldo L.

2014-01-01

269

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

270

Induced pigmentation in zooplankton: a trade-off between threats from predation and ultraviolet radiation.  

PubMed Central

Ultraviolet (UV) radiation is harmful to all life, and the ongoing depletion of the ozone layer is likely to affect interactions among both terrestrial and aquatic organisms. Some organisms have evolved adaptations to reduce radiation damage, such as the various types of protective pigmentation of freshwater zooplankton. However, strong pigmentation also increases vulnerability to visually hunting predators. Hence, where both UV radiation and predation are intense, zooplankton may be sandwiched between conflicting selective pressures: to be pigmented and to be transparent at the same time. Here, I show that the level of pigmentation in copepods is up to ten times higher in lakes without predatory fishes than where fishes are present. Moreover, animals from the same population exposed to either UV light or predator scent showed a 10% difference in pigmentation after only four days, suggesting that pigmentation is an inducible trait. Hence, individual copepods are not passive victims of selective predation or radiation damage, but adjust the level of pigmentation according to the prevailing threat. The ability to adjust pigmentation level rapidly may be especially useful in situations where risk assessment is difficult due to strong seasonal and spatial variation in risk variables, such as in Arctic regions. With progressive thinning of the ozone layer, the ability of some but not other organisms to adjust protection against UV radiation may lead to counter-intuitive, large-scale alterations in freshwater food webs. PMID:11413651

Hansson, L A

2000-01-01

271

Development of zooplankton culture subsystem for a closed ecological recirculating aquaculture system (CERAS)  

NASA Astrophysics Data System (ADS)

Ten parthenogenetic females of Moina macrocopa were placed in small cells with different flow conditions. The cells were opened after three-days of cultivation, and the water fleas in each cell were counted. It appeared that M. macrocopa were cultured effectively in a relatively slow current, 10 cm/min., but the population growth was not significantly influenced by the difference in flow direction. Subsequent, filtration efficiencies of filters with various pore sizes were compared. Four available porous hollow-fiber membrane modules, ACP-1010, AHP-1010, PSP-103, and PMP-102 (Asahi-Kasei Corp.), were tested. The module with the larger pore size initially filtered a greater amount of water but clogged up sooner. ACP-1010, which has the smallest pores, was considered to be suitable to filter condensed algal water due to its durability and stable filtration. An improved zooplankton culture device (IZCD) was designed and constructed based on these examinations. IZCD is a 13.2L airtight device characterized by a short and thick rearing tank and alternate filtration with paired fine hollow-fiber membrane modules. It must be tested and revised to be used in research into the optimal conditions for a zooplankton culture in a closed environment.

Omori, Katsunori; Oguchi, Mitsuo; Takeuchi, Toshio

2006-01-01

272

Induced pigmentation in zooplankton: a trade-off between threats from predation and ultraviolet radiation.  

PubMed

Ultraviolet (UV) radiation is harmful to all life, and the ongoing depletion of the ozone layer is likely to affect interactions among both terrestrial and aquatic organisms. Some organisms have evolved adaptations to reduce radiation damage, such as the various types of protective pigmentation of freshwater zooplankton. However, strong pigmentation also increases vulnerability to visually hunting predators. Hence, where both UV radiation and predation are intense, zooplankton may be sandwiched between conflicting selective pressures: to be pigmented and to be transparent at the same time. Here, I show that the level of pigmentation in copepods is up to ten times higher in lakes without predatory fishes than where fishes are present. Moreover, animals from the same population exposed to either UV light or predator scent showed a 10% difference in pigmentation after only four days, suggesting that pigmentation is an inducible trait. Hence, individual copepods are not passive victims of selective predation or radiation damage, but adjust the level of pigmentation according to the prevailing threat. The ability to adjust pigmentation level rapidly may be especially useful in situations where risk assessment is difficult due to strong seasonal and spatial variation in risk variables, such as in Arctic regions. With progressive thinning of the ozone layer, the ability of some but not other organisms to adjust protection against UV radiation may lead to counter-intuitive, large-scale alterations in freshwater food webs. PMID:11413651

Hansson, L A

2000-11-22

273

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

274

Planetary Population Synthesis: Comparison of Updated Model Results and Observations.  

NASA Astrophysics Data System (ADS)

The field of extrasolar planet research is currently undergoing an fast, impressive gain of observational knowledge on the architectures and characteristics of planetary systems around other stars. This is thanks to the results of both observations from the ground, as well as observations from space. Some of these detections, in particular from the KEPLER satellite and from high precision radial velocity searches have recently challenged existing planet formation models. This has triggered intense theoretical work in order to understand the origins of the differences between observation and theory. In my talk I will present updated core accretion formation models which were used to conduct population synthesis simulations. Besides many other improvements contain these models a much more detailed description of planetary migration, allow for the concurrent formation of many fully interacting embryos in one disk, and include now also the subsequent evolution of the planets after formation on Gyr timescales. The latter improvement gives us all major quantities characterizing a planet, like its mass, composition, radius, luminosity and effective temperature. It also means that the results can be directly compared not only to the observed mass - distance diagram, but also to the observed radius distribution and the luminosity measured by direct imaging. Thanks to such improvement of the models, allowing new physical phenomena like the capture into mean motion resonances, or the existence of convergence zones for type I migration, it is found that the properties of the population of synthetic close-in, low mass planets, and of the corresponding observed population are much more similar than in earlier models, even though that some differences still exist. An example is that the models predict an bimodal distribution of planetary radii, which is not observed. I will discuss the reasons for both the better agreement, as well as the remaining differences.

Mordasini, Christoph

2011-09-01

275

Short-term effects of drawing water for connectivity of rivers and lakes on zooplankton community structure.  

PubMed

During 28-29, September 2005, water was drawn from Hanjiang River and Houguan Lake to the Yangzi River via Sanjiao Lake and Nantaizi Lake in Wuhan in order to provide favorable conditions for ecosystem restoration. To evaluate the feasibility and validity of drawing water as a means of ecosystem restoration, zooplankton populations were studied 3 times (before, immediately after finishing and a month after drawing water) at seven locations from 27 Sept. 2005 to 2 Nov. 2005. Water quality in the lakes was mostly improved and zooplankton species richness decreased as soon as drawing water had finished but increased a month after drawing water. Zooplankton density and biomass was reduced in the lakes by drawing water but was increased at the entrance to Sanjiao Lake because of landform geometry change. Before drawing water, most species in Sanjiao Lake e.g., Brachionus sp. and Keratella sp. were tolerant of contamination. After drawing water oligotrophic-prone species such as Lecane ludwigii and Gastropus stylifer emerged. We conclude that drawing water could be important for improving water quality and favour ecosystem restoration. Dilution of nutrient concentrations may be an important role in the effect. PMID:18575125

Wu, Zhenbin; Liu, Aifen; Zhang, Shiyang; Cheng, Shuiping; Wu, Xiaohui

2008-01-01

276

Multimodel robust observer for an uncertain fish population model.  

PubMed

In this paper, a new method is proposed to design an observer for a nonlinear and uncertain system describing a continuous stage structured model of a harvested fish population. The aim is to get an estimation of the biomass of fishes by stage class. In the studied model the fishing effort is considered as a control term, the stage classes as states and the quantity of captured fish as a measured output. A Takagi-Sugeno multimodel first represents the uncertain non-linear model. Next, we develop a technique for designing a multimodel observer corresponding to this system, which attenuates the effect of modelling uncertainties and measurement noise on the state estimation. The design conditions are given in linear matrix inequalities (LMIs) terms that can be solved efficiently using existing numerical tools. The validity of the proposed method is illustrated by the simulation results. PMID:25057778

Ait Kaddour, Achraf; Benjelloun, Khalid; Elalami, Noureddine; El Mazoudi, El Houssine

2014-10-01

277

Modelling lipid competition dynamics in heterogeneous protocell populations.  

PubMed

Recent experimental work in the field of synthetic protocell biology has shown that prebiotic vesicles are able to 'steal' lipids from each other. This phenomenon is driven purely by asymmetries in the physical state or composition of the vesicle membranes, and, when lipid resource is limited, translates directly into competition amongst the vesicles. Such a scenario is interesting from an origins of life perspective because a rudimentary form of cell-level selection emerges. To sharpen intuition about possible mechanisms underlying this behaviour, experimental work must be complemented with theoretical modelling. The aim of this paper is to provide a coarse-grain mathematical model of protocell lipid competition. Our model is capable of reproducing, often quantitatively, results from core experimental papers that reported distinct types vesicle competition. Additionally, we make some predictions untested in the lab, and develop a general numerical method for quickly solving the equilibrium point of a model vesicle population. PMID:25024020

Shirt-Ediss, Ben; Ruiz-Mirazo, Kepa; Mavelli, Fabio; Solé, Ricard V

2014-01-01

278

Richards-like two species population dynamics model.  

PubMed

The two-species population dynamics model is the simplest paradigm of inter- and intra-species interaction. Here, we present a generalized Lotka-Volterra model with intraspecific competition, which retrieves as particular cases, some well-known models. The generalization parameter is related to the species habitat dimensionality and their interaction range. Contrary to standard models, the species coupling parameters are general, not restricted to non-negative values. Therefore, they may represent different ecological regimes, which are derived from the asymptotic solution stability analysis and are represented in a phase diagram. In this diagram, we have identified a forbidden region in the mutualism regime, and a survival/extinction transition with dependence on initial conditions for the competition regime. Also, we shed light on two types of predation and competition: weak, if there are species coexistence, or strong, if at least one species is extinguished. PMID:25112794

Ribeiro, Fabiano; Cabella, Brenno Caetano Troca; Martinez, Alexandre Souto

2014-12-01

279

Constrained hidden Markov models for population-based haplotyping  

PubMed Central

Background Haplotype Reconstruction is the problem of resolving the hidden phase information in genotype data obtained from laboratory measurements. Solving this problem is an important intermediate step in gene association studies, which seek to uncover the genetic basis of complex diseases. We propose a novel approach for haplotype reconstruction based on constrained hidden Markov models. Models are constructed by incrementally refining and regularizing the structure of a simple generative model for genotype data under Hardy-Weinberg equilibrium. Results The proposed method is evaluated on real-world and simulated population data. Results show that it is competitive with other recently proposed methods in terms of reconstruction accuracy, while offering a particularly good trade-off between computational costs and quality of results for large datasets. Conclusion Relatively simple probabilistic approaches for haplotype reconstruction based on structured hidden Markov models are competitive with more complex, well-established techniques in this field. PMID:17493258

Landwehr, Niels; Mielikainen, Taneli; Eronen, Lauri; Toivonen, Hannu; Mannila, Heikki

2007-01-01

280

CALIBRATING STELLAR POPULATION MODELS WITH MAGELLANIC CLOUD STAR CLUSTERS  

SciTech Connect

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 {approx}0.6 to {approx}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 {approx}0.6 Gyr, with a correspondingly very red integrated color, at variance with the data; Bruzual and 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 {approx}0.6 and 1 Gyr is dependent on the adopted age scale for the clusters and may have important implications for stellar evolution.

Noeel, N. E. D.; Carollo, C. M. [ETH Zuerich, Institute for Astronomy, Wolfgang-Pauli-Strasse 27, Building HIT, Floor J, CH-8093 Zurich (Switzerland); Greggio, L.; Renzini, A. [INAF-Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, I-35122 Padova (Italy); Maraston, C. [University of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth PO1 3FX (United Kingdom)

2013-07-20

281

Fast algorithm for population-based protein structural model analysis.  

PubMed

De novo protein structure prediction often generates a large population of candidates (models), and then selects near-native models through clustering. Existing structural model clustering methods are time consuming due to pairwise distance calculation between models. In this paper, we present a novel method for fast model clustering without losing the clustering accuracy. Instead of the commonly used pairwise root mean square deviation and TM-score values, we propose two new distance measures, Dscore1 and Dscore2, based on the comparison of the protein distance matrices for describing the difference and the similarity among models, respectively. The analysis indicates that both the correlation between Dscore1 and root mean square deviation and the correlation between Dscore2 and TM-score are high. Compared to the existing methods with calculation time quadratic to the number of models, our Dscore1-based clustering achieves a linearly time complexity while obtaining almost the same accuracy for near-native model selection. By using Dscore2 to select representatives of clusters, we can further improve the quality of the representatives with little increase in computing time. In addition, for large size (~500 k) models, we can give a fast data visualization based on the Dscore distribution in seconds to minutes. Our method has been implemented in a package named MUFOLD-CL, available at http://mufold.org/clustering.php. PMID:23184517

Zhang, Jingfen; Xu, Dong

2013-01-01

282

Pathogen population dynamics in agricultural landscapes: The Ddal modelling framework.  

PubMed

Modelling processes that occur at the landscape scale is gaining more and more attention from theoretical ecologists to agricultural managers. Most of the approaches found in the literature lack applicability for managers or, on the opposite, lack a sound theoretical basis. Based on the metapopulation concept, we propose here a modelling approach for landscape epidemiology that takes advantage of theoretical results developed in the metapopulation context while considering realistic landscapes structures. A landscape simulator makes it possible to represent both the field pattern and the spatial distribution of crops. The pathogen population dynamics are then described through a matrix population model both stage- and space-structured. In addition to a classical invasion analysis we present a stochastic simulation experiment and provide a complete framework for performing a sensitivity analysis integrating the landscape as an input factor. We illustrate our approach using an example to evaluate whether the agricultural landscape composition and structure may prevent and mitigate the development of an epidemic. Although designed for a fungal foliar disease, our modelling approach is easily adaptable to other organisms. PMID:24480053

Papaïx, Julien; Adamczyk-Chauvat, Katarzyna; Bouvier, Annie; Kiêu, Kiên; Touzeau, Suzanne; Lannou, Christian; Monod, Hervé

2014-10-01

283

Modelling multi-pulse population dynamics from ultrafast spectroscopy.  

PubMed

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. PMID:21445294

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

2011-01-01

284

Towards a continuous population model for natural language vowel shift.  

PubMed

The Great English Vowel Shift of 16th-19th centuries and the current Northern Cities Vowel Shift are two examples of collective language processes characterized by regular phonetic changes, that is, gradual changes in vowel pronunciation over time. Here we develop a structured population approach to modeling such regular changes in the vowel systems of natural languages, taking into account learning patterns and effects such as social trends. We treat vowel pronunciation as a continuous variable in vowel space and allow for a continuous dependence of vowel pronunciation in time and age of the speaker. The theory of mixtures with continuous diversity provides a framework for the model, which extends the McKendrick-von Foerster equation to populations with age and phonetic structures. We develop the general balance equations for such populations and propose explicit expressions for the factors that impact the evolution of the vowel pronunciation distribution. For illustration, we present two examples of numerical simulations. In the first one we study a stationary solution corresponding to a state of phonetic equilibrium, in which speakers of all ages share a similar phonetic profile. We characterize the variance of the phonetic distribution in terms of a parameter measuring a ratio of phonetic attraction to dispersion. In the second example we show how vowel shift occurs upon starting with an initial condition consisting of a majority pronunciation that is affected by an immigrant minority with a different vowel pronunciation distribution. The approach developed here for vowel systems may be applied also to other learning situations and other time-dependent processes of cognition in self-interacting populations, like opinions or perceptions. PMID:23624180

Shipman, Patrick D; Faria, Sérgio H; Strickland, Christopher

2013-09-01

285

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. PMID:24124552

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

2013-01-01

286

Ecological Modelling 126 (2000) 7377 Leslie model for predatory gall-midge population  

E-print Network

Ecological Modelling 126 (2000) 73­77 Leslie model for predatory gall-midge population Vlastimil´ Budejo6ice, Czech Republic Accepted 16 August 1999 Abstract A Leslie matrix model for predatory gall-midge is used in biological control. We compare the two common parametrizations of Leslie matrix., i.e. the flow

Krivan, Vlastimil

287

A predictive model for gypsy moth population dynamics with model validation  

Microsoft Academic Search

A simple model for gypsy moth, Lymantria dispar (Lepidoptera: Lymantriidae), population dynamics is presented. Comparison with data from the Melrose Highlands study shows the model to exhibit the same qualitative and quantitative behavior as the data. Predictions are made about future outbreaks using only a portion of the field data to fit the model parameters. Comparison of these predictions with

J. W Wilder

1999-01-01

288

State-space models for the dynamics of wild animal populations  

Microsoft Academic Search

We develop a unified framework for jointly defining population dynamics models and measurements taken on a population. The framework is a state-space model where the population processes are modelled by the state process and measurements are modelled by the observation process. In many cases, the expected value for the state process can be represented as a generalisation of the standard

S. T. Buckland; K. B. Newmanb; L. Thomas; N. B. Koesters

2004-01-01

289

A Diffusion Model in Population Genetics with Mutation and Dynamic Fitness  

E-print Network

A Diffusion Model in Population Genetics with Mutation and Dynamic Fitness Mike O'Leary Department Model in Genetics WCNA 2008 2 / 38 #12;The Discrete Model Consider a single haploid panmictic population in Genetics WCNA 2008 3 / 38 #12;The Discrete Model Let the fraction of the population with allele Ai at locus

O'Leary, Michael

290

Modelling Lipid Competition Dynamics in Heterogeneous Protocell Populations  

E-print Network

In addressing the origins of Darwinian evolution, recent experimental work has been focussed on the discovery of simple physical effects which would provide a relevant selective advantage to protocells competing with each other for a limited supply of lipid. In particular, data coming from Szostak's lab suggest that the transition from simple prebiotically plausible lipid membranes to more complex and heterogeneous ones, closer to real biomembranes, may have been driven by changes in the fluidity of the membrane and its affinity for the available amphiphilic compound, which in turn would involve changes in vesicle growth dynamics. Earlier work from the same group reported osmotically-driven competition effects, whereby swelled vesicles grow at the expense of isotonic ones. In this paper, we try to expand on these experimental studies by providing a simple mathematical model of a population of competing vesicles, studied at the level of lipid kinetics. In silico simulations of the model are able to reproduce qualitatively and often quantitatively the experimentally reported competition effects in both scenarios. We also develop a method for numerically solving the equilibrium of a population of competing model vesicles, which is quite general and applicable to different vesicle kinetics schemes.

Ben Shirt-Ediss; Kepa Ruiz-Mirazo; Fabio Mavelli; Ricard V. Solé

2014-01-30

291

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

292

Modeling the impact of the indigenous microbial population on the maximum population density of Salmonella on alfalfa.  

PubMed

Within a microbial risk assessment framework, modeling the maximum population density (MPD) of a pathogenic microorganism is important but often not considered. This paper describes a model predicting the MPD of Salmonella on alfalfa as a function of the initial contamination level, the total count of the indigenous microbial population, the maximum pathogen growth rate and the maximum population density of the indigenous microbial population. The model is parameterized by experimental data describing growth of Salmonella on sprouting alfalfa seeds at inoculum size, native microbial load and Pseudomonas fluorescens 2-79. The obtained model fits well to the experimental data, with standard errors less than ten percent of the fitted average values. The results show that the MPD of Salmonella is not only dictated by performance characteristics of Salmonella but depends on the characteristics of the indigenous microbial population like total number of cells and its growth rate. The model can improve the predictions of microbiological growth in quantitative microbial risk assessments. Using this model, the effects of preventive measures to reduce pathogenic load and a concurrent effect on the background population can be better evaluated. If competing microorganisms are more sensitive to a particular decontamination method, a pathogenic microorganism may grow faster and reach a higher level. More knowledge regarding the effect of the indigenous microbial population (size, diversity, composition) of food products on pathogen dynamics is needed in order to make adequate predictions of pathogen dynamics on various food products. PMID:23456855

Rijgersberg, Hajo; Franz, Eelco; Nierop Groot, Masja; Tromp, Seth-Oscar

2013-07-01

293

Quantitative seasonal aspects of zooplankton in the Delaware River estuary  

Microsoft Academic Search

The Delaware, a major Coastal Plain estuary about 90 miles long, was quantitatively sampled for net zooplankton at quarterly\\u000a intervals over a two-year period (#2 bolting cloth on Clarke-Bumpus samplers for 1-hour tows). The principal species were\\u000a counted from 20-foot depth intervals and for 13 channel stations distributed from the Atlantic Ocean to fresh water. Accompanying\\u000a hydrographic data were taken

L. E. Cronin; Joanne C. Daiber; E. M. Hulbert

1962-01-01

294

Phytoplankton, not allochthonous carbon, sustains herbivorous zooplankton production  

PubMed Central

Terrestrial organic matter inputs have long been thought to play an important role in aquatic food web dynamics. Results from recent whole lake 13C 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 ?20% of the flux of particulate carbon available to herbivorous zooplankton, this food source accounted for ?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

2009-01-01

295

Light scattering by selected zooplankton from the Gulf of Aqaba.  

PubMed

Light scattering by zooplankton was investigated as a major factor undermining transparency camouflage in these pelagic animals. Zooplankton of differing transparencies--including the hyperiid amphipod Anchylomera blossevillei, an unknown gammarid amphipod species, the brine shrimp Artemia salina, the euphausiid shrimp Euphausia diomedeae, the isopod Gnathia sp., the copepods Pontella karachiensis, Rhincalanus sp. and Sapphirina sp., the chaetognath Sagitta elegans and an enteropneust tornaria larva--were illuminated dorsally with white light (400-700 nm). Spectral measurements of direct transmittance as well as relative scattered radiances at angles of 30 degrees , 90 degrees , 150 degrees and 180 degrees from the light source were taken. The animals sampled had transparencies between 1.5% and 75%. For all species, the highest recorded relative scattered radiance was at 30 degrees , with radiances reaching 38% of the incident radiance for the amphipod A. blossevillei. Scattering patterns were also found to be species-specific for most animals. Relative scattered radiances were used to estimate sighting distances at different depths. These calculations predict that all of the examined zooplankton are brighter than the background radiance when viewed horizontally, or from diagonally above or below at shallow depths. Thus, in contrast to greater depths, the best strategy for detecting transparent zooplankton in the epipelagic environment may be to search for them from above while looking diagonally downwards, looking horizontally or looking from below diagonally upwards. Looking directly upwards proved to be more beneficial than the other viewing angles only when the viewed animal was at depths greater than 40 m. PMID:17951413

Gagnon, Y L; Shashar, N; Warrant, E J; Johnsen, S J

2007-11-01

296

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

297

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.” PMID:19336293

Sabuncu, Mert R.; Balci, Serdar K.; Shenton, Martha E.; Golland, Polina

2009-01-01

298

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

299

Increased zooplankton PAH concentrations across hydrographic fronts in the East China Sea.  

PubMed

The Changjiang has transported large quantities of polycyclic aromatic hydrocarbons (PAHs) to the East China Sea (ECS), but information of these pollutants in zooplankton is limited. To understand PAHs pollution in zooplankton in the ECS, total concentrations of PAHs in zooplankton from surface waters were measured. Values of PAHs ranged from 2 to 3500 ng m(-3) in the ECS, with highest PAHs levels located at the salinity front between the Changjiang Diluted Water (CDW) and the mid-shelf waters. In contrast, concentrations of zooplankton PAHs in the mid-shelf and outer-shelf waters were significantly lower (2-23 ng m(-3)) than those in the CDW. These results demonstrate that PAHs are conspicuously accumulated in zooplankton at the salinity front between the CDW and the mid-shelf waters. These higher levels of PAHs in zooplankton at the salinity front may be further biomagnified in marine organisms of higher trophic levels through their feeding activities. PMID:24775063

Hung, Chin-Chang; Ko, Fung-Chi; Gong, Gwo-Ching; Chen, Kuo-Shu; Wu, Jian-Ming; Chiang, Hsin-Lun; Peng, Sen-Chueh; Santschi, Peter H

2014-06-15

300

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

301

Sexual Reproduction in a Simple Growth Population Model  

NASA Astrophysics Data System (ADS)

One of the most important characteristics in the survival of a species is related to the kind of reproduction responsible for the offspring generation. However, only in the last years the role played by sexual reproduction has been investigated. Then, for a better understanding of this kind of process we introduce, in this work, a surface reaction model that describes the role of the sexual reproduction. In our model two different elements of the species, representing male and female, can interact to reproduce a new element. The sex of this new element is chosen with a given probability and in order to take into account the mortality rate we introduce another kind of individual. The value of the spatial density of this element remains constant during the time evolution of the system. The model is studied using Monte Carlo simulations and mean field approximation. Depending on the values of the control parameters of the model, the system can attain two stationary states: In one of them the population survives and in the other it can be extinguished. Besides, accordingly to our results, the phase diagram of the model shows a discontinuous transition between these two states.

Lemos, Carlos Gentil Oro; Santos, Marcio

2012-05-01

302

Diel vertical migration: Ecological controls and impacts on the biological pump in a one-dimensional ocean model  

NASA Astrophysics Data System (ADS)

vertical migration (DVM) of zooplankton and micronekton is widespread in the ocean and forms a fundamental component of the biological pump, but is generally overlooked in global models of the Earth system. We develop a parameterization of DVM in the ocean and integrate it with a size-structured NPZD model. We assess the model's ability to recreate ecosystem and DVM patterns at three well-observed Pacific sites, ALOHA, K2, and EQPAC, and use it to estimate the impact of DVM on marine ecosystems and biogeochemical dynamics. Our model includes the following: (1) a representation of migration dynamics in response to food availability and light intensity; (2) a representation of the digestive and metabolic processes that decouple zooplankton feeding from excretion, egestion, and respiration; and (3) a light-dependent parameterization of visual predation on zooplankton. The model captures the first-order patterns in plankton biomass and productivity across the biomes, including the biomass of migrating organisms. We estimate that realistic migratory populations sustain active fluxes to the mesopelagic zone equivalent to between 15% and 40% of the particle export and contribute up to half of the total respiration within the layers affected by migration. The localized active transport has important consequences for the cycling of oxygen, nutrients, and carbon. We highlight the importance of decoupling zooplankton feeding and respiration and excretion with depth for capturing the impact of migration on the redistribution of carbon and nutrients in the upper ocean.

Bianchi, Daniele; Stock, Charles; Galbraith, Eric D.; Sarmiento, Jorge L.

2013-04-01

303

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

304

A Diffusion Model in Population Genetics with Mutation and Dynamic Fitness  

E-print Network

A Diffusion Model in Population Genetics with Mutation and Dynamic Fitness Mike O'Leary Department in Genetics Vanderbilt 2008 2 / 52 #12;The Discrete Model Consider a single haploid panmictic population in Genetics Vanderbilt 2008 3 / 52 #12;The Discrete Model Let the fraction of the population with allele Ai

O'Leary, Michael

305

A bio-physical coastal ecosystem model for assessing environmental effects of marine bivalve aquaculture  

Microsoft Academic Search

A simple lower trophic level, bio-physical marine ecosystem model is developed for the purpose of assessing the environmental effects of bivalve aquaculture in coastal embayments. The ecosystem box model includes pelagic and benthic components and describes the cycling of a most-limiting nutrient. The pelagic compartment is comprised of phytoplankton, zooplankton, nutrients and detritus. These populations interact following predator–prey dynamics and

Michael Dowd

2005-01-01

306

Limited-Information Modeling of Loggerhead Turtle Population Size  

E-print Network

. In traditional capture-recapture experiments to estimate the size of an animal population, individual animals of a population (e.g., an animal population) whose members cannot be counted exactly because, practically, many of captures for indi- vidual animals are made and are critical to inference about the population size. We

Hitchcock, David B.

307

Modelling and assessment of South African elephant Loxodonta africana population persistence  

Microsoft Academic Search

The use of a quantitative population growth model to investigate the persistence of South African elephant populations is\\u000a explored. The model provides quantitative assessments of population persistence and confidence intervals for estimated parameters\\u000a based purely on population size estimates. The analysis supports the view that most of the larger populations in the region\\u000a are secure. This view is further supported

A. S. van Jaarsveld; A. O. Nicholls; M. H. Knight

1999-01-01

308

Modeling lesser snow geese page 1 Modeling the Midcontinent Population of Lesser Snow Geese  

E-print Network

(eric.reed@ec.gc.ca), Canadian Wildlife Service, Migratory Birds Conservation Division, Place Vincent through changes in harvest regulations, thus using North American hunters as the main management toolModeling lesser snow geese ­ page 1 Modeling the Midcontinent Population of Lesser Snow Geese RF

Rockwell, Robert F.

309

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

310

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

PubMed Central

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 species from various taxonomic phyla. Here we present the results of single-gene zooplankton community analysis using a method that determines a large number of mitochondrial COI gene sequences from a bulk zooplankton sample. This approach will enable us to estimate the species richness of almost the entire zooplankton community. Results A sample was collected from a depth of 721 m to the surface in the western equatorial Pacific off Pohnpei Island, Micronesia, with a plankton net equipped with a 2-m2 mouth opening. A total of 1,336 mitochondrial COI gene sequences were determined from the cDNA library made from the sample. From the determined sequences, the occurrence of 189 species of zooplankton was estimated. BLASTN search results showed high degrees of similarity (>98%) between the query and database for 10 species, including holozooplankton and merozooplankton. Conclusion In conjunction with the Census of Marine Zooplankton and Barcode of Life projects, single-gene zooplankton community analysis will be a powerful tool for estimating the species richness of zooplankton communities. PMID:19758460

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

2009-01-01

311

Basic Concepts in Population Modeling, Simulation, and Model-Based Drug Development: Part 3--Introduction to Pharmacodynamic Modeling Methods  

PubMed Central

Population pharmacodynamic (PD) models describe the time course of drug effects, relating exposure to response, and providing a more robust understanding of drug action than single assessments. PD models can test alternative dose regimens through simulation, allowing for informed assessment of potential dose regimens and study designs. This is the third paper in a three-part series, providing an introduction into methods for developing and evaluating population PD models. Example files are available in the Supplementary Data. PMID:24384783

Upton, R N; Mould, D R

2014-01-01

312

Effects of stochastic population fluctuations in two models of biological macroevolution  

NASA Astrophysics Data System (ADS)

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. In one model, species can make either predator-prey, mutualistic, or competitive interactions, while the other model allows only predator-prey interactions. When the noise in the population dynamics is strong enough, both models show intermittent behavior and their power spectral densities show approximate 1/ f fluctuations. In the noiseless limit, the two models have different power spectral densities. For the predator-prey model, 1/ f2 fluctuations appears, indicating random-walk like behavior, while the other model still shows 1/ f noise. These results indicate that stochastic population fluctuations may significantly affect long-time evolutionary dynamics.

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

313

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. PMID:22761736

Miranda, Luciano; de Souza, Adauto J. F.; Ferreira, Fernando F.; Campos, Paulo R. A.

2012-01-01

314

Model of energetic populations at Ganymede, implications for an orbiter  

NASA Astrophysics Data System (ADS)

A model is developed to study the energetic particle populations in Ganymede's magnetosphere. The main objective is to estimate to what extent the moon could protect an orbiter from radiations. Using Liouville's theorem, the phase space density of particles coming from Jupiter's magnetosphere is calculated at any point of Ganymede's environment. Up to energies of ˜50-100 keV for ions and ˜10-20 MeV for electrons, Ganymede's magnetic field appears to be able to form distinctive populations as loss-cones over the polar caps and radiation belts. At larger energies, these features are blurred by Larmor radius effects; the moon absorption simply creates a quasi-isotropic layer of ˜500 km thickness where the flux is reduced by ˜40-50%. The predictions are compared to Galileo measurements. In particular, we demonstrate the importance of the moon sweeping in reducing the flux over the polar caps. Interestingly, this can be accounted for by assuming that the particles bouncing between Jupiter and Ganymede are ideally scattered in pitch angle and permanently re-fill the loss-cone, which increases the precipitation on Ganymede's polar cap. In overall, it is estimated that the radiation dose received by an orbiter of Ganymede will be reduced by more than 50-60% compared to the expected dose at Jupiter/Ganymede distance. This should have a positive impact on the design of a future orbiter of Ganymede.

Allioux, Renaud; Louarn, Philippe; André, Nicolas

2013-04-01

315

Consistent two-population lattice Boltzmann model for thermal flows  

NASA Astrophysics Data System (ADS)

Theory of two-population lattice Boltzmann equations for thermal flow simulations is revisited. The present approach makes use of a consistent division of the conservation laws between the two lattices, where mass and the momentum are conserved quantities on the first lattice, and the energy is conserved quantity of the second lattice. The theory of such a division is developed, and the advantage of energy conservation in the model construction is demonstrated in detail. The present fully local lattice Boltzmann theory is specified on the standard lattices for the simulation of thermal flows. Extension to the subgrid entropic lattice Boltzmann formulation is also given. The theory is validated with a set of standard two-dimensional simulations including planar Couette flow and natural convection in two dimensions.

Karlin, I. V.; Sichau, D.; Chikatamarla, S. S.

2013-12-01

316

HIV and population dynamics: A general model and maximum-likelihood standards for East Africa  

Microsoft Academic Search

In high-prevalence populations, the HIV epidemic undermines the validity of past empirical models and related demographic\\u000a techniques. A parsimonious model of HIV and population dynamics is presented here and fit to 46,000 observations, gathered\\u000a from 11 East African populations. The fitted model simulates HIV and population dynamics with standard demographic inputs\\u000a and only two additional parameters for the onset and

Patrick Heuveline

2003-01-01

317

Evaluating Habitat as a Surrogate for Population Viability Using a Spatially Explicit Population Model  

Microsoft Academic Search

Because data for conservation planning are always limited, surrogates are often substituted for intractable measurements such\\u000a as species richness or population viability. We examined the ability of habitat quality to act as a surrogate for population\\u000a performance for both Red-shouldered Hawks (Buteo lineatus) and Northern Goshawks (Accipiter gentilis). We compared simple measures of habitat quality to estimates of population growth

Joshua J. Lawler; Nathan H. Schumaker

2004-01-01

318

Modelling the evolution of the space debris population  

NASA Astrophysics Data System (ADS)

The current space activities are already disturbed and jeopardized by the growing number of orbiting debris. Those planned for the near future, such as the launch of large satellite constellations and the construction of the international space station, are even more sensitive to the evolution of the space environment. Therefore, a clear picture of the present situation in Earth orbit and its future evolution is needed. In this paper we describe in some details the work we have carried out on this problem in the last several years. Starting from the current population and simulating a reasonable scenario for the space activities in the next decades, we have obtained plausible quantitative models of the possible future space environment. We summarize some results concerning the effectiveness of possible mitigation measures and assess the robustness of these results, by checking how sensitively they depend upon the initial conditions and the choice of some model parameters. We also analyze the effect of the launch of a number of satellite constellations, showing the importance of the adoption of some debris prevention measures in their launch policies. Finally, we study the possible problems arising from the recent discovery of a new family of debris composed by drops of NaK coolant, that leaked outside the nuclear reactors of the Soviet RORSAT-class satellites. Our preliminary results indicate that these drops are going to cause an increasing number of small-scale, possible satellite-damaging impacts but, due to their small size, no additional catastrophic collisions; therefore their influence on the long-term evolution of the overall debris population is limited.

Rossi, A.; Anselmo, L.; Cordelli, A.; Farinella, P.; Pardini, C.

1998-12-01

319

Modeling white-tailed deer Odocoileus virginianus population control by contraception  

Microsoft Academic Search

Large populations of white-tailed deer Odocoileus virginianus present conservation problems in suburban landscapes because of limited population control options. We used the GAPPS II modeling system to simulate temporal effects of contraception on deer population control and the interaction between contraception and uncertain immigration rates. Contraception rates less than 50% of female deer curbed population growth with a long (30

Steven W. Seagle; John D. Close

1996-01-01

320

A simple model of optimal population coding for sensory systems.  

PubMed

A fundamental task of a sensory system is to infer information about the environment. It has long been suggested that an important goal of the first stage of this process is to encode the raw sensory signal efficiently by reducing its redundancy in the neural representation. Some redundancy, however, would be expected because it can provide robustness to noise inherent in the system. Encoding the raw sensory signal itself is also problematic, because it contains distortion and noise. The optimal solution would be constrained further by limited biological resources. Here, we analyze a simple theoretical model that incorporates these key aspects of sensory coding, and apply it to conditions in the retina. The model specifies the optimal way to incorporate redundancy in a population of noisy neurons, while also optimally compensating for sensory distortion and noise. Importantly, it allows an arbitrary input-to-output cell ratio between sensory units (photoreceptors) and encoding units (retinal ganglion cells), providing predictions of retinal codes at different eccentricities. Compared to earlier models based on redundancy reduction, the proposed model conveys more information about the original signal. Interestingly, redundancy reduction can be near-optimal when the number of encoding units is limited, such as in the peripheral retina. We show that there exist multiple, equally-optimal solutions whose receptive field structure and organization vary significantly. Among these, the one which maximizes the spatial locality of the computation, but not the sparsity of either synaptic weights or neural responses, is consistent with known basic properties of retinal receptive fields. The model further predicts that receptive field structure changes less with light adaptation at higher input-to-output cell ratios, such as in the periphery. PMID:25121492

Doi, Eizaburo; Lewicki, Michael S

2014-08-01

321

Quantitative estimation of the cost of parasitic castration in a Helisoma anceps population using a matrix population model.  

PubMed

Larval trematodes frequently castrate their snail intermediate hosts. When castrated, the snails do not contribute offspring to the population, yet they persist and compete with the uninfected individuals for the available food resources. Parasitic castration should reduce the population growth rate lambda, but the magnitude of this decrease is unknown. The present study attempted to quantify the cost of parasitic castration at the level of the population by mathematically modeling the population of the planorbid snail Helisoma anceps in Charlie's Pond, North Carolina. Analysis of the model identified the life-history trait that most affects lambda, and the degree to which parasitic castration can lower lambda. A period matrix product model was constructed with estimates of fecundity, survival, growth rates, and infection probabilities calculated in a previous study. Elasticity analysis was performed by increasing the values of the life-history traits by 10% and recording the percentage change in lambda. Parasitic castration resulted in a 40% decrease in lambda of H. anceps. Analysis of the model suggests that decreasing the size at maturity was more effective at reducing the cost of castration than increasing survival or growth rates of the snails. The current matrix model was the first to mathematically describe a snail population, and the predictions of the model are in agreement with published research. PMID:18973413

Negovetich, N J; Esch, G W

2008-10-01

322

MODELING THE IMPLICATIONS OF STRESSOR INTERACTIONS FOR WILDLIFE POPULATIONS  

EPA Science Inventory

Wildlife risk assessments have traditionally explored the consequences, for a single individual, of exposure to a single stressor. But attention has recently included the study of population-level responses to exposure. Wildlife populations are often subjected to multiple stres...

323

Evaluation of alternative management strategies of muskrat Ondatra zibethicus population control using a population model  

Microsoft Academic Search

Muskrats Ondatra zibethicus are considered a pest species in the Netherlands, and a year-round control programme is in effect. Currently, the agency responsible for the management of muskrat populations in the Netherlands (the LCCM) is preparing for field studies to compare alternative strategies of control. In order to decide on the specific design of such field studies, a population dynamic

D. Bos; R. Ydenberg

2011-01-01

324

EVALUATING HABITAT AS A SURROGATE FOR POPULATION VIABILITY USING A SPATIALLY EXPLICIT POPULATION MODEL  

EPA Science Inventory

Because data for conservation planning are always limited, surrogates are often substituted for intractable measurements such as species richness or population viability. We examined the ability of habitat quality to act as a surrogate for population performance for both Red-sho...

325

Maryland's Special Populations Cancer Network: Cancer Health Disparities Reduction Model  

Microsoft Academic Search

Cancer in Maryland is a serious health concern for minority and underserved populations in rural and urban areas. This report describes the National Cancer Institute (NCI) supported Maryland Special Populations Cancer Network (MSPN), a community- academic partnership. The MSPN's priority populations include African Americans, Native Americans, and other medically underserved residents of rural and urban areas. The MSPN has established

Claudia R. Baquet; Kelly M. Mack; Joy Bramble; Mary DeShields; Delores Datcher; Mervin A. Savoy; Kery Hummel; Shiraz I. Mishra; Sandra E. Brooks; Stephanie Boykin-Brown

2005-01-01

326

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

SciTech Connect

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 correlated 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. 54 refs., 4 figs., 2 tabs.

Malloy, K.D.; Holman, M.A. [Northeastern Univ., Boston, MA (United States)] [Northeastern Univ., Boston, MA (United States); Mitchell, D. [Univ. of Texas, Smithville, TX (United States)] [and others] [Univ. of Texas, Smithville, TX (United States); and others

1997-02-18

327

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

PubMed

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. PMID:9037040

Malloy, K D; Holman, M A; Mitchell, D; Detrich, H W

1997-02-18

328

Realistic population dynamics in epidemiological models: the impact of population decline on the dynamics of childhood infectious diseases  

Microsoft Academic Search

Most contributions in the field of mathematical modelling of childhood infectious diseases transmission dynamics have focused on stationary or exponentially growing populations. In this paper an epidemiological model with realistic demography is used to investigate the impact of the non-equilibrium conditions typical of the transition to sustained below replacement fertility (BRF) recently observed in a number of western countries, upon

Piero Manfredi; John R. Williams

2004-01-01

329

POPULATION GENETICS MODELS WITH SKEWED FERTILITIES: A FORWARD AND BACKWARD ANALYSIS  

E-print Network

POPULATION GENETICS MODELS WITH SKEWED FERTILITIES: A FORWARD AND BACKWARD ANALYSIS THIERRY HUILLET, MARTIN M¨OHLE Abstract. Discrete population genetics models with unequal (skewed) fertil- ities. For each class the asymptotic behavior as the total population size N tends to infinity is investigated

Paris-Sud XI, Université de

330

Evaluating management strategies and recovery of an invasive grass ( Agropyron cristatum) using matrix population models  

Microsoft Academic Search

The success of invasive species control depends on management type, duration and recovery following management. Population models were here used to compare response and recovery of clipped and herbicide-treated Agropyron cristatum populations invading native North American grasslands. Matrix models were produced for experimental populations of A. cristatum using probabilities of tussocks changing size class (based on tiller number), as well

Malin J. Hansen

2007-01-01

331

Endemic threshold results in an age-duration-structured population model for HIV infection  

E-print Network

abusers, blood transfusion, etc. Therefore, in the real, the susceptible population is composedEndemic threshold results in an age-duration-structured population model for HIV infection Hisashi In this paper we consider an age-duration-structured population model for HIV infection in a homosex- ual

Inaba, Hisashi

332

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

333

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

334

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

335

Seasonal Abundance and Distribution of Zooplankton, Fish Eggs, and Fish Larvae in the Eastern Gulf of Mexico, 1972-74.  

National Technical Information Service (NTIS)

Zooplankton volumes and abundance of fish eggs and fish larvae were determined for stations on 12 cruises to the western Florida continental shelf. Contour charts of zooplankton volumes and of ichthyoplankton abundance are presented. A marked seasonality ...

E. D. Houde, N. Chitty

1976-01-01

336

Can a more realistic model error structure improve the parameter estimation in modelling the dynamics of sh populations?  

E-print Network

the dynamics of ®sh populations? Y. Chena,* , J.E. Paloheimob a Fisheries Conservation Chair Program, Fisheries 1998 Abstract Mathematical models are commonly used to describe the dynamics of ®sh populations the dynamics of ®sh populations. Using a simple cohort-based model as an example in this study, we examine

Chen, Yong

337

Population Growth: Experimental Models Using Duckweed (Lemna spp.)  

NSDL National Science Digital Library

Experiment 1, "Dynamics of population growth: exponential and logistic growth" examines continuous population growth by growing duckweeds (Lemna spp.) Experiment 2, "Resource limitation and population growth" examines the conditions that result in maximum population growth of Lemna by manipulating the resources that limit growth including nutrients, light, and surface area. Experiment 3, "Population growth and resource competition in Lemna minor and Spirodela polyrhiza", studies the population growth and competition of two species of floating aquatic plants. In Part A the growth of lab populations of Lemna minor and Sprirodela polyrhiza grown alone and in mixed cultures are monitored. In Part B the magnitude of interaction is explored by growing monocultures and mixed cultures under conditions of two nutrient concentrations and two levels of light intensity.

Jefferies, R. L.

2010-02-16

338

Modelling HIV in the injecting drug user population and the male homosexual population in a developed country context.  

PubMed

In many high income countries men who have sex with men (MSM) and injecting drug users (IDUs) are the two groups with the highest HIV prevalence. Yet these two groups are not mutually exclusive, and those MSM who are also IDUs (MSM-IDUs) may be particularly vulnerable to HIV infection. This may be particularly relevant to the IDU population in countries, like the UK, with a much lower HIV prevalence amongst IDUs than MSM, as the MSM-IDUs could provide a route of HIV infection into the IDU population. In this research two alternative modelling approaches that describe the transmission dynamics of HIV within the IDU, MSM, and heterosexual populations are proposed. These models are constructed with two aims. The first is to investigate the possible impact of interventions that target HIV transmission in the MSM and IDU populations, and the second aim is to investigate the impact of the model structure on the model results. An examination of the assortativity of mixing between risk groups is also undertaken. The models are parameterised for England and Wales. While the MSM-IDU population is small, targeting MSM-IDUs was the most efficient intervention strategy in terms of cases averted per 100 individuals targeted with the intervention. Sensitivity analysis showed that variations in the assumed assortativity of mixing between the population groups in both models have a large impact on model results. This means that to generate quantitatively robust estimates for the impact of different intervention strategies it will be necessary to obtain estimates for assortativity values through empirical work. PMID:22325014

Sutton, A J; House, T; Hope, V D; Ncube, F; Wiessing, L; Kretzschmar, M

2012-03-01

339

Preliminary study of the effect of pumped-storage plant operation on zooplankton  

Microsoft Academic Search

The hydromechanical effect of hydroelectric stations on zooplankton is customarily regarded as a constantly acting and comparatively harmless factor, since its destruction is inevitable when water masses are passed through hydroelectric stations, but its capacity for restoration is high (i.e., destruction of the zooplankton of the forebay is compensated by its production in the after bay). It is not known

Y. Y. Tseyeb; G. A. Zhdanova

1980-01-01

340

SPATIAL PATTERNS IN ASSEMBLAGE STRUCTURES OF PELAGIC FORAGE FISH AND ZOOPLANKTON IN WESTERN LAKE SUPERIOR  

EPA Science Inventory

This manuscript reports on the spatial distribution of zooplankton and forage fish in western Lake Superior. Fish and zooplankton assemblages are shown to differ substantially in abundance and size structure both between the open lake and nearshore regions and between two differe...

341

Zooplankton invasions: a brief review, plus two case studies from the northeast Pacific Ocean  

Microsoft Academic Search

Invasions of aquatic habitats by non-indigenous species (NIS), including zooplankton, are occurring at an alarming rate and are causing global concern. Although hundreds of such invasions have now been documented, surprisingly little is known about the basic biology and ecology of these invaders in their new habitats. Here we provide an overview of the published literature on NIS zooplankton, separated

Stephen M. Bollens; Jeffery R. Cordell; Sean Avent; Rian Hooff

2002-01-01

342

Benthic and pelagic food resources for zooplankton in shallow high-latitude lakes and ponds  

E-print Network

Benthic and pelagic food resources for zooplankton in shallow high-latitude lakes and ponds MILLA. 2. In this study we quantified zooplankton food sources and feeding rates in the shallow waters polar desert (Resolute, Nunavut). Five substrate types were tested (beads, bacteria, picophytoplankton

Vincent, Warwick F.

343

Relative significance of direct and indirect effects of predation by planktivorous fish on zooplankton  

Microsoft Academic Search

One of the most obvious features of tropical lakes and reservoirs is the small body size of their zooplankton taxa. It is believed that this is the result of high and persistent predation by abundant planktivorous fish, which select large-bodied zooplankton prey thus making them more vulnerable to extinction in tropical as compared to temperate habitats. Do these extinctions result

Z. Maciej Gliwicz

1994-01-01

344

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

345

The effects of salinity on aquatic plant germination and zooplankton hatching from two wetland sediments  

Microsoft Academic Search

SUMMARY 1. The effect of increasing salinity on the emergence of zooplankton eggs and the germination of aquatic plant seeds from the sediment of two wetlands was examined. Salinity was found to cause reductions in species richness and abundance of aquatic plants and zooplankton at salinities between 1000 and 5000 mg L)1. Aquatic plants also had an associated decrease in

DARYL L. N IELSEN; K ATHARINE; C ROSSLE ´; K EN H ARRIS; MICHAEL H EALEY; I RENE J AROSINSKI

2003-01-01

346

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...

347

PHYTOPLANKTON AND ZOOPLANKTON SEASONAL DYNAMICS IN A SUBTROPICAL ESTUARY: IMPORTANCE OF CYANOBACTERIA  

EPA Science Inventory

Murrell, Michael C. and Emile M. Lores. 2004. Phytoplankton and Zooplankton Seasonal Dynamics in a Subtropical Estuary: Importance of Cyanobacteria. J. Plankton Res. 26(3):371-382. (ERL,GB 1190). A seasonal study of phytoplankton and zooplankton was conducted from 1999-20...

348

What is the windage of zooplankton? Turbulence avoidance and the wind-driven transport of plankton.  

E-print Network

What is the windage of zooplankton? Turbulence avoidance and the wind-driven transport of plankton of zooplankton in the surface Ekman layer at realistic wind speeds. Plankton that avoid turbulence by moving the directly wind driven transport of plankton. The direct effect of wind-forcing is transmitted through

Pringle, James "Jamie"

349

Research Article Water residence time as a driving force of zooplankton structure  

E-print Network

Research Article Water residence time as a driving force of zooplankton structure and succession years and assessed the importance of water residence time for zooplankton dynamics. Crustacean abundance and biomass were significantly correlated with water residence time and temperature, but showed no significant

Sommaruga, Ruben

350

COMPOSITION, ABUNDANCE, AND DISTRIBUTION OF ZOOPLANKTON IN THE NEW YORK BIGHT, SEPTEMBER 1974-SEPTEMBER 1975  

E-print Network

COMPOSITION, ABUNDANCE, AND DISTRIBUTION OF ZOOPLANKTON IN THE NEW YORK BIGHT, SEPTEMBER 1974 during autumn 1974 and summer 1975, an offshore (>50 m water depth) zooplankton abundance maximum in March dominated by the pteropodLimacina retroversa, a second offshore maximum in May characterized

351

Distribution, biomass and ecology of meso-zooplankton in the Northern Adriatic Sea  

Microsoft Academic Search

Two oceanographic cruises were carried out in the northern Adriatic Sea, from June, 1996 to February, 1997. Samples were collected using a BIONESS electronic multinet (204 samples on 54 stations) along inshore-offshore sections. Zooplankton abundance and biomass were estimated in relation to the variability of temperature, salinity and fluorescence. Spatial and vertical distribution patterns of the most important zooplankton groups

L. Guglielmo; O. Sidoti; A. Granata; G. Zagami

2002-01-01

352

Diel variation of zooplankton distributions in Hawaiian waters favors horizontal diel migration by midwater micronekton  

Microsoft Academic Search

Micronekton in deep-scattering layers around the Hawaiian Islands undergo diel migrations with both vertical and horizontal components. We sought to determine whether resource availability provides an adaptive explanation for this migration. We simultaneously measured the spatio-temporal patterns of micronekton, using acoustics and imaging optics, and of their potential zooplankton prey, using net tows, acoustics, and optics. Zooplankton biomass, density, and

Kelly J. Benoit-Bird; Marnie Jo Zirbel; Margaret A. McManus

2008-01-01

353

Introduction to special section on Analysis of Zooplankton Distributions Using the Optical Plankton Counter  

Microsoft Academic Search

We briefly introduce the optical plankton counters (OPCs) currently in use and summarize major themes and conclusions of papers from this special section. These collected papers demonstrate that the OPC and the new laser OPC (LOPC) are useful tools for mapping fine-scale distributions of zooplankton over broad expanses of space and for examining patterns in the size structure of zooplankton

Henry A. Vanderploeg; Michael R. Roman

2006-01-01

354

Blue Crab Population Modeling: Individual-Based vs. Stage-Based Models Brian Weeks and Michael Childress  

E-print Network

seen in populations. We created an individual-based model using NetLogo and a stage-based model using an individually-based model using NetLogo in which we have modeled blue crab populations in the Ashley River and NetLogo. Set probabilities of moving to a higher stage Create Stages 1-20 Assign Fecundities to stages

Childress, Michael J.

355

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

356

Can Binary Population Synthesis Models Be Tested With Hot Subdwarfs ?  

NASA Astrophysics Data System (ADS)

Models of binary star interactions have been successful in explaining the origin of field hot subdwarf (sdB) stars in short period systems. The hydrogen envelopes around these core He-burning stars are removed in a "common envelope" evolutionary phase. Reasonably clean samples of short-period sdB+WD or sdB+dM systems exist, that allow the common envelope ejection efficiency to be estimated for wider use in binary population synthesis (BPS) codes. About one-third of known sdB stars, however, are found in longer-period systems with a cool G or K star companion. These systems may have formed through Roche-lobe overflow (RLOF) mass transfer from the present sdB to its companion. They have received less attention, because the existing catalogues are believed to have severe selection biases against these systems, and because their long, slow orbits are difficult to measure. Are these known sdB+cool systems worth intense observational effort? That is, can they be used to make a valid and useful test of the RLOF process in BPS codes? We use the Binary Stellar Evolution (BSE) code of Hurley et al. (2002), mapping sets of initial binaries into present-day binaries that include sdBs, and distinguishing "observable" sdBs from "hidden" ones. We aim to find out whether (1) the existing catalogues of sdBs are sufficiently fair samples of the kinds of sdB binaries that theory predicts, to allow testing or refinement of RLOF models; or instead whether (2) large predicted hidden populations mandate the construction of new catalogues, perhaps using wide-field imaging surveys such as 2MASS, SDSS, and Galex. This work has been partially supported by NASA grant NNG05GE11G and NSF grants PHY 03-26281, PHY 06-00953 and PHY 06-53462. This work is also supported by the Center for Gravitational Wave Physics, which is supported by the National Science Foundation under cooperative agreement PHY 01-14375.

Kopparapu, Ravi Kumar; Wade, R. A.; O'Shaughnessy, R.

2007-12-01

357

The Propagation of Uncertainties in Stellar Population Synthesis Modeling. III. Model Calibration, Comparison, and Evaluation  

Microsoft Academic Search

Stellar population synthesis (SPS) provides the link between the stellar and dust content of galaxies and their observed spectral energy distributions. In the present work, we perform a comprehensive calibration of our own flexible SPS (FSPS) model against a suite of data. These data include ultraviolet, optical, and near-IR photometry, surface brightness fluctuations, and integrated spectra of star clusters in

Charlie Conroy; James E. Gunn

2010-01-01

358

Model or meal? Farm animal populations as models for infectious diseases of humans  

Microsoft Academic Search

In recent decades, theory addressing the processes that underlie the dynamics of infectious diseases has progressed considerably. Unfortunately, the availability of empirical data to evaluate these theories has not grown at the same pace. Although laboratory animals have been widely used as models at the organism level, they have been less appropriate for addressing issues at the population level. However,

Patrick Ayscue; Renata Ivanek; Yrjö T. Gröhn; Cristina Lanzas

2009-01-01

359

Ability of matrix models to explain the past and predict the future of plant populations.  

USGS Publications Warehouse

Uncertainty associated with ecological forecasts has long been recognized, but forecast accuracy is rarely quantified. We evaluated how well data on 82 populations of 20 species of plants spanning 3 continents explained and predicted plant population dynamics. We parameterized stage-based matrix models with demographic data from individually marked plants and determined how well these models forecast population sizes observed at least 5 years into the future. Simple demographic models forecasted population dynamics poorly; only 40% of observed population sizes fell within our forecasts' 95% confidence limits. However, these models explained population dynamics during the years in which data were collected; observed changes in population size during the data-collection period were strongly positively correlated with population growth rate. Thus, these models are at least a sound way to quantify population status. Poor forecasts were not associated with the number of individual plants or years of data. We tested whether vital rates were density dependent and found both positive and negative density dependence. However, density dependence was not associated with forecast error. Forecast error was significantly associated with environmental differences between the data collection and forecast periods. To forecast population fates, more detailed models, such as those that project how environments are likely to change and how these changes will affect population dynamics, may be needed. Such detailed models are not always feasible. Thus, it may be wiser to make risk-averse decisions than to expect precise forecasts from models.

McEachern, Kathryn; Crone, Elizabeth E.; Ellis, Martha M.; Morris, William F.; Stanley, Amanda; Bell, Timothy; Bierzychudek, Paulette; Ehrlen, Johan; Kaye, Thomas N.; Knight, Tiffany M.; Lesica, Peter; Oostermeijer, Gerard; Quintana-Ascencio, Pedro F.; Ticktin, Tamara; Valverde, Teresa; Williams, Jennifer I; Doak, Daniel F.; Ganesan, Rengaian; Thorpe, Andrea S.; Menges, Eric S.

2013-01-01

360

Response of zooplankton to nutrient enrichment and fish in shallow lakes: a pan-European mesocosm experiment  

Microsoft Academic Search

SUMMARY 1. Responses of zooplankton to nutrient enrichment and fish predation were studied in 1998 and 1999 by carrying out parallel mesocosm experiments in six lakes across Europe. 2. Zooplankton community structure, biomass and responses to nutrient and fish manipulation showed geographical and year-to-year differences. Fish had a greater influence than nutrients in regulating zooplankton biomass and especially the relative

KIRSI V AKKILAINEN; T IMO K AIRESALO; J AANA H IETALA; D AVID M. B; ELOY B ECARES; WOUTER J. V; ELLEN V AN D ONK; MARGARITA F ERNANDEZ; MIKAEL G YLLSTROM; MARIA R. M IRACLE; BRIAN M OSS; SUSANA R OMO; JUAN R UEDA

2004-01-01

361

Grazing effects of a freshwater bivalve ( Corbicula leana Prime) and large zooplankton on phytoplankton communities in two Korean lakes  

Microsoft Academic Search

This study examined the effects of a freshwater filter feeding bivalve (Corbicula leana Prime) and large zooplankton (>200 µm, mostly cladocerans and copepods) on the phytoplankton communities in two lakes with contrasting trophic conditions. A controlled experiment was conducted with four treatments (control, zooplankton addition, mussel addition, and both zooplankton and mussel addition), and each established in duplicate 10-l chambers. In

Soon-Jin Hwang; Ho-Sub Kim; Jae-Ki Shin; Jong-Min Oh; Dong-Soo Kong

2004-01-01

362

Composition and sources of near reef zooplankton on a Jamaican forereef along with implications for coral feeding  

Microsoft Academic Search

Nocturnal near-reef zooplankton from the forereef of Discovery Bay, Jamaica, were sampled during winter and summer 1994 using a diver-operated plankton pump with an intake head positioned within centimeters of benthic zooplanktivores. The pump collected zooplankton not effectively sampled by conventional net tows or demersal traps. We found consistently greater densities of zooplankton than did earlier studies that used other

K. B. Heidelberg; K. P. Sebens; J. E. Purcell

2004-01-01

363

The seasonal succession of zooplankton in the Southern Ocean south of Australia, part I: The seasonal ice zone  

NASA Astrophysics Data System (ADS)

Between November 2001 and March 2002 an Australian/Japanese collaborative study completed six passes of a transect line in the Seasonal-Ice Zone (south of 62°S) along 140°E. Zooplankton samples were collected with a NORPAC net on 22-28 November, and a Continuous Plankton Recorder on 10-15 January, 11-12 February, 19-22 February, 25-26 February, and 10-11 March. Zooplankton densities were lowest on 22-28 November (ave=61 individuals (ind) m -3), when almost the entire transect was covered by sea ice. By 10-15 January sea surface temperature had increased by ˜2 °C across the transect line, and the study area was ice-free. Total zooplankton abundance had increased to maximum levels for the season (ave=1301 ind m -3; max=1979 ind m -3), dominated by a "Peak Community" comprising Oithona similis, Ctenocalanus citer, Clausocalanus laticeps, foraminiferans, Limacina spp., appendicularians, Rhincalanus gigas and large calanoid copepodites (C1-3). Total densities declined on each subsequent transect, returning to an average of 169 ind m -3 on 10-11 March. The seasonal density decline was due to the decline in densities of "Peak Community" taxa, but coincided with the rise of Euphausia superba larvae into the surface waters, increased densities of Salpa thompsoni, and an increased contribution of C4 to adult stages to the populations of Calanoides acutus, Calanus propinquus and Calanus simillimus. The seasonal community succession appeared to be influenced by the low sea ice extent and southward projection of the ACC in this region. The relatively warm ACC waters, together with low krill biomass, favoured high densities of small grazers during the January/February bloom conditions. The persistence of relatively warm surface waters in March and the seasonal decrease in chlorophyll a biomass provided favorable conditions for salps, which were able to penetrate south of the Southern Boundary.

Hunt, Brian P. V.; Hosie, Graham W.

2006-07-01

364

Secondary production of freshwater zooplankton communities exposed to a fungicide and to a petroleum distillate in outdoor pond mesocosms.  

PubMed

Ecological risk assessment of chemicals in mesocosms requires measurement of a large number of parameters at the community level. Studies on invertebrate communities usually focus on taxonomic approaches, which only provide insights into taxonomic structure changes induced by chemicals. In the present study, abundance, biomass (B), theoretical production (P), and instantaneous P/B ratio were used as endpoints to assess the effects of the commercial form of the dithiocarbamate fungicide thiram (35 µg/L and 170 µg/L nominal concentrations) and of the hydrocarbon water accommodated fraction (HWAF) of a petroleum distillate (0.01 mg/L, 0.4 mg/L, 2 mg/L, and 20 mg/L loadings) on the zooplankton community in freshwater pond mesocosms. Endpoints were measured during a 4-wk treatment period (1 pulse/wk) followed by a 5-mo posttreatment period to evaluate zooplankton population recovery. The chlorophyll a concentration in water was significantly increased after treatment with HWAF, whereas it was not affected by thiram treatment. Zooplankton abundance-based analysis showed effects on a limited number of taxa, whereas other endpoints (mainly the P/B ratio) revealed that more taxa were impacted, with recovery depending on the chemical and concentration. Exposure to HWAF mainly had a negative impact on cladocerans, which resulted in top-down effects (between cladocerans and phytoplankton). Thiram negatively affected rotifers and copepods, suggesting more direct toxic effects. The results show that the use of secondary production as an endpoint provides a more comprehensive assessment of potential direct and indirect effects of chemicals on a community, and they also support evidence of alteration in functional processes. PMID:24375909

Bayona, Yannick; Roucaute, Ana; Roucaute, Marc; Gorzerino, Caroline; Cailleaud, Kevin; Lagadic, Laurent; Bassères, Anne; Caquet, Thierry

2014-04-01

365

Resolving discrepancies between deterministic population models and individual-based simulations.  

PubMed

This work ties together two distinct modeling frameworks for population dynamics: an individual-based simulation and a set of coupled integrodifferential equations involving population densities. The simulation model represents an idealized predator-prey system formulated at the scale of discrete individuals, explicitly incorporating their mutual interactions, whereas the population-level framework is a generalized version of reaction-diffusion models that incorporate population densities coupled to one another by interaction rates. Here I use various combinations of long-range dispersal for both the offspring and adult stages of both prey and predator species, providing a broad range of spatial and temporal dynamics, to compare and contrast the two model frameworks. Taking the individual-based modeling results as given, two examinations of the reaction-dispersal model are made: linear stability analysis of the deterministic equations and direct numerical solution of the model equations. I also modify the numerical solution in two ways to account for the stochastic nature of individual-based processes, which include independent, local perturbations in population density and a minimum population density within integration cells, below which the population is set to zero. These modifications introduce new parameters into the population-level model, which I adjust to reproduce the individual-based model results. The individual-based model is then modified to minimize the effects of stochasticity, producing a match of the predictions from the numerical integration of the population-level model without stochasticity. PMID:18811412

Wilson, W G

1998-02-01

366

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

367

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

368

Models for management of wildlife populations: lessons from spectacled bears in zoos and grizzly bears in Yellowstone  

Microsoft Academic Search

Models of population dynamics are frequently used in the management and conservation of wildlife populations. They provide a powerful method of quantitatively assessing a population's risk of decline and determining the potential to reverse the decline. Models from recent studies of managed populations are presented. The first model simulates the spectacled bear populations maintained in American Zoo and Aquarium Association

Lisa J. Faust; Rosemary Jackson; Andrew Ford; Joanne M. Earnhardt; Steven D. Thompson

2004-01-01

369

Modeling the dynamics of natural rotifer populations: phase-parametric analysis  

E-print Network

A model of the dynamics of natural rotifer populations is described as a discrete nonlinear map depending on three parameters, which reflect characteristics of the population and environment. Model dynamics and their change by variation of these parameters were investigated by methods of bifurcation theory. A phase-parametric portrait of the model was constructed and domains of population persistence (stable equilibrium, periodic and a-periodic oscillations of population size) as well as population extinction were identified and investigated. The criteria for population persistence and approaches to determining critical parameter values are described. The results identify parameter values that lead to population extinction under various environmental conditions. They further illustrate that the likelihood of extinction can be substantially increased by small changes in environmental quality, which shifts populations into new dynamical regimes.

Faina S. Berezovskaya; Georgy P. Karev; Terry W. Snell

2005-05-24

370

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

371

Zooplankton Feeding on the Nuisance Flagellate Gonyostomum semen  

PubMed Central

The large bloom-forming flagellate Gonyostomum semen has been hypothesized to be inedible to naturally occurring zooplankton due to its large cell size and ejection of long slimy threads (trichocysts) induced by physical stimulation. In a grazing experiment using radiolabelled algae and zooplankton collected from lakes with recurring blooms of G. semen and lakes that rarely experience blooms, we found that Eudiaptomus gracilis and Holopedium gibberum fed on G. semen at high rates, whereas Daphnia cristata and Ceriodaphnia spp. did not. Grazing rates of E. gracilis were similar between bloom-lakes and lakes with low biomass of G. semen, indicating that the ability to feed on G. semen was not a result of local adaptation. The high grazing rates of two of the taxa in our experiment imply that some of the nutrients and energy taken up by G. semen can be transferred directly to higher trophic levels, although the predominance of small cladocerans during blooms may limit the importance of G. semen as a food resource. Based on grazing rates and previous observations on abundances of E. gracilis and H. gibberum, we conclude that there is a potential for grazer control of G. semen and discuss why blooms of G. semen still occur. PMID:23667489

Johansson, Karin S. L.; Vrede, Tobias; Lebret, Karen; Johnson, Richard K.

2013-01-01

372

Modeling vital rates improves estimation of population projection matrices  

Microsoft Academic Search

Population projection matrices are commonly used by ecologists and managers to analyze the dynamics of stage-structured populations. Building projection matrices from data requires estimating transition rates among stages, a task that often entails estimating many parameters with few data. Consequently, large sampling variability in the estimated transition rates increases the uncertainty in the estimated matrix and quantities derived from it,

Kevin Gross; William F. Morris; Michael S. Wolosin; Daniel F. Doak

2006-01-01

373

Modeling the Sustainability of Walleye Populations in Northern Wisconsin Lakes  

Microsoft Academic Search

Population sustainability of walleyes Sander vitreus in the face of angling and spearing fisheries has been a concern of fishery managers in northern Wisconsin since off-reservation tribal fishing rights were affirmed by federal court decisions. We evaluated sustainability of walleye populations across a range of densities that were subjected to various exploitation rates and allocations of angling and spearing harvest

Amy M. Schueller; Michael J. Hansen; Steven P. Newman

2008-01-01

374

Linking population viability, habitat suitability, and landscape simulation models for conservation planning  

Microsoft Academic Search

Methods for habitat modeling based on landscape simulations and population viability modeling based on habitat quality are well developed, but no published study of which we are aware has effectively joined them in a single, comprehensive analysis. We demonstrate the application of a population viability model for ovenbirds (Seiurus aurocapillus) that is linked to realistic landscape simulations using a GIS-based

Michael A. Larson; Frank R. Thompson; Joshua J. Millspaugh; William D. Dijak; Stephen R. Shifley

2004-01-01

375

Modelling fish population movements: from an individual-based representation to an  

E-print Network

Modelling fish population movements: from an individual-based representation to an advection`ete cedex, France Abstract In this paper we address the problem of modelling fish population movements. We is formulated as a biased random walk model in which the velocity of each fish has both a deterministic

Paris-Sud XI, Université de

376

An optimal foraging-based model of hunter-gatherer population dynamics  

Microsoft Academic Search

Population changes for hunter-gatherers are modeled on the basis of nutritional intake, which is determined using an optimal foraging model based upon the optimization technique of linear programming. The population model not only demonstrates how hunter-gatherer demography changes with nutrition, but also shows how their density influences food abundance in the environment which in turn affects their nutritional status. Differences

GARY E. BELOVSKY

1988-01-01

377

Theoretical Population Biology 52, 60 70 (1997) Modelling the Feline Leukemia Virus (FeLV) in  

E-print Network

the circulation of animal retro- viruses has not been modelled until recently (Courchamp et al., 1995). OurTheoretical Population Biology 52, 60 70 (1997) Modelling the Feline Leukemia Virus (Fe and impact of Feline Leukemia Virus (FeLV) in populations of domestic cats. The model was tested with data

Courchamp, Franck

378

From population control to AIDS: Conceptualising and critiquing the global crisis model  

Microsoft Academic Search

This essay takes as its point of departure comparative analyses of the population control movement and the global AIDS response. We argue that the responses to both rapid population growth and AIDS reflect a particular model for approaching development issues: the global crisis model. This model provides a framework in which development issues become classified as (1) global in scope,

Ellen E. Foley; Anne Hendrixson

2011-01-01

379

Validation of population-based disease simulation models: a review of concepts and methods  

Microsoft Academic Search

BACKGROUND: Computer simulation models are used increasingly to support public health research and policy, but questions about their quality persist. The purpose of this article is to review the principles and methods for validation of population-based disease simulation models. METHODS: We developed a comprehensive framework for validating population-based chronic disease simulation models and used this framework in a review of

Jacek A Kopec; Philippe Finès; Douglas G Manuel; David L Buckeridge; William M Flanagan; Jillian Oderkirk; Michal Abrahamowicz; Samuel Harper; Behnam Sharif; Anya Okhmatovskaia; Eric C Sayre; M Mushfiqur Rahman; Michael C Wolfson

2010-01-01

380

Using Spreadsheets To Model Population Growth, Competition and Predation in Nature.  

ERIC Educational Resources Information Center

Describes how to place mathematical equations modeling population growth into a spreadsheet that performs calculations quickly and easily. Suggests experiments that can be performed with the spreadsheets. (WRM)

Carter, Ashley J. R.

1999-01-01

381

Journal of Theoretical Biology 229 (2004) 559572 Population models of sperm-dependent parthenogenesis  

E-print Network

populations are reproductive parasites of the hermaphrodite sexual form. Our logistic models reveal two. The fish Poeciliopsis monacha- lucida likewise obtains an intrinsic growth advantage from reduced

Sluckin, Tim

382

Individual-based model of sympatric populations of brown and rainbow trout for instream flow assessment: model description and calibration  

Microsoft Academic Search

This paper describes an individual-based model of sympatric populations of brown and rainbow trout in a stream habitat. The model provides a tool for projecting flow and temperature effects on trout populations by linking the hydraulic component of the instream flow incremental methodology\\/physical habitat simulation system (IFIM\\/PHABSIM) to an individual-based population model. PHABSIM simulates the spatial distribution of depth and

W. Van Winkle; H. I. Jager; S. F. Railsback; B. D. Holcomb; T. K. Studley; J. E. Baldrige

1998-01-01

383

Exploring a Financial Product Model with a Two-Population Genetic Algorithm  

E-print Network

Exploring a Financial Product Model with a Two-Population Genetic Algorithm Steven O. Kimbrough two-population genetic algorithm (GA) has been remarkably successful in finding good, feasible for presenting this case study is that we wish to explore the effectiveness of the two- population genetic

Kimbrough, Steven Orla

384

Modeling survival at multi-population scales using mark-recapture data  

Microsoft Academic Search

The demography of vertebrate populations is governed in part by processes operating at large spatial scales that have synchronizing effects on demographic parameters over large geographic areas, and in part, by local processes that generate fluctuations that are independent across populations. We describe a statistical model for the analysis of individual monitoring data at the multi-population scale that allows us

V. GROSBOIS; M. P. HARRIS; T. ANKER-NILSSEN; R. H. MCCLEERY; D. N. SHAW; B. J. T. MORGAN

2009-01-01

385

Phytoplankton food quality determines time windows for successful zooplankton reproductive pulses.  

PubMed

Recruitment success at the early life stages is a critical process for zooplankton demography. Copepods often dominate the zooplankton in marine coastal zones and are prey of the majority of fish larvae. Hypotheses interpreting variations of copepod recruitment are based on the concepts of "naupliar predation," "nutritional deficiency," and "toxic effect" of diatom diets. Contradictory laboratory and field studies have reached opposite conclusions on the effects of diatoms on copepod reproductive success, blurring our view of marine food-web energy flow from diatoms to higher consumers by means of copepods. Here we report estimates of copepod feeding selectivity and reproduction in response to seasonally changing phytoplankton characteristics measured in a highly productive coastal upwelling area off the coast of central Chile. The variable phytoplankton diversity and changing food quality had a strong and highly significant impact on the feeding selectivity, reproduction, and larval survival of three indigenous copepod species. Seasonal changes in copepod feeding behavior were related to the alternating protozoan-diatom diets, mostly based on dinoflagellates and ciliates during winter and autumn (low highly unsaturated fatty acids [HUFA]/polyunsaturated fatty acids [PUFA] availability), but switched to a diet of centric and chain-forming diatoms (high HUFA/PUFA availability) during the spring/summer upwelling period. Ingestion of diatom cells induced a positive effect on egg production. However, a negative relationship was found between egg hatching success, naupliar survival, and diatom ingestion. Depending on the phytoplankton species, diets had different effects on copepod reproduction and recruitment. In consequence, it seems that the classical marine food web model does not apply to some coastal upwelling systems. PMID:17249223

Vargas, Cristian A; Escribano, Rubén; Poulet, Serge

2006-12-01

386

An empirical model for estimating annual consumption by freshwater fish populations  

USGS Publications Warehouse

Population consumption is an important process linking predator populations to their prey resources. Simple tools are needed to enable fisheries managers to estimate population consumption. We assembled 74 individual estimates of annual consumption by freshwater fish populations and their mean annual population size, 41 of which also included estimates of mean annual biomass. The data set included 14 freshwater fish species from 10 different bodies of water. From this data set we developed two simple linear regression models predicting annual population consumption. Log-transformed population size explained 94% of the variation in log-transformed annual population consumption. Log-transformed biomass explained 98% of the variation in log-transformed annual population consumption. We quantified the accuracy of our regressions and three alternative consumption models as the mean percent difference from observed (bioenergetics-derived) estimates in a test data set. Predictions from our population-size regression matched observed consumption estimates poorly (mean percent difference = 222%). Predictions from our biomass regression matched observed consumption reasonably well (mean percent difference = 24%). The biomass regression was superior to an alternative model, similar in complexity, and comparable to two alternative models that were more complex and difficult to apply. Our biomass regression model, log10(consumption) = 0.5442 + 0.9962??log10(biomass), will be a useful tool for fishery managers, enabling them to make reasonably accurate annual population consumption predictions from mean annual biomass estimates. ?? Copyright by the American Fisheries Society 2005.

Liao, H.; Pierce, C. L.; Larscheid, J. G.

2005-01-01

387

ERRATUM ON `POPULATION GENETICS MODELS WITH SKEWED FERTILITIES: A FORWARD AND  

E-print Network

process models and compound Poisson models. Conditional branching process models are population modelsN , which is wrong in that generality. It is clarified for which compound Poisson models this for- mula holds true. It turns out that the only compound Poisson models for which this formula holds true

Boyer, Edmond

388

[Simulation of the distribution of spinocerebellar ataxia type I in Yakut populations: description of the model].  

PubMed

A simulation model has been developed for predicting the distribution of trinucleotide repeat expansion diseases in human populations. The interface of the software used to run this model presents the options for simulating natural reproduction of a population, with the population demographic parameters taken into account, and for simulating the appearance of a dynamic mutation in populations, transmission of the mutant gene from parents to offspring, and the effect of the phenotypic expression of the disease (the patients' life expectancy and birthrate) on the transmission of the mutant allele in the patients' families and its accumulation in the population. PMID:20391787

Koneva, L A; Konev, A V; Kucher, A N

2010-03-01

389

Dual-age-class population model to assess radiation dose effects on non-human biota populations.  

PubMed

In the present paper, a two-age-class group, logistic growth model for generic populations of non-human biota is described in order to assess non-stochastic effects of low linear energy-transfer radiation using three endpoints: repairable radiation damage, impairment of reproductive ability and, at higher radiation dose rates, mortality. This model represents mathematically the exchange between two life stages considering fecundity, growth and mortality. Radiation effects are modeled with a built-in self-recovery pool whereupon individuals can repair themselves. In acute effects mode, the repairing pool becomes depleted due to radiation and the model tends to lethality mode. A base calibration of the model's two free parameters is possible assuming that in acute mode 50% of the individuals die on 30 days when a radiation dose equal to the LD(50/30) is applied during that period. The model, which requires 10 species-dependent life-history parameters, was applied to fish and mammals. Its use in the derivation of dose-rate screening values for the protection of non-human biota from the effects of ionizing radiation is demonstrated through several applications. First, results of model testing with radiation effects data for fish populations from the EPIC project show the predictive capability of the model in a practical case. Secondly, the model was further verified with FREDERICA radiation effects data for mice and voles. Then, consolidated predictions for mouse, rabbit, dog and deer were generated for use in a population model comparison made within the IAEA EMRAS II project. Taken together, model predictions suggest that radiation effects are more harmful for larger organisms that generate lower numbers of offspring. For small mammal and fish populations, dose rates that are below 0.02 Gy day(-1) are not fatal; in contrast, for large mammals, chronic exposure at this level is predicted to be harmful. At low exposure rates similar to the ERICA screening dose rate of 2.4 × 10(-4) Gy day(-1), long-term effects on the survivability of populations are negligible, supporting the appropriateness of this value for radiological assessments to wildlife. PMID:22544082

Vives i Batlle, J

2012-08-01

390

A dynamic network population model with strategic link formation governed by individual preferences.  

PubMed

Historically most evolutionary models have considered infinite populations with no structure. Recently more realistic evolutionary models have been developed using evolutionary graph theory, which considered the evolution of structured populations. The structures involved in these populations are typically fixed, however, and real populations change their structure over both long and short time periods. In this paper we consider the dynamics of such a population structure. The timescales involved are sufficiently short that no individuals are born or die, but the links between individuals are in a constant state of flux, being actively governed by the preferences of the members of the population. The process is modelled using a Markov chain over the possible structures. We find that under the specified process the population evolves to a closed class of structures, and we show a method to find the stationary distribution on this class. We also consider some special cases of interest. PMID:23820036

Broom, Mark; Cannings, Chris

2013-10-21

391

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. PMID:20046854

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

2010-01-01

392

Zooplankton community analysis in the Changjiang River estuary by single-gene-targeted metagenomics  

NASA Astrophysics Data System (ADS)

DNA barcoding provides accurate identification of zooplankton species through all life stages. Single-gene-targeted metagenomic analysis based on DNA barcode databases can facilitate longterm monitoring of zooplankton communities. With the help of the available zooplankton databases, the zooplankton community of the Changjiang (Yangtze) River estuary was studied using a single-gene-targeted metagenomic method to estimate the species richness of this community. A total of 856 mitochondrial cytochrome oxidase subunit 1 (cox1) gene sequences were determined. The environmental barcodes were clustered into 70 molecular operational taxonomic units (MOTUs). Forty-two MOTUs matched barcoded marine organisms with more than 90% similarity and were assigned to either the species (similarity>96%) or genus level (similarity<96%). Sibling species could also be distinguished. Many species that were overlooked by morphological methods were identified by molecular methods, especially gelatinous zooplankton and merozooplankton that were likely sampled at different life history phases. Zooplankton community structures differed significantly among all of the samples. The MOTU spatial distributions were influenced by the ecological habits of the corresponding species. In conclusion, single-gene-targeted metagenomic analysis is a useful tool for zooplankton studies, with which specimens from all life history stages can be identified quickly and effectively with a comprehensive database.

Cheng, Fangping; Wang, Minxiao; Li, Chaolun; Sun, Song

2014-07-01

393

The distribution and vertical flux of fecal pellets from large zooplankton in Monterey bay and coastal California  

NASA Astrophysics Data System (ADS)

We sampled zooplankton and fecal pellets in the upper 200 m of Monterey Bay and nearby coastal regions in California, USA. On several occasions, we observed high concentrations of large pellets that appeared to be produced during night-time by dielly migrating euphausiids. High concentrations of pellets were found in near-surface waters only when euphausiids co-occurred with high concentrations of large (>10 ?m) phytoplankton. Peak concentrations of pellets at mid-depth (100 or 150 m) during the day were consistent with the calculated sinking speeds of pellets produced near the surface at night. At these high flux locations (HI group), pellet concentrations declined below mid-depth. In contrast, at locations where the phytoplankton assemblage was dominated by small phytoplankton cells (<10 ?m), pellet production and flux were low (LO group) whether or not euphausiid populations were high. Protozooplankton concentrations did not affect this pattern. We concluded that the day and night differences in pellet concentration and flux in the HI profiles were mostly due to sinking of dielly-pulsed inputs in the surface layer, and that small zooplankton (Oithona, Oncaea), heterotrophic dinoflagellates, and bacterial activity probably caused some pellet degradation or consumption below 100 m. We estimated that consumption of sinking pellets by large copepods was insignificant. High fluxes of pellets were episodic because they required both high concentrations of large phytoplankton and large stocks of euphausiids. Under these conditions, flux events overwhelmed retention mechanisms, resulting in large exports of organic matter from the upper 200 m.

Dagg, Michael J.; Jackson, George A.; Checkley, David M.

2014-12-01

394

Effects of climate change on an emperor penguin population: analysis of coupled demographic and climate models.  

PubMed

Sea ice conditions in the Antarctic affect the life cycle of the emperor penguin (Aptenodytes forsteri). We present a population projection for the emperor penguin population of Terre Adélie, Antarctica, by linking demographic models (stage-structured, seasonal, nonlinear, two-sex matrix population models) to sea ice forecasts from an ensemble of IPCC climate models. Based on maximum likelihood capture-mark-recapture analysis, we find that seasonal sea ice concentration anomalies (SICa ) affect adult survival and breeding success. Demographic models show that both deterministic and stochastic population growth rates are maximized at intermediate values of annual SICa , because neither the complete absence of sea ice, nor heavy and persistent sea ice, would provide satisfactory conditions for the emperor penguin. We show that under some conditions the stochastic growth rate is positively affected by the variance in SICa . We identify an ensemble of five general circulation climate models whose output closely matches the historical record of sea ice concentration in Terre Adélie. The output of this ensemble is used to produce stochastic forecasts of SICa , which in turn drive the population model. Uncertainty is included by incorporating multiple climate models and by a parametric bootstrap procedure that includes parameter uncertainty due to both model selection and estimation error. The median of these simulations predicts a decline of the Terre Adélie emperor penguin population of 81% by the year 2100. We find a 43% chance of an even greater decline, of 90% or more. The uncertainty in population projections reflects large differences among climate models in their forecasts of future sea ice conditions. One such model predicts population increases over much of the century, but overall, the ensemble of models predicts that population declines are far more likely than population increases. We conclude that climate change is a significant risk for the emperor penguin. Our analytical approach, in which demographic models are linked to IPCC climate models, is powerful and generally applicable to other species and systems. PMID:24501054

Jenouvrier, Stéphanie; Holland, Marika; Stroeve, Julienne; Barbraud, Christophe; Weimerskirch, Henri; Serreze, Mark; Caswell, Hal

2012-09-01

395

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

396

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. 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.

2013-01-01

397

Modeling the population dynamics of pacific yew. Forest Service research note  

SciTech Connect

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-growth forest stands. Diameter growth at breast height ranged from 0 to 3 centimeters per decade. The annual mortality rate for individuals greater than 5 centimeters in diameter at breast height was about 1 percent of the population. A matrix population model was constructed by using these and other fundamental data on yew population dynamics. The model was designed to perform population viability analyses of yew under various harvest regimes. Model projections suggested a slow rate of recovery from major disturbance.

Busing, R.T.; Spies, T.A.

1995-05-01

398

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

399

Applying the multivariate time-rescaling theorem to neural population models  

E-print Network

Statistical models of neural activity are integral to modern neuroscience. Recently interest has grown in modeling the spiking activity of populations of simultaneously recorded neurons to study the effects of correlations ...

Gerhard, Felipe

400

Modeling and responding to pandemic influenza : importance of population distributional attributes and non-pharmaceutical interventions  

E-print Network

After reviewing prevalent approaches to the modeling pandemic influenza transmission, we present a simple distributional model that captures the most significant population attributes that alter the dynamics of the outbreak. ...

Nigmatulina, Karima Robert

2009-01-01

401

Two populations and models of gamma ray bursts  

NASA Technical Reports Server (NTRS)

Gamma-ray burst statistics are best explained by a source population at cosmological distances, while spectroscopy and intensity histories of some individual bursts imply an origin on Galactic neutron stars. To resolve this inconsistency I suggest the presence of two populations, one at cosmological distances and the other Galactic. I build on ideas of Shemi and Piran (1990) and of Rees and Mesozaros (1992) involving the interaction of fireball debris with surrounding clouds to explain the observed intensity histories in bursts at cosmological distances. The distances to the Galactic population are undetermined because they are too few to affect the statistics of intensity and direction; I explain them as resulting from magnetic reconnection in neutron star magnetospheres. An appendix describes the late evolution of the debris as a relativistic blast wave.

Katz, J. I.

1993-01-01

402

Eco-Evo PVAs: Incorporating Eco-Evolutionary Processes into Population Viability Models  

EPA Science Inventory

We synthesize how advances in computational methods and population genomics can be combined within an Ecological-Evolutionary (Eco-Evo) PVA model. Eco-Evo PVA models are powerful new tools for understanding the influence of evolutionary processes on plant and animal population pe...

403

EUCLIDEAN SHIFT-TWIST SYMMETRY IN POPULATION MODELS OF SELF-ALIGNING OBJECTS  

E-print Network

EUCLIDEAN SHIFT-TWIST SYMMETRY IN POPULATION MODELS OF SELF-ALIGNING OBJECTS PAUL C. BRESSLOFF SIAM­1690 Abstract. We consider the symmetry properties of a general class of nonlocal population models describing words. cell alignment, actin cytoskeleton, animal aggregation, Euclidean symmetry, self- organization

Bressloff, Paul C

404

A MID-ATLANTIC AND A NATIONAL POPULATION MODEL OF NORTHERN BOBWHITE DEMOGRAPHIC SENSITIVITY  

E-print Network

bobwhites (Colinus virginianus), but a synthetic population model based on life-stage simulation analysis bobwhite demographic sensitivity. Proceedings of the National Quail Symposium 7:163­172. Key words: Colinus virginianus, fecundity, life-stage simulation analysis, New Jersey, northern bobwhite, population model

Sandercock, Brett K.

405

Stochastic model for population migration and the growth of human settlements during the Neolithic transition  

E-print Network

Stochastic model for population migration and the growth of human settlements during the Neolithic; published 12 August 2008 We present a stochastic two-population model that describes the migration transition. The main idea is that random migration and transition from a sedentary to a foraging way of life

Fedotov, Sergei

406

A PROBABILISTIC POPULATION EXPOSURE MODEL FOR PM10 AND PM 2.5  

EPA Science Inventory

A first generation probabilistic population exposure model for Particulate Matter (PM), specifically for predicting PM10, and PM2.5, exposures of an urban, population has been developed. This model is intended to be used to predict exposure (magnitude, frequency, and duration) ...

407

A PARTIAL DIFFERENTIAL EQUATION MODEL OF FISH POPULATION DYNAMICS AND ITS APPLICATION IN IMPINGEMENT IMPACT ANALYSIS  

EPA Science Inventory

The report gives results of a study to: (1) develop a mathematical model describing fish populations as a function of life process dynamics and facilities that impose additional mortality on fish populations; and (2) improve objective impingement impact prediction. The model acco...

408

A temperature-driven daily process model for onion thrips populations in onions  

Microsoft Academic Search

A temperature-driven process model was developed to describe the seasonal patterns of populations of onion thrips, Thrips tabaci Lindeman, in onion crops. The model used daily cohorts (individuals of the same developmental stage and daily age) as the population unit. After each day, individuals in a daily cohort either move to the next daily cohort in the same developmental stage,

M. Stevens; D. L. Liu

409

THE INFLUENCE OF MODEL TIME STEP ON THE RELATIVE SENSITIVIY OF POPULATION GROWTH RATE TO REPRODUCTION  

EPA Science Inventory

In recent years there has been an increasing interest in using population models in environmental assessments. Matrix population models represent a valuable tool for extrapolating from life stage-specific stressor effects on survival and reproduction to effects on finite populati...

410

A model of the trapped electron population for solar minimum  

NASA Technical Reports Server (NTRS)

A model is presented of the trapped electron environment of solar minimum conditions. Solar maximum models have been presented for the inner radiation zone (AE-5 1967), and for the outer radiation zone (AE-4 1967). The present solar minimum model consists of an inner zone model (AE-5 1975 Projected) with an epoch of 1975, and an outer zone model with an epoch of 1964. With only minor modifications this latter model is identical to the AE-4 1964 model presented previous. The model, however, has not previously been issued in computer form. AE-4 1964 is based upon satellite data, while the inner zone solar minimum model AE-5 1975 Projected consists entirely of extrapolations from AE-5 1967. While the two components of the solar minimum model have epochs 11 years part, it is assumed that any differences between the successive solar minima are smaller than the model error, and the complete model is associated with an epoch of 1975.

Teague, M. J.; Vette, J. I.

1974-01-01

411

F-IF A-SSE Modeling London's Population  

NSDL National Science Digital Library

This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: The table below shows historical estimates for the population of London. Year18011821 18411861 18811901 1921 1939 1961 London population 1,100,000 1,60...

412

Application of population growth models based on cumulative size to pecan aphids  

Microsoft Academic Search

Models for aphid population growth based on cumulative (past) population size have been developed with both a deterministic\\u000a formulation and a stochastic formulation. This article applies these mechanistic models to analyze a large dataset on pecan\\u000a aphid. The models yield symmetric and right-skewed curves, which differ qualitatively from the observed data which tend to\\u000a be left-skewed. Nevertheless this model-based analysis

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

2006-01-01

413

Importance of Arctic zooplankton seasonal migrations for ?-hexachlorocyclohexane bioaccumulation dynamics.  

PubMed

Like most zooplankton, Calanus hyperboreus undergoes seasonal migration spending late spring and summer grazing at the surface and the rest of the year in diapause at depth. As a result, in the Arctic Ocean this copepod resides for part of the year in the hexachlorocyclohexane (HCH) enriched surface water and for part of the year at depth where HCH undergoes significant microbial degradation resulting in far lower concentrations (~3 times for ?-HCH). We collected C. hyperboreus from summer and winter from the Amundsen Gulf and measured their ?-HCH concentrations, enantiomeric compositions, and bioaccumulation factors (BAFs) to investigate how this copepod responds to the change in exposure to ?-HCH. C. hyperboreus collected in winter were also cultured for 5 weeks under surface water conditions without feeding to investigate bioconcentration dynamics following spring ascent. Concentration of ?-HCH was 2-3 times higher in individuals from the summer than those from the winter. Log BAF from the summer (feeding period) does not exceed log BCF (bioconcentration factor) from the culturing experiment (no feeding) suggesting that ?-HCH concentration in C. hyperboreus is maintained through equilibration rather than feeding. After the spring ascent from deep waters, C. hyperboreus approach equilibrium partitioning with the higher surface water concentrations of ?-HCH within 3-4 weeks with about 60% of bioconcentration taking place in the first week. The C. hyperboreus ?-HCH chiral signature also reflects ambient seawater and can therefore be used as a determinant of residence depth. Even though a single cycle of seasonal migration does not result in a significant redistribution of ?-HCH in the water column, this process could have a significant cumulative effect over longer time scales with particular local importance where the zooplankton biomass is high and the ocean depth is great enough to provide substantial vertical concentration gradients. PMID:23570325

Pu?ko, Monika; Walkusz, W; Macdonald, R W; Barber, D G; Fuchs, C; Stern, G A

2013-05-01

414

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

415

Quantifying Inter- and Intra-Population Niche Variability Using Hierarchical Bayesian Stable Isotope Mixing Models  

PubMed Central

Variability in resource use defines the width of a trophic niche occupied by a population. Intra-population variability in resource use may occur across hierarchical levels of population structure from individuals to subpopulations. Understanding how levels of population organization contribute to population niche width is critical to ecology and evolution. Here we describe a hierarchical stable isotope mixing model that can simultaneously estimate both the prey composition of a consumer diet and the diet variability among individuals and across levels of population organization. By explicitly estimating variance components for multiple scales, the model can deconstruct the niche width of a consumer population into relevant levels of population structure. We apply this new approach to stable isotope data from a population of gray wolves from coastal British Columbia, and show support for extensive intra-population niche variability among individuals, social groups, and geographically isolated subpopulations. The analytic method we describe improves mixing models by accounting for diet variability, and improves isotope niche width analysis by quantitatively assessing the contribution of levels of organization to the niche width of a population. PMID:19587790

Moore, Jonathan W.; Darimont, Chris T.

2009-01-01

416

Modeling ruffed grouse populations in the central and southern Appalachians  

Microsoft Academic Search

From 1995–2002, the Appalachian Cooperative Grouse Research Project conducted a radiotelemetry study of ruffed grouse ( Bonasa umbellus) on 7 study areas in 5 states—Pennsylvania, Maryland, West Virginia, Virginia, and North Carolina. Based on this data, grouse populations were declining on all sites. However, declines were steeper than trends based on either Breeding Bird Survey or Christmas Bird Count data.

John Michael Tirpak

2005-01-01

417

The evolutionary limit for models of populations interacting competitively via  

E-print Network

in the limit of strong selection and small mutations. We prove that the population density converges to a sum to mutation and selection driven by competition for resources. Each individual in the popu- lation Cedex 02, France, E-mail: jabin@unice.fr 1 #12;the size of individuals, their age at maturity

Champagnat, Nicolas - Institut de Mathématiques �lie Cartan, Université Henri Poincaré

418

The evolutionary limit for models of populations interacting competitively with  

E-print Network

selection and small mutations. We prove that the population density converges to a sum of Dirac masses to mutation and selection driven by competition for resources. Each individual in the popu- lation Cedex 02, France, E-mail: jabin@unice.fr 1 #12;the size of individuals, their age at maturity

Jabin, Pierre-Emmanuel

419

TOXICANT-INDUCED MORTALITY IN MODELS OF DAPHNIA POPULATIONS  

EPA Science Inventory

A method to determine the mortality effects of a hydrophobic chemical on a population is proposed. he ecotoxicological protocol is based on individual organism response and is derived from the static theory of "survival of the fattest." his study, focusing on effects of mortality...

420

Improving Bayesian population dynamics inference: a coalescent-based model for multiple loci.  

PubMed

Effective population size is fundamental in population genetics and characterizes genetic diversity. To infer past population dynamics from molecular sequence data, coalescent-based models have been developed for Bayesian nonparametric estimation of effective population size over time. Among the most successful is a Gaussian Markov random field (GMRF) model for a single gene locus. Here, we present a generalization of the GMRF model that allows for the analysis of multilocus sequence data. Using simulated data, we demonstrate the improved performance of our method to recover true population trajectories and the time to the most recent common ancestor (TMRCA). We analyze a multilocus alignment of HIV-1 CRF02_AG gene sequences sampled from Cameroon. Our results are consistent with HIV prevalence data and uncover some aspects of the population history that go undetected in Bayesian parametric estimation. Finally, we recover an older and more reconcilable TMRCA for a classic ancient DNA data set. PMID:23180580

Gill, Mandev S; Lemey, Philippe; Faria, Nuno R; Rambaut, Andrew; Shapiro, Beth; Suchard, Marc A

2013-03-01

421

Modelling the Dynamics of Feral Alfalfa Populations and Its Management Implications  

PubMed Central

Background Feral populations of cultivated crops can pose challenges to novel trait confinement within agricultural landscapes. Simulation models can be helpful in investigating the underlying dynamics of feral populations and determining suitable management options. Methodology/Principal Findings We developed a stage-structured matrix population model for roadside feral alfalfa populations occurring in southern Manitoba, Canada. The model accounted for the existence of density-dependence and recruitment subsidy in feral populations. We used the model to investigate the long-term dynamics of feral alfalfa populations, and to evaluate the effectiveness of simulated management strategies such as herbicide application and mowing in controlling feral alfalfa. Results suggest that alfalfa populations occurring in roadside habitats can be persistent and less likely to go extinct under current roadverge management scenarios. Management attempts focused on controlling adult plants alone can be counterproductive due to the presence of density-dependent effects. Targeted herbicide application, which can achieve complete control of seedlings, rosettes and established plants, will be an effective strategy, but the seedbank population may contribute to new recruits. In regions where roadside mowing is regularly practiced, devising a timely mowing strategy (early- to mid-August for southern Manitoba), one that can totally prevent seed production, will be a feasible option for managing feral alfalfa populations. Conclusions/Significance Feral alfalfa populations can be persistent in roadside habitats. Timely mowing or regular targeted herbicide application will be effective in managing feral alfalfa populations and limit feral-population-mediated gene flow in alfalfa. However, in the context of novel trait confinement, the extent to which feral alfalfa populations need to be managed will be dictated by the tolerance levels established by specific production systems for specific traits. The modelling framework outlined in this paper could be applied to other perennial herbaceous plants with similar life-history characteristics. PMID:22768079

Bagavathiannan, Muthukumar V.; Begg, Graham S.; Gulden, Robert H.; Van Acker, Rene C.

2012-01-01

422

Biomass Atlas of Net Zooplankton in the Northeastern Pacific Ocean, 1956-1964.  

National Technical Information Service (NTIS)

The collection of zooplankton samples in the northeast Pacific Ocean was carried out as during oceanographic and exploratory fishing surveys. Samples were collected from vertical hauls and horizontal tows with a NORPAC net; other samples were collected wi...

R. J. LeBrasseur

1965-01-01

423

Community Structure and Standing Stock of Epibenthic Zooplankton at Five Sites in Grays Harbor, Washington.  

National Technical Information Service (NTIS)

Using a suction pump, epibenthic zooplankton community structures and standing stock were measured in shallow sublittoral and middle littoral habitats at Cow Point, Moon Island, the Marsh Establishment Site, and Stearn's Bluff, and the lower littoral habi...

J. R. Cordell, C. A. Simenstad

1981-01-01

424

Distribution, patchiness, and behavior of Antarctic zooplankton, assessed using multi-frequency acoustic techniques  

E-print Network

The physical and biological forces that drive zooplankton distribution and patchiness in an antarctic continental shelf region were examined, with particular emphasis on the Antarctic krill, Euphausia superba. This was ...

Lawson, Gareth L

2006-01-01

425

A New Model of the Near-Earth-Object Population  

NASA Astrophysics Data System (ADS)

We construct a new near-Earth-object (NEO) model which describes the debiased orbit and absolute-magnitude distributions of these objects. The model is developed using the same basic approach as the so-called Bottke model [1]. We anticipate that the new model, planned to be finished by mid-2013, will be a substantial improvement over the decade-old Bottke model, because we use more realistic NEO source regions, more accurate orbital integrations, improved estimations of the observational bias, and about 40 times more known NEOs to calibrate the model.

Granvik, M.; Morbidelli, A.; Jedicke, R.; Bolin, B.; Bottke, W. F.; Beshore, E.; Vokrouhlicky, D.; Nesvorny, D.; Michel, P.; Tsiganis, K.

2013-09-01

426

Dissolved and fecal pellet carbon and nitrogen release by zooplankton in tropical waters  

NASA Astrophysics Data System (ADS)

Carbon (C) and nitrogen (N) release by tropical zooplankton (mostly copepods) and micronekton (euphausiids, pelagic red crabs, and salps) was investigated near VERTEX particle traps at 18°N, 108°W (in 1981) and 15°40'N, 107°30'W (in 1982). The objective was to assess the significance of fecal pellet release relative to respiratory and dissolved excretory release of C and N and relative to primary production in the same waters. For small (< 300 ?m) and large (300 to 500 ?m) zooplankton, 38 to 49% more ammonium-nitrogen was excreted than C was respired, relative to body concentrations of N and C, respectively. However, for the same zooplankton, 40 to 54% less fecal N was egested than fecal C, again relative to body C and N contents. This apparent compensation yielded a relatively constant body C:N ratio, and, because of the relatively low ratio of respiratory C to excretory N, implied a protein-based metabolism. The same compensatory relationships were found for euphausiids and red crabs, except the percentages of C and N losses were lower than for the zooplankton. No such compensatory relationship was found for the salps, using respiratory—excretory data from the literature and our own observations of fecal pellet production. Either the literature data were not applicable to our salps, or the salps had a more lipid-based metabolism. Reasonably balanced C and N loss budgets were computed for the small and large zooplankton. Daily fecal pellet C egestion represented only 2 to 3% of both large and small zooplankton body C content, and daily fecal pellet N egestion was <2% of zooplankton body N. Likewise, daily fecal pellet production by small and large zooplankton together accounted for <2% of the daily primary C and N production in the top 100 m of water; that is, 'new' primary production would have had to replace losses of <2% per day to balance fecal pellet losses from large and small zooplankton, presuming all fecal pellets sank below 100 m without being eaten or remineralized. However, the estimate of total C flux through 120 m (from particle trap data) was only 4.4% of primary production, so the fecal pellet flux from small and large zooplankton could have accounted for up to 41% of the total flux. From corollary data, it was estimated that the total vertical C flux could result almost entirely from combined fecal pellet production by the existing zooplankton and micronekton concentrations. The vast majority of the primary C production (95.6%) was supported by respired and dissolved excreted compounds plus any atmospheric inputs.

Small, Lawrence F.; Fowler, Scott W.; Moore, Stanley A.; LaRosa, Jacques

1983-12-01

427

Modeling tradeoffs in avian life history traits and consequences for population growth  

USGS Publications Warehouse

Variation in population dynamics is inherently related to life history characteristics of species, which vary markedly even within phylogenetic groups such as passerine birds. We computed the finite rate of population change (??) from a matrix projection model and from mark-recapture observations for 23 bird species breeding in northern Arizona. We used sensitivity analyses and a simulation model to separate contributions of different life history traits to population growth rate. In particular we focused on contrasting effects of components of reproduction (nest success, clutch size, number of clutches, and juvenile survival) versus adult survival on ??. We explored how changes in nest success or adult survival coupled to costs in other life history parameters affected ?? over a life history gradient provided by our 23 Arizona species, as well as a broader sample of 121 North American passerine species. We further examined these effects for more than 200 passeriform and piciform populations breeding across North America. Model simulations indicate nest success and juvenile survival exert the largest effects on population growth in species with moderate to high reproductive output, whereas adult survival contributed more to population growth in long-lived species. Our simulations suggest that monitoring breeding success in populations across a broad geographic area provides an important index for identifying neotropical migratory populations at risk of serious population declines and a potential method for identifying large-scale mechanisms regulating population dynamics. ?? 2007 Elsevier B.V. All rights reserved.

Clark, M.E.; Martin, T.E.

2007-01-01

428

Analysis and Management of Animal Populations: Modeling, Estimation and Decision Making  

USGS Publications Warehouse

This book deals with the processes involved in making informed decisions about the management of animal populations. It covers the modeling of population responses to management actions, the estimation of quantities needed in the modeling effort, and the application of these estimates and models to the development of sound management decisions. The book synthesizes and integrates in a single volume the methods associated with these themes, as they apply to ecological assessment and conservation of animal populations. KEY FEATURES * Integrates population modeling, parameter estimation and * decision-theoretic approaches to management in a single, cohesive framework * Provides authoritative, state-of-the-art descriptions of quantitative * approaches to modeling, estimation and decision-making * Emphasizes the role of mathematical modeling in the conduct of science * and management * Utilizes a unifying biological context, consistent mathematical notation, * and numerous biological examples

Williams, B.K.; Nichols, J.D.; Conroy, M.J.

2002-01-01

429

Stable isotope analysis of the origins of zooplankton carbon in lakes of differing trophic state  

Microsoft Academic Search

Carbon stable isotope analysis was carried out on zooplankton from 24 United Kingdom lakes to examine the hypothesis that\\u000a zooplankton dependence on allochthonous sources of organic carbon declines with increasing lake trophy. Stable isotope analysis\\u000a was also carried out on particulate and dissolved organic matter (POM and DOM) and, in 11 of the lakes, of phytoplankton isolates.\\u000a In 21 of

Jonathan Grey; Roger I. Jones; Darren Sleep

2000-01-01

430

Long-term, predation-based control of a central-west North Sea zooplankton community  

Microsoft Academic Search

Long-term monitoring of the zooplankton community at a station 5.5 miles from the English coast in the central-west North Sea has been performed since 1968. Analyses of these data have revealed an inverse relationship between annual total zooplankton abundance and the position of the Gulf Stream North Wall (GSNW). This long-term relationship is opposite to the long-term positive association observed

Robin A. Clark; Chris L. J. Frid; Kirsty R. Nicholas

2003-01-01

431

Phytoplankton control by grazing zooplankton: A study on the spring clear-water phase  

Microsoft Academic Search

We tested the hypothesis that a clear-water period, regularly observed in many meso- and eutrophic lakes, is caused by grazing herbivorous zooplankton. Such a clear-water phase occurs during mid-May in the moderately eutrophic Schiihsee and involves a rapid increase in Secchi transparency, and a drop in chlorophyll and particulate organic carbon in size fractions ~35 Nm. Maxima of zooplankton biomass

WINFRIED LAMPERT; WALTER FLECKNER; HAKUMAT RAI; BARBARA E. TAYLOR

1986-01-01

432

Biochemical composition of zooplankton from Visakhapatnam harbour waters, east coast of India  

Microsoft Academic Search

Proximate composition, zooplankton biomass, protein, lipid, carbohydrate, organic carbon and calorific content of mixed zooplankton in the Visakhapatnam harbour waters were estimated. Biomass varied from 15.2 to 74.0 ml.100 m-3 ( x =31.05 ±17.7) in the outer harbour and 10 to 64.0 ml.100 m-3 ( x =26.30±14.8) in the inner harbour. Copepods, tintin- nids, decapods and chaetognaths formed dominant groups

I. Nageswara Rao; R. Ratna Kumari

2002-01-01

433

A comparison of zooplankton communities in saline lakewater with variable anion composition  

Microsoft Academic Search

Although salinity and aquatic biodiversity are inversely related in lake water, the relationship between types of salts and zooplankton communities is poorly understood. In this study, zooplankton species were related to environmental variables from 12 lakes: three saline lakes with water where the dominant anions were SO4 and CO3, four saline lakes with Cl-dominated water, and five dilute, subsaline (0.5–3

A. M. Derry; E. E. Prepas; P. D. N. Hebert

2003-01-01

434

Influence of hydrophyte abundance on the spatial distribution of zooplankton in selected lakes in Greece  

Microsoft Academic Search

Submerged hydrophyte vegetation consists of a highly important biotic component of maintaining lake ecosystems towards a “clear\\u000a water” ecological status. Aquatic macrophytes are well known to play a significant multidimensional role in lakes by competing\\u000a with phytoplankton growth, stabilising sediment and offering refuge to fishes, macro-invertebrates and littoral zooplankton,\\u000a amongst others. Zooplanktons that are associated with macrophyte beds, in particular,

K. Stefanidis; E. Papastergiadou

2010-01-01

435

MULTIPLE STRESSOR EFFECTS OF HERBICIDE, PH, AND FOOD ON WETLAND ZOOPLANKTON AND A LARVAL AMPHIBIAN  

PubMed Central

Interactions of herbicides and natural environmental stressors such as pH and food availability are poorly understood. We tested a chemical formulation of triclopyr (Release®) at environmentally relevant test concentrations (0.25 and 0.50 mg/L) in combination with two levels of pH (pH 5.5 and 7.5), and two levels of food availability (high and low). Population level effects of each stressor alone and in combination with the others were investigated using Simocephalus vetulus, a zooplankton species, and Rana pipiens tadpoles (Gosner stage 25), both common to forest ponds and wetlands. Herbicide treatments resulted in significant decreases in survival of both test species as well as reproduction and development time for Simocephalus vetulus at levels 5–10× below predicted worst case environmental concentrations (2.6 mg/L). This laboratory study demonstrates a probable risk of toxic effects of Release® herbicide which may be significantly increased by low food availability and by low pH at environmentally relevant concentrations. PMID:17904219

Chen, Celia Y.; Hathaway, Kevin M.; Thompson, Dean G.; Folt, Carol L.

2011-01-01

436

Population size models based on cumulative size, with application to aphids  

Microsoft Academic Search

This paper investigates the use of a mechanistic model for describing the size of local aphid populations, specifically of the pecan aphid (Monellia caryella) and of the mustard aphid (Lipaphis erysimi). The mechanistic equation, like the logistic growth model, has parameters for a birth rate and a death rate, however the present mechanistic model generalizes the logistic growth model by

James H. Matis; Thomas R. Kiffe; Timothy I. Matis; John A. Jackman; Harvir Singh

2007-01-01

437

Importance of light, temperature, zooplankton and fish in predicting the nighttime vertical distribution of Mysis diluviana  

USGS Publications Warehouse

The opossum shrimp Mysis diluviana (formerly M. relicta) performs large amplitude diel vertical migrations in Lake Ontario and its nighttime distribution is influenced by temperature, light and the distribution of its predators and prey. At one location in southeastern Lake Ontario, we measured the vertical distribution of mysids, mysid predators (i.e. planktivorous fishes) and mysid prey (i.e. zooplankton), in addition to light and temperature, on 8 occasions from May to September, 2004 and 2005. We use these data to test 3 different predictive models of mysid habitat selection, based on: (1) laboratory-derived responses of mysids to different light and temperature gradients in the absence of predator or prey cues; (2) growth rate of mysids, as estimated with a mysid bioenergetics model, given known prey densities and temperatures at different depths in the water column; (3) ratio of growth rates (g) and mortality risk (??) associated with the distribution of predatory fishes. The model based on light and temperature preferences was a better predictor of mysid vertical distribution than the models based on growth rate and g:?? on all 8 occasions. Although mysid temperature and light preferences probably evolved as mechanisms to reduce predation while increasing foraging intake, the response to temperature and light alone predicts mysid vertical distribution across seasons in Lake Ontario. ?? Inter-Research 2009.

Boscarino, B. T.; Rusdtam, L. G.; Eillenberger, J. L.; O'Gorman, R.

2009-01-01

438

A population model for the black tern Chlidonias niger in West-Europe  

Microsoft Academic Search

Based on empiric data of breeding success and accurate number trends in The Netherlands, a population model for the black\\u000a tern was constructed. This model is based on Leslie matrices. Reproductive parameters from the four most important landscape\\u000a types (river landscape, agricultural grasslands, peat marsh and heath land\\/moors) are used as model input. Highly accurate\\u000a national population trend data were

Jan van der Winden; Peter W. van Horssen

2008-01-01

439

Responses of Phyto- and Zooplankton Communities to Prymnesium polylepis (Prymnesiales) Bloom in the Baltic Sea  

PubMed Central

A large bloom of Prymnesium polylepis occurred in the Baltic Sea during the winter 2007 – spring 2008. Based on numerous reports of strong allelopathic effects on phytoplankton exerted by P. polylepis and its toxicity to grazers, we hypothesized that during this period negative correlations will be observed between P. polylepis and (1) main phytoplankton groups contributing to the spring bloom (i.e., diatoms and dinoflagellates), and (2) zooplankton growth and abundance. To test these hypotheses, we analyzed inter-annual variability in phytoplankton and zooplankton dynamics as well as growth indices (RNA?DNA ratio) in dominant zooplankton in relation to the Prymnesium abundance and biomass. Contrary to the hypothesized relationships, no measurable negative responses to P. polylepis were observed for either the total phytoplankton stocks or the zooplankton community. The only negative response, possibly associated with P. polylepis occurrence, was significantly lower abundance of dinoflagellates both during and after the bloom in 2008. Moreover, contrary to the expected negative effects, there were significantly higher total phytoplankton abundance as well as significantly higher winter abundance and winter-spring RNA?DNA ratio in dominant zooplankton species in 2008, indicating that P. polylepis bloom coincided with favourable feeding conditions for zooplankton. Thus, primary consumers, and consequently also zooplanktivores (e.g., larval fish and mysids), may benefit from haptophyte blooms, particularly in winter, when phytoplankton is scarce. PMID:25393031

Gorokhova, Elena; Hajdu, Susanna; Larsson, Ulf

2014-01-01

440

Microcystin production by Microcystis aeruginosa exposed to different stages of herbivorous zooplankton.  

PubMed

Microcystin (MC) production by four monoclonal Microcystis aeruginosa strains was evaluated in response to infochemicals (indirect exposure) released from different stages of herbivorous zooplankton (neonate/juvenile and adult Daphnia magna and Moina macrocopa). The intracellular MC and extracellular MC concentrations were significantly different among the control and treatments with zooplankton culture media filtrates (p<0.05), and in most cases MC production was significantly higher (p<0.05) in strains exposed to infochemicals released from adult zooplankton rather than those of neonate/juvenile zooplankton in four strains of M. aeruginosa. Compared to intracellular MC (385.0-5598.6microg g(-1)DW), very low concentrations of extracellular MC (9.9-737.6microg ml(-1)) were released, but both showed similar temporal patterns over the course of the experiment. This result might be attributed to the fact that adult zooplankton produced more infochemical signals than equal numbers of smaller juveniles and neonates. It is the first study to provide evidence that MC production might be impacted by infochemicals released from different stages of zooplankton, mediated with physiological characteristics, body size, and feeding habits. PMID:18243271

Jang, Min-Ho; Ha, Kyong; Takamura, Noriko

2008-04-01

First Page Previous Page 1 2 3 4 5 6 7 8 9