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1

Lake acidification: Effects on crustacean zooplankton populations  

SciTech Connect

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

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

1993-08-01

2

Interactions between Predation and Resources Shape Zooplankton Population Dynamics  

PubMed Central

Identifying the relative importance of predation and resources in population dynamics has a long tradition in ecology, while interactions between them have been studied less intensively. In order to disentangle the effects of predation by juvenile fish, algal resource availability and their interactive effects on zooplankton population dynamics, we conducted an enclosure experiment where zooplankton were exposed to a gradient of predation of roach (Rutilus rutilus) at different algal concentrations. We show that zooplankton populations collapse under high predation pressure irrespective of resource availability, confirming that juvenile fish are able to severely reduce zooplankton prey when occurring in high densities. At lower predation pressure, however, the effect of predation depended on algal resource availability since high algal resource supply buffered against predation. Hence, we suggest that interactions between mass-hatching of fish, and the strong fluctuations in algal resources in spring have the potential to regulate zooplankton population dynamics. In a broader perspective, increasing spring temperatures due to global warming will most likely affect the timing of these processes and have consequences for the spring and summer zooplankton dynamics. PMID:21304980

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

2011-01-01

3

Effects of alewife predation on zooplankton populations in Lake Michigan  

USGS Publications Warehouse

The zooplankton populations in southeastern Lake Michigan underwent striking, size-related changes between 1954 and 1966. Forms that decline sharply were the largest cladocerans (Leptodora kindtii, Daphnia galeata, and D. retrocurva), the largest calanoid copepods (Limnocalanus macrurus, Epischura lacustris, and Diaptomus sicilis), and the largest cyclopoid copepod (Mesocyclops edax). Two of these, D. galeata and M. edax (both abundant in 1954), became extremely rare. Certain medium-sized or small species increased in numbers: Daphnia longiremis, Holopedium gibberum, Polyphemus pediculus, Bosmina longirostris, Bosmina coregoni, Ceriodaphnia sp., Cyclops bicuspidatus, Cyclops vernalis, and Diaptomus ashlandi. Evidence is strong that the changes were due to selective predation by alewives. The alewife was uncommon in southeastern Lake Michigan in 1954 but had increased to enormous proportions by 1966; there was a massive dieoff in spring 1967, and abundance remained relatively low in 1968. The composition of zooplankton populations in 1968 generally had shifted back toward that of 1954, although D. galeata and M. edax remained rare. The average size, and size at onset of maturity, of D. retrocurva decreased noticeably between 1954 and 1966 but increased between 1966 and 1968.

Wells, LaRue

1970-01-01

4

BENEFICIAL USE IMPAIRMENT #13: DEGRADATION OF PHYTOPLANKTON AND ZOOPLANKTON POPULATIONS  

EPA Science Inventory

Pursuant to the Great Lakes Water Quality Agreement and Annex 2, the Detroit River possesses several impaired beneficial uses. Beneficial Use #13 addresses phyto- and zooplankton populatioins and whether or not they are degraded or impaired....

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

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

NASA Astrophysics Data System (ADS)

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

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

2007-11-01

7

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

SciTech Connect

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

Shuman, J.R.

1988-01-01

8

Modeling dynamic interactions and coherence between marine zooplankton and fishes linked to environmental variability  

NASA Astrophysics Data System (ADS)

The dynamics of marine fishes are closely related to lower trophic levels and the environment. Quantitatively understanding ecosystem dynamics linking environmental variability and prey resources to exploited fishes is crucial for ecosystem-based management of marine living resources. However, standard statistical models typically grounded in the concept of linear system may fail to capture the complexity of ecological processes. We have attempted to model ecosystem dynamics using a flexible, nonparametric class of nonlinear forecasting models. We analyzed annual time series of four environmental indices, 22 marine copepod taxa, and four ecologically and commercially important fish species during 1977 to 2009 on Georges Bank, a highly productive and intensively studied area of the northeast U.S. continental shelf ecosystem. We examined the underlying dynamic features of environmental indices and copepods, quantified the dynamic interactions and coherence with fishes, and explored the potential control mechanisms of ecosystem dynamics from a nonlinear perspective. We found: (1) the dynamics of marine copepods and environmental indices exhibiting clear nonlinearity; (2) little evidence of complex dynamics across taxonomic levels of copepods; (3) strong dynamic interactions and coherence between copepods and fishes; and (4) the bottom-up forcing of fishes and top-down control of copepods coexisting as target trophic levels vary. These findings highlight the nonlinear interactions among ecosystem components and the importance of marine zooplankton to fish populations which point to two forcing mechanisms likely interactively regulating the ecosystem dynamics on Georges Bank under a changing environment.

Liu, Hui; Fogarty, Michael J.; Hare, Jonathan A.; Hsieh, Chih-hao; Glaser, Sarah M.; Ye, Hao; Deyle, Ethan; Sugihara, George

2014-03-01

9

Three-dimensional modeling of acoustic backscattering from fluid-like zooplankton  

Microsoft Academic Search

Scattering models that correctly incorporate organism size and shape are a critical component for the remote detection and classification of many marine organisms. In this work, an acoustic scattering model has been developed for fluid-like zooplankton that is based on the distorted wave Born approximation (DWBA) and that makes use of high-resolution three-dimensional measurements of the animal's outer boundary shape.

Andone C. Lavery; Timothy K. Stanton; Duncan E. McGehee; Dezhang Chu

2002-01-01

10

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

11

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

12

Culture optimization for the emergent zooplanktonic model organism Oikopleura dioica  

PubMed Central

The pan-global marine appendicularian, Oikopleura dioica, shows considerable promise as a candidate model organism for cross-disciplinary research ranging from chordate genetics and evolution to molecular ecology research. This urochordate, has a simplified anatomical organization, remains transparent throughout an exceptionally short life cycle of less than 1 week and exhibits high fecundity. At 70 Mb, the compact, sequenced genome ranks among the smallest known metazoan genomes, with both gene regulatory and intronic regions highly reduced in size. The organism occupies an important trophic role in marine ecosystems and is a significant contributor to global vertical carbon flux. Among the short list of bona fide biological model organisms, all share the property that they are amenable to long-term maintenance in laboratory cultures. Here, we tested diet regimes, spawn densities and dilutions and seawater treatment, leading to optimization of a detailed culture protocol that permits sustainable long-term maintenance of O. dioica, allowing continuous, uninterrupted production of source material for experimentation. The culture protocol can be quickly adapted in both coastal and inland laboratories and should promote rapid development of the many original research perspectives the animal offers. PMID:19461862

Bouquet, Jean-Marie; Spriet, Endy; Troedsson, Christofer; Otterå, Helen; Chourrout, Daniel; Thompson, Eric M.

2009-01-01

13

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

14

The effect of different zooplankton grazing patterns resulting from diel vertical migration on phytoplankton growth and composition: a laboratory experiment  

Microsoft Academic Search

Diel vertical migration (DVM) of herbivorous zooplankton is a widespread behavioural phenomenon in freshwater ecosystems. So far only little attention has been paid to the impact of DVM on the phytoplankton community in the epilimnion. Some theoretical models predict that algal population growth in the epilimnion should depend on the herbivores’ migration and grazing patterns: even if migrating zooplankton consume

Elke S. Reichwaldt; Isabelle D. Wolf; Herwig Stibor

2004-01-01

15

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

16

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

17

A modeling study to explore on-shelf transport of oceanic zooplankton in the Eastern Bering Sea  

NASA Astrophysics Data System (ADS)

The Eastern Bering Sea shelf is divided into distinct hydrographic domains by structural fronts. Despite frontal obstructions to cross-shelf transport, each year large oceanic copepods—primarily Neocalanus spp.—are known to dominate the biomass of the outer-shelf zooplankton communities, and in some years are advected into the middle-shelf domain. Using ROMS (the Regional Ocean Modeling System), coupled with a float tracking model designed to represent ontogenetic vertical migration behavior of Neocalanus, we explored the mechanisms, timing, and location of the transport of oceanic zooplankton onto the eastern Bering Sea shelf from overwintering sources along the Gulf of Alaska and Bering Sea shelf breaks, under a variety of environmental conditions. Our float tracking experiments suggest that the timing of on-shelf transport and the distribution of oceanic zooplankton on the shelf can vary substantially between one year and another. The Bering, Pribilof, and Zhemchug Canyons and Cape Navarin were all regions of elevated on-shelf float transport. Wind direction was the primary factor controlling inter-annual variability in the timing, amount, and location of the on-shelf transport of our Neocalanus floats. Float transport across the northern and southern shelves responded in opposite directions to inter-annual differences in wind forcing: southeasterly wind enhanced on-shelf transport of the Neocalanus floats along the southern shelf but suppressed on-shelf transport over the northern shelf. Conversely, northwesterly wind suppressed on-shelf zooplankton transport onto the southern shelf but promoted enhanced transport around Cape Navarin on the northern shelf. Transport of the Neocalanus floats onto the shelf can be very episodic, reflecting the short duration of winds that promote on-shelf transport. Relatively short (days to weeks) periods of southeasterly wind between March and April significantly impacted the number of floats transported onto the shelf. The relative importance of different source areas to supplying oceanic zooplankton to the Bering Sea shelf does not appear to vary much from year to year. Our model results suggest that the Neocalanus found on the southern shelf most likely originate from overwintering sites in the Alaska Stream or the Eastern Bering Sea shelf break south of the Pribilof Islands, while Neocalanus found on the northern shelf most likely originate from sites north of the Pribilof Islands.

Gibson, G. A.; Coyle, K. O.; Hedstrom, K.; Curchitser, E. N.

2013-07-01

18

Zooplankton intermittency and turbulence  

NASA Astrophysics Data System (ADS)

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

Schmitt, François G.

2010-05-01

19

High evolutionary potential of marine zooplankton  

PubMed Central

Abstract Open ocean zooplankton often have been viewed as slowly evolving species that have limited capacity to respond adaptively to changing ocean conditions. Hence, attention has focused on the ecological responses of zooplankton to current global change, including range shifts and changing phenology. Here, we argue that zooplankton also are well poised for evolutionary responses to global change. We present theoretical arguments that suggest plankton species may respond rapidly to selection on mildly beneficial mutations due to exceptionally large population size, and consider the circumstantial evidence that supports our inference that selection may be particularly important for these species. We also review all primary population genetic studies of open ocean zooplankton and show that genetic isolation can be achieved at the scale of gyre systems in open ocean habitats (100s to 1000s of km). Furthermore, population genetic structure often varies across planktonic taxa, and appears to be linked to the particular ecological requirements of the organism. In combination, these characteristics should facilitate adaptive evolution to distinct oceanographic habitats in the plankton. We conclude that marine zooplankton may be capable of rapid evolutionary as well as ecological responses to changing ocean conditions, and discuss the implications of this view. We further suggest two priority areas for future research to test our hypothesis of high evolutionary potential in open ocean zooplankton, which will require (1) assessing how pervasive selection is in driving population divergence and (2) rigorously quantifying the spatial and temporal scales of population differentiation in the open ocean. Recent attention has focused on the ecological responses of open ocean zooplankton to current global change, including range shifts and changing phenology. Here, we argue that marine zooplankton also are well poised for evolutionary responses to global change. PMID:24567838

Peijnenburg, Katja T C A; Goetze, Erica

2013-01-01

20

A multi-angle acoustic scattering apparatus for zooplankton and fish  

E-print Network

Use acoustics to survey marine animal populations. Empirical forward modeling for target strengthA multi-angle acoustic scattering apparatus for zooplankton and fish Paul L. D. Roberts AOS Seminar, and the application to in situ systems. Design of a multi-angle laboratory scattering system ­ Tank, acoustics

Jaffe, Jules

21

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

22

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.

23

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

24

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

25

The use of mechanistic descriptions of algal growth and zooplankton grazing in an estuarine eutrophication model  

Microsoft Academic Search

A simple model of estuarine eutrophication is built on biomechanical (or mechanistic) descriptions of a number of the key ecological processes in estuaries. Mechanistically described processes include the nutrient uptake and light capture of planktonic and benthic autotrophs, and the encounter rates of planktonic predators and prey. Other more complex processes, such as sediment biogeochemistry, detrital processes and phosphate dynamics,

M. e. Baird; S. j. Walker; B. b. Wallace; I. t. Webster; J. s. Parslow

2003-01-01

26

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.

27

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

28

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

29

Zooplankton of West Madagascar  

NASA Astrophysics Data System (ADS)

During six week survey (August - October 2009) in Western and Northern coast of Madagascar, the R/V 'Dr. Fridtjof Nansen' has carried out a study of the pelagic ecosystem. In collaboration with Agulhas & Somali Current Large Marine Ecosystems project (ASCLME) and South West Indian Ocean Fisheries Project (SWIOFP), the aim of the survey was to establish the physical, chemical and biological characteristics of the Western Madagascar shelf region as a whole. Zooplankton samples were collected with Hydrobios Multinet at all environmental stations ranging from 200 m depth to the surface. The Multinet was equipped with 5 nets for depth-stratified sampling. The nets were fitted with 180 µm mesh size and the water flow through the nets was measured. The Multinet was deployed and retrieved at a rate of ~ 1.5 m per second and was obliquely hauled. The five nets were triggered at the pre-selected depth intervals 0-25m, 25-50m, 50-80m, 80-120m and 120-200m. All samples were stored in marked bottles and preserved with buffered formaldehyde of 4% for further analysis. As results,the zooplankton abundance was influenced by physico-chemical factors. During the study period 34 Family of zooplankton were identified which are dominated by Copepoda (58,69%) followed by Radiolaria (12,06%), Appendicularia (6,47%), Sagitta (5,11%), Larvae (4,57%), Ostracoda (3,13%), pelagic Foraminifera (2,15%). Family of zooplankton with abundance <1% were also recorded, namely Salpidae (0,94%), Euphausiacea (0,44%), Tintinnidae (0,39%), Annélidae Polychètes (0,34%), Mysidacea (0,21%), Ptéropodae (0,13%). Highest number of zooplankton were found at the depth below the maximum of fluorescence during the day. Copepods distribution depends on site and depth. During this study, the number of identified species is always superior to 50 for all sampling sites. The findings of the present study will help to improve the scientific knowledge of the marine ecosystem of the west coast of Madagascar.

Bemiasa, John; Remanevy, Sitraka

2014-05-01

30

Communities and Populations Two models of population change  

E-print Network

-Volterra equations for oscillations in populations · Prisoner's dilemma ­ Single play ­ Iterated play ­ CommunityCommunities and Populations · Two models of population change ­ The logistic map ­ The Lotke-wide play #12;The Logistic Map Function (Robert May) · PopulationT+1=r(PopulationT)(1-Population

Indiana University

31

Modeling Population Growth and Extinction  

ERIC Educational Resources Information Center

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

Gordon, Sheldon P.

2009-01-01

32

Spatial and Temporal Variability of Zooplankton in a Great Plains Reservoir  

Microsoft Academic Search

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

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

2004-01-01

33

Fuzzy modelling in population dynamics  

Microsoft Academic Search

The aim of this paper is to analyze the behavior of models which describe the population dynamics taking into account the subjectivity in the state variables or in the parameters. The models in this work have demographic and environmental fuzziness. The environmental fuzziness is presented using a life expectancy model where the fuzziness of parameters is considered. The demographic fuzziness

L. C. Barros; R. C. Bassanezi; P. A. Tonelli

2000-01-01

34

Population Explosion: Modeling Phage Growth  

NSDL National Science Digital Library

How is the relationship between phages and their bacterial hosts like that of predators and prey? How does this relationship differ? What are the factors that contribute to phage production in the cell? What can the phage concentration in a high titer lysate tell us about both of these populations? We can investigate these questions and more with an Excel spreadsheet model for phage growth. * explore a multiple parameter model of population growth in bacteriophages that demonstrates interdependence with the population of bacterial hosts

Jean Douthwright (Beloit College; Biology)

2006-05-20

35

Terrorist population dynamics model.  

PubMed

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

Kaminskiy, Mark P; Ayyub, Bilal M

2006-06-01

36

Modeling the prehistoric Maori population.  

PubMed

Skeletal and comparative evidence of mortality is combined with fertility estimates for the precontact Maori population of New Zealand to determine the implied rate of precontact population growth. This rate is found to be too low to populate New Zealand within the time constraints of its prehistoric sequence, the probable founding population size, and the probable population size at contact. Rates of growth necessary to populate New Zealand within the accepted time span are calculated. The differences between this minimum necessary rate and the skeletally derived rate are too large to result solely from inadequacies in the primary data. Four alternative explanations of this conundrum are proposed: 1) skeletal evidence of precontact mortality is highly inaccurate; 2) skeletal evidence of fertility is severely underestimating actual levels; 3) there was very rapid population growth in the earliest part of the sequence up to 1150 A.D., from which no skeletal evidence currently is available; or 4) the prehistoric sequence of New Zealand may have been longer than the generally accepted 1,000-1,200 years. These alternatives are examined, and a combination of the last two is found to be the most probable. The implications of this model for New Zealand prehistory and Oceanic paleodemography are discussed. PMID:2183629

Brewis, A A; Molloy, M A; Sutton, D G

1990-03-01

37

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

PubMed

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

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

2011-01-01

38

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 ...

39

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

Microsoft Academic Search

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

Kirsten Work; Moshe Gophen

1999-01-01

40

An emerging paradigm in marine science is the elastic ability of gelatinous zooplankton to dominate in stressed  

E-print Network

2475 An emerging paradigm in marine science is the elastic ability of gelatinous zooplankton to dominate in stressed marine environments, and several studies have raised the possibility that gelatinous). Gelatinous zooplankton populations also appear to be increasing due to increased eutrophication resulting

Thuesen, Erik V.

41

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

42

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

43

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; Tamara, Ticktin; Valverde, Teresa; Weekley, Carl W.

2012-01-01

44

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; Tamara, Ticktin; Valverde, Teresa; Weekley, Carl W.

2012-01-01

45

Amerciamysis bahia Stochastic Matrix Population Model for Laboratory Populations  

EPA Science Inventory

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

46

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; Möllmann, Christian

2014-01-01

47

Habitat heterogeneity determines climate impact on zooplankton community structure and dynamics.  

PubMed

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; Möllmann, Christian

2014-01-01

48

[The population problem in global modeling].  

PubMed

Developments during the past 15 years in population modeling are critically reviewed. The author notes that while population variables were treated as endogenous in earlier models developed by the Club of Rome, later models have treated such variables as exogenous. The need to link demographic factors to structural changes and economic growth, in accordance with Marxist-Leninist population theory, is noted. (SUMMARY IN ENG AND RUS) PMID:12280533

Naidenova, P

1986-01-01

49

Uncertainty in spatially explicit population models  

Microsoft Academic Search

Spatially explicit population models (SEPMs) are often used in conservation planning. However, confidence intervals around predictions of spatially explicit population models can greatly underestimate model uncertainty. This is partly because some sources of uncertainty are not amenable to the classic methods of uncertainty analysis. Here, we present a method that can be used to include multiple sources of uncertainty into

E. S. Minor; R. I. McDonald; E. A. Treml; D. L. Urban

2008-01-01

50

Fitting probability models to population dynamics data  

Microsoft Academic Search

Methods for modeling population dynamics in probability using the generalized point process approach are developed. The life history of these populations is such that seasonal reproduction occurs during a short time. Several models are developed and analyzed. Data about two species: colonial spiders (Stegodyphus dumicola) and a migratory bird (wood thrush, Hylocichla mustelina) are used to estimate model parameters with

Yosef Cohen

2009-01-01

51

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

52

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

53

Introduction The zooplankton community occupies a central  

E-print Network

Introduction The zooplankton community occupies a central position in the pelagic food web of lakes of the lake. Such excessive predation on the grazing zooplankton can cause a "bot- tleneck" in the flow of energy through the lake food web resulting in a build up of undesirable phytoplankton, poten- tially

New Hampshire, University of

54

Caloric requirements of human populations: A model  

Microsoft Academic Search

Currently available models used for predicting human caloric requirements do not reflect the great variability in activity patterns observed among populations, and are insensitive to important anthropometric, demographic, and environmental variables. They are thus inadequate for application to many populations and problems of anthropological interest. We present a model for determining caloric requirements which more accurately accommodates the effects of

Paul W. Leslie; James R. Bindon; Paul T. Baker

1984-01-01

55

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

56

Hidden Process Models For Animal Population Dynamics  

Microsoft Academic Search

Hidden process models are a conceptually useful and practical way to si- multaneously 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,

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

2006-01-01

57

Robust population management under uncertainty for structured population models.  

PubMed

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

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

2007-12-01

58

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

59

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

60

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

61

"Trophic overyielding": phytoplankton diversity promotes zooplankton productivity.  

PubMed

Diversity-productivity relationships at the primary producer level have been extensively studied, especially for terrestrial systems. Here, we explore whether the diversity of aquatic primary producers (phytoplankton) has effects on higher trophic levels (zooplankton). We investigated the effect of phytoplankton diversity on an artificial zooplankton community in a laboratory experiment where phytoplankton biomass and elemental composition (carbon-to-phosphorus ratio) were kept constant. Phytoplankton diversity increased the means of both zooplankton growth rate and abundance while suppressing their variability, and sustained higher zooplankton diversity. Likely explanations include resource complementarity effects among phytoplankton species as food entities, as well as niche complementarity effects among Daphnia species as competitors. By affecting the productivity as well as the variability of the next trophic level, biodiversity of primary producers may have far-reaching consequences in aquatic food webs. PMID:23431601

Striebel, Maren; Singer, Gabriel; Stibor, Herwig; Andersen, Tom

2012-12-01

62

ORIGINAL PAPER Predation by zooplankton on Batrachochytrium  

E-print Network

ORIGINAL PAPER Predation by zooplankton on Batrachochytrium dendrobatidis: biological control Abstract Batrachochytrium dendrobatidis (hereafter Batrachochytrium), a fungal path- ogen of amphibians of Batrachochytrium. Keywords Amphibian chytrid fungus Á Batrachochytrium dendrobatidis Á Biological control Á Daphnia

Blaustein, Andrew R.

63

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

64

UV Radiation and Arctic Freshwater Zooplankton  

Microsoft Academic Search

\\u000a Arctic freshwaters possess simple zooplankton communities.The high Arctic lakes and ponds are commonly inhabited by only a\\u000a few species of rotifers, cladocerans and copepods. Dominant inhabitants of high Arctic zooplankton communities are first and\\u000a foremost members of the circumpolar cladoceran species Daphnia pulex complex (Colbourne et al. 1998; Weider et al. 1999). Members of this complex are recorded in all

D. O. Hessen

65

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

66

Bivalves: From individual to population modelling  

NASA Astrophysics Data System (ADS)

An individual based population model for bivalves was designed, built and tested in a 0D approach, to simulate the population dynamics of a mussel bed located in an intertidal area. The processes at the individual level were simulated following the dynamic energy budget theory, whereas initial egg mortality, background mortality, food competition, and predation (including cannibalism) were additional population processes. Model properties were studied through the analysis of theoretical scenarios and by simulation of different mortality parameter combinations in a realistic setup, imposing environmental measurements. Realistic criteria were applied to narrow down the possible combination of parameter values. Field observations obtained in the long-term and multi-station monitoring program were compared with the model scenarios. The realistically selected modeling scenarios were able to reproduce reasonably the timing of some peaks in the individual abundances in the mussel bed and its size distribution but the number of individuals was not well predicted. The results suggest that the mortality in the early life stages (egg and larvae) plays an important role in population dynamics, either by initial egg mortality, larvae dispersion, settlement failure or shrimp predation. Future steps include the coupling of the population model with a hydrodynamic and biogeochemical model to improve the simulation of egg/larvae dispersion, settlement probability, food transport and also to simulate the feedback of the organisms' activity on the water column properties, which will result in an improvement of the food quantity and quality characterization.

Saraiva, S.; van der Meer, J.; Kooijman, S. A. L. M.; Ruardij, P.

2014-11-01

67

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

Microsoft Academic Search

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

Jonathan B. Shurin

2000-01-01

68

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

Microsoft Academic Search

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

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

1989-01-01

69

Design issues for population growth models  

PubMed Central

We briefly review and discuss design issues for population growth and decline models. We then use a flexible growth and decline model as an illustrative example and apply optimal design theory to find optimal sampling times for estimating model parameters, specific parameters and interesting functions of the model parameters for the model with two real applications. Robustness properties of the optimal designs are investigated when nominal values or the model is mis-specified, and also under a different optimality criterion. To facilitate use of optimal design ideas in practice, we also introduce a website for generating a variety of optimal designs for popular models from different disciplines. PMID:21647244

López Fidalgo, J.; Ortiz Rodríguez, I.M.

2010-01-01

70

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

71

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...

72

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

SciTech Connect

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

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

1981-05-01

73

LIMNETIC ZOOPLANKTON OF LAKES IN KATMAI NATIONAL MONUMENT, ALASKA  

EPA Science Inventory

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

74

Population dynamics simulations of functional model proteins  

NASA Astrophysics Data System (ADS)

In order to probe the fundamental principles that govern protein evolution, we use a minimalist model of proteins to provide a mapping from genotype to phenotype. The model is based on physically realistic forces of protein folding and includes an explicit definition of protein function. Thus, we can find the fitness of a sequence from its ability to fold to a stable structure and perform a function. We study the fitness landscapes of these functional model proteins, that is, the set of all sequences mapped on to their corresponding fitnesses and connected to their one mutant neighbors. Through population dynamics simulations we directly study the influence of the nature of the fitness landscape on evolution. Populations are observed to move to a steady state, the distribution of which can often be predicted prior to the population dynamics simulations from the nature of the fitness landscape and a quantity analogous to a partition function. In this paper, we develop a scheme for predicting the steady-state population on a fitness landscape, based on the nature of the fitness landscape, thereby obviating the need for explicit population dynamics simulations and providing some insight into the impact on molecular evolution of the nature of fitness landscapes. Poor predictions are indicative of fitness landscapes that consist of a series of weakly connected sublandscapes.

Blackburne, Benjamin P.; Hirst, Jonathan D.

2005-10-01

75

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

76

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

77

Modeling population genetic data in autotetraploid species.  

PubMed

Allozyme and PCR-based molecular markers have been widely used to investigate genetic diversity and population genetic structure in autotetraploid species. However, an empirical but inaccurate approach was often used to infer marker genotype from the pattern and intensity of gel bands. Obviously, this introduces serious errors in prediction of the marker genotypes and severely biases the data analysis. This article developed a theoretical model to characterize genetic segregation of alleles at genetic marker loci in autotetraploid populations and a novel likelihood-based method to estimate the model parameters. The model properly accounts for segregation complexities due to multiple alleles and double reduction at autotetrasomic loci in natural populations, and the method takes appropriate account of incomplete marker phenotype information with respect to genotype due to multiple-dosage allele segregation at marker loci in tetraploids. The theoretical analyses were validated by making use of a computer simulation study and their utility is demonstrated by analyzing microsatellite marker data collected from two populations of sycamore maple (Acer pseudoplatanus L.), an economically important autotetraploid tree species. Numerical analyses based on simulation data indicate that the model parameters can be adequately estimated and double reduction is detected with good power using reasonable sample size. PMID:16172506

Luo, Z W; Zhang, Ze; Zhang, R M; Pandey, Madhav; Gailing, Oliver; Hattemer, Hans H; Finkeldey, Reiner

2006-01-01

78

Modeling Population Genetic Data in Autotetraploid Species  

PubMed Central

Allozyme and PCR-based molecular markers have been widely used to investigate genetic diversity and population genetic structure in autotetraploid species. However, an empirical but inaccurate approach was often used to infer marker genotype from the pattern and intensity of gel bands. Obviously, this introduces serious errors in prediction of the marker genotypes and severely biases the data analysis. This article developed a theoretical model to characterize genetic segregation of alleles at genetic marker loci in autotetraploid populations and a novel likelihood-based method to estimate the model parameters. The model properly accounts for segregation complexities due to multiple alleles and double reduction at autotetrasomic loci in natural populations, and the method takes appropriate account of incomplete marker phenotype information with respect to genotype due to multiple-dosage allele segregation at marker loci in tetraploids. The theoretical analyses were validated by making use of a computer simulation study and their utility is demonstrated by analyzing microsatellite marker data collected from two populations of sycamore maple (Acer pseudoplatanus L.), an economically important autotetraploid tree species. Numerical analyses based on simulation data indicate that the model parameters can be adequately estimated and double reduction is detected with good power using reasonable sample size. PMID:16172506

Luo, Z. W.; Zhang, Ze; Zhang, R. M.; Pandey, Madhav; Gailing, Oliver; Hattemer, Hans H.; Finkeldey, Reiner

2006-01-01

79

Zooplankton Size and Taxonomic Selectivity of Channel Catfish Fry  

Microsoft Academic Search

Zooplankton utilization and their importance to channel catfish Ictalurus punctatus fry during pond culture is not well documented. Current fry stocking decisions are based on total zooplankton densities. We studied the feeding habits (zooplankton size and taxa selection) of channel catfish fry. Catfish fry just completing swim-up were placed into glass aquaria or into cages in ponds and allowed to

Charles C. Mischke; David J. Wise

2003-01-01

80

ORIGINAL PAPER Global patterns of epipelagic gelatinous zooplankton biomass  

E-print Network

ORIGINAL PAPER Global patterns of epipelagic gelatinous zooplankton biomass M. K. S. Lilley · S. E no global synthesis of patterns of gelatinous zooplankton biomass (GZB), an important first step abundance of gelatinous zooplankton did not co- vary with depth. Introduction There is intense interest

Hays, Graeme

81

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

82

Intercomparison of six Mediterranean zooplankton time series  

NASA Astrophysics Data System (ADS)

We analyzed and compared Mediterranean mesozooplankton time series spanning 1957-2006 from six coastal stations in the Balearic, Ligurian, Tyrrhenian, North and Middle Adriatic and Aegean Sea. Our analysis focused on fluctuations of major zooplankton taxonomic groups and their relation with environmental and climatic variability. Average seasonal cycles and interannual trends were derived. Stations spanned a large range of trophic status from oligotrophic to moderately eutrophic. Intra-station analyses showed (1) coherent multi-taxa trends off Villefranche sur mer that diverge from the previous results found at species level, (2) in Baleares, covariation of zooplankton and water masses as a consequence of the boundary hydrographic regime in the middle Western Mediterranean, (3) decrease in trophic status and abundance of some taxonomic groups off Naples, and (4) off Athens, an increase of zooplankton abundance and decrease in chlorophyll possibly caused by reduction of anthropogenic nutrient input, increase of microbial components, and more efficient grazing control on phytoplankton. (5) At basin scale, the analysis of temperature revealed significant positive correlations between Villefranche, Trieste and Naples for annual and/or winter average, and synchronous abrupt cooling and warming events centered in 1987 at the same three sites. After correction for multiple comparisons, we found no significant correlations between climate indices and local temperature or zooplankton abundance, nor between stations for zooplankton abundance, therefore we suggest that for these coastal stations local drivers (climatic, anthropogenic) are dominant and that the link between local and larger scale of climate should be investigated further if we are to understand zooplankton fluctuations.

Berline, Léo; Siokou-Frangou, Ioanna; Marasovi?, Ivona; Vidjak, Olja; Fernández de Puelles, M.a. Luz; Mazzocchi, Maria Grazia; Assimakopoulou, Georgia; Zervoudaki, Soultana; Fonda-Umani, Serena; Conversi, Alessandra; Garcia-Comas, Carmen; Ibanez, Frédéric; Gasparini, Stéphane; Stemmann, Lars; Gorsky, Gabriel

2012-05-01

83

Population Coding of Visual Space: Modeling  

PubMed Central

We examine how the representation of space is affected by receptive field (RF) characteristics of the encoding population. Spatial responses were defined by overlapping Gaussian RFs. These responses were analyzed using multidimensional scaling to extract the representation of global space implicit in population activity. Spatial representations were based purely on firing rates, which were not labeled with RF characteristics (tuning curve peak location, for example), differentiating this approach from many other population coding models. Because responses were unlabeled, this model represents space using intrinsic coding, extracting relative positions amongst stimuli, rather than extrinsic coding where known RF characteristics provide a reference frame for extracting absolute positions. Two parameters were particularly important: RF diameter and RF dispersion, where dispersion indicates how broadly RF centers are spread out from the fovea. For large RFs, the model was able to form metrically accurate representations of physical space on low-dimensional manifolds embedded within the high-dimensional neural population response space, suggesting that in some cases the neural representation of space may be dimensionally isomorphic with 3D physical space. Smaller RF sizes degraded and distorted the spatial representation, with the smallest RF sizes (present in early visual areas) being unable to recover even a topologically consistent rendition of space on low-dimensional manifolds. Finally, although positional invariance of stimulus responses has long been associated with large RFs in object recognition models, we found RF dispersion rather than RF diameter to be the critical parameter. In fact, at a population level, the modeling suggests that higher ventral stream areas with highly restricted RF dispersion would be unable to achieve positionally-invariant representations beyond this narrow region around fixation. PMID:21344012

Lehky, Sidney R.; Sereno, Anne B.

2011-01-01

84

Eutrophication-like response to climate warming: an analysis of Lago Maggiore (N. Italy) zooplankton in contrasting years  

Microsoft Academic Search

Global mean surface temperatures are increasing. All ecosystems are likely to be affected and there is much interest at present in predicting the effects. In freshwater environments, we expect to observe, among other things, effects similar to those observed under eutrophication, such as increases in zooplankton population density and biomass as a result of enhanced population growth rates. Lago Maggiore

Anna VISCONTI; Marina MANCA; Riccardo DE BERNARDI

85

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

86

The nk model and population genetics.  

PubMed

The nk model of fitness interactions is examined. This model has been used by previous authors to investigate the effects of fitness epistasis on substitution dynamics in molecular evolution, and to make broader claims about the importance of epistasis. To examine these claims, an infinite-allele approximation is introduced. In this limit, it is shown that the nk model is, at an appropriate level of description, formally identical to the non-epistatic House-of-Cards model--a well-studied model in theoretical population genetics. It is further shown that in many parameter regimes, the analytical results obtained from this infinite-allele approximation are very close to results from the full nk model (with a finite number of alleles per locus). The findings presented shed light on a number of previous results. PMID:15784268

Welch, John J; Waxman, David

2005-06-01

87

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 ...

88

Zooplankton, fish and fisheries in tropical freshwaters  

Microsoft Academic Search

About 40% of all fish species occur in freshwater, although only 1% of the globe is occupied by freshwaters. The tropics harbour a high percentage of these fishes. Freshwater zooplankton on the other hand is far less diverse than its marine counterpart and the tropics do not harbour a markedly high percentage of freshwater species either. The antecedents of freshwater

C. H. Fernando

1994-01-01

89

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

90

Cyanobacterial chemical warfare affects zooplankton community composition  

Microsoft Academic Search

SUMMARY 1. Toxic algal blooms widely affect our use of water resources both with respect to drinking water and recreation. However, it is not only humans, but also organisms living in freshwater and marine ecosystems that may be affected by algal toxins. 2. In order to assess if cyanobacterial toxins affect the composition of natural zooplankton communities, we quantified the

LARS-ANDERS HANSSON; SUSANNE GUSTAFSSON; KARIN RENGEFORS; LINA BOMARK

2007-01-01

91

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

92

ANALOG COMPUTER MODELS OF FISH POPULATIONS  

Microsoft Academic Search

ABSTRACT A modern,analo~,computer. tol1ether with an X-Y plotter, I provides a means of constructinl1 useful models of commercially,exploited fish populations.,The model combined,conventional,exponential,fishin~and natural mortality rates with a Gompertz,curve,of,~owth,in wei~ht.,By combination,of these rates and curve into a sinl1le differential equation. survival,curves,for suc­ cessive year classes of fish were ~enerated,by the com­ puter and plotted by the plotter. Wei~hts,for all year classes

Ralph P. Silliman

93

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

94

Modeling spatial aggregation of finite populations.  

PubMed

Accurate description of spatial distribution of species is essential for correctly modeling macroecological patterns and thus to infer mechanisms of species coexistence. The Poisson and negative binomial distribution (NBD) are most widely used to respectively model random and aggregated distributions of species in infinitely large areas. As a finite version of the Poisson distribution, the binomial distribution is used to model random distribution of species populations in finite areas. Despite that spatial aggregation is the most widespread pattern and no species in nature are distributed in infinitely large areas, no model is currently available to describe spatial aggregation for species distributed in finite areas. Here we develop a finite counterpart of the NBD to model aggregated species in finite landscapes. Similar to the NBD, this new model also has a parameter k measuring spatial aggregation. When k --> infinity, this model becomes the binomial distribution; when study area approaches infinite, it becomes the NBD. This model was extensively evaluated against the distributions of over 300 tree species in a 50-ha stem-mapping plot from Barro Colorado Island, Panama. The results show that when sampling area is small (relative to the study area), the new model and the NBD are of little difference. But the former correctly models spatial distribution at the finite limit at which the NBD fails. We reveal serious theoretical pathologies by using infinite models to approximate finite distribution and show the theoretical and practical advantages for using the new finite model for modeling species-area relationships, species occupancy and spatial distribution of rare species. PMID:21302840

Zillio, Tommaso; He, Fangliang

2010-12-01

95

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

96

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

E-print Network

Effects of piscivore-mediated habitat use on growth, diet and zooplankton consumption of roach, Limnological Institute, Konstanz, Germany SUMMARY 1. We used an individual based modelling approach for roach; (ii) analyse the relevance of these habitat shifts for the diet, activity costs and growth of roach

97

Bridging the gap between marine biogeochemical and fisheries sciences; configuring the zooplankton link  

NASA Astrophysics Data System (ADS)

Exploring climate and anthropogenic impacts on marine ecosystems requires an understanding of how trophic components interact. However, integrative end-to-end ecosystem studies (experimental and/or modelling) are rare. Experimental investigations often concentrate on a particular group or individual species within a trophic level, while tropho-dynamic field studies typically employ either a bottom-up approach concentrating on the phytoplankton community or a top-down approach concentrating on the fish community. Likewise the emphasis within modelling studies is usually placed upon phytoplankton-dominated biogeochemistry or on aspects of fisheries regulation. In consequence the roles of zooplankton communities (protists and metazoans) linking phytoplankton and fish communities are typically under-represented if not (especially in fisheries models) ignored. Where represented in ecosystem models, zooplankton are usually incorporated in an extremely simplistic fashion, using empirical descriptions merging various interacting physiological functions governing zooplankton growth and development, and thence ignoring physiological feedback mechanisms. Here we demonstrate, within a modelled plankton food-web system, how trophic dynamics are sensitive to small changes in parameter values describing zooplankton vital rates and thus the importance of using appropriate zooplankton descriptors. Through a comprehensive review, we reveal the mismatch between empirical understanding and modelling activities identifying important issues that warrant further experimental and modelling investigation. These include: food selectivity, kinetics of prey consumption and interactions with assimilation and growth, form of voided material, mortality rates at different age-stages relative to prior nutrient history. In particular there is a need for dynamic data series in which predator and prey of known nutrient history are studied interacting under varied pH and temperature regimes.

Mitra, Aditee; Castellani, Claudia; Gentleman, Wendy C.; Jónasdóttir, Sigrún H.; Flynn, Kevin J.; Bode, Antonio; Halsband, Claudia; Kuhn, Penelope; Licandro, Priscilla; Agersted, Mette D.; Calbet, Albert; Lindeque, Penelope K.; Koppelmann, Rolf; Møller, Eva F.; Gislason, Astthor; Nielsen, Torkel Gissel; St. John, Michael

2014-12-01

98

Proliferation in Cell Population Models with Age Structure Frdrique Billy  

E-print Network

differential models, focusing on age synchronisation in the cell division cycle in cell populations and itsProliferation in Cell Population Models with Age Structure Frédérique Billy , Jean Clairambault) performed at the single cell level in proliferating cell populations allows identifying model parameters

Clairambault, Jean

99

A Structured Population Model of Cell Differentiation Marie Doumic  

E-print Network

A Structured Population Model of Cell Differentiation Marie Doumic Anna Marciniak-Czochra Beno-words. Structured population dynamics; transport equation; stem cells; cell differ- entiation; INRIA Paris structured population model of cell differentiation 2 Contents 1 A Model of Continuous Cell Differentiation 4

Zubelli, Jorge Passamani

100

Promotion of harmful algal blooms by zooplankton predatory activity  

PubMed Central

The relationship between algae and their zooplanktonic predators typically involves consumption of nutrients by algae, grazing of the algae by zooplankton which in turn enhances predator biomass, controls algal growth and regenerates nutrients. Eutrophication raises nutrient levels, but does not simply increase normal predator–prey activity; rather, harmful algal bloom (HAB) events develop often with serious ecological and aesthetic implications. Generally, HAB species are outwardly poor competitors for nutrients, while their development of grazing deterrents during nutrient stress ostensibly occurs too late, after the nutrients have largely been consumed already by fast-growing non-HAB species. A new mechanism is presented to explain HAB dynamics under these circumstances. Using a multi-nutrient predator–prey model, it is demonstrated that these blooms can develop through the self-propagating failure of normal predator–prey activity, resulting in the transfer of nutrients into HAB growth at the expense of competing algal species. Rate limitation of this transfer provides a continual level of nutrient stress that results in HAB species exhibiting grazing deterrents protecting them from top-down control. This process is self-stabilizing as long as nutrient demand exceeds supply, maintaining the unpalatable status of HABs; such events are most likely under eutrophic conditions with skewed nutrient ratios. PMID:17148360

Mitra, Aditee; Flynn, Kevin J

2006-01-01

101

Toward the Census of Marine Life: Proof of Concept through the Integration of Traditional, Optical and Acoustic Zooplankton and Fish  

E-print Network

of traditional, optical, and acoustical information to demonstrate the benefits of quantifying marine populationsToward the Census of Marine Life: Proof of Concept through the Integration of Traditional, Optical and Acoustic Zooplankton and Fish Data in the Chesapeake Bay Primary Investigators: Stuart A. Ludsin - Ohio

102

Making MILES better for stellar population modelling  

NASA Astrophysics Data System (ADS)

In order to build more realistic single stellar population (SSP) models with variable ?-enhancement, we have recently determined [Mg/Fe] in a uniform scale with a precision of about 0.1 dex for 752 stars in the MILES empirical library. The [?/Fe] abundance ratio is commonly used as a good temporal scale indicator of star formation, taking Mg as a template for ? elements. Calcium is another element whose abundance is currently being investigated for the MILES stars. The MILES library is also being expanded by around 20% by including stars with known T_eff, log g, [Fe/H] and [Mg/Fe]. The transformation of their photospheric parameters to the MILES system has been carried out, but the calibration of their [Mg/Fe] is still in progress. In parallel, C, N and O abundances are also being compiled from literature for the library stars because they play an important role in the photospheric opacity, particularly influencing the blue spectral region. The Galactic kinematic classification of MILES stars with compiled [Mg/Fe] has been just computed such that this information can be considered in the SSP modelling. Comparisons of theoretical stellar predictions of the Lick line-strength indices against the MILES data have revealed the good behaviour of Fe-sensitive indices predictions, while highlighting areas for improvement in some models for the higher order H-Balmer features.

de C. Milone, A.; Sansom, A.; Vazdekis, A.; Sánchez-Blázquez, P.; Allende Prieto, C.; Falcón-Barroso, J.; da Silva, R.

103

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

104

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). Patterns in the dispersal graphs highlight pathways for larval dispersal along major ocean currents

Queensland, University of

105

Overview of week ahead Single Population Models  

E-print Network

project - Presentations on Friday Lecture 3: A Feedback Control Approach to Nonlinear Population Dynamics project - Presentations on Friday Lecture 3: A Feedback Control Approach to Nonlinear Population Dynamics: A Feedback Control Approach to Nonlinear Population Dynamics Lecture 4: Diffusion Driven Instability

Knobloch,Jürgen

106

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

Microsoft Academic Search

The relationships between the seasonal fluctuations of the copepod Eurytemora affinis and the mysid Neomysis integer were studied from observed data and experimental results, using a predator–prey model in the oligo-mesohaline area of the Gironde estuary. Mean seasonal fluctuations of abundances were derived from long term data series collected from 1978 to 2003 for both species. In situ predator–prey experiments

Valérie David; Pierre Chardy; Benoît Sautour

2006-01-01

107

Modeling Populations and Habitats for Kirtland's Warbler  

NSDL National Science Digital Library

Conserving endangered species often requires a balancing of the biological needs of endangered populations against the human desires for economic and recreational opportunities. At least some biological aspects of every species are poorly understood, some do have large data sets that can be difficult to interpret. All are confounded by human interactions. Computational science allows visualization, analysis, and interpretation of large data sets in ways that can inform these complex biological and environmental problems. This module will allow students to explore one of the fundamental paradigms of conservation biology, island biogeography, and apply that theoretical ecological concept to a real-world problem by creating models for habitat management. Specifically this module reviews island biogeography as it applies to forest fragmentation in northern Michigan and uses the related concepts to explore applications to preservation of the endangered Kirtland's warbler (Dendroica kirtlandii). Students will learn fundamental ecological concepts, visualize and analyze large spatial data sets of an endangered species using a free but sophisticated geographic information system (GIS), and develop an environmental impact statement formatted output to explain recommendations based on their analysis of the data and developed models.

Lewis, Timothy L.

108

Sources of zooplankton on the Nova Scotia shelf and their aggregations within deep-shelf basins  

NASA Astrophysics Data System (ADS)

A large-scale survey/study of zooplankton on the Scotian Shelf south of Nova Scotia was performed during 1984 1985. Rapid sampling was accomplished using a Batfish vehicle mounted with an optical plankton counter, a multiple opening/closing net system (BIONESS), and multifrequency acoustics. From the Batfish survey reported here, we present evidence indicating that the dominant supply of zooplankton to the Scotian Shelf is provided by the Nova Scotia Current, a strong localized flow adjacent to the coast. During late winter and spring, the Nova Scotia Current supplies our shelf water with most Calanus species which originate from the Gulf of St Lawrence to the north. Further sampling indicated that the deep Scotian Shelf basins harbor large populations of zooplankton during autumn and winter which consist mainly of stages IV and V of C. finmarchicus, C. hyperboreus, and C. glacialis. This winter storage mechanism is also a dominant source of young copepedite stages in surface waters during the spring. Weak circulation within the shelf basins ensures that copepod populations are not displaced throughout the year.

Herman, A. W.; Sameoto, D. D.; Shunnian, Chen; Mitchell, M. R.; Petrie, B.; Cochrane, N.

1991-03-01

109

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

NASA Astrophysics Data System (ADS)

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

David, Valérie; Chardy, Pierre; Sautour, Benoît

2006-05-01

110

Changes in the Lake Superior Crustacean Zooplankton Community  

Microsoft Academic Search

We examined crustacean zooplankton densities at five locations in two regions of Lake Superior during a time period that spanned two decades, for three years in the early 1970's and again for three years in the early 1990's. We used coupled multivariate and univariate analyses to find whether the zooplankton community had changed over these decades, and to determine if

Jason Link; James H. Selgeby; Robert E. Keen

2004-01-01

111

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

112

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

113

Research On Zooplankton in the Gulf of Rapallo  

Microsoft Academic Search

Zooplankton samples, collected in autumn 1996 from two stations in the Gulf of Rapallo, Ligurian Sea (Rapallo Harbour and Prelo Bay, which is a more open site with lower human impacts) were analysed. at both stations, the community was dominated by copepods (mainly juveniles and adults of different species of Acartia and Oithona) and meroplankton (mainly polychaete larvae). Total zooplankton

S. Sei; P. Licandro; Zunini Sertorio; I. Ferrari

1999-01-01

114

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

115

Mapping Oceanic Zooplankton Distributions -A Challenge for Ultrasonics  

E-print Network

Mapping Oceanic Zooplankton Distributions - A Challenge for Ultrasonics Gwyn Griffiths, Ocean Oceanography Centre Presented at a colloquium 'Ultrasonics in Oceanography' organised by the University.soc.soton.ac.uk/OTD #12;Mapping Oceanic Zooplankton Distributions - A Challenge for Ultrasonics Gwyn Griffiths, Ocean

Griffiths, Gwyn

116

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...

117

Harvesting and Processing Zooplankton for Use as Supplemental Fry Feed  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

118

Upslope transport of near-bed zooplankton  

NASA Astrophysics Data System (ADS)

Zooplankton residing just above the deep-sea floor is an important component of the benthic/benthopelagic food chain. Consuming planktonic particulates and organisms, holoplankton and meroplankton are prey for fish and large invertebrates. Mechanisms controlling their abundances have been explored over relatively long time scales (months to years). Here, zooplankton were sampled every 2 h for 2.2 d using a moored, automated, serial zooplankton pump. The physical regime (currents and temperature) 1-100 m above bottom was measured during an inclusive 24-d period. The study site was located on the upper continental slope (750 m) of the Mid-Atlantic Bight, between the productive shelf and more impoverished rise and abyss. The coupled biological and physical records indicated tidally driven, net upslope transport of the holoplankton. The copepod (74.5% of collections) time series showed marked periodicity with a peak frequency of ˜13 h, approximately the diurnal tide (Fourier analysis). Local maxima corresponded with minimal water temperatures. Moreover, tidal cross-slope flow was highly coherent and 90° out of phase with temperature. Thus, maximal copepod concentrations, originating in colder deeper water, would be transported up the slope by the tide. Estimated net displacement of ˜1 km/d would deliver the animals to continental-shelf depths within a couple weeks. Time series of the much less abundant larvaceans (urochordates) (15.3%) and polychaete larvae (8.9%) showed periodicities with peak frequencies of 8-9 h. Statistical significance of the periodic signals could not be determined due to low numbers. Revealing holoplankton dynamics on scales of hours, this study may contribute to understanding of, for example, copepod feeding and aggregation near the deep-sea floor.

Zimmer, Cheryl Ann

2009-09-01

119

The Role of Models in (Population) Ecology "Populations grow, but only to a point".  

E-print Network

1 The Role of Models in (Population) Ecology TYPES: ·Verbal "Populations grow, but only to a point for applied problems! Empirical Predict system behavior, compare with data of actual system behavior Model elements of a given problem They can be verbal, graphical, or mathematical; purpose can be heuristic

Gervais, Jennifer

120

Spatio-Temporal Variability of the North Sea Cod Recruitment in Relation to Temperature and Zooplankton  

PubMed Central

The North Sea cod (Gadus morhua, L.) stock has continuously declined over the past four decades linked with overfishing and climate change. Changes in stock structure due to overfishing have made the stock largely dependent on its recruitment success, which greatly relies on environmental conditions. Here we focus on the spatio-temporal variability of cod recruitment in an effort to detect changes during the critical early life stages. Using International Bottom Trawl Survey (IBTS) data from 1974 to 2011, a major spatio-temporal change in the distribution of cod recruits was identified in the late 1990s, characterized by a pronounced decrease in the central and southeastern North Sea stock. Other minor spatial changes were also recorded in the mid-1980s and early 1990s. We tested whether the observed changes in recruits distribution could be related with direct (i.e. temperature) and/or indirect (i.e. changes in the quantity and quality of zooplankton prey) effects of climate variability. The analyses were based on spatially-resolved time series, i.e. sea surface temperature (SST) from the Hadley Center and zooplankton records from the Continuous Plankton Recorder Survey. We showed that spring SST increase was the main driver for the most recent decrease in cod recruitment. The late 1990s were also characterized by relatively low total zooplankton biomass, particularly of energy-rich zooplankton such as the copepod Calanus finmarchicus, which have further contributed to the decline of North Sea cod recruitment. Long-term spatially-resolved observations were used to produce regional distribution models that could further be used to predict the abundance of North Sea cod recruits based on temperature and zooplankton food availability. PMID:24551103

Nicolas, Delphine; Rochette, Sébastien; Llope, Marcos; Licandro, Priscilla

2014-01-01

121

Effects of simple environmental feedback on some population models  

NASA Astrophysics Data System (ADS)

Lovelock used a model of an idealised planet to demonstrate the stabilising effect of feedback on a population of daisies and environmental temperature. The equations he used represented a population model with only two steady states: no daisies present, or a stable population with monotonic damping. This paper investigates whether a similar result is obtained with a less stable population model. It was found that simple feedbacks, mediated by albedo and temperature, or by CO2 and the "greenhouse" effect, did not alter the basic properties of population models but could alter the stability regime within which a certain set of population parameters operated. Models of populations with discrete generations tended to be less stable with feedback while those with continuous growth were more stable. This confirms that Lovelock's result is not highly dependent on the type of population model. Adding environmental feedback to simple population models does not alter the basic properties of the models themselves but leads to a stabilisation of the whole system of environment plus population.

Maddock, Linda

1991-07-01

122

Population Modeling and Implications for Caribbean Hawksbill Sea Turtle Management  

Microsoft Academic Search

Population models provide a means to predict a population's likely response to a particular perturbation, and to evaluate the importance of data gaps with respect to the model's predictive capabilities. Current data are inadequate for development of a comprehen- sive, predictive model for hawksbill sea turtles ( Eretmochelys imbricata). However, the growth, age to maturity, and fecundity data available suggest

DEBORAH T. CROUSE

123

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...

124

Random effects models and multistage estimation procedures for statistical population reconstruction of small game populations.  

PubMed

Recently, statistical population models using age-at-harvest data have seen increasing use for monitoring of harvested wildlife populations. Even more recently, detailed evaluation of model performance for long-lived, large game animals indicated that the use of random effects to incorporate unmeasured environmental variation, as well as second-stage Horvitz-Thompson-type estimators of abundance, provided more reliable estimates of total abundance than previous models. We adapt this new modeling framework to small game, age-at-harvest models with only young-of-the-year and adult age classes. Our Monte Carlo simulation results indicate superior model performance for the new modeling framework, evidenced by lower bias and proper confidence interval coverage. We apply this method to male wild turkey harvest in the East Ozarks turkey productivity region, Missouri, USA, where statistical population reconstruction indicates a relatively stationary population for 1996-2010. PMID:23755199

Gast, Christopher M; Skalski, John R; Isabelle, Jason L; Clawson, Michael V

2013-01-01

125

Some superpopulation models for estimating the number of population uniques  

E-print Network

- nomial distribution, statistical disclosure control 1 Introduction The number of the population uniquesSome superpopulation models for estimating the number of population uniques Akimichi Takemura in the population is of great importance in evaluating the disclosure risk of a microdata set. We approach

Takemura, Akimichi

126

population model Harald Rybka, Jason Wong, Jorge Rivas  

E-print Network

yield improved pollution control reduced land erosion stabilized population with the right policiesA simple population model Harald Rybka, Jason Wong, Jorge Rivas RISE (Research of the book: Limits to Growth, 1972, 2004) computer simulation of interactions between: the population

Yorke, James

127

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...

128

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

129

Population model for Alaska Peninsula sea otters. Final report  

SciTech Connect

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

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

1988-12-31

130

Effects of drought and pluvial periods on fish and zooplankton communities in prairie lakes: systematic and asystematic responses.  

PubMed

The anticipated impacts of climate change on aquatic biota are difficult to evaluate because of potentially contrasting effects of temperature and hydrology on lake ecosystems, particularly those closed-basin lakes within semiarid regions. To address this shortfall, we quantified decade-scale changes in chemical and biological properties of 20 endorheic lakes in central North America in response to a pronounced transition from a drought to a pluvial period during the early 21st century. Lakes exhibited marked temporal changes in chemical characteristics and formed two discrete clusters corresponding to periods of substantially different effective moisture (as Palmer Drought Severity Index, PDSI). Discriminant function analysis (DFA) explained 90% of variability in fish assemblage composition and showed that fish communities were predicted best by environmental conditions during the arid interval (PDSI <-2). DFA also predicted that lakes could support more fish species during pluvial periods, but their occurrences may be limited by periodic stress due to recurrent droughts and physical barriers to colonization. Zooplankton taxonomic assemblages in fishless lakes were resilient to short-term changes in meteorological conditions, and did not vary between drought and deluge periods. Conversely, zooplankton taxa in fish-populated lakes decreased substantially in biomass during the wet interval, likely due to increased zooplanktivory by fish. The powerful effects of such climatic variability on hydrology and the strong subsequent links to water chemistry and biota indicate that future changes in global climate could result in significant restructuring of aquatic communities. Together these findings suggest that semiarid lakes undergoing temporary climate shifts provide a useful model system for anticipating the effects of global climate change on lake food webs. PMID:23960001

Starks, Elizabeth; Cooper, Ryan; Leavitt, Peter R; Wissel, Björn

2014-04-01

131

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

132

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

133

Zooplankton distribution in the western Arctic during summer 2002: Hydrographic habitats and implications for food chain dynamics  

NASA Astrophysics Data System (ADS)

Global warming is presently a widely accepted phenomenon with a broad range of anticipated impacts on marine ecosystems. Alterations in temperature, circulation and ice cover in Arctic seas may result in changes in food chain dynamics, beginning with planktonic processes. As part of the Shelf-Basin Interactions (SBI) program, we conducted zooplankton surveys during summer 2002 to assess the biomass, distribution and abundance of copepods and other pelagic zooplankton over the Chukchi and Beaufort shelves, slope regions and the adjacent Canada Basin. The motivation for our fieldwork was the question, "Will global change, particularly warming, result in more large-sized zooplankton which support a pelagic food web of fish, birds, and certain mammals over the Chukchi and Beaufort shelves or in more smaller-sized zooplankton which will diminish the fish, birds and mammals and favor sedentary benthic organisms?" The objectives of the present study were 1) to census the regional zooplankton community and establish a baseline for comparisons with historical and future studies and 2) to determine whether large-bodied copepods associated with deep waters of the Bering Sea or the Canada Basin were transported to the shelves in sufficient numbers to modify the food web in a region where smaller copepods often dominate the zooplankton numerically. Spatial distributions of zooplankton communities were clearly associated with hydrographic habitats determined by the chemical, physical and biological characteristics of the upper water layer. Smaller taxa dominated the shelf communities while offshore zooplankton assemblages were characterized by large-bodied copepods. The mesozooplankton community was numerically dominated by copepod nauplii and small-bodied juveniles, including Pseudocalanus spp. and Oithona similis. We observed very few large-bodied copepods from the Bering Sea. However, much of the shelf region surveyed included relatively numerous Calanus glacialis juveniles and adults, suggesting that these copepods were advected onto the shelf and possibly reproducing there. Juvenile stages of the large-bodied copepod Calanus hyperboreus were found in relative abundance on the Chukchi shelf in the vicinity of Hanna Canyon. These observations suggest that large-bodied, deep-water species from the basin are advected onto the Chukchi Shelf where they may impact the fate of shelf-derived primary production and alter the food webs of the shelves. Regional comparisons of abundances of selected taxa enumerated in the present study with sample data from the early 1950s suggested that some taxa were more abundant in the SBI region in 2002 than ca. 50 years ago. Long-term changes in planktonic populations are expected to have significant implications for shelf-basin exchange of biogenic material in the Chukchi and Beaufort Seas and the adjacent Arctic Basin.

Lane, Peter V. Z.; Llinás, Leopoldo; Smith, Sharon L.; Pilz, Dora

134

Spatial interaction among nontoxic phytoplankton, toxic phytoplankton, and zooplankton: emergence in space and time.  

PubMed

In homogeneous environments, by overturning the possibility of competitive exclusion among phytoplankton species, and by regulating the dynamics of overall plankton population, toxin-producing phytoplankton (TPP) potentially help in maintaining plankton diversity-a result shown recently. Here, I explore the competitive effects of TPP on phytoplankton and zooplankton species undergoing spatial movements in the subsurface water. The spatial interactions among the species are represented in the form of reaction-diffusion equations. Suitable parametric conditions under which Turing patterns may or may not evolve are investigated. Spatiotemporal distributions of species biomass are simulated using the diffusivity assumptions realistic for natural planktonic systems. The study demonstrates that spatial movements of planktonic systems in the presence of TPP generate and maintain inhomogeneous biomass distribution of competing phytoplankton, as well as grazer zooplankton, thereby ensuring the persistence of multiple species in space and time. The overall results may potentially explain the sustainability of biodiversity and the spatiotemporal emergence of phytoplankton and zooplankton species under the influence of TPP combined with their physical movement in the subsurface water. PMID:19669506

Roy, Shovonlal

2008-10-01

135

Evidence of microplastics in samples of zooplankton from Portuguese coastal waters.  

PubMed

Records of high concentrations of plastic and microplastic marine debris floating in the ocean have led to investigate the presence of microplastics in samples of zooplankton from Portuguese coastal waters. Zooplankton samples collected at four offshore sites, in surveys conducted between 2002 and 2008, with three different sampling methods, were used in this preliminary study. A total of 152 samples were processed and microplastics were identified in 93 of them, corresponding to 61% of the total. Costa Vicentina, followed by Lisboa, were the regions with higher microplastic concentrations (0.036 and 0.033 no. m?³) and abundances (0.07 and 0.06 cm³ m?³), respectively. Microplastic: zooplankton ratios were also higher in these two regions, which is probably related to the proximity of densely populated areas and inputs from the Tejo and Sado river estuaries. Microplastics polymers were identified using Micro Fourier Transformed Infrared Spectroscopy (?-FTIR), as polyethylene (PE), polypropylene (PP) and polyacrylates (PA). The present work is the first report on the composition of microplastic particles collected with plankton nets in Portuguese coastal waters. Plankton surveys from regular monitoring campaigns conducted worldwide may be used to monitor plastic particles in the oceans and constitute an important and low cost tool to address marine litter within the scope of the Marine Strategy Framework Directive (2008/56/EC). PMID:24461782

Frias, J P G L; Otero, V; Sobral, P

2014-04-01

136

Effect of planktivores, zooplankton, and macrobenthos on material flow in a small lake  

SciTech Connect

Planktivores, zooplankton grazers, and macrobenthos were studied to determine how changes in animal community structure may alter the flow of material in Dunham Pond, CT. Chaoborus and chironomid larvae were studied to determine how they affect the flux of matter across the sediment/water interface. This was done by incubating undisturbed cores in situ and relating changes in water chemistry to larval density. The log-transformed flux rates of iron, manganese, and phosphorus were linearly related to larval biomass. Functional groups may be successfully used to predict rates of material flow. Changes in the mass of macroinvertebrates affect the flux rates of redox-active substances across the sediment/water interface. The use of population densities and feeding characteristics to estimate trophic transfer in Dunham Pond indicate that (1) visual planktivory by larval perch may result in overutilization of prey, (2) ambush planktivory by univoltine Chaoborus appears to under utilize prey, and (3) zooplankton grazing tracks net primary productivity, regardless of zooplankton community structure. Animal groups cycle 30-100% of the phosphorus required for /sup 14/C productivity in Dunham Pond.

Starkel, W.M.

1985-01-01

137

Zooplankton functional groups on the continental shelf of the yellow sea  

NASA Astrophysics Data System (ADS)

Zooplankton plays a vital role in marine ecosystems. Variations in the zooplankton species composition, biomass, and secondary production will change the structure and function of the ecosystem. How to describe this process and make it easier to be modeled in the Yellow Sea ecosystem is the main purpose of this paper. The zooplankton functional groups approach, which is considered a good method of linking the structure of food webs and the energy flow in the ecosystems, is used to describe the main contributors of secondary produciton of the Yellow Sea ecosystem. The zooplankton can be classified into six functional groups: giant crustaceans, large copepods, small copepods, chaetognaths, medusae, and salps. The giant crustaceans, large copepods, and small copepods groups, which are the main food resources for fish, are defined depending on the size spectrum. Medusae and chaetognaths are the two gelatinous carnivorous groups, which compete with fish for food. The salps group, acting as passive filter-feeders, competes with other species feeding on phytoplankton, but their energy could not be efficiently transferred to higher trophic levels. From the viewpoint of biomass, which is the basis of the food web, and feeding activities, the contributions of each functional group to the ecosystem were evaluated; the seasonal variations, geographical distribution patterns, and species composition of each functional group were analyzed. The average zooplankton biomass was 2.1 g dry wt m -2 in spring, to which the giant crustaceans, large copepods, and small copepods contributed 19, 44, and 26%, respectively. High biomasses of the large copepods and small copepods were distributed at the coastal waters, while the giant crustaceans were mainly located at offshore area. In summer, the mean biomass was 3.1 g dry wt m -2, which was mostly contributed by the giant crustaceans (73%), and high biomasses of the giant crustaceans, large copepods, and small copepods were all distributed in the central part of the Yellow Sea. During autumn, the mean biomass was 1.8 g dry wt m -2, which was similarly constituted by the giant crustaceans, large copepods, and small copepods (36, 33, and 23%, respectively), and high biomasses of the giant crustaceans and large copepods occurred in the central part of the Yellow Sea, while the small copepods were mainly located at offshore stations. The giant crustaceans and large copepods dominated the zooplankton biomass (2.9 g dry wt m -2) in winter, contributing respectively 57 and 27%, and they, as well as the small copepods, were all mainly located in the central part of the Yellow Sea. The chaetognaths group was mainly located in the northern part of the Yellow Sea during all seasons, but contributed less to the biomass compared with the other groups. The medusae and salps groups were distributed unevenly, with sporadic dynamics, mainly along the coastline and at the northern part of the Yellow Sea. No more than 10 species belonging to the respective functional groups dominated the zooplankton biomass and controlled the dynamics of the zooplankton community. The clear picture of the seasonal and spatial variations of each zooplankton functional group makes the complicated Yellow Sea ecosystem easier to be understood and modeled.

Sun, Song; Huo, Yuanzi; Yang, Bo

2010-06-01

138

Periodically forced food-chain dynamics: model predictions and experimental validation.  

PubMed

Despite the recognition of the importance of seasonal forcing in nature, remarkably few studies have theoretically explored periodically forced community dynamics. Here we employ a novel approach called "successional state dynamics" (SSD) to model a seasonally forced predator-prey system. We first generated analytical predictions of the effects of altered seasonality on species persistence and the timing of community state transitions. We then parameterized the model using a zooplankton-phytoplankton system and tested quantitative predictions using controlled experiments. In the majority of cases, timing of zooplankton and algal population peaks matched model predictions. Decreases in growing-period length delayed algal blooms, consequently delaying peaks in zooplankton abundance. Predictions of increased probability of predator extinction at low growing-period lengths were also upheld experimentally. Our results highlight the utility of the SSD modeling approach as a framework for predicting the effects of altered seasonality on the structure and dynamics of multitrophic communities. PMID:19967865

Steiner, Christopher F; Schwaderer, Anne S; Huber, Veronika; Klausmeier, Christopher A; Litchman, Elena

2009-11-01

139

Physiologically structured cell population dynamic models with applications to combined  

E-print Network

Physiologically structured cell population dynamic models with applications to combined drug cytotoxic drugs in the organism. An age-structured PDE cell population model has been designed with drug delivery in the general circulation targeted towards cancer cell pop- ulations, but inevitably reaching

Paris-Sud XI, Université de

140

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...

141

A delayed-recruitment model of population dynamics, with an application to baleen whale populations  

Microsoft Academic Search

This paper studies the delay equation xk+1=?xk+F(xk-ß), which has been employed as a model of baleen whale population dynamics. The two main questions discussed are (a) stability of equilibria, and (b) optimal exploitation policies.

Colin W. Clark

1976-01-01

142

Modelling production per unit of food consumed in fish populations.  

PubMed

The ratio of production-to-consumption (?) reflects how efficiently a population can transform ingested food into biomass. Usually this ratio is estimated by separately integrating cohort per-recruit production and consumption per unit of biomass. Estimates of ? from cohort analysis differ from those that consider the whole population, because fish populations are usually composed of cohorts that differ in their relative abundance. Cohort models for ? also assume a stable age-structure and a constant population size (stationary condition). This may preclude their application to harvested populations, in which variations in fishing mortality and recruitment will affect age-structure. In this paper, we propose a different framework for estimating (?) in which production and consumption are modelled simultaneously to produce a population estimator of ?. Food consumption is inferred from the physiological concepts underpinning the generalised von Bertalanffy growth function (VBGF). This general framework allows the effects of different age-structures to be explored, with a stationary population as a special case. Three models with different complexities, depending mostly on what assumptions are made about age-structure, are explored. The full data model requires knowledge about food assimilation efficiency, parameters of the VBGF and the relative proportion of individuals at age a at time y (Py(a)). A simpler model, which requires less data, is based on the stationary assumption. Model results are compared with estimates from cohort models for ? using simulated fish populations of different lifespans. The models proposed here were also applied to three fish populations that are targets of commercial fisheries in the south-east Pacific. Uncertainty in the estimation of ? was evaluated using a resampling approach. Simulation showed that cohort and population models produce different estimates for ? and those differences depend on lifespan, fishing mortality and recruitment variations. Results from the three case studies show that the population model gives similar estimates to those reported by empirical models in other fish species. This modelling framework allows ? to be related directly to population length- or age-structure and thus has the potential to improve the biological realism of both population and ecosystem models. PMID:25445187

Wiff, Rodrigo; Barrientos, Mauricio A; Milessi, Andrés C; Quiroz, J C; Harwood, John

2015-01-21

143

A Quantitative Model of Honey Bee Colony Population Dynamics  

PubMed Central

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

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

2011-01-01

144

A quantitative model of honey bee colony population dynamics.  

PubMed

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

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

2011-01-01

145

Laguerre-type population dynamics models  

E-print Network

, the exponential function ex is transformed into the Tricomi function C0(-x) := n=0 xn (n!)2 , the powers (x + y-exponentials en(t) are increasing convex functions for t 0, but increasing slower with respect to exp t. For this rea- son these functions are useful in order to approximate different behaviors of population growth

Bretti, Gabriella

146

Augmenting superpopulation capture-recapture models with population assignment data  

USGS Publications Warehouse

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.

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

2011-01-01

147

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

Microsoft Academic Search

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

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

1996-01-01

148

Connecting micro dynamics and population distributions in system dynamics models  

PubMed Central

Researchers use system dynamics models to capture the mean behavior of groups of indistinguishable population elements (e.g., people) aggregated in stock variables. Yet, many modeling problems require capturing the heterogeneity across elements with respect to some attribute(s) (e.g., body weight). This paper presents a new method to connect the micro-level dynamics associated with elements in a population with the macro-level population distribution along an attribute of interest without the need to explicitly model every element. We apply the proposed method to model the distribution of Body Mass Index and its changes over time in a sample population of American women obtained from the U.S. National Health and Nutrition Examination Survey. Comparing the results with those obtained from an individual-based model that captures the same phenomena shows that our proposed method delivers accurate results with less computation than the individual-based model.

Rahmandad, Hazhir; Chen, Hsin-Jen; Xue, Hong; Wang, Youfa

2014-01-01

149

A population growth model forced by random, episodic disturbances  

NASA Astrophysics Data System (ADS)

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

Peckham, S. D.

2011-12-01

150

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

151

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

152

PBPK and population modelling to interpret urine cadmium concentrations of the French population.  

PubMed

As cadmium accumulates mainly in kidney, urinary concentrations are considered as relevant data to assess the risk related to cadmium. The French Nutrition and Health Survey (ENNS) recorded the concentration of cadmium in the urine of the French population. However, as with all biomonitoring data, it needs to be linked to external exposure for it to be interpreted in term of sources of exposure and for risk management purposes. The objective of this work is thus to interpret the cadmium biomonitoring data of the French population in terms of dietary and cigarette smoke exposures. Dietary and smoking habits recorded in the ENNS study were combined with contamination levels in food and cigarettes to assess individual exposures. A PBPK model was used in a Bayesian population model to link this external exposure with the measured urinary concentrations. In this model, the level of the past exposure was corrected thanks to a scaling function which account for a trend in the French dietary exposure. It resulted in a modelling which was able to explain the current urinary concentrations measured in the French population through current and past exposure levels. Risk related to cadmium exposure in the general French population was then assessed from external and internal critical values corresponding to kidney effects. The model was also applied to predict the possible urinary concentrations of the French population in 2030 assuming there will be no more changes in the exposures levels. This scenario leads to significantly lower concentrations and consequently lower related risk. PMID:24998972

Béchaux, Camille; Bodin, Laurent; Clémençon, Stéphan; Crépet, Amélie

2014-09-15

153

Spatially explicit population models: Current forms and future uses  

SciTech Connect

Spatially explicit population models are becoming increasingly useful tools for population ecologists, conservation biologists, and land managers. Models are spatially explicit when they combine a population simulator with a landscaped map that describes the spatial distribution of landscape features. With this map, the locations of habitat patches, individuals, and other items of interest are explicitly incorporated into the model, and the effect of changing landscape features on population dynamics can be studied. In this paper we describe the structure of some spatially explicit models under development and provide examples of current and future research using these models. Spatially explicit models are important tools for investigating scale-related questions in population ecology, especially the response of organisms to habitat change occurring at a variety of spatial and temporal scales. Simulation models that incorporate real-world landscapes, as portrayed by landscape maps created with geographic information systems, are also proving to be crucial in the development of management strategies in response to regional land-use and other global change processes. Spatially explicit population models will increase our ability to accurately model complex landscapes, and therefore should improve both basic ecological knowledge of landscape phenomena and applications of landscape ecology to conservation and management. 58 refs., 1 fig.

Dunning, J.B. Jr.; Stewart, D.J. [Univ. of Georgia, Athens, GA (United States); Danielson, B.J. [Iowa State Univ., Ames, IA (United States); Noon, B.R. [US Forest Service, Arcata, CA (United States); Root, T.L. [Univ. of Michigan, Ann Arbor, MI (United States); Lamberson, R.H. [Humboldt State Univ., Arcata, CA (United States); Stevens, E.E. [Clemson Univ., SC (United States)

1995-02-01

154

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\\u000a adequately supports the growth of both algae and zooplankton without the need to alter the medium to accommodate either the\\u000a algae or the animals. We devised a freshwater medium, named COMBO, that supports excellent growth of both algae and zooplankton.

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

1998-01-01

155

Lipids of gelatinous antarctic zooplankton: Cnidaria and Ctenophora  

Microsoft Academic Search

Antarctic gelatinous zooplankton, including Cnidaria (Calycopsis borchgrevinki, Diphyes antarctica, Stygiomedusa gigantea, Atolla wyvillei, Dimophyes arctica) and Ctenophora (Beroe cucumis, B. forskalii, Pleurobrachia pileus, Bolinopsis infundibulum) were collected near Elephant Island, South Shetland Islands, during January and February 1997 and 1998. Total lipid was\\u000a low in all zooplankton (0.1–5 mg g?1 wet mass) and included primarily polar lipids (59–96% of total

Matthew M. Nelson; Charles F. Phleger; Ben D. Mooney; Peter D. Nichols

2000-01-01

156

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

157

Zooplankton time series from the Strait of Georgia: Results from year-round sampling at deep water locations, 1990-2010  

NASA Astrophysics Data System (ADS)

We have compiled and archived a large fraction of the zooplankton data collected from the Strait of Georgia during the past 50 years. Although the full dataset is very heterogeneous and gappy, sampling since 1990 has been consistent and frequent enough to examine interannual variability of the full zooplankton community. In this paper we focus on deep tows at mid-Strait deep-water locations, where vertical-migratory zooplankton can be captured at all times of day and all seasons. Average zooplankton dryweight biomass is high (?9 g m-2) and varies seasonally between a winter minimum (?4 g m-2) and a broad late-spring to autumn maximum (10-11 g m-2). Much of the biomass in all seasons consists of large crustaceans (copepods, euphausiids and amphipods with oceanic and subarctic zoogeographic affinities) that undergo strong diurnal or seasonal vertical migrations. Their interannual variability is very strong: about an order of magnitude within most zooplankton categories, and nearly two orders of magnitude for euphausiids, large copepods, and chaetognaths. Most (73%) of the interannual variability is accounted for by three principal components. The dominant mode (36%) is a low-frequency decadal fluctuation shared by most zooplankton taxa: declining from 1990 to 1995, increasing to a maximum ?1999-2002, declining to a second minimum in 2005-2007, and then recovering to near-average levels by 2010. This zooplankton signal correlates positively with the North Pacific Gyre Oscillation (NPGO) climate index, negatively with temperature anomalies throughout the water column, and positively (but less consistently) with survival anomalies of Strait of Georgia salmon and herring. Proximal causal mechanisms are less certain, but probably include estuarine advective exchange with outer coast populations, and timing match-mismatch within the Strait.

Mackas, David; Galbraith, Moira; Faust, Deborah; Masson, Diane; Young, Kelly; Shaw, William; Romaine, Stephen; Trudel, Marc; Dower, John; Campbell, Rob; Sastri, Akash; Bornhold Pechter, Elizabeth A.; Pakhomov, Evgeny; El-Sabaawi, Rana

2013-08-01

158

Non-linearity and heterogeneity in modeling of population dynamics.  

PubMed

The study of population growth reveals that the behaviors that follow the power law appear in numerous biological, demographical, ecological, physical and other contexts. Parabolic models appear to be realistic approximations of real-life replicator systems, while hyperbolic models were successfully applied to problems of global demography and appear relevant in quasispecies and hypercycle modeling. Nevertheless, it is not always clear why non-exponential growth is observed empirically and what possible origins of the non-exponential models are. In this paper the power equation is considered within the frameworks of inhomogeneous population models; it is proven that any power equation describes the total population size of a frequency-dependent model with Gamma-distributed Malthusian parameter. Additionally, any super-exponential equation describes the dynamics of inhomogeneous Malthusian density-dependent population model. All statistical characteristics of the underlying inhomogeneous models are computed explicitly. The results of this analysis show that population heterogeneity can be a reasonable explanation for power law accurately describing total population growth. PMID:25262656

Karev, Georgy P

2014-12-01

159

ANALYSIS OF A SIMPLE MODEL FOR ESTIMATING HISTORICAL POPULATION SIZES  

E-print Network

for the bridled dolphin, Stenella attenuata, to investigate the behavior ofthe model by which these historical for several populations of dolphin involved with the yellowfin tuna purse seine fishery. We used the data population with its original size (Southwest Fisheries Center3 J. Schools of dolphin of several species

160

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

161

A decade of predatory control of zooplankton species composition of Lake Michigan  

USGS Publications Warehouse

From 1983 to 1992, 71 species representing 38 genera from the Calanoida, Cladocera, Cyclopoida, Mysidacea, Rotifera, Mollusca and Harpacticoida comprised the offshore zooplankton community of Lake Michigan. Our data demonstrate that the composition and abundance of the calanoid community after 1983 is not unlike that of 1960s and that species diversity of the calanoid community is more diverse than the cladoceran community in the 1990s as compared to the early 1980s. Even though the relative biomass of the cladocerans has remained similar over the 1983-1993 period, the species diversity and evenness of the Cladocera community in the early 1990s is unlike anything that has been previously reported for Lake Michigan. Cladocera dominance is centered in one species, Daphnia galeata mendotae, and only three species of Cladocera were observed in the pelagic region of the lake in 1991 and 1992. Nutrient levels, phytoplankton biomass, and the abundance of planktivorous alewife and bloater chub and Bythotrephes are examined as possible causes of these changes in zooplankton species composition. The increase in Rotifera biomass, but not Crustacea, was correlated with an increase in relative biomass of unicellular algae. Food web models suggest Bythotrephes will cause Lake Michigan's plankton to return to a community similar to that of the 1970s; that is Diaptomus dominated. Such a change has occurred. However, correlational analysis suggest that alewife and bloater chubs (especially juveniles) are affecting size and biomass of larger species of zooplankton as well as Bythotrephes.

Makarewicz, Joseph C.; Bertram, Paul; Lewis, Theodore; Brown, Edward H., Jr.

1995-01-01

162

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

2014-09-12

163

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

164

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

165

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

SciTech Connect

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

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

1981-05-01

166

SPATIALLY-EXPLICIT POPULATION MODELS WITH COMPLEX DECISIONS  

Microsoft Academic Search

Many approaches exist for modeling the response of animals to environmental condition and change. Regardless of the model\\u000a selected, uncertainty is a major component in the modeling of complex physical-biological relationships. Structured methods\\u000a exist for handling uncertainty in these modeling studies, and can facilitate decision-making among stakeholders with differing\\u000a values. We describe two different approaches for modeling population response to

R. GOODWIN; V. PANDEY; G. KIKER; J. KIM

167

Population-level effects in Amphiascus tenuiremis: contrasting matrix- and individual-based population models.  

PubMed

Environmental risk assessment (ERA) is generally based on individual-level endpoints, even though protection goals in ERA intend higher biological levels. Population models have the potential to translate individual-level endpoints to population-level responses and range from simple demographic equations to highly complex individual based models (IBMs). The aims of the current study were to develop a matrix model (MM) with the structure and parameterization proposed in the draft OECD guideline "Harpacticoid copepod development and reproduction test with Amphiascus tenuiremis", and an IBM with the same data requirements. Experimental data from lindane exposure from validation studies of the OECD guideline was projected to the population level. Lindane does not only cause effects on survival and reproduction, but also on the time it takes to develop from larvae to adults. The two model approaches were contrasted in terms of their ability to properly project these effects on development. The MM projected smaller effects of the lindane treatments on population growth rate compared to the IBM since in its proposed structure, it did not include the delay in development explicitly. Population-level EC10 for population growth rate in the IBM was at the same level as the most sensitive individual-level endpoint, whereas the EC10 from the MM was not as sensitive. Based on these findings, our conclusion is that the IBM (or an improved MM) should be used for datasets including shifts in development, whereas the simpler MM is sufficient for datasets where only mortality and reproduction are affected, or as a screening tool in lower-tier population-level ERA. PMID:25456235

Lundström Belleza, Elin; Brinkmann, Markus; Preuss, Thomas G; Breitholtz, Magnus

2014-12-01

168

Estimation of population size using open capture-recapture models  

USGS Publications Warehouse

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

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

2001-01-01

169

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

170

FISHERY-ORIENTED MODEL OF MARYLAND OYSTER POPULATIONS  

EPA Science Inventory

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

171

Generalized population models and the nature of genetic drift  

Microsoft Academic Search

The Wright–Fisher model of allele dynamics forms the basis for most theoretical and applied research in population genetics. Our understanding of genetic drift, and its role in suppressing the deterministic forces of Darwinian selection has relied on the specific form of sampling inherent to the Wright–Fisher model and its diffusion limit. Here we introduce and analyze a broad class of

Ricky Der; Charles L. Epstein; Joshua B. Plotkin

2011-01-01

172

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 ...

173

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

174

Zooplankton Successions in Neighboring Lakes with Contrasting Impacts of Amphibian and Fish Predators  

NASA Astrophysics Data System (ADS)

Two pairs of neighboring subalpine lakes located in the Northern Calcareous Alps of Austria were investigated. Each pair comprised a deeper lake containing European minnows (Phoxinus phoxinus ), and a corresponding shallower lake harboring Alpine newts (Triturus alpestris ) as top predators. Plankton successions within fish and amphibian lakes differed markedly from each other. Throughout the year rotifers numerically dominated within the minnow lakes, while pigmented copepods (Genera Heterocope, Acanthodiaptomus , Arctodiaptomus , Mixodiaptomus ) and Daphnia were prominent in the amphibian lakes, at least early during the ice-free period. We argue that size-selective predation by minnows was the ultimate reason for this predominance of smaller zooplankton. While one of the minnow lakes was characterized by a succession of spatially and temporally segregated rotifer species, the other minnow lake permitted the development of populations of small-sized Bosmina and Ceriodaphnia during summer, probably due to the existence of a strong oxycline allowing zooplankton crustaceans to avoid predation from shore-based shoals of minnows. Once trout were introduced into this lake, minnows were visibly reduced in abundance. Bosmina and Ceriodaphnia disappeared and Daphnia together with a predacious copepod (Heterocope ) emerged either from egg banks or arrived from nearby source populations. We argue that the crustacean communities within the fishless lakes were adapted to the comparatively weak predation rates of Alpine newts.

Schabetsberger, Robert; Grill, Susanne; Hauser, Gabriele; Wukits, Petra

2006-06-01

175

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

NASA Astrophysics Data System (ADS)

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

Turner, Jefferson T.; Borkman, David G.

2005-09-01

176

Bythotrephes invasion elevates trophic position of zooplankton and fish: implications for contaminant biomagnification  

Microsoft Academic Search

We estimated the effects of Bythotrephes longimanus invasion on the trophic position (TP) of zooplankton communities and lake herring, Coregonus artedi. Temporal changes in lacustrine zooplankton communities following Bythotrephes invasion were contrasted with non-invaded reference lakes, and along with published information on zooplankton and herring\\u000a diets, formed the basis of estimated changes in TP. The TP of zooplankton communities and

Michael D. RennieAngela; Angela L. Strecker; Michelle E. Palmer

177

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

178

Population estimates for Bangladesh: The use of a specific transitional population model.  

PubMed

Summary The development of population in Bangladesh was affected by a succession of man-made and natural calamities, such as the Bengal Famine of 1943, refugee movements following the partition of India and Pakistan in 1947, devastating floods and cyclones around 1970, and the military action during the war of liberation. Though there had been a tradition of census taking and vital registration in Bangladesh, as part of the Indian sub-continent, extending for over a century, vital registration was so deficient as to be almost valueless, and there were gross misstatements of age and under-enumeration in the censuses. In the census of 1941, on the other hand, political manoeuvring led to a substantial overcount of the population. In this paper, Bangladesh population trends are studied within the broader framework of the subcontinent, taking account of plausible differentials. A considerable element of uncertainty was introduced into growth trends as a result of variations in the completeness of census-taking and of unrecorded refugee and labour movements across open land borders. In this connection the substantial inflationary bias associated with techniques of population estimation using the dual record system is discussed. The application of stable population models is even less justified in Bangladesh with its history of declining mortality. A transitional age structure model was constructed on the basis of the information available on declining mortality and accelerating growth and the model was made even more specific by modifications which took care of the impact of recent calamities and of unrecorded migration. The population base of the census of 1961 was adjusted in accordance with this model. The local mortality age pattern was used in projecting the population by sex and age groups to the date at which the census was originally due to be taken in 1971, and to the date when it was actually taken in March 1974. The post-1970 calamities and their effect on mortality were ignored. The aggregate estimate of population of 72.9 million in March 1974 is slightly in excess of the census count (by about two per cent) reported provisionally as 71.3 million. The excess in our estimate could be accounted for by the losses due to cyclone and military action. PMID:22091851

Gupta, A D; Roy, S G

1976-03-01

179

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

180

Influence of a multiyear event of low salinity on the zooplankton from Mexican eco-regions of the California Current  

NASA Astrophysics Data System (ADS)

Data are presented from the southern part of the California Current System (CCS) for the period 1997-2007, derived from the IMECOCAL monitoring program. Apart from El Niño 1997 to 1998, and La Niña 1998-1999 the strongest perturbation occurred in 2002 due to an intrusion of subarctic water affecting all the CCS. The response of zooplankton biomass to the strong cooling and freshening of the upper layer was an immediate drop followed by a progressive recovery between 2003 and 2007. Though the low salinity influence ended in 2006, the increased zooplankton trend continued, reinforced by increased upwelling activity beginning 2005 off north Baja California region (30-32°N) and beginning 2006 off central Baja California (24-30°N). Multiple regression analysis was done between regional variables and Upwelling Index (UI) and two basin-scale proxies: the North Pacific Gyre Oscillation (NPGO), and Pacific Decadal Oscillation (PDO). The significant influence of the NPGO on surface salinity, salinity stratification, zooplankton volume and secondary consumers (zooplankton carnivores) suggests a basin scale control on these variables more than local mechanisms. The signature of the NPGO was also evident in the base of the trophic web, but more related to the group of crustacean herbivores in the north eco-region, and the tunicates in central Baja California. In this last region, the effect from NPGO on the zooplankton volume and tunicates was antagonist with UI indicative of similar importance of basin and local processes. However, when the time interval is limited to the post-subarctic intrusion (2003-2007) the significance of multiple regression models and physical variables was lost. Therefore, though data and bio-physical coupling analysis off Baja California suggest a better relation with NPGO compared to PDO, it is still not sufficient to explain the magnitude of the perturbation observed in 2002.

Lavaniegos, Bertha E.

2009-12-01

181

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

182

Thermal habitat constraints on zooplankton species associated with Atlantic cod (Gadus morhua) on the US Northeast Continental Shelf  

NASA Astrophysics Data System (ADS)

The US Northeast Continental Shelf is experiencing a period of increasing temperature levels and range, which impacts the quantity of thermal habitats within the ecosystem. With increasing temperatures, the amount of warmer, surface water thermal habitats (16-27 °C) has increased while there has been a reciprocal decline in cooler water habitats (5-15 °C). These cooler water habitats are the most abundant and comprise the core habitats of the ecosystem. The coldest thermal habitats (1-4 °C), however, have increased slightly in amount or have remained constant, reflecting a discontinuity in the progression of warming along a latitudinal gradient. This discontinuity may be the result of recent changes in the circulation of water masses in the northern Gulf of Maine, potentially associated with the Labrador Current. The contraction of core thermal habitats appears to have had biological consequences on multiple trophic levels. In particular, two zooplankton species associated with the larval feeding of Atlantic cod, Gadus morhua, have declined in abundance in the same areas where cod populations have exhibited continually poor recruitment. The zooplankton species group Pseudocalanus spp., which is associated with winter-spawning cod, has declined on Georges Bank and in the Eastern Gulf of Maine. The zooplankton Centropages typicus has declined in the Gulf of Maine during late summer into fall, potentially affecting spring-spawning cod in that area. These observations are consistent with the hypothesis that portions of the population complex of cod have lower reproductive output due to changes in zooplankton abundance, which we associate with the distribution of temperatures within the ecosystem.

Friedland, Kevin D.; Kane, Joe; Hare, Jonathan A.; Lough, R. Gregory; Fratantoni, Paula S.; Fogarty, Michael J.; Nye, Janet A.

2013-09-01

183

Ancestral Population Genomics: The Coalescent Hidden Markov Model Approach  

PubMed Central

With incomplete lineage sorting (ILS), the genealogy of closely related species differs along their genomes. The amount of ILS depends on population parameters such as the ancestral effective population sizes and the recombination rate, but also on the number of generations between speciation events. We use a hidden Markov model parameterized according to coalescent theory to infer the genealogy along a four-species genome alignment of closely related species and estimate population parameters. We analyze a basic, panmictic demographic model and study its properties using an extensive set of coalescent simulations. We assess the effect of the model assumptions and demonstrate that the Markov property provides a good approximation to the ancestral recombination graph. Using a too restricted set of possible genealogies, necessary to reduce the computational load, can bias parameter estimates. We propose a simple correction for this bias and suggest directions for future extensions of the model. We show that the patterns of ILS along a sequence alignment can be recovered efficiently together with the ancestral recombination rate. Finally, we introduce an extension of the basic model that allows for mutation rate heterogeneity and reanalyze human–chimpanzee–gorilla–orangutan alignments, using the new models. We expect that this framework will prove useful for population genomics and provide exciting insights into genome evolution. PMID:19581452

Dutheil, Julien Y.; Ganapathy, Ganesh; Hobolth, Asger; Mailund, Thomas; Uyenoyama, Marcy K.; Schierup, Mikkel H.

2009-01-01

184

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 ½ of 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

185

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; Agust?, Susana; Carreja, Beatriz; Duarte, Carlos M.

2014-01-01

186

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

187

Population.  

ERIC Educational Resources Information Center

This pamphlet has been prepared in response to a new problem, a rapidly increasing population, and a new need, population education. It is designed to help teachers provide their students with some basic population concepts with stress placed on the elements of decision making. In the first section of the pamphlet, some of the basic concepts of…

King, Pat; Landahl, John

188

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

189

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

190

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

191

Incorporating parametric uncertainty into population viability analysis models  

USGS Publications Warehouse

Uncertainty in parameter estimates from sampling variation or expert judgment can introduce substantial uncertainty into ecological predictions based on those estimates. However, in standard population viability analyses, one of the most widely used tools for managing plant, fish and wildlife populations, parametric uncertainty is often ignored in or discarded from model projections. We present a method for explicitly incorporating this source of uncertainty into population models to fully account for risk in management and decision contexts. Our method involves a two-step simulation process where parametric uncertainty is incorporated into the replication loop of the model and temporal variance is incorporated into the loop for time steps in the model. Using the piping plover, a federally threatened shorebird in the USA and Canada, as an example, we compare abundance projections and extinction probabilities from simulations that exclude and include parametric uncertainty. Although final abundance was very low for all sets of simulations, estimated extinction risk was much greater for the simulation that incorporated parametric uncertainty in the replication loop. Decisions about species conservation (e.g., listing, delisting, and jeopardy) might differ greatly depending on the treatment of parametric uncertainty in population models.

McGowan, Conor P.; Runge, Michael C.; Larson, Michael A.

2011-01-01

192

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

193

Nonlinear PI controllers for continuous bioreactors using population balance models.  

PubMed

Continuous bioreactors are critical unit operations in many biological systems, but the unique modeling is very complicated due to the underlying biochemical reactions and the distributed properties of cell population. The scope of this paper considers a popular modeling method for microbial cell cultures by population balance equation models, and the control objective aims to attenuate undesired oscillations appeared in the nonlinear distributed parameter system. In view of pursuing the popular/practical control configuration and the lack of on-line sensors, an approximate technique by exploiting the "pseudo-steady-state" approach constructs a simple nonlinear control model. Through an off-line estimation mechanism for the system having self-oscillating behavior, two kinds of nonlinear PI configurations are developed. Closed-loop simulation results have confirmed that the regulatory and tracking performances of the control system proposed are good. PMID:16200392

Wu, Wei; Chang, Haw-Yuan

2005-11-01

194

Parsimonious snow model explains reindeer population dynamics and ranging behavior  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

195

Population clinical pharmacology of children: modelling covariate effects  

Microsoft Academic Search

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

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

2006-01-01

196

CFD modeling of bubble columns flows: implementation of population balance  

Microsoft Academic Search

The Bubble Population Balance Equation is implemented both in the two-fluid model and in the Algebraic Slip Mixture Model. Two and three-dimensional numerical simulations of two-phase (air–water) and pseudo-two-phase (air–Therminol-Glass beads) transient flows are performed for laboratory scale bubble columns of two different diameters operated over a range of superficial gas velocities (8 to 20cm\\/s) in the churn turbulent regime.

P. Chen; J. Sanyal; M. P. Dudukovic

2004-01-01

197

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

198

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

199

Grazing by rotifers and crustacean zooplankton on nanoplanktonic protists  

Microsoft Academic Search

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

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

1994-01-01

200

Factors that regulate the zooplankton community structure of a turbid,  

E-print Network

wetland of Lake Ontario. Samples were from several habitat types including open water, vegetated areasFactors that regulate the zooplankton community structure of a turbid, hypereutrophic Great Lakes, fast-flow areas, and a sewage lagoon. Mean seasonal densities ranged from 17 individuals/L (5 µg

McMaster University

201

FORAGE FISH AND ZOOPLANKTON COMMUNITY COMPOSITION IN WESTERN LAKE SUPERIOR  

EPA Science Inventory

We assessed the abundance, size, and species composition of the fish and zooplankton communities of western Lake Superior during 1996 and 1997. Data were analyzed for 3 ecoregions (Duluth-Superior (1), Apostle Islands (2), Minnesota coast (3) differing in lake bathymetry, phsiodo...

202

A physical context for gelatinous zooplankton aggregations: a review  

Microsoft Academic Search

The magnitude and extent of jellyfish blooms are influenced not only by the biology and behavior of the animal, but also by the geographic setting and physical environment. Hydrography alone is often thought to cause or favor gelatinous zooplankton aggregations, however, it is clear that interactions between biology of the animal and physics of the water are very important sources

William M. Graham; Fransesc Pagès; William M. Hamner

2001-01-01

203

Variation in zooplankton species-area curves between regions of  

E-print Network

Variation in zooplankton species- area curves between regions of differing land use Jose Serna and will not in a undeveloped region #12;Methods Will species-area curves differ between developed and undeveloped areas · Land use may affect species-area curves · If land use had no effect, then we might anticipate similar

204

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

205

Impact of turbulence on riverine zooplankton: a mesocosm experiment  

E-print Network

.S.A. Department of Biology, University of Louisville, Louisville, KY, U.S.A. Kansas Biological Survey and Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, U.S.A. SUMMARY 1. With increases in river discharge over time and space, zooplankton generally encounter increased turbulence

Thorp, James H.

206

Respiratory rates of migrating zooplankton in the natural habitat  

Microsoft Academic Search

Rates of oxygen consumption by zooplankton in Cayuga Lake were measured when the lake was stratified. The effects of temperature, pressure, and light wcrc examined. Animals from the epilimnion, mostly cladocerans, and from the hypolimnion, mostly copepods, respired at similar rates in their rcspectivc habitats. When the animals were placed in the same habitats, copepods from the hypolimnion hacl the

JOHN W. BISHOP

1968-01-01

207

Automated sizing, counting and identification of zooplankton by pattern recognition  

Microsoft Academic Search

A computerized system was developed to automate the analysis of zooplankton samples. Classification to major taxonomic group was based on discriminant analysis of morphological features. Images were generated either from preserved organisms or from silhouette photographs. The latter technique simplified large-scale sample storage. Accuracy of correct classification, among organisms regularly occurring in New England coastal waters, exceeded 90%. Critical problems

H. P. Jeffries; M. S. Berman; A. D. Poularikas; C. Katsinis; I. Melas; K. Sherman; L. Bivins

1984-01-01

208

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

209

Mechanical reaction-diffusion model for bacterial population dynamics  

E-print Network

The effect of mechanical interaction between cells on the spreading of bacterial population was investigated in one-dimensional space. A nonlinear reaction-diffusion equation has been formulated as a model for this dynamics. In this model, the bacterial cells are treated as the rod-like particles that interact, when contacting each other, through the hard-core repulsion. The repulsion introduces the exclusion process that causes the fast diffusion in bacterial population at high density. The propagation of the bacterial density as the traveling wave front in long time behavior has been analyzed. The analytical result reveals that the front speed is enhanced by the exclusion process---and its value depends on the packing fraction of cell. The numerical solutions of the model have been solved to confirm this prediction.

Ngamsaad, Waipot

2015-01-01

210

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

211

ORDEM2010 and MASTER-2009 Modeled Small Debris Population Comparison  

NASA Technical Reports Server (NTRS)

The latest versions of the two premier orbital debris engineering models, NASA s ORDEM2010 and ESA s MASTER-2009, have been publicly released. Both models have gone through significant advancements since inception, and now represent the state-of-the-art in orbital debris knowledge of their respective agencies. The purpose of these models is to provide satellite designers/operators and debris researchers with reliable estimates of the artificial debris environment in near-Earth orbit. The small debris environment within the size range of 1 mm to 1 cm is of particular interest to both human and robotic spacecraft programs. These objects are much more numerous than larger trackable debris but are still large enough to cause significant, if not catastrophic, damage to spacecraft upon impact. They are also small enough to elude routine detection by existing observation systems (radar and telescope). Without reliable detection the modeling of these populations has always coupled theoretical origins with supporting observational data in different degrees. This paper details the 1 mm to 1 cm orbital debris populations of both ORDEM2010 and MASTER-2009; their sources (both known and presumed), current supporting data and theory, and methods of population analysis. Fluxes on spacecraft for chosen orbits are also presented and discussed within the context of each model.

Krisko, Paula H.; Flegel, S.

2010-01-01

212

Population.  

ERIC Educational Resources Information Center

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

International Planned Parenthood Federation, London (England).

213

Logistic Growth The logistic equation is a model of limited population growth. The exponential growth model  

E-print Network

9­28­1998 Logistic Growth The logistic equation is a model of limited population growth and K grow almost exponentially at first. Growth slows as N nears the limiting population K. As t !1, N. The exponential growth model dN dt = aN; a ? 0: is not bad in situations where resources are unlimited

Ikenaga, Bruce

214

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

NASA Astrophysics Data System (ADS)

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

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

2005-09-01

215

Population effects of increased climate variation  

PubMed Central

Global circulation models predict and numerous observations confirm that anthropogenic climate change has altered high-frequency climate variability. However, it is not yet well understood how changing patterns of environmental variation will affect wildlife population dynamics and other ecological processes. Theory predicts that a population's long-run growth rate is diminished and the chance of population extinction is increased as environmental variation increases. This results from the fact that population growth is a multiplicative process and that long-run population growth rate is the geometric mean of growth rates over time, which is always less than the arithmetic mean. However, when population growth rates for unstructured populations are related nonlinearly to environmental drivers, increasing environmental variation can increase a population's long-run growth rate. This suggests that patterns of environmental variation associated with different aspects of climate change may affect population dynamics in different ways. Specifically, increasing variation in rainfall might result in diminished long-run growth rates for many animal species while increasing variation in temperature might result in increased long-run growth rates. While the effect of rainfall is theoretically well understood and supported by data, the hypothesized effect of temperature is not. Here, I analyse two datasets to study the effect of fluctuating temperatures on growth rates of zooplankton. Results are consistent with the prediction that fluctuating temperatures should increase long-run growth rates and the frequency of extreme demographic events. PMID:16096095

Drake, John M

2005-01-01

216

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

217

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

218

A test for deviation from island-model population structure.  

PubMed

The neutral island model forms the basis for several estimation models that relate patterns of genetic structure to microevolutionary processes. Estimates of gene flow are often based on this model and may be biased when the model's assumptions are violated. An appropriate test for violations is to compare FST scores for individual loci to a null distribution based on the average FST taken over multiple loci. A parametric bootstrap method is described here based on Wright's beta-distribution to generate null distributions of FST for each locus. These null distributions account for error introduced by sampling populations, individuals and loci, and also biological sources of error, including variable alleles/locus and inbreeding. Confidence limits can be obtained directly from these distributions. Significant deviations from the island model may be the result of selection, deviations from the island model's migration pattern, nonequilibrium conditions, or other deviations from island-model assumptions. Only strong biases are likely to be detected because of the inherently large sampling variation of FST. Nevertheless, a coefficient, Nb, describing bias in the spread of the beta-distribution in units comparable to the gene flow parameter, Nm, can be obtained for each locus. In samples from populations of the butterfly Coenonympha tullia, the loci Idh-1, Mdh-1, Pgi and Pgm showed significantly lower FST than expected. PMID:12753211

Porter, Adam H

2003-04-01

219

Synergistic Interaction between Selective Drugs in Cell Populations Models  

PubMed Central

The design of selective drugs and combinatorial drug treatments are two of the main focuses in modern pharmacology. In this study we use a mathematical model of chimeric ligand-receptor interaction to show that the combination of selective drugs is synergistic in nature, providing a way to gain optimal selective potential at reduced doses compared to the same drugs when applied individually. We use a cell population model of proliferating cells expressing two different amounts of a target protein to show that both selectivity and synergism are robust against variability and heritability in the cell population. The reduction in the total drug administered due to the synergistic performance of the selective drugs can potentially result in reduced toxicity and off-target interactions, providing a mechanism to improve the treatment of cell-based diseases caused by aberrant gene overexpression, such as cancer and diabetes. PMID:25671700

Doldán-Martelli, Victoria; Míguez, David G.

2015-01-01

220

Consequences of population models for the dynamics of food chains.  

PubMed

A class of bioenergetic ecological models is studied for the dynamics of food chains with a nutrient at the base. A constant influx rate of the nutrient and a constant efflux rate for all trophic levels is assumed. Starting point is a simple model where prey is converted into predator with a fixed efficiency. This model is extended by the introduction of maintenance and energy reserves at all trophic levels, with two state variables for each trophic level, biomass and reserve energy. Then the dynamics of each population are described by two ordinary differential equations. For all models the bifurcation diagram for the bi-trophic food chain is simple. There are three important regions; a region where the predator goes to extinction, a region where there is a stable equilibrium and a region where a stable limit cycle exists. Bifurcation diagrams for tritrophic food chains are more complicated. Flip bifurcation curves mark regions where complex dynamic behaviour (higher periodic limit cycles as well as chaotic attractors) can occur. We show numerically that Shil'nikov homoclinic orbits to saddle-focus equilibria exists. The codimension 1 continuations of these orbits form a 'skeleton' for a cascade of flip and tangent bifurcations. The bifurcation analysis facilitates the study of the consequences of the population model for the dynamic behaviour of a food chain. Although the predicted transient dynamics of a food chain may depend sensitively on the underlying model for the populations, the global picture of the bifurcation diagram for the different models is about the same. PMID:9825635

Kooi, B W; Boer, M P; Kooijman, S A

1998-11-01

221

Ecological Modelling 147 (2002) 291307 The kin facilitation hypothesis for red grouse population  

E-print Network

Ecological Modelling 147 (2002) 291­307 The kin facilitation hypothesis for red grouse population grouse population cycles to the formation of spatial assemblages comprising related territory holders clusters; Kinship; Ordinary differential equations; Population cycles; Red grouse (Lagopus lagopus scoticus

Lambin, Xavier

222

Wave trains in a model of gypsy moth population dynamics  

NASA Astrophysics Data System (ADS)

A recent model of gypsy moth [Lymantria dispar (Lepidoptera: Lymantriidae)] populations led to the observation of traveling waves in a one-dimensional spatial model. In this work, these waves are studied in more detail and their nature investigated. It was observed that when there are no spatial effects the model behaves chaotically under certain conditions. Under the same conditions, when diffusion is allowed, traveling waves develop. The biomass densities involved in the model, when examined at one point in the spatial domain, are found to correspond to a limit cycle lying on the surface of the chaotic attractor of the spatially homogeneous model. Also observed are wave trains that have modulating maxima, and which when examined at one point in the spatial domain show a quasiperiodic temporal behavior. This complex behavior is determined to be due to the interaction of the traveling wave and the chaotic background dynamics.

Wilder, J. W.; Vasquez, D. A.; Christie, I.; Colbert, J. J.

1995-12-01

223

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

224

A population model of chaparral vegetation response to frequent wildfires.  

PubMed

The recent increase in wildfire frequency in the Santa Monica Mountains (SMM) may substantially impact plant community structure. Species of Chaparral shrubs represent the dominant vegetation type in the SMM. These species can be divided into three life history types according to their response to wildfires. Nonsprouting species are completely killed by fire and reproduce by seeds that germinate in response to a fire cue, obligate sprouting species survive by resprouting from dormant buds in a root crown because their seeds are destroyed by fire, and facultative sprouting species recover after fire both by seeds and resprouts. Based on these assumptions, we developed a set of nonlinear difference equations to model each life history type. These models can be used to predict species survivorship under varying fire return intervals. For example, frequent fires can lead to localized extinction of nonsprouting species such as Ceanothus megacarpus while several facultative sprouting species such as Ceanothus spinosus and Malosma (Rhus) laurina will persist as documented by a longitudinal study in a biological preserve in the SMM. We estimated appropriate parameter values for several chaparral species using 25 years of data and explored parameter relationships that lead to equilibrium populations. We conclude by looking at the survival strategies of these three species of chaparral shrubs under varying fire return intervals and predict changes in plant community structure under fire intervals of short return. In particular, our model predicts that an average fire return interval of greater than 12 years is required for 50 % of the initial Ceanothus megacarpus population and 25 % of the initial Ceanothus spinosus population to survive. In contrast, we predict that the Malosma laurina population will have 90 % survivorship for an average fire return interval of at least 6 years. PMID:24091781

Lucas, Timothy A; Johns, Garrett; Jiang, Wancen; Yang, Lucie

2013-12-01

225

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

226

Information-theoretic model selection and model averaging for closed-population capture-recapture studies  

USGS Publications Warehouse

Specification of an appropriate model is critical to valid stalistical inference. Given the "true model" for the data is unknown, the goal of model selection is to select a plausible approximating model that balances model bias and sampling variance. Model selection based on information criteria such as AIC or its variant AICc, or criteria like CAIC, has proven useful in a variety of contexts including the analysis of open-population capture-recapture data. These criteria have not been intensively evaluated for closed-population capture-recapture models, which are integer parameter models used to estimate population size (N), and there is concern that they will not perform well. To address this concern, we evaluated AIC, AICc, and CAIC model selection for closed-population capture-recapture models by empirically assessing the quality of inference for the population size parameter N. We found that AIC-, AICc-, and CAIC-selected models had smaller relative mean squared errors than randomly selected models, but that confidence interval coverage on N was poor unless unconditional variance estimates (which incorporate model uncertainty) were used to compute confidence intervals. Overall, AIC and AICc outperformed CAIC, and are preferred to CAIC for selection among the closed-population capture-recapture models we investigated. A model averaging approach to estimation, using AIC. AICc, or CAIC to estimate weights, was also investigated and proved superior to estimation using AIC-, AICc-, or CAIC-selected models. Our results suggested that, for model averaging, AIC or AICc. should be favored over CAIC for estimating weights.

Stanley, T.R.; Burnham, K.P.

1998-01-01

227

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

228

Knowledge epidemics and population dynamics models for describing idea diffusion  

E-print Network

The diffusion of ideas is often closely connected to the creation and diffusion of knowledge and to the technological evolution of society. Because of this, knowledge creation, exchange and its subsequent transformation into innovations for improved welfare and economic growth is briefly described from a historical point of view. Next, three approaches are discussed for modeling the diffusion of ideas in the areas of science and technology, through (i) deterministic, (ii) stochastic, and (iii) statistical approaches. These are illustrated through their corresponding population dynamics and epidemic models relative to the spreading of ideas, knowledge and innovations. The deterministic dynamical models are considered to be appropriate for analyzing the evolution of large and small societal, scientific and technological systems when the influence of fluctuations is insignificant. Stochastic models are appropriate when the system of interest is small but when the fluctuations become significant for its evolution...

Vitanov, Nikolay K

2012-01-01

229

Modelling Lipid Competition Dynamics in Heterogeneous Protocell Populations  

PubMed Central

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

230

Avoidance of towed nets by zooplankton  

Microsoft Academic Search

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

ABRAHAM FLEMINGER; ROBERT I. CLUTTER

1965-01-01

231

Fast algorithm for population-based protein structural model analysis  

PubMed Central

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

232

Modeling the population dynamics of phytoplankton in lacustrine ecosystems  

NASA Astrophysics Data System (ADS)

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

Leiterman, Terry Jo

2011-11-01

233

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

234

Interacting trophic forcing and the population dynamics of herring.  

PubMed

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

Lindegren, Martin; Ostman, Orjan; Gårdmark, Anna

2011-07-01

235

Spatial and temporal variation in mercury bioaccumulation by zooplankton in Lake Champlain (North America).  

PubMed

Trophic transfer of Hg across lakes within a region has been related to multiple environmental factors, but the nature of these relationships across distinct basins within individual large lakes is unknown. We investigated Hg bioaccumulation in zooplankton in basins of differing trophic status in Lake Champlain (Vermont, USA) to determine the strongest predictors of Hg bioaccumulation. Zooplankton were sampled in Malletts Bay (oligotrophic) and Missisquoi Bay (eutrophic) in 2005-2008. Zooplankton in the eutrophic basin had lower concentrations of total Hg and MeHg than those in the oligotrophic basin in all years but 2007, when no bloom occurred in Missisquoi. In addition, Hg concentrations in seston and small zooplankton, sampled during 2009 at 12 sites spanning the lake, decreased with increasing phytoplankton and zooplankton biomass. Thus, Hg bioaccumulation in zooplankton across basins in Lake Champlain is related to trophic status, as observed previously in multiple lake studies. PMID:21995871

Chen, Celia; Kamman, Neil; Williams, Jason; Bugge, Deenie; Taylor, Vivien; Jackson, Brian; Miller, Eric

2012-02-01

236

Spatial and temporal variation in mercury bioaccumulation by zooplankton in Lake Champlain (North America)  

PubMed Central

Trophic transfer of Hg across lakes within a region has been related to multiple environmental factors, but the nature of these relationships across distinct basins within individual large lakes is unknown. We investigated Hg bioaccumulation in zooplankton in basins of differing trophic status in Lake Champlain (Vermont, USA) to determine the strongest predictors of Hg bioaccumulation. Zooplankton were sampled in Malletts Bay (oligotrophic) and Missisquoi Bay (eutrophic) in 2005–2008. Zooplankton in the eutrophic basin had lower concentrations of total Hg and MeHg than those in the oligotrophic basin in all years but 2007, when no bloom occurred in Missisquoi. In addition, Hg concentrations in seston and small zooplankton, sampled during 2009 at 12 sites spanning the lake, decreased with increasing phytoplankton and zooplankton biomass. Thus, Hg bioaccumulation in zooplankton across basins in Lake Champlain is related to trophic status, as observed previously in multiple lake studies. PMID:21995871

Kamman, Neil; Williams, Jason; Bugge, Deenie; Taylor, Vivien; Jackson, Brian; Miller, Eric

2012-01-01

237

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

238

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

239

Can tropical freshwater zooplankton graze efficiently on cyanobacteria?  

Microsoft Academic Search

Zooplankton may at times graze cyanobacteria. However, their top-down effects are considered to be low, particularly in tropical\\u000a regions dominated by small-size grazers that may be unable to consume efficiently filamentous or colonial species. Recently,\\u000a cyanobacteria blooms were reported in the Senegal River hydrosystem. We conducted feeding experiments to assess the ability\\u000a of copepods (Pseudodiaptomus hessei and Mesocyclops ogunnus), cladocerans

Samba Kâ; Juana Mireya Mendoza-Vera; Marc Bouvy; Gisèle Champalbert; Rose N’Gom-Kâ; Marc Pagano

240

Type of suspended clay influences zooplankton response to phosphorus loading  

Microsoft Academic Search

The effects on zooplankton community structure of P loading and two different kinds of suspended sediments were tested in a small lake. Limnocorrals were used in a complete, triplicated, six- treatment-block design. Treatments were loading with P, kaolinitic clay (IQ, K+P, montmorillonitic clay (M), and M+P plus a control without additions. P fertilization caused blooms of blue-green bacteria and resulted

BENJAMIN E. CUKER; LEON HUDSON

1992-01-01

241

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

242

Flow disturbances generated by feeding and swimming zooplankton.  

PubMed

Interactions between planktonic organisms, such as detection of prey, predators, and mates, are often mediated by fluid signals. Consequently, many plankton predators perceive their prey from the fluid disturbances that it generates when it feeds and swims. Zooplankton should therefore seek to minimize the fluid disturbance that they produce. By means of particle image velocimetry, we describe the fluid disturbances produced by feeding and swimming in zooplankton with diverse propulsion mechanisms and ranging from 10-µm flagellates to greater than millimeter-sized copepods. We show that zooplankton, in which feeding and swimming are separate processes, produce flow disturbances during swimming with a much faster spatial attenuation (velocity u varies with distance r as u ? r(-3) to r(-4)) than that produced by zooplankton for which feeding and propulsion are the same process (u ? r(-1) to r(-2)). As a result, the spatial extension of the fluid disturbance produced by swimmers is an order of magnitude smaller than that produced by feeders at similar Reynolds numbers. The "quiet" propulsion of swimmers is achieved either through swimming erratically by short-lasting power strokes, generating viscous vortex rings, or by "breast-stroke swimming." Both produce rapidly attenuating flows. The more "noisy" swimming of those that are constrained by a need to simultaneously feed is due to constantly beating flagella or appendages that are positioned either anteriorly or posteriorly on the (cell) body. These patterns transcend differences in size and taxonomy and have thus evolved multiple times, suggesting a strong selective pressure to minimize predation risk. PMID:25071196

Kiørboe, Thomas; Jiang, Houshuo; Gonçalves, Rodrigo Javier; Nielsen, Lasse Tor; Wadhwa, Navish

2014-08-12

243

Flow disturbances generated by feeding and swimming zooplankton  

PubMed Central

Interactions between planktonic organisms, such as detection of prey, predators, and mates, are often mediated by fluid signals. Consequently, many plankton predators perceive their prey from the fluid disturbances that it generates when it feeds and swims. Zooplankton should therefore seek to minimize the fluid disturbance that they produce. By means of particle image velocimetry, we describe the fluid disturbances produced by feeding and swimming in zooplankton with diverse propulsion mechanisms and ranging from 10-µm flagellates to greater than millimeter-sized copepods. We show that zooplankton, in which feeding and swimming are separate processes, produce flow disturbances during swimming with a much faster spatial attenuation (velocity u varies with distance r as u ? r?3 to r?4) than that produced by zooplankton for which feeding and propulsion are the same process (u ? r?1 to r?2). As a result, the spatial extension of the fluid disturbance produced by swimmers is an order of magnitude smaller than that produced by feeders at similar Reynolds numbers. The “quiet” propulsion of swimmers is achieved either through swimming erratically by short-lasting power strokes, generating viscous vortex rings, or by “breast-stroke swimming.” Both produce rapidly attenuating flows. The more “noisy” swimming of those that are constrained by a need to simultaneously feed is due to constantly beating flagella or appendages that are positioned either anteriorly or posteriorly on the (cell) body. These patterns transcend differences in size and taxonomy and have thus evolved multiple times, suggesting a strong selective pressure to minimize predation risk. PMID:25071196

Kiørboe, Thomas; Jiang, Houshuo; Gonçalves, Rodrigo Javier; Nielsen, Lasse Tor; Wadhwa, Navish

2014-01-01

244

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

245

Effect of animal orientation on acoustic estimates of zooplankton properties  

Microsoft Academic Search

It is well known that the behavior of zooplankton and, in particular, their orientation distribution dramatically affects the level of backscattered acoustic energy. As a result, interpretation of acoustic survey data in the ocean is subject to error. In order to quantify these effects, laboratory data from two important classes of animals were collected. The data involved broad-band (350-650 kHz)

Joseph D. Warren; Timothy K. Stanton; Duncan E. McGehee; Dezhang Chu

2002-01-01

246

Mercury biomagnification in marine zooplankton food webs in Hudson Bay.  

PubMed

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

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

2012-12-01

247

Dynamics of lake herring (Coregonus artedi) reactive volume for different crustacean zooplankton  

Microsoft Academic Search

Lake herring (Coregonus artedi) can drastically alter the zooplankton community of a lake through size-selective predation.\\u000a I studied the first step in the predation sequence, reaction to prey, for different zooplankton taxa by lake herring. Reactive\\u000a distance was significantly shorter for smaller zooplankton taxa (p < 0.0001). Reactive volume was calculated from measured\\u000a distances and angles of elevation and bearing.

Jason Link

1998-01-01

248

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

Microsoft Academic Search

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 o0.4 to 78mg\\/L, and concentrations in

Steven J. Hamilton; Kevin J. Buhl; Fern A. Bullard; Susan F. McDonald

249

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

250

USING MODELS TO EXTRAPOLATE POPULATION-LEVEL EFFECTS FROM LABORATORY TOXICITY TESTS IN SUPPORT OF POPULATION RISK ASSESSMENTS  

EPA Science Inventory

Using models to extrapolate population-level effects from laboratory toxicity tests in support of population risk assessments. Munns, W.R., Jr.*, Anne Kuhn, Matt G. Mitro, and Timothy R. Gleason, U.S. EPA ORD NHEERL, Narragansett, RI, USA. Driven in large part by management goa...

251

The model of fungal population dynamics affected by nystatin  

NASA Astrophysics Data System (ADS)

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

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

252

Mathematical modeling of glassy-winged sharpshooter population.  

PubMed

Pierce's disease (PD) is a fatal disease of grapevines which results from an infection by the plant pathogen Xyllela fastidiosa. This bacterium grows in the xylem (water-conducting) vessels of the plant blocking movement of water. PD can kill vines in one year and poses a serious threat to both the California and the expanding Texas wine industries. Bacteria are vectored from one vine to the next by a number of xylem feeding insect species. Of these, the Glassy-winged Sharpshooter (GWSS) is considered to be the primary xylem feeding insect in Texas vineyards. An extensive database of the xylem-feeding population frequencies was collected by USDA-APHIS for Texas vineyards over multiple years. This project focused on a subset of data, GWSS frequencies within 25 vineyards in Edwards Plateau located in central Texas. The proposed model investigates the natural population dynamics and the decline in GWSS, likely the result of pest management campaigns on the insects within the region. The model is a delay Gompertz differential equation with harvesting and immigration terms, and we use the data to estimate the model parameters. PMID:24506556

Yoon, Jeong-Mi; Hrynkiv, Volodymyr; Morano, Lisa; Nguyen, Anh Tuan; Wilder, Sara; Mitchell, Forrest

2014-06-01

253

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

254

Population pharmacokinetics modeling of levetiracetam in Chinese children with epilepsy  

PubMed Central

Aim: To establish a population pharmacokinetics (PPK) model of levetiracetam in Chinese children with epilepsy. Methods: A total of 418 samples from 361 epileptic children in Peking University First Hospital were analyzed. These patients were divided into two groups: the PPK model group (n=311) and the PPK validation group (n=50). Levetiracetam concentrations were determined by HPLC. The PPK model of levetiracetam was established using NONMEM, according to a one-compartment model with first-order absorption and elimination. To validate the model, the mean prediction error (MPE), mean squared prediction error (MSPE), root mean-squared prediction error (RMSPE), weight residues (WRES), and the 95% confidence intervals (95% CI) were calculated. Results: A regression equation of the basic model of levetiracetam was obtained, with clearance (CL/F)=0.988 L/h, volume of distribution (V/F)=12.3 L, and Ka=1.95 h?1. The final model was as follows: Ka=1.56 h?1, V/F=12.1 (L), CL/F=1.04×(WEIG/25)0.583 (L/h). For the basic model, the MPE, MSPE, RMSPE, WRES, and the 95%CI were 9.834 (?0.587–197.720), 50.919 (0.012–1286.429), 1.680 (0.021–34.184), and 0.0621 (?1.100–1.980). For the final model, the MPE, MSPE, RMSPE, WRES, and the 95% CI were 0.199 (?0.369–0.563), 0.002082 (0.00001–0.01054), 0.0293 (0.001?0.110), and 0.153 (?0.030–1.950). Conclusion: A one-compartment model with first-order absorption adequately described the levetiracetam concentrations. Body weight was identified as a significant covariate for levetiracetam clearance in this study. This model will be valuable to facilitate individualized dosage regimens. PMID:22669118

Wang, Ying-hui; Wang, Li; Lu, Wei; Shang, De-wei; Wei, Min-ji; Wu, Ye

2012-01-01

255

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

256

Math 114 Class 23 Fall 2005 Population Models and Qualitative Analysis  

E-print Network

the population? How well do you think this model would work in capturing the bacterial growth over time? What that track the growth of a population over time; the SIR model we examined some weeks ago is such a model of population growth is known as both exponential growth and Malthus growth. Sketch the function dB/dt versus B

Buckmire, Ron

257

An isotopic (?14C, ?13C, and ?15N) investigation of particulate organic matter and zooplankton biomass in Lake Superior and across a size-gradient of aquatic systems  

NASA Astrophysics Data System (ADS)

Food webs in aquatic systems can be supported both by carbon from recent local primary productivity and by carbon subsidies, such as material from terrestrial ecosystems or past in situ primary productivity. The importance of these subsidies to respiration and biomass production remains a topic of debate, but they may play major roles in determining the fate of organic carbon and in sustaining upper trophic levels, including those contributing to economically important fisheries. While some studies have reported that terrigenous organic carbon supports disproportionately high zooplankton production, others have suggested that phytoplankton preferentially supports zooplankton production in aquatic ecosystems. Here we apply natural abundance radiocarbon (?14C) and stable isotope (?13C, ?15N) analyses to show that zooplankton in Lake Superior selectively incorporate recently-fixed, locally-produced (autochthonous) organic carbon even though other carbon sources are readily available. Estimates from Bayesian isotopic modeling based on ?14C values show that the average lakewide median contributions of recent in situ algal, terrestrial, sedimentary, and bacterial organic carbon to the bulk POM in Lake Superior were 23%, 28%, 15%, and 25%, respectively. However, the isotopic modeling estimates show that recent in situ production (algae) contributed a disproportionately large amount (median, 40-89%) of the carbon in zooplankton biomass in Lake Superior. Although terrigenous organic carbon and old organic carbon from resuspended sediments were significant portions of the available basal food resources, these contributed only a small amount to zooplankton biomass (average lakewide median, 2% from sedimentary organic carbon and 9% from terrigenous organic carbon). Comparison of zooplankton food sources based on their radiocarbon composition showed that terrigenous organic carbon was relatively more important in rivers and small lakes, and the proportion of terrestrially-derived material used by zooplankton correlated with the hydrologic residence time and the ratio of basin area to water surface area.

Zigah, P. K.; Minor, E. C.; Werne, J. P.; McCallister, S. Leigh

2012-04-01

258

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

NASA Astrophysics Data System (ADS)

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

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

2002-09-01

259

Population balance models: a useful complementary modelling framework for future WWTP modelling.  

PubMed

Population balance models (PBMs) represent a powerful modelling framework for the description of the dynamics of properties that are characterised by distributions. This distribution of properties under transient conditions has been demonstrated in many chemical engineering applications. Modelling efforts of several current and future unit processes in wastewater treatment plants could potentially benefit from this framework, especially when distributed dynamics have a significant impact on the overall unit process performance. In these cases, current models that rely on average properties cannot sufficiently capture the true behaviour and even lead to completely wrong conclusions. Examples of distributed properties are bubble size, floc size, crystal size or granule size. In these cases, PBMs can be used to develop new knowledge that can be embedded in our current models to improve their predictive capability. Hence, PBMs should be regarded as a complementary modelling framework to biokinetic models. This paper provides an overview of current applications, future potential and limitations of PBMs in the field of wastewater treatment modelling, thereby looking over the fence to other scientific disciplines. PMID:25633937

Nopens, Ingmar; Torfs, Elena; Ducoste, Joel; Vanrolleghem, Peter A; Gernaey, Krist V

2015-01-01

260

MULTISCALE MODELS OF TAXIS-DRIVEN PATTERNING IN BACTERIAL POPULATIONS  

PubMed Central

Spatially-distributed populations of various types of bacteria often display intricate spatial patterns that are thought to result from the cellular response to gradients of nutrients or other attractants. In the past decade a great deal has been learned about signal transduction, metabolism and movement in E. coli and other bacteria, but translating the individual-level behavior into population-level dynamics is still a challenging problem. However, this is a necessary step because it is computationally impractical to use a strictly cell-based model to understand patterning in growing populations, since the total number of cells may reach 1012 - 1014 in some experiments. In the past phenomenological equations such as the Patlak-Keller-Segel equations have been used in modeling the cell movement that is involved in the formation of such patterns, but the question remains as to how the microscopic behavior can be correctly described by a macroscopic equation. Significant progress has been made for bacterial species that employ a “run-and-tumble” strategy of movement, in that macroscopic equations based on simplified schemes for signal transduction and turning behavior have been derived [14, 15]. Here we extend previous work in a number of directions: (i) we allow for time-dependent signals, which extends the applicability of the equations to natural environments, (ii) we use a more general turning rate function that better describes the biological behavior, and (iii) we incorporate the effect of hydrodynamic forces that arise when cells swim in close proximity to a surface. We also develop a new approach to solving the moment equations derived from the transport equation that does not involve closure assumptions. Numerical examples show that the solution of the lowest-order macroscopic equation agrees well with the solution obtained from a Monte Carlo simulation of cell movement under a variety of temporal protocols for the signal. We also apply the method to derive equations of chemotactic movement that are governed by multiple chemotactic signals. PMID:19784399

XUE, CHUAN; OTHMER, HANS G.

2009-01-01

261

Mathematical model of temephos resistance in Aedes aegypti mosquito population  

NASA Astrophysics Data System (ADS)

Aedes aegypti is the main vector of dengue disease in many tropical and sub-tropical countries. Dengue became major public concern in these countries due to the unavailability of vaccine or drugs for dengue disease in the market. Hence, the only way to control the spread of DF and DHF is by controlling the vectors carrying the disease, for instance with fumigation, temephos or genetic manipulation. Many previous studies conclude that Aedes aegypti may develop resistance to many kind of insecticide, including temephos. Mathematical model for transmission of temephos resistance in Aedes aegypti population is discussed in this paper. Nontrivial equilibrium point of the system and the corresponding existence are shown analytically. The model analysis have shown epidemiological trends condition that permits the coexistence of nontrivial equilibrium is given analytically. Numerical results are given to show parameter sensitivity and some cases of worsening effect values for illustrating possible conditions in the field.

Aldila, D.; Nuraini, N.; Soewono, E.; Supriatna, A. K.

2014-03-01

262

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

263

Nonlinear Model-based Control of a Semi-industrial Batch Crystallizer Using a Population Balance Modeling  

E-print Network

Nonlinear Model-based Control of a Semi-industrial Batch Crystallizer Using a Population Balance-based control approach for optimal operation of industrial batch crystallizers. A full population balance model on the discretization coarseness of the population balance model. The control performance can be greatly deteriorated

Van den Hof, Paul

264

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

265

Yunnan-III models for evolutionary population synthesis  

NASA Astrophysics Data System (ADS)

We build the Yunnan-III evolutionary population synthesis (EPS) models by using the mesa stellar evolution code, BaSeL stellar spectra library and the initial mass functions (IMFs) of Kroupa and Salpeter, and present colours and integrated spectral energy distributions (ISEDs) of solar-metallicity stellar populations (SPs) in the range of 1 Myr to 15 Gyr. The main characteristic of the Yunnan-III EPS models is the usage of a set of self-consistent solar-metallicity stellar evolutionary tracks (the masses of stars are from 0.1 to 100 M?). This set of tracks is obtained by using the state-of-the-art mesa code. mesa code can evolve stellar models through thermally pulsing asymptotic giant branch (TP-AGB) phase for low- and intermediate-mass stars. By comparisons, we confirm that the inclusion of TP-AGB stars makes the V - K, V - J and V - R colours of SPs redder and the infrared flux larger at ages log(t/yr) ? 7.6 [the differences reach the maximum at log(t/yr) ˜ 8.6, ˜0.5-0.2 mag for colours, approximately two times for K-band flux]. We also find that the colour-evolution trends of Model with-TPAGB at intermediate and large ages are similar to those from the starburst99 code, which employs the Padova-AGB stellar library, BaSeL spectral library and the Kroupa IMF. At last, we compare the colours with the other EPS models comprising TP-AGB stars (such as CB07, M05, V10 and POPSTAR), and find that the B - V colour agrees with each other but the V-K colour shows a larger discrepancy among these EPS models [˜1 mag when 8 ? log(t/yr) ? 9]. The stellar evolutionary tracks, isochrones, colours and ISEDs can be obtained on request from the first author or from our website (http://www1.ynao.ac.cn/~zhangfh/). Using the isochrones, you can build your EPS models. Now the format of stellar evolutionary tracks is the same as that in the starburst99 code; you can put them into the starburst99 code and get the SP's results. Moreover, the colours involving other passbands or on other systems (e.g. HST F439W - F555W colour on AB system) can also be obtained on request.

Zhang, F.; Li, L.; Han, Z.; Zhuang, Y.; Kang, X.

2013-02-01

266

Stochastic stable population growth in integral projection models: theory and application  

Microsoft Academic Search

Stochastic matrix projection models are widely used to model age- or stage-structured populations with vital rates that fluctuate\\u000a randomly over time. Practical applications of these models rest on qualitative properties such as the existence of a long\\u000a term population growth rate, asymptotic log-normality of total population size, and weak ergodicity of population structure.\\u000a We show here that these properties are

Stephen P. Ellner; Mark Rees

2007-01-01

267

Modelling ammonium-oxidizing population shifts in a biofilm reactor.  

PubMed

The dynamic reactor behaviour of a nitrifying inverse turbulent bed reactor, operated at varying loading rate, was described with a one-dimensional two-step nitrification biofilm model. In contrast with conventional biofilm models, this model includes the competition between two genetically different populations of ammonia-oxidizing bacteria (AOB), besides nitrite-oxidizing bacteria (NOB). Previously gathered experimental evidence showed that different loading rates in the reactor resulted in a change in the composition of the AOB community, besides a different nitrifying performance. The dissolved oxygen concentration in the bulk liquid was put forward as the key variable governing the experimentally observed shift from Nitrosomonas europaea (AOB1) to Nitrosomonas sp. (AOB2), which was confirmed by the developed one-dimensional biofilm model. Both steady state and dynamic analysis showed that the influence of microbial growth and endogenous respiration parameters as well as external mass transfer limitation have a clear effect on the competition dynamics. Overall, it was shown that the biomass distribution profiles of the coexisting AOB reflected the ecological niches created by substrate gradients. PMID:24434989

Vannecke, T P W; Bernet, N; Steyer, J-P; Volcke, E I P

2014-01-01

268

Determining parameters for populations by using structural models  

USGS Publications Warehouse

A method for calculating parameters necessary to maintain stable populations is described and the management implications of the method are discussed. This method depends upon knowledge of the population mortality rate schedule, the age at which the species reaches maturity, and recruitment rates or age ratios in the population. Four approaches are presented which yield information about the status of the population: (1) necessary production for a stable population, (2) allowable mortality for a stable population, (3) annual rate of change in population size, and (4) age ratios in the population which yield a stable condition. General formulas for these relationships, and formulas for several special cases, are presented. Tables are also presented showing production required to maintain a stable population with the simpler (more common) mortality and fecundity schedules.

Henny, C.J.; Overton, W.S.; Wight, H.M.

1970-01-01

269

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

270

Relationships of Lake Herring (Coregonus artedi) Gill Raker Characteristics to Retention Probabilities of Zooplankton Prey  

Microsoft Academic Search

We measured morphometric and meristic parameters of gill rakers from the first gill arch of 36 adult lake herring (Coregonus artedi) from Lake Superior that ranged in length from 283–504 mm. These data, coupled with the mean of the smallest two body dimensions (length, width, or breadth) of various zooplankton prey, allowed us to calculate retention probabilities for zooplankton taxa

Jason Link; Michael H. Hoff

1998-01-01

271

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

Microsoft Academic Search

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

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

2004-01-01

272

Interactions between piscivores, zooplanktivores and zooplankton in submerged macrophytes: preliminary observations from enclosure and pond experiments  

Microsoft Academic Search

The effects of piscivores upon zooplanktivore behaviour anddistribution and the impact of zooplanktivores on the abundance anddistribution of zooplankton are well documented. However, thepotential indirect effect of piscivores reducing the predationpressure upon grazing zooplankton through behavioural changes ofzooplanktivores has received little attention, even though this maybe an important mechanism in enhancing the stability of submergedmacrophytes in shallow lakes. Preliminary observations

Lene Jacobsen; Martin R. Perrow; Frank Landkildehus; Morten Hjørne; Torben L. Lauridsen; Søren Berg

1997-01-01

273

Zooplankton Grazing and Phytoplankton Abundance: an Assessment Before and After Invasion of Dreissena Polymorpha  

Microsoft Academic Search

The introduction of the zebra mussel Dreissena polymorpha into Lake Erie raises the question of whether it competes with the existing zooplankton community for phytoplankton. In this study, we approached this question by examining the role of zooplankton grazing in influencing Lake Erie abiotic conditions and biotic interactions during 2 years of varying zebra mussel abundances. In situ grazing experiments

Lin Wu; David A. Culver

1991-01-01

274

Quantifying marine snow as a food choice for zooplankton using stable silicon isotope tracers  

Microsoft Academic Search

Aggregates of biogenic origin >0.5 mm, known as marine snow, represent a concentrated potential source of food for zooplankton. Little is known, however, about whether aggregates are commonly grazed by zooplankton in the field. While previous laboratory studies have shown that the euphausiid Euphausia pacifica, and the copepod, Calanus pacificus, common crustacean zooplank- ters, consume marine snow if it is

LISA DILLING; MARK A. BRZEZINSKI

2004-01-01

275

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...

276

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

277

Spatial and temporal variation in mercury bioaccumulation by zooplankton in Lake Champlain (North America)  

Microsoft Academic Search

Trophic transfer of Hg across lakes within a region has been related to multiple environmental factors, but the nature of these relationships across distinct basins within individual large lakes is unknown. We investigated Hg bioaccumulation in zooplankton in basins of differing trophic status in Lake Champlain (Vermont, USA) to determine the strongest predictors of Hg bioaccumulation. Zooplankton were sampled in

Celia Chen; Neil Kamman; Jason Williams; Deenie Bugge; Vivien Taylor; Brian Jackson; Eric Miller

278

Competition in zooplankton communities: Suppression of small species by Daphnia pulex  

Microsoft Academic Search

The hypothesis that a large zooplankton herbivore, Daphnia pulex, can competitively reduce the abundance of resident zooplankton when colonizing a community of small species was tested in two lakes. When introduced to enclosures in eutrophic Larimore Pond, D. pulex decreased phytoplankton abundance by an order of magnitude, resulting in drastically reduced densities of Tropocyclops prasinus and Mesocyclops edax, the two

MICHAEL J. VANNI

1986-01-01

279

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.

280

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...

281

The summer zooplankton community at South Georgia: biomass, vertical migration and grazing  

Microsoft Academic Search

Zooplankton abundance and biomass were determined during January 1990 at two stations to the north-west of South Georgia using a Longhurst Hardy Plankton Recorder (LHPR). At both shelf and oceanic station sites, zooplankton biomass, (excluding Euphausia superba), was found to be ca. 13 g dry mass m-2. Copepods and small euphausiids dominated the catches. These estimates are over 4 times

P. Ward; A. Atkinson; A. W. A. Murray; A. G. Wood; R. Williams; S. A. Poulet

1995-01-01

282

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

Microsoft Academic Search

Zooplankton grazing was investigated by shipboard experiments during natural blooms of Alexandrium spp. in the offshore Gulf of Maine in spring and\\/or summer of 1998, 2000, and 2001. Grazing studies were done in conjunction with studies of accumulation of Alexandrium toxins in the zooplankton, as part of the ECOHAB-Gulf of Maine regional program. Several species of copepods, marine cladocerans, and

Jefferson T. Turner; David G. Borkman

2005-01-01

283

Zooplankton distributions at the Georges Bank frontal system: retention or dispersion?  

Microsoft Academic Search

The relation of zooplankton distributions to the physical environment across the frontal system on the northern flank of Georges Bank is described for early summer. The goal of this study was to determine if the frontal system is transparent or a barrier to the transport of zooplankton on and off the Bank. Physical characteristics of the frontal system included a

R. Ian Perry; Gareth C. Harding; John W. Loder; M. John Tremblay; Michael M. Sinclair; Kenneth F. Drinkwater

1993-01-01

284

Population Bottlenecks and Nonequilibrium Models in Population Genetics. I. Allele Numbers When Populations Evolve from Zero Variability  

PubMed Central

A simple numerical method was developed for the mean number and average age of alleles in a population that was initiated with no genetic variation following a sudden population expansion. The methods are used to examine the question of whether allele numbers are elevated compared with values seen in equilibrium populations having equivalent gene diversity. Excess allele numbers in expanding populations were found to be the rule. This was true whether the population began with zero variation or with low levels of variation in either of two initial distributions (initially an equilibrium allele frequency distribution or initially with loci occurring in only two classes of variation). Although the increase of alleles may persist for only a short time, when compared with the time which is required for approach to final equilibrium, the increase may be long when measured in absolute generation numbers. The pattern of increase in very rare alleles (those present only once in a sample) and the persistence of the original allele were also investigated. PMID:6500263

Maruyama, Takeo; Fuerst, Paul A.

1984-01-01

285

A MULTI-PATCH MALARIA MODEL WITH LOGISTIC GROWTH POPULATIONS*  

PubMed Central

In this paper, we propose a multi-patch model to study the effects of population dispersal on the spatial spread of malaria between patches. The basic reproduction number R0 is derived and it is shown that the disease-free equilibrium is locally asymptotically stable if R0<1 and unstable if R0>1. Bounds on the disease-free equilibrium and R0 are given. A sufficient condition for the existence of an endemic equilibrium when R0>1 is obtained. For the two-patch submodel, the dependence of R0 on the movement of exposed, infectious, and recovered humans between the two patches is investigated. Numerical simulations indicate that travel can help the disease to become endemic in both patches, even though the disease dies out in each isolated patch. However, if travel rates are continuously increased, the disease may die out again in both patches. PMID:23723531

GAO, DAOZHOU; RUAN, SHIGUI

2013-01-01

286

A MULTI-PATCH MALARIA MODEL WITH LOGISTIC GROWTH POPULATIONS.  

PubMed

In this paper, we propose a multi-patch model to study the effects of population dispersal on the spatial spread of malaria between patches. The basic reproduction number [Formula: see text] is derived and it is shown that the disease-free equilibrium is locally asymptotically stable if [Formula: see text] and unstable if [Formula: see text]. Bounds on the disease-free equilibrium and [Formula: see text] are given. A sufficient condition for the existence of an endemic equilibrium when [Formula: see text] is obtained. For the two-patch submodel, the dependence of [Formula: see text] on the movement of exposed, infectious, and recovered humans between the two patches is investigated. Numerical simulations indicate that travel can help the disease to become endemic in both patches, even though the disease dies out in each isolated patch. However, if travel rates are continuously increased, the disease may die out again in both patches. PMID:23723531

Gao, Daozhou; Ruan, Shigui

2012-01-01

287

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

288

Consistent two-population lattice Boltzmann model for thermal flows.  

PubMed

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. PMID:24483587

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

2013-12-01

289

Stability in Model Populations m onographs in p opulation b iology 3 1  

E-print Network

Stability in Model Populations m onographs in p opulation b iology · 3 1 laurence d. mueller amitabh joshi #12;Stability in Model Populations LAURENCE D. MUELLER AND AMITABH JOSHI PRINCETON--Introduction 000 Historical Development of the Concept of Population Stability 000 What Is Stability? 000

Rose, Michael R.

290

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

291

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

292

Theoretical Population Biology 71 (2007) 502523 The probability distribution under a population divergence model of the  

E-print Network

. All rights reserved. Keywords: Coalescence; Founding events; Lineage sorting; Ancestral population of Tristan de Cunha, which was settled by humans in the early 1800s. Genealogical records show that 15 settler women contributed to a population of $300 individuals at the time that the settlement

Jakobsson, Mattias

293

Seasonal changes in zooplankton abundance, biomass, size structure and dominant copepods in the Oyashio region analysed by an optical plankton counter  

NASA Astrophysics Data System (ADS)

To identify seasonal patterns of change in zooplankton communities, an optical plankton counter (OPC) and microscopic analysis were utilised to characterise zooplankton samples collected from 0 to 150 m and 0 to 500 m in the Oyashio region every one to three months from 2002 to 2007. Based on the OPC measurements, the abundance and biomass of zooplankton peaked in June (0-150 m) or August (150-500 m), depending on the depth stratum. The peak periods of the copepod species that were dominant in terms of abundance and biomass indicated species-specific patterns. Three Neocalanus species (Neocalanus cristatus, Neocalanus flemingeri and Neocalanus plumchrus) exhibited abundance peaks that occurred before their biomass peaks, whereas Eucalanus bungii and Metridia pacifica experienced biomass peaks before their abundance peaks. The abundance peaks corresponded to the recruitment periods of early copepodid stages, whereas the biomass peaks corresponded to the periods when the dominant populations reached the late copepodid stages (C5 or C6). Because the reproduction of Neocalanus spp. occurred in the deep layer (>500 m), their biomass peaks were observed when the major populations reached stage C5 after the abundance peaks of the early copepodid stages. The reproduction of E. bungii and M. pacifica occurred near the surface layer. These species first formed biomass peaks of C6 and later developed abundance peaks of newly recruited early copepodid stages. From the comparison between OPC measurements and microscopic analyses, seasonal changes in zooplankton biomass at depths of 0-150 m were governed primarily by E. bungii and M. pacifica, whereas those at depths of 150-500 m were primarily caused by the three Neocalanus species.

Yamaguchi, Atsushi; Matsuno, Kohei; Abe, Yoshiyuki; Arima, Daichi; Ohgi, Kohei

2014-09-01

294

EVALUATION OF THE EFFICACY OF EXTRAPOLATION POPULATION MODELING TO PREDICT THE DYNAMICS OF AMERICAMYSIS BAHIA POPULATIONS IN THE LABORATORY  

EPA Science Inventory

An age-classified projection matrix model has been developed to extrapolate the chronic (28-35d) demographic responses of Americamysis bahia (formerly Mysidopsis bahia) to population-level response. This study was conducted to evaluate the efficacy of this model for predicting t...

295

A Simple Model of Optimal Population Coding for Sensory Systems  

PubMed Central

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.

2014-01-01

296

Modelling targets for anticancer drug control optimization in physiologically structured cell population models  

NASA Astrophysics Data System (ADS)

The main two pitfalls of therapeutics in clinical oncology, that limit increasing drug doses, are unwanted toxic side effects on healthy cell populations and occurrence of resistance to drugs in cancer cell populations. Depending on the constraint considered in the control problem at stake, toxicity or drug resistance, we present two different ways to model the evolution of proliferating cell populations, healthy and cancer, under the control of anti-cancer drugs. In the first case, we use a McKendrick age-structured model of the cell cycle, whereas in the second case, we use a model of evolutionary dynamics, physiologically structured according to a continuous phenotype standing for drug resistance. In both cases, we mention how drug targets may be chosen so as to accurately represent the effects of cytotoxic and of cytostatic drugs, separately, and how one may consider the problem of optimisation of combined therapies.

Billy, Frédérique; Clairambault, Jean; Fercoq, Olivier; Lorenzi, Tommaso; Lorz, Alexander; Perthame, Benoît

2012-09-01

297

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...

298

Basic Concepts in Population Modeling, Simulation, and Model-Based Drug Development  

PubMed Central

Modeling is an important tool in drug development; population modeling is a complex process requiring robust underlying procedures for ensuring clean data, appropriate computing platforms, adequate resources, and effective communication. Although requiring an investment in resources, it can save time and money by providing a platform for integrating all information gathered on new therapeutic agents. This article provides a brief overview of aspects of modeling and simulation as applied to many areas in drug development. PMID:23835886

Mould, D R; Upton, R N

2012-01-01

299

An Emergency Evacuation Planning Model for Special Needs Populations  

Microsoft Academic Search

The need to have evacuation plans in place for ready implementation for special needs populations became evident after catastrophic events such as Hurricane Katrina. For the purpose of this study, special needs populations will include, but are not limited to, people with physical disabilities, older adults, non-English-speaking populations, residents and employees without vehicles, and tourists. The main objective of this

Evangelos I. Kaisar; Linda Hess; Alicia Benazir Portal Palomo

2012-01-01

300

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

301

Bayesian model comparison in cosmology with Population Monte Carlo  

NASA Astrophysics Data System (ADS)

We use Bayesian model selection techniques to test extensions of the standard flat ? cold dark matter (?CDM) paradigm. Dark-energy and curvature scenarios, and primordial perturbation models are considered. To that end, we calculate the Bayesian evidence in favour of each model using Population Monte Carlo (PMC), a new adaptive sampling technique which was recently applied in a cosmological context. In contrast to the case of other sampling-based inference techniques such as Markov chain Monte Carlo (MCMC), the Bayesian evidence is immediately available from the PMC sample used for parameter estimation without further computational effort, and it comes with an associated error evaluation. Also, it provides an unbiased estimator of the evidence after any fixed number of iterations and it is naturally parallelizable, in contrast with MCMC and nested sampling methods. By comparison with analytical predictions for simulated data, we show that our results obtained with PMC are reliable and robust. The variability in the evidence evaluation and the stability for various cases are estimated both from simulations and from data. For the cases we consider, the log-evidence is calculated with a precision of better than 0.08. Using a combined set of recent cosmic microwave background, type Ia supernovae and baryonic acoustic oscillation data, we find inconclusive evidence between flat ?CDM and simple dark-energy models. A curved universe is moderately to strongly disfavoured with respect to a flat cosmology. Using physically well-motivated priors within the slow-roll approximation of inflation, we find a weak preference for a running spectral index. A Harrison-Zel'dovich spectrum is weakly disfavoured. With the current data, tensor modes are not detected; the large prior volume on the tensor-to-scalar ratio r results in moderate evidence in favour of r = 0.

Kilbinger, Martin; Wraith, Darren; Robert, Christian P.; Benabed, Karim; Cappé, Olivier; Cardoso, Jean-François; Fort, Gersende; Prunet, Simon; Bouchet, François R.

2010-07-01

302

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

303

Networks and Models with Heterogeneous Population Structure in Epidemiology  

NASA Astrophysics Data System (ADS)

Heterogeneous population structure can have a profound effect on infectious disease dynamics, and is particularly important when investigating “tactical” disease control questions. At times, the nature of the network involved in the transmission of the pathogen (bacteria, virus, macro-parasite, etc.) appears to be clear; however, the nature of the network involved is dependent on the scale (e.g. within-host, between-host, or between-population), the nature of the contact, which ranges from the highly specific (e.g. sexual acts or needle sharing at the person-to-person level) to almost completely non-specific (e.g. aerosol transmission, often over long distances as can occur with the highly infectious livestock pathogen foot-and-mouth disease virus—FMDv—at the farm-to-farm level, e.g. Schley et al. in J. R. Soc. Interface 6:455-462, 2008), and the timescale of interest (e.g. at the scale of the individual, the typical infectious period of the host). Theoretical approaches to examining the implications of particular network structures on disease transmission have provided critical insight; however, a greater challenge is the integration of network approaches with data on real population structures. In this chapter, some concepts in disease modelling will be introduced, the relevance of selected network phenomena discussed, and then results from real data and their relationship to network analyses summarised. These include examinations of the patterns of air traffic and its relation to the spread of SARS in 2003 (Colizza et al. in BMC Med., 2007; Hufnagel et al. in Proc. Natl. Acad. Sci. USA 101:15124-15129, 2004), the use of the extensively documented Great Britain livestock movements network (Green et al. in J. Theor. Biol. 239:289-297, 2008; Robinson et al. in J. R. Soc. Interface 4:669-674, 2007; Vernon and Keeling in Proc. R. Soc. Lond. B, Biol. Sci. 276:469-476, 2009) and the growing interest in combining contact structure data with phylogenetics to identify real contact patterns as they directly relate to diseases of interest (Cottam et al. in PLoS Pathogens 4:1000050, 2007; Hughes et al. in PLoS Pathogens 5:1000590, 2009).

Kao, R. R.

304

The role of dust in models of population synthesis  

NASA Astrophysics Data System (ADS)

We have employed state-of-the-art evolutionary models of low- and intermediate-mass asymptotic giant branch (AGB) stars and included the effect of circumstellar dust shells on the spectral energy distribution (SED) of AGB stars in order to revise the Padua library of isochrones, which covers an extended range of ages and initial chemical compositions. The major revision involves the thermally pulsing AGB phase, which is now taken from fully evolutionary calculations by Weiss & Ferguson. Two libraries of about 600 AGB dust-enshrouded SEDs each have also been calculated, one for oxygen-rich M stars and one for carbon-rich C stars. Each library accounts for different values of input parameters like the optical depth ?, dust composition and temperature of the inner boundary of the dust shell. These libraries of dusty AGB spectra have been implemented into a large composite library of theoretical stellar spectra, to cover all regions of the Hertzsprung-Russell diagram (HRD) crossed by the isochrones. With the aid of the above isochrones and libraries of stellar SEDs, we have calculated the spectrophotometric properties (SEDs, magnitudes and colours) of single-generation stellar populations (SSPs) for six metallicities, more than 50 ages (from ˜3 Myr to 15 Gyr) and nine choices of the initial mass function. The new isochrones and SSPs have been compared with the colour-magnitude diagrams (CMDs) of field populations in the Large and Small Magellanic Clouds, with particular emphasis on AGB stars, and the integrated colours of star clusters in the same galaxies, using data from the catalogue `Surveying the Agents of Galaxy Evolution' (SAGE). We have also examined the integrated colours of a small sample of star clusters located on the outskirts of M31. The agreement between theory and observations is generally good. In particular, the new SSPs reproduce the red tails of the AGB star distribution in the CMDs of field stars in the Magellanic Clouds. Some discrepancies still exist and need to be investigated further.

Cassarà, L. P.; Piovan, L.; Weiss, A.; Salaris, M.; Chiosi, C.

2013-12-01

305

Synchronous dynamics of zooplankton competitors prevail in temperate lake ecosystems.  

PubMed

Although competing species are expected to exhibit compensatory dynamics (negative temporal covariation), empirical work has demonstrated that competitive communities often exhibit synchronous dynamics (positive temporal covariation). This has led to the suggestion that environmental forcing dominates species dynamics; however, synchronous and compensatory dynamics may appear at different length scales and/or at different times, making it challenging to identify their relative importance. We compiled 58 long-term datasets of zooplankton abundance in north-temperate and sub-tropical lakes and used wavelet analysis to quantify general patterns in the times and scales at which synchronous/compensatory dynamics dominated zooplankton communities in different regions and across the entire dataset. Synchronous dynamics were far more prevalent at all scales and times and were ubiquitous at the annual scale. Although we found compensatory dynamics in approximately 14% of all combinations of time period/scale/lake, there were no consistent scales or time periods during which compensatory dynamics were apparent across different regions. Our results suggest that the processes driving compensatory dynamics may be local in their extent, while those generating synchronous dynamics operate at much larger scales. This highlights an important gap in our understanding of the interaction between environmental and biotic forces that structure communities. PMID:24966312

Vasseur, David A; Fox, Jeremy W; Gonzalez, Andrew; Adrian, Rita; Beisner, Beatrix E; Helmus, Matthew R; Johnson, Catherine; Kratina, Pavel; Kremer, Colin; de Mazancourt, Claire; Miller, Elizabeth; Nelson, William A; Paterson, Michael; Rusak, James A; Shurin, Jonathan B; Steiner, Christopher F

2014-08-01

306

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

307

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

308

Population viability analysis: using a modeling tool to assess the viability of tapir populations in fragmented landscapes.  

PubMed

A population viability analysis (PVA) was conducted of the lowland tapir populations in the Atlantic Forest of the Pontal do Paranapanema region, Brazil, including Morro do Diabo State Park (MDSP) and surrounding forest fragments. Results from the model projected that the population of 126 tapirs in MDSP is likely to persist over the next 100 years; however, 200 tapirs would be required to maintain a viable population. Sensitivity analysis showed that sub-adult mortality and adult mortality have the strongest influence on the dynamics of lowland tapir populations. High road-kill has a major impact on the MDSP tapir population and can lead to population extinction. Metapopulation modeling showed that dispersal of tapirs from MDSP to the surrounding fragments can be detrimental to the overall metapopulation, as fragments act as sinks. Nevertheless, the model showed that under certain conditions the maintenance of the metapopulation dynamics might be determinant for the persistence of tapirs in the region, particularly in the smaller fragments. The establishment of corridors connecting MDSP to the forest fragments models resulted in an increase in the stochastic growth rate, making tapirs more resilient to threats and catastrophes, but only if rates of mortality were not increased when using corridors. The PVA showed that the conservation of tapirs in the Pontal region depends on: the effective protection of MDSP; maintenance and, whenever possible, enhancement of the functional connectivity of the landscape, reducing mortality during dispersal and threats in the unprotected forest fragments; and neutralization of all threats affecting tapirs in the smaller forest fragments. PMID:23253367

Medici, Emília Patrícia; Desbiez, Arnaud Leonard Jean

2012-12-01

309

Strong Spatial Influence on Colonization Rates in a Pioneer Zooplankton Metacommunity  

PubMed Central

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

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

2012-01-01

310

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

311

(137)Cs concentration in zooplankton and its relation to taxonomic composition in the western North Pacific Ocean.  

PubMed

To study the role of zooplankton in the transport of (137)Cs in the ocean, zooplankton samples were collected in October 2005 and June 2006 in the western North Pacific Ocean. The peak zooplankton biomass was observed in the surface layer, and gelatinous plankton was more abundant in October 2005 than in June 2006 reflecting exchange of water masses. The concentrations of (137)Cs in zooplankton varied from 11 to 24 mBq kg wet(-1) and were higher in October 2005 than in June 2006. The elevated abundance of gelatinous zooplankton probably led to higher concentration of (137)Cs in zooplankton in October 2005. Annual export fluxes of (137)Cs by ontogenetic vertical migrant copepods were estimated to be 0.8 and 0.6 mBq m(-2) year(-1) at 200 and 1000 m depths, respectively; this suggested that transport of (137)Cs by zooplankton may be no trivial pathway. PMID:18929436

Kaeriyama, Hideki; Watabe, Teruhisa; Kusakabe, Masashi

2008-12-01

312

Rational Chebyshev tau method for solving Volterra’s population model  

Microsoft Academic Search

An approximate method for solving Volterra’s population model for population growth of a species in a closed system is proposed. Volterra’s model is a nonlinear integro-differential equation where the integral term represents the effect of toxin. The approach is based on a rational Chebyshev tau method. The Volterra’s population model is first converted to a nonlinear ordinary differential equation. The

K. Parand; M. Razzaghi

2004-01-01

313

Chain pooling to minimize prediction error in subset regression. [Monte Carlo studies using population models  

NASA Technical Reports Server (NTRS)

Monte Carlo studies using population models intended to represent response surface applications are reported. Simulated experiments were generated by adding pseudo random normally distributed errors to population values to generate observations. Model equations were fitted to the observations and the decision procedure was used to delete terms. Comparison of values predicted by the reduced models with the true population values enabled the identification of deletion strategies that are approximately optimal for minimizing prediction errors.

Holms, A. G.

1974-01-01

314

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

PubMed

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

315

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

316

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

317

Guava ( Psidium guajava L.) trees in a pasture: population model, sensitivity analyses, and applications  

Microsoft Academic Search

A preliminary demographic model is presented for a population of guava (Psidium guajava L.) trees in a pasture. In this paper special attention is devoted to describing both the calculation and testing of the parameters of the model. Some applications of the model are described. It is predicted that the guava population will gradually decline; low seedling survival (due to

Eduardo Somarriba

1988-01-01

318

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

319

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

320

Population-based threshold models describe weed germination and emergence patterns across varying  

E-print Network

Population-based threshold models describe weed germination and emergence patterns across varying them to predict emergence from field soil. 2. We combined hydrothermal time for germination, accounting population. In all populations, germination rates increased between 9Á5 and 31 °C, b was

Bradford, Kent

321

Stable isotope and signature fatty acid analyses suggest reef manta rays feed on demersal zooplankton.  

PubMed

Assessing the trophic role and interaction of an animal is key to understanding its general ecology and dynamics. Conventional techniques used to elucidate diet, such as stomach content analysis, are not suitable for large threatened marine species. Non-lethal sampling combined with biochemical methods provides a practical alternative for investigating the feeding ecology of these species. Stable isotope and signature fatty acid analyses of muscle tissue were used for the first time to examine assimilated diet of the reef manta ray Manta alfredi, and were compared with different zooplankton functional groups (i.e. near-surface zooplankton collected during manta ray feeding events and non-feeding periods, epipelagic zooplankton, demersal zooplankton and several different zooplankton taxa). Stable isotope ?(15)N values confirmed that the reef manta ray is a secondary consumer. This species had relatively high levels of docosahexaenoic acid (DHA) indicating a flagellate-based food source in the diet, which likely reflects feeding on DHA-rich near-surface and epipelagic zooplankton. However, high levels of ?6 polyunsaturated fatty acids and slightly enriched ?(13)C values in reef manta ray tissue suggest that they do not feed solely on pelagic zooplankton, but rather obtain part of their diet from another origin. The closest match was with demersal zooplankton, suggesting it is an important component of the reef manta ray diet. The ability to feed on demersal zooplankton is likely linked to the horizontal and vertical movement patterns of this giant planktivore. These new insights into the habitat use and feeding ecology of the reef manta ray will assist in the effective evaluation of its conservation needs. PMID:24167562

Couturier, Lydie I E; Rohner, Christoph A; Richardson, Anthony J; Marshall, Andrea D; Jaine, Fabrice R A; Bennett, Michael B; Townsend, Kathy A; Weeks, Scarla J; Nichols, Peter D

2013-01-01

322

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-lives, 134Cs detected in our samples could only be derived from the FNPP1 accident. The highest 137Cs activity in zooplankton was same order of magnitude as that 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 occurrence of many diel vertical migratory zooplanktons. 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 follow the higher radiocesium activity in zooplankton. Biological characteristics of zooplankton community possibly influenced how large was contamination of radiocesium in the community but it is still unknown what kind of biological factors were important.

Kitamura, M.; Kumamoto, Y.; Kawakami, H.; Cruz, E. C.; Fujikura, K.

2013-04-01

323

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

324

Ecological implications of parasites in natural Daphnia populations.  

PubMed

In natural host populations, parasitism is considered to be omnipresent and to play an important role in shaping host life history and population dynamics. Here, we study parasitism in natural populations of the zooplankton host Daphnia magna investigating their individual and population level effects during a 2-year field study. Our results revealed a rich and highly prevalent community of parasites, with eight endoparasite species (four microsporidia, one amoeba, two bacteria and one nematode) and six epibionts (belonging to five different taxa: Chlorophyta, Bacillariophyceae, Ciliata, Fungi and Rotifera). Several of the endoparasites were associated with a severe overall fecundity reduction of the hosts, while such effects were not seen for epibionts. In particular, infections by Pasteuria ramosa, White Fat Cell Disease and Flabelliforma magnivora were strongly associated with a reduction in overall D. magna fecundity. Across the sampling period, average population fecundity of D. magna was negatively associated with overall infection intensity and total endoparasite richness. Population density of D. magna was negatively correlated to overall endoparasite prevalence and positively correlated with epibiont richness. Finally, the reduction in host fecundity caused by different parasite species was negatively correlated to both parasite prevalence and the length of the time period during which the parasite persisted in the host population. Consistent with epidemiological models, these results indicate that parasite mediated host damages influence the population dynamics of both hosts and parasites. PMID:15891825

Decaestecker, Ellen; Declerck, Steven; De Meester, Luc; Ebert, Dieter

2005-07-01

325

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

326

Modeling Grade IV Gas Emboli using a Limited Failure Population Model with Random Effects  

NASA Astrophysics Data System (ADS)

Venous gas emboli (VGE) (gas bubbles in venous blood) are associated with an increased risk of decompression sickness (DCS) in hypobaric environments. A high grade of VGE can be a precursor to serious DCS. In this paper, we model time to Grade IV VGE considering a subset of individuals assumed to be immune from experiencing VGE. Our data contain monitoring test results from subjects undergoing up to 13 denitrogenation test procedures prior to exposure to a hypobaric environment. The onset time of Grade IV VGE is recorded as contained within certain time intervals. We fit a parametric (lognormal) mixture survival model to the interval-and right-censored data to account for the possibility of a subset of "cured" individuals who are immune to the event. Our model contains random subject effects to account for correlations between repeated measurements on a single individual. Model assessments and cross-validation indicate that this limited failure population mixture model is an improvement over a model that does not account for the potential of a fraction of cured individuals. We also evaluated some alternative mixture models. Predictions from the best fitted mixture model indicate that the actual process is reasonably approximated by a limited failure population model.

Thompson, Laura A.; Conkin, Johnny; Chhikara, Raj S.; Powell, Michael R.

2002-05-01

327

Modeling Grade IV Gas Emboli using a Limited Failure Population Model with Random Effects  

NASA Technical Reports Server (NTRS)

Venous gas emboli (VGE) (gas bubbles in venous blood) are associated with an increased risk of decompression sickness (DCS) in hypobaric environments. A high grade of VGE can be a precursor to serious DCS. In this paper, we model time to Grade IV VGE considering a subset of individuals assumed to be immune from experiencing VGE. Our data contain monitoring test results from subjects undergoing up to 13 denitrogenation test procedures prior to exposure to a hypobaric environment. The onset time of Grade IV VGE is recorded as contained within certain time intervals. We fit a parametric (lognormal) mixture survival model to the interval-and right-censored data to account for the possibility of a subset of "cured" individuals who are immune to the event. Our model contains random subject effects to account for correlations between repeated measurements on a single individual. Model assessments and cross-validation indicate that this limited failure population mixture model is an improvement over a model that does not account for the potential of a fraction of cured individuals. We also evaluated some alternative mixture models. Predictions from the best fitted mixture model indicate that the actual process is reasonably approximated by a limited failure population model.

Thompson, Laura A.; Conkin, Johnny; Chhikara, Raj S.; Powell, Michael R.

2002-01-01

328

Population dynamics of species-rich ecosystems: the mixture of matrix population models approach  

E-print Network

-rich ecosystems, population dynamics Introduction The conservation of animal and plant species and their biologi popula- tion demography in the context of species invasion (Hooten et al. 2007; Sebert-Cuvillier et al, tropical marine fish or coral reefs, high diversity implies that the sample size for most species

Rossi, Vivien

329

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

330

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

331

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

332

Zooplankton size and distribution within mesoscale structures in the Mozambique Channel: A comparative approach using the TAPS acoustic profiler, a multiple net sampler and ZooScan image analysis  

NASA Astrophysics Data System (ADS)

Two surveys were conducted in the Mozambique Channel in November 2009 and April/May 2010 to study the influence of mesoscale eddies on the zooplanktonic component of the ecosystem. Three complementary methods were used to sample zooplankton: (1) hydro-acoustics with a TAPS™ multi-frequency zooplankton profiler; (2) in situ biological sampling using a Multinet with samples processed via the classical settled biovolume technique; (3) ZooScan image analysis which determines biovolume, size and taxonomic composition. This approach presented an ideal opportunity to compare the results of these different methods which highlighted a large overlap in their detectable size range. Each method favoured a particular size fraction of the population, i.e. TAPS for the microzooplankton (<0.1 mm ESR) and the Multinet and ZooScan for larger sizes (>3 mm ESR). In the case of the 2009 cruise, a well-established cyclone-anticyclone dipole was sampled, with results clearly indicating a higher concentration of zooplankton in the cyclonic eddy compared to the anticyclonic counterpart. The TAPS also detected high surface (0-22 m) concentrations of what appeared to be microzooplankton or marine snow in the cyclone. In 2010, the eddy field was less defined and more spatially variable compared to that in 2009. Two cyclonic and anticyclonic features were sampled during the cruise, each with different life histories and levels of stability. Results were inconsistent compared to those of 2009 and dependent on the size component of the population, with both cyclonic and anticyclonic features capable of having higher planktonic biomass. Differences in species composition between these mesoscale features were not too different and mainly a matter of relative biovolume. Less well formed eddy fields, particularly in the mid-Mozambique Channel, therefore appear to result in indistinct vertical and horizontal zooplankton distribution patterns.

Lebourges-Dhaussy, A.; Huggett, J.; Ockhuis, S.; Roudaut, G.; Josse, E.; Verheye, H.

2014-02-01

333

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

334

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

335

Biotic relations affecting species structure in zooplankton communities  

Microsoft Academic Search

Mathematical modelling and laboratory experiments were used to study how exploitative competition and predation influence\\u000a the species structure in cladoceran community. For five species of Cladocera (Sida crystallina, Daphnia magna, Simocephalus vetulus, Daphnia longispina, and Diaphanosoma brachyurum), representing a gradient of body size, population characteristics were described as functions of food concentration. Abundance\\u000a dynamics were simulated in mixed species cultures

Vitaliy P. Semenchenko; Vladimir I. Razlutskij; Irina Yu. Feniova; Denis N. Aibulatov

2007-01-01

336

ANALOG COMPUTER MODELS OF FISH POPULATIONS By RALPH P. SILLIMAN, Fishery Biologist (Research)  

E-print Network

ANALOG COMPUTER MODELS OF FISH POPULATIONS By RALPH P. SILLIMAN, Fishery Biologist (Research exploited fish populations. The model combined conventional exponential fishin~and natural mortality rates equation. survival curves for suc- cessive year classes of fish were ~enerated by the com- puter

337

Daphnias: from the individual based model to the large population equation  

E-print Network

Daphnias: from the individual based model to the large population equation J.A.J.(Hans) Metz The class of deterministic 'Daphnia' models treated by Diekmann et al. (J Math Biol 61: 277­318, 2010) has a general size-structured consumer population ('Daphnia') and an unstruc- tured resource ('algae

Paris-Sud XI, Université de

338

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...

339

Super-individuals a simple solution for modelling large populations on an individual basis  

Microsoft Academic Search

Modelling populations on an individual-by-individual basis has proven to be a fruitful approach. Many complex patterns that are observed on the population level have been shown to arise from simple interactions between individuals. However, a major problem with these models is that the typically large number of individuals needed requires impractically large computation times. The common solution, reduction of the

M. Scheffer; J. M. Baveco; D. L. DeAngelis; K. A. Rose; E. H. van Nes

1995-01-01

340

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) ...

341

A Nonlinear Model of Age and Size-Structured Populations with Applications to Cell Cycles  

E-print Network

A Nonlinear Model of Age and Size-Structured Populations with Applications to Cell Cycles S. J at a given size. Keywords: age-structure; size-structure; populations; cell cycle; mathematical model. 1 #12 cells the most applicable measure of size is DNA content. We initially derive a general age-structured

James, Alex

342

CONSTRUCTING, PERTURBATION ANALYSIIS AND TESTING OF A MULTI-HABITAT PERIODIC MATRIX POPULATION MODEL  

EPA Science Inventory

We present a matrix model that explicitly incorporates spatial habitat structure and seasonality and discuss preliminary results from a landscape level experimental test. Ecological risk to populations is often modeled without explicit treatment of spatially or temporally distri...

343

Leslie/Lefkovitch Matrix Models for Age or Stage-structured Populations  

NSDL National Science Digital Library

This excel workbook uses the Leslie matrix model for population projection of age-class structured populations, and also allows Lefkovitch matrix models for stage-class structured populations. The user enters age or stage specific fecundity and survival rates as well as the populationâÂÂs initial proportions. The workbook calculates the matrix with corresponding eigenvalues for finite growth rate and eigenvectors for stable age/stage distribution and reproductive value. The graphical output included illustrates the stabilization of population structure, reproductive values and the finite rate of increase. It also includes exponential growth curves and semi-log plots of the population growth. The user can view population projections for four actual datasets.

John Jungck (Beloit College;Biology); Jennifer Spangenberg (Beloit College;)

2005-05-21

344

Histology of Herniations through the Body Wall and Cuticle of Zooplankton from the Laurentian Great Lakes  

E-print Network

Histology of Herniations through the Body Wall and Cuticle of Zooplankton from the Laurentian Great a histologic and cyto- logic analysis of the protrusions and found that they are composed of apparently

345

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

346

A comparison of neustonic plastic and zooplankton at different depths near the southern California shore.  

PubMed

Previous studies of neustonic debris have been limited to surface sampling. Here we conducted two trawl surveys, one before and one shortly after a rain event, in which debris and zooplankton density were measured at three depths in Santa Monica Bay, California. Surface samples were collected with a manta trawl, mid-depth samples with a bongo net and bottom samples with an epibenthic sled, all having 333 micron nets. Density of debris was greatest near the bottom, least in midwater. Debris density increased after the storm, particularly at the sampling site closest to shore, reflecting inputs from land-based runoff and resuspended matter. The mass of plastic collected exceeded that of zooplankton, though when the comparison was limited to plastic debris similar to the size of most zooplankton, zooplankton mass was three times that of debris. PMID:15341821

Lattin, G L; Moore, C J; Zellers, A F; Moore, S L; Weisberg, S B

2004-08-01

347

An individual-based model for population viability analysis of humpback chub in Grand Canyon  

USGS Publications Warehouse

We developed an individual-based population viability analysis model (females only) for evaluating risk to populations from catastrophic events or conservation and research actions. This model tracks attributes (size, weight, viability, etc.) for individual fish through time and then compiles this information to assess the extinction risk of the population across large numbers of simulation trials. Using a case history for the Little Colorado River population of Humpback Chub Gila cypha in Grand Canyon, Arizona, we assessed extinction risk and resiliency to a catastrophic event for this population and then assessed a series of conservation actions related to removing specific numbers of Humpback Chub at different sizes for conservation purposes, such as translocating individuals to establish other spawning populations or hatchery refuge development. Our results suggested that the Little Colorado River population is generally resilient to a single catastrophic event and also to removals of larvae and juveniles for conservation purposes, including translocations to establish new populations. Our results also suggested that translocation success is dependent on similar survival rates in receiving and donor streams and low emigration rates from recipient streams. In addition, translocating either large numbers of larvae or small numbers of large juveniles has generally an equal likelihood of successful population establishment at similar extinction risk levels to the Little Colorado River donor population. Our model created a transparent platform to consider extinction risk to populations from catastrophe or conservation actions and should prove useful to managers assessing these risks for endangered species such as Humpback Chub.

Pine, William Pine, III; Healy, Brian; Smith, Emily Omana; Trammell, Melissa; Speas, Dave; Valdez, Rich; Yard, Mike; Walters, Carl; Ahrens, Rob; Vanhaverbeke, Randy; Stone, Dennis; Wilson, Wade

2013-01-01

348

A toy model for hostility between two populations in dependency on their internal frustration  

NASA Astrophysics Data System (ADS)

Hostility between two populations n and m is described in terms of a first-order differential equation system for the population sizes n(t) and m(t) over time t. Each population is subdivided into two subpopulations 'Doves' and 'Hawks'. Hawks represent the strategy aggression against the other population. The number of hawks which actually exert aggression depends on the overall frustration within their population. Conversely, aggression causes the conversion from doves to hawks in the attacked population. Thus, a system of flows among the subpopulation is established. The actual behaviour of n(t) and m(t) over time t depends on the coefficients chosen for the differential system and in particular on the temporal development of the frustration parameters. No calculation or simulation of actual population sizes is intended. The only goal of the paper is to establish a model which describes an never ending conflict between both populations caused by internal frustrations.

Wieder, Thomas

2014-10-01

349

Extension of landscape-based population viability models to ecoregional scales for conservation planning  

Microsoft Academic Search

Landscape-based population models are potentially valuable tools in facilitating conservation planning and actions at large scales. However, such models have rarely been applied at ecoregional scales. We extended landscape-based population models to ecoregional scales for three species of concern in the Central Hardwoods Bird Conservation Region and compared model projections against long-term trend data from the North American Breeding Bird

Thomas W. Bonnot; Frank R. Thompson; Joshua J. Millspaugh

2011-01-01

350

Sources of zooplankton on the Nova Scotia shelf and their aggregations within deep-shelf basins  

Microsoft Academic Search

A large-scale survey\\/study of zooplankton on the Scotian Shelf south of Nova Scotia was performed during 1984 1985. Rapid sampling was accomplished using a Batfish vehicle mounted with an optical plankton counter, a multiple opening\\/closing net system (BIONESS), and multifrequency acoustics. From the Batfish survey reported here, we present evidence indicating that the dominant supply of zooplankton to the Scotian

A. W. Herman; D. D. Sameoto; Chen Shunnian; M. R. Mitchell; B. Petrie; N. Cochrane

1991-01-01

351

Grazing by 35 to 202 ?m micro-zooplankton in Long Island Sound  

Microsoft Academic Search

Micro-zooplankton abundance in Long Island Sound varied from 103 to 104 animals l-1 at the station studied and consisted almost entirely of tintinnids. The micro-zooplankton were found to sometimes remove a significant portion of the chlorophyll a standing stock, with an upper limit of 41% of the standing stock being ingested per day. Observed ingestion rates ranged from 0.001 to

G. M. Capriulo; E. J. Carpenter

1980-01-01

352

Effect of watershed land use and lake age on zooplankton species richness  

Microsoft Academic Search

Results of a field survey of southern Wisconsin shallow lakes suggested that watershed (catchment basin) land use has a significant\\u000a and adverse effect on zooplankton species richness. Zooplankton communities in lakes with no riparian buffer zone, in agriculture-dominated\\u000a watersheds, contained about half as many species as lakes in least-impact watersheds. In that study, the age of the lake was\\u000a not

Stanley I. Dodson; William R. Everhart; Andrew K. Jandl; Sara J. Krauskopf

2007-01-01

353

Improving Bayesian Population Dynamics Inference: A Coalescent-Based Model for Multiple Loci  

PubMed Central

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.

2013-01-01

354

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

355

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

356

Examining shifts in zooplankton community as a response of environmental change in Lakes  

NASA Astrophysics Data System (ADS)

We examined 20 years of zooplankton samples from Harp Lake for shifts in zooplankton variability following invasion by zooplankton predator Bythotrephes longimanus, using organism body size—as measured at high resolution by Laser Optical Plankton Counter (LOPC)—as the primary metric of investigation. A period of transitory high variability in the 2yr post-invasion was observed for both body size compositional variability and aggregate variability metrics, with both measures of variability shifting from low or intermediate to high variability immediately following invasion, before shifting again to intermediate variability, 2 yr post-invasion. Aggregate and compositional variability dynamics were also considered in combination over the study period, revealing that the period of transitory high variability coincided with a shift from a community-wide stasis variability pattern to one of asynchrony, before a shift back to stasis 2 yr post-invasion. These dynamics were related to changes in the significant zooplankton species within the Harp Lake community over the pre- and post- invasion periods, and are likely to be indicative of changes in the stability in the zooplankton community following invasion by Bythotrephes. The dual consideration of aggregate and compositional variability as measured by LOPC was found to provide a valuable means to assess the ecological effects of biological invasion on zooplankton communities as a whole, extending our knowledge of the effects of invasion beyond that already revealed through more traditional taxonomic investigation.

Ghadouani, Anas; Mines, Conor; Legendre, Pierre; Yan, Norman

2014-05-01

357

Abundance and diversity of zooplankton in semi intensive prawn (Macrobrachium rosenbergii) farm.  

PubMed

The present study was carried out on the seasonal abundance and diversity of zooplankton in a semi- intensive prawn farm of Bagerhat district from July to December, 2008. Plankton samples were collected by conical shaped monofilament nylon net (Plankton net) and Lugol's solution was used for preservation. The zooplankton abundance was influenced by physico-chemical factors. During the study period 11 genera of zooplankton under 5 orders were recorded from the study ponds namely Copepoda, Rotifera, Cladocera, Ostracoda and Crustacean Larvae. Among all groups copepod was the dominant order. The percentages of Copepoda, Rotifera, Cladocera, Ostracoda and Crustacean Larvae in semi-intensive culture system were 54%, 28%, 12%, 4% and 2% respectively. But the genera Brachionus under the order of Rotifer was dominant among all other genera. Cyclops and Helidiaptomus under the order of Copepod were the 2nd dominant genera. Numbers of zooplankton species were recorded to be the highest in summer season and minimum at early winter season. Highest number of zooplankton found at the month of October. Total zooplankton shows significant positive relationship with water temperature ((r?=?+0.384), Dissolve Oxygen(r?=?+0.113), pH(r?=?+0.320), Free CO2 (r?=?+0.319), Alkalinity(r?=?+0.269), Hardness (r?=?+0.402) and negative relationship with Salinity(r?=?-0.486), Transparency(r?=?-0.693). The findings of the present study will help to improve the management strategies of shrimp culture system. PMID:23667823

Shil, Jadobendro; Ghosh, Alokesh Kumar; Rahaman, S M Bazlur

2013-12-01

358

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...

359

Ecological implications of parasites in natural Daphnia populations  

Microsoft Academic Search

In natural host populations, parasitism is considered to be omnipresent and to play an important role in shaping host life\\u000a history and population dynamics. Here, we study parasitism in natural populations of the zooplankton host Daphnia magna investigating their individual and population level effects during a 2-year field study. Our results revealed a rich and\\u000a highly prevalent community of parasites,

Ellen Decaestecker; Steven Declerck; Luc De Meester; Dieter Ebert

2005-01-01

360

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

361

Density and sound speed of two gelatinous zooplankton: ctenophore (Mnemiopsis leidyi) and lion's mane jellyfish (Cyanea capillata).  

PubMed

The density and sound speed of two coastal, gelatinous zooplankton, Mnemiopsis leidyi (a ctenophore) and Cyanea capillata (lion's mane jellyfish), were measured. These parameters are important inputs to acoustic scattering models. Two different methods were used to measure the density of individual animals: one used a balance and graduated cylinder to determine the mass and displacement volume of the animal, the other varied the density of the solution the animal was immersed in. When the same animal was measured using both methods, density values were within 1% of each other. A travel-time difference method was used to measure the sound speed within the animals. The densities of both zooplankton slightly decreased as the animals increased in length, mass, and volume. The ratio of animal density and sound speed to the surrounding seawater (g and h, respectively) are reported for both animals. For Mnemiopsis leidyi ranging in length from 1 to 5 cm, the mean value (+/-standard deviation) of g and h were 1.009 (+/-0.004) and 1.007 (+/-0.001). For Cyanea capillata ranging in bell diameter from 2 to 11 cm, the mean value (+/-standard deviation) of g and single value of h were 1.009 (+/-0.004) and 1.0004. PMID:17614513

Warren, Joseph D; Smith, Joy N

2007-07-01

362

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

363

Are the numbers adding up? Exploiting discrepancies among complementary population models  

PubMed Central

Large carnivores are difficult to monitor because they tend to be sparsely distributed, sensitive to human activity, and associated with complex life histories. Consequently, understanding population trend and viability requires conservationists to cope with uncertainty and bias in population data. Joint analysis of combined data sets using multiple models (i.e., integrated population model) can improve inference about mechanisms (e.g., habitat heterogeneity and food distribution) affecting population dynamics. However, unobserved or unobservable processes can also introduce bias and can be difficult to quantify. We developed a Bayesian hierarchical modeling approach for inference on an integrated population model that reconciles annual population counts with recruitment and survival data (i.e., demographic processes). Our modeling framework is flexible and enables a realistic form of population dynamics by fitting separate density-dependent responses for each demographic process. Discrepancies estimated from shared parameters among different model components represent unobserved additions (i.e., recruitment or immigration) or removals (i.e., death or emigration) when annual population counts are reliable. In a case study of gray wolves in Wisconsin (1980–2011), concordant with policy changes, we estimated that a discrepancy of 0% (1980–1995), ?2% (1996–2002), and 4% (2003–2011) in the annual mortality rate was needed to explain annual growth rate. Additional mortality in 2003–2011 may reflect density-dependent mechanisms, changes in illegal killing with shifts in wolf management, and nonindependent censoring in survival data. Integrated population models provide insights into unobserved or unobservable processes by quantifying discrepancies among data sets. Our modeling approach is generalizable to many population analysis needs and allows for identifying dynamic differences due to external drivers, such as management or policy changes. PMID:25691964

Stenglein, Jennifer L; Zhu, Jun; Clayton, Murray K; Van Deelen, Timothy R

2015-01-01

364

Testing a Theoretical Model that Predicts Thresholds in Populations Forced by Imposing Random, Episodic Disturbances  

NASA Astrophysics Data System (ADS)

We do not fully understand reasons behind extinction of populations and species. Consequently, our ability to anticipate extinction (which can be considered a permanent type of an ecological threshold) has remained elusive. In particular, it is not clear how the attributes of episodic disturbance regimes can elicit extinction. Here, I test a stochastic model that predicts population extinction based on attributes of the disturbance regime and population growth rates using phytoplankton in a test tube. I examined the response of phytoplankton (Thalassiosira weissflogii) to stochastic disturbances implemented by having MATLAB control a hydraulic pump that episodically removed portions of the population through time in between episodes of population recovery. My experiment demonstrated evidence that a theoretical or mathematical threshold predicted to exist in theory may actually apply to a diatom population dynamics in a test tube; however, my results also open new questions about how the statistical attributes of the disturbance regimes under study may alter the predicted time to population extinction.

Olsen, C.; Lintz, H. E.; Peckham, S. D.

2013-12-01

365

The limnology of Canyon Ferry Reservoir. I. Thephytoplankton-zooplankton relationships in the euphotic zone during September and October, 1956  

Microsoft Academic Search

Phytoplankton and zooplankton standing crop, gross and net primary production were measured. From these data the daily rate of loss of phytoplankton from the euphotic zone was calculated. The phytoplankton loss correlated well with zooplankton during Scptem- ber and with vertical water movement during October. A grazing coefficient was calculated (G = 1.064 L water\\/mg dry wt. zooplankton\\/day). By use

JOHN C. WRIGHT

1958-01-01

366

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

367

A heterogeneous population model for the analysis of bacterial growth kinetics  

Microsoft Academic Search

A two-compartment, heterogeneous population model (HPM) was derived using the simulation software SB ModelMaker© to describe the growth of Listeria monocytogenes in bacteriological media at 5–35 °C. The model assumed that, at time t = 0, the inoculum was distributed between two distinct compartments, Non-Growing and Growing, and that growth could be described by four parameters: initial total cell population

R. C. McKellar

1997-01-01

368

How genes causing unfit hybrids evolve within populations: a review of models of postzygotic isolation  

Microsoft Academic Search

The main subject for models of postzygotic isolation has been how reproductive isolation genes (RI genes) which cause hybrid\\u000a inviability or sterility spread within populations despite their deleterious effects. The models are divided into three categories\\u000a according to the within-population effect of RI genes in their fixation process. (1) The beneficial effect model, where RI\\u000a genes are assumed to spread

Takehiko I. Hayashi; Masakado Kawata

2002-01-01

369

A Potts Model for Night Light and Human Population  

E-print Network

The Potts model was one of the most popular physics models of the twentieth century in an interdisciplinary context. It has been applied to a large variety of problems. Many generalizations exists and a whole range of models were inspired by this statistical physics tool. Here we present how a generic Potts model can be used to study complex data. As a demonstration, we engage our model in the analysis of night light patterns of human settlements observed on space photographs.

Máté, Gabriell

2015-01-01

370

The evolution of wealth transmission in human populations: a stochastic model  

NASA Astrophysics Data System (ADS)

Reproductive success and survival are influenced by wealth in human populations. Wealth is transmitted to offsprings and strategies of transmission vary over time and among populations, the main variation being how equally wealth is transmitted to children. Here we propose a model where we simulate both the dynamics of wealth in a population and the evolution of a trait that determines how wealth is transmitted from parents to offspring, in a darwinian context.

Augustins, G.; Etienne, L.; Ferdy, J.-B.; Ferrer, R.; Godelle, B.; Pitard, E.; Rousset, F.

2014-03-01

371

The evolution of wealth transmission in human populations: a stochastic model  

E-print Network

Reproductive success and survival are influenced by wealth in human populations. Wealth is transmitted to offsprings and strategies of transmission vary over time and among populations, the main variation being how equally wealth is transmitted to children. Here we propose a model where we simulate both the dynamics of wealth in a population and the evolution of a trait that determines how wealth is transmitted from parents to offspring, in a darwinian context.

Augustins, G; Ferdy, J-B; Ferrer, R; Godelle, B; Pitard, E; Rousset, F

2014-01-01

372

Modelling the effects of ionizing radiation on survival of animal population: acute versus chronic exposure.  

PubMed

The objective of the present paper was application of a model, which was originally developed to simulate chronic ionizing radiation effects in a generic isolated population, to the case of acute exposure, and comparison of the dynamic features of radiation effects on the population survival in cases of acute and chronic exposure. Two modes of exposure were considered: acute exposure (2-35 Gy) and chronic lifetime exposure with the same integrated dose. Calculations were made for a generic mice population; however, the model can be applied for other animals with proper selection of parameter values. In case of acute exposure, in the range 2-11 Gy, the population response was in two phases. During a first phase, there was a depletion in population survival; the second phase was a recovery period due to reparation of damage and biosynthesis of new biomass. Model predictions indicate that a generic mice population, living in ideal conditions, has the potential for recovery (within a mouse lifetime period) from acute exposure with dose up to 10-11 Gy, i.e., the population may recover from doses above an LD50 (6.2 Gy). Following acute doses above 14 Gy, however, the mice population went to extinction without recovery. In contrast, under chronic lifetime exposures (500 days), radiation had little effect on population survival up to integrated doses of 14-15 Gy, so the survival of a population subjected to chronic exposure was much better compared with that after an acute exposure with the same dose. Due to the effect of "wasted radiation", the integrated dose of chronic exposure could be about two times higher than acute dose, producing the same effect on survival. It is concluded that the developed generic population model including the repair of radiation damage can be applied both to acute and chronic modes of exposure; results of calculations for generic mice population are in qualitative agreement with published data on radiation effects in mice. PMID:25481246

Kryshev, A I; Sazykina, T G

2014-12-01

373

Refinement of a model for evaluating the population exposure in an urban area  

NASA Astrophysics Data System (ADS)

A mathematical model is presented for the determination of human exposure to ambient air pollution in an urban area; the model is a refined version of a previously developed mathematical model EXPAND (EXposure model for Particulate matter And Nitrogen oxiDes). The model combines predicted concentrations, information on people's activities and location of the population to evaluate the spatial and temporal variation of average exposure of the urban population to ambient air pollution in different microenvironments. The revisions of the modelling system containing the EXPAND model include improvements of the associated urban emission and dispersion modelling system, an improved treatment of the time-use of population, and better treatment for the infiltration coefficients from outdoor to indoor air. The revised model version can also be used for evaluating intake fractions for various pollutants, source categories and population subgroups. We present numerical results on annual spatial concentration, time activity and population exposures to PM2.5 in the Helsinki Metropolitan Area and Helsinki for 2008 and 2009, respectively. Approximately 60% of the total exposure occurred at home, 17% at work, 4% in traffic and 19% in other micro-environments. The population exposure originated from the long range transported background concentrations was responsible for a major fraction, 86%, of the total exposure. The largest local contributors were vehicular emissions (12%) and shipping (2%).

Soares, J.; Kousa, A.; Kukkonen, J.; Matilainen, L.; Kangas, L.; Kauhaniemi, M.; Riikonen, K.; Jalkanen, J.-P.; Rasila, T.; Hänninen, O.; Koskentalo, T.; Aarnio, M.; Hendriks, C.; Karppinen, A.

2014-04-01

374

Modeling of LEO Orbital Debris Populations in Centimeter and Millimeter Size Regimes  

NASA Technical Reports Server (NTRS)

The building of the NASA Orbital Debris Engineering Model, whether ORDEM2000 or its recently updated version ORDEM2010, uses as its foundation a number of model debris populations, each truncated at a minimum object-size ranging from 10 micron to 1 m. This paper discusses the development of the ORDEM2010 model debris populations in LEO (low Earth orbit), focusing on centimeter (smaller than 10 cm) and millimeter size regimes. Primary data sets used in the statistical derivation of the cm- and mm-size model populations are from the Haystack radar operated in a staring mode. Unlike cataloged objects of sizes greater than approximately 10 cm, ground-based radars monitor smaller-size debris only in a statistical manner instead of tracking every piece. The mono-static Haystack radar can detect debris as small as approximately 5 mm at moderate LEO altitudes. Estimation of millimeter debris populations (for objects smaller than approximately 6 mm) rests largely on Goldstone radar measurements. The bi-static Goldstone radar can detect 2- to 3-mm objects. The modeling of the cm- and mm-debris populations follows the general approach to developing other ORDEM2010-required model populations for various components and types of debris. It relies on appropriate reference populations to provide necessary prior information on the orbital structures and other important characteristics of the debris objects. NASA's LEO-to-GEO Environment Debris (LEGEND) model is capable of furnishing such reference populations in the desired size range. A Bayesian statistical inference process, commonly adopted in ORDEM2010 model-population derivations, changes a priori distribution into a posteriori distribution and thus refines the reference populations in terms of data. This paper describes key elements and major steps in the statistical derivations of the cm- and mm-size debris populations and presents results. Due to lack of data for near 1-mm sizes, the model populations of 1- to 3.16-mm objects are an empirical extension from larger debris. The extension takes into account the results of micro-debris (from 10 micron to 1 mm) population modeling that is based on shuttle impact data, in the hope of making a smooth transition between micron and millimeter size regimes. This paper also includes a brief discussion on issues and potential future work concerning the analysis and interpretation of Goldstone radar data.

Xu, Y.-L.; Hill, . M.; Horstman, M.; Krisko, P. H.; Liou, J.-C.; Matney, M.; Stansbery, E. G.

2010-01-01

375

Population density models of integrate-and-fire neurons with jumps: well-posedness.  

PubMed

In this paper we study the well-posedness of different models of population of leaky integrate-and-fire neurons with a population density approach. The synaptic interaction between neurons is modeled by a potential jump at the reception of a spike. We study populations that are self excitatory or self inhibitory. We distinguish the cases where this interaction is instantaneous from the one where there is a repartition of conduction delays. In the case of a bounded density of delays both excitatory and inhibitory population models are shown to be well-posed. But without conduction delay the solution of the model of self excitatory neurons may blow up. We analyze the different behaviours of the model with jumps compared to its diffusion approximation. PMID:22714650

Dumont, Grégory; Henry, Jacques

2013-09-01

376

Population growth in snow geese: a modeling approach integrating demographic and survey information.  

PubMed

There are few analytic tools available to formally integrate information coming from population surveys and demographic studies. The Kalman filter is a procedure that facilitates such integration. Based on a state-space model, we can obtain a likelihood function for the survey data using a Kalman filter, which we may then combine with a likelihood for the demographic data. In this paper, we used this combined approach to analyze the population dynamics of a hunted species, the Greater Snow Goose (Chen caerulescens atlantica), and to examine the extent to which it can improve previous demographic population models. The state equation of the state-space model was a matrix population model with fecundity and regression parameters relating adult survival and harvest rate estimated in a previous capture-recapture study. The observation equation combined the output from this model with estimates from an annual spring photographic survey of the population. The maximum likelihood estimates of the regression parameters from the combined analysis differed little from the values of the original capture-recapture analysis, though their precision improved. The model output was found to be insensitive to a wide range of coefficient of variation (CV) in fecundity parameters. We found a close match between the surveyed and smoothed population size estimates generated by the Kalman filter over an 18-year period, and the estimated CV of the survey (0.078-0.150) was quite compatible with its assumed value (approximately 0.10). When we used the updated parameter values to predict future population size, the model underestimated the surveyed population size by 18% over a three-year period. However, this could be explained by a concurrent change in the survey method. We conclude that the Kalman filter is a promising approach to forecast population change because it incorporates survey information in a formal way compared with ad hoc approaches that either neglect this information or require some parameter or model tuning. PMID:17601135

Gauthier, Gilles; Besbeas, Panagiotis; Lebreton, Jean-Dominique; Morgan, Byron J T

2007-06-01

377

Modeling the population dynamics of Culex quinquefasciatus (Diptera: Culcidae), along an elevational gradient in Hawaii  

USGS Publications Warehouse

We present a population model to understand the effects of temperature and rainfall on the population dynamics of the southern house mosquito, Culex quinquefasciatus Say, along an elevational gradient in Hawaii. We use a novel approach to model the effects of temperature on population growth by dynamically incorporating developmental rate into the transition matrix, by using physiological ages of immatures instead of chronological age or stages. We also model the effects of rainfall on survival of immatures as the cumulative number of days below a certain rain threshold. Finally, we incorporate density dependence into the model as competition between immatures within breeding sites. Our model predicts the upper altitudinal distributions of Cx. quinquefasciatus on the Big Island of Hawaii for self-sustaining mosquito and migrating summer sink populations at 1,475 and 1,715 m above sea level, respectively. Our model predicts that mosquitoes at lower elevations can grow under a broader range of rainfall parameters than middle and high elevation populations. Density dependence in conjunction with the seasonal forcing imposed by temperature and rain creates cycles in the dynamics of the population that peak in the summer and early fall. The model provides a reasonable fit to the available data on mosquito abundance for the east side of Mauna Loa, Hawaii. The predictions of our model indicate the importance of abiotic conditions on mosquito dynamics and have important implications for the management of diseases transmitted by Cx. quinquefasciatus in Hawaii and elsewhere.

Ahumada, Jorge A.; LaPointe, D.; Samuel, Michael D.

2004-01-01

378

Modelling the Effects of Dispersal and Landscape Configuration on Population Distribution and Viability in Fragmented Habitat  

Microsoft Academic Search

Landscape configuration and dispersal characteristics are major determinants of population distribution and persistence in fragmented habitat. An individual-based spatially explicit population model was developed to investigate these factors using the distribution of nuthatches in an area of eastern England as an example. The effects of immigration and increasing the area of breeding quality habitat were explored. Predictions were compared with

Jolyon Alderman; Duncan McCollin; Shelley A. Hinsley; Paul E. Bellamy; Phil Picton; Robin Crockett

2005-01-01

379

A stochastic model of evolutionary dynamics with deterministic large-population asymptotics  

E-print Network

A stochastic model of evolutionary dynamics with deterministic large-population asymptotics Burton-diffusion equation Reactive strategies Iterated prisoner's dilemma a b s t r a c t An evolutionary birth on their local population density. Agents' individual evolutionary trajectories in X and S are governed

Simon, Burt

380

Management and Conservation Article Sensitivity Analyses of a Population Projection Model of  

E-print Network

on population dynamics of ring-necked pheasant (Phasianus colchicus) in North America, but there has not been, elasticity, finite rate of increase, matrix population model, nest success, Phasianus colchicus, pheasant, sensitivity analysis, winter survival. Ring-necked pheasants (Phasianus colchicus) in North America have been

Clark, William R.

381

Agricultural expansion and deforestation: modelling the impact of population, market forces and property rights  

Microsoft Academic Search

This paper compares four different modelling approaches to agricultural expansion and deforestation, and explores the implications of assumptions about the household objectives, the labour market, and the property rights regime. A major distinction is made between population and market based explanations. Many of the popular policy prescriptions are based on the population approach, assuming subsistence behaviour and limited market integration.

Arild Angelsen

1999-01-01

382

A model of fish population distribution in the space of inhabitation  

Microsoft Academic Search

This article is dedicated to the question of modeling of fish population distribution. The article includes theoretical part and part devoted to numerical estimation by received theoretical expressions. Mechanism of the distribution as a result of response of organisms forming population on the affecting factors is described in the theoretical part of the article. Independent and interdependent influences of factors

V. V. Gertseva; V. I. Gertsev

2002-01-01

383

DEVELOPING A HABITAT-BASED POPULATION VIABILITY MODEL FOR SAGE GROUSE  

E-print Network

DEVELOPING A HABITAT-BASED POPULATION VIABILITY MODEL FOR SAGE GROUSE IN SOUTHEASTERN ALBERTA FINAL PROJECT REPORT FOR 2001 SAGE GROUSE FUNDING PARTNERS Cameron L. Aldridge Department of Biological Sciences@ualberta.ca December, 2001 #12;ii ABSTRACT The Alberta Sage Grouse population has declined by 66-92% over the last 30

Aldridge, Cameron

384

DEVELOPING A HABITAT-BASED POPULATION VIABILITY MODEL FOR SAGE-GROUSE  

E-print Network

DEVELOPING A HABITAT-BASED POPULATION VIABILITY MODEL FOR SAGE-GROUSE IN SOUTHEASTERN ALBERTA FINAL PROJECT REPORT FOR 2003 SAGE-GROUSE FUNDING PARTNERS Cameron L. Aldridge Department of Biological Sciences@ualberta.ca November 30, 2003 #12;ii ABSTRACT The endangered Alberta Sage-Grouse population has declined by 66-92% over

Aldridge, Cameron

385

DEVELOPING A HABITAT-BASED POPULATION VIABILITY MODEL FOR SAGE-GROUSE  

E-print Network

DEVELOPING A HABITAT-BASED POPULATION VIABILITY MODEL FOR SAGE-GROUSE IN SOUTHEASTERN ALBERTA FINAL PROJECT REPORT FOR 2002 SAGE-GROUSE FUNDING PARTNERS Cameron L. Aldridge Department of Biological Sciences@ualberta.ca November 30, 2002 #12;ii ABSTRACT The Alberta Sage-Grouse population has declined by 66-92% over the last

Aldridge, Cameron

386

AN ENERGETICS MODEL FOR THE EXPLOITED YELLOWFIN TUNA, THUNNUS ALBACARES, POPULATION IN  

E-print Network

AN ENERGETICS MODEL FOR THE EXPLOITED YELLOWFIN TUNA, THUNNUS ALBACARES, POPULATION IN THE EASTERN yellowfin tuna, Thunnus albacares, population in the eastern Pacific Ocean is developed. Hydrodynamic to swimming as a function oflength for tunas. Growth and maintenance energetics are estimated and incorporated

387

Population genomics and local adaptation in wild isolates of a model microbial eukaryote  

E-print Network

circumvented these issues in the microbial eukaryote Neurospora crassa by using a "reverse-ecology" populationPopulation genomics and local adaptation in wild isolates of a model microbial eukaryote , and John W. Taylora,1 Departments of a Plant and Microbial Biology and b Molecular and Cell Biology

Dean, Matthew D.

388

A spatial Dirichlet process mixture model for clustering population genetics data  

E-print Network

A spatial Dirichlet process mixture model for clustering population genetics data Brian J. Reich1 Abstract Identifying homogeneous groups of individuals is an important problem in population genet- ics that uses both genetic and spatial information to classify individuals into homogeneous clusters for further

Reich, Brian J.

389

Stochastic and deterministic models for age-structured populations with genetically variable traits  

E-print Network

Stochastic and deterministic models for age-structured populations with genetically variable traits to offspring and may vary due to genetic mutation. Other types of variables include ages, which are increasing of a population with (continuous) age and trait structures. The individuals reproduce asexually, age, interact

Paris-Sud XI, Université de

390

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 is motivated by the fact that, while evolution programs (EPs) in general and genetic algorithms in particular

Kimbrough, Steven Orla

391

Robustness of cheetah asymptotic growth rate and implications to population models  

E-print Network

Robustness of cheetah asymptotic growth rate and implications to population models Joan Lubben1 cheetah (Acinonyx jubatus) is in decline due to hunting, poaching, loss of habitat, lack of genetic diversity and death of cubs due to natural predators such as lions and hyenas. Previous cheetah population

Logan, David

392

SUBLETHAL NARCOSIS AND POPULATION PERSISTENCE: A MODELING STUDY ON GROWTH EFFECTS  

EPA Science Inventory

This study of a Daphnia population model suggests that sublethal effects of nonpolar narcotics on growth of individual organisms can result in ultimate extinction of the population at chronic chemical concentrations near the effect concentration that leads to a 50% reduction in i...

393

Effects of ultraviolet-B radiation on phytoplankton - zooplankton interactions = [Effecten van ultraviolet-B straling op interacties tussen fytoplankton en zooplankton  

Microsoft Academic Search

The decrease in stratospheric ozone concentration has received wide attention because the ozone layer protects the earth from harmful ultraviolet-B radiation (UVB, 280-320 nm). UVB radiation is harmful for organisms, and therefore scientific research into how UVB radiation affects organisms and ecosystems receives great interest. This thesis describes the effects of UVB radiation on interactions between phytoplankton (algae) and zooplankton

Lange de H. J

1999-01-01

394

Effects of physical processes on structure and transport of thin zooplankton layers in the coastal ocean  

USGS Publications Warehouse

Thin layers of plankton are recurrent features in a variety of coastal systems. These layers range in thickness from a few centimeters to a few meters. They can extend horizontally for kilometers and have been observed to persist for days. Densities of organisms found within thin layers are far greater than those above or below the layer, and as a result, thin layers may play an important role in the marine ecosystem. The paramount objective of this study was to understand the physical processes that govern the dynamics of thin layers of zooplankton in the coastal ocean. We deployed instruments to measure physical processes and zooplankton distribution in northern Monterey Bay; during an 11 d period of persistent upwelling-favorable winds, 7 thin zooplankton layers were observed. These zooplankton layers persisted throughout daylight hours, but were observed to dissipate during evening hours. These layers had an average vertical thickness of 1.01 m. No layers were found in regions where the Richardson number was <0.25. In general, when the Richardson number is <0.25 the water column is unstable, and incapable of supporting thin layers. Thin zooplankton layers were also located in regions of reduced flow. In addition, our observations show that the vertical depth distribution of thin zooplankton layers is modulated by high-frequency internal waves, with periods of 18 to 20 min. Results from this study clearly show an association between physical structure, physical processes and the presence of thin zooplankton layers in Monterey Bay. With this new understanding we may identify other coastal regions that have a high probability of supporting thin layers. ?? Inter-Research 2005.

McManus, M.A.; Cheriton, O.M.; Drake, P.J.; Holliday, D.V.; Storlazzi, C.D.; Donaghay, P.L.; Greenlaw, C.F.

2005-01-01

395

North Atlantic summers have warmed more than winters since 1353, and the response of marine zooplankton  

PubMed Central

Modeling and measurements show that Atlantic marine temperatures are rising; however, the low temporal resolution of models and restricted spatial resolution of measurements (i) mask regional details critical for determining the rate and extent of climate variability, and (ii) prevent robust determination of climatic impacts on marine ecosystems. To address both issues for the North East Atlantic, a fortnightly resolution marine climate record from 1353–2006 was constructed for shallow inshore waters and compared to changes in marine zooplankton abundance. For the first time summer marine temperatures are shown to have increased nearly twice as much as winter temperatures since 1353. Additional climatic instability began in 1700 characterized by ?5–65 year climate oscillations that appear to be a recent phenomenon. Enhanced summer-specific warming reduced the abundance of the copepod Calanus finmarchicus, a key food item of cod, and led to significantly lower projected abundances by 2040 than at present. The faster increase of summer marine temperatures has implications for climate projections and affects abundance, and thus biomass, near the base of the marine food web with potentially significant feedback effects for marine food security. PMID:21148422

Kamenos, Nicholas A.

2010-01-01

396

Integration of Density Dependence and Concentration Response Models Provides an Ecologically Relevant Assessment of Populations Exposed to Toxicants  

EPA Science Inventory

The assessment of toxic exposure on wildlife populations involves the integration of organism level effects measured in toxicity tests (e.g., chronic life cycle) and population models. These modeling exercises typically ignore density dependence, primarily because information on ...

397

Population persistence of stream fish in response to environmental change: integrating data and models across space  

NASA Astrophysics Data System (ADS)

For stream fishes, environmental variation is a key driver of individual body growth/movement/survival and, by extension, population dynamics. Identifying how stream fish respond to environmental variation can help clarify mechanisms responsible for population dynamics and can help provide tools to forecast relative resilience of populations across space. Forecasting dynamics across space is challenging, however, because it can be difficult to conduct enough studies with enough intensity to fully characterize broad-scale population response to environmental change. We have adopted a multi-scale approach, using detailed individual-based studies and analyses (integral projection matrix) to determine sensitivities of population growth to environmental variation combined with broad spatial data and analyses (occupancy and abundance models) to estimate patterns of population response across space. Population growth of brook trout was most sensitive to stream flow in the spring and winter, most sensitive to stream temperature in the fall and sensitive to both flow and temperature in the summer. High flow in the spring and winter had negative effects on population growth while high temperature had a negative effect in the fall. Flow had no effect when it was cold, but a positive effect when it was warm in the summer. Combined with occupancy and abundance models, these data give insight into the spatial structure of resilient populations and can help guide prioritization of management actions.

Letcher, B. H.; Schueller, P.; Bassar, R.; Coombs, J.; Rosner, A.; Sakrejda, K.; Kanno, Y.; Whiteley, A.; Nislow, K. H.

2013-12-01

398

Population Synthesis in the Blue. IV. Accurate Model Predictions for Lick Indices and UBV Colors in Single Stellar Populations  

NASA Astrophysics Data System (ADS)

We present a new set of model predictions for 16 Lick absorption line indices from H? through Fe5335 and UBV colors for single stellar populations with ages ranging between 1 and 15 Gyr, [Fe/H] ranging from -1.3 to +0.3, and variable abundance ratios. The models are based on accurate stellar parameters for the Jones library stars and a new set of fitting functions describing the behavior of line indices as a function of effective temperature, surface gravity, and iron abundance. The abundances of several key elements in the library stars have been obtained from the literature in order to characterize the abundance pattern of the stellar library, thus allowing us to produce model predictions for any set of abundance ratios desired. We develop a method to estimate mean ages and abundances of iron, carbon, nitrogen, magnesium, and calcium that explores the sensitivity of the various indices modeled to those parameters. The models are compared to high-S/N data for Galactic clusters spanning the range of ages, metallicities, and abundance patterns of interest. Essentially all line indices are matched when the known cluster parameters are adopted as input. Comparing the models to high-quality data for galaxies in the nearby universe, we reproduce previous results regarding the enhancement of light elements and the spread in the mean luminosity-weighted ages of early-type galaxies. When the results from the analysis of blue and red indices are contrasted, we find good consistency in the [Fe/H] that is inferred from different Fe indices. Applying our method to estimate mean ages and abundances from stacked SDSS spectra of early-type galaxies brighter than L*, we find mean luminosity-weighed ages of the order of ~8 Gyr and iron abundances slightly below solar. Abundance ratios, [X/Fe], tend to be higher than solar and are positively correlated with galaxy luminosity. Of all elements, nitrogen is the more strongly correlated with galaxy luminosity, which seems to indicate secondary nitrogen enrichment. If that interpretation is correct, this result may impose a lower limit of 50-200 Myr to the timescale of star formation in early-type galaxies. Unlike clusters, galaxies show a systematic effect whereby higher order, bluer, Balmer lines yield younger ages than H?. This age discrepancy is stronger for lower luminosity galaxies. We examine four possible scenarios to explain this trend. Contamination of the bluer indices by a metal-poor stellar population with a blue horizontal branch cannot account for the data. Blue stragglers and abundance-ratio effects cannot be ruled out, as they can potentially satisfy the data, even though this can only be achieved by resorting to extreme conditions, such as extremely high [O/Fe] or specific blue-straggler frequencies. The most likely explanation is the presence of small amounts of a young/intermediate-age stellar population component. We simulate this effect by producing two-component models and show that they provide a reasonably good match to the data when the mass fraction of the young component is typically a few percent. If confirmed, this result implies star formation has been extended in early-type galaxies, and more so in less massive galaxies, which seems to lend support to the ``downsizing'' scenario. Moreover, it implies that stellar population synthesis models are capable of constraining not only the mean ages of stellar populations in galaxies, but also their age spread.

Schiavon, Ricardo P.

2007-07-01

399

Collocation method using sinc and Rational Legendre functions for solving Volterra’s population model  

Microsoft Academic Search

This paper proposes two approximate methods to solve Volterra’s population model for population growth of a species in a closed system. Volterra’s model is a nonlinear integro-differential equation on a semi-infinite interval, where the integral term represents the effect of toxin. The proposed methods have been established based on collocation approach using Sinc functions and Rational Legendre functions. They are

K. Parand

2011-01-01

400

Establishing a beachhead: A stochastic population model with an Allee effect applied to species invasion  

USGS Publications Warehouse

We formulated a spatially explicit stochastic population model with an Allee effect in order to explore how invasive species may become established. In our model, we varied the degree of migration between local populations and used an Allee effect with variable birth and death rates. Because of the stochastic component, population sizes below the Allee effect threshold may still have a positive probability for successful invasion. The larger the network of populations, the greater the probability of an invasion occurring when initial population sizes are close to or above the Allee threshold. Furthermore, if migration rates are low, one or more than one patch may be successfully invaded, while if migration rates are high all patches are invaded. ?? 2007 Elsevier Inc. All rights reserved.

Ackleh, A.S.; Allen, L.J.S.; Carter, J.

2007-01-01

401

Dynamical properties of the Penna aging model applied to the population of wolves  

NASA Astrophysics Data System (ADS)

The parameters of th Penna bit-string model of aging of biological systems are systematically tested to better understand the model itself as well as the results arising from applying this model to studies of the development of the stationary population of Alaska wolves.

Makowiec, Danuta

1997-02-01

402

Bayesian Modeling of Space-Time Properties of Infectious Disease in a College Student Population  

E-print Network

Bayesian Modeling of Space-Time Properties of Infectious Disease in a College Student Population 1Z statistical model is developed for analysis of the time-evolving properties of infectious disease of the model results. Keywords: Infectious disease, Bayesian, semi-Markov I. INTRODUCTION There has been

Carin, Lawrence

403

MANAGING PLANT POPULATION SPREAD: PREDICTION AND ANALYSIS USING A SIMPLE MODEL  

Microsoft Academic Search

Models can be used to direct the management of population spread for the control of invasives or to encourage species of conservation value. Analytical models are attractive because of their theoretical basis and limited data requirements, but there is concern that their simplicity may limit their practical utility. We address the applied use of simple models in a study of

James M. Bullock; Richard F. Pywell; Sarah J. Coulson-Phillips

2008-01-01

404

POPULATION EXPOSURES TO PARTICULATE MATTER: A COMPARISON OF EXPOSURE MODEL PREDICTIONS AND MEASUREMENT DATA  

EPA Science Inventory

The US EPA National Exposure Research Laboratory (NERL) is currently developing an integrated human exposure source-to-dose modeling system (HES2D). This modeling system will incorporate models that use a probabilistic approach to predict population exposures to environmental ...

405

ESTIMATING POPULATION SIZE IN PROPORTIONAL TRAPPING-REMOVAL MODELS  

Microsoft Academic Search

We examine the inference problem of a proportional trapping model intro- duced by Good, Lewis, Gaskins and Howell (1979), and consider a similar removal model in continuous time. The existence and uniqueness of the maximum likeli- hood estimates of the parameters are studied. Corresponding variance estimates are also given. Martingale theory is used to obtain the asymptotic properties, and simulations

Liping Liu; Paul S. F. Yip

2003-01-01

406

An isotopic (?14C, ?13C, and ?15N) investigation of the composition of particulate organic matter and zooplankton food sources in Lake Superior and across a size-gradient of aquatic systems  

NASA Astrophysics Data System (ADS)

Food webs in aquatic systems can be supported both by carbon from recent local primary productivity and by carbon subsidies, such as material from terrestrial ecosystems, or past in situ primary productivity. The importance of these subsidies to respiration and biomass production remains a topic of debate. While some studies have reported that terrigenous organic carbon supports disproportionately high zooplankton production, others have suggested that phytoplankton preferentially support zooplankton production in aquatic ecosystems. Here we apply natural abundance radiocarbon (?14C) and stable isotope (?13C, ?15N) analyses to show that zooplankton in Lake Superior selectively incorporate recently fixed, locally produced (autochthonous) organic carbon even though other carbon sources are readily available. Estimates from Bayesian isotopic modeling based on ?14C and ?13C values show that the average lake-wide median contributions of recent in-lake primary production and terrestrial, sedimentary, and bacterial organic carbon to the bulk POM in Lake Superior were 58%, 5%, 33%, and 3%, respectively. However, isotopic modeling estimates also show that recent in situ production contributed a disproportionately large amount (median, 91%) of the carbon in mesozooplankton biomass in Lake Superior. Although terrigenous organic carbon and old organic carbon from resuspended sediments were significant portions (median, 38%) of the available basal food resources, these contributed only a small amount to mesozooplankton biomass. Comparison of zooplankton food sources based on their radiocarbon composition showed that terrigenous organic carbon was relatively more important in rivers and small lakes, and the proportion of terrestrially derived material used by zooplankton correlated with the hydrologic residence time and the ratio of basin area to water surface area.

Zigah, P. K.; Minor, E. C.; Werne, J. P.; McCallister, S. Leigh

2012-09-01

407

Zooplankton Atlas of the Southern Ocean: The SCAR SO-CPR Survey (1991-2008)  

NASA Astrophysics Data System (ADS)

The SCAR Southern Ocean Continuous Plankton Recorder (SO-CPR) Survey produces one of the largest and most accessed zooplankton data sets in the world. These data serve as a reference for other Southern Ocean monitoring programmes such as those run by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) and the developing Southern Ocean Observing System (SOOS). It has been instrumental in providing baseline data on zooplankton composition, communities, and distribution patterns on the ocean basin scale. The SO-CPR Survey is publishing the first detailed geographical atlas of the near-surface Southern Ocean zooplankton. This atlas is based on 22,553 CPR samples collected from 1991 to 2008 from voyages operated by Australia, Japan, Germany, New Zealand, USA and Russia. The Atlas documents the distribution and abundance of the 50 most abundant zooplankton taxa amongst the 200+ taxa sampled. The maps are printed in alphabetical order of the genera within each taxon and nomenclature is based on the Register of Antarctic Marine Species (RAMS) developed by the SCAR Marine Biodiversity Information Network (SCAR-MarBIN). The SO-CPR Atlas will operate as a ready reference to researchers interested in the distribution of zooplankton in the Southern Ocean, for example knowing the distribution of grazers in relation to phytoplankton production or the availability of prey for higher predators.

McLeod, David J.; Hosie, Graham W.; Kitchener, John A.; Takahashi, Kunio T.; Hunt, Brian P. V.

2010-08-01

408

Combined effect of predatory zooplankton and allelopathic aquatic macrophytes on algal suppression.  

PubMed

The present study evaluated the combined effects of four typical predatory zooplankton and allelopathic aquatic macrophytes on algal control in a microcosm system. It would determine the effects of diverse species and biological restoration on the growth of harmful water-bloom microalgae in great lakes polluted by excess nutrients. It was found that the mixtures of each zooplankton and the floating plant Nymphoides peltatum had stronger inhibitory effects on harmful water-bloom microalgae than the individual species in clean or eutrophic water bodies. In addition, a community of four zooplankton types had a synergistic effect on algal inhibition. Algal suppression by the zooplankton community was enhanced significantly when the macrophyte was co-cultured in the microcosm. Furthermore, Chlorella pyrenoidosa was more susceptible than Microcystis aeruginosa when exposed to grazing by zooplankton and the allelopathic potential of the macrophyte. Algal inhibition was also weaker in eutrophic conditions compared with the control. These findings indicate that diverse species may enhance algal inhibition. Therefore, it is necessary to restore biological diversity and rebuild an ecologically balanced food chain or web to facilitate the control of harmful algal blooms in eutrophic lakes. PMID:25409583

Zuo, Shengpeng; Wan, Kun; Ma, Sumin

2015-01-01

409

Variability of zooplankton communities at Condor seamount and surrounding areas, Azores (NE Atlantic)  

NASA Astrophysics Data System (ADS)

Seamounts are common topographic features around the Azores archipelago (NE Atlantic). Recently there has been increasing research effort devoted to the ecology of these ecosystems. In the Azores, the mesozooplankon is poorly studied, particularly in relation to these seafloor elevations. In this study, zooplankton communities in the Condor seamount area (Azores) were investigated during March, July and September 2010. Samples were taken during both day and night with a Bongo net of 200 µm mesh that towed obliquely within the first 100 m of the water column. Total abundance, biomass and chlorophyll a concentrations did not vary with sampling site or within the diel cycle but significant seasonal variation was observed. Moreover, zooplankton community composition showed the same strong seasonal pattern regardless of spatial or daily variability. Despite seasonal differences, the zooplankton community structure remained similar for the duration of this study. Seasonal variability better explained our results than mesoscale spatial variability. Spatial homogeneity is probably related with island proximity and local dynamics over Condor seamount. Zooplankton literature for the region is sparse, therefore a short review of the most important zooplankton studies from the Azores is also presented.

Carmo, Vanda; Santos, Mariana; Menezes, Gui M.; Loureiro, Clara M.; Lambardi, Paolo; Martins, Ana

2013-12-01

410

Spatiotemporal statistical analyses reveal predator-driven zooplankton fluctuations in the Barents Sea  

NASA Astrophysics Data System (ADS)

There is limited statistical support for top-down effects on plankton in oceanic ecosystems. We quantify the combined effects of key planktivorous fish, invertebrates and climate on mesozooplankton dynamics in the Barents Sea. Zooplankton biomass was measured during Russian and Norwegian surveys in April-May and June-July 1959-1990 and August-early October (1981) 1984-2010. We found that zooplankton biomass in the central and northern Barents Sea in August-October showed pronounced multi-year fluctuations that were strongly negatively correlated with the total biomass of planktivorous fish. Fish predation explained >50% of the interannual variability in the biomass of medium-sized and large mesozooplankton in these parts of the Barents Sea and the predation effects remained significant while accounting for effects of climate variables. Spatiotemporal statistical analyses for different zooplankton size fractions supported the interpretation of top-down control, predominantly from capelin, on the zooplankton. In the southwestern Barents Sea the fluctuations were less pronounced and uncorrelated to total biomass of planktivorous fish, suggesting weaker top-down control by fish in this region, characterised by higher productivity and higher diversity of the predators. We suggest that predator-driven zooplankton fluctuations may play an important role in the ecosystem dynamics of the Barents Sea and potentially other Arcto-boreal shelves.

Stige, Leif Christian; Dalpadado, Padmini; Orlova, Emma; Boulay, Anne-Cécile; Durant, Joël M.; Ottersen, Geir; Stenseth, Nils Chr.

2014-01-01

411

Effects of ultraviolet radiation on pigmentation, photoenzymatic repair, behavior, and community ecology of zooplankton.  

PubMed

In this report, we provide a perspective on how zooplankton are able to respond to present and future levels of ultraviolet (UV) radiation, a threat that has been present throughout evolutionary time. To cope with this threat, zooplankton have evolved several adaptations including behavioral responses, repair systems, and accumulation of photoprotective compounds. Common photoprotective compounds include melanins and carotenoids, which are true pigments, but also mycosporine-like amino acids (MAAs) and several other substances, and different taxa use different blends of these compounds. It is not only the level of UV radiation, however, that determines the amount of photoprotective compounds incorporated by the zooplankton, but also other environmental factors, such as predation and supply rate of the compounds. Furthermore, compared to taxa that are less pigmented, those taxa with ample pigmentation are generally less likely to exhibit diel migration. The photoenzymatic repair of UV damages seems to be more efficient at intermediate temperature than at low and high temperatures, suggesting that it is less useful at high and low latitudes, where UV radiation is often extremely high. While predicted future increases in UV radiation are expected to substantially affect many processes, recent studies show that most zooplankton taxa are well adapted to cope with such increases, either by UV avoidance behavior or by incorporation of photoprotective compounds. Hence, we conclude that future increase in UV radiation will have only moderate direct effects on zooplankton biomass and community dynamics. PMID:19707615

Hansson, Lars-Anders; Hylander, Samuel

2009-09-01

412

Trophic transfer of cyanobacterial toxins from zooplankton to planktivores: consequences for pike larvae and mysid shrimps.  

PubMed

The aim of this study was to evaluate the potentially harmful effects of zooplankton preexposed to cyanobacteria on two planktivorous animals: a fish larva (pike, Esox lucius) and a mysid shrimp (Neomysis integer). The planktivores were fed zooplankton from a natural community that had been preexposed to cell-free extract or to purified toxin (nodularin) of the cyanobacterium Nodularia spumigena, and the growth, feeding, and pellet production of the planktivores, as well as the toxin content of the pellets, were measured. In addition, radiolabeled nodularin ((3)H-dihydronodularin) was used in separate experiments to measure the vector transfer of nodularin from zooplankton to their predators. During 11-day exposures, dissolved nodularin was transferred to pike larvae and N. integer via zooplankton at very low rates of accumulation. Treatment with N. spumigena extract decreased the ingestion and feces production rates of pike larvae. With purified nodularin alone, no such effect could be observed. No effect on molting cycle length, fecal pellet production, C:N ratio, or growth of N. integer was detected. The results suggest that dissolved cyanobacterial toxins released during bloom decay can have a negative impact on feeding and, hence, on the growth of fish larvae via zooplankton, even without direct contact between cyanobacteria and the fish. PMID:15892036

Karjalainen, Miina; Reinikainen, Marko; Spoof, Lisa; Meriluoto, Jussi A O; Sivonen, Kaarina; Viitasalo, Markku

2005-06-01

413

Neural Population Dynamics Modeled by Mean-Field Graphs  

NASA Astrophysics Data System (ADS)

In this work we apply random graph theory approach to describe neural population dynamics. There are important advantages of using random graph theory approach in addition to ordinary and partial differential equations. The mathematical theory of large-scale random graphs provides an efficient tool to describe transitions between high- and low-dimensional spaces. Recent advances in studying neural correlates of higher cognition indicate the significance of sudden changes in space-time neurodynamics, which can be efficiently described as phase transitions in the neuropil medium. Phase transitions are rigorously defined mathematically on random graph sequences and they can be naturally generalized to a class of percolation processes called neuropercolation. In this work we employ mean-field graphs with given vertex degree distribution and edge strength distribution. We demonstrate the emergence of collective oscillations in the style of brains.

Kozma, Robert; Puljic, Marko

2011-09-01

414

Geospatial Modeling of Asthma Population in Relation to Air Pollution  

NASA Technical Reports Server (NTRS)

Current observations indicate that asthma is growing every year in the United States, specific reasons for this are not well understood. This study stems from an ongoing research effort to investigate the spatio-temporal behavior of asthma and its relatedness to air pollution. The association between environmental variables such as air quality and asthma related health issues over Mississippi State are investigated using Geographic Information Systems (GIS) tools and applications. Health data concerning asthma obtained from Mississippi State Department of Health (MSDH) for 9-year period of 2003-2011, and data of air pollutant concentrations (PM2.5) collected from USEPA web resources, and are analyzed geospatially to establish the impacts of air quality on human health specifically related to asthma. Disease mapping using geospatial techniques provides valuable insights into the spatial nature, variability, and association of asthma to air pollution. Asthma patient hospitalization data of Mississippi has been analyzed and mapped using quantitative Choropleth techniques in ArcGIS. Patients have been geocoded to their respective zip codes. Potential air pollutant sources of Interstate highways, Industries, and other land use data have been integrated in common geospatial platform to understand their adverse contribution on human health. Existing hospitals and emergency clinics are being injected into analysis to further understand their proximity and easy access to patient locations. At the current level of analysis and understanding, spatial distribution of Asthma is observed in the populations of Zip code regions in gulf coast, along the interstates of south, and in counties of Northeast Mississippi. It is also found that asthma is prevalent in most of the urban population. This GIS based project would be useful to make health risk assessment and provide information support to the administrators and decision makers for establishing satellite clinics in future.

Kethireddy, Swatantra R.; Tchounwou, Paul B.; Young, John H.; Luvall, Jeffrey C.; Alhamdan, Mohammad

2013-01-01

415

Population Characteristics, Development of a Predictive Population Viability Model, and Catch Dynamics for Pallid Sturgeon in the Lower Missouri River.  

E-print Network

??Population characteristics and long-term population trends of pallid sturgeon Scaphirhynchus albus in the lower Missouri River are relatively unknown. As recovery efforts continue, understanding and… (more)

Steffensen, Kirk D.

2012-01-01

416

A Bayesian population PBPK model for multiroute chloroform exposure  

PubMed Central

A Bayesian hierarchical model was developed to estimate the parameters in a physiologically based pharmacokinetic (PBPK) model for chloroform using prior information and biomarker data from different exposure pathways. In particular, the model provides a quantitative description of the changes in physiological parameters associated with hot-water bath and showering scenarios. Through Bayesian inference, uncertainties in the PBPK parameters were reduced from the prior distributions. Prediction of biomarker data with the calibrated PBPK model was improved by the calibration. The posterior results indicate that blood flow rates varied under two different exposure scenarios, with a two-fold increase of the skin's blood flow rate predicted in the hot-bath scenario. This result highlights the importance of considering scenario-specific parameters in PBPK modeling. To demonstrate the application of a probability approach in toxicological assessment, results from the posterior distributions from this calibrated model were used to predict target tissue dose based on the rate of chloroform metabolized in liver. This study demonstrates the use of the Bayesian approach to optimize PBPK model parameters for typical household exposure scenarios. PMID:19471319

Yang, Yuching; Xu, Xu; Georgopoulos, Panos G.

2011-01-01

417

Comparison of individual-based modeling and population approaches for prediction of foodborne pathogens growth.  

PubMed

Individual-based modeling (IBM) approach combined with the microenvironment modeling of vacuum-packed cold-smoked salmon was more effective to describe the variability of the growth of a few Listeria monocytogenes cells contaminating irradiated salmon slices than the traditional population models. The IBM approach was particularly relevant to predict the absence of growth in 25% (5 among 20) of artificially contaminated cold-smoked salmon samples stored at 8 °C. These results confirmed similar observations obtained with smear soft cheese (Ferrier et al., 2013). These two different food models were used to compare the IBM/microscale and population/macroscale modeling approaches in more global exposure and risk assessment frameworks taking into account the variability and/or the uncertainty of the factors influencing the growth of L. monocytogenes. We observed that the traditional population models significantly overestimate exposure and risk estimates in comparison to IBM approach when contamination of foods occurs with a low number of cells (<100 per serving). Moreover, the exposure estimates obtained with the population model were characterized by a great uncertainty. The overestimation was mainly linked to the ability of IBM to predict no growth situations rather than the consideration of microscale environment. On the other hand, when the aim of quantitative risk assessment studies is only to assess the relative impact of changes in control measures affecting the growth of foodborne bacteria, the two modeling approach gave similar results and the simplest population approach was suitable. PMID:25500386

Augustin, Jean-Christophe; Ferrier, Rachel; Hezard, Bernard; Lintz, Adrienne; Stahl, Valérie

2015-02-01

418

The importance of individual developmental variation in stage-structured population models.  

PubMed

Population stage structure is fundamental to ecology, and models of this structure have proven useful in many different systems. Many ecological variables other than stage, such as habitat type, site occupancy and metapopulation status are also modelled using transitions among discrete states. Transitions among life stages can be characterised by the distribution of time spent in each stage, including the mean and variance of each stage duration and within-individual correlations among multiple stage durations. Three modelling traditions represent stage durations differently. Matrix models can be derived as a long-run approximation from any distribution of stage durations, but they are often interpreted directly as a Markov model for stage transitions. Statistical stage-duration distribution models accommodate the variation typical of cohort development data, but such realism has rarely been incorporated in population theory or statistical population models. Delay-differential equation models include lags but no variation, except in limited cases. We synthesise these models in one framework and illustrate how individual variation and correlations in development can impact population growth. Furthermore, different development models can yield the same long-term matrix transition rates but different sensitivities and elasticities. Finally, we discuss future directions for estimating realistic stage duration models from data. PMID:24811267

de Valpine, Perry; Scranton, Katherine; Knape, Jonas; Ram, Karthik; Mills, Nicholas J

2014-08-01

419

Image-Driven Population Analysis Through Mixture Modeling  

E-print Network

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 ...

Shenton, Martha E.

420

A PROBABILISTIC MODELING FRAMEWORK FOR PREDICTING POPULATION EXPOSURES TO BENZENE  

EPA Science Inventory

The US Environmental Protection Agency (EPA) is modifying their probabilistic Stochastic Human Exposure Dose Simulation (SHEDS) model to assess aggregate exposures to air toxics. Air toxics include urban Hazardous Air Pollutants (HAPS) such as benzene from mobile sources, part...

421

A sub-cellular viscoelastic model for cell population mechanics.  

PubMed

Understanding the biomechanical properties and the effect of biomechanical force on epithelial cells is key to understanding how epithelial cells form uniquely shaped structures in two or three-dimensional space. Nevertheless, with the limitations and challenges posed by biological experiments at this scale, it becomes advantageous to use mathematical and 'in silico' (computational) models as an alternate solution. This paper introduces a single-cell-based model representing the cross section of a typical tissue. Each cell in this model is an individual unit containing several sub-cellular elements, such as the elastic plasma membrane, enclosed viscoelastic elements that play the role of cytoskeleton, and the viscoelastic elements of the cell nucleus. The cell membrane is divided into segments where each segment (or point) incorporates the cell's interaction and communication with other cells and its environment. The model is capable of simulating how cells cooperate and contribute to the overall structure and function of a particular tissue; it mimics many aspects of cellular behavior such as cell growth, division, apoptosis and polarization. The model allows for investigation of the biomechanical properties of cells, cell-cell interactions, effect of environment on cellular clusters, and how individual cells work together and contribute to the structure and function of a particular tissue. To evaluate the current approach in modeling different topologies of growing tissues in distinct biochemical conditions of the surrounding media, we model several key cellular phenomena, namely monolayer cell culture, effects of adhesion intensity, growth of epithelial cell through interaction with extra-cellular matrix (ECM), effects of a gap in the ECM, tensegrity and tissue morphogenesis and formation of hollow epithelial acini. The proposed computational model enables one to isolate the effects of biomechanical properties of individual cells and the communication between cells and their microenvironment while simultaneously allowing for the formation of clusters or sheets of cells that act together as one complex tissue. PMID:20856895

Jamali, Yousef; Azimi, Mohammad; Mofrad, Mohammad R K

2010-01-01

422

Population dynamics of California sea otters and a model for the risk of oil spills  

SciTech Connect

In an effort to estimate parameters in the density dependence function used in the simulation model, an analysis of the recent historical growth and range expansion of the population was undertaken. Simple deterministic models that included feedback between population growth and range expansion were built, some including a density independent mortality rate after 1972 to investigate the effect of incidental drowning in fishing-nets. Analysis of model output indicated that the density dependence function in the actual population is probably very rectangular. Range length may hamper the dispersal of young males out of the central part of the range. The apparent decline in population in the 1970's may be due to this slowing range expansion coinciding with the onset of fishing-net mortality.

Brody, A.J.

1988-01-01

423

Perspective: The Climate-Population-Infrastructure Modeling and Simulation Fertile Area for New Research  

SciTech Connect

Managing the risks posed by climate change and extreme weather to energy production and delivery is a challenge to communities worldwide. As climate conditions change, populations will shift, and demand will re-locate; and networked infrastructures will evolve to accommodate new load centers, and, hopefully, minimize vulnerability to natural disaster. Climate effects such as sea level rise, increased frequency and intensity of natural disasters, force populations to move locations. Displaced population creates new demand for built infrastructure that in turn generates new economic activity that attracts new workers and associated households to the new locations. Infrastructures and their interdependencies will change in reaction to climate drivers as the networks expand into new population areas and as portions of the networks are abandoned as people leave. Thus, infrastructures will evolve to accommodate new load centers while some parts of the network are underused, and these changes will create emerging vulnerabilities. Forecasting the location of these vulnerabilities by combining climate predictions and agent based population movement models shows promise for defining these future population distributions and changes in coastal infrastructure configurations. By combining climate and weather data, engineering algorithms and social theory it has been only recently possible to examine electricity demand response to increased climactic temperatures, population relocation in response to extreme cyclonic events, consequent net population changes and new regional patterns in electricity demand. These emerging results suggest a research agenda of coupling these disparate modelling approaches to understand the implications of climate change for protecting the nation s critical infrastructure.

Allen, Melissa R [ORNL; Fernandez, Steven J [ORNL; Walker, Kimberly A [ORNL; Fu, Joshua S [ORNL

2014-01-01

424

Modeling the Pre-Industrial Roots of Modern Super-Exponential Population Growth  

PubMed Central

To Malthus, rapid human population growth—so evident in 18th Century Europe—was obviously unsustainable. In his Essay on the Principle of Population, Malthus cogently argued that environmental and socioeconomic constraints on population rise were inevitable. Yet, he penned his essay on the eve of the global census size reaching one billion, as nearly two centuries of super-exponential increase were taking off. Introducing a novel extension of J. E. Cohen's hallmark coupled difference equation model of human population dynamics and carrying capacity, this article examines just how elastic population growth limits may be in response to demographic change. The revised model involves a simple formalization of how consumption costs influence carrying capacity elasticity over time. Recognizing that complex social resource-extraction networks support ongoing consumption-based investment in family formation and intergenerational resource transfers, it is important to consider how consumption has impacted the human environment and demography—especially as global population has become very large. Sensitivity analysis of the consumption-cost model's fit to historical population estimates, modern census data, and 21st Century demographic projections supports a critical conclusion. The recent population explosion was systemically determined by long-term, distinctly pre-industrial cultural evolution. It is suggested that modern globalizing transitions in technology, susceptibility to infectious disease, information flows and accumulation, and economic complexity were endogenous products of much earlier biocultural evolution of family formation's embeddedness in larger, hierarchically self-organizing cultural systems, which could potentially support high population elasticity of carrying capacity. Modern super-exponential population growth cannot be considered separately from long-term change in the multi-scalar political economy that connects family formation and intergenerational resource transfers to wider institutions and social networks. PMID:25141019

Stutz, Aaron Jonas

2014-01-01

425

The temporal spectrum of adult mosquito population fluctuations: conceptual and modeling implications.  

PubMed

An improved understanding of mosquito population dynamics under natural environmental forcing requires adequate field observations spanning the full range of temporal scales over which mosquito abundance fluctuates in natural conditions. Here we analyze a 9-year daily time series of uninterrupted observations of adult mosquito abundance for multiple mosquito species in North Carolina to identify characteristic scales of temporal variability, the processes generating them, and the representativeness of observations at different sampling resolutions. We focus in particular on Aedes vexans and Culiseta melanura and, using a combination of spectral analysis and modeling, we find significant population fluctuations with characteristic periodicity between 2 days and several years. Population dynamical modelling suggests that the observed fast fluctuations scales (2 days-weeks) are importantly affected by a varying mosquito activity in response to rapid changes in meteorological conditions, a process neglected in most representations of mosquito population dynamics. We further suggest that the range of time scales over which adult mosquito population variability takes place can be divided into three main parts. At small time scales (indicatively 2 days-1 month) observed population fluctuations are mainly driven by behavioral responses to rapid changes in weather conditions. At intermediate scales (1 to several month) environmentally-forced fluctuations in generation times, mortality rates, and density dependence determine the population characteristic response times. At longer scales (annual to multi-annual) mosquito populations follow seasonal and inter-annual environmental changes. We conclude that observations of adult mosquito populations should be based on a sub-weekly sampling frequency and that predictive models of mosquito abundance must include behavioral dynamics to separate the effects of a varying mosquito activity from actual changes in the abundance of the underlying population. PMID:25478861

Jian, Yun; Silvestri, Sonia; Brown, Jeff; Hickman, Rick; Marani, Marco

2014-01-01

426

The Temporal Spectrum of Adult Mosquito Population Fluctuations: Conceptual and Modeling Implications  

PubMed Central

An improved understanding of mosquito population dynamics under natural environmental forcing requires adequate field observations spanning the full range of temporal scales over which mosquito abundance fluctuates in natural conditions. Here we analyze a 9-year daily time series of uninterrupted observations of adult mosquito abundance for multiple mosquito species in North Carolina to identify characteristic scales of temporal variability, the processes generating them, and the representativeness of observations at different sampling resolutions. We focus in particular on Aedes vexans and Culiseta melanura and, using a combination of spectral analysis and modeling, we find significant population fluctuations with characteristic periodicity between 2 days and several years. Population dynamical modelling suggests that the observed fast fluctuations scales (2 days-weeks) are importantly affected by a varying mosquito activity in response to rapid changes in meteorological conditions, a process neglected in most representations of mosquito population dynamics. We further suggest that the range of time scales over which adult mosquito population variability takes place can be divided into three main parts. At small time scales (indicatively 2 days-1 month) observed population fluctuations are mainly driven by behavioral responses to rapid changes in weather conditions. At intermediate scales (1 to several month) environmentally-forced fluctuations in generation times, mortality rates, and density dependence determine the population characteristic response times. At longer scales (annual to multi-annual) mosquito populations follow seasonal and inter-annual environmental changes. We conclude that observations of adult mosquito populations should be based on a sub-weekly sampling frequency and that predictive models of mosquito abundance must include behavioral dynamics to separate the effects of a varying mosquito activity from actual changes in the abundance of the underlying population. PMID:25478861

Jian, Yun; Silvestri, Sonia; Brown, Jeff; Hickman, Rick; Marani, Marco

2014-01-01

427

Hierarchical modeling of population stability and species group attributes from survey data  

USGS Publications Warehouse

Many ecological studies require analysis of collections of estimates. For example, population change is routinely estimated for many species from surveys such as the North American Breeding Bird Survey (BBS), and the species are grouped and used in comparative analyses. We developed a hierarchical model for estimation of group attributes from a collection of estimates of population trend. The model uses information from predefined groups of species to provide a context and to supplement data for individual species; summaries of group attributes are improved by statistical methods that simultaneously analyze collections of trend estimates. The model is Bayesian; trends are treated as random variables rather than fixed parameters. We use Markov Chain Monte Carlo (MCMC) methods to fit the model. Standard assessments of population stability cannot distinguish magnitude of trend and statistical significance of trend estimates, but the hierarchical model allows us to legitimately describe the probability that a trend is within given bounds. Thus we define population stability in terms of the probability that the magnitude of population change for a species is less than or equal to a predefined threshold. We applied the model to estimates of trend for 399 species from the BBS to estimate the proportion of species with increasing populations and to identify species with unstable populations. Analyses are presented for the collection of all species and for 12 species groups commonly used in BBS summaries. Overall, we estimated that 49% of species in the BBS have positive trends and 33 species have unstable populations. However, the proportion of species with increasing trends differs among habitat groups, with grassland birds having only 19% of species with positive trend estimates and wetland birds having 68% of species with positive trend estimates.

Sauer, J.R.; Link, W.A.

2002-01-01

428

UV-enhanced fish predation and the differential migration of zooplankton in response to UV radiation and fish  

E-print Network

radiation and fish Dina M. Leech,a,* Wiebke J. Boeing,b Sandra L. Cooke,c Craig E. Williamson,d and Lisette to influence fish predation on zooplankton. However, in clear-water systems, ultraviolet (UV) radiation (UVR-transparent or UV-blocking columns suspended in the epilimnion. Zooplankton consumption by young-of-the-year (YOY

Williamson, Craig E.

429

Wax esters in tropical zooplankton and nekton and the geographical distribution of wax esters in marine copepods  

Microsoft Academic Search

Analyses of zooplankton and nekton from the central South Pacific showed that surface an d epipclagic zooplankton had small amounts of neutral lipids, mainly triglyccridcs, while deep-water tropical copepods had wax esters as the major lipid type, presumed to function as a rcscrvc srtoragc. The total lipid content and wax esters of tropical copepods captured at about 500 m were

RICHARD F. LEE; JED HIROTA

1973-01-01

430

Refining Reproductive Parameters for Modelling Sustainability and Extinction in Hunted Primate Populations in the Amazon  

PubMed Central

Primates are frequently hunted in Amazonia. Assessing the sustainability of hunting is essential to conservation planning. The most-used sustainability model, the ‘Production Model’, and more recent spatial models, rely on basic reproductive parameters for accuracy. These parameters are often crudely estimated. To date, parameters used for the Amazon’s most-hunted primate, the woolly monkey (Lagothrix spp.), come from captive populations in the 1960s, when captive births were rare. Furthermore, woolly monkeys have since been split into five species. We provide reproductive parameters calculated by examining the reproductive organs of female Poeppig’s woolly monkeys (Lagothrix poeppigii), collected by hunters as part of their normal subsistence activity. Production was 0.48–0.54 young per female per year, and an interbirth interval of 22.3 to 25.2 months, similar to parameters from captive populations. However, breeding was seasonal, which imposes limits on the maximum reproductive rate attainable. We recommend the use of spatial models over the Production Model, since they are less sensitive to error in estimated reproductive rates. Further refinements to reproductive parameters are needed for most primate taxa. Methods like ours verify the suitability of captive reproductive rates for sustainability analysis and population modelling for populations under differing conditions of hunting pressure and seasonality. Without such research, population modelling is based largely on guesswork. PMID:24714614

Bowler, Mark; Anderson, Matt; Montes, Daniel; Pérez, Pedro; Mayor, Pedro

2014-01-01

431

Experimental demonstration of a two-phase population extinction hazard  

PubMed Central

Population extinction is a fundamental biological process with applications to ecology, epidemiology, immunology, conservation biology and genetics. Although a monotonic relationship between initial population size and mean extinction time is predicted by virtually all theoretical models, attempts at empirical demonstration have been equivocal. We suggest that this anomaly is best explained with reference to the transient properties of ensembles of populations. Specifically, we submit that under experimental c