Science.gov

Sample records for zooplankton population model

  1. Lake acidification: Effects on crustacean zooplankton populations

    SciTech Connect

    Havens, K.E. ); Yan, N.D. ); Keller, W. )

    1993-08-01

    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.

  2. Interactions between predation and resources shape zooplankton population dynamics.

    PubMed

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

    2011-01-01

    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

  3. Zooplankton population dynamics in experimentally toxified pond ecosystems

    SciTech Connect

    Sierszen, M.E.; Boston, H.L.; Horn, M.J.

    1989-01-01

    To evaluate ecosystem response to and recovery from toxic contamination, we added phenolic compounds to a series of experimental ponds. Toxicants were added repeatedly in a temporally staggered sequence to evaluate the influence of seasonal factors and previous exposure history on the responses to toxicant stress. We hypothesized that seasonal changes in ecosystem structure, e.g. shifts in the relative importance of ''top-down'' and ''bottom-up'' controls on energy flow, would influence the system-level responses to the toxicant. Information from these experiments is being incorporated into models that predict ecological risk and system-level behavior under toxicant stress. Here we focus on the responses of zooplankton populations to toxicants, and factors which may affect the apparent severity of toxic effects. 9 refs., 4 figs.

  4. Roles of predation, food, and temperature in structuring the epilimnetic zooplankton populations in Lake Ontario, 1981-1986

    USGS Publications Warehouse

    Johannsson, Ora E.; O'Gorman, Robert

    1991-01-01

    We sampled phytoplankton, zooplankton, and alewives Alosa pseudoharengus and measured water temperature in Lake Ontario during 1981-1986. Through the use of general linear regression models we then sought evidence of control of the eplimnetic zooplankton community (mid-July to mid-October) by producers, consumers, and temperature. Our measures of the zooplankton community were total biomass, cladoceran biomass, and the ratio of large to small Daphnia spp. (D. galeata mendotae and D. retrocurva). Zooplankton population variables assessed were abundance, egg ratio, and productivity. Through factor analysis, factors were created from the standardized, transformed independent variables for use in the regression analyses. Regression models showed significant inverse relationships (P < 0.05) between alewives and Bosmina longirostris (abundance, production, and egg ratio), Ceriodaphnia lacustris (egg ratio), and Daphnia retrocurva (egg ratio). Bosmina longirostris and D. retrocurva egg ratios were inversely related to algae biomass (<20 I?m), thus the smaller algae might be controlled in part by the zooplankton community. Production of C. lacustris was directly related to temperature, as was the production and abundance of Tropocyclops prasinus. The annual size-frequency distributions of B. longirostris and D. retrocurva were inversely related to yearling alewife abundance and directly related to adult alewife abundance, which suggested that yearlings use a particulate-feeding mode on these zooplankton species more frequently than adults. We found no significant negative correlations among the zooplankton species, which suggested that interzooplankton predation and competition were not as important in structuring the community as were planktivory and temperature.

  5. Evaluation of abiotic stresses of temperate estuaries by using resident zooplankton: A community vs. population approach

    NASA Astrophysics Data System (ADS)

    Paul, Sourav; Wooldridge, Tris; Perissinotto, Renzo

    2016-03-01

    By using permanently resident zooplankton, we assessed the ecological level (i.e. community and or population) that provides more in-depth indication of the stress related to salinity and temperature fluctuations in temperate estuaries. In the semi-arid warm temperate South Africa, the Gamtoos estuary experiences a full salinity gradient maintained by irregular but relatively frequent freshwater pulses, whereas the Kromme estuary is euhaline throughout its extent and receives only occasional freshwater inputs when the storage reservoir six km upstream overtops. Changes in the species evenness index of Pielou and the abundances of estuarine resident zooplankton species were modelled against salinity and temperature variations of respective estuaries. In the Gamtoos estuary, response of individual populations provided more in-depth information regarding zooplankton variability. However the most abundant resident zooplankton i.e. Acartia longipatella a copepod was not the best predictor of the salinity and temperature fluctuations. Conversely, the Kromme estuary study provided insights into the potential vulnerability of the resident estuarine zooplankton community to cold. Further, the population level study exposed responses of specific species against salinity changes. We discuss the pros and cons of designing ecological indicators of abiotic stress based on specific species, targeted to specific ecological level, and needs of considering the frequency and magnitude of fresh water inflow in an estuary. A suggestion is to use specific taxonomic group(s) (e.g. Copepods) to better understand the abiotic stress factors of specific set of estuaries (e.g. freshwater rich/starved) until a 'one size fits all' indicator is found for temperate estuaries.

  6. Effects of alewife predation on zooplankton populations in Lake Michigan

    USGS Publications Warehouse

    Wells, LaRue

    1970-01-01

    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.

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

    PubMed

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

    2007-02-01

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

  8. Distribution and abundance of zooplankton populations in Crater Lake, Oregon

    USGS Publications Warehouse

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

    2007-01-01

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

  9. RESPONSE OF PREDATORY ZOOPLANKTON POPULATIONS TO THE EXPERIMENTAL ACIDIFICATION OF LITTLE ROCK LAKE, WI

    EPA Science Inventory

    To assess the effects of lake acidification on large predatory zooplankton, we monitored population levels of four limnetic taxa for 6 years in a lake with two basins, one of which was experimentally acidified (2 years at each of there levels: pH 5.6, 5.2, and 4.7). oncentrations...

  10. New view of population genetics of zooplankton: RAD-seq analysis reveals population structure of the North Atlantic planktonic copepod Centropages typicus.

    PubMed

    Blanco-Bercial, L; Bucklin, A

    2016-04-01

    Detection of population genetic structure of zooplankton at medium-to-small spatial scales in the absence of physical barriers has remained challenging and controversial. The large population sizes and high rates of gene flow characteristic of zooplankton have made resolution of geographical differentiation very difficult, especially when using few genetic markers and assuming equilibrium conditions. Next-generation sequencing now allows simultaneous sampling of hundreds to thousands of genetic markers; new analytical approaches allow studies under nonequilibrium conditions and directional migration. Samples of the North Atlantic Ocean planktonic copepod, Centropages typicus, were analysed using restriction site-associated DNA (RAD) sequencing on a PROTON platform. Although prior studies revealed no genetic differentiation of populations across the geographical range of the species, analysis of RAD tags showed significant structure across the North Atlantic Ocean. We also compared the likelihood for models of connectivity among NW Atlantic populations under various directional flow scenarios that replicate oceanographic conditions of the sampled domain. High-density marker sampling with RAD sequencing markedly outperformed other technical and analytical approaches in detection of population genetic structure and characterization of connectivity of this high geneflow zooplankton species. PMID:26857348

  11. Population dynamics of pond zooplankton, I. Diaptomus pallidus Herrick

    USGS Publications Warehouse

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

    1973-01-01

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

  12. Gelatinous zooplankton in the Belgian part of the North Sea and the adjacent Schelde estuary: Spatio-temporal distribution patterns and population dynamics

    NASA Astrophysics Data System (ADS)

    Vansteenbrugge, Lies; Van Regenmortel, Tina; De Troch, Marleen; Vincx, Magda; Hostens, Kris

    2015-03-01

    Many ocean ecosystems are thought to be heading towards a dominance of gelatinous organisms. However, gelatinous zooplankton has been largely understudied and the absence of quantitative long-term data for the studied area impedes drawing conclusions on potential increasing densities. This study gives a comprehensive overview of the spatio-temporal distribution patterns of gelatinous zooplankton in terms of diversity and density in the Belgian part of the North Sea and the adjacent Schelde estuary, based on monthly and seasonal samples between March 2011 and February 2012. Three Scyphozoa, three Ctenophora and 27 Hydrozoa taxa were identified, including three non-indigenous species: Mnemiopsis leidyi, Nemopsis bachei and Lovenella assimilis. In general, one gelatinous zooplankton assemblage was found across locations and seasons. Average gelatinous zooplankton densities reached up to 18 ind·m-3 near the coast, gradually declining towards the open sea. In the brackish Schelde estuary, average densities remained below 3 ind·m-3. Highest gelatinous zooplankton densities were recorded in summer and autumn. Overall, hydromedusae were the most important group both in terms of diversity and density. The ctenophore Pleurobrachia pileus and the hydromedusa Clytia sp. were present in every season and at every location. Gelatinous zooplankton densities never outnumbered the non-gelatinous zooplankton densities recorded from the WP3 samples. The spatial and temporal distribution patterns seemed to be mainly driven by temperature (season) and salinity (location). Other environmental parameters including (larger) non-gelatinous zooplankton densities (as an important food source) were not retained in the most parsimonious DistLM model.In terms of population dynamics, Beroe sp. seemed to follow the three reproductive cycles of its prey P. pileus and the presence of M. leidyi, which were abundant in a broad size spectrum in summer and autumn. In general, gelatinous zooplankton diversity was higher, but densities were in the same order of magnitude compared to adjacent areas in the North Sea. This study provides a baseline against which a potential increase in gelatinous zooplankton in the Belgian part of the North Sea and the Schelde estuary can be measured.

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

    SciTech Connect

    Evans, M.S.; McNaught, D.

    1988-01-01

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

  14. Wetland defense: naturally occurring pesticide resistance in zooplankton populations protects the stability of aquatic communities.

    PubMed

    Bendis, Randall J; Relyea, Rick A

    2016-06-01

    Anthropogenic stressors are ubiquitous and have been implicated in worldwide declines of terrestrial and aquatic species. Pesticides are one such stressor that can have profound effects on aquatic communities by directly affecting sensitive species and indirectly affecting other species via trophic cascades, which can alter ecosystem function. However, there is growing evidence that non-target species can evolve increased resistance. When such species are important drivers of the food web, then evolved resistance should help buffer communities from the effects of pesticides. To examine this possibility, we cultured four populations of the common zooplankton Daphnia pulex that we previously demonstrated were either sensitive or resistant to a common insecticide (i.e., chlorpyrifos) due to their proximity to agriculture. Using outdoor mesocosms that contained identical aquatic communities of phytoplankton, periphyton, and leopard frog tadpoles (Lithobates pipiens), we manipulated four D. pulex populations and four insecticide concentrations. As we monitored the communities for nearly 3 months, we found that the insecticide caused direct mortality of D. pulex in communities containing sensitive populations, and this led to a bloom of phytoplankton. In contrast, the insecticide caused much less direct mortality in communities containing resistant D. pulex populations, and the trophic cascade was prevented under low to moderate insecticide concentrations. Across all insecticide treatments, survivorship of leopard frogs was approximately 72 % in communities with resistant D. pulex but only 35 % in communities with sensitive D. pulex. To our knowledge, this is one of the first studies to use naturally occurring population variation in insecticide resistance to show that the evolution of pesticide resistance in zooplankton can mitigate the effects of insecticide-induced trophic cascades, and that this outcome can have far-reaching community effects. PMID:26875187

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

    NASA Astrophysics Data System (ADS)

    Stempniewicz, Lech; Błachowiak-Samołyk, Katarzyna; Węsławski, Jan M.

    2007-11-01

    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.

  16. Role of Zooplankton Diversity in Vibrio cholerae Population Dynamics and in the Incidence of Cholera in the Bangladesh Sundarbans ▿

    PubMed Central

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

    2011-01-01

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

  17. Population structure changes in zooplankton following PAH exposure in aquatic mesocosms

    SciTech Connect

    McCann, J.H.; Gensemer, R.W.; Solomon, K.R.

    1994-12-31

    Studies on polycyclic aromatic hydrocarbons (PAHs) have generally concentrated on single compounds. However, PAHs are usually found as mixtures in the aquatic environment and may pose significant risk to the ecosystem. A study was conducted to determine the effect of creosote (a mixture of PAHs) on pelagic invertebrates, including cladocerans, copepods, amphipods, and rotifers. Artificial aquatic mesocosms consisting of a simple community structure, including fish, algae, macrophytes and invertebrates, were utilized. Four doses of creosote and a control were used. Dosing was accomplished by adding contaminated sediment to the mesocosm, ranging from 100 cm{sup 2} to 3 m{sup 2} in area. As well, 1 to 8 creosote coated log pilings were added to several mesocosms, simulating aquatic exposure to preserved log pilings. The zooplankton at the various dose levels were enumerated. The changes in population structure will be described.

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

    SciTech Connect

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

    1993-01-01

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

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

    SciTech Connect

    Shuman, J.R.

    1988-01-01

    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.

  20. Water level and temperature and zooplankton population abundances in Lake Surinumu, Papua New Guinea

    NASA Astrophysics Data System (ADS)

    Vlaardingerbroek, Barend

    1989-09-01

    Lake Surinumu, an oligotrophic hydroelectric impoundment on the Laloki River in Central Province, Papua New Guinea, was sampled throughout 1982 for its zooplankton community composition, water level and surface temperature. The zooplankton community was observed to be normally dominated by Eodiaptomus lumholtzi, Ceriodaphnia cornuta and the Diaphanosoma species D. sarsi and D. excisum, though the rotifer T. equatorialis became dominant toward the end of the sampling period. Nutrient levels, especially with regard to ionic nitrogen, were observed to decrease following the monsoonal influx. Close correlations were found between water level and surface temperature, and between water level and the relative abundances of E. lumholtzi, diaphanosomids and T. equatorialis. The zooplankton community was observed to undergo the most significant changes during periods of monsoonal influx and lowest water level/highest water temperature. In the absence of significant interspecific abundance correlations, it is suggested that climatic factors are primarily responsible for the dynamics of the zooplankton community composition.

  1. Environmental influence on coastal phytoplankton and zooplankton diversity: a multivariate statistical model analysis.

    PubMed

    Chou, Wei-Rung; Fang, Lee-Shing; Wang, Wei-Hsien; Tew, Kwee Siong

    2012-09-01

    In a marine ecosystem, the diversity of phytoplankton can influence the diversity of zooplankton, or vice versa, and both can be affected by the environmental factors. In this study, we used principal component analysis (PCA) to identify the major sources of influence on the coastal water near an industrial park, following by construction of structural equation model (SEM) to determine the direct and indirect effect of the factors on phytoplankton and zooplankton diversity. PCA results indicated that the coastal area was mainly affected by riverine discharge (represented by high PC factor loadings of transparency and turbidity) and seasonal change (represented by temperature). SEM further suggested that both riverine discharge and seasonal influences can directly affect phytoplankton diversity, but indirectly affected zooplankton diversity via changes in phytoplankton. Using PCA to determine the sources of influence followed by construction of SEM allowed us to understand the relative importance of the environmental factors, direct or indirect, on phytoplankton and zooplankton diversity. When environmental changes occur, a new SEM could be constructed using the same category of physical and biological data and then compared to the current model to verify whether the environmental changes were the cause of alterations in planktonic communities in the area. PMID:21956341

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

  3. A case study of an enhanced eutrophication model with stoichiometric zooplankton growth sub-model calibrated by Bayesian method.

    PubMed

    Yang, Likun; Peng, Sen; Sun, Jingmei; Zhao, Xinhua; Li, Xia

    2016-05-01

    Urban lakes in China have suffered from severe eutrophication over the past several years, particularly those with relatively small areas and closed watersheds. Many efforts have been made to improve the understanding of eutrophication physiology with advanced mathematical models. However, several eutrophication models ignore zooplankton behavior and treat zooplankton as particles, which lead to the systematic errors. In this study, an eutrophication model was enhanced with a stoichiometric zooplankton growth sub-model that simulated the zooplankton predation process and the interplay among nitrogen, phosphorus, and oxygen cycles. A case study in which the Bayesian method was used to calibrate the enhanced eutrophication model parameters and to calculate the model simulation results was carried out in an urban lake in Tianjin, China. Finally, a water quality assessment was also conducted for eutrophication management. Our result suggests that (1) integration of the Bayesian method and the enhanced eutrophication model with a zooplankton feeding behavior sub-model can effectively depict the change in water quality and (2) the nutrients resulting from rainwater runoff laid the foundation for phytoplankton bloom. PMID:26780061

  4. Biomass, growth, and development of populations of herbivorous zooplankton in the southeastern Bering Sea during spring

    SciTech Connect

    Vidal, J.; Smith, S.L.

    1985-09-01

    Two distinct communities of herbivorous zooplankton, separated by an oceanographic front, inhabit the continental shelf and slope of the southeastern Bering Sea during spring. The community over the outer shelf and slope is dominated by populations of large-sized oceanic copepods (mainly Neocalanus ssp.) that develop early in spring and attain maximum biomass and growth rates by mid- to late spring. Total biomass and growth rates of herbivores follow the spring outburst of phytoplankton; during April and May biomass increases from less than or equal to1 to approx.14 g C m/sup -2/ on the slope and to approx.10 g C m/sup -2/ on the outer shelf, and maximum growth rates >500 and approx.300 mg C m/sup -2/ day/sup -1/ occure on the slope and outer shelf, respectively in May. The dominant species, N. plumchrus, grows from copepodid I and V between late March and early May, and after attaining maximum body weight in late May and early June it begins its downward migration. The inshore community on the middle shelf is dominated by the euphausiid Thysanoessa raschi in April and May and by the copepod Calanus marshallae in late May and early June. Total biomass (less than or equal to g C m/sup -2/) and growth rates (less than or equal to50 mg C m/sup -2/) of the inshore community are substantially lower than those of the offshore community and show a delayed response to the spring bloom of phytoplankton; both biomass and growth rates increase about one month after the bloom. Small herbivorous copepods contributed little to the total biomass and growth rates of either community and the cumulative community growth rates during April and May decreases from 18.3 g C m/sup -2/ on the slope to 2.5 g C m/sup -2/ on the middle shelf. 79 refs., 15 figs., 7 tabs.

  5. Biomixing due to diel vertical migrations of zooplankton: Comparison of computational fluid dynamics model with observations

    NASA Astrophysics Data System (ADS)

    Dean, Cayla; Soloviev, Alexander; Hirons, Amy; Frank, Tamara; Wood, Jon

    2016-02-01

    Recent studies (Dewar et al., 2006; Wilhelmus and Dabiri, 2014) suggest that diel vertical migrations (DVM) of zooplankton (or other migrating organisms) may have an impact on ocean mixing, though details are not completely clear. Zooplankton that undergo DVM can have an impact on oil transport through the water column, and oil and dispersants can have a negative or even lethal effect on the organisms. Kunze et al. (2006) reported an increase of dissipation rate of turbulent kinetic energy, ε, by four to five orders of magnitude during DVM of zooplankton over background turbulence in Saanich Inlet, British Columbia, Canada. However, the effect was not observed in the same area by Rousseau et al. (2010) and was later reassessed by Kunze (2011). In our work, an 11-month data set obtained in the Straits of Florida with a bottom-mounted acoustic Doppler current profiler revealed strong sound scattering layers undergoing DVM. We used a 3-D non-hydrostatic computational fluid dynamics model with Lagrangian particle injections (a proxy for migrating organisms) via a discrete phase model to simulate the effect of turbulence generation by DVM. We tested a range of organism concentrations from 1000 to 10,000 organisms/m3 based on measurements by Greenlaw (1979) and Mackie and Mills (1983) in Saanich Inlet. At a concentration close to the upper limit, the simulation showed an increase in ε by two to three orders of magnitude during DVM over background turbulence, 10-9 W kg-1. At a concentration of 1000 organisms/m3, almost no turbulence above the background level was produced in the model. These results suggest that the Kunze et al. (2006) observations could have been performed at a larger concentration of migrating zooplankton than those reported by Rousseau et al. (2010). No exact zooplankton concentrations data were provided in either work. The difference between observations and the model can, in part, be explained by the fact that Kunze et al. (2006) measured instantaneous profiles of ε, while the model results on ε were averaged horizontally over the 50 m by 50 m domain. In the Straits of Florida, we observed a small decrease in northward current velocity profiles during migration times after averaging over 11 months of observations. The computational fluid dynamics model reproduced this decrease of current velocity due to turbulence generated by DVM in the Straits of Florida model case. The deviations in the velocity profiles can be explained by the increase in turbulent mixing during vertical migration periods. Comparison of observational data to the model results was complicated by physical factors such as tides, Florida Current meandering, etc., which may have a stronger effect on current velocity profiles than DVM.

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

    SciTech Connect

    Not Available

    1985-07-01

    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.

  7. Extended probit mortality model for zooplankton against transient change of PCO(2).

    PubMed

    Sato, Toru; Watanabe, Yuji; Toyota, Koji; Ishizaka, Joji

    2005-09-01

    The direct injection of CO(2) in the deep ocean is a promising way to mitigate global warming. One of the uncertainties in this method, however, is its impact on marine organisms in the near field. Since the concentration of CO(2), which organisms experience in the ocean, changes with time, it is required to develop a biological impact model for the organisms against the unsteady change of CO(2) concentration. In general, the LC(50) concept is widely applied for testing a toxic agent for the acute mortality. Here, we regard the probit-transformed mortality as a linear function not only of the concentration of CO(2) but also of exposure time. A simple mathematical transform of the function gives a damage-accumulation mortality model for zooplankton. In this article, this model was validated by the mortality test of Metamphiascopsis hirsutus against the transient change of CO(2) concentration. PMID:15913663

  8. Metal and proton toxicity to lake zooplankton: a chemical speciation based modelling approach.

    PubMed

    Stockdale, Anthony; Tipping, Edward; Lofts, Stephen; Fott, Jan; Garmo, Oyvind A; Hruska, Jakub; Keller, Bill; Löfgren, Stefan; Maberly, Stephen C; Majer, Vladimir; Nierzwicki-Bauer, Sandra A; Persson, Gunnar; Schartau, Ann-Kristin; Thackeray, Stephen J; Valois, Amanda; Vrba, Jaroslav; Walseng, Bjørn; Yan, Norman

    2014-03-01

    The WHAM-FTOX model quantifies the combined toxic effects of protons and metal cations towards aquatic organisms through the toxicity function (FTOX), a linear combination of the products of organism-bound cation and a toxic potency coefficient for each cation. We describe the application of the model to predict an observable ecological field variable, species richness of pelagic lake crustacean zooplankton, studied with respect to either acidification or the impacts of metals from smelters. The fitted results give toxic potencies increasing in the order H(+) < Al < Cu < Zn < Ni. In general, observed species richness is lower than predicted, but in some instances agreement is close, and is rarely higher than predictions. The model predicts recovery in agreement with observations for three regions, namely Sudbury (Canada), Bohemian Forest (Czech Republic) and a subset of lakes across Norway, but fails to predict observed recovery from acidification in Adirondack lakes (USA). PMID:24370669

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

    PubMed

    Bendis, Randall J; Relyea, Rick A

    2014-12-01

    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. PMID:25220688

  10. The zooplankton of Marguerite Bay, Western Antarctic Peninsula—Part I: Abundance, distribution, and population response to variability in environmental conditions

    NASA Astrophysics Data System (ADS)

    Marrari, Marina; Daly, Kendra L.; Timonin, Alexander; Semenova, Tatjana

    2011-07-01

    The zooplankton community of Marguerite Bay was studied during austral fall of 2001 and 2002 using net and concurrent environmental data. Interannual differences were observed in zooplankton species composition, developmental stages, and abundances, which were linked to unusually high chlorophyll concentrations in the Bellingshausen Sea and Marguerite Bay during spring-summer 2000/2001. Copepod abundance was significantly higher in 2001 than in 2002 (46.3 and 28.3 ind m -3 in 2001 and 2002, respectively). During 2001, the copepod community was dominated by two species. Calanoides acutus, a herbivore, and Metridia gerlachei, an omnivore, accounted for 46% and 45% of the community, respectively. During 2002, however, several species were relatively abundant, including M. gerlachei, Ctenocalanus spp., C. acutus, Oithona spp., and Paraeuchaeta spp. Euphausiids also showed a rapid population response to high chlorophyll levels in 2001. Even though average total euphausiid (juvenile/adult) abundances were similar during both years (0.20 and 0.15 ind m -3 for 2001 and 2002, respectively), species composition showed marked interannual differences due to varying life history strategies among species. Thysanoessa macrura, which has a relatively rapid development from larval to juvenile stages between spring and fall of the same year, was the most abundant euphausiid in 2001. In contrast, Euphausia crystallorophias and Euphausia superba juvenile/adult populations increased in 2002, owing to a slower development in which larval stages overwinter and recruit to juveniles during the following spring/summer. Other zooplankton groups those were abundant in Marguerite Bay, but showed little variability between years, included ostracods, pteropods, chaetognaths, medusae, amphipods, and mysids. Summer phytoplankton concentrations strongly influenced copepods and euphausiids; however, there were no clear associations between zooplankton distributions and fall environmental conditions (i.e., pigment concentrations and surface salinity) or bottom depth. It is notable that ostracods and pteropods had the highest abundances of non-copepod zooplankton.

  11. 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)

    Vandromme, Pieter; Sourisseau, Marc; Huret, Martin

    2013-04-01

    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.

  12. Synoptic-scale upwelling indices and predictions of phyto- and zooplankton populations

    NASA Astrophysics Data System (ADS)

    García-Reyes, Marisol; Largier, John L.; Sydeman, William J.

    2014-01-01

    Seasonal upwelling is responsible for the biologically rich and productive ecosystems of coastal eastern boundary currents. In most studies of physical - biological interactions in these systems, upwelling statistics are computed on monthly, seasonal, and annual time scales, whereas upwelling naturally occurs at high frequencies (days to weeks). This simplification of the upwelling process may misrepresent relationships between upwelling and biological populations. Based on 31 years (1982-2012) of hourly-measured winds and sea surface temperature at buoys off the central-northern California coast, we characterized upwelling and relaxation events at synoptic time scales, and used event-scale statistics to relate to local lower trophic level populations. We defined three metrics to quantify synoptic-scale upwelling: (i) Intensity, a measure of cumulative wind stress forcing during each upwelling event, (ii) SSTevent, a measure of the oceanic response to wind forcing, and (iii) Nutrient Upwelling Index (NUI), a measure of the nitrate availability at the surface during upwelling events. We compared cumulative values of Intensity and NUI, and average values of SSTevent during the peak of the upwelling season (April-June in central-northern California) to proxies of phytoplankton biomass (chlorophyll-a concentrations) and krill abundance to assess the abilities of high frequency upwelling indices to predict biology. Wind forcing alone (Intensity) did not explain population variability, but SSTevent and NUI showed excellent relationships to chlorophyll concentrations (44% and 54% of variance explained, respectively) and krill abundance (68% of variance explained). All relationships appeared to be dome-shaped, supporting the hypothesis that moderate upwelling and ocean temperature are optimal for these populations. SSTevent and NUI performed better than the traditional Bakun upwelling index in predicting populations. We conclude that investigating upwelling characteristics on event scales can improve understanding of lower trophic level dynamics in eastern boundary current systems.

  13. Zooplankton and forage fish species off Peru: Large-scale bottom-up forcing and local-scale depletion

    NASA Astrophysics Data System (ADS)

    Ayón, Patricia; Swartzman, Gordon; Bertrand, Arnaud; Gutiérrez, Mariano; Bertrand, Sophie

    2008-10-01

    The Humboldt Current System, like all upwelling systems, has dramatic quantities of plankton-feeding fish, which suggested that their population dynamics may ‘drive’ or ‘control’ ecosystem dynamics. With this in mind we analysed the relationship between forage fish populations and their main prey, zooplankton populations. Our study combined a zooplankton sampling program (1961-2005) with simultaneous acoustic observations on fish from 40 pelagic surveys (1983-2005) conducted by the Peruvian Marine Research Institute (IMARPE) and landing statistics for anchoveta ( Engraulis ringens) and sardine ( Sardinops sagax) along the Peruvian coast from 1961 to 2005. The multi-year trend of anchoveta population abundance varied consistently with zooplankton biovolume trend, suggesting bottom-up control on anchovy at the population scale (since oceanographic conditions and phytoplankton production support the changes in zooplankton abundance). For a finer-scale analysis (km) we statistically modelled zooplankton biovolume as a function of geographical (latitude and distance from the 200-m isobath), environmental (sea surface temperature), temporal (year, month and time-of-day) and biological (acoustic anchovy and sardine biomass within 5 km of each zooplankton sample) covariates over all survey using both classification and regression trees (CART) and generalized additive models (GAM). CART showed local anchoveta density to have the strongest effect on zooplankton biovolume, with significantly reduced levels of biovolume for higher neighbourhood anchoveta biomass. Additionally, zooplankton biovolume was higher offshore than on the shelf. GAM results corroborated the CART findings, also showing a clear diel effect on zooplankton biovolume, probably due to diel migration or daytime net avoidance. Apparently, the observed multi-year population scale bottom-up control is not inconsistent with local depletion of zooplankton when anchoveta are locally abundant, since the latter effect was observed over a wide range of overall anchoveta abundance.

  14. Acoustic classification of zooplankton

    NASA Astrophysics Data System (ADS)

    Martin Traykovski, Linda V.

    1998-11-01

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

  15. Zooplankton intermittency and turbulence

    NASA Astrophysics Data System (ADS)

    Schmitt, François G.

    2010-05-01

    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.

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

    USGS Publications Warehouse

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

    2006-01-01

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

  17. Temperature effects on stocks and stability of a phytoplankton-zooplankton model and the dependence on light and nutrients

    USGS Publications Warehouse

    Norberg, J.; DeAngelis, D.L.

    1997-01-01

    A model of a closed phytoplankton—zooplankton ecosystem was analyzed for effects of temperature on stocks and stability and the dependence of these effects on light and total nutrient concentration of the system. An analysis of the steady state equations showed that the effect of temperature on zooplankton and POM biomass was levelled when primary production is nutrient limited. Temperature increase had a generally negative effect on all biomasses at high nutrient levels due to increased maintenance costs. Nutrient limitation of net primary production is the main factor governing the effect of stocks and flows as well as the stability of the system. All components of the system, except for phytoplankton biomass, are proportional to net production and thus to the net effect of light on photosynthesis. However, temperature determines the slope of that relationship. The resilience of the system was measured by calculating the eigenvalues of the steady state. Under oligotrophic conditions, the system can be stable, but an increase in temperature can cause instability or a decrease in resilience. This conclusion is discussed in the face of recent models that take spatial heterogeneity into account and display far more stable behavior, in better agreement to empirical data. Using simulations, we found that the amplitude of fluctuations of the herbivore stock increases with temperature while the mean biomass and minimum values decrease in comparison with steady state predictions

  18. Oxygenation of anoxic sediments triggers hatching of zooplankton eggs.

    PubMed

    Broman, Elias; Brüsin, Martin; Dopson, Mark; Hylander, Samuel

    2015-10-22

    Many coastal marine systems have extensive areas with anoxic sediments and it is not well known how these conditions affect the benthic-pelagic coupling. Zooplankton lay their eggs in the pelagic zone, and some sink and lie dormant in the sediment, before hatched zooplankton return to the water column. In this study, we investigated how oxygenation of long-term anoxic sediments affects the hatching frequency of dormant zooplankton eggs. Anoxic sediments from the brackish Baltic Sea were sampled and incubated for 26 days with constant aeration whereby, the sediment surface and the overlying water were turned oxic. Newly hatched rotifers and copepod nauplii (juveniles) were observed after 5 and 8 days, respectively. Approximately 1.5 × 10(5) nauplii m(-2) emerged from sediment turned oxic compared with 0.02 × 10(5) m(-2) from controls maintained anoxic. This study demonstrated that re-oxygenation of anoxic sediments activated a large pool of buried zooplankton eggs, strengthening the benthic-pelagic coupling of the system. Modelling of the studied anoxic zone suggested that a substantial part of the pelagic copepod population can derive from hatching of dormant eggs. We suggest that this process should be included in future studies to understand population dynamics and carbon flows in marine pelagic systems. PMID:26468249

  19. Application of an automatic approach to calibrate the NEMURO nutrient-phytoplankton-zooplankton food web model in the Oyashio region

    NASA Astrophysics Data System (ADS)

    Ito, Shin-ichi; Yoshie, Naoki; Okunishi, Takeshi; Ono, Tsuneo; Okazaki, Yuji; Kuwata, Akira; Hashioka, Taketo; Rose, Kenneth A.; Megrey, Bernard A.; Kishi, Michio J.; Nakamachi, Miwa; Shimizu, Yugo; Kakehi, Shigeho; Saito, Hiroaki; Takahashi, Kazutaka; Tadokoro, Kazuaki; Kusaka, Akira; Kasai, Hiromi

    2010-10-01

    The Oyashio region in the western North Pacific supports high biological productivity and has been well monitored. We applied the NEMURO (North Pacific Ecosystem Model for Understanding Regional Oceanography) model to simulate the nutrients, phytoplankton, and zooplankton dynamics. Determination of parameters values is very important, yet ad hoc calibration methods are often used. We used the automatic calibration software PEST (model-independent Parameter ESTimation), which has been used previously with NEMURO but in a system without ontogenetic vertical migration of the large zooplankton functional group. Determining the performance of PEST with vertical migration, and obtaining a set of realistic parameter values for the Oyashio, will likely be useful in future applications of NEMURO. Five identical twin simulation experiments were performed with the one-box version of NEMURO. The experiments differed in whether monthly snapshot or averaged state variables were used, in whether state variables were model functional groups or were aggregated (total phytoplankton, small plus large zooplankton), and in whether vertical migration of large zooplankton was included or not. We then applied NEMURO to monthly climatological field data covering 1 year for the Oyashio, and compared model fits and parameter values between PEST-determined estimates and values used in previous applications to the Oyashio region that relied on ad hoc calibration. We substituted the PEST and ad hoc calibrated parameter values into a 3-D version of NEMURO for the western North Pacific, and compared the two sets of spatial maps of chlorophyll- a with satellite-derived data. The identical twin experiments demonstrated that PEST could recover the known model parameter values when vertical migration was included, and that over-fitting can occur as a result of slight differences in the values of the state variables. PEST recovered known parameter values when using monthly snapshots of aggregated state variables, but estimated a different set of parameters with monthly averaged values. Both sets of parameters resulted in good fits of the model to the simulated data. Disaggregating the variables provided to PEST into functional groups did not solve the over-fitting problem, and including vertical migration seemed to amplify the problem. When we used the climatological field data, simulated values with PEST-estimated parameters were closer to these field data than with the previously determined ad hoc set of parameter values. When these same PEST and ad hoc sets of parameter values were substituted into 3-D-NEMURO (without vertical migration), the PEST-estimated parameter values generated spatial maps that were similar to the satellite data for the Kuroshio Extension during January and March and for the subarctic ocean from May to November. With non-linear problems, such as vertical migration, PEST should be used with caution because parameter estimates can be sensitive to how the data are prepared and to the values used for the searching parameters of PEST. We recommend the usage of PEST, or other parameter optimization methods, to generate first-order parameter estimates for simulating specific systems and for insertion into 2-D and 3-D models. The parameter estimates that are generated are useful, and the inconsistencies between simulated values and the available field data provide valuable information on model behavior and the dynamics of the ecosystem.

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

    USGS Publications Warehouse

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

    2013-01-01

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

  1. Statistical Mechanics of Zooplankton.

    PubMed

    Hinow, Peter; Nihongi, Ai; Strickler, J Rudi

    2015-01-01

    Statistical mechanics provides the link between microscopic properties of many-particle systems and macroscopic properties such as pressure and temperature. Observations of similar "microscopic" quantities exist for the motion of zooplankton, as well as many species of other social animals. Herein, we propose to take average squared velocities as the definition of the "ecological temperature" of a population under different conditions on nutrients, light, oxygen and others. We test the usefulness of this definition on observations of the crustacean zooplankton Daphnia pulicaria. In one set of experiments, D. pulicaria is infested with the pathogen Vibrio cholerae, the causative agent of cholera. We find that infested D. pulicaria under light exposure have a significantly greater ecological temperature, which puts them at a greater risk of detection by visual predators. In a second set of experiments, we observe D. pulicaria in cold and warm water, and in darkness and under light exposure. Overall, our ecological temperature is a good discriminator of the crustacean's swimming behavior. PMID:26270537

  2. Statistical Mechanics of Zooplankton

    PubMed Central

    Hinow, Peter; Nihongi, Ai; Strickler, J. Rudi

    2015-01-01

    Statistical mechanics provides the link between microscopic properties of many-particle systems and macroscopic properties such as pressure and temperature. Observations of similar “microscopic” quantities exist for the motion of zooplankton, as well as many species of other social animals. Herein, we propose to take average squared velocities as the definition of the “ecological temperature” of a population under different conditions on nutrients, light, oxygen and others. We test the usefulness of this definition on observations of the crustacean zooplankton Daphnia pulicaria. In one set of experiments, D. pulicaria is infested with the pathogen Vibrio cholerae, the causative agent of cholera. We find that infested D. pulicaria under light exposure have a significantly greater ecological temperature, which puts them at a greater risk of detection by visual predators. In a second set of experiments, we observe D. pulicaria in cold and warm water, and in darkness and under light exposure. Overall, our ecological temperature is a good discriminator of the crustacean’s swimming behavior. PMID:26270537

  3. Zooplankton research off Peru: A review

    NASA Astrophysics Data System (ADS)

    Ayón, Patricia; Criales-Hernandez, Maria I.; Schwamborn, Ralf; Hirche, Hans-Jürgen

    2008-10-01

    A review of zooplankton studies conducted in Peruvian marine waters is given. After a short history of the development of zooplankton research off Peru, we review zooplankton methodology, taxonomy, biodiversity, spatial distribution, seasonal and interannual variability, trophodynamics, secondary production, and modelling. We review studies on several micro-, meso-, macro-, and meroplankton groups, and give a species list from both published and unpublished reports. Three regional zooplankton groups have been identified: (1) a continental shelf group dominated by Acartia tonsa and Centropages brachiatus; (2) a continental slope group characterized by siphonophores, bivalves, foraminifera and radiolaria; (3) and a species-rich oceanic group. The highest zooplankton abundances and biomasses were often found between 4-6°S and 14-16°S, where continental shelves are narrow. Species composition changes with distance from the shore. Species composition and biomass also vary strongly on short time scales due to advection, peaks of larval production, trophic interactions, and community succession. The relation of zooplankton to climatic variability (ENSO and multi-decadal) and fish stocks is discussed in the context of ecological regime shifts. An intermediate upwelling hypothesis is proposed, based on the negative effects of low upwelling intensity in summer or extremely strong and enduring winter upwelling on zooplankton abundance off Peru. According to this hypothesis, intermediate upwelling creates an optimal environmental window for zooplankton communities. Finally, we highlight important knowledge gaps that warrant attention in future.

  4. High evolutionary potential of marine zooplankton

    PubMed Central

    Peijnenburg, Katja T C A; Goetze, Erica

    2013-01-01

    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

  5. Latitudinal comparisons of equatorial Pacific zooplankton

    NASA Astrophysics Data System (ADS)

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

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

  6. Modeling the direct and indirect effects of copper on phytoplankton-zooplankton interactions.

    PubMed

    Prosnier, Loïc; Loreau, Michel; Hulot, Florence D

    2015-05-01

    Predicting the effects of pollution at the community level is difficult because of the complex impacts of ecosystem dynamics and properties. To predict the effects of copper on a plant-herbivore interaction in a freshwater ecosystem, we built a model that focuses on the interaction between an alga, Scenedesmus sp., and a herbivore, Daphnia sp. The model assumes logistic growth for Scenedesmus and a type II functional response for Daphnia. Internal copper concentrations in Scenedesmus and Daphnia are calculated using a biodynamic model. We include two types of direct effects of copper on Scenedesmus and Daphnia that results from hormesis: a deficiency effect at low concentration and a toxic effect at high concentration. We perform a numerical analysis to predict the combined effects of copper and nutrient enrichment on the Scenedesmus-Daphnia interaction. Results show three types of outcomes depending on copper concentration. First, low (4 μg L(-1)) and high (50 μg L(-1)) copper concentrations cause deficiency and toxicity, respectively, leading to the extinction of all populations; for less extreme concentrations (between 4 and 5 μg L(-1) and between 16.5 and 50 μg L(-1)), only the consumer population becomes extinct. The two populations survive with intermediate concentrations. Second, when population dynamics present oscillations, copper has a stabilizing effect and reduces or suppresses oscillations. Third, copper, on account of its stabilizing effect, opposes the destabilizing effect of nutrient enrichment. Our model shows that (1) Daphnia is affected by copper at lower concentrations when community interactions are taken into account than when analyzed alone, and (2) counterintuitive effects may arise from the interaction between copper pollution and nutrient enrichment. Our model also suggests that single-value parameters such as NOEC and LOEC, which do not take community interactions into account to characterize pollutants effects, are unable to determine pollutant effects in complex ecosystems. More generally, our model underscores the importance of ecosystem-scale studies to predict the effects of pollutants. PMID:25781394

  7. Modeling Honey Bee Populations

    PubMed Central

    Torres, David J.; Ricoy, Ulises M.; Roybal, Shanae

    2015-01-01

    Eusocial honey bee populations (Apis mellifera) employ an age stratification organization of egg, larvae, pupae, hive bees and foraging bees. Understanding the recent decline in honey bee colonies hinges on understanding the factors that impact each of these different age castes. We first perform an analysis of steady state bee populations given mortality rates within each bee caste and find that the honey bee colony is highly susceptible to hive and pupae mortality rates. Subsequently, we study transient bee population dynamics by building upon the modeling foundation established by Schmickl and Crailsheim and Khoury et al. Our transient model based on differential equations accounts for the effects of pheromones in slowing the maturation of hive bees to foraging bees, the increased mortality of larvae in the absence of sufficient hive bees, and the effects of food scarcity. We also conduct sensitivity studies and show the effects of parameter variations on the colony population. PMID:26148010

  8. Modeling Honey Bee Populations.

    PubMed

    Torres, David J; Ricoy, Ulises M; Roybal, Shanae

    2015-01-01

    Eusocial honey bee populations (Apis mellifera) employ an age stratification organization of egg, larvae, pupae, hive bees and foraging bees. Understanding the recent decline in honey bee colonies hinges on understanding the factors that impact each of these different age castes. We first perform an analysis of steady state bee populations given mortality rates within each bee caste and find that the honey bee colony is highly susceptible to hive and pupae mortality rates. Subsequently, we study transient bee population dynamics by building upon the modeling foundation established by Schmickl and Crailsheim and Khoury et al. Our transient model based on differential equations accounts for the effects of pheromones in slowing the maturation of hive bees to foraging bees, the increased mortality of larvae in the absence of sufficient hive bees, and the effects of food scarcity. We also conduct sensitivity studies and show the effects of parameter variations on the colony population. PMID:26148010

  9. Zooplankton in the Arctic outflow

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  11. Microplastic ingestion by zooplankton.

    PubMed

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

    2013-06-18

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

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

    SciTech Connect

    Adams, E.E.; Caulfield, J.A.; Herzog, H.J.; Auerbach, D.I.

    1998-07-01

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

  13. Modeling Exponential Population Growth

    ERIC Educational Resources Information Center

    McCormick, Bonnie

    2009-01-01

    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

  14. Modeling Exponential Population Growth

    ERIC Educational Resources Information Center

    McCormick, Bonnie

    2009-01-01

    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…

  15. The organization of zooplankton epibiont communities.

    PubMed

    Threlkeld, S T; Chiavelli, D A; Willey, R L

    1993-09-01

    Recent findings suggest that a diverse set of interactions exists between crustacean zooplankton and the algae, protozoans and metazoans that live attached to them. The frequent molting of the crustacean exoskeleton keeps these epibiont populations in a state of constant renewal and makes this epibiont community an ideal experimental system for examining the organization of communities whose populations are distributed among ephemeral habitat patches. PMID:21236181

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

    PubMed Central

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

    2010-01-01

    We try to answer the question of to what extent details in nutrient uptake and phytoplankton physiology matter for population and community dynamics. To this end, we study how two nutrients interact in limiting phytoplankton growth. A popular formulation uses a product-rule for nutrient uptake, which we compare with that on the basis of synthesizing units. We first fit different nutrient uptake models to a dataset and conclude that the quantitative differences between the models are small. Then we study the sensitivity of phytoplankton growth and zooplankton–phytoplankton interactions (ZPi) models to uptake formulations. Two population models are compared; they are based on different assumptions on the relation between nutrient uptake and phytoplankton growth. We find that the population and community models are sensitive to uptake formulations. According to the uptake formulation used in the ZPi models, qualitative differences can be observed. Indeed, although two models based on functions with similar shapes have close equilibria, these can differ in stability properties. Since stability involves the derivatives of formulas, even if two formulas provide close values, large numerical differences in the stability criterion may occur after derivation. We conclude that mechanistic details can be of importance for community modelling. PMID:20921048

  17. The ICES Working Group on Zooplankton Ecology: Accomplishments of the first 25 years

    NASA Astrophysics Data System (ADS)

    Wiebe, Peter H.; Harris, Roger; Gislason, Astthor; Margonski, Piotr; Skjoldal, Hein Rune; Benfield, Mark; Hay, Steve; O'Brien, Todd; Valdés, Luis

    2016-02-01

    The ICES Study Group on Zooplankton Ecology was created in 1991 to address issues of current and future concern within the field of zooplankton ecology. Within three years it became the ICES Working Group on Zooplankton Ecology (ICES WGZE) and this unique group in the world's oceanographic community has now been active for 25 years. This article reviews and synthesizes the products, and major accomplishments of the group. Achievements of the group, including the Zooplankton Methodology Manual, the Zooplankton Status Reports, and the International Zooplankton Symposia, have had an important impact on the wider field. Among the future issues that remain to be addressed by the group are the assessment of exploratory fisheries on zooplankton and micronekton species; further development of the zooplankton time-series; compilation and integration of allometric relationships for zooplankton species, and evaluation of new methodologies for the study of zooplankton distribution, abundance, physiology, and genetics. Marine science is an increasingly global undertaking and groups such as the ICES WGZE will continue to be essential to the advancement of understanding of zooplankton community structure and population dynamics in the world's oceans.

  18. Population modelling in drug development.

    PubMed

    Sheiner, L; Wakefield, J

    1999-09-01

    In this paper we discuss the vital role that population (hierarchical) modelling can play within the drug development process. Specifically, population pharmacokinetic/pharmacodynamic models can provide reliable predictions of an individualized dose-exposure-response relationship. A predictive model of this kind can be used to simulate and hence design clinical trials, find initial dosage regimens satisfying an optimality criterion on the population distribution of responses, and individualized regimens satisfying such a criterion conditional on individual features, such as sex, age, etc. Throughout we emphasize prediction and advocate mechanistic as opposed to empirical modelling, and argue that the Bayesian approach is particularly natural in this setting. PMID:10636334

  19. Zooplankton feeding ecology and the experimental acidification of Little Rock Lake

    SciTech Connect

    Sierszen, M.E.

    1988-01-01

    There is considerable variety in both the selective behavior of suspension feeders and the quality of food available to them. The author reviews this variability and incorporate it in a simple model of particle selection that quantifies the consequences of selective feeding under various feeding conditions. To evaluate the concept that selective feeding enhances fitness, the author tests the hypothesis than an herbivorous zooplankton selects food items that best support its reproduction. Investigations of zooplankton herbivory in experimentally acidified Little Rock Lake indicate that acidification from pH 6.2 to pH 5.2 has not directly impaired feeding rates, while effects on selective feeding behavior are evident. Assessment of the effects of lake acidification on large predatory zooplankton indicate that Chaoborus spp. and water mite populations remain as yet unaffected, while Epischura lacustris and Leptodora kindtii have both declined in the acidified basin. Methodological tests show that preservation of labelled zooplankton by rapid freezing on dry ice minimizes loss of {sup 14}C and {sup 32}P. {sup 14}C retention approximates 100%, while {sup 32}P retention is more variable.

  20. Bacteria of the gamma-subclass Proteobacteria associated with zooplankton in Chesapeake Bay.

    PubMed

    Heidelberg, J F; Heidelberg, K B; Colwell, R R

    2002-11-01

    The seasonal abundance of gamma-subclass Proteobacteria, Vibrio-Photobacterium, Vibrio cholerae-Vibrio mimicus, Vibrio cincinnatiensis, and Vibrio vulnificus in the Choptank River of Chesapeake Bay associated with zooplankton was monitored from April to December 1996. Large (>202- microm) and small (64- to 202- microm) size classes of zooplankton were collected, and the bacteria associated with each of the zooplankton size classes were enumerated by fluorescent oligonucleotide direct count. Large populations of bacteria were found to be associated with both the large and small size classes of zooplankton. Also, the species of bacteria associated with the zooplankton showed seasonal abundance, with the largest numbers occurring in the early spring and again in the summer, when zooplankton total numbers were correspondingly large. Approximately 0.01 to 40.0% of the total water column bacteria were associated with zooplankton, with the percentage of the total water column bacteria population associated with zooplankton varying by season. A taxonomically diverse group of bacteria was associated with zooplankton, and a larger proportion was found in and on zooplankton during the cooler months of the year, with selected taxa comprising a larger percent of the Bacteria in the summer. V. cholerae-V. mimicus and V. vulnificus comprised the bulk of the large and small zooplankton-associated Vibrio-Photobacterium species. In contrast, V. cincinnatiensis accounted for less than 0.1 to 3%. It is concluded that water column and zooplankton bacterial populations vary independently with respect to species composition since no correlation was observed between taxa occurring with highest frequency in the water column and those in association with zooplankton. PMID:12406743

  1. Modeling Population Growth and Extinction

    ERIC Educational Resources Information Center

    Gordon, Sheldon P.

    2009-01-01

    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,…

  2. Modeling Population Growth and Extinction

    ERIC Educational Resources Information Center

    Gordon, Sheldon P.

    2009-01-01

    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,

  3. Zooplankton of West Madagascar

    NASA Astrophysics Data System (ADS)

    Bemiasa, John; Remanevy, Sitraka

    2014-05-01

    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.

  4. Modeling sandhill crane population dynamics

    USGS Publications Warehouse

    Johnson, D.H.

    1979-01-01

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

  5. Rapid local adaptation mediates zooplankton community assembly in experimental mesocosms.

    PubMed

    Pantel, Jelena H; Duvivier, Cathy; Meester, Luc De

    2015-10-01

    Adaptive evolution can occur over similar timescales as ecological processes such as community assembly, but its particular effects on community assembly and structure and their magnitude are poorly understood. In experimental evolution trials, Daphnia magna were exposed to varying environments (presence and absence of fish and artificial macrophytes) for 2 months. Then, in a common gardening experiment, we compared zooplankton community composition when either experimentally adapted or D. magna from the original population were present. Local adaptation of D. magna significantly altered zooplankton community composition, leading to a suppression of abundances for some zooplankton taxa and facilitation for others. The effect size of D. magna adaptation was similar to that of adding fish or macrophytes to mesocosms, two important drivers of zooplankton community structure. Our results suggest that substantial amounts of variation in community composition in natural systems may be unexplained if evolutionary dynamics are ignored. PMID:26251339

  6. Estimating In Situ Zooplankton Non-Predation Mortality in an Oligo-Mesotrophic Lake from Sediment Trap Data: Caveats and Reality Check

    PubMed Central

    Dubovskaya, Olga P.; Tang, Kam W.; Gladyshev, Michail I.; Kirillin, Georgiy; Buseva, Zhanna; Kasprzak, Peter; Tolomeev, Aleksandr P.; Grossart, Hans-Peter

    2015-01-01

    Background Mortality is a main driver in zooplankton population biology but it is poorly constrained in models that describe zooplankton population dynamics, food web interactions and nutrient dynamics. Mortality due to non-predation factors is often ignored even though anecdotal evidence of non-predation mass mortality of zooplankton has been reported repeatedly. One way to estimate non-predation mortality rate is to measure the removal rate of carcasses, for which sinking is the primary removal mechanism especially in quiescent shallow water bodies. Objectives and Results We used sediment traps to quantify in situ carcass sinking velocity and non-predation mortality rate on eight consecutive days in 2013 for the cladoceran Bosmina longirostris in the oligo-mesotrophic Lake Stechlin; the outcomes were compared against estimates derived from in vitro carcass sinking velocity measurements and an empirical model correcting in vitro sinking velocity for turbulence resuspension and microbial decomposition of carcasses. Our results show that the latter two approaches produced unrealistically high mortality rates of 0.58-1.04 d-1, whereas the sediment trap approach, when used properly, yielded a mortality rate estimate of 0.015 d-1, which is more consistent with concurrent population abundance data and comparable to physiological death rate from the literature. Ecological implications Zooplankton carcasses may be exposed to water column microbes for days before entering the benthos; therefore, non-predation mortality affects not only zooplankton population dynamics but also microbial and benthic food webs. This would be particularly important for carbon and nitrogen cycles in systems where recurring mid-summer decline of zooplankton population due to non-predation mortality is observed. PMID:26146995

  7. Redwoods: a population model.

    PubMed

    Bosch, C A

    1971-04-23

    The chief conclusion to be drawn from the results of this study is that redwoods are amazingly vigorous. The results support both the lumber companies and the conservationists. There is no question that old growth giant redwoods must be preserved. Only commercial greed could be a basis for refuting that stand. On the other hand, the lumber companies seem to be supported in their contention that redwoods can be farmed without driving them to extinction. The central issue revolves around the old trees. And here profit is the big factor. Lumbering is an important industry in California, and redwood lumbering represents about 20 percent of the industry (l). Most of the big names in timber, such as Weyerhaeuser and Georgia-Pacific, are involved in logging the California redwood. At the current rate of logging, particularly of old growth stands, the Bank of America estimates that employment in Humboldt County will be down significantly by 1975 (4). It has been argued that tourism would more than compensate for the lower employment in logging. But not if the trees that the tourists come to see are gone. Why can't young and mature trees be harvested at a reasonable rate, the old trees saved, and both tourism and logging flourish? The question posed earlier has been answered. Redwood growth and survival can be modeled, using matrix methods in a new context. Meaningful conclusions may be drawn. And the results are sufficiently tantalizing to inspire further research. PMID:17756034

  8. Can microcystins affect zooplankton structure community in tropical eutrophic reservoirs?

    PubMed

    Paes, T A S V; Costa, I A S; Silva, A P C; Eskinazi-Sant'Anna, E M

    2016-06-01

    The aim of our study was to assess whether cyanotoxins (microcystins) can affect the composition of the zooplankton community, leading to domination of microzooplankton forms (protozoans and rotifers). Temporal variations in concentrations of microcystins and zooplankton biomass were analyzed in three eutrophic reservoirs in the semi-arid northeast region of Brazil. The concentration of microcystins in water proved to be correlated with the cyanobacterial biovolume, indicating the contributions from colonial forms such as Microcystis in the production of cyanotoxins. At the community level, the total biomass of zooplankton was not correlated with the concentration of microcystin (r2 = 0.00; P > 0.001), but in a population-level analysis, the biomass of rotifers and cladocerans showed a weak positive correlation. Cyclopoid copepods, which are considered to be relatively inefficient in ingesting cyanobacteria, were negatively correlated (r2 = - 0.01; P > 0.01) with the concentration of cyanotoxins. Surprisingly, the biomass of calanoid copepods was positively correlated with the microcystin concentration (r2 = 0.44; P > 0.001). The results indicate that allelopathic control mechanisms (negative effects of microcystin on zooplankton biomass) do not seem to substantially affect the composition of mesozooplankton, which showed a constant and high biomass compared to the microzooplankton (rotifers). These results may be important to better understand the trophic interactions between zooplankton and cyanobacteria and the potential effects of allelopathic compounds on zooplankton. PMID:26959954

  9. Zooplankton community responses to synthetic oil exposure

    SciTech Connect

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

    1985-01-01

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

  10. Optimal Foraging by Zooplankton

    NASA Astrophysics Data System (ADS)

    Garcia, Ricardo; Moss, Frank

    2007-03-01

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

  11. The zooplankton of the north sea

    NASA Astrophysics Data System (ADS)

    Fransz, H. G.; Colebrook, J. M.; Gamble, J. C.; Krause, M.

    This review summarizes available knowledge on herbivorous and omnivorous zooplankton of the North Sea. After an introductory chapter on history and general approach of zooplankton studies, the four main contributions review distribution patterns, cycles and trends in temporal variation, trophic interactions and population dyamics and production. The distribution of zooplankton species in relation to hydrography and origin of watermasses is described for copepods. It highlights the influence of Atlantic Ocean influx from the northwest, which to a large extent dominates the species composition and its seasonal variation in the summer-stratified waters. In contrast, the more neritic communities in the southeast region mainly depend on the local populations of the species abundant in coastal mixed waters. The chapter on cycles and trends in temporal variation discusses the differences in seasonal variation with respect to species, area, and community structure in terms of herbivores, omnivores and carnivores. The year-to-year changes are considered as dependent on the overwintering stocks and strategies. Patterns in long-term variation appearing from long-term data series are related to climatic changes, leading to two hypotheses with respect to the effects of changes in wind regime. The chapter on trophic interactions deals with the utilization of primary particulate production by planktonic herbivores and its variation in time and space. Emphasis is put on differences between north and south, which are partly due to differences in species composition, community structure and seasonal variation already discussed in foregoing chapters. The various aspects of copepod grazing are reviewed, but also the role of microzooplankton as both grazers and food organisms is brought to attention. The last chapter deals with population dynamics and production of key species. Seasonal fluctuations in abundance and biomass are discussed and related to underlying population processes and characteristics such as reproduction and life strategy, growth and development, and mortality. Secondary-production estimates inferred from biomass and growth rate estimates are discussed.

  12. [Population pharmacokinetic modeling of flurbiprofen].

    PubMed

    Wang, Chang-Lian; Lin, Wei-Wei; Gong, Shi-Ju; Huang, Pin-Fang

    2010-11-01

    The paper is to report the establishment of a population pharmacokinetic model for flurbiprofen (FP), an active metabolite of flurbiprofen axetil (FA). 246 FP serum concentration and clinical data were perspectively collected from 23 general anaesthesia patients receiving FA intravenously before operation in Dentofacial Surgery and Otorhinolaryngology Department of the First Affiliated Hospital of Fujian Medical University. Population pharmacokinetic data analysis was performed using NONMEM software. The measure of Bootstrap was applied for internal validation, while Visual Predictive check was adopted for external validation. The data of FP correspond with two-compartment model. The body weight (WT) had conspicuous effect on clearance and volume of central compartment, while sex, age and daily dose of administration had no marked effect on pharmacokinetic parameter of FP. The basic model was described as follows: CL (L x h(-1)) = 1.28x EXP(ETA(1)), V1 (L) = 5.03x EXP(ETA(2)), Q (L x h(-1)) = 8.5 x EXP(ETA(3)), V2 (L) = 4.39 x EXP(ETA(4)). The final model was described as follows: CL (L x h(-1)) = 1.32 x (WT/60) x EXP(ETA(1)), V1 (L) = 5.23 x (WT/60) x EXP(ETA(2)), Q (L x h(-1)) = 8.45 x EXP(ETA(3)), V2 (L) = 4.37 x EXP(ETA(4)). The population typical value of CL, V1, Q and V2 were: 1.32 L x h(-1), 5.23 L, 8.45 L x h(-1) and 4.37 L, respectively. Bootstrap and visual predictive check show that the final model of FP is stable, effective and predictable. A novel population pharmacokinetic model is developed to estimate the individual pharmacokinetic parameter for patients intravenous injecting FA in terms of patients' characteristics and dosing history, and to design a prior dosage regimen. PMID:21361044

  13. Quantifying Preferences and Responsiveness of Marine Zooplankton to Changing Environmental Conditions using Microfluidics

    PubMed Central

    Merten, Christoph A.; Arendt, Detlev

    2015-01-01

    Global environmental change significantly affects marine species composition. However, analyzing the impact of these changes on marine zooplankton communities was so far mostly limited to assessing lethal doses through mortality assays and hence did not allow a direct assessment of the preferred conditions, or preferendum. Here, we use a microfluidic device to characterize individual behavior of actively swimming zooplankton, and to quantitatively determine their ecological preferendum. For the annelid zooplankton model Platynereis dumerilii we observe a broader pH preferendum than for the copepod Euterpina acutifrons, and reveal previously unrecognized sub-populations with different pH preferenda. For Platynereis, the minimum concentration difference required to elicit a response (responsiveness) is ~1 μM for H+ and ~13.7 mM for NaCl. Furthermore, using laser ablations we show that olfactomedin-expressing sensory cells mediate chemical responsiveness in the Platynereis foregut. Taken together, our microfluidic approach allows precise assessment and functional understanding of environmental perception on planktonic behaviour. PMID:26517120

  14. Modelling nova populations in galaxies

    NASA Astrophysics Data System (ADS)

    Chen, Hai-Liang; Woods, T. E.; Yungelson, L. R.; Gilfanov, M.; Han, Zhanwen

    2016-02-01

    Theoretical modelling of the evolution of classical and recurrent novae plays an important role in studies of binary evolution, nucleosynthesis and accretion physics. However, from a theoretical perspective the observed statistical properties of novae remain poorly understood. In this paper, we have produced model populations of novae using a hybrid binary population synthesis approach for differing star formation histories (SFHs): a starburst case (elliptical-like galaxies), a constant star formation rate case (spiral-like galaxies) and a composite case (in line with the inferred SFH for M31). We found that the nova rate at 10 Gyr in an elliptical-like galaxy is ˜10 - 20 times smaller than a spiral-like galaxy with the same mass. The majority of novae in elliptical-like galaxies at the present epoch are characterized by low mass white dwarfs (WDs), long decay times, relatively faint absolute magnitudes and long recurrence periods. In contrast, the majority of novae in spiral-like galaxies at 10 Gyr have massive WDs, short decay times, are relatively bright and have short recurrence periods. The mass loss time distribution for novae in our M31-like galaxy is in agreement with observational data for Andromeda. However, it is possible that we underestimate the number of bright novae in our model. This may arise in part due to the present uncertainties in the appropriate bolometric correction for novae.

  15. Modelling nova populations in galaxies

    NASA Astrophysics Data System (ADS)

    Chen, Hai-Liang; Woods, T. E.; Yungelson, L. R.; Gilfanov, M.; Han, Zhanwen

    2016-05-01

    Theoretical modelling of the evolution of classical and recurrent novae plays an important role in studies of binary evolution, nucleosynthesis and accretion physics. However, from a theoretical perspective the observed statistical properties of novae remain poorly understood. In this paper, we have produced model populations of novae using a hybrid binary population synthesis approach for differing star formation histories (SFHs): a starburst case (elliptical-like galaxies), a constant star formation rate case (spiral-like galaxies) and a composite case (in line with the inferred SFH for M31). We found that the nova rate at 10 Gyr in an elliptical-like galaxy is ˜10-20 times smaller than a spiral-like galaxy with the same mass. The majority of novae in elliptical-like galaxies at the present epoch are characterized by low-mass white dwarfs (WDs), long decay times, relatively faint absolute magnitudes and long recurrence periods. In contrast, the majority of novae in spiral-like galaxies at 10 Gyr have massive WDs, short decay times, are relatively bright and have short recurrence periods. The mass-loss time distribution for novae in our M31-like galaxy is in agreement with observational data for Andromeda. However, it is possible that we underestimate the number of bright novae in our model. This may arise in part due to the present uncertainties in the appropriate bolometric correction for novae.

  16. Physical control of zooplankton communities in the Catalan Sea

    NASA Astrophysics Data System (ADS)

    Alcaraz, M.; Calbet, A.; Estrada, M.; Marrasé, C.; Saiz, E.; Trepat, I.

    2007-08-01

    The study of the response of planktonic systems to environmental variability, and particularly to differences in the intensity and frequency of mechanical energy inputs, one of the leading objectives of GLOBEC, has been an important part of the research developed in the Spanish Mediterranean over the last decades. In this review we will discuss the research conducted at different space and time scales, intended to cope with the broad space and time variability scales of plankton. The time- and space scales considered range from small- (i.e., from seconds and mm, affecting zooplankton at individual level) to meso- (weeks and tens of km) and large scales (i.e., seasonal changes in the density structure of the water column). The discussion includes laboratory research using visual observation techniques at individual level, the use of experimental micro- and mesocosms, as well as data obtained by sampling natural systems during oceanographic cruises. At the smaller scales, mechanical energy inputs produce turbulent water movements that enhance the encounter probability between zooplankton and their prey, modify their swimming behaviour (higher frequency of fast-swimming events, escape responses), increase metabolic rates and affect energetic balances. Consequently, the development of organisms is accelerated, and the size of adults significantly reduced. The changes induced by turbulence on zooplankton at individual levels modify, by cumulative processes, the characteristics of zooplankton populations and of the whole planktonic ecosystems. Such changes can be observed by using micro- and mesocosm experiments. The physical control of zooplankton communities can also be observed, even at larger scales, in the highly hydrodynamic physical structures (i.e., fronts and ergoclines) of the Catalan Sea (NW Mediterranean). In these structures mechanical energy inputs are amplified, resulting in turbulence increases that contribute to modify, from individual rate processes, the structural and functional characteristics of plankton communities and of the whole ecosystem. Mesoscale hydrographic features, particularly the Catalan and Balearic permanent density fronts and the central divergence, are important fertilization sources for the relatively productive Catalan Sea. But during summer stratification, the nutrient depletion of surface waters and the higher penetration of light allow the development of a deep phytoplankton maximum. The consequence is the formation of a deep zooplankton maximum coinciding with that of phytoplankton. The vertical migration patterns of zooplankton during summer result in significant nocturnal inputs of recycled nutrients to the surface, thus counteracting the vertical downward flux of nutrients. The spatial distribution of zooplankton biomass and metabolic rates appear to be closely related to the physical characteristics of the different hydrographic features. Similarly, the intensity and the temporal and spatial scales of variability of the structural and functional properties of zooplankton are closely linked to those of the physical structures.

  17. Matrix population models from 20 studies of perennial plant populations

    USGS Publications Warehouse

    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

    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.

  18. Matrix population models from 20 studies of perennial plant populations

    USGS Publications Warehouse

    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

    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.

  19. A three-dimensional biophysical model of Karenia brevis dynamics on the west Florida shelf: A look at physical transport and potential zooplankton grazing controls

    NASA Astrophysics Data System (ADS)

    Milroy, Scott P.; Dieterle, Dwight A.; He, Ruoying; Kirkpatrick, Gary J.; Lester, Kristen M.; Steidinger, Karen A.; Vargo, Gabriel A.; Walsh, John J.; Weisberg, Robert H.

    2008-01-01

    The development of accurate predictive models of toxic dinoflagellate blooms is of great ecological importance, particularly in regions that are most susceptible to their detrimental effects. This is especially true along the west Florida shelf (WFS) and coast, where episodic bloom events of the toxic dinoflagellate Karenia brevis often wreak havoc on the valuable commercial fisheries and tourism industries of west Florida. In an effort to explain the dynamics at work within the maintenance and termination phases of a red tide, a simple three-dimensional coupled biophysical model was used in the analysis of the October 1999 red tide offshore Sarasota, Florida. Results of the numerical experiments indicate that: (1) measured and modeled flowfields were capable of transporting the observed offshore inoculum of K. brevis to within 16 km of the coastal boundary; (2) background concentrations (1000 cells L -1) of K. brevis could grow to a red tide of over 2×10 6 cells L -1 in little more than a month, assuming an estuarine initiation site with negligible offshore advection, no grazing losses, negligible competition from other phytoplankton groups, and no nutrient limitation; (3) maximal grazing pressure could not prevent the initiation of a red tide or cause its termination, assuming no other losses to algal biomass and a zooplankton community ingestion rate similar to that of Acartia tonsa; and (4) the light-cued ascent behavior of K. brevis served as an aggregational mechanism, concentrating K. brevis at the 55 μE m -2 s -1 isolume when mean concentrations of K. brevis exceeded 100,000 cells L -1. Further improvements in model fidelity will be accomplished by the future inclusion of phytoplankton competitors, disparate nutrient availability and limitation schemes, a more realistic rendering of the spectral light field and the attendant effects of photo-inhibition and compensation, and a mixed community of vertically-migrating proto- and metazoan grazers. These model refinements are currently under development and shall be used to aid progress toward an operational model of red tide forecasting along the WFS.

  20. Modeling population dynamics: A quantile approach.

    PubMed

    Chavas, Jean-Paul

    2015-04-01

    The paper investigates the modeling of population dynamics, both conceptually and empirically. It presents a reduced form representation that provides a flexible characterization of population dynamics. It leads to the specification of a threshold quantile autoregression (TQAR) model, which captures nonlinear dynamics by allowing lag effects to vary across quantiles of the distribution as well as with previous population levels. The usefulness of the model is illustrated in an application to the dynamics of lynx population. We find statistical evidence that the quantile autoregression parameters vary across quantiles (thus rejecting the AR model as well as the TAR model) as well as with past populations (thus rejecting the quantile autoregression QAR model). The results document the nature of dynamics and cycle in the lynx population over time. They show how both the period of the cycle and the speed of population adjustment vary with population level and environmental conditions. PMID:25661501

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

    USGS Publications Warehouse

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

    2011-01-01

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

  2. 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...

  3. ZOOPLANKTON AS A FOOD SOURCE

    EPA Science Inventory

    While thousands of zooplankton species could potentially serve as food for larval stages of cultured fish and crustaceans, the aquaculturists practical choice of a reproducible live food ratio is quite limited. In practice, rotifers and brine shrimp are the most commonly used zoo...

  4. Role of zooplankton dynamics for Southern Ocean phytoplankton biomass and global biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Le Quéré, C.; Buitenhuis, E. T.; Moriarty, R.; Alvain, S.; Aumont, O.; Bopp, L.; Chollet, S.; Enright, C.; Franklin, D. J.; Geider, R. J.; Harrison, S. P.; Hirst, A.; Larsen, S.; Legendre, L.; Platt, T.; Prentice, I. C.; Rivkin, R. B.; Sathyendranath, S.; Stephens, N.; Vogt, M.; Sailley, S.; Vallina, S. M.

    2015-07-01

    Global ocean biogeochemistry models currently employed in climate change projections use highly simplified representations of pelagic food webs. These food webs do not necessarily include critical pathways by which ecosystems interact with ocean biogeochemistry and climate. Here we present a global biogeochemical model which incorporates ecosystem dynamics based on the representation of ten plankton functional types (PFTs); six types of phytoplankton, three types of zooplankton, and heterotrophic bacteria. We improved the representation of zooplankton dynamics in our model through (a) the explicit inclusion of large, slow-growing zooplankton, and (b) the introduction of trophic cascades among the three zooplankton types. We use the model to quantitatively assess the relative roles of iron vs. grazing in determining phytoplankton biomass in the Southern Ocean High Nutrient Low Chlorophyll (HNLC) region during summer. When model simulations do not represent crustacean macrozooplankton grazing, they systematically overestimate Southern Ocean chlorophyll biomass during the summer, even when there was no iron deposition from dust. When model simulations included the developments of the zooplankton component, the simulation of phytoplankton biomass improved and the high chlorophyll summer bias in the Southern Ocean HNLC region largely disappeared. Our model results suggest that the observed low phytoplankton biomass in the Southern Ocean during summer is primarily explained by the dynamics of the Southern Ocean zooplankton community rather than iron limitation. This result has implications for the representation of global biogeochemical cycles in models as zooplankton faecal pellets sink rapidly and partly control the carbon export to the intermediate and deep ocean.

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

    PubMed

    Gray, Derek K; Arnott, Shelley E

    2011-06-01

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

  6. Comparing models of Red Knot population dynamics

    USGS Publications Warehouse

    McGowan, Conor

    2015-01-01

    Predictive population modeling contributes to our basic scientific understanding of population dynamics, but can also inform management decisions by evaluating alternative actions in virtual environments. Quantitative models mathematically reflect scientific hypotheses about how a system functions. In Delaware Bay, mid-Atlantic Coast, USA, to more effectively manage horseshoe crab (Limulus polyphemus) harvests and protect Red Knot (Calidris canutus rufa) populations, models are used to compare harvest actions and predict the impacts on crab and knot populations. Management has been chiefly driven by the core hypothesis that horseshoe crab egg abundance governs the survival and reproduction of migrating Red Knots that stopover in the Bay during spring migration. However, recently, hypotheses proposing that knot dynamics are governed by cyclical lemming dynamics garnered some support in data analyses. In this paper, I present alternative models of Red Knot population dynamics to reflect alternative hypotheses. Using 2 models with different lemming population cycle lengths and 2 models with different horseshoe crab effects, I project the knot population into the future under environmental stochasticity and parametric uncertainty with each model. I then compare each model's predictions to 10 yr of population monitoring from Delaware Bay. Using Bayes' theorem and model weight updating, models can accrue weight or support for one or another hypothesis of population dynamics. With 4 models of Red Knot population dynamics and only 10 yr of data, no hypothesis clearly predicted population count data better than another. The collapsed lemming cycle model performed best, accruing ~35% of the model weight, followed closely by the horseshoe crab egg abundance model, which accrued ~30% of the weight. The models that predicted no decline or stable populations (i.e. the 4-yr lemming cycle model and the weak horseshoe crab effect model) were the most weakly supported.

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

    NASA Astrophysics Data System (ADS)

    Lehane, Clare; Davenport, John

    2006-05-01

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

  8. Spatial and Temporal Variations in the Zooplankton Community of Phosphorescent Bay, Puerto Rico

    NASA Astrophysics Data System (ADS)

    Rios-Jara, E.

    1998-06-01

    Nocturnal variations of zooplankton abundance and hydrographic conditions were examined at three locations (centre, north shore and south shore) in Phosphorescent Bay, Puerto Rico, from May 1992 through April 1993. Seven taxa accounted for approximately 96% of the annual mean zooplankton abundance: Oithonaspp. (43·5%), Acartia tonsa(31·5%), copepod nauplii (8·8%), Paracalanusspp.(6·7%), gastropod veligers (2·5%), larvaceans (1·7%) and Pseudo-diaptomus cokeri(1·6%). Copepods dominated numerically throughout the year and comprised 94·3% of total zooplankton. Higher abundance of zooplankton (mean±1 SD=252 259±176 797 individuals m -3) was associated with cool water temperatures (24·9-27·4 °C) and dry conditions (0·3-2·9 cm precipitation/month) which prevailed between December and March relative to the period between April and November (warm/wet season) (mean±1 SD=59 773±26 861 individuals m -3), when temperature and precipitation were higher (27·3-30·3 °C, 3·1-20·6 cm month -1). Fluctuations of zooplankton populations, particularly copepods, followed progressive increments in chlorophyll aconcentrations. This abundance pattern was consistent at the three sampling stations. Zooplankton abundance was higher on the north shore of the bay. The taxonomic composition of zooplankton was similar at the sampling stations studied.

  9. Modelling population change from time series data

    USGS Publications Warehouse

    Barker, R.J.; Sauer, J.R.

    1992-01-01

    Information on change in population size over time is among the most basic inputs for population management. Unfortunately, population changes are generally difficult to identify, and once identified difficult to explain. Sources of variald (patterns) in population data include: changes in environment that affect carrying capaciyy and produce trend, autocorrelative processes, irregular environmentally induced perturbations, and stochasticity arising from population processes. In addition. populations are almost never censused and many surveys (e.g., the North American Breeding Bird Survey) produce multiple, incomplete time series of population indices, providing further sampling complications. We suggest that each source of pattern should be used to address specific hypotheses regarding population change, but that failure to correctly model each source can lead to false conclusions about the dynamics of populations. We consider hypothesis tests based on each source of pattern, and the effects of autocorrelated observations and sampling error. We identify important constraints on analyses of time series that limit their use in identifying underlying relationships.

  10. Mathematical Modeling of Extinction of Inhomogeneous Populations.

    PubMed

    Karev, G P; Kareva, I

    2016-04-01

    Mathematical models of population extinction have a variety of applications in such areas as ecology, paleontology and conservation biology. Here we propose and investigate two types of sub-exponential models of population extinction. Unlike the more traditional exponential models, the life duration of sub-exponential models is finite. In the first model, the population is assumed to be composed of clones that are independent from each other. In the second model, we assume that the size of the population as a whole decreases according to the sub-exponential equation. We then investigate the "unobserved heterogeneity," i.e., the underlying inhomogeneous population model, and calculate the distribution of frequencies of clones for both models. We show that the dynamics of frequencies in the first model is governed by the principle of minimum of Tsallis information loss. In the second model, the notion of "internal population time" is proposed; with respect to the internal time, the dynamics of frequencies is governed by the principle of minimum of Shannon information loss. The results of this analysis show that the principle of minimum of information loss is the underlying law for the evolution of a broad class of models of population extinction. Finally, we propose a possible application of this modeling framework to mechanisms underlying time perception. PMID:27090117

  11. Mathematical Modeling of Extinction of Inhomogeneous Populations

    PubMed Central

    Karev, G.P.; Kareva, I.

    2016-01-01

    Mathematical models of population extinction have a variety of applications in such areas as ecology, paleontology and conservation biology. Here we propose and investigate two types of sub-exponential models of population extinction. Unlike the more traditional exponential models, the life duration of sub-exponential models is finite. In the first model, the population is assumed to be composed clones that are independent from each other. In the second model, we assume that the size of the population as a whole decreases according to the sub-exponential equation. We then investigate the “unobserved heterogeneity”, i.e. the underlying inhomogeneous population model, and calculate the distribution of frequencies of clones for both models. We show that the dynamics of frequencies in the first model is governed by the principle of minimum of Tsallis information loss. In the second model, the notion of “internal population time” is proposed; with respect to the internal time, the dynamics of frequencies is governed by the principle of minimum of Shannon information loss. The results of this analysis show that the principle of minimum of information loss is the underlying law for the evolution of a broad class of models of population extinction. Finally, we propose a possible application of this modeling framework to mechanisms underlying time perception. PMID:27090117

  12. POPULATION MODELS IN ECOLOGICAL RISK ASSESSMENT

    EPA Science Inventory

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

  13. Population Modelling with M&M's[R

    ERIC Educational Resources Information Center

    Winkel, Brian

    2009-01-01

    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.)

  14. Modeling wildlife populations with HexSim

    EPA Science Inventory

    HexSim is a framework for constructing spatially-explicit, individual-based computer models designed for simulating terrestrial wildlife population dynamics and interactions. HexSim is useful for a broad set of modeling applications including population viability analysis for on...

  15. Statistical Models of Adaptive Immune populations

    NASA Astrophysics Data System (ADS)

    Sethna, Zachary; Callan, Curtis; Walczak, Aleksandra; Mora, Thierry

    The availability of large (104-106 sequences) datasets of B or T cell populations from a single individual allows reliable fitting of complex statistical models for naïve generation, somatic selection, and hypermutation. It is crucial to utilize a probabilistic/informational approach when modeling these populations. The inferred probability distributions allow for population characterization, calculation of probability distributions of various hidden variables (e.g. number of insertions), as well as statistical properties of the distribution itself (e.g. entropy). In particular, the differences between the T cell populations of embryonic and mature mice will be examined as a case study. Comparing these populations, as well as proposed mixed populations, provides a concrete exercise in model creation, comparison, choice, and validation.

  16. Habitat Heterogeneity Determines Climate Impact on Zooplankton Community Structure and Dynamics

    PubMed Central

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

    2014-01-01

    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

  17. Accumulation and cycling of polycyclic aromatic hydrocarbons in zooplankton.

    PubMed

    Berrojalbiz, Naiara; Lacorte, Silvia; Calbet, Albert; Saiz, Enric; Barata, Carlos; Dachs, Jordi

    2009-04-01

    Planktonic food webs play an important role driving the environmental fate of persistent organic pollutants, and POP accumulation in phytoplankton has been previously studied for its importance as a first step in the aquatic food webs. However, little is known about the accumulation and cycling of organic pollutants between zooplankton and water. The present study shows the results of laboratory experiments on the bioconcentration (by passive uptake) of polycyclic aromatic hydrocarbons in phytoplankton (Rhodomonas salina) and accumulation in copepods (Paracartia(acartia) granm), by ingestion and diffusion. Both bioconcentration (BCF) and bioaccumulation (BAF) factors show significant correlation with the octanol-water partition coefficient (Kow) for phytoplankton and zooplankton. The BCF values for phytoplankton were 2 orders of magnitude higher than those for copepods. The analysis of fecal pellets shows that elimination by defecation is mainly significant for PAHs taken up from ingested phytoplankton but not due to passive uptake. However, the dominant elimination mechanisms are by far metabolism and diffusive depuration. Indeed, the mass balance suggests that metabolism of PAHs by copepods is a significant process that could play a role in the fate of PAHs in the water column. Uptake, depuration, eggestion, and ingestion rates increased with hydrophobicity of the chemical, while the metabolism rate was slightly higher for the less hydrophobic compounds. Passive partitioning dominated the accumulation of POPs in zooplankton. The derivation of all the uptake and loss rate constants for PAHs opens the doorto future modeling studies of the role of zooplankton in PAH cycling in the marine environment. PMID:19452877

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

    SciTech Connect

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

    1993-08-01

    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.

  19. A simplified model of spatiotemporal population dynamics.

    PubMed

    Puu, T

    1985-09-01

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

  20. Calvert Cliffs zooplankton entrainment study. Final report

    SciTech Connect

    Bradley, B.P.

    1980-01-01

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

  1. Incorporating evolutionary processes into population viability models.

    PubMed

    Pierson, Jennifer C; Beissinger, Steven R; Bragg, Jason G; Coates, David J; Oostermeijer, J Gerard B; Sunnucks, Paul; Schumaker, Nathan H; Trotter, Meredith V; Young, Andrew G

    2015-06-01

    We examined how ecological and evolutionary (eco-evo) processes in population dynamics could be better integrated into population viability analysis (PVA). Complementary advances in computation and population genomics can be combined into an eco-evo PVA to offer powerful new approaches to understand the influence of evolutionary processes on population persistence. We developed the mechanistic basis of an eco-evo PVA using individual-based models with individual-level genotype tracking and dynamic genotype-phenotype mapping to model emergent population-level effects, such as local adaptation and genetic rescue. We then outline how genomics can allow or improve parameter estimation for PVA models by providing genotypic information at large numbers of loci for neutral and functional genome regions. As climate change and other threatening processes increase in rate and scale, eco-evo PVAs will become essential research tools to evaluate the effects of adaptive potential, evolutionary rescue, and locally adapted traits on persistence. PMID:25494697

  2. Zooplankton community changes confound the biodilution theory of methylmercury accumulation in a recovering mercury-contaminated lake.

    PubMed

    Todorova, Svetoslava; Driscoll, Charles T; Matthews, David A; Effler, Steven W

    2015-04-01

    In this study, the biodilution hypothesis of methylmercury (MeHg) accumulation was examined in a Hg-contaminated ecosystem that has undergone concurrent changes in nutrient loading and zooplankton community composition. Using a long-term record of 17 years (between 1980 and 2009), we demonstrate that zooplankton MeHg concentrations in Onondaga Lake, NY, are strongly driven by changes in the zooplankton community and body size. MeHg concentrations in zooplankton increased with an increase in body size and biomass. The highest concentrations of MeHg were observed under eutrophic and hypereutrophic conditions when large-bodied Daphnia species, Daphnia pulicaria and Daphnia galeata mendotae, were present. Bioconcentration rather than biodilution was governing the accumulation of MeHg in zooplankton without apparent growth dilution or zooplankton biomass dilution. Algal-bloom dilution controlled the variability in the MeHg concentration only under hypereutrophic conditions when Ceriodaphnia predominated the cladoceran population. Our study demonstrates that changes in zooplankton community composition confound the biodilution theory in Onondaga Lake and that the presence of large-bodied zooplankton species drives elevated MeHg concentrations. PMID:25741879

  3. The Career Counseling with Underserved Populations Model

    ERIC Educational Resources Information Center

    Pope, Mark

    2011-01-01

    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.

  4. Zooplankton data report: Winter MIZEX, 1987

    SciTech Connect

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

    1988-12-01

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

  5. A Population Health Model for Integrated Assessment Models

    SciTech Connect

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

    2008-05-01

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

  6. Fluctuations in a coupled population model

    NASA Astrophysics Data System (ADS)

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

    2005-07-01

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

  7. Modeling Small Stellar Populations Using Starburst99

    NASA Astrophysics Data System (ADS)

    Vazquez, Gerardo Arturo; Leitherer, Claus

    2015-08-01

    Stellar populations synthesis models have proven to be excellent tools to learn about galaxy evolution. However, modeling small stellar populations (lower than 105 M⊙) has been an intriguing and continuous to be a field of intensive research. In this work, we have developed a new approach to form stars from clusters first, where massive stars are formed from fractions of mass of small stellar clusters. This new approximation is based on the empirical power law (mc-2) for the mass function of clusters between 20-1100 M⊙ found in recent years and the maximum stellar mass that can be formed in a cluster. Incorporating this new approach to form clusters has made us upgrade the way we integrate the stellar properties and the way that the isochrone is produced with a new technique. To produce the new models we have used the most recent version of Starburst99 that incorporates the most recent stellar evolution models with rotation. On the verge of solving nearby stellar populations and observing small stellar populations across the universe, this new approach brings a new scope on trying to disentangle the nature of hyper and supermassive stars in small stellar populations. In this work we present this new approach and the results when these models are applied to very energetic stellar populations such as the cluster in NGC 3603. Our most important result is that we have modeled the ionizing power of this cluster and some others by forming enough supermassive stars in a cluster of ~104 M⊙.

  8. Feeding and production of zooplankton in the Catalan Sea (NW Mediterranean)

    NASA Astrophysics Data System (ADS)

    Saiz, Enric; Calbet, Albert; Atienza, Dacha; Alcaraz, Miquel

    2007-08-01

    Zooplankton are key components of the structure and functioning of marine planktonic food webs. They are the main link of planktonic primary production towards top pelagic consumer levels (fish), and play a relevant role on the nutrient recycling in the water column and on the export of particulate matter out of the photic zone. In this paper, we review the present knowledge on the feeding and production of zooplankton in the Catalan Sea (NW Mediterranean), with special emphasis on copepods. Feeding of zooplankton in the Catalan Sea appears typically food limited, with average daily rations on a yearly basis in the order of 48% body C d -1. Heterotrophic prey constitute a relevant fraction of their diet, as an alternative to the scarce phytoplankton in the area. From a structural point of view, the trophic impact and control of their prey populations are low on standing stocks but, at certain times, zooplankton can exert a meaningful effect on their prey production. Regarding zooplankton production, the available estimates of growth rates in the area are based on the egg production rate of copepods. Egg production rates appear to be limited, especially in summer. Tentative estimates of copepod production in the area are in the order of 20-40 mg C m -2 d -1. In conclusion, this review confirms that the oligotrophic character of the NW Mediterranean constrains the feeding activity and production of zooplankton.

  9. Ecosystem model-based approach for modelling the dynamics of 137Cs transfer to marine plankton populations: application to the western North Pacific Ocean after the Fukushima nuclear power plant accident

    NASA Astrophysics Data System (ADS)

    Belharet, M.; Estournel, C.; Charmasson, S.

    2015-06-01

    Huge amounts of radionuclides, especially 137Cs, were released into the western North Pacific Ocean after the Fukushima nuclear power plant (FNPP) accident that occurred on 11 March 2011, resulting in contamination of the marine biota. In this study we developed a radioecological model to estimate 137Cs concentrations in phytoplankton and zooplankton populations representing the lower levels of the pelagic trophic chain. We coupled this model to a lower trophic level ecosystem model and an ocean circulation model to take into account the site-specific environmental conditions in the area. The different radioecological parameters of the model were estimated by calibration, and a sensitivity analysis to parameter uncertainties was carried out, showing a high sensitivity of the model results, especially to the 137Cs concentration in seawater, to the rates of uptake from water and to the radionuclide assimilation efficiency for zooplankton. The results of the 137Cs concentrations in planktonic populations simulated in this study were then validated through comparison with the some data available in the region after the accident. The model results have shown that the maximum concentrations in plankton after the accident were about two to four orders of magnitude higher than those observed before the accident depending on the distance from FNPP. Finally, the maximum 137Cs absorbed dose rate for phyto- and zooplankton populations was estimated to be about 10-2 μGy h-1, and was, therefore, lower than the 10 μGy h-1 benchmark value defined in the ERICA assessment approach from which a measurable effect on the marine biota can be observed.

  10. Disentangling the mechanisms behind climate effects on zooplankton.

    PubMed

    Kvile, Kristina Ø; Langangen, Øystein; Prokopchuk, Irina; Stenseth, Nils C; Stige, Leif C

    2016-02-16

    Understanding how climate influences ecosystems is complicated by the many correlated and interrelated impacting factors. Here we quantify climate effects on Calanus finmarchicus in the northeastern Norwegian Sea and southwestern Barents Sea. By combining oceanographic drift models and statistical analyses of field data from 1959 to 1993 and investigating effects across trophic levels, we are able to elucidate pathways by which climate influences zooplankton. The results show that both chlorophyll biomass in spring and C. finmarchicus biomass in summer relate positively to a combination of shallow mixed layer depth and increased wind in spring, suggesting that C. finmarchicus biomass in summer is influenced by bottom-up effects of food availability. Furthermore, spatially resolved C. finmarchicus biomass in summer is linked to favorable transport from warmer, core areas to the south. However, increased mean temperature in spring does not lead to increased C. finmarchicus biomass in summer. Rather, spring biomass is generally higher, but population growth from spring to summer is lower, after a warm compared with a cold spring. Our study illustrates how improved understanding of climate effects can be obtained when different datasets and different methods are combined in a unified approach. PMID:26831099

  11. Disentangling the mechanisms behind climate effects on zooplankton

    PubMed Central

    Kvile, Kristina Ø.; Langangen, Øystein; Prokopchuk, Irina; Stenseth, Nils C.; Stige, Leif C.

    2016-01-01

    Understanding how climate influences ecosystems is complicated by the many correlated and interrelated impacting factors. Here we quantify climate effects on Calanus finmarchicus in the northeastern Norwegian Sea and southwestern Barents Sea. By combining oceanographic drift models and statistical analyses of field data from 1959 to 1993 and investigating effects across trophic levels, we are able to elucidate pathways by which climate influences zooplankton. The results show that both chlorophyll biomass in spring and C. finmarchicus biomass in summer relate positively to a combination of shallow mixed layer depth and increased wind in spring, suggesting that C. finmarchicus biomass in summer is influenced by bottom-up effects of food availability. Furthermore, spatially resolved C. finmarchicus biomass in summer is linked to favorable transport from warmer, core areas to the south. However, increased mean temperature in spring does not lead to increased C. finmarchicus biomass in summer. Rather, spring biomass is generally higher, but population growth from spring to summer is lower, after a warm compared with a cold spring. Our study illustrates how improved understanding of climate effects can be obtained when different datasets and different methods are combined in a unified approach. PMID:26831099

  12. Population-expression models of immune response

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

    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.

  13. Design issues for population growth models

    PubMed Central

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

    2010-01-01

    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

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

    SciTech Connect

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

    1980-04-01

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

  15. Bivalves: From individual to population modelling

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    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.

  16. Cell population modelling of yeast glycolytic oscillations.

    PubMed Central

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

    2002-01-01

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

  17. 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...

  18. Spatial effects in discrete generation population models.

    PubMed

    Carrillo, C; Fife, P

    2005-02-01

    A framework is developed for constructing a large class of discrete generation, continuous space models of evolving single species populations and finding their bifurcating patterned spatial distributions. Our models involve, in separate stages, the spatial redistribution (through movement laws) and local regulation of the population; and the fundamental properties of these events in a homogeneous environment are found. Emphasis is placed on the interaction of migrating individuals with the existing population through conspecific attraction (or repulsion), as well as on random dispersion. The nature of the competition of these two effects in a linearized scenario is clarified. The bifurcation of stationary spatially patterned population distributions is studied, with special attention given to the role played by that competition. PMID:15480674

  19. Population Genetic Models of Genomic Imprinting

    PubMed Central

    Pearce, G. P.; Spencer, H. G.

    1992-01-01

    The phenomenon of genomic imprinting has recently excited much interest among experimental biologists. The population genetic consequences of imprinting, however, have remained largely unexplored. Several population genetic models are presented and the following conclusions drawn: (i) systems with genomic imprinting need not behave similarly to otherwise identical systems without imprinting; (ii) nevertheless, many of the models investigated can be shown to be formally equivalent to models without imprinting; (iii) consequently, imprinting often cannot be discovered by following allele frequency changes or examining equilibrium values; (iv) the formal equivalences fail to preserve some well known properties. For example, for populations incorporating genomic imprinting, parameter values exist that cause these populations to behave like populations without imprinting, but with heterozygote advantage, even though no such advantage is present in these imprinting populations. We call this last phenomenon ``pseudoheterosis.'' The imprinting systems that fail to be formally equivalent to nonimprinting systems are those in which males and females are not equivalent, i.e., two-sex viability systems and sex-chromosome inactivation. PMID:1582564

  20. Expanding clinical applications of population pharmacodynamic modelling.

    PubMed

    Minto, C; Schnider, T

    1998-10-01

    Population pharmacokinetics or pharmacodynamics is the study of the variability in drug concentration or pharmacological effect between individuals when standard dosage regimens are administered. We provide an overview of pharmacokinetic models, pharmacodynamic models, population models and residual error models. We outline how population modelling approaches seek to explain interpatient variability with covariate analysis, and, in some approaches, to characterize the unexplained interindividual variability. The interpretation of the results of population modelling approaches is facilitated by shifting the emphasis from the perspective of the modeller to the perspective of the clinician. Both the explained and unexplained interpatient variability should be presented in terms of their impact on the dose-response relationship. Clinically relevant questions relating to the explained and unexplained variability in the population can be posed to the model, and confidence intervals can be obtained for the fraction of the population that is estimated to fall within a specific therapeutic range given a certain dosing regimen. Such forecasting can be used to develop optimal initial dosing guidelines. The development of population models (with random effects) permits the application of Bayes's formula to obtain improved estimates of an individual's pharmacokinetic and pharmacodynamic parameters in the light of observed responses. An important challenge to clinical pharmacology is to identify the drugs that might benefit from such adaptive-control-with-feedback dosing strategies. Drugs used for life threatening diseases with a proven pharmacokinetic-pharmacodynamic relationship, a small therapeutic range, large interindividual variability, small interoccasion variability and severe adverse effects are likely to be good candidates. Rapidly evolving changes in health care economics and consumer expectations make it unlikely that traditional drug development approaches will succeed in the future. A shift away from the narrow focus on rejecting the null hypothesis towards a broader focus on seeking to understand the factors that influence the dose-response relationship--together with the development of the next generation of software based on population models--should permit a more efficient and rational drug development programme. PMID:9803979

  1. Bayesian population modeling of drug dosing adherence.

    PubMed

    Fellows, Kelly; Stoneking, Colin J; Ramanathan, Murali

    2015-10-01

    Adherence is a frequent contributing factor to variations in drug concentrations and efficacy. The purpose of this work was to develop an integrated population model to describe variation in adherence, dose-timing deviations, overdosing and persistence to dosing regimens. The hybrid Markov chain-von Mises method for modeling adherence in individual subjects was extended to the population setting using a Bayesian approach. Four integrated population models for overall adherence, the two-state Markov chain transition parameters, dose-timing deviations, overdosing and persistence were formulated and critically compared. The Markov chain-Monte Carlo algorithm was used for identifying distribution parameters and for simulations. The model was challenged with medication event monitoring system data for 207 hypertension patients. The four Bayesian models demonstrated good mixing and convergence characteristics. The distributions of adherence, dose-timing deviations, overdosing and persistence were markedly non-normal and diverse. The models varied in complexity and the method used to incorporate inter-dependence with the preceding dose in the two-state Markov chain. The model that incorporated a cooperativity term for inter-dependence and a hyperbolic parameterization of the transition matrix probabilities was identified as the preferred model over the alternatives. The simulated probability densities from the model satisfactorily fit the observed probability distributions of adherence, dose-timing deviations, overdosing and persistence parameters in the sample patients. The model also adequately described the median and observed quartiles for these parameters. The Bayesian model for adherence provides a parsimonious, yet integrated, description of adherence in populations. It may find potential applications in clinical trial simulations and pharmacokinetic-pharmacodynamic modeling. PMID:26319548

  2. A Population Model of Integrative Cardiovascular Physiology

    PubMed Central

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

    2013-01-01

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

  3. FUNCTIONAL BIOASSAYS UTILIZING ZOOPLANKTON: A COMPARISON

    EPA Science Inventory

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

  4. Melatonin Signaling Controls Circadian Swimming Behavior in Marine Zooplankton

    PubMed Central

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

    2014-01-01

    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

  5. A one dimensional model of population growth

    NASA Astrophysics Data System (ADS)

    Ribeiro, Fabiano L.; Ribeiro, Kayo N.

    2015-09-01

    In this work, a one dimensional population growth model is proposed. The model, based on the cooperative and competitive individual-individual distance-dependent interaction, allows us to get a full analytical solution. With this analytical approach, it was possible to investigate the dynamics of the population according to some parameters, as intrinsic growth rate, strength of the interaction between individuals, and the distance-dependent interaction. As a consequence of the individuals' interaction, a rich phase diagram to which the population has access was observed. The phases observed are: convergence to carrying capacity, exponential growth, divergence at finite time, and extinction. Moreover, it was also observed that some phases are strictly dependent on the initial condition. For instance, in the cooperative regime with negative intrinsic growth rate, the population can diverge or become extinct according to the initial population size. The phases accessible to the population can be seen as a macroscopic behavior which emerges from the interaction among the individuals (the microscopic level).

  6. Predation by estuarine zooplankton on tintinnid ciliates

    NASA Astrophysics Data System (ADS)

    Robertson, J. Roy

    1983-01-01

    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 μm) and Tintinnopsis tubulosa (length 148 μm). 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 μm) 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 μm 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.

  7. Fitting population models from field data

    USGS Publications Warehouse

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

    2003-01-01

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

  8. Climate warming and the decline of zooplankton in the California current

    SciTech Connect

    Roemmich, D.; McGowan, J.

    1995-03-03

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

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

    SciTech Connect

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

    1980-08-01

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

  10. 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 ...

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

    PubMed Central

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

    2013-01-01

    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

  12. Turbulence and zooplankton production: insights from PROVESS

    NASA Astrophysics Data System (ADS)

    Visser, André W.; Stips, Adolf

    2002-06-01

    Zooplankton are directly influenced by turbulence in both a passive and an active manner. Passively, zooplankton are at the mercy of turbulence in how it affects their vertical mixing, encounter rate, detection abilities and feeding current efficiency. Many zooplankton species, however, are actively able to mitigate the effects of turbulence by modifying their behaviour, e.g. vertical migration, prey switching and habituation to hydromechanical stimuli. Both theoretical treatments of these processes and field observations from the northern North Sea are examined. Field observations show that some copepod species actively migrate to avoid high turbulence levels in surface waters. Furthermore, observations show a negative relationship between turbulence and zooplankton ingestion rates. This supports the paradigm of a dome-shaped response for zooplankton production with environmental turbulence. A theoretical treatment shows that the reaction distance, R, for an ambush-feeding copepod feeding on swimming organisms follows R ∝ ɛ-1/6 where ɛ is the turbulent dissipation rate, a result that shows close agreement with previously reported experimental results.

  13. 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...

  14. Material properties of zooplankton and nekton from the California current

    NASA Astrophysics Data System (ADS)

    Becker, Kaylyn

    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.

  15. Population genetics models of transposable elements.

    PubMed

    Brookfield, J F; Badge, R M

    1997-01-01

    The control of transposable element copy number is of considerable theoretical and empirical interest. Under simple models, copy numbers may increase without limit. Mechanisms that can prevent such an increase include those in which the effect of selection increases with copy number, those in which the rate of transposition decreases with copy number, and those where unlimited increase in copy number is prevented by the consequences of functional heterogeneity in the transposable element family. Finite population sizes may attenuate the power of natural selection to act on transposable element copy number in a number of ways that may be of particular importance in laboratory populations. First, a small host population size will create occasional periods in which the variance between individuals in copy number is diminished, and with it the power of natural selection, even when the expected variance is Poisson. Second, small population sizes will produce high-frequency transposable element sites, systematically reducing the variance in copy number. The consequences will be particularly profound when the selective damage of transposable elements follows from their heterozygosity, as when ectopic exchange limits copy number. PMID:9440281

  16. 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

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

    1981-05-01

    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)

  17. Biomass and estimated production properties of size-fractionated zooplankton in the Yellow Sea, China

    NASA Astrophysics Data System (ADS)

    Huo, Yuanzi; Sun, Song; Zhang, Fang; Wang, Minxiao; Li, Chaolun; Yang, Bo

    2012-06-01

    The size-fractionated zooplankton biomass, taxonomic composition, and production calculated by formulas basing on Ikeda-Motoda's physiological methods were studied on the basis of samples taken from six cruises in the Yellow Sea. Zooplankton was size-fractionated using sieves into ~ 2 mm, 1-2 mm, 0.5-1 mm, 0.25-0.5 mm and 0.16-0.25 mm groups. The results showed that the average zooplankton biomass was 84.03 mg DM m- 3 in May, followed in order by September, June, March, August and December with 42.34, 38.36, 32.37, 27.17 and 21.83 mg DM m- 3, respectively. The contribution of ~ 2 mm, 1-2 mm, 0.5-1 mm, 0.25-0.5 mm and 0.16-0.25 mm groups to the total biomass was in the range of 15.2-27.4%, 13.2-29.4%, 14.7-18.2%, 15.8-22.6% and 16.3-34.2%, respectively, during the investigating period. The biomass of all size groups was all highest in May, and except that the biomass of 0.16-0.25 mm group was lowest in August, the biomass of other size groups was lowest in December. The dominant zooplankton species (or taxa) in each group were similar between six cruises. The estimated zooplankton production was highest in May with 1.97 mg C m- 3 d- 1, and was lowest in December with 0.51 mg C m- 3 d- 1, and was in the range of 0.67-1.44 mg C m- 3 d- 1 in other investigating months. The estimated annual zooplankton production was 0.37 g C m- 3 y- 1. The two smallest groups aggregately comprised 59-84% of the net-zooplankton production in the Yellow Sea. The geographical distribution of size-fractionated zooplankton biomass and production was significantly affected by the complex physical features of the Yellow Sea. When the Yellow Sea Cold Bottom Water appeared from June to September, the biomass and production of zooplankton larger than 1 mm were higher inside the cold water mass area than outside it, while the zooplankton smaller than 1 mm showed contrary results. The higher biomass and production of all zooplankton groups occurred in the southern part of the study area in December due to the intrusion of the Yellow Sea Warm Current. And in March, the higher zooplankton biomass and production, especially for small size zooplankton, occurred at the coastal waters resulting from complex physical properties. Results of the present paper showed the biomass and production properties of size-fractionated zooplankton, which is very important for "parameterization" of food web structure models of the Yellow Sea.

  18. Collection and culture techniques for gelatinous zooplankton.

    PubMed

    Raskoff, Kevin A; Sommer, Freya A; Hamner, William M; Cross, Katrina M

    2003-02-01

    Gelatinous zooplankton are the least understood of all planktonic animal groups. This is partly due to their fragility, which typically precludes the capture of intact specimens with nets or trawls. Specialized tools and techniques have been developed that allow researchers and aquarists to collect intact gelatinous animals at sea and to maintain many of these alive in the laboratory. This paper summarizes the scientific literature on the capture, collection, and culture of gelatinous zooplankton and incorporates many unpublished methods developed at the Monterey Bay Aquarium in the past 15 years. PMID:12588746

  19. Hierarchical spatial capture-recapture models: modeling population density from stratified populations

    USGS Publications Warehouse

    Royle, J. Andrew; Converse, Sarah J.

    2013-01-01

    1. Capture–recapture studies are often conducted on populations that are stratified by space, time or other factors. In this paper, we develop a Bayesian spatial capture–recapture (SCR) modelling framework for stratified populations – when sampling occurs within multiple distinct spatial and temporal strata. 2. We describe a hierarchical model that integrates distinct models for both the spatial encounter history data from capture–recapture sampling, and also for modelling variation in density among strata. We use an implementation of data augmentation to parameterize the model in terms of a latent categorical stratum or group membership variable, which provides a convenient implementation in popular BUGS software packages. 3. We provide an example application to an experimental study involving small-mammal sampling on multiple trapping grids over multiple years, where the main interest is in modelling a treatment effect on population density among the trapping grids. 4. Many capture–recapture studies involve some aspect of spatial or temporal replication that requires some attention to modelling variation among groups or strata. We propose a hierarchical model that allows explicit modelling of group or strata effects. Because the model is formulated for individual encounter histories and is easily implemented in the BUGS language and other free software, it also provides a general framework for modelling individual effects, such as are present in SCR models.

  20. Minimal Model of Plankton Systems Revisited with Spatial Diffusion and Maturation Delay.

    PubMed

    Zhao, Jiantao; Tian, Jianjun Paul; Wei, Junjie

    2016-03-01

    This study revisits the minimal model for a plankton ecosystem proposed by Scheffer with spatial diffusion of plankton and the delay of the maturation period of herbivorous zooplankton. It deepens our understanding of effects of the nutrients and the predation of fish upon zooplankton on the dynamical patterns of the plankton system and also presents new phenomena induced by the delay with spatial diffusion. When the nutrient level is sufficient low, the zooplankton population collapses and the phytoplankton population reaches its carrying capacity. Mathematically, the global stability of the boundary equilibrium is proved. As the nutrient level increases, the system switches to coexistent equilibria or oscillations depending on the maturation period of zooplankton and the predation rate of fish on herbivorous zooplankton. Under an eutrophic condition, there is a unique coexistent homogeneous equilibrium, and the equilibrium density of phytoplankton increases, while the equilibrium density of herbivorous zooplankton decreases as the fish predation rate on herbivorous zooplankton is increasing. The study shows that the system will never collapses under the eutrophic condition unless the fish predation rate approaches infinite. The study also finds a functional bifurcation relation between the delay parameter of the maturation period of herbivorous zooplankton and the fish predation rate on herbivorous zooplankton that, above a critical value of the fish predation rate, the system stays at the coexistent equilibrium, and below that value, the system switches its dynamical patterns among stable and unstable equilibria and oscillations. The oscillations emerge from Hopf bifurcations, and a detailed mathematical analysis about the Hopf bifurcations is carried out to give relevant ecological predications. PMID:26934887

  1. Estimating population trends with a linear model

    USGS Publications Warehouse

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

    2003-01-01

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

  2. Age-dependent models of population growth.

    PubMed

    Ziebur, A D

    1984-12-01

    P. H. Leslie (1945, Biometrika 33, 183-212) (and others) introduced vector-matrix growth difference equations to model populations in which birth and death rates are age-dependent. We develop differential versions of these equations in both the unrestricted growth and logistic cases. We find that the vector logistic equations (difference and differential) are explicitly solvable in terms of solutions of the unrestricted equations, even when vital rates vary with time. These explicit solution formulas make it easy to determine the behavior of solutions as time goes on. PMID:6515584

  3. Sustainability in single-species population models

    PubMed Central

    Quinn, Terrance J.; Collie, Jeremy S.

    2005-01-01

    In this paper, we review the concept of sustainability with regard to a single-species, age-structured fish population with density dependence at some stage of its life history. We trace the development of the view of sustainability through four periods. The classical view of sustainability, prevalent in the 1970s and earlier, developed from deterministic production models, in which equilibrium abundance or biomass is derived as a function of fishing mortality. When there is no fishing mortality, the population equilibrates about its carrying capacity. We show that carrying capacity is the result of reproductive and mortality processes and is not a fixed constant unless these processes are constant. There is usually a fishing mortality, FMSY, which results in MSY, and a higher value, Fext, for which the population is eventually driven to extinction. For each F between 0 and Fext, there is a corresponding sustainable population. From this viewpoint, the primary tool for achieving sustainability is the control of fishing mortality. The neoclassical view of sustainability, developed in the 1980s, involved population models with depensation and stochasticity. This viewpoint is in accord with the perception that a population at a low level is susceptible to collapse or to a lack of rebuilding regardless of fishing. Sustainability occurs in a more restricted range from that in the classical view and includes an abundance threshold. A variety of studies has suggested that fishing mortality should not let a population drop below a threshold at 10–20% of carrying capacity. The modern view of sustainability in the 1990s moves further in the direction of precaution. The fishing mortality limit is the former target of FMSY (or some proxy), and the target fishing mortality is set lower. This viewpoint further reduces the range of permissible fishing mortalities and resultant desired population sizes. The objective has shifted from optimizing long-term catch to preserving spawning biomass and egg production for the future. The use of discount rates in objective functions involving catch is not a suitable alternative to protecting reproductive value. As we move into the post-modern time period, new definitions of sustainability will attempt to incorporate the economic and social aspects of fisheries and/or ecosystem and habitat requirements. These definitions now involve ‘warm and fuzzy’ notions (healthy ecosystems and fishing communities, the needs of future generations, diverse fish communities) and value judgements of desired outcomes. Additional work is needed to make these definitions operational and to specify quantitative objectives to be achieved. In addition, multiple objectives may be incompatible, so trade-offs in what constitutes sustainability must be made. The advances made under the single-species approach should not be abandoned in the post-modern era, but rather enhanced and combined with new approaches in the multi-species and economic realms. PMID:15713594

  4. Population Models for Massive Globular Clusters

    NASA Astrophysics Data System (ADS)

    Lee, Young-Wook; Joo, Seok-Joo; Han, Sang-Il; Na, Chongsam; Lim, Dongwook; Roh, Dong-Goo

    2015-03-01

    Increasing number of massive globular clusters (GCs) in the Milky Way are now turned out to host multiple stellar populations having different heavy element abundances enriched by supernovae. Recent observations have further shown that [CNO/Fe] is also enhanced in metal-rich subpopulations in most of these GCs, including ω Cen and M22 (Marino et al. 2011, 2012). In order to reflect this in our population modeling, we have expanded the parameter space of Y 2 isochrones and horizontal-branch (HB) evolutionary tracks to include the cases of normal and enhanced nitrogen abundances ([N/Fe] = 0.0, 0.8, and 1.6). The observed variations in the total CNO content were reproduced by interpolating these nitrogen enhanced stellar models. Our test simulations with varying N and O abundances show that, once the total CNO sum ([CNO/Fe]) is held constant, both N and O have almost identical effects on the HR diagram (see Fig. 1).

  5. Zooplankton succession in fingerling production ponds

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many pond cultured species require a range of zooplankton species for consumption before they can be weaned onto manufactured feed. The widest variety of plankton species develops when empty ponds are filled and fertilized. Use of organic and inorganic fertilizers facilitates the development of ba...

  6. SENSITIVITY OF ZOOPLANKTON INDICATORS IN REGIONAL MONITORING

    EPA Science Inventory

    This study describes an approach for assessing and selecting ecological indicators for regional monitoring of northeastern US lakes. We analyze the components of variance for indicators of zooplankton richness and abundance in the context of the spatial and temporal sampling des...

  7. ZOOPLANKTON NUTRITIONAL VALUE: NURSERY POND FERTILIZATION EFFECTS

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  8. Bacteria dispersal by hitchhiking on zooplankton.

    PubMed

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

    2010-06-29

    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 x 10(5) x cells x Daphnia(-1) x 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

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

    EPA Science Inventory

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

    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.

  11. Sample variability of zooplankton in the nearshore off Louisiana with consideration of sampling design

    NASA Astrophysics Data System (ADS)

    Park, Chul; Wormuth, John H.; Wolff, Gary A.

    1989-02-01

    Variability in zooplankton samples was examined to identify a proper sampling design for unbiased estimates of zooplankton abundances. Samples were selected in the nearshore about 16 km south of Louisiana during one night and 2 days in October 1985 using a 1 m 2 multiple Opening/Closing net and Environmental Sensing System fitted with 0.333 mm mesh nets. Data obtained from 21 tows of three different tow lengths at mid depth (about 5 m, water depth 10 m) were analysed. There seemed to be different patterns of vertical migration and these vertical migrations were shown to explain about 75% of total sample variability in the study area. These were: usual vertical migration ( Centropages velificatus, Chaetognatha, Eucalanus spp., Phialidium spp., Paracalanus spp. and Temora turbinata), weak vertical migration with elapsed phase (Doliolida A and Oikopleura spp.), and reversed vertical migration ( Acartia tonsa). The relationship between mean abundances and tow distance was weak, but the variance of the abundance estimates showed an exponentially decreasing trend with an increase of tow distance when populations were at their maximum, probably due to vertical migration. From nonlinear regression analyses with the model (variance)= A + B e c(tow distance), the minimum tow distance that would provide a stabilized variance of abundance estimate was determined. It varied among taxa from 43 to 140 m with an average of 80 m. Vertically stratified sampling with a minimum tow distance of about 140 m is suggested as a proper sampling scheme for the unbiased estimation of abundances in a nearshore environment like the sampling site of this study.

  12. Zooplankton Seasonal Abundance of South AmericanSaline Shallow Lakes

    NASA Astrophysics Data System (ADS)

    Echaniz, Santiago Andrés; Vignatti, Alicia María; José de Paggi, Susana; Paggi, Juan César; Pilati, Alberto

    2006-02-01

    The central provinces of Argentina are characterized by the presence of a high number of shallow lakes, located in endorheic basins, many of which have elevated salinities as well as eutrophic or hypereutrophic condition. The zooplankton of four saline shallow lakes of the province of La Pampa was studied on a monthly basis during a 2-year period to determine its temporal and spatial variation.The surface of these shallow lakes (<2.5 m depth) varied between 56.8 and 215.9 ha, and some have from 8.4 to 20.8 g . l-1. The more saline lakes have clear water and the less saline lakes turbid water. Fishes, Jenynsia multidentata , were present in only two lakes during the last two months of the studied period.The zooplankton was composed of 17 taxa of Rotifera, 5 taxa of Cladocera and 4 taxa of Copepoda. The low diversity and the faunistic composition are characteristic of saline environments. Although the studied lakes share 38% of the species, the faunistic similarity was higher between the two least saline lakes. The lowest diversity was found in the two most saline lakes.All four shallow lakes were characterized by their very high zooplankton density, especially in the least saline lakes (<80000 ind . l-1). The abundance is significantly correlated with the water transparency but not with salinity.The zooplankton temporal variation was characterized by the alternation of macro- and microzooplankton, probably regulated by competition and intrazooplanktonic predation. In each lake, the spatial abundance distribution of the macro- and microzooplankton was homogeneous. It was related to the shallow depht of the lakes and their polymictic condition.The Scheffer model on alternative states in shallow lakes acknowledges that it cannot be applied to saline lakes because Daphnia , the main responsible for the clear water state, is not tolerant to high salinity. Our study shows that the most saline lakes, where the halophylic Daphnia menucoensis is abundant, have also the most clear waters. Another difference that we found with regards to the mentioned model is that, in turbid lakes, it could not have had a top-down control on macrozooplankton exerted by fishes because in these lakes fishes were practically absent.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  14. Dynamic analysis of a parasite population model

    NASA Astrophysics Data System (ADS)

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

    2002-03-01

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

  15. [Kinetics of zooplankton in an aquatic continuum: from the Marne River and reservoir to the Seine estuary].

    PubMed

    Akopian, Maa; Garnier, Josette; Pourriot, Roger

    2002-07-01

    A study was carried out within a 700-km river sector, including three types of ecosystems (a reservoir, a river and its estuary) to characterise the major features of zooplankton communities in the Seine Basin. In rivers, zooplankton biomass becomes significant only when the growth rate of the organisms is higher than the dilution rate (4-5th orders rivers, according to River Continuum Concept). Upstream, short residence times favour the development of small species (Rotifers) with low individual body weight and biomass. Conversely, larger species (microcrustaceans) develop more downstream, where increased residence time leads to autochthonous production (Riverine Productivity Model). Such a pattern is greatly modified by human impact. Zooplankton input from the Marne reservoir represents one type of disruption in the general upstream-downstream trend (according to the Serial Discontinuity Concept). This reservoir is a source of microcrustaceans; they rapidly disappear mainly through fish predation, and therefore have little impact on the river phytoplankton. Discontinuities, such as confluences, have a relatively small effect on the stock of zooplankton with regard to the water release from the reservoir, but they persist more downstream, because they have the same lotic origin. A few microhabitats with macrophytes play a small role for this canalised river, but they can modify locally the plankton community structure and composition. As a whole, the flux of zooplankton rises exponentially, whereas discharge increases linearly from upstream (4th order) to downstream (8th order). In the canalised sectors, Dreissena larvae build up an important biomass, adding to that of the zooplankton sensu stricto. Especially abundant in the downstream sector of the Marne and Seine Rivers, the larvae show a widespread colonisation of the benthic substrates by the adult Dreissena. One of the largest mussel colonies in the middle estuary can contribute to a rapid decrease of zooplankton. Estuary ecosystems form a transitional zone between freshwater and seawater, with zooplankton dynamics closely linked to the particular conditions on this part of the river system. PMID:12360849

  16. UV radiation and freshwater zooplankton: damage, protection and recovery

    PubMed Central

    Rautio, Milla; Tartarotti, Barbara

    2011-01-01

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

  17. Modeling populations of rotationally mixed massive stars

    NASA Astrophysics Data System (ADS)

    Brott, I.

    2011-02-01

    Massive stars can be considered as cosmic engines. With their high luminosities, strong stellar winds and violent deaths they drive the evolution of galaxies through-out the history of the universe. Despite the importance of massive stars, their evolution is still poorly understood. Two major issues have plagued evolutionary models of massive stars until today: mixing and mass loss On the main sequence, the effects of mass loss remain limited in the considered mass and metallicity range, this thesis concentrates on the role of mixing in massive stars. This thesis approaches this problem just on the cross road between observations and simulations. The main question: Do evolutionary models of single stars, accounting for the effects of rotation, reproduce the observed properties of real stars. In particular we are interested if the evolutionary models can reproduce the surface abundance changes during the main-sequence phase. To constrain our models we build a population synthesis model for the sample of the VLT-FLAMES Survey of Massive stars, for which star-formation history and rotational velocity distribution are well constrained. We consider the four main regions of the Hunter diagram. Nitrogen un-enriched slow rotators and nitrogen enriched fast rotators that are predicted by theory. Nitrogen enriched slow rotators and nitrogen unenriched fast rotators that are not predicted by our model. We conclude that currently these comparisons are not sufficient to verify the theory of rotational mixing. Physical processes in addition to rotational mixing appear necessary to explain the stars in the later two regions. The chapters of this Thesis have been published in the following Journals: Ch. 2: ``Rotating Massive Main-Sequence Stars I: Grids of Evolutionary Models and Isochrones'', I. Brott, S. E. de Mink, M. Cantiello, N. Langer, A. de Koter, C. J. Evans, I. Hunter, C. Trundle, J.S. Vink submitted to Astronomy & Astrop hysics Ch. 3: ``The VLT-FLAMES Survey of Massive Stars: Rotation and Nitrogen Enrichment as the Key to Understanding Massive Star Evolution'', I.Hunter, I.Brott, D.J. Lennon, N. Langer, C. Trundle, A. de Koter, C.J. Evans and R.S.I. Ryans The Astrophysical Journal, 2008, 676, L29-L32 Ch. 4: ``The VLT-FLAMES Survey of Massive Stars: Constraints on Stellar Evolution from the Chemical Compositions of Rapidly Rotating Galactic and Magellanic Cloud B-type Stars '', I. Hunter, I. Brott, N. Langer, D.J. Lennon, P.L. Dufton, I.D. Howarth R.S.I. Ryan, C. Trundle, C. Evans, A. de Koter and S.J. Smartt Published in Astronomy & Astropysics, 2009, 496, 841- 853 Ch. 5: ``Rotating Massive Main-Sequence Stars II: Simulating a Population of LMC early B-type Stars as a Test of Rotational Mixing '', I. Brott, C. J. Evans, I. Hunter, A. de Koter, N. Langer, P. L. Dufton, M. Cantiello, C. Trundle, D. J. Lennon, S.E. de Mink, S.-C. Yoon, P. Anders submitted to Astronomy & Astrophysics Ch 6: ``The Nature of B Supergiants: Clues From a Steep Drop in Rotation Rates at 22 000 K - The possibility of Bi-stability braking'', Jorick S. Vink, I. Brott, G. Graefener, N. Langer, A. de Koter, D.J. Lennon Astronomy & Astrophysics, 2010, 512, L7

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    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.

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

    NASA Astrophysics Data System (ADS)

    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

    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.

  20. Linking contemporary vegetation models with spatially explicit animal population models

    SciTech Connect

    Holt, R.D.; Pacala, S.W.; Smith, T.W.; Liu, Jianguo

    1995-02-01

    Spatially explicit models for animal populations (SEPMs) necessarily embody assumptions about plant community structure and dynamics. This paper explores the advantages and limitations of directly linking animal SEPMs with models for vegetation dynamics. Such linkages may often be unnecessary. For instance, in research focussed on questions with short time horizons, the spatial patterning of vegetation can be reasonably approximated as a fixed landscape templet for animal population dynamics. But if one needs to consider longer time scales (e.g., decades to centuries), landscapes will be dynamic. Models of vegetation dynamics provide useful tools for predicting landscape dynamics. We outline the sorts of output from vegetation models that might be useful in animal SEPMs. We discuss as a concrete example recent forest simulators, which predict with reasonable accuracy some variables (e.g., tree species composition), but which, to date, are quite poor for others (e.g., seed production). Moreover, because vegetation models target a restricted range of temporal and spatial scales, they may be more useful for certain consumer groups than for others. Despite these cautionary observations, we believe that the time is ripe for fruitful linkages between models of vegetation dynamics and animal SEPMs. 61 refs., 1 fig.

  1. Power-plant-related estuarine zooplankton studies

    SciTech Connect

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

    1981-01-01

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

  2. A hybrid numerical-experimental study of fluid transport by migrating zooplankton aggregations

    NASA Astrophysics Data System (ADS)

    Martinez, Monica; Dabiri, John; Nawroth, Janna; Gemmell, Brad; Collins, Samantha

    2014-11-01

    Zooplankton aggregations that undergo diel vertical migrations have been hypothesized to play an important role in local nutrient transport and global ocean dynamics. The degree of the contributions of these naturally occurring events ultimately relies on how efficiently fluid is transported and eventually mixed within the water column. By implementing solutions to the Stokes equations, numerical models have successfully captured the time-averaged far-field flow of self-propelled swimmers. However, discrepancies between numerical fluid transport estimates and field measurements of individual jellyfish suggest the need to include near-field effects to assess the impact of biomixing in oceanic processes. Here, we bypass the inherent difficulty of modeling the unsteady flow of active swimmers while including near-field effects by integrating experimental velocity data of zooplankton into our numerical model. Fluid transport is investigated by tracking a sheet of artificial fluid particles during vertical motion of zooplankton. Collective effects are addressed by studying different swimmer configurations within an aggregation from the gathered data for a single swimmer. Moreover, the dependence of animal swimming mode is estimated by using data for different species of zooplankton.

  3. Promotion of harmful algal blooms by zooplankton predatory activity

    PubMed Central

    Mitra, Aditee; Flynn, Kevin J

    2006-01-01

    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

  4. Landscape Modeling of Lygus hesperus Populations.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Lygus is a key pest in several of the 200 crops grown in the geographically distinct San Joaquin Valley. Spring weather patterns drive population build-up on host-plants. Habitat maps were created from survey sites in cropping regions of Kern County, CA. Population simulations were used to predict a...

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

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

    PubMed Central

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

    2003-01-01

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

  7. Policy Applications of Population Models: A Comparative Review

    ERIC Educational Resources Information Center

    Srikantan, K. S.; Blumstein, Alfred

    1977-01-01

    From various models used in population studies, 40 typical ones were chosen and classified by policy relevant categories. Seven essential requirements of a policy model were specified and the 40 models were evaluated by these policy features. (Author)

  8. Bio-physical coupling in the formation of zooplankton and fish aggregations over abrupt topographies

    NASA Astrophysics Data System (ADS)

    Genin, Amatzia

    2004-09-01

    Aggregations of zooplankton, micronekton and fish are frequently observed above seamounts, canyons and shelf breaks. The aggregations are produced by five different mechanisms, all driven by ocean currents. Upwelling is frequently generated when ambient currents impinge on abrupt topographies. Nevertheless, upwelling enhances local production of zooplankton and fish only over large topographies such as shelf breaks, where the residence time of the upwelled water is sufficiently long to allow enrichment in primary production to propagate up the food web and augment the growth of resident animals. Daily accumulations occur over topographies at shallow and intermediate depths when the topography blocks the morning descent of migrating zooplankton. This mechanism is common over seamounts. Two other mechanisms are driven by behavioral response to vertical currents when zooplankton swims vertically in order to maintain depth: accumulations by depth retention against upwelling are common at depths to which migrating zooplankton descend during the day, while depth retention against downwelling seems to operate only in the upper water column (e.g., along topographically generated fronts). The fifth mechanism is driven by the amplification of currents over abrupt topographies. Strong currents enhance population growth of resident animals by augmenting fluxes of suspended food. A feed-rest hypothesis is proposed to explain how site-attached planktivorous fish can benefit from strong currents at sites with ample quiescence shelters in which the fish rest during non-feeding intervals. Four of the above mechanisms generate "trophic focusing", a process by which prey from immense volumes of flowing water is accumulated (or trapped) in a relatively small confined area. The ensuing subsidy of prey propagates up the food web, supporting aggregations of higher predators, such as fish, marine mammals and fishermen. Abrupt topographies can have an important role in determining trophic interactions in the marine realm.

  9. 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...

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

    PubMed

    Lawler, Joshua J; Schumaker, Nathan H

    2004-06-01

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

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

    PubMed

    Kiørboe, Thomas

    2011-05-01

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

  12. 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...

  13. Population model for Alaska Peninsula sea otters. Final report

    SciTech Connect

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

    1988-12-31

    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.

  14. Modeling of Biological Populations Using Fuzzy Differential Equations

    NASA Astrophysics Data System (ADS)

    Ahmad, M. Z.; Hasan, M. K.

    This paper explores the application of fuzzy differential equations in modeling of prey and predator populations. A new model, referred to as fuzzy predator-prey model is introduced. This model is then solved numerically by means of a fuzzy Euler method. Some numerical results are presented in order to show the evolution of the prey and predator populations over time. Finally, the stability of the new fuzzy model is studied and shown graphically in the fuzzy phase plane.

  15. Estimating birth and death rates of zooplankton

    SciTech Connect

    Taylor, B.E.; Slatkin, M.

    1981-01-01

    Two estimates of the birth rate using an egg ratio are derived from a three-stage (eggs, juveniles, and adults) model for an exponentially growing population, and the sensitivity of these estimates to time and age-dependence of the birth and death rates and to measurement errors is explored. Tests to determine whether a population violates the assumptions of the model are suggested, and birth rate estimates which partially compensate for some departures from the model are proposed. Other methods for estimating birth and death rates based on this type of model are reviewed. Four birth rate estimates are compared using data for a population of Daphnia pulicaria, and recommendations on the use of birth and death rates based on the egg ratio are made.

  16. Population modelling to compare chronic external radiotoxicity between individual and population endpoints in four taxonomic groups.

    PubMed

    Alonzo, Frédéric; Hertel-Aas, Turid; Real, Almudena; Lance, Emilie; Garcia-Sanchez, Laurent; Bradshaw, Clare; Vives I Batlle, Jordi; Oughton, Deborah H; Garnier-Laplace, Jacqueline

    2016-02-01

    In this study, we modelled population responses to chronic external gamma radiation in 12 laboratory species (including aquatic and soil invertebrates, fish and terrestrial mammals). Our aim was to compare radiosensitivity between individual and population endpoints and to examine how internationally proposed benchmarks for environmental radioprotection protected species against various risks at the population level. To do so, we used population matrix models, combining life history and chronic radiotoxicity data (derived from laboratory experiments and described in the literature and the FREDERICA database) to simulate changes in population endpoints (net reproductive rate R0, asymptotic population growth rate λ, equilibrium population size Neq) for a range of dose rates. Elasticity analyses of models showed that population responses differed depending on the affected individual endpoint (juvenile or adult survival, delay in maturity or reduction in fecundity), the considered population endpoint (R0, λ or Neq) and the life history of the studied species. Among population endpoints, net reproductive rate R0 showed the lowest EDR10 (effective dose rate inducing 10% effect) in all species, with values ranging from 26 μGy h(-1) in the mouse Mus musculus to 38,000 μGy h(-1) in the fish Oryzias latipes. For several species, EDR10 for population endpoints were lower than the lowest EDR10 for individual endpoints. Various population level risks, differing in severity for the population, were investigated. Population extinction (predicted when radiation effects caused population growth rate λ to decrease below 1, indicating that no population growth in the long term) was predicted for dose rates ranging from 2700 μGy h(-1) in fish to 12,000 μGy h(-1) in soil invertebrates. A milder risk, that population growth rate λ will be reduced by 10% of the reduction causing extinction, was predicted for dose rates ranging from 24 μGy h(-1) in mammals to 1800 μGy h(-1) in soil invertebrates. These predictions suggested that proposed reference benchmarks from the literature for different taxonomic groups protected all simulated species against population extinction. A generic reference benchmark of 10 μGy h(-1) protected all simulated species against 10% of the effect causing population extinction. Finally, a risk of pseudo-extinction was predicted from 2.0 μGy h(-1) in mammals to 970 μGy h(-1) in soil invertebrates, representing a slight but statistically significant population decline, the importance of which remains to be evaluated in natural settings. PMID:26630040

  17. Impacts of zooplankton composition and algal enrichment on the accumulation of mercury in an experimental freshwater food web.

    PubMed

    Pickhardt, Paul C; Folt, Carol L; Chen, Celia Y; Klaue, Bjoern; Blum, Joel D

    2005-03-01

    There is a well documented accumulation of mercury in fish to concentrations of concern for human consumption. Variation in fish Hg burden between lakes is often high and may result from differences in Hg transfer through lower levels of the food web where mercury is bioconcentrated to phytoplankton and transferred to herbivorous zooplankton. Prior research derived patterns of mercury accumulation in freshwater invertebrates from field collected animals. This study provides results from controlled mesocosm experiments comparing the effects of zooplankton composition, algal abundance, and the chemical speciation of mercury on the ability of zooplankton to accumulate mercury from phytoplankton and transfer that mercury to planktivores. Experiments were conducted in 550-L mesocosms across a gradient of algal densities manipulated by inorganic nutrient additions. Enriched, stable isotopes of organic (CH3(200HgCl)) and inorganic (201HgCl2) mercury were added to mesocosms and their concentrations measured in water, seston, and three common zooplankton species. After 2 weeks, monomethylmercury (MMHg) concentrations were two to three times lower in the two copepod species, Leptodiaptomus minutus and Mesocyclops edax than in the cladoceran, Daphnia mendotae. All three zooplankton species had higher MMHg concentrations in mesocosms with low versus high initial algal abundance. However, despite higher concentrations of inorganic mercury (HgI) in seston from low nutrient mesocosms, there were no significant differences in the HgI accumulated by zooplankton across nutrient treatments. Bioaccumulation factors for MMHg in the plankton were similar to those calculated for plankton in natural lakes and a four-compartment (aqueous, seston, macrozooplankton, and periphyton/sediments) mass balance model after 21 days accounted for approximately 18% of the CH3(200Hg) and approximately 33% of the 201Hg added. Results from our experiments corroborate results from field studies and suggest the importance of particular zooplankton herbivores (e.g., Daphnia) in the transfer of Hg to higher trophic levels in aquatic food webs. PMID:15740761

  18. Survival models for harvest management of mourning dove populations

    USGS Publications Warehouse

    Otis, D.L.

    2002-01-01

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

  19. Limnetic crustacean zooplankton of Lake Oahe, May-October 1969

    USGS Publications Warehouse

    Selgeby, James H.

    1974-01-01

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

  20. COMPARISONS OF ZOOPLANKTON COMMUNITY SIZE STRUCTURE IN THE GREAT LAKES

    EPA Science Inventory

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

  1. 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...

  2. 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...

  3. Thermal stress studies on selected zooplankton species and an isopod

    SciTech Connect

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

    1980-06-01

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

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

    NASA Astrophysics Data System (ADS)

    Lehodey, Patrick; Senina, Inna; Murtugudde, Raghu

    2008-09-01

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

  5. PC BEEPOP - A PERSONAL COMPUTER HONEY BEE POPULATION DYNAMICS MODEL

    EPA Science Inventory

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

  6. 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...

  7. Functional bioassays utilizing zooplankton: A comparison

    SciTech Connect

    McNaught, D.C.

    1989-01-01

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

  8. MODELING APPROACHES TO POPULATION-LEVEL RISK AESSESSMENT

    EPA Science Inventory

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

  9. Effects of a synthetic oil on zooplankton community structure

    SciTech Connect

    Hook, L.A.

    1988-01-01

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

  10. Spatio-temporal variability of the North Sea cod recruitment in relation to temperature and zooplankton.

    PubMed

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

    2014-01-01

    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

  11. Population models for passerine birds: structure, parameterization, and analysis

    USGS Publications Warehouse

    Noon, B.R.; Sauer, J.R.

    1992-01-01

    Population models have great potential as management tools, as they use infonnation about the life history of a species to summarize estimates of fecundity and survival into a description of population change. Models provide a framework for projecting future populations, determining the effects of management decisions on future population dynamics, evaluating extinction probabilities, and addressing a variety of questions of ecological and evolutionary interest. Even when insufficient information exists to allow complete identification of the model, the modelling procedure is useful because it forces the investigator to consider the life history of the species when determining what parameters should be estimated from field studies and provides a context for evaluating the relative importance of demographic parameters. Models have been little used in the study of the population dynamics of passerine birds because of: (1) widespread misunderstandings of the model structures and parameterizations, (2) a lack of knowledge of life histories of many species, (3) difficulties in obtaining statistically reliable estimates of demographic parameters for most passerine species, and (4) confusion about functional relationships among demographic parameters. As a result, studies of passerine demography are often designed inappropriately and fail to provide essential data. We review appropriate models for passerine bird populations and illustrate their possible uses in evaluating the effects of management or other environmental influences on population dynamics. We identify environmental influences on population dynamics. We identify parameters that must be estimated from field data, briefly review existing statistical methods for obtaining valid estimates, and evaluate the present status of knowledge of these parameters.

  12. Accommodating environmental variation in population models: metaphysiological biomass loss accounting.

    PubMed

    Owen-Smith, Norman

    2011-07-01

    1. There is a pressing need for population models that can reliably predict responses to changing environmental conditions and diagnose the causes of variation in abundance in space as well as through time. In this 'how to' article, it is outlined how standard population models can be modified to accommodate environmental variation in a heuristically conducive way. This approach is based on metaphysiological modelling concepts linking populations within food web contexts and underlying behaviour governing resource selection. Using population biomass as the currency, population changes can be considered at fine temporal scales taking into account seasonal variation. Density feedbacks are generated through the seasonal depression of resources even in the absence of interference competition. 2. Examples described include (i) metaphysiological modifications of Lotka-Volterra equations for coupled consumer-resource dynamics, accommodating seasonal variation in resource quality as well as availability, resource-dependent mortality and additive predation, (ii) spatial variation in habitat suitability evident from the population abundance attained, taking into account resource heterogeneity and consumer choice using empirical data, (iii) accommodating population structure through the variable sensitivity of life-history stages to resource deficiencies, affecting susceptibility to oscillatory dynamics and (iv) expansion of density-dependent equations to accommodate various biomass losses reducing population growth rate below its potential, including reductions in reproductive outputs. Supporting computational code and parameter values are provided. 3. The essential features of metaphysiological population models include (i) the biomass currency enabling within-year dynamics to be represented appropriately, (ii) distinguishing various processes reducing population growth below its potential, (iii) structural consistency in the representation of interacting populations and (iv) capacity to accommodate environmental variation in space as well as through time. Biomass dynamics provide a common currency linking behavioural, population and food web ecology. 4. Metaphysiological biomass loss accounting provides a conceptual framework more conducive for projecting and interpreting the population consequences of climatic shifts and human transformations of habitats than standard modelling approaches. PMID:21644974

  13. Analyzing the trophic link between the mesopelagic microbial loop and zooplankton from observed depth profiles of bacteria and protozoa

    NASA Astrophysics Data System (ADS)

    Tanaka, T.; Rassoulzadegan, F.; Thingstad, T. F.

    It is widely recognized that organic carbon exported to the ocean aphotic layer is significantly consumed by heterotrophic organisms such as bacteria and zooplankton in the mesopelagic layer. However, very little is known for the trophic link between bacteria and zooplankton or the function of the microbial loop in this layer. In the northwestern Mediterranean, recent studies have shown that viruses, bacteria, heterotrophic nanoflagellates, and ciliates distribute down to 2000 m with group-specific depth-dependent decreases, and that bacterial production decreases with depth down to 1000 m. Here we show that such data can be analyzed using a simple steady-state food chain model to quantify the carbon flow from bacteria to zooplankton over the mesopelagic layer. The model indicates that bacterial mortality by viruses is similar to or 1.5 times greater than that by heterotrophic nanoflagellates, and that heterotrophic nanoflagellates transfer little of bacterial production to higher trophic levels.

  14. A general consumer-resource population model

    USGS Publications Warehouse

    Lafferty, Kevin D.; DeLeo, Giulio; Briggs, Cheryl J.; Dobson, Andrew P.; Gross, Thilo; Kuris, Armand M.

    2015-01-01

    Food-web dynamics arise from predator-prey, parasite-host, and herbivore-plant interactions. Models for such interactions include up to three consumer activity states (questing, attacking, consuming) and up to four resource response states (susceptible, exposed, ingested, resistant). Articulating these states into a general model allows for dissecting, comparing, and deriving consumer-resource models. We specify this general model for 11 generic consumer strategies that group mathematically into predators, parasites, and micropredators and then derive conditions for consumer success, including a universal saturating functional response. We further show how to use this framework to create simple models with a common mathematical lineage and transparent assumptions. Underlying assumptions, missing elements, and composite parameters are revealed when classic consumer-resource models are derived from the general model.

  15. IBSEM: An Individual-Based Atlantic Salmon Population Model

    PubMed Central

    Castellani, Marco; Heino, Mikko; Gilbey, John; Araki, Hitoshi; Svåsand, Terje; Glover, Kevin A.

    2015-01-01

    Ecology and genetics can influence the fate of individuals and populations in multiple ways. However, to date, few studies consider them when modelling the evolutionary trajectory of populations faced with admixture with non-local populations. For the Atlantic salmon, a model incorporating these elements is urgently needed because many populations are challenged with gene-flow from non-local and domesticated conspecifics. We developed an Individual-Based Salmon Eco-genetic Model (IBSEM) to simulate the demographic and population genetic change of an Atlantic salmon population through its entire life-cycle. Processes such as growth, mortality, and maturation are simulated through stochastic procedures, which take into account environmental variables as well as the genotype of the individuals. IBSEM is based upon detailed empirical data from salmon biology, and parameterized to reproduce the environmental conditions and the characteristics of a wild population inhabiting a Norwegian river. Simulations demonstrated that the model consistently and reliably reproduces the characteristics of the population. Moreover, in absence of farmed escapees, the modelled populations reach an evolutionary equilibrium that is similar to our definition of a ‘wild’ genotype. We assessed the sensitivity of the model in the face of assumptions made on the fitness differences between farm and wild salmon, and evaluated the role of straying as a buffering mechanism against the intrusion of farm genes into wild populations. These results demonstrate that IBSEM is able to capture the evolutionary forces shaping the life history of wild salmon and is therefore able to model the response of populations under environmental and genetic stressors. PMID:26383256

  16. IBSEM: An Individual-Based Atlantic Salmon Population Model.

    PubMed

    Castellani, Marco; Heino, Mikko; Gilbey, John; Araki, Hitoshi; Svåsand, Terje; Glover, Kevin A

    2015-01-01

    Ecology and genetics can influence the fate of individuals and populations in multiple ways. However, to date, few studies consider them when modelling the evolutionary trajectory of populations faced with admixture with non-local populations. For the Atlantic salmon, a model incorporating these elements is urgently needed because many populations are challenged with gene-flow from non-local and domesticated conspecifics. We developed an Individual-Based Salmon Eco-genetic Model (IBSEM) to simulate the demographic and population genetic change of an Atlantic salmon population through its entire life-cycle. Processes such as growth, mortality, and maturation are simulated through stochastic procedures, which take into account environmental variables as well as the genotype of the individuals. IBSEM is based upon detailed empirical data from salmon biology, and parameterized to reproduce the environmental conditions and the characteristics of a wild population inhabiting a Norwegian river. Simulations demonstrated that the model consistently and reliably reproduces the characteristics of the population. Moreover, in absence of farmed escapees, the modelled populations reach an evolutionary equilibrium that is similar to our definition of a 'wild' genotype. We assessed the sensitivity of the model in the face of assumptions made on the fitness differences between farm and wild salmon, and evaluated the role of straying as a buffering mechanism against the intrusion of farm genes into wild populations. These results demonstrate that IBSEM is able to capture the evolutionary forces shaping the life history of wild salmon and is therefore able to model the response of populations under environmental and genetic stressors. PMID:26383256

  17. An open-population hierarchical distance sampling model

    USGS Publications Warehouse

    Sollmann, Rachel; Beth Gardner; Richard B Chandler; Royle, J. Andrew; T Scott Sillett

    2015-01-01

    Modeling population dynamics while accounting for imperfect detection is essential to monitoring programs. Distance sampling allows estimating population size while accounting for imperfect detection, but existing methods do not allow for direct estimation of demographic parameters. We develop a model that uses temporal correlation in abundance arising from underlying population dynamics to estimate demographic parameters from repeated distance sampling surveys. Using a simulation study motivated by designing a monitoring program for island scrub-jays (Aphelocoma insularis), we investigated the power of this model to detect population trends. We generated temporally autocorrelated abundance and distance sampling data over six surveys, using population rates of change of 0.95 and 0.90. We fit the data generating Markovian model and a mis-specified model with a log-linear time effect on abundance, and derived post hoc trend estimates from a model estimating abundance for each survey separately. We performed these analyses for varying number of survey points. Power to detect population changes was consistently greater under the Markov model than under the alternatives, particularly for reduced numbers of survey points. The model can readily be extended to more complex demographic processes than considered in our simulations. This novel framework can be widely adopted for wildlife population monitoring.

  18. Modelling production per unit of food consumed in fish populations.

    PubMed

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

    2015-01-21

    The ratio of production-to-consumption (ρ) 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 ρ 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 ρ 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 (ρ) in which production and consumption are modelled simultaneously to produce a population estimator of ρ. 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 ρ 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 ρ was evaluated using a resampling approach. Simulation showed that cohort and population models produce different estimates for ρ 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 ρ 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

  19. A quantitative model of honey bee colony population dynamics.

    PubMed

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

    2011-01-01

    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

  20. A Quantitative Model of Honey Bee Colony Population Dynamics

    PubMed Central

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

    2011-01-01

    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

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

    PubMed

    Mickens, Ronald E

    2007-10-01

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

  2. Connecting micro dynamics and population distributions in system dynamics models

    PubMed Central

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

    2014-01-01

    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. PMID:25620842

  3. Models of plant populations and communities

    SciTech Connect

    Huston, M.

    1990-01-01

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

  4. A population growth model forced by random, episodic disturbances

    NASA Astrophysics Data System (ADS)

    Peckham, S. D.

    2011-12-01

    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, λ , and μ = 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.

  5. Augmenting superpopulation capture-recapture models with population assignment data

    USGS Publications Warehouse

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

    2011-01-01

    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.

  6. Augmenting superpopulation capture-recapture models with population assignment data.

    PubMed

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

    2011-09-01

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

  7. Modeling Radicalization Phenomena in Heterogeneous Populations

    PubMed Central

    2016-01-01

    The phenomenon of radicalization is investigated within a mixed population composed of core and sensitive subpopulations. The latest includes first to third generation immigrants. Respective ways of life may be partially incompatible. In case of a conflict core agents behave as inflexible about the issue. In contrast, sensitive agents can decide either to live peacefully adjusting their way of life to the core one, or to oppose it with eventually joining violent activities. The interplay dynamics between peaceful and opponent sensitive agents is driven by pairwise interactions. These interactions occur both within the sensitive population and by mixing with core agents. The update process is monitored using a Lotka-Volterra-like Ordinary Differential Equation. Given an initial tiny minority of opponents that coexist with both inflexible and peaceful agents, we investigate implications on the emergence of radicalization. Opponents try to turn peaceful agents to opponents driving radicalization. However, inflexible core agents may step in to bring back opponents to a peaceful choice thus weakening the phenomenon. The required minimum individual core involvement to actually curb radicalization is calculated. It is found to be a function of both the majority or minority status of the sensitive subpopulation with respect to the core subpopulation and the degree of activeness of opponents. The results highlight the instrumental role core agents can have to hinder radicalization within the sensitive subpopulation. Some hints are outlined to favor novel public policies towards social integration. PMID:27166677

  8. Spatially explicit population models: Current forms and future uses

    SciTech Connect

    Dunning, J.B. Jr.; Stewart, D.J.; Danielson, B.J.; Noon, B.R.; Root, T.L.; Lamberson, R.H.; Stevens, E.E.

    1995-02-01

    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.

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

    SciTech Connect

    Paffenhoefer, G.A.

    1989-02-07

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

  10. Seasonal and interannual changes in zooplankton community in the coastal zone of the North-Eastern Black Sea.

    NASA Astrophysics Data System (ADS)

    Nikishina, A. B.; Arashkevich, E. G.; Louppova, N. E.; Soloviev, K. A.

    2009-04-01

    The phenological response of zooplankton community is a result of simultaneous effect of several factors: feeding conditions, predation abundance, periods of reproduction of common species and hydrodynamic regime. The Black sea ecosystem is one of the best studied in the world, otherwise there is still some illegibility about ecosystem functioning and especially about environmental factors influence on zooplankton dynamics. For the last twenty years pelagic system of the Black Sea has changed dramatically. The invasion of ctenophore Mnemiopsis leidyi in the middle of eighties caused significant decrease in zooplankton biomass. It also altered plankton structure and shifted periods of mass reproduction of the abundant species and biomass maximums. For instance, before the invasion of Mnemiopsis the maximum of zooplankton biomass was observed in autumn (data by A. Pasternak, 1983), and after that the maximum moved to the spring (data by V.S. Khoroshilov, 1999). The incursion of ctenophore Beroe ovata feeding on Mnemiopsis in the nineties has led to the enhancement of zooplankton community. Although the detailed analysis of seasonal zooplankton dynamics wasn't performed in the recent years. The object of our research was to study seasonal and interannual changes in zooplankton community in the coastal area of the North-Eastern Black Sea. Analysis of interannual, seasonal and spatial changes in zooplankton distribution, abundance and species composition along with age structure of dominant populations were performed based on investigations during 2005-2008 years in the North-Eastern Black Sea. Plankton samples were obtained monthly since June 2005 till December 2008. Plankton was collected at three stations at depths 25m, 50m and 500-1000m along the transect from the Blue Bay to the open sea. Sampling of gelatinous animals was conducted in parallel to the zooplankton sampling. Simultaneously with plankton sampling CTD data were obtained. The feeding conditions were obtained using SSC satellite data. For studying vertical distribution of zooplankton depth stratified samples were collected in different seasons. To evaluate seasonal variations in reproduction and offspring development of dominant mesozooplankton populations, we analyzed age structure of five species: four herbivorous copepods - Acartia clausi, Pseudocalanus elongatus, Paracalanus parvus and Calanus euxinus, and carnivorous chaethognaths Parasagitta setosa. Periods of mass reproduction varied in different years. The possible reason for this variation is the effect of climate change and top-predators on seasonal shift in zooplankton dynamics. Whereas timing of reproduction is related to life strategy of species, an intensity of reproduction and success of new generations depend on food supply. The impact of food conditions on abundance and age structure of herbivores was studied in the different seasons. Vertical distribution of different species also altered from year to year. Thus, in "warm" July 2007 (sea surface temperature 27°C) most of the Calanus euxinus population concentrated in the deeper layers than in "cold" July 2005 (sea surface temperature 22°C).

  11. Population extinction in an inhomogeneous host-pathogen model

    NASA Astrophysics Data System (ADS)

    Bagarti, Trilochan

    2016-01-01

    We study inhomogeneous host-pathogen dynamics to model the global amphibian population extinction in a lake basin system. The lake basin system is modeled as quenched disorder. In this model we show that once the pathogen arrives at the lake basin it spreads from one lake to another, eventually spreading to the entire lake basin system in a wave like pattern. The extinction time has been found to depend on the steady state host population and pathogen growth rate. Linear estimate of the extinction time is computed. The steady state host population shows a threshold behavior in the interaction strength for a given growth rate.

  12. Characterization of Lake Michigan coastal lakes using zooplankton assemblages

    USGS Publications Warehouse

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

    2004-01-01

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

  13. A General Mechanistic Model for Admixture Histories of Hybrid Populations

    PubMed Central

    Verdu, Paul; Rosenberg, Noah A.

    2011-01-01

    Admixed populations have been used for inferring migrations, detecting natural selection, and finding disease genes. These applications often use a simple statistical model of admixture rather than a modeling perspective that incorporates a more realistic history of the admixture process. Here, we develop a general model of admixture that mechanistically accounts for complex historical admixture processes. We consider two source populations contributing to the ancestry of a hybrid population, potentially with variable contributions across generations. For a random individual in the hybrid population at a given point in time, we study the fraction of genetic admixture originating from a specific one of the source populations by computing its moments as functions of time and of introgression parameters. We show that very different admixture processes can produce identical mean admixture proportions, but that such processes produce different values for the variance of the admixture proportion. When introgression parameters from each source population are constant over time, the long-term limit of the expectation of the admixture proportion depends only on the ratio of the introgression parameters. The variance of admixture decreases quickly over time after the source populations stop contributing to the hybrid population, but remains substantial when the contributions are ongoing. Our approach will facilitate the understanding of admixture mechanisms, illustrating how the moments of the distribution of admixture proportions can be informative about the historical admixture processes contributing to the genetic diversity of hybrid populations. PMID:21968194

  14. Stimulus-dependent Maximum Entropy Models of Neural Population Codes

    PubMed Central

    Segev, Ronen; Schneidman, Elad

    2013-01-01

    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

  15. Surrogate population models for large-scale neural simulations.

    PubMed

    Tripp, Bryan P

    2015-06-01

    Because different parts of the brain have rich interconnections, it is not possible to model small parts realistically in isolation. However, it is also impractical to simulate large neural systems in detail. This article outlines a new approach to multiscale modeling of neural systems that involves constructing efficient surrogate models of populations. Given a population of neuron models with correlated activity and with specific, nonrandom connections, a surrogate model is constructed in order to approximate the aggregate outputs of the population. The surrogate model requires less computation than the neural model, but it has a clear and specific relationship with the neural model. For example, approximate spike rasters for specific neurons can be derived from a simulation of the surrogate model. This article deals specifically with neural engineering framework (NEF) circuits of leaky-integrate-and-fire point neurons. Weighted sums of spikes are modeled by interpolating over latent variables in the population activity, and linear filters operate on gaussian random variables to approximate spike-related fluctuations. It is found that the surrogate models can often closely approximate network behavior with orders-of-magnitude reduction in computational demands, although there are certain systematic differences between the spiking and surrogate models. Since individual spikes are not modeled, some simulations can be performed with much longer steps sizes (e.g., 20 ms). Possible extensions to non-NEF networks and to more complex neuron models are discussed. PMID:25774544

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

    PubMed

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

    2014-04-01

    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

  17. Zooplankton functional groups on the continental shelf of the yellow sea

    NASA Astrophysics Data System (ADS)

    Sun, Song; Huo, Yuanzi; Yang, Bo

    2010-06-01

    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.

  18. Modeling seasonal interactions in the population dynamics of migratory birds

    USGS Publications Warehouse

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

    2005-01-01

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

  19. A Role for M-Matrices in Modelling Population Growth

    ERIC Educational Resources Information Center

    James, Glyn; Rumchev, Ventsi

    2006-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    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.

  1. Changes in the nearshore and offshore zooplankton communities in Lake Ontario: 1981-88

    USGS Publications Warehouse

    Johannsson, Ora E.; Mills, Edward L.; O'Gorman, Robert

    1991-01-01

    We examined trends and factors influencing changes in nearshore and offshore zooplankton abundance and composition in Lake Ontario between 1981 and 1988. In the nearshore (southshore and eastern basin), zooplankton abundance decreased and shifts occurred in the relative abundances of Bosmina longirostris and Daphnia retrocurva (eastern basin) and Daphnia retrocurva and Daphnia galeata mendotae (southshore). These changes could have resulted from increased vertebrate predation or reduced food resources which intensified the effects of predation. In the offshore, the first appearance (FA) of the larger, less common cladoceran species occurred earlier in the season as of 1985. FA was correlated with cumulative epilimnetic temperature (CET) and the catch per unit effort (CPUE) of alewife (Alosa pseudoharengus) a?Y165 mm caught in U.S. waters in the spring. In 1987, when CET was high and CPUE of alewife a?Y165 mm was low, large populations of these cladocerans developed in June and July. Bythotrephes cederstroemi, a recent invader in the Great Lakes, was abundant only in 1987 when the CPUE of alewife was lowest. Changes in zooplankton abundance, development, and composition along the nearshore-offshore gradient reflected effects of temperature, habitat, and planktivory on the community.

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

    PubMed

    Roy, Shovonlal

    2008-10-01

    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

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

    SciTech Connect

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

    1984-08-01

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

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

    SciTech Connect

    Starkel, W.M.

    1985-01-01

    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.

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

    PubMed

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

    2014-04-01

    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 (μ-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

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

    NASA Astrophysics Data System (ADS)

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

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

  7. Effect of various intake designs on zooplankton entrainment

    SciTech Connect

    Dycus, D.L.

    1983-03-01

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

  8. Zooplankton patch dynamics: daily gap formation over abrupt topography

    NASA Astrophysics Data System (ADS)

    Genin, Amatzia; Greene, Charles; Haury, Loren; Wiebe, Peter; Gal, Gideon; Kaartvedt, Stein; Meir, Eli; Fey, Connie; Dawson, Jim

    1994-05-01

    Net tow and acoustic surveys of zooplankton distributions were made over and around Sixtymile Bank (110 km southwest of San Diego, California). Gaps devoid of vertically migrating zooplankton were formed every evening above the summit of the bank. Interactions between the migrating animals, their predators, physical advection and the local topography appear to determine the gap formation and dynamics. Gaps were transported downstream during the night and appeared to disintegrate slowly through vertical swimming behavior, current shear and mixing processes. Patch dynamics following gap formation, mediated by both ocean currents and animal behavior, should augment the spatial heterogeneity of zooplankton and affect marine food webs in areas where abrupt topography features are common.

  9. MASSCLEAN Multiple Stellar Populations Models of Stellar Clusters

    NASA Astrophysics Data System (ADS)

    Popescu, Bogdan; Hanson, Margaret M.

    2015-08-01

    The age and mass of unresolved or partially resolved stellar clusters can only be estimated using their integrated-light properties of magnitude and colors. Traditional Simple Stellar Population (SSP) models interpret these integrated properties assuming an infinite mass limit. This can lead to catastrophic failures in both age and mass determination when applied to real stellar clusters, particularly with total mass below 104 Msun. New, more sophisticated mass-dependent SSP models provide more accurate age and mass estimates, in better agreement with cluster age determinations using deep photometry Color-Magnitude Diagrams (CMD). But even these modern, mass-dependent SSP models can fail to estimate age and mass if the cluster contains a second stellar population. Our newest mass-dependent Multiple Stellar Populations (MSP) models show the influence of a second population of stars on the integrated light of these complex stellar clusters and their age estimates shows stronger agreement with CMD-derived stellar cluster ages.

  10. Zooplankton may serve as transmission vectors for viruses infecting algal blooms in the ocean.

    PubMed

    Frada, Miguel José; Schatz, Daniella; Farstey, Viviana; Ossolinski, Justin E; Sabanay, Helena; Ben-Dor, Shifra; Koren, Ilan; Vardi, Assaf

    2014-11-01

    Marine viruses are recognized as a major driving force regulating phytoplankton community composition and nutrient cycling in the oceans. Yet, little is known about mechanisms that influence viral dispersal in aquatic systems, other than physical processes, and that lead to the rapid demise of large-scale algal blooms in the oceans. Here, we show that copepods, abundant migrating crustaceans that graze on phytoplankton, as well as other zooplankton can accumulate and mediate the transmission of viruses infecting Emiliania huxleyi, a bloom-forming coccolithophore that plays an important role in the carbon cycle. We detected by PCR that >80% of copepods collected during a North Atlantic E. huxleyi bloom carried E. huxleyi virus (EhV) DNA. We demonstrated by isolating a new infectious EhV strain from a copepod microbiome that these viruses are infectious. We further showed that EhVs can accumulate in high titers within zooplankton guts during feeding or can be adsorbed to their surface. Subsequently, EhV can be dispersed by detachment or via viral-dense fecal pellets over a period of 1 day postfeeding on EhV-infected algal cells, readily infecting new host populations. Intriguingly, the passage through zooplankton guts prolonged EhV's half-life of infectivity by 35%, relative to free virions in seawater, potentially enhancing viral transmission. We propose that zooplankton, swimming through topographically adjacent phytoplankton micropatches and migrating daily over large areas across physically separated water masses, can serve as viral vectors, boosting host-virus contact rates and potentially accelerating the demise of large-scale phytoplankton blooms. PMID:25438947

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

    SciTech Connect

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

    2014-09-15

    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. - Highlights: • Interpretation of urine cadmium concentrations in France • PBPK and Bayesian population modelling of cadmium exposure • Assessment of the historic time-trend of the cadmium exposure in France • Risk assessment from current and future external and internal exposure.

  12. Modeling oscillations and spiral waves in Dictyostelium populations

    NASA Astrophysics Data System (ADS)

    Noorbakhsh, Javad; Schwab, David J.; Sgro, Allyson E.; Gregor, Thomas; Mehta, Pankaj

    2015-06-01

    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 cyclic adenosine monophosphate (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 preprocessing modules. We use this family of models to study spatially unstructured populations of "fixed" cells by constructing phase diagrams that relate the properties of population-level oscillations to parameters in the underlying biochemical network. We then briefly discuss an extension of our model that includes spatial structure and show how this naturally gives 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.

  13. Parameter Estimates in Differential Equation Models for Population Growth

    ERIC Educational Resources Information Center

    Winkel, Brian J.

    2011-01-01

    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,…

  14. Parameter Estimates in Differential Equation Models for Population Growth

    ERIC Educational Resources Information Center

    Winkel, Brian J.

    2011-01-01

    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,

  15. Defining priorities for dog population management through mathematical modeling.

    PubMed

    Santos Baquero, O; Akamine, L A; Amaku, M; Ferreira, F

    2016-01-01

    We simulated dog population dynamics for a thirty-years period using a logistic growth model. Through sensitivity analyses, we determined the influence of the parameters used in the model. Carrying capacity was the most influential parameter in all simulations. In the owned-dog population, the influence of immigration, abandonment and births was 19%, 16% and 6% of the influence of the carrying capacity, respectively. In the sterilized owned-dog population, the influence of abandonment, female and male sterilization was 37%, 30% and 27% of the influence of the carrying capacity. In the stray population, the influence of abandonment, carrying capacity of the owned-dog population and adoption was 10%, 9% and 6% of the influence of the carrying capacity. In the sterilized stray population, the influence of births, female sterilization and male sterilization was 45%, 15% and 13% of the influence of the carrying capacity. Other parameters had lower influence values. Modification of the carrying capacity requires different interventions for the owned- and stray-dog populations. Dog trade control is a way to reduce immigration. The evaluation of sterilization effects must focus on the variations in the infertile population fraction. Adoption may improve the effects of the reduction in carrying capacity on the stray-dog population. PMID:26652574

  16. Feeding of Acanthocylops robustus on zooplankton

    NASA Astrophysics Data System (ADS)

    Yu-Feng, Yang; Brandl, Zdeněk

    1996-03-01

    Feeding of freshwater cyclopoid copepod Acanthocyclops robustus on zooplankton was examined by a senes of feeding experiments during August-September of 1993. Study results showed A. robustus can capture and eat all type items provided from the Starý Haklovský fishpond, a shallow eutrophic water body near Budějovice City, Czech Republic. Selection by the predator was determined largely by prey body-size and density, but was also affected by prey types. Variable but significant changes in feeding rates were found in various size distribution and concentration of prey types. Percentages of small (80-235μm) and large (445-610μm) prey consumed were 42.47 and 3.85%, respectively. Starvation did not cause statistically significant difference. The feeding on Ceriodaphnia quadrangula showed significant difference between large and small prey. Feeding rate increased with increasing prey concentration.

  17. Rostock zooplankton studies off West Africa

    NASA Astrophysics Data System (ADS)

    Postel, L.; Arndt, E. A.; Brenning, U.

    1995-03-01

    Since the beginning of the seventies, upwelling research has become increasingly popular in the path of the Canary and Benguela Current, because of economic consideration, particularly in the relation to fisheries and marine geology. Many expeditions were carried out between 1970 and 1977, including 8 cruises of the German R. V. “A. v. Humboldt” operating from Rostock. Measurements covered scales ranging in time from minutes to several years and in space from hundreds of metres to several thousands of kilometres. Zooplankton studies focussed on quantitative, metabolic, taxonomic, and parasitological aspects. Plankton was collected with a WP-2-UNESCO standard net to a maximum depth of 200 m. The epipelagic mesozooplankton consists mainly of copepods, especially calanoids with developmental times of about 20 to 23 days. After an upwelling event, zooplankton is able to double its biomass. This typical biomass increase is independent of coastal distance and depth. The upwelling response lasts about 3 weeks in nearsurface waters, and 6 to 8 weeks in depths below 75m. A relationship was observed between the duration of seasonal upwelling (that means the numbers of single upwelling events) and the cumulative increase of biomass. This net growth rate of zooplankton biomass is most pronounced at the shelf break, the area with the highest fish biomass, and in the upper 25 m. Differences between the expected and the real rate values in conjunction with the known amount of nutritive demands of fishes allow the estimation of the fish biomass in a given area. The near coastal Ekman upwelling, which is an event in the time scale of about two weeks, also shows seasonality in some areas. Off Northwest Africa the largest expansion was recorded in the first half of the year, extending from 10° N to 24° N, more than 400 km offshore and at least down to 200 m. It contracts in the second half of the year to an area between 20°N and 22°N, 100 to 200 km off the coast and in an average depth of 25 m. These zooplankton biomass patterns are superimposed by mesoscale phenomena, originated by other than Ekman upwelling events. Those are, for example, long coastal parallel waves, producing cells of intensified upwelling and downwelling, and eddies, caused by instabilities in a frontal zone parallel to the coast. Different water masses can be distinguished by indicator species, species combinations or the significant absence of species. This was demonstrated for chaetognaths. The calanoid Calanus helgolandicus (Claus, 1863), a typical species of the North Atlantic, indicates North Atlantic Central Water, whereas Calanoides carinatus (Krøyer, 1849) is an indicator of South Atlantic Central Water. Finally, comparisons of near coastal current regimes, transport velocities, and developmental rates of calanoids allow one to conclude that a suitable mechanism is present to maintain plankton in the coastal environment.

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

    USGS Publications Warehouse

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

    2013-01-01

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

  19. A model of northern pintail productivity and population growth rate

    USGS Publications Warehouse

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

    1998-01-01

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

  20. Modeling Bacterial Population Growth from Stochastic Single-Cell Dynamics

    PubMed Central

    Molina, Ignacio; Theodoropoulos, Constantinos

    2014-01-01

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

  1. Modeling bacterial population growth from stochastic single-cell dynamics.

    PubMed

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

    2014-09-01

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

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

    PubMed

    Wang, Magnus

    2013-04-01

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

  3. Migrant biomass and respiratory carbon flux by zooplankton and micronekton in the subtropical northeast Atlantic Ocean (Canary Islands)

    NASA Astrophysics Data System (ADS)

    Ariza, A.; Garijo, J. C.; Landeira, J. M.; Bordes, F.; Hernández-León, S.

    2015-05-01

    Diel Vertical Migration (DVM) in marine ecosystems is performed by zooplankton and micronekton, promoting a poorly accounted export of carbon to the deep ocean. Major efforts have been made to estimate carbon export due to gravitational flux and to a lesser extent, to migrant zooplankton. However, migratory flux by micronekton has been largely neglected in this context, due to its time-consuming and difficult sampling. In this paper, we evaluated gravitational and migratory flux due to the respiration of zooplankton and micronekton in the northeast subtropical Atlantic Ocean (Canary Islands). Migratory flux was addressed by calculating the biomass of migrating components and measuring the electron transfer system (ETS) activity in zooplankton and dominant species representing micronekton (Euphausia gibboides, Sergia splendens and Lobianchia dofleini). Our results showed similar biomass in both components. The main taxa contributing to DVM within zooplankton were juvenile euphausiids, whereas micronekton were mainly dominated by fish, followed by adult euphausiids and decapods. The contribution to respiratory flux of zooplankton (3.4 ± 1.9 mg C m-2 d-1) was similar to that of micronekton (2.9 ± 1.0 mg C m-2 d-1). In summary, respiratory flux accounted for 53% (range 23-71) of the gravitational flux measured at 150 m depth (11.9 ± 5.8 mg C m-2 d-1). However, based on larger migratory ranges and gut clearance rates, micronekton are expected to be the dominant component that contributes to carbon export in deeper waters. Micronekton estimates in this paper as well as those in existing literature, although variable due to regional differences and difficulties in calculating their biomass, suggest that carbon fluxes driven by this community are important for future models of the biological carbon pump.

  4. Parasitic chytrids sustain zooplankton growth during inedible algal bloom

    PubMed Central

    Rasconi, Serena; Grami, Boutheina; Niquil, Nathalie; Jobard, Marlène; Sime-Ngando, Télesphore

    2014-01-01

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

  5. Parasitic chytrids sustain zooplankton growth during inedible algal bloom.

    PubMed

    Rasconi, Serena; Grami, Boutheina; Niquil, Nathalie; Jobard, Marlène; Sime-Ngando, Télesphore

    2014-01-01

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

  6. A hierarchical model for estimating change in American Woodcock populations

    USGS Publications Warehouse

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

    2008-01-01

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

  7. Developing population models with data from marked individuals

    USGS Publications Warehouse

    Hae Yeong Ryu; Kevin T. Shoemaker; Eva Kneip; Anna Pidgeon; Patricia Heglund; Brooke Bateman; Thogmartin, Wayne E.; Reşit Akçakaya

    2016-01-01

    Population viability analysis (PVA) is a powerful tool for biodiversity assessments, but its use has been limited because of the requirements for fully specified population models such as demographic structure, density-dependence, environmental stochasticity, and specification of uncertainties. Developing a fully specified population model from commonly available data sources – notably, mark–recapture studies – remains complicated due to lack of practical methods for estimating fecundity, true survival (as opposed to apparent survival), natural temporal variability in both survival and fecundity, density-dependence in the demographic parameters, and uncertainty in model parameters. We present a general method that estimates all the key parameters required to specify a stochastic, matrix-based population model, constructed using a long-term mark–recapture dataset. Unlike standard mark–recapture analyses, our approach provides estimates of true survival rates and fecundities, their respective natural temporal variabilities, and density-dependence functions, making it possible to construct a population model for long-term projection of population dynamics. Furthermore, our method includes a formal quantification of parameter uncertainty for global (multivariate) sensitivity analysis. We apply this approach to 9 bird species and demonstrate the feasibility of using data from the Monitoring Avian Productivity and Survivorship (MAPS) program. Bias-correction factors for raw estimates of survival and fecundity derived from mark–recapture data (apparent survival and juvenile:adult ratio, respectively) were non-negligible, and corrected parameters were generally more biologically reasonable than their uncorrected counterparts. Our method allows the development of fully specified stochastic population models using a single, widely available data source, substantially reducing the barriers that have until now limited the widespread application of PVA. This method is expected to greatly enhance our understanding of the processes underlying population dynamics and our ability to analyze viability and project trends for species of conservation concern.

  8. Population dynamics of pond zooplankton II Daphnia ambigua Scourfield

    USGS Publications Warehouse

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

    1973-01-01

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

  9. Estimation of population size using open capture-recapture models

    USGS Publications Warehouse

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

    2001-01-01

    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.

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

    PubMed

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

    2014-12-01

    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

  11. Estimating a geographically explicit model of population divergence.

    PubMed

    Knowles, L Lacey; Carstens, Bryan C

    2007-03-01

    Patterns of genetic variation can provide valuable insights for deciphering the relative roles of different evolutionary processes in species differentiation. However, population-genetic models for studying divergence in geographically structured species are generally lacking. Since these are the biogeographic settings where genetic drift is expected to predominate, not only are population-genetic tests of hypotheses in geographically structured species constrained, but generalizations about the evolutionary processes that promote species divergence may also be potentially biased. Here we estimate a population-divergence model in montane grasshoppers from the sky islands of the Rocky Mountains. Because this region was directly impacted by Pleistocene glaciation, both the displacement into glacial refugia and recolonization of montane habitats may contribute to differentiation. Building on the tradition of using information from the genealogical relationships of alleles to infer the geography of divergence, here the additional consideration of the process of gene-lineage sorting is used to obtain a quantitative estimate of population relationships and historical associations (i.e., a population tree) from the gene trees of five anonymous nuclear loci and one mitochondrial locus in the broadly distributed species Melanoplus oregonensis. Three different approaches are used to estimate a model of population divergence; this comparison allows us to evaluate specific methodological assumptions that influence the estimated history of divergence. A model of population divergence was identified that significantly fits the data better compared to the other approaches, based on per-site likelihood scores of the multiple loci, and that provides clues about how divergence proceeded in M. oregonensis during the dynamic Pleistocene. Unlike the approaches that either considered only the most recent coalescence (i.e., information from a single individual per population) or did not consider the pattern of coalescence in the gene genealogies, the population-divergence model that best fits the data was estimated by considering the pattern of gene lineage coalescence across multiple individuals, as well as loci. These results indicate that sampling of multiple individuals per population is critical to obtaining an accurate estimate of the history of divergence so that the signal of common ancestry can be separated from the confounding influence of gene flow-even though estimates suggest that gene flow is not a predominant factor structuring patterns of genetic variation across these sky island populations. They also suggest that the gene genealogies contain information about population relationships, despite the lack of complete sorting of gene lineages. What emerges from the analyses is a model of population divergence that incorporates both contemporary distributions and historical associations, and shows a latitudinal and regional structuring of populations reminiscent of population displacements into multiple glacial refugia. Because the population-divergence model itself is built upon the specific events shaping the history of M. oregonensis, it provides a framework for estimating additional population-genetic parameters relevant to understanding the processes governing differentiation in geographically structured species and avoids the problems of relying on overly simplified and inaccurate divergence models. The utility of these approaches, as well as the caveats and future improvements, for estimating population relationships and historical associations relevant to genetic analyses of geographically structured species are discussed. PMID:17348914

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

    SciTech Connect

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

    1986-03-01

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

  13. Seasonal cycles of zooplankton from San Francisco Bay

    USGS Publications Warehouse

    Ambler, Julie W.; Cloern, James E.; Hutchinson, Anne

    1985-01-01

    Seasonal cycles of zooplankton abundance appear to be constant among years (1978–1981) and are similar in the deep (>10 m) channels and lateral shoals (<3 m). The seasonal zooplankton community dynamics are discussed in relation to: (1) river discharge which alters salinity distribution and residence time of plankton; (2) temperature which induces production and hatching of dormant copepod eggs; (3) coastal hydrography which brings neritic copepods of different zoogeographic affinities into the bay; and (4) seasonal cycles of phytoplankton.

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

    PubMed

    Buchin, A Iu; Chizhov, A V

    2010-01-01

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

  15. Numerical simulations of submesoscale balanced vertical velocity forcing unsteady nutrient-phytoplankton-zooplankton distributions

    NASA Astrophysics Data System (ADS)

    Videz, Lvaro; Claret, Mariona

    2009-04-01

    The effect of submesoscale balanced (void of waves) vertical velocity on initially steady nutrient-phytoplankton-zooplankton (NPZ) distributions is investigated numerically. First, steady vertical NPZ profiles, continuous but not continuously differentiable at several depths, are found as analytical solutions to the NPZ equations in the absence of flow. These solutions admit numerical equivalents that are continuously differentiable in the numerical sense, here meaning convergence of the vertical derivative with respect to increasing vertical resolution. These NPZ solutions require, however, large vertical resolutions, with a grid size of few centimeters, to be properly discretisized. The ecological model is next coupled to a nonhydrostatic Boussinesq f plane physical model that explicitly conserves potential vorticity on isopycnals. Then the NPZ solutions are used as steady initial ecosystem conditions to investigate the role of submesoscale balanced vertical velocity in forcing NPZ anomalies in an idealized case of a baroclinic unstable jet. The results show that the baroclinic flow rapidly develops balanced vertical velocity that in turn favors NPZ anomalies. A large cancelation between the local change and the horizontal advection occurs in the ecosystem variables. This particularly occurs for zooplankton anomalies that therefore behave as better passive tracers of the horizontal flow than phytoplankton anomalies. However, once phytoplankton and zooplankton anomalies develop locally, forced by vertical velocity, they are horizontally advected away from the upwelling or downwelling regions so that spatial distributions of vertical velocity and ecological fields become eventually uncorrelated.

  16. An aerial sightability model for estimating ferruginous hawk population size

    USGS Publications Warehouse

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

    1999-01-01

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

  17. Modeling structured population dynamics using data from unmarked individuals

    USGS Publications Warehouse

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

    2014-01-01

    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.

  18. A Dose-Structured Population Dynamics Model for Outmigrant Salmon

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

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

  19. Model for the chemotactic response of a bacterial population.

    PubMed Central

    Lapidus, I R; Schiller, R

    1976-01-01

    We present a mathematical model for the motion of a bacterial population in prescribed attractant or repellent gradients. The model is suggested by the observations of Mesibov et al. (1973, J. Gen. Physiol. 62:203) and Brown and Berg (1974, Proc. Natl. Acad. Sci. U.S.A. 71:1388) who found that the sensitivity of the chemotactic response depends on the concentration of attractant. Predictions of the theory are in general agreement with the experiments of Dahlquist et al. (1972, Nat. New Biol. 236:120) and of Mesibov et al. on populations of motile bacteria in fixed attractant gradients. Additional tests of the model are proposed. PMID:938718

  20. Internal models for interpreting neural population activity during sensorimotor control.

    PubMed

    Golub, Matthew D; Yu, Byron M; Chase, Steven M

    2015-01-01

    To successfully guide limb movements, the brain takes in sensory information about the limb, internally tracks the state of the limb, and produces appropriate motor commands. It is widely believed that this process uses an internal model, which describes our prior beliefs about how the limb responds to motor commands. Here, we leveraged a brain-machine interface (BMI) paradigm in rhesus monkeys and novel statistical analyses of neural population activity to gain insight into moment-by-moment internal model computations. We discovered that a mismatch between subjects' internal models and the actual BMI explains roughly 65% of movement errors, as well as long-standing deficiencies in BMI speed control. We then used the internal models to characterize how the neural population activity changes during BMI learning. More broadly, this work provides an approach for interpreting neural population activity in the context of how prior beliefs guide the transformation of sensory input to motor output. PMID:26646183

  1. Models for age structured populations with distributed maturation rates.

    PubMed

    Plant, R E; Wilson, L T

    1986-01-01

    In the use of age structured population models for agricultural applications such as the modeling of crop-pest interactions it is often essential that the model take into account the distribution in maturation rates present in some or all of the populations. The traditional method for incorporating distributed maturation rates into crop and pest models has been the so-called "distributed delay" method. In this paper we review the application of the distributed delay formalism to the McKendrick equation of an age structured population. We discuss the mathematical properties of the system of ordinary differential equations arising out of the distributed delay formalism. We then discuss an alternative method involving modification of the Leslie matrix. PMID:3958638

  2. 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...

  3. 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 ...

  4. Size-specific sensitivity: Applying a new structured population model

    SciTech Connect

    Easterling, M.R.; Ellner, S.P.; Dixon, P.M.

    2000-03-01

    Matrix population models require the population to be divided into discrete stage classes. In many cases, especially when classes are defined by a continuous variable, such as length or mass, there are no natural breakpoints, and the division is artificial. The authors introduce the integral projection model, which eliminates the need for division into discrete classes, without requiring any additional biological assumptions. Like a traditional matrix model, the integral projection model provides estimates of the asymptotic growth rate, stable size distribution, reproductive values, and sensitivities of the growth rate to changes in vital rates. However, where the matrix model represents the size distributions, reproductive value, and sensitivities as step functions (constant within a stage class), the integral projection model yields smooth curves for each of these as a function of individual size. The authors describe a method for fitting the model to data, and they apply this method to data on an endangered plant species, northern monkshood (Aconitum noveboracense), with individuals classified by stem diameter. The matrix and integral models yield similar estimates of the asymptotic growth rate, but the reproductive values and sensitivities in the matrix model are sensitive to the choice of stage classes. The integral projection model avoids this problem and yields size-specific sensitivities that are not affected by stage duration. These general properties of the integral projection model will make it advantageous for other populations where there is no natural division of individuals into stage classes.

  5. On population size estimators in the Poisson mixture model.

    PubMed

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

    2013-09-01

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

  6. Modelling interactions of toxicants and density dependence in wildlife populations

    USGS Publications Warehouse

    Schipper, Aafke M.; Hendriks, Harrie W.M.; Kauffman, Matthew J.; Hendriks, A. Jan; Huijbregts, Mark A.J.

    2013-01-01

    1. A major challenge in the conservation of threatened and endangered species is to predict population decline and design appropriate recovery measures. However, anthropogenic impacts on wildlife populations are notoriously difficult to predict due to potentially nonlinear responses and interactions with natural ecological processes like density dependence. 2. Here, we incorporated both density dependence and anthropogenic stressors in a stage-based matrix population model and parameterized it for a density-dependent population of peregrine falcons Falco peregrinus exposed to two anthropogenic toxicants [dichlorodiphenyldichloroethylene (DDE) and polybrominated diphenyl ethers (PBDEs)]. Log-logistic exposure–response relationships were used to translate toxicant concentrations in peregrine falcon eggs to effects on fecundity. Density dependence was modelled as the probability of a nonbreeding bird acquiring a breeding territory as a function of the current number of breeders. 3. The equilibrium size of the population, as represented by the number of breeders, responded nonlinearly to increasing toxicant concentrations, showing a gradual decrease followed by a relatively steep decline. Initially, toxicant-induced reductions in population size were mitigated by an alleviation of the density limitation, that is, an increasing probability of territory acquisition. Once population density was no longer limiting, the toxicant impacts were no longer buffered by an increasing proportion of nonbreeders shifting to the breeding stage, resulting in a strong decrease in the equilibrium number of breeders. 4. Median critical exposure concentrations, that is, median toxicant concentrations in eggs corresponding with an equilibrium population size of zero, were 33 and 46 μg g−1 fresh weight for DDE and PBDEs, respectively. 5. Synthesis and applications. Our modelling results showed that particular life stages of a density-limited population may be relatively insensitive to toxicant impacts until a critical threshold is crossed. In our study population, toxicant-induced changes were observed in the equilibrium number of nonbreeding rather than breeding birds, suggesting that monitoring efforts including both life stages are needed to timely detect population declines. Further, by combining quantitative exposure–response relationships with a wildlife demographic model, we provided a method to quantify critical toxicant thresholds for wildlife population persistence.

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

    NASA Astrophysics Data System (ADS)

    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

    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.

  8. Spatial/temporal variations in zooplankton biomass and ecological characteristics of major species in the southern part of the Japan Sea: a review

    NASA Astrophysics Data System (ADS)

    Iguchi, Naoki

    2004-05-01

    During the 1990s many studies on zooplankton in the Japan Sea have been carried out. In this review, I have synthesized the study of horizontal distribution, seasonal and annual variations of zooplankton biomass, and ecological characteristics of major component species in the southern Japan Sea, which area is influenced by the warm Tsushima Current. The zooplankton biomass (annual mean) in the southern Japan Sea was lower than in the subarctic Pacific, including the northern Japan Sea, and similar to biomass levels in Kuroshio waters. Temporal variations in zooplankton biomass showed both seasonal and year-to-year components. Seasonal biomass increases to a maximum in spring with a weak secondary peak in autumn. As for long-term changes, 3-6 year cycles were identified, with the dynamics of the surface warm Tsushima Current and the subsurface cold water playing important roles in determining the yearly zooplankton community structure and biomass. Cold water species in the southern Japan Sea had extensive diel vertical migrations whose range is restricted in summer by the development of a thermocline. Among these species, the herbivores Euphausia pacifica and Metridia pacifica encounter a lower food supply, resulting in lower growth rates. The vertical dispersal of epipelagic carnivorous zooplankton such as Sagitta elegans and Themisto japonica to the deep-sea is probably facilitated by reduced interspecific competition. Their interaction with Japan Sea Proper Water, characterized by near-zero temperatures in the meso- and bathypelagic zones suppresses growth rates of the mesopelagic zooplankton. The lack of micronektonic predators in the mesopelagic zone may allow the persistence of slow growing populations.

  9. OASIS in the sea: Measurement of the acoustic reflectivity of zooplankton with concurrent optical imaging

    NASA Astrophysics Data System (ADS)

    Jaffe, J. S.; Ohman, M. D.; De Robertis, A.

    A new instrument Optical-Acoustic Submersible Imaging System (OASIS) has been developed for three-dimensional acoustic tracking of zooplankton with concurrent optical imaging to verify the identity of the insonified organisms. OASIS also measures in situ target strengths (TS) of freely swimming zooplankton and nekton of known identity and 3-D orientation. The system consists of a three-dimensional acoustic imaging system (FishTV), a sensitive optical CCD camera with red-filtered strobe illumination, and ancillary oceanographic sensors. The sonar triggers the acquisition of an optical image when it detects the presence of a significant target in the precise location where the camera, strobe and sonar are co-registered. Acoustic TS can then be related to the optical image, which permits identification of the animal and its 3-D aspect. The system was recently deployed (August 1996) in Saanich Inlet, B.C., Canada. Motile zooplankton and nekton were imaged with no evidence of reaction to or avoidance of the OASIS instrument package. Target strengths of many acoustic reflectors were recorded in parallel with the optical images, triggered by the presence of an animal in the correct location of the sonar system. Inspection of the optical images, corroborated with zooplankton sampling with a MOCNESS net, revealed that the joint optically and acoustically sensed taxa at the site were the euphausiid Euphausia pacifica, the gammarid amphipod Orchomene obtusa, and a gadid fish. The simultaneous optical and acoustic images permitted an exact correlation of TS and taxa. Computer simulations from a model of the backscattered strength from euphausiids are in good agreement with the observed data.

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

    SciTech Connect

    Bowers, J.A.; Bowen, M.

    1992-03-01

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

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

    SciTech Connect

    Schell, D.M.

    1992-06-01

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

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

    USGS Publications Warehouse

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

    1995-01-01

    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.

  13. The vertical distribution of zooplankton in the eastern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Hopkins, Thomas L.

    1982-09-01

    The zooplankton community in the eastern Gulf of Mexico was investigated to determine the quantity and taxonomic composition of forage available to higher trophic levels and to provide a data base for future trophodynamic modelling. Standing stock (1.2 g m -2, dw) in the upper 1000 m is in the range for oligotrophic low-latitude boundary currents but is greater than in central gyre areas. Abundance decreases exponentially with depth, over half the biomass occuring in the upper 200 m. Diel variations are apparent, the greatest differences in biomass occuring in the upper 50 m and at 300 to 350 m. Copepods were dominant, contributing over 80% of the number and half the net-caught biomass. The zooplankton community is diverse, 21 genera individually exceeding 1% of the biomass in the 0 to 100-m layer. Grazers (herbivores, detritivores, omnivores) were 66% of the 0 to 1000-m standing stock and carnivores 34%, their biomass in the epipelagic zone above the base of the thermocline (150 m) at night increasing 46 and 57%, respectively. Zooplankton biomass available as forage for higher trophic levels is most concentrated in the upper 50 m, whereas, paradoxically, the zooplanktivorous micronekton, the myctophid fishes in particular, are centered deeper, primarily between 50 and 150 m.

  14. Stochastic resonance in a generalized Von Foerster population growth model

    SciTech Connect

    Lumi, N.; Mankin, R.

    2014-11-12

    The stochastic dynamics of a population growth model, similar to the Von Foerster model for human population, is studied. The influence of fluctuating environment on the carrying capacity is modeled as a multiplicative dichotomous noise. It is established that an interplay between nonlinearity and environmental fluctuations can cause single unidirectional discontinuous transitions of the mean population size versus the noise amplitude, i.e., an increase of noise amplitude can induce a jump from a state with a moderate number of individuals to that with a very large number, while by decreasing the noise amplitude an opposite transition cannot be effected. An analytical expression of the mean escape time for such transitions is found. Particularly, it is shown that the mean transition time exhibits a strong minimum at intermediate values of noise correlation time, i.e., the phenomenon of stochastic resonance occurs. Applications of the results in ecology are also discussed.

  15. Ancestral population genomics: the coalescent hidden Markov model approach.

    PubMed

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

    2009-09-01

    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

  16. Time-delayed coupled logistic capacity model in population dynamics

    NASA Astrophysics Data System (ADS)

    Cáceres, Manuel O.

    2014-08-01

    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.

  17. Model estimation of energy flow in Oregon coastal seabird populations

    USGS Publications Warehouse

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

    1976-01-01

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

  18. Modeling population access to New Zealand public hospitals

    PubMed Central

    Brabyn, Lars; Skelly, Chris

    2002-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

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

  20. Modeling Climate Change and Sturgeon Populations in the Missouri River

    USGS Publications Warehouse

    Wildhaber, Mark L.

    2010-01-01

    The U.S. Geological Survey (USGS) Columbia Environmental Research Center (CERC), in collaboration with researchers from the University of Missouri and Iowa State University, is conducting research to address effects of climate change on sturgeon populations (Scaphirhynchus spp.) in the Missouri River. The CERC is conducting laboratory, field, and modeling research to identify causative factors for the responses of fish populations to natural and human-induced environmental changes and using this information to understand sensitivity of sturgeon populations to potential climate change in the Missouri River drainage basin. Sturgeon response information is being used to parameterize models predicting future population trends. These models will provide a set of tools for natural resource managers to assess management strategies in the context of global climate change. This research complements and builds on the ongoing Comprehensive Sturgeon Research Program (CSRP) at the CERC. The CSRP is designed to provide information critical to restoration of the Missouri River ecosystem and the endangered pallid sturgeon (S. albus). Current research is being funded by USGS through the National Climate Change Wildlife Science Center (NCCWSC) and the Science Support Partnership (SSP) Program that is held by the USGS and the U.S. Fish and Wildlife Service. The national mission of the NCCWSC is to improve the capacity of fish and wildlife agencies to respond to climate change and to address high-priority climate change effects on fish and wildlife. Within the national context, the NCCWSC research on the Missouri River focuses on temporal and spatial downscaling and associated uncertainty in modeling climate change effects on sturgeon species in the Missouri River. The SSP research focuses on improving survival and population estimates for pallid sturgeon population models.

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

    PubMed

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

    2013-09-01

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

  2. Incorporating parametric uncertainty into population viability analysis models

    USGS Publications Warehouse

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

    2011-01-01

    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.

  3. 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

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

    1981-05-01

    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.

  4. Effects of polycyclic aromatic hydrocarbons (PAHs) on an aquatic ecosystem: acute toxicity and community-level toxic impact tests of benzo[a]pyrene using lake zooplankton community.

    PubMed

    Ikenaka, Yoshinori; Sakamoto, Masaki; Nagata, Takamaru; Takahashi, Hirokazu; Miyabara, Yuichi; Hanazato, Takayuki; Ishizuka, Mayumi; Isobe, Tomohiko; Kim, Jun-Woo; Chang, Kwang-Hyeon

    2013-02-01

    We estimated acute toxicity of benzo[a]pyrene (B[a]P) using two cladoceran species, Ceriodaphnia reticulata and Daphnia magna, and also analyzed its impact on zooplankton community throughout an exposure experiment using small-scale mesocosms. LC(50) of B[a]P for C. reticulata and D. magna was 4.3 and 4.7 µg/l, respectively. However, individuals fed with Chlorella showed higher LC(50), 6.1 µg/l for C. reticulata and 8.0 µg/l for D. magna. In the exposure experiment, we examined the impact of B[a]P on zooplankton community using conceivable concentrations in the environment (5 and 10 µg/l) using typical zooplankton community in eutrophicated systems. Despite the residence time of B[a]P in the water column was short as < 4 days, application of B[a]P induced decrease of zooplankton abundance. However, the recovery pattern was different among cladocerans and rotifers. Consequently, B[a]P showed insecticide-like impacts, suppressing cladoceran populations and inducing the dominance of rotifers particularly under high concentration (10 µg/l). Results have suggested that, even such short duration of B[a]P in the water body can have impact on zooplankton abundance and community structure. Since B[a]P easily precipitate to the bottom and rapidly disappears from the water body, careful monitoring and further assessment of the potential toxicity of polycyclic aromatic hydrocarbons are necessary. PMID:23358147

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

    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 α-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.

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

    SciTech Connect

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

    2013-01-15

    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.

  7. Modeling Population Exposures to Silver Nanoparticles Present in Consumer Products

    PubMed Central

    Royce, Steven G.; Mukherjee, Dwaipayan; Cai, Ting; Xu, Shu S.; Alexander, Jocelyn A.; Mi, Zhongyuan; Calderon, Leonardo; Mainelis, Gediminas; Lee, KiBum; Lioy, Paul J.; Tetley, Teresa D.; Chung, Kian Fan; Zhang, Junfeng; Georgopoulos, Panos G.

    2014-01-01

    Exposures of the general population to manufactured nanoparticles (MNPs) are expected to keep rising due to increasing use of MNPs in common consumer products (PEN 2014). The present study focuses on characterizing ambient and indoor population exposures to silver MNPs (nAg). For situations where detailed, case-specific exposure-related data are not available, as in the present study, a novel tiered modeling system, Prioritization/Ranking of Toxic Exposures with GIS (Geographic Information System) Extension (PRoTEGE), has been developed: it employs a product Life Cycle Analysis (LCA) approach coupled with basic human Life Stage Analysis (LSA) to characterize potential exposures to chemicals of current and emerging concern. The PRoTEGE system has been implemented for ambient and indoor environments, utilizing available MNP production, usage, and properties databases, along with laboratory measurements of potential personal exposures from consumer spray products containing nAg. Modeling of environmental and microenvironmental levels of MNPs employs Probabilistic Material Flow Analysis combined with product LCA to account for releases during manufacturing, transport, usage, disposal, etc. Human exposure and dose characterization further employs screening Microenvironmental Modeling and Intake Fraction methods combined with LSA for potentially exposed populations, to assess differences associated with gender, age, and demographics. Population distributions of intakes, estimated using the PRoTEGE framework, are consistent with published individual-based intake estimates, demonstrating that PRoTEGE is capable of capturing realistic exposure scenarios for the US population. Distributions of intakes are also used to calculate biologically-relevant population distributions of uptakes and target tissue doses through human airway dosimetry modeling that takes into account product MNP size distributions and age-relevant physiological parameters. PMID:25745354

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

    NASA Astrophysics Data System (ADS)

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

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

  9. Nonlinear PI controllers for continuous bioreactors using population balance models.

    PubMed

    Wu, Wei; Chang, Haw-Yuan

    2005-11-01

    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

  10. Zooplankton structure and dynamics in two estuaries from the Atlantic coast in relation to multi-stressors exposure

    NASA Astrophysics Data System (ADS)

    Vieira, L. R.; Guilhermino, L.; Morgado, F.

    2015-12-01

    The aim of this research was to investigate the response of pelagic zooplankton to different levels of abiotic multi-stressors in the North Atlantic coast, taking advantage of the comparison of the communities of two adjacent estuaries with different levels of historical pollution (estuaries of Minho and Lima Rivers). The zooplankton community structure, composition and temporal variation were comparatively investigated for 15 months, using different net meshes. Several abiotic factors were measured in situ and water samples were simultaneously collected for determination of nutrients and chlorophyll a. The overall results revealed a diverse community represented by species that have been found in subtropical and temperate zones. Although the highest diversity was observed in the Lima estuary, supported by higher contributions of marine taxa, the total zooplankton biomass was found to be significantly higher in the Minho estuary. The salinity gradient differences between estuaries, associated to significant differences in water nutrients levels, were found to be the main forcing factors affecting micro and mesozooplankton. Considering the importance of the impacts resulting from abiotic variation on the basis of aquatic food webs, the present investigation represented a case-study, based in two contrasting estuaries, one strongly influenced by freshwater discharges (Minho estuary) and the other with higher salinity levels (Lima estuary), contributing to a better understanding of the effects of multi-stressors on pelagic zooplankton communities, providing useful information for studies related with climate change impacts, biogeography, conservation and providing data contributing to the improvement of pelagic fisheries management models.

  11. Population genetics of Setaria viridis, a new model system

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An extensive survey of the standing genetic variation in natural populations is among the priority steps in developing a species into a model system. In recent years, green foxtail (Setaria viridis), along with its domesticated form foxtail millet (S. italica), has rapidly become a promising new mod...

  12. Galactic dual population models of gamma-ray bursts

    NASA Technical Reports Server (NTRS)

    Higdon, J. C.; Lingenfelter, R. E.

    1994-01-01

    We investigate in more detail the properties of two-population models for gamma-ray bursts in the galactic disk and halo. We calculate the gamma-ray burst statistical properties, mean value of (V/V(sub max)), mean value of cos Theta, and mean value of (sin(exp 2) b), as functions of the detection flux threshold for bursts coming from both Galactic disk and massive halo populations. We consider halo models inferred from the observational constraints on the large-scale Galactic structure and we compare the expected values of mean value of (V/V(sub max)), mean value of cos Theta, and mean value of (sin(exp 2) b), with those measured by Burst and Transient Source Experiment (BATSE) and other detectors. We find that the measured values are consistent with solely Galactic populations having a range of halo distributions, mixed with local disk distributions, which can account for as much as approximately 25% of the observed BATSE bursts. M31 does not contribute to these modeled bursts. We also demonstrate, contrary to recent arguments, that the size-frequency distributions of dual population models are quite consistent with the BATSE observations.

  13. Zooplanktonic community of six reservoirs in northeast Brazil.

    PubMed

    Almeida, V L S; Dantas, E W; Melo-Júnior, M; Bittencourt-Oliveira, M C; Moura, A N

    2009-02-01

    The aim of the present study was to investigate the zooplankton community at six reservoirs in the state of Pernambuco (Brazil). Zooplankton assemblages were identified using current literature and quantitatively analysed under a microscope and stereomicroscope. Concurrently to the sampling of zooplanktonic and phytoplanktonic communities, in situ measurements of abiotic variables, such as water temperature, dissolved oxygen and pH, were determined using field probes and transparency was determined with a Secchi disk. Total phosphorus concentrations were used for the determination of the Trophic State Index. The reservoirs were classified between eutrophic and hypertrophic, oxygenated, with pH varying from slightly acid to alkaline, high temperatures and low water transparency. A total of 27 zooplankton taxa were identified. Phytoplankton was represented by Cyanophyta, Chlorophyta, Baccilariophyta and phytoflagellates. The highest richness of species was observed for Rotifera (17), followed by Crustacea (8), Protozoa (1) and Insecta (1). Rotifers shared quantitative importance with Crustacea, which were mainly represented by juvenile forms. Jazigo Reservoir presented the highest diversity and equitability. Lowest diversity and equitability were recorded at the Poço da Cruz and Mundaú reservoirs, respectively. Dissimilarity was detected between the environments studied regarding zooplankton composition and structure. PMID:19347146

  14. Mesoscale physical variability affects zooplankton production in the Labrador Sea

    NASA Astrophysics Data System (ADS)

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

    2009-05-01

    Surface distribution (0-100 m) of zooplankton biomass and specific aminoacyl-tRNA synthetases (AARS) activity, as a proxy of structural growth, were assessed during winter 2002 and spring 2004 in the Labrador Sea. Two fronts formed by strong boundary currents, several anticyclonic eddies and a cyclonic eddy were studied. The spatial contrasts observed in seawater temperature, salinity and fluorescence, associated with those mesoscale structures, affected the distributions of both zooplankton biomass and specific AARS activity, particularly those of the smaller individuals. Production rates of large organisms (200-1000 ?m) were significantly related to microzooplankton biomass (63-200 ?m), suggesting a cascade effect from hydrography through microzooplankton to large zooplankton. Water masses defined the biomass distribution of the three dominant species: Calanus glacialis was restricted to cold waters on the shelves while Calanus hyperboreus and Calanus finmarchicus were widespread from Canada to Greenland. Zooplankton production was up to ten-fold higher inside anticyclonic eddies than in the surrounding waters. The recent warming tendency observed in the Labrador Sea will likely generate weaker convection and less energetic mesoscale eddies. This may lead to a decrease in zooplankton growth and production in the Labrador basin.

  15. Zooplankton communities of a new pumped storage reservoir

    SciTech Connect

    Potter, D.U.; Meyer, J.L.

    1982-08-01

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

  16. Nitrogen isotopic ratios in fecal pellets produced by marine zooplankton

    SciTech Connect

    Altabet, M.A. ); Small, L.F. )

    1990-01-01

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

  17. A model agreement for genetic research in socially identifiable populations.

    PubMed

    Foster, M W; Bernsten, D; Carter, T H

    1998-09-01

    Genetic research increasingly focuses on population-specific human genetic diversity. However, the naming of a human population in public databases and scientific publications entails collective risks for its members. Those collective risks can be evaluated and protections can be put in place by the establishment of a dialogue with the subject population, before a research study is initiated. Here we describe an agreement to undertake genetic research with a Native American tribe. We identified the culturally appropriate public and private social units within which community members are accustomed to make decisions about health. We then engaged those units in a process of communal discourse. In their discourses about our proposed study, community members expressed most concern about culturally specific implications. We also found that, in this population, private social units were more influential in communal decision making than were public authorities. An agreement was reached that defined the scope of research, provided options for naming the population in publications (including anonymity), and addressed the distribution of royalties from intellectual property, the future use of archival samples, and specific cultural concerns. We found that informed consent by individuals could not fully address these collective issues. This approach may serve as a general model for the undertaking of population-specific genetic studies. PMID:9718343

  18. Modelling Spread of Oncolytic Viruses in Heterogeneous Cell Populations

    NASA Astrophysics Data System (ADS)

    Ellis, Michael; Dobrovolny, Hana

    2014-03-01

    One of the most promising areas in current cancer research and treatment is the use of viruses to attack cancer cells. A number of oncolytic viruses have been identified to date that possess the ability to destroy or neutralize cancer cells while inflicting minimal damage upon healthy cells. Formulation of predictive models that correctly describe the evolution of infected tumor systems is critical to the successful application of oncolytic virus therapy. A number of different models have been proposed for analysis of the oncolytic virus-infected tumor system, with approaches ranging from traditional coupled differential equations such as the Lotka-Volterra predator-prey models, to contemporary modeling frameworks based on neural networks and cellular automata. Existing models are focused on tumor cells and the effects of virus infection, and offer the potential for improvement by including effects upon normal cells. We have recently extended the traditional framework to a 2-cell model addressing the full cellular system including tumor cells, normal cells, and the impacts of viral infection upon both populations. Analysis of the new framework reveals complex interaction between the populations and potential inability to simultaneously eliminate the virus and tumor populations.

  19. Can modeling improve estimation of desert tortoise population densities?

    USGS Publications Warehouse

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

    2007-01-01

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

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

    SciTech Connect

    Lambert, R.M.

    1989-01-01

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

  1. A frictional population model of seismicity rate change

    USGS Publications Warehouse

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

    2005-01-01

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

  2. Locomotor adaptations of some gelatinous zooplankton.

    PubMed

    Bone, Q

    1985-01-01

    Swimming behaviour and locomotor adaptations are described in chaetognaths, larvacean tunicates, some cnidaria, and thaliacean tunicates. The first two groups swim by oscillating a flattened tail, the others by jet propulsion. In chaetognaths, the locomotor muscle fibres are extensively coupled and relatively sparsely innervated, they exhibit compound spike-like potentials. The motoneurons controlling the rhythmic activity of the locomotor muscle lie in a ventral ganglion whose organization is briefly described. Rhythmic swimming bursts in larvaceans are similarly driven by a caudal ganglion near the base of the tail, but each caudal muscle cell is separately innervated by two sets of motor nerves, as well as being coupled to its neighbours. The external epithelium is excitable, and linked to the caudal ganglion by the axons of central cells. Mechanical stimulation of the epithelium evokes receptor potentials followed by action potentials and by bursts of rapid swimming. The trachyline medusa Aglantha and the small siphonophore Chelophyes also show rapid escape responses; in Aglantha these are driven by a specialized giant axon system lacking in other hydromedusae, and in Chelophyes. Slow swimming in Aglantha apparently involves a second nerve supply to the same muscle sheets used in rapid swimming, whereas in Chelophyes slow swimming results from the activity of the smaller posterior nectophore. Slow swimming in siphonophores is more economical than the rapid responses. In the hydrozoan medusa Polyorchis (as in Chelophyes) action potentials in the locomotor muscle sheet change in shape during swimming bursts, and their duration is related to the size of the medusa; they are not simply triggers of muscular contraction. The two groups of thaliacean tunicates are specialized differently. Doliolum is adapted for single rapid jet pulses (during which it achieves instantaneous velocities of 50 body lengths s-l), whilst salps are adapted for slow continuous swimming. The cost of locomotion is greater in Doliolum. Few gelatinous zooplankton show special adaptations both for rapid escape movements, and for slow sustained swimming, those that do deserve further study. PMID:2871635

  3. Population.

    ERIC Educational Resources Information Center

    King, Pat; Landahl, John

    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…

  4. A mathematical model of syphilis transmission in an MSM population.

    PubMed

    Saad-Roy, C M; Shuai, Zhisheng; van den Driessche, P

    2016-07-01

    Syphilis is caused by the bacterium Treponema pallidum subspecies pallidum, and is a sexually transmitted disease with multiple stages. A model of transmission of syphilis in an MSM population (there has recently been a resurgence of syphilis in such populations) that includes infection stages and treatment is formulated as a system of ordinary differential equations. The control reproduction number is calculated, and it is proved that if this threshold parameter is below one, syphilis dies out; otherwise, if it is greater than one, it is shown that there exists a unique endemic equilibrium and that for certain special cases, this equilibrium is globally asymptotically stable. Using data from the literature on MSM populations, numerical methods are used to determine the variation and robustness of the control reproduction number with respect to the model parameters, and to determine adequate treatment rates for syphilis eradication. By assuming a closed population and no return to susceptibility, an epidemic model is obtained. Final outbreak sizes are numerically determined for various parameter values, and its variation and robustness to parameter value changes is also investigated. Results quantify the importance of early treatment for syphilis control. PMID:27071977

  5. Negative binomial models for abundance estimation of multiple closed populations

    USGS Publications Warehouse

    Boyce, Mark S.; MacKenzie, Darry I.; Manly, Bryan F.J.; Haroldson, Mark A.; Moody, David W.

    2001-01-01

    Counts of uniquely identified individuals in a population offer opportunities to estimate abundance. However, for various reasons such counts may be burdened by heterogeneity in the probability of being detected. Theoretical arguments and empirical evidence demonstrate that the negative binomial distribution (NBD) is a useful characterization for counts from biological populations with heterogeneity. We propose a method that focuses on estimating multiple populations by simultaneously using a suite of models derived from the NBD. We used this approach to estimate the number of female grizzly bears (Ursus arctos) with cubs-of-the-year in the Yellowstone ecosystem, for each year, 1986-1998. Akaike's Information Criteria (AIC) indicated that a negative binomial model with a constant level of heterogeneity across all years was best for characterizing the sighting frequencies of female grizzly bears. A lack-of-fit test indicated the model adequately described the collected data. Bootstrap techniques were used to estimate standard errors and 95% confidence intervals. We provide a Monte Carlo technique, which confirms that the Yellowstone ecosystem grizzly bear population increased during the period 1986-1998.

  6. A stochastic population model of mid-continental mallards

    USGS Publications Warehouse

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

    1992-01-01

    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%.

  7. Two-population dynamics in a growing network model

    NASA Astrophysics Data System (ADS)

    Ivanova, Kristinka; Iordanov, Ivan

    2012-02-01

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

  8. A Bibliometric Analysis on Cancer Population Science with Topic Modeling

    PubMed Central

    Li, Ding-Cheng; Rastegar-Mojarad, Majid; Okamoto, Janet; Liu, Hongfang; Leichow, Scott

    2015-01-01

    Bibliometric analysis is a research method used in library and information science to evaluate research performance. It applies quantitative and statistical analyses to describe patterns observed in a set of publications and can help identify previous, current, and future research trends or focus. To better guide our institutional strategic plan in cancer population science, we conducted bibliometric analysis on publications of investigators currently funded by either Division of Cancer Preventions (DCP) or Division of Cancer Control and Population Science (DCCPS) at National Cancer Institute. We applied two topic modeling techniques: author topic modeling (AT) and dynamic topic modeling (DTM). Our initial results show that AT can address reasonably the issues related to investigators’ research interests, research topic distributions and popularities. In compensation, DTM can address the evolving trend of each topic by displaying the proportion changes of key words, which is consistent with the changes of MeSH headings. PMID:26306249

  9. ORDEM2010 and MASTER-2009 Modeled Small Debris Population Comparison

    NASA Technical Reports Server (NTRS)

    Krisko, Paula H.; Flegel, S.

    2010-01-01

    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.

  10. Searching for an Integrated Watershed Salmonid Population Model

    NASA Astrophysics Data System (ADS)

    Ligon, F. K.; Dietrich, W. E.

    2005-05-01

    In proposing to restore a stream or watershed, we imply that we know what we are restoring and why. However, in many cases, restoration proceeds without having the tools to adequately assess the efficacy of a project-both in terms of its likely local success and what effects it may have at a larger watershed or regional scale. In salmonid ecology and restoration, our approach has been to "step back" and investigate the degree to which geology, tectonics, and climate determine the relative abundance and temporal variability of the species present in a watershed or reach. In other words, does the habitat provided by a landscape prior to European disturbance (the so-called historical reference condition) allow us to predict, using salmon life history theory, the historical population dynamics of all salmonid species for a watershed or region? Likewise, as changes in physical processes have occurred due to human disturbance, can we predict the differential effects on the abundance of different salmonid species historically present in the watershed? To explore these questions, we have developed the "reference model". The reference model is based on a set of desktop watershed analyses tools that estimate a number of landscape attributes including channel slope, drainage area, stream temperature, and shallow landslide sensitivity. The model uses these tools to predict the spatial distribution of habitat and its quality and quantity. Then, by relating the habitat to life stage specific survival, the model predicts population dynamics under reference and current conditions, and under proposed restoration scenarios. In applying the reference model, we explicitly link salmon restoration targets and plans to an understanding of the role of physical processes on the historical and current population dynamics. As is true with most models, the reference model's predictions have the greatest value when they can be treated as testable hypotheses. Ongoing restoration projects that demonstrate the model and explicitly test model predictions will be presented.

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

    USGS Publications Warehouse

    Girdner, Scott; Larson, Gary L.

    1995-01-01

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

  12. Imazethapyr and imazapic, bispyribac-sodium and penoxsulam: zooplankton and dissipation in subtropical rice paddy water.

    PubMed

    Reimche, Geovane B; Machado, Sérgio L O; Oliveira, Maria Angélica; Zanella, Renato; Dressler, Valderi Luiz; Flores, Erico M M; Gonçalves, Fábio F; Donato, Filipe F; Nunes, Matheus A G

    2015-05-01

    Herbicides are very effective at eliminating weed and are largely used in rice paddy around the world, playing a fundamental role in maximizing yield. Therefore, considering the flooded environment of rice paddies, it is necessary to understand the side effects on non-target species. Field experiment studies were carried out during two rice growing seasons in order to address how the commonly-used herbicides imazethapyr and imazapic, bispyribac-sodium and penoxsulam, used at recommended dosage, affect water quality and the non-target zooplankton community using outdoor rice field microcosm set-up. The shortest (4.9 days) and longest (12.2 days) herbicide half-life mean, estimated of the dissipation rate (k) is shown for imazethapyr and bispyribac-sodium, respectively. Some water quality parameters (pH, conductivity, hardness, BOD5, boron, potassium, magnesium, phosphorus and chlorides) achieved slightly higher values at the herbicide treatment. Zooplankton community usually quickly recovered from the tested herbicide impact. Generally, herbicides led to an increase of cladocera, copepods and nauplius population, while rotifer population decreased, with recovery at the end of the experiment (88 days after herbicide treatment). PMID:25659307

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

    NASA Astrophysics Data System (ADS)

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

    2006-06-01

    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.

  14. Modeling the Effects of Mortality on Sea Otter Populations

    USGS Publications Warehouse

    Bodkin, James L.; Ballachey, Brenda E.

    2010-01-01

    Conservation and management of sea otters can benefit from managing the magnitude and sex composition of human related mortality, including harvesting within sustainable levels. Using age and sex-specific reproduction and survival rates from field studies, we created matrix population models representing sea otter populations with growth rates of 1.005, 1.072, and 1.145, corresponding to stable, moderate, and rapid rates of change. In each modeled population, we incrementally imposed additional annual mortality over a 20-year period and calculated average annual rates of change (lambda). Additional mortality was applied to (1) males only, (2) at a 1:1 ratio of male to female, and (3) at a 3:1 ratio of male to female. Dependent pups (age 0-0.5) were excluded from the mortality. Maintaining a stable or slightly increasing population was largely dependent on (1) the magnitude of additional mortality, (2) the underlying rate of change in the population during the period of additional mortality, and (3) the extent that females were included in the additional mortality (due to a polygnous reproductive system where one male may breed with more than one female). In stable populations, additional mortality as high as 2.4 percent was sustainable if limited to males only, but was reduced to 1.2 percent when males and females were removed at ratios of 3:1 or 0.5 percent at ratios of 1:1. In moderate growth populations, additional mortality of 9.8 percent (male-only) and 15.0 percent (3:1 male to female) maximized the sustainable mortality about 3-10 ten-fold over the stable population levels. However, if additional mortality consists of males and females at equal proportions, the sustainable rate is 7.7 percent. In rapid growth populations, maximum sustainable levels of mortality as high as 27.3 percent were achieved when the ratio of additional mortality was 3:1 male to female. Although male-only mortality maximized annual harvest in stable populations, high male biased mortality in all simulations eventually led to low proportions of males, leading to instability in projected populations over time. Our findings identify the critical need to understand underlying rates of change that can be acquired only through frequent monitoring of managed populations. Models could be improved through better understanding of the effects of density and demographic and environmental stochasticity on sea otter vital rates. Although our primary objective was to provide information useful in managing harvests of sea otters, our findings have implications for the conservation and management of sea otter populations subjected to other sources of mortality that can be quantified, such as incidental, accidental, or illegal.

  15. Encounters of spherical galaxies. I - Galaxy models with one stellar population. II - Galaxy models with two stellar populations

    NASA Technical Reports Server (NTRS)

    Biermann, P.; Silk, J.

    1976-01-01

    Close encounters between two spherical galaxies of equal size and consisting of only one stellar population are calculated using models of elliptical galaxies constructed according to King's (1966) method. The mass loss and the change in internal energy are computed under the assumption that the stars do not change their velocity or density distributions during the encounters. The results for a specific case are compared with the calculations of Gallagher and Ostriker (1972), who employed the observed brightness distribution and the derived density distribution of the E1 galaxy NGC 3379. For models with one stellar population, the results suggest that the radius of a galactic halo would have to be at least 200 kpc for appreciable mass loss to occur over the history of a galaxy in a rich cluster. The calculations are then extended to include a halo population characterized by a high central velocity dispersion. In this case, it is found that the halo population of sufficiently large galaxies can be dispersed without appreciably affecting the main population. It is suggested that the missing mass of many clusters of galaxies may be located in an intergalactic sea of faint stars making up an envelope for the centrally located gE galaxies.

  16. High mortality of Red Sea zooplankton under ambient solar radiation.

    PubMed

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

    2014-01-01

    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

  17. High Mortality of Red Sea Zooplankton under Ambient Solar Radiation

    PubMed Central

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

    2014-01-01

    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

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

    NASA Astrophysics Data System (ADS)

    Lavaniegos, Bertha E.

    2009-12-01

    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.

  19. Internal models for interpreting neural population activity during sensorimotor control

    PubMed Central

    Golub, Matthew D; Yu, Byron M; Chase, Steven M

    2015-01-01

    To successfully guide limb movements, the brain takes in sensory information about the limb, internally tracks the state of the limb, and produces appropriate motor commands. It is widely believed that this process uses an internal model, which describes our prior beliefs about how the limb responds to motor commands. Here, we leveraged a brain-machine interface (BMI) paradigm in rhesus monkeys and novel statistical analyses of neural population activity to gain insight into moment-by-moment internal model computations. We discovered that a mismatch between subjects’ internal models and the actual BMI explains roughly 65% of movement errors, as well as long-standing deficiencies in BMI speed control. We then used the internal models to characterize how the neural population activity changes during BMI learning. More broadly, this work provides an approach for interpreting neural population activity in the context of how prior beliefs guide the transformation of sensory input to motor output. DOI: http://dx.doi.org/10.7554/eLife.10015.001 PMID:26646183

  20. Modeling of the population density flow for periodically migrating organisms

    NASA Astrophysics Data System (ADS)

    Tyutyunov, Yu. V.; Zagrebneva, A. D.; Surkov, F. A.; Azovsky, A. I.

    2010-02-01

    The Patlak-Keller-Segel population density flow equation was derived based on the hypotheses concerning the way of movement of the benthic organisms with periodic appearance in the water mass differing from the commonly used assumptions [12, 14, 15]. On the basis of these hypotheses, a time-discrete and space-continuous individual-based model of the population distribution in the environment with the continuous stimulus distribution was built. Using this model, we have shown that the analyzed taxis mechanism (i.e., the decrease of the migration frequency of the individuals from the bottom to the water mass with the increase of the stimulus concentration) leads to the aggregation of the organisms in the places with a high concentration of the stimulus. The population dynamics is well approximated by the continuous model in which the obtained Patlak-Keller-Segel flow equation is used. The numerical modeling has shown that the form of the dependence of the individual migration frequency to the water mass on the stimulus concentration (hyperbolic, exponential, linear, and sigmoid) slightly influences the pattern of the individuals’ distribution.

  1. Modelling food and population dynamics in honey bee colonies.

    PubMed

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

    2013-01-01

    Honey bees (Apis mellifera) are increasingly in demand as pollinators for various key agricultural food crops, but globally honey bee populations are in decline, and honey bee colony failure rates have increased. This scenario highlights a need to understand the conditions in which colonies flourish and in which colonies fail. To aid this investigation we present a compartment model of bee population dynamics to explore how food availability and bee death rates interact to determine colony growth and development. Our model uses simple differential equations to represent the transitions of eggs laid by the queen to brood, then hive bees and finally forager bees, and the process of social inhibition that regulates the rate at which hive bees begin to forage. We assume that food availability can influence both the number of brood successfully reared to adulthood and the rate at which bees transition from hive duties to foraging. The model predicts complex interactions between food availability and forager death rates in shaping colony fate. Low death rates and high food availability results in stable bee populations at equilibrium (with population size strongly determined by forager death rate) but consistently increasing food reserves. At higher death rates food stores in a colony settle at a finite equilibrium reflecting the balance of food collection and food use. When forager death rates exceed a critical threshold the colony fails but residual food remains. Our model presents a simple mathematical framework for exploring the interactions of food and forager mortality on colony fate, and provides the mathematical basis for more involved simulation models of hive performance. PMID:23667418

  2. Moving across the border: modeling migratory bat populations

    USGS Publications Warehouse

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

    2013-01-01

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

  3. Modelling Food and Population Dynamics in Honey Bee Colonies

    PubMed Central

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

    2013-01-01

    Honey bees (Apis mellifera) are increasingly in demand as pollinators for various key agricultural food crops, but globally honey bee populations are in decline, and honey bee colony failure rates have increased. This scenario highlights a need to understand the conditions in which colonies flourish and in which colonies fail. To aid this investigation we present a compartment model of bee population dynamics to explore how food availability and bee death rates interact to determine colony growth and development. Our model uses simple differential equations to represent the transitions of eggs laid by the queen to brood, then hive bees and finally forager bees, and the process of social inhibition that regulates the rate at which hive bees begin to forage. We assume that food availability can influence both the number of brood successfully reared to adulthood and the rate at which bees transition from hive duties to foraging. The model predicts complex interactions between food availability and forager death rates in shaping colony fate. Low death rates and high food availability results in stable bee populations at equilibrium (with population size strongly determined by forager death rate) but consistently increasing food reserves. At higher death rates food stores in a colony settle at a finite equilibrium reflecting the balance of food collection and food use. When forager death rates exceed a critical threshold the colony fails but residual food remains. Our model presents a simple mathematical framework for exploring the interactions of food and forager mortality on colony fate, and provides the mathematical basis for more involved simulation models of hive performance. PMID:23667418

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

    PubMed Central

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

    2012-01-01

    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 μl 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

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

    USGS Publications Warehouse

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

    1998-01-01

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

  6. Bayesian Modeling of Haplotype Effects in Multiparent Populations

    PubMed Central

    Zhang, Zhaojun; Wang, Wei; Valdar, William

    2014-01-01

    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

  7. A stage-based model of manatee population dynamics

    USGS Publications Warehouse

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

    2004-01-01

    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.

  8. Bayesian modeling of haplotype effects in multiparent populations.

    PubMed

    Zhang, Zhaojun; Wang, Wei; Valdar, William

    2014-09-01

    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

  9. Resource requirements of the Pacific leatherback turtle population.

    PubMed

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

    2012-01-01

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

  10. Resource Requirements of the Pacific Leatherback Turtle Population

    PubMed Central

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

    2012-01-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2008-08-01

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

  13. Synergistic Interaction between Selective Drugs in Cell Populations Models

    PubMed Central

    Doldán-Martelli, Victoria; Míguez, David G.

    2015-01-01

    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

  14. Encoding through patterns: regression tree-based neuronal population models.

    PubMed

    Haslinger, Robert; Pipa, Gordon; Lewis, Laura D; Nikolić, Danko; Williams, Ziv; Brown, Emery

    2013-08-01

    Although the existence of correlated spiking between neurons in a population is well known, the role such correlations play in encoding stimuli is not. We address this question by constructing pattern-based encoding models that describe how time-varying stimulus drive modulates the expression probabilities of population-wide spike patterns. The challenge is that large populations may express an astronomical number of unique patterns, and so fitting a unique encoding model for each individual pattern is not feasible. We avoid this combinatorial problem using a dimensionality-reduction approach based on regression trees. Using the insight that some patterns may, from the perspective of encoding, be statistically indistinguishable, the tree divisively clusters the observed patterns into groups whose member patterns possess similar encoding properties. These groups, corresponding to the leaves of the tree, are much smaller in number than the original patterns, and the tree itself constitutes a tractable encoding model for each pattern. Our formalism can detect an extremely weak stimulus-driven pattern structure and is based on maximizing the data likelihood, not making a priori assumptions as to how patterns should be grouped. Most important, by comparing pattern encodings with independent neuron encodings, one can determine if neurons in the population are driven independently or collectively. We demonstrate this method using multiple unit recordings from area 17 of anesthetized cat in response to a sinusoidal grating and show that pattern-based encodings are superior to those of independent neuron models. The agnostic nature of our clustering approach allows us to investigate encoding by the collective statistics that are actually present rather than those (such as pairwise) that might be presumed. PMID:23607564

  15. Integration of manatee life-history data and population modeling

    USGS Publications Warehouse

    Eberhardt, L.L.; O'Shea, Thomas J.

    1995-01-01

    Aerial counts and the number of deaths have been a major focus of attention in attempts to understand the population status of the Florida manatee (Trichechus manatus latirostris). Uncertainties associated with these data have made interpretation difficult. However, knowledge of manatee life-history attributes increased and now permits the development of a population model. We describe a provisional model based on the classical approach of Lotka. Parameters in the model are based on data from'other papers in this volume and draw primarily on observations from the Crystal River, Blue Spring, and Adantic Coast areas. The model estimates X (the finite rate ofincrease) at each study area, and application ofthe delta method provides estimates of variance components and partial derivatives ofX with respectto key input parameters (reproduction, adult survival, and early survival). In some study areas, only approximations of some parameters are available. Estimates of X and coefficients of variation (in parentheses) of manatees were 1.07 (0.009) in the Crystal River, 1.06 (0.012) at Blue Spring, and 1.01 (0.012) on the Atlantic Coast. Changing adult survival has a major effect on X. Early-age survival has the smallest effect. Bootstrap comparisons of population growth estimates from trend counts in the Crystal River and at Blue Spring and the reproduction and survival data suggest that the higher, observed rates from counts are probably not due to chance. Bootstrapping for variance estimates based on reproduction and survival data from manatees at Blue Spring and in the Crystal River provided estimates of X, adult survival, and rates of reproduction that were similar to those obtained by other methods. Our estimates are preliminary and suggestimprovements for future data collection and analysis. However, results support efforts to reduce mortality as the most effective means to promote the increased growth necessary for the eventual recovery of the Florida manatee population.

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

    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.

  17. The retreat of the less fit allele in a population-controlled model for population genetics.

    PubMed

    Weinberger, Hans F

    2014-04-01

    It is shown that the solutions of a single-locus diploid model with population control for the spatial and temporal interaction of the three genotypes approach a constant-density equilibrium in which only the more fit allele is present, provided the density dependent birth rate and fitnesses have certain properties. The speed at which this phenomenon spreads is at least as great as that of the linearization of the corresponding Fisher equation. A larger upper bound for this speed is also obtained. PMID:23549910

  18. Acoustic backscatter measurements with a 153 kHz ADCP in the northeastern Gulf of Mexico: determination of dominant zooplankton and micronekton scatterers

    NASA Astrophysics Data System (ADS)

    Ressler, Patrick H.

    2002-11-01

    A 153 kHz narrowband acoustic Doppler current profiler (ADCP) was used to measure volume backscattering strength ( Sv) during a deepwater oceanographic survey of cetacean and seabird habitat in the northeastern Gulf of Mexico. Sv was positively related to zooplankton and micronekton biomass (wet displacement volume) in 'sea-truth' net hauls made with a 1 m 2 Multiple Opening-Closing Net Environmental Sensing System (MOCNESS). A subset of these MOCNESS tows was used to explore the relationship between the numerical densities of various taxonomic categories of zooplankton and the ADCP backscatter signal. Crustaceans, small fish, and fragments of non-gas-bearing siphonophores in the net samples all showed significant, positive correlations with the acoustic signal, while other types of gelatinous zooplankton, pteropod and atlantid molluscs, and gas-filled siphonophore floats showed no significant correlation with Sv. Previously published acoustic scattering models for zooplankton were used to calculate expected scattering for several general zooplankton types and sizes for comparison with the field data. Even though gelatinous material often made up a large fraction of the total biomass, crustaceans, small fish, and pteropods were most likely the important scatterers. Since only crustacean and small fish densities were significantly correlated with Sv, it is suggested that Sv at 153 kHz can be used as a relative proxy for the abundance of these organisms in the Gulf of Mexico.

  19. Intraspecific Autochthonous and Allochthonous Resource Use by Zooplankton in a Humic Lake during the Transitions between Winter, Summer and Fall

    PubMed Central

    Berggren, Martin; Bergström, Ann-Kristin; Karlsson, Jan

    2015-01-01

    Seasonal patterns in assimilation of externally produced, allochthonous, organic matter into aquatic food webs are poorly understood, especially in brown-water lakes. We studied the allochthony (share biomass of terrestrial origin) in cladoceran, calanoid and cyclopoid micro-crustacean zooplankton from late winter to fall during two years in a small humic lake (Sweden). The use of allochthonous resources was important for sustaining a small population of calanoids in the water column during late winter. However, in summer the calanoids shifted to 100% herbivory, increasing their biomass several-fold by making efficient use of the pelagic primary production. In contrast, the cyclopoids and cladocerans remained at high levels of allochthony throughout the seasons, both groups showing the mean allochthony of 0.56 (range in mean 0.17-0.79 and 0.34-0.75, for the respective group, depending on model parameters). Our study shows that terrestrial organic matter can be an important resource for cyclopoids and cladocerans on an annual basis, forming a significant link between terrestrial organic matter and the higher trophic levels of the food web, but it can also be important for sustaining otherwise herbivorous calanoids during periods of low primary production in late winter. PMID:25764501

  20. A Stochastic Super-Exponential Growth Model for Population Dynamics

    NASA Astrophysics Data System (ADS)

    Avila, P.; Rekker, A.

    2010-11-01

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

  1. Population.

    ERIC Educational Resources Information Center

    International Planned Parenthood Federation, London (England).

    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,…

  2. 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)

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

    2012-08-01

    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.

  3. Does salinity change determine zooplankton variability in the saline Qarun Lake (Egypt)?

    NASA Astrophysics Data System (ADS)

    El-Shabrawy, Gamal M.; Anufriieva, Elena V.; Germoush, Mousa O.; Goher, Mohamed E.; Shadrin, Nickolai V.

    2015-11-01

    Zooplankton and 14 abiotic variables were studied during August 2011 at 10 stations in Lake Qarun, Egypt. Stations with the lowest salinity and highest nutrient concentrations and turbidity were close to the discharge of waters from the El-Bats and El-Wadi drainage systems. A total of 15 holozooplankton species were identified. The salinity in Lake Qarun increased and fluctuated since 1901: 12 g/L in 1901; 8.5 g/L in 1905; 12.0 g/L in 1922; 30.0 g/L in 1985; 38.7 g/L in 1994; 35.3 g/L in 2006, and 33.4 g/L in 2011. The mean concentration of nutrients (nitrate, nitrite and orthophosphate) gradually increased from 35, 0.16 and 0.38 µg/L, respectively, in 1953-1955 to 113, 16.4, and 30.26 µg/L in 2011. From 1999-2003 some decrease of species diversity occurred. Average total zooplankton density was 30 000 ind./m3 in 1974-1977; 356 125 ind./m3 in 1989; 534 000 ind./m3 in 1994-1995; from 965 000 to 1 452 000 ind./m3 in 2006, and 595 000 ind./m3 in 2011. A range of long-term summer salinity variability during the last decades was very similar to a range of salinity spatial variability in summer 2011. There is no significant correlation between zooplankton abundance and salinity in spatial and long-term changes. We conclude that salinity fluctuations since at least 1955 did not directly drive the changes of composition and abundance of zooplankton in the lake. A marine community had formed in the lake, and it continues to change. One of the main drivers of this change is a regular introduction and a pressure of alien species on the existent community. Eutrophication also plays an important role. The introduction of Mnemiopsis leidyi, first reported in 2014, may lead to a start of a new stage of the biotic changes in Lake Qarun, when eutrophication and the population dynamics of this ctenophore will be main drivers of the ecosystem change.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  5. A population model of chaparral vegetation response to frequent wildfires.

    PubMed

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

    2013-12-01

    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

  6. Modeling evolutionary games in populations with demographic structure.

    PubMed

    Li, Xiang-Yi; Giaimo, Stefano; Baudisch, Annette; Traulsen, Arne

    2015-09-01

    Classic life history models are often based on optimization algorithms, focusing on the adaptation of survival and reproduction to the environment, while neglecting frequency dependent interactions in the population. Evolutionary game theory, on the other hand, studies frequency dependent strategy interactions, but usually omits life history and the demographic structure of the population. Here we show how an integration of both aspects can substantially alter the underlying evolutionary dynamics. We study the replicator dynamics of strategy interactions in life stage structured populations. Individuals have two basic strategic behaviours, interacting in pairwise games. A player may condition behaviour on the life stage of its own, or that of the opponent, or the matching of life stages between both players. A strategy is thus defined as the set of rules that determines a player׳s life stage dependent behaviours. We show that the diversity of life stage structures and life stage dependent strategies can promote each other, and the stable frequency of basic strategic behaviours can deviate from game equilibrium in populations with life stage structures. PMID:26055649

  7. Richards-like two species population dynamics model.

    PubMed

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

    2014-12-01

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

  8. Modelling Lipid Competition Dynamics in Heterogeneous Protocell Populations

    PubMed Central

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

    2014-01-01

    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

  9. Modelling Lipid Competition Dynamics in Heterogeneous Protocell Populations

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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.

  10. CALIBRATING STELLAR POPULATION MODELS WITH MAGELLANIC CLOUD STAR CLUSTERS

    SciTech Connect

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

    2013-07-20

    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.

  11. [A model of the population growth of the Earth].

    PubMed

    Kapitsa, S P

    1995-01-01

    Of all global problems world population growth is the most significant one. World population drives all other global issues--of food and energy, resources and the environment. Although demographic data in a quantitative way does express the net result of our economic, social and cultural development, methods of demography can hardly suggest a more general, synergistic, approach to the study of long term growth. To describe this process in its past and project it into the foreseeable future a mathematical model is worked out. It treats the world population as an entity, seen as an open and evolving dynamic system. The approach is phenomenological and growth over very many generations is assumed to be self-similar. This invokes scaling and mathematically is expressed by a power law. Comparison with population data leads to a consistent description of growth by a hyperbolic growth curve valid from the Paleolithic up to the middle of this century. In terms of kinetics the growth rate is proportional to the square of the total number of people, rather than their number, as in the case of exponential growth. Thus nonlinear quadratic rate describes the sum outcome of all mechanisms that contribute to our growth and development in a collective interactive process. Taken without limits this pattern is divergent in the distant past and present, when it describes the population explosion. These singularities are cut off by introducing a characteristic time of 42 years,--the effective human life span--as the microscopic time constant in this phenomenology. The model gives an estimate of the beginning of human evolution congruent to 4.4 million years ago and of the total number of people who ever lived: congruent to 100 billion. In the scope of the model large scale cycles defined by history and anthropology are shown to be uniformly spaced in time on a logarithmic scale, expressing an inherent periodicity. On this scale, as we go into the past the rate of growth decreases when, finally in the early Paleolithic any appreciable change would take a million years to happen. As we approach the present this progression of cycles with the consequent compression of the time scale is now terminated by the demographic transition. This is seen as a singular epoch in all human development when the basic mode of world population growth is to change.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:7483750

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

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

    We extend the spectral range of our stellar population synthesis models based on the MILES and CaT empirical stellar spectral libraries. For this purpose, we combine these two libraries with the Indo-U.S. to construct composite stellar spectra to feed our models. The spectral energy distributions (SEDs) computed with these models and the originally published models are combined to construct composite SEDs for single-age, single-metallicity stellar populations (SSPs) covering the range λλ3465-9469 Å at moderately high and uniform resolution (full width at half-maximum = 2.51 Å). The colours derived from these SSP SEDs provide good fits to Galactic globular cluster data. We find that the colours involving redder filters are very sensitive to the initial mass function (IMF), as well as a number of features and molecular bands throughout the spectra. To illustrate the potential use of these models, we focus on the Na I doublet at 8200 Å and with the aid of the newly synthesized SSP model SEDs, we define a new IMF-sensitive index that is based on this feature, which overcomes various limitations from previous index definitions for low-velocity dispersion stellar systems. We propose an index-index diagram based on this feature and the neighbouring Ca II triplet at 8600 Å, to constrain the IMF if the age and [Na/Fe] abundance are known. Finally we also show a survey-oriented spectrophotometric application which evidences the accurate flux calibration of these models for carrying out reliable spectral fitting techniques. These models are available through our user-friendly website.

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

    USGS Publications Warehouse

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

    1998-01-01

    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.

  14. NUTRIENT REGENERATION BY ZOOPLANKTON IN SOUTHERN LAKE HURON

    EPA Science Inventory

    Rates of nutrient regeneration by zooplankton (micromolecule/mg dry wt/hr) in southern Lake Huron from April to August 1975 ranged from undetectable to 2.6 for total phosphorus (TP), undetected to 0.8 for total soluble phosphorus (TSP), undetectable to 0.12 for soluble reactive p...

  15. Correlates of Zooplankton Beta Diversity in Tropical Lake Systems

    PubMed Central

    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

    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

  16. 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...

  17. Evaluation of Zooplankton in Hatchery Diets for Channel Catfish Fry

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  18. Zooplankton and Karenia brevis in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

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

    2008-01-01

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

  19. Effect of various intake designs on zooplankton entrainment

    SciTech Connect

    Dycus, D.L.

    1983-03-01

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

  20. Zooplankton fecal pellets link fossil fuel and phosphate deposits

    SciTech Connect

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

    1981-05-22

    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.

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

    USGS Publications Warehouse

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

    2009-01-01

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

  2. Medaka: a promising model animal for comparative population genomics

    PubMed Central

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

    2009-01-01

    Background Within-species genome diversity has been best studied in humans. The international HapMap project has revealed a tremendous amount of single-nucleotide polymorphisms (SNPs) among humans, many of which show signals of positive selection during human evolution. In most of the cases, however, functional differences between the alleles remain experimentally unverified due to the inherent difficulty of human genetic studies. It would therefore be highly useful to have a vertebrate model with the following characteristics: (1) high within-species genetic diversity, (2) a variety of gene-manipulation protocols already developed, and (3) a completely sequenced genome. Medaka (Oryzias latipes) and its congeneric species, tiny fresh-water teleosts distributed broadly in East and Southeast Asia, meet these criteria. Findings Using Oryzias species from 27 local populations, we conducted a simple screening of nonsynonymous SNPs for 11 genes with apparent orthology between medaka and humans. We found medaka SNPs for which the same sites in human orthologs are known to be highly differentiated among the HapMap populations. Importantly, some of these SNPs show signals of positive selection. Conclusion These results indicate that medaka is a promising model system for comparative population genomics exploring the functional and adaptive significance of allelic differentiations. PMID:19426554

  3. Risk prediction models for hepatocellular carcinoma in different populations

    PubMed Central

    Ma, Xiao; Yang, Yang; Tu, Hong; Gao, Jing; Tan, Yu-Ting; Zheng, Jia-Li; Bray, Freddie; Xiang, Yong-Bing

    2016-01-01

    Hepatocellular carcinoma (HCC) is a malignant disease with limited therapeutic options due to its aggressive progression. It places heavy burden on most low and middle income countries to treat HCC patients. Nowadays accurate HCC risk predictions can help making decisions on the need for HCC surveillance and antiviral therapy. HCC risk prediction models based on major risk factors of HCC are useful and helpful in providing adequate surveillance strategies to individuals who have different risk levels. Several risk prediction models among cohorts of different populations for estimating HCC incidence have been presented recently by using simple, efficient, and ready-to-use parameters. Moreover, using predictive scoring systems to assess HCC development can provide suggestions to improve clinical and public health approaches, making them more cost-effective and effort-effective, for inducing personalized surveillance programs according to risk stratification. In this review, the features of risk prediction models of HCC across different populations were summarized, and the perspectives of HCC risk prediction models were discussed as well. PMID:27199512

  4. Optimization modeling to maximize population access to comprehensive stroke centers

    PubMed Central

    Branas, Charles C.; Kasner, Scott E.; Wolff, Catherine; Williams, Justin C.; Albright, Karen C.; Carr, Brendan G.

    2015-01-01

    Objective: The location of comprehensive stroke centers (CSCs) is critical to ensuring rapid access to acute stroke therapies; we conducted a population-level virtual trial simulating change in access to CSCs using optimization modeling to selectively convert primary stroke centers (PSCs) to CSCs. Methods: Up to 20 certified PSCs per state were selected for conversion to maximize the population with 60-minute CSC access by ground and air. Access was compared across states based on region and the presence of state-level emergency medical service policies preferentially routing patients to stroke centers. Results: In 2010, there were 811 Joint Commission PSCs and 0 CSCs in the United States. Of the US population, 65.8% had 60-minute ground access to PSCs. After adding up to 20 optimally located CSCs per state, 63.1% of the US population had 60-minute ground access and 86.0% had 60-minute ground/air access to a CSC. Across states, median CSC access was 55.7% by ground (interquartile range 35.7%–71.5%) and 85.3% by ground/air (interquartile range 59.8%–92.1%). Ground access was lower in Stroke Belt states compared with non–Stroke Belt states (32.0% vs 58.6%, p = 0.02) and lower in states without emergency medical service routing policies (52.7% vs 68.3%, p = 0.04). Conclusion: Optimal system simulation can be used to develop efficient care systems that maximize accessibility. Under optimal conditions, a large proportion of the US population will be unable to access a CSC within 60 minutes. PMID:25740858

  5. Modeling the population dynamics of phytoplankton in lacustrine ecosystems

    NASA Astrophysics Data System (ADS)

    Leiterman, Terry Jo

    2011-11-01

    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.

  6. Exact Solution of Population Redistributions in a Migration Model

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    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 (kαi) and j (kβj), respectively. Both analytical calculation and numerical simulation show that the population distribution of communities in stationary states is determined by the parameters α and β. The distribution is widely homogeneous with a characteristic size if α > β. Whereas, for α < β, the distribution is highly heterogeneous with the emergence of condensing phenomenon. Between the two regimes, α = β, the distribution gradually shifts from the nonmonotonous (α < 0) to scale-free (α > 0).

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

    NASA Astrophysics Data System (ADS)

    Omori, Katsunori; Oguchi, Mitsuo; Takeuchi, Toshio

    2006-01-01

    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.

  8. Modelling multi-pulse population dynamics from ultrafast spectroscopy.

    PubMed

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

    2011-01-01

    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

  9. Modelling Multi-Pulse Population Dynamics from Ultrafast Spectroscopy

    PubMed Central

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

    2011-01-01

    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

  10. Towards a continuous population model for natural language vowel shift.

    PubMed

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

    2013-09-01

    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

  11. Monitored and modeled coral population dynamics and the refuge concept.

    PubMed

    Riegl, B; Purkis, S J; Keck, J; Rowlands, G P

    2009-01-01

    With large-scale impacts on coral reefs due to global climatic change projected to increase dramatically, and suitability of many areas for reef growth projected to decrease, the question arises whether particular settings might serve as refugia that can maintain higher coral populations than surrounding areas. We examine this hypothesis on a small, local scale in Honduras, western Caribbean. Dense coral thickets containing high numbers of the endangered coral Acropora cervicornis occur on offshore banks while being rare on the fringing reef on nearby Roatán. Geomorphological setting and community dynamics were evaluated and monitored from 1996 to 2005. A model of population dynamics was developed to test assumptions derived from monitoring. Coral cover on the fringing reef declined in 1998 from >30% to <20%, but the banks maintained areas of very dense coral cover (32% cover by A. cervicornis on the banks but <1% on the fringing reef). Bathymetry from satellite images showed the banks to be well-separated from the fringing reef, making asexual connectivity between banks and fringing reef impossible but protecting the banks from direct land-runoff during storms. Exposure to SE tradewinds also causes good flushing. Only four A. cervicornis recruits were recorded on the fringing reef over 6 years. Runoff associated with hurricanes caused greater mortality than did bleaching in 1998 and 2005 on the fringing reef, but not on the banks. Since 1870, our analysis suggests that corals on the banks may have been favored during 17 runoff events associated with tropical depressions and storms and potentially also during five bleaching events, but this is more uncertain. Our model suggests that under this disturbance regime, the banks will indeed maintain higher coral populations than the fringing reef and supports the assumption that offshore banks could serve as refugia with the capacity to subsidize depleted mainland populations. PMID:19100585

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

    SciTech Connect

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

    1988-01-01

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

  13. Distinguishing Antimicrobial Models with Different Resistance Mechanisms via Population Pharmacodynamic Modeling.

    PubMed

    Jacobs, Matthieu; Grégoire, Nicolas; Couet, William; Bulitta, Jurgen B

    2016-03-01

    Semi-mechanistic pharmacokinetic-pharmacodynamic (PK-PD) modeling is increasingly used for antimicrobial drug development and optimization of dosage regimens, but systematic simulation-estimation studies to distinguish between competing PD models are lacking. This study compared the ability of static and dynamic in vitro infection models to distinguish between models with different resistance mechanisms and support accurate and precise parameter estimation. Monte Carlo simulations (MCS) were performed for models with one susceptible bacterial population without (M1) or with a resting stage (M2), a one population model with adaptive resistance (M5), models with pre-existing susceptible and resistant populations without (M3) or with (M4) inter-conversion, and a model with two pre-existing populations with adaptive resistance (M6). For each model, 200 datasets of the total bacterial population were simulated over 24h using static antibiotic concentrations (256-fold concentration range) or over 48h under dynamic conditions (dosing every 12h; elimination half-life: 1h). Twelve-hundred random datasets (each containing 20 curves for static or four curves for dynamic conditions) were generated by bootstrapping. Each dataset was estimated by all six models via population PD modeling to compare bias and precision. For M1 and M3, most parameter estimates were unbiased (<10%) and had good imprecision (<30%). However, parameters for adaptive resistance and inter-conversion for M2, M4, M5 and M6 had poor bias and large imprecision under static and dynamic conditions. For datasets that only contained viable counts of the total population, common statistical criteria and diagnostic plots did not support sound identification of the true resistance mechanism. Therefore, it seems advisable to quantify resistant bacteria and characterize their MICs and resistance mechanisms to support extended simulations and translate from in vitro experiments to animal infection models and ultimately patients. PMID:26967893

  14. Distinguishing Antimicrobial Models with Different Resistance Mechanisms via Population Pharmacodynamic Modeling

    PubMed Central

    Jacobs, Matthieu; Grégoire, Nicolas; Couet, William; Bulitta, Jurgen B.

    2016-01-01

    Semi-mechanistic pharmacokinetic-pharmacodynamic (PK-PD) modeling is increasingly used for antimicrobial drug development and optimization of dosage regimens, but systematic simulation-estimation studies to distinguish between competing PD models are lacking. This study compared the ability of static and dynamic in vitro infection models to distinguish between models with different resistance mechanisms and support accurate and precise parameter estimation. Monte Carlo simulations (MCS) were performed for models with one susceptible bacterial population without (M1) or with a resting stage (M2), a one population model with adaptive resistance (M5), models with pre-existing susceptible and resistant populations without (M3) or with (M4) inter-conversion, and a model with two pre-existing populations with adaptive resistance (M6). For each model, 200 datasets of the total bacterial population were simulated over 24h using static antibiotic concentrations (256-fold concentration range) or over 48h under dynamic conditions (dosing every 12h; elimination half-life: 1h). Twelve-hundred random datasets (each containing 20 curves for static or four curves for dynamic conditions) were generated by bootstrapping. Each dataset was estimated by all six models via population PD modeling to compare bias and precision. For M1 and M3, most parameter estimates were unbiased (<10%) and had good imprecision (<30%). However, parameters for adaptive resistance and inter-conversion for M2, M4, M5 and M6 had poor bias and large imprecision under static and dynamic conditions. For datasets that only contained viable counts of the total population, common statistical criteria and diagnostic plots did not support sound identification of the true resistance mechanism. Therefore, it seems advisable to quantify resistant bacteria and characterize their MICs and resistance mechanisms to support extended simulations and translate from in vitro experiments to animal infection models and ultimately patients. PMID:26967893

  15. Model of two infectious diseases in nettle caterpillar population

    NASA Astrophysics Data System (ADS)

    Firdausi, F. Z.; Nuraini, N.

    2016-04-01

    Palm oil is a vital commodity to the economy of Indonesia. The area of oil palm plantations in Indonesia has increased from year to year. However, the effectiveness of palm oil production is reduced by pest infestation. One of the pest which often infests oil palm plantations is nettle caterpillar. The pest control used in this study is biological control, viz. biological agents given to oil palm trees. This paper describes a mathematical model of two infectious diseases in nettle caterpillar population. The two infectious diseases arise due to two biological agents, namely Bacillus thuringiensis bacterium and parasite which usually attack nettle caterpillars. The derivation of the model constructed in this paper is obtained from ordinary differential equations without time delay. The equilibrium points are analyzed. Two of three equilibrium points are stable if the Routh-Hurwitz criteria are fulfilled. In addition, this paper also presents the numerical simulation of the model which has been constructed.

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

    PubMed

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

    2015-01-01

    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

  17. Modeling Refuge Effect of Submerged Macrophytes in Lake System.

    PubMed

    Lv, Dongyu; Fan, Meng; Kang, Yun; Blanco, Krystal

    2016-04-01

    This paper considers a significant problem in biological control of algae issue in ecological environment. A four-dimensional dynamic model is carefully formulated to characterize the interactions among phytoplankton, submerged macrophyte, zooplankton, and general fish class in a lake ecosystem. The predation relationship is modeled by Beddington-DeAngelis functional responses derived from the classical Holling time budget arguments. Qualitative analyses of the global dynamics show that the system can generate very rich dynamics with potentially 10 different equilibria and several bistable scenarios. We perform analysis on the existence and local stability of equilibria and explore the refuge effect of macrophyte on the zooplankton with numerical simulations on aquatic ecosystems. We also discuss effective methods of biological control used to restrain the increase of phytoplankton. Our study shows the proposed model could have rich and complex dynamics including but not limited to bistable and chaotic phenomenon. Numerical simulation results demonstrate that both the refuge constant and the density of the macrophytes are two key factors where refuge effects take place. In addition, the intraspecific competition between the macrophyte and the phytoplankton can also affect the macrophyte's refuge effect. Our analytical and simulation results suggest that macrophytes provide structure and shelter against predation for zooplankton such that it could restore the zooplankton population, and that planting macrophyte properly might achieve the purpose of controlling algae growth. PMID:27055658

  18. Late stages of stellar evolution in population models

    NASA Astrophysics Data System (ADS)

    Maraston, Claudia

    2015-04-01

    My contribution to Roger's celebration symposium focuses on the treatment of late stellar evolutionary phases in stellar population models, reviewing the state of art and discussing some very recent developments, ranging from local stellar clusters up to distant galaxies at high redshift. I shall focus in particular on the Thermally Pulsating Asymptotic Giant Branch, about which a vivid discussion has been ongoing since a few years. I shall present renewed evidence in favour of a sizable contribution from this phase for matching the observed spectral energy distribution of distant massive galaxies. I shall also discuss the possible reasons why such a conclusion has been controversial in the recent literature. Stellar population models are the magic tool to shape the physics of galaxies out of their observed light, and enter virtually all papers presented at this symposium. In a collective effort to properly treat all relevant aspects of the modelling, we split the discussion into six contributions given by experts in the field, as our present to Roger and his outstanding career.

  19. The model of fungal population dynamics affected by nystatin

    NASA Astrophysics Data System (ADS)

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

    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

  20. Mathematical modeling of glassy-winged sharpshooter population.

    PubMed

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

    2014-06-01

    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

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

    SciTech Connect

    Cowan, J.H. ); Rose, K.A. ); Rutherford, E.S.; Houde, E.D. )

    1993-05-01

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

  2. 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)

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

    2005-09-01

    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 μm) 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 μm 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 μm, 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.

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

    USGS Publications Warehouse

    Verschuren, D.; Marnell, L.F.

    1997-01-01

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

  4. Linking population-level models with growing networks: A class of epidemic models

    NASA Astrophysics Data System (ADS)

    Breban, Romulus; Vardavas, Raffaele; Blower, Sally

    2005-10-01

    We introduce a class of growing network models that are directly applicable to epidemiology. We show how to construct a growing network model (individual-level model) that generates the same epidemic-level outcomes as a population-level ordinary differential equation (ODE) model. For concreteness, we analyze the susceptible-infected (SI) ODE model of disease invasion. First, we give an illustrative example of a growing network whose population-level variables are compatible with those of this ODE model. Second, we demonstrate that a growing network model can be found that is equivalent to the Crump-Mode-Jagers (CMJ) continuous-time branching process of the SI ODE model of disease invasion. We discuss the computational advantages that our growing network model has over the CMJ branching process.

  5. MULTISCALE MODELS OF TAXIS-DRIVEN PATTERNING IN BACTERIAL POPULATIONS

    PubMed Central

    XUE, CHUAN; OTHMER, HANS G.

    2009-01-01

    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

  6. Spring bloom dynamics and zooplankton biomass response on the US Northeast Continental Shelf

    NASA Astrophysics Data System (ADS)

    Friedland, Kevin D.; Leaf, Robert T.; Kane, Joe; Tommasi, Desiree; Asch, Rebecca G.; Rebuck, Nathan; Ji, Rubao; Large, Scott I.; Stock, Charles; Saba, Vincent S.

    2015-07-01

    The spring phytoplankton bloom on the US Northeast Continental Shelf is a feature of the ecosystem production cycle that varies annually in timing, spatial extent, and magnitude. To quantify this variability, we analyzed remotely-sensed ocean color data at two spatial scales, one based on ecologically defined sub-units of the ecosystem (production units) and the other on a regular grid (0.5°). Five units were defined: Gulf of Maine East and West, Georges Bank, and Middle Atlantic Bight North and South. The units averaged 47×103 km2 in size. The initiation and termination of the spring bloom were determined using change-point analysis with constraints on what was identified as a bloom based on climatological bloom patterns. A discrete spring bloom was detected in most years over much of the western Gulf of Maine production unit. However, bloom frequency declined in the eastern Gulf of Maine and transitioned to frequencies as low as 50% along the southern flank of the Georges Bank production unit. Detectable spring blooms were episodic in the Middle Atlantic Bight production units. In the western Gulf of Maine, bloom duration was inversely related to bloom start day; thus, early blooms tended to be longer lasting and larger magnitude blooms. We view this as a phenological mismatch between bloom timing and the "top-down" grazing pressure that terminates a bloom. Estimates of secondary production were available from plankton surveys that provided spring indices of zooplankton biovolume. Winter chlorophyll biomass had little effect on spring zooplankton biovolume, whereas spring chlorophyll biomass had mixed effects on biovolume. There was evidence of a "bottom up" response seen on Georges Bank where spring zooplankton biovolume was positively correlated with the concentration of chlorophyll. However, in the western Gulf of Maine, biovolume was uncorrelated with chlorophyll concentration, but was positively correlated with bloom start and negatively correlated with magnitude. This observation is consistent with both a "top-down" mechanism of control of the bloom and a "bottom-up" effect of bloom timing on zooplankton grazing. Our inability to form a consistent model of these relationships across adjacent systems underscores the need for further research.

  7. Mathematical model of temephos resistance in Aedes aegypti mosquito population

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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.

  8. Estimating population trends with a linear model: technical comments

    USGS Publications Warehouse

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

    2004-01-01

    Controversy has sometimes arisen over whether there is a need to accommodate the limitations of survey design in estimating population change from the count data collected in bird surveys. Analyses of surveys such as the North American Breeding Bird Survey (BBS) can be quite complex; it is natural to ask if the complexity is necessary, or whether the statisticians have run amok. Bart et al. (2003) propose a very simple analysis involving nothing more complicated than simple linear regression, and contrast their approach with model-based procedures. We review the assumptions implicit to their proposed method, and document that these assumptions are unlikely to be valid for surveys such as the BBS. One fundamental limitation of a purely design-based approach is the absence of controls for factors that influence detection of birds at survey sites. We show that failure to model observer effects in survey data leads to substantial bias in estimation of population trends from BBS data for the 20 species that Bart et al. (2003) used as the basis of their simulations. Finally, we note that the simulations presented in Bart et al. (2003) do not provide a useful evaluation of their proposed method, nor do they provide a valid comparison to the estimating- equations alternative they consider.

  9. Modelling Oyster Population Response to Variation in Freshwater Input

    NASA Astrophysics Data System (ADS)

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

    2000-05-01

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

  10. Predicting extinction risks under climate change: coupling stochastic population models with dynamic bioclimatic habitat models.

    PubMed

    Keith, David A; Akçakaya, H Resit; Thuiller, Wilfried; Midgley, Guy F; Pearson, Richard G; Phillips, Steven J; Regan, Helen M; Araújo, Miguel B; Rebelo, Tony G

    2008-10-23

    Species responses to climate change may be influenced by changes in available habitat, as well as population processes, species interactions and interactions between demographic and landscape dynamics. Current methods for assessing these responses fail to provide an integrated view of these influences because they deal with habitat change or population dynamics, but rarely both. In this study, we linked a time series of habitat suitability models with spatially explicit stochastic population models to explore factors that influence the viability of plant species populations under stable and changing climate scenarios in South African fynbos, a global biodiversity hot spot. Results indicate that complex interactions between life history, disturbance regime and distribution pattern mediate species extinction risks under climate change. Our novel mechanistic approach allows more complete and direct appraisal of future biotic responses than do static bioclimatic habitat modelling approaches, and will ultimately support development of more effective conservation strategies to mitigate biodiversity losses due to climate change. PMID:18664424

  11. Sexual Reproduction in a Simple Growth Population Model

    NASA Astrophysics Data System (ADS)

    Lemos, Carlos Gentil Oro; Santos, Marcio

    2012-05-01

    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.

  12. [Population surveys as management tools and health care models].

    PubMed

    Andrade, Flávia Reis de; Narvai, Paulo Capel

    2013-12-01

    The article briefly systematizes health care models, emphasizes the role of population surveys as a management tool and analyzes the specific case of the Brazilian Oral Health Survey (SBBrasil 2010) and its contribution to the consolidation process of health care models consistent with the principles of the Sistema Único de Saúde (SUS, Public Health Care System). While in legal terms SUS corresponds to a health care model, in actual practice the public policy planning and health action, the system gives rise to a care model which is not the result of legal texts or theoretical formulations, but rather the praxis of the personnel involved. Bearing in mind that the management of day-to-day health affairs is a privileged space for the production and consolidation of health care models, it is necessary to stimulate and support the development of technical and operational skills which are different from those required for the management of care related to individual demands. PMID:24626592

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

    PubMed Central

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

    2013-01-01

    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

  14. 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...

  15. Comparison of multifrequency acoustic and in situ measurements of zooplankton abundances in Knight Inlet, British Columbia.

    PubMed

    Trevorrow, Mark V; Mackas, David L; Benfield, Mark C

    2005-06-01

    An investigation of midwater zooplankton aggregations in a coastal fjord was conducted in November 2002. This study focused on quantitative comparisons between a calibrated, three-frequency (38, 120, and 200 kHz) vessel-based echo-sounder, a multinet towed zooplankton sampler (BIONESS), and a high-resolution underwater camera (ZOOVIS). Daytime layers of euphausiids and amphipods near 70-90-m depth were observed in lower parts of the inlet, especially concentrated by tidal flows around a sill. Quantitative backscatter measurements of euphausiids and amphipods, combined with in situ size and abundance estimates, and using an assumed tilt-angle distribution, were in agreement with averaged fluid-cylinder scattering models produced by Stanton and Chu [ICES J. Mar. Sci. 57, 793-807, (2000)]. Acoustic measurements of physonect siphonophores in the upper inlet were found to have a strong 38-kHz scattering strength, in agreement with a damped bubble scattering model using a diameter of 0.4 mm. In relatively dense euphausiid layers, ZOOVIS abundance estimates were found to be a factor of 2 to 4 higher than the acoustic estimates, potentially due to deviations from assumed euphausiid orientation. Nocturnal near-surface euphausiid scattering exhibited a strong (15 dB) and rapid (seconds) sensitivity to vessel lights, interpreted as due to changing animal orientation. PMID:16018461

  16. Yunnan-III models for evolutionary population synthesis

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

    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.

  17. Nuisance Source Population Modeling for Radiation Detection System Analysis

    SciTech Connect

    Sokkappa, P; Lange, D; Nelson, K; Wheeler, R

    2009-10-05

    A major challenge facing the prospective deployment of radiation detection systems for homeland security applications is the discrimination of radiological or nuclear 'threat sources' from radioactive, but benign, 'nuisance sources'. Common examples of such nuisance sources include naturally occurring radioactive material (NORM), medical patients who have received radioactive drugs for either diagnostics or treatment, and industrial sources. A sensitive detector that cannot distinguish between 'threat' and 'benign' classes will generate false positives which, if sufficiently frequent, will preclude it from being operationally deployed. In this report, we describe a first-principles physics-based modeling approach that is used to approximate the physical properties and corresponding gamma ray spectral signatures of real nuisance sources. Specific models are proposed for the three nuisance source classes - NORM, medical and industrial. The models can be validated against measured data - that is, energy spectra generated with the model can be compared to actual nuisance source data. We show by example how this is done for NORM and medical sources, using data sets obtained from spectroscopic detector deployments for cargo container screening and urban area traffic screening, respectively. In addition to capturing the range of radioactive signatures of individual nuisance sources, a nuisance source population model must generate sources with a frequency of occurrence consistent with that found in actual movement of goods and people. Measured radiation detection data can indicate these frequencies, but, at present, such data are available only for a very limited set of locations and time periods. In this report, we make more general estimates of frequencies for NORM and medical sources using a range of data sources such as shipping manifests and medical treatment statistics. We also identify potential data sources for industrial source frequencies, but leave the task of estimating these frequencies for future work. Modeling of nuisance source populations is only useful if it helps in understanding detector system performance in real operational environments. Examples of previous studies in which nuisance source models played a key role are briefly discussed. These include screening of in-bound urban traffic and monitoring of shipping containers in transit to U.S. ports.

  18. Population effects of increased climate variation

    PubMed Central

    Drake, John M

    2005-01-01

    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

  19. Population pharmacokinetic modeling of isoniazid, rifampin, and pyrazinamide.

    PubMed Central

    Peloquin, C A; Jaresko, G S; Yong, C L; Keung, A C; Bulpitt, A E; Jelliffe, R W

    1997-01-01

    Isoniazid (INH), rifampin (RIF), and pyrazinamide (PZA) are the most important drugs for the treatment of tuberculosis (TB). The pharmacokinetics of all three drugs in the plasma of 24 healthy males were studied as part of a randomized cross-over phase I study of two dosage forms. Subjects ingested single doses of INH at 250 mg, RIF at 600 mg, and PZA at 1,500 mg. Plasma was collected for 36 h and was assayed by high-performance liquid chromatography. The data were analyzed by noncompartmental, iterative two-stage maximum a posteriori probability Bayesian (IT2B) and nonparametric expectation maximization (NPEM) population modeling methods. Fast and slow acetylators of INH had median peak concentrations in plasma (C[max]) of 2.44 and 3.64 microg/ml, respectively, both of which occurred at 1.0 h postdose (time of maximum concentrations of drugs in plasma [T(max)]), with median elimination half-lives (t1/2) of 1.2 and 3.3 h, respectively (by the NPEM method). RIF produced a median C(max) of 11.80 microg/ml, a T(max) of 1.0 h, and a t1/2 of 3.4 h. PZA produced a median C(max) of 28.80 microg/ml, a T(max) of 1.0 h, and a t1/2 of 10.0 h. The pharmacokinetic behaviors of INH, RIF, and PZA were well described by the three methods used. These models can serve as benchmarks for comparison with models for other populations, such as patients with TB or TB with AIDS. PMID:9420037

  20. A dynamic urban air pollution population exposure assessment study using model and population density data derived by mobile phone traffic

    NASA Astrophysics Data System (ADS)

    Gariazzo, Claudio; Pelliccioni, Armando; Bolignano, Andrea

    2016-04-01

    A dynamic city-wide air pollution exposure assessment study has been carried out for the urban population of Rome, Italy, by using time resolved population distribution maps, derived by mobile phone traffic data, and modelled air pollutants (NO2, O3 and PM2.5) concentrations obtained by an integrated air dispersion modelling system. More than a million of persons were tracked during two months (March and April 2015) for their position within the city and its surroundings areas, with a time resolution of 15 min and mapped over an irregular grid system with a minimum resolution of 0.26 × 0.34 Km2. In addition, demographics information (as gender and age ranges) were available in a separated dataset not connected with the total population one. Such BigData were matched in time and space with air pollution model results and then used to produce hourly and daily resolved cumulative population exposures during the studied period. A significant mobility of population was identified with higher population densities in downtown areas during daytime increasing of up to 1000 people/Km2 with respect to nigh-time one, likely produced by commuters, tourists and working age population. Strong variability (up to ±50% for NO2) of population exposures were detected as an effect of both mobility and time/spatial changing in pollutants concentrations. A comparison with the correspondent stationary approach based on National Census data, allows detecting the inability of latter in estimating the actual variability of population exposure. Significant underestimations of the amount of population exposed to daily PM2.5 WHO guideline was identified for the Census approach. Very small differences (up to a few μg/m3) on exposure were detected for gender and age ranges population classes.

  1. Changes in the abundance and composition of zooplankton from the ports of Mumbai, India.

    PubMed

    Gaonkar, Chetan A; Krishnamurthy, Venkat; Anil, Arga Chandrashekar

    2010-09-01

    Zooplankton abundance, biomass, and composition from the ports of Mumbai, India, were studied by selecting 14 stations in and around the area during three different periods between 2001 and 2002 (Nov 01, Apr 02, and Oct 02). The results are compared with the records available since the 1940s. Copepod species such as Canthocalanus sp., Paracalanus arabiensis, Cosmocalanus sp., Euterpina acutifrons, Nannocalanus minor, and Tortanus sp. which were not reported in the earlier studies were observed during the present investigation. Purely herbivorous forms like Nannocalanus minor, Paracalanus sp., and Temora discaudata were in reduced abundance during Apr 02 sampling which was coupled with reduction in the diatom population. Whereas increased abundance of some carnivorous and omnivorous forms during Apr 02 sampling can be related to the changes in the food web dynamics. PMID:19649716

  2. Toward population management in an integrated care model.

    PubMed

    Maddux, Franklin W; McMurray, Stephen; Nissenson, Allen R

    2013-04-01

    Under the Patient Protection and Affordable Care Act of 2010, accountable care organizations (ACOs) will be the primary mechanism for achieving the dual goals of high-quality patient care at managed per capita costs. To achieve these goals in the newly emerging health care environment, the nephrology community must plan for and direct integrated delivery and coordination of renal care, focusing on population management. Even though the ESRD patient population is a complex group with comorbid conditions that may confound integration of care, the nephrology community has unique experience providing integrated care through ACO-like programs. Specifically, the recent ESRD Management Demonstration Project sponsored by the Centers for Medicare & Medicaid Services and the current ESRD Prospective Payment System with it Quality Incentive Program have demonstrated that integrated delivery of renal care can be accomplished in a manner that provides improved clinical outcomes with some financial margin of savings. Moving forward, integrated renal care will probably be linked to provider performance and quality outcomes measures, and clinical integration initiatives will share several common elements, namely performance-based payment models, coordination of communication via health care information technology, and development of best practices for care coordination and resource utilization. Integration initiatives must be designed to be measured and evaluated, and, consistent with principles of continuous quality improvement, each initiative will provide for iterative improvements of the initiative. PMID:23539229

  3. Toward population management in an integrated care model.

    PubMed

    Maddux, Franklin W; McMurray, Stephen; Nissenson, Allen R

    2013-01-01

    Under the Patient Protection and Affordable Care Act of 2010, accountable care organizations (ACOs) will be the primary mechanism for achieving the dual goals of high-quality patient care at managed per capita costs. To achieve these goals in the newly emerging health care environment, the nephrology community must plan for and direct integrated delivery and coordination of renal care, focusing on population management. Even though the ESRD patient population is a complex group with comorbid conditions that may confound integration of care, the nephrology community has unique experience providing integrated care through ACO-like programs. Specifically, the recent ESRD Management Demonstration Project sponsored by the Centers for Medicare & Medicaid Services and the current ESRD Prospective Payment System with it Quality Incentive Program have demonstrated that integrated delivery of renal care can be accomplished in a manner that provides improved clinical outcomes with some financial margin of savings. Moving forward, integrated renal care will probably be linked to provider performance and quality outcomes measures, and clinical integration initiatives will share several common elements, namely performance-based payment models, coordination of communication via health care information technology, and development of best practices for care coordination and resource utilization. Integration initiatives must be designed to be measured and evaluated, and, consistent with principles of continuous quality improvement, each initiative will provide for iterative improvements of the initiative. PMID:24496184

  4. Explaining the Linguistic Diversity of Sahul Using Population Models

    PubMed Central

    Reesink, Ger; Singer, Ruth; Dunn, Michael

    2009-01-01

    The region of the ancient Sahul continent (present day Australia and New Guinea, and surrounding islands) is home to extreme linguistic diversity. Even apart from the huge Austronesian language family, which spread into the area after the breakup of the Sahul continent in the Holocene, there are hundreds of languages from many apparently unrelated families. On each of the subcontinents, the generally accepted classification recognizes one large, widespread family and a number of unrelatable smaller families. If these language families are related to each other, it is at a depth which is inaccessible to standard linguistic methods. We have inferred the history of structural characteristics of these languages under an admixture model, using a Bayesian algorithm originally developed to discover populations on the basis of recombining genetic markers. This analysis identifies 10 ancestral language populations, some of which can be identified with clearly defined phylogenetic groups. The results also show traces of early dispersals, including hints at ancient connections between Australian languages and some Papuan groups (long hypothesized, never before demonstrated). Systematic language contact effects between members of big phylogenetic groups are also detected, which can in some cases be identified with a diffusional or substrate signal. Most interestingly, however, there remains striking evidence of a phylogenetic signal, with many languages showing negligible amounts of admixture. PMID:19918360

  5. Complex Transition to Cooperative Behavior in a Structured Population Model

    PubMed Central

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

    2012-01-01

    Cooperation plays an important role in the evolution of species and human societies. The understanding of the emergence and persistence of cooperation in those systems is a fascinating and fundamental question. Many mechanisms were extensively studied and proposed as supporting cooperation. The current work addresses the role of migration for the maintenance of cooperation in structured populations. This problem is investigated in an evolutionary perspective through the prisoner's dilemma game paradigm. It is found that migration and structure play an essential role in the evolution of the cooperative behavior. The possible outcomes of the model are extinction of the entire population, dominance of the cooperative strategy and coexistence between cooperators and defectors. The coexistence phase is obtained in the range of large migration rates. It is also verified the existence of a critical level of structuring beyond that cooperation is always likely. In resume, we conclude that the increase in the number of demes as well as in the migration rate favor the fixation of the cooperative behavior. PMID:22761736

  6. Zooplankton fecal pellets link fossil fuel and phosphate deposits

    USGS Publications Warehouse

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

    1981-01-01

    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.

  7. Phytoplankton, not allochthonous carbon, sustains herbivorous zooplankton production

    PubMed Central

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

    2009-01-01

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

  8. Flow disturbances generated by feeding and swimming zooplankton

    PubMed Central

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

    2014-01-01

    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

  9. Ingestion of Microplastics by Zooplankton in the Northeast Pacific Ocean.

    PubMed

    Desforges, Jean-Pierre W; Galbraith, Moira; Ross, Peter S

    2015-10-01

    Microplastics are increasingly recognized as being widespread in the world's oceans, but relatively little is known about ingestion by marine biota. In light of the potential for microplastic fibers and fragments to be taken up by small marine organisms, we examined plastic ingestion by two foundation species near the base of North Pacific marine food webs, the calanoid copepod Neocalanus cristatus and the euphausiid Euphausia pacifia. We developed an acid digestion method to assess plastic ingestion by individual zooplankton and detected microplastics in both species. Encounter rates resulting from ingestion were 1 particle/every 34 copepods and 1/every 17 euphausiids (euphausiids > copepods; p = 0.01). Consistent with differences in the size selection of food between these two zooplankton species, the ingested particle size was greater in euphausiids (816 ± 108 μm) than in copepods (556 ± 149 μm) (p = 0.014). The contribution of ingested microplastic fibres to total plastic decreased with distance from shore in euphausiids (r (2) = 70, p = 0.003), corresponding to patterns in our previous observations of microplastics in seawater samples from the same locations. This first evidence of microplastic ingestion by marine zooplankton indicate that species at lower trophic levels of the marine food web are mistaking plastic for food, which raises fundamental questions about potential risks to higher trophic level species. One concern is risk to salmon: We estimate that consumption of microplastic-containing zooplankton will lead to the ingestion of 2-7 microplastic particles/day by individual juvenile salmon in coastal British Columbia, and ≤91 microplastic particles/day in returning adults. PMID:26066061

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

    PubMed

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

    2012-02-01

    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

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

    PubMed

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

    2014-06-15

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

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

    PubMed Central

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

    2012-01-01

    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

  13. Zooplankton distribution as related to summer hydrographic conditions in Onslow Bay, North Carolina

    SciTech Connect

    Paffenhoefer, G.A.

    1980-01-01

    Zooplankton concentration and composition was related to hydrographic parameters in Onslow Bay, NC. During summer the hydrography of Onslow Bay is often characterized by the presence of nutrient-rich Gulf Stream waters. These originate from greater depths of the Gulf Stream, intrude at subsurface depths, frequently strand in the Bay and have high concentrations of particulate matter and chlorophyll a. Since such water masses can maintain their integrity for up to one month, temporal changes in phyto- and zooplankton communities may be followed. This paper describes the concentration, composition and distribution of abundant zooplankton taxa from summer 1976. Zooplankton distribution was affected by hydrography. Zooplankton biomass and composition indicate relatively high production of and low predation rates on zooplankton in intruded waters.

  14. Zooplankton distribution as related to summer hydrographic conditions in Onslow Bay, North Carolina

    SciTech Connect

    Paffenhoefer, G.A.

    1980-01-01

    Zooplankton concentration and composition was related to hydrographic parameters in Onslow Bay, NC. During summer the hydrography of Onslow Bay is often characterized by the presence of nutrient-rich Gulf Stream waters. These originate from greater depths of the Gulf Stream, intrude at subsurface depths, frequently strand in the Bay and have high concentrations of particulate matter and chlorophyll a. Since such water masses can maintain their integrity for up to one month, temporal changes in phyto- and zooplankton communities may be followed. Researchers describe the concentration, composition and distribution of abundant zooplankton taxa from summer 1976. Zooplankton distribution was affected by hydrography as, for example, Oncaeidae and Corycaeidae were significantly more abundant in intrusions than in the upper mixed layer. Zooplankton biomass and composition indicate relatively high production of and low predation rates on zooplankton in intruded waters.

  15. Zooplankton distribution as related to summer hydrographic conditions in Onslow Bay, North Carolina

    SciTech Connect

    Paffenhoefer, G.A.

    1980-01-01

    Zooplankton concentration and composition were related to hydrographic parameters in Onslow Bay, NC. During summer the hydrography of Onslow Bay is often characterized by the presence of nutrient-rich Gulf Stream waters. These originate from greater depths of the Gulf Stream, intrude at subsurface depths, frequently strand in the Bay and have high concentrations of particulate matter and chlorophyll a. Since such water masses can maintain their integrity for up to one month, temporal changes in phyto- and zooplankton communities may be followed. Researchers describe the concentration, composition and distribution of abundant zooplankton taxa from summer 1976. Zooplankton distribution was affected by hydrography as, for example, Oncaeidae and Corycaeidae were significantly more abundant in intrusions than in the upper mixed layer. Zooplankton biomass and composition indicate relatively high production of and low predation rates on zooplankton in intruded waters.

  16. Chemical Response of the Toxic Dinoflagellate Karenia mikimotoi Against Grazing by Three Species of Zooplankton.

    PubMed

    Dang, Lin-Xi; Li, Yue; Liu, Fei; Zhang, Yong; Yang, Wei-Dong; Li, Hong-Ye; Liu, Jie-Sheng

    2015-01-01

    We investigated the toxicity of Karenia mikimotoi toward three model grazers, the cladoceran Moina mongolica, the copepod Pseudodiaptomus annandalei, and the crustacean Artemia salina, and explored its chemical response upon zooplankton grazing. An induction experiment, where K. mikimotoi was exposed to grazers or waterborne cues from the mixed cultures revealed that K. mikimotoi might be toxic or nutritionally inadequate toward the three grazers. In general, direct exposure to the three grazers induced the production of hemolytic toxins and the synthesis of eicosapentaenoic acid (EPA). Both EPA and the hemolytic toxins from K. mikimotoi decreased the survival rate of the three grazers. In addition, the survival rates of M. mongolica, P. annandalei, and A. salina in the presence of induced K. mikimotoi that had previously been exposed to a certain grazer were lower than their counterparts caused by fresh K. mikimotoi, suggesting that exposure to some grazers might increase the toxicity of K. mikimotoi. The chemical response and associated increased resistance to further grazing suggested that K. mikimotoi could produce deterrents to protect against grazing by zooplankton and that the substances responsible might be hemolytic toxins and EPA. PMID:25523905

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

    SciTech Connect

    Holliday, D.V.

    1996-11-22

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

  18. A MULTI-PATCH MALARIA MODEL WITH LOGISTIC GROWTH POPULATIONS.

    PubMed

    Gao, Daozhou; Ruan, Shigui

    2012-01-01

    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

  19. Interactive effects of temperature, ultraviolet radiation and food quality on zooplankton alkaline phosphatase activity.

    PubMed

    Wolinski, Laura; Modenutti, Beatriz; Souza, Maria Sol; Balseiro, Esteban

    2016-06-01

    Ultraviolet Radiation (UVR) is a stressor for aquatic organisms affecting enzyme activities in planktonic populations because of the increase in reactive oxygen species. In addition, UVR exposure combined with other environmental factors (i.e. temperature and food quality) could have even higher detrimental effects. In this work, we aimed to determine the effect of UVR on somatic Alkaline Phosphatase Activity (APA) and Glutathione S-Transferase (GST) activity on the cladoceran Daphnia commutata under two different temperatures (10 °C and 20 °C) and under three food qualities (carbon:phosphorus ratios: 1150, 850 and 550). APA is a biomarker that is considered as a P deficiency indicator in zooplankton. Since recovery from UVR damage under dark conditions is an ATP depending reaction we also measured APA during recovery phases. We carried out a laboratory experiment combining different temperatures and food qualities with exposition to UVR followed by luminic and dark phases for recovery. In addition, we exposed organisms to H2O2, to establish if the response on APA to UVR was a consequence of the reactive oxygen species produced these short wavelengths. Our results showed that somatic APA was negatively affected by UVR exposure and this effect was enhanced under high temperature and low food quality. Consistently, GST activity was higher when exposed to UVR under both temperatures. The H2O2 experiments showed the same trend as UVR exposure, indicating that APA is affected mainly by oxidative stress than by direct effect of UVR on the enzyme. Finally, APA was affected in the dark phase of recovery confirming the P demands. These results enlighten the importance of food quality in the interacting effect of UVR and temperature, showing that C:P food ratio could determine the success or failure of zooplanktonic populations in a context of global change. PMID:26895537

  20. Modelling the evolution of the space debris population

    NASA Astrophysics Data System (ADS)

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

    1998-12-01

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

  1. A Simple Model of Optimal Population Coding for Sensory Systems

    PubMed Central

    Doi, Eizaburo; Lewicki, Michael S.

    2014-01-01

    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

  2. MULTISCALE MODELS OF TAXIS-DRIVEN PATTERNING IN BACTERIAL POPULATIONS.

    PubMed

    Xue, Chuan; Othmer, Hans G

    2009-01-01

    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 10(12) - 10(14) 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

  3. Lessons learned from multifrequency acoustic studies of zooplankton and micronekton in the western Antarctic Peninsula and the Gulf of Maine

    NASA Astrophysics Data System (ADS)

    Lavery, Andone C.; Lawson, Gareth L.; Wiebe, Peter H.

    2005-09-01

    A series of acoustic surveys of zooplankton and micronekton have been performed in the Gulf of Maine (GOM), off the northeast United States, and along the western Antarctic Peninsula (WAP). Similar techniques were used to survey these regions, including multifrequency acoustic backscatter (43, 120, 200, 420, 1000 kHz), MOCNESS, CTD, VPR, and in some instances physical microstructure measurements. The GOM is characterized by heterogeneous zooplankton communities in which biomass is dominated by abundant millimeter sized copepods, but the scattering is frequently dominated by a smaller number of strong scatterers, such as shelled pteropods and gas-bearing siphonophores. Heterogeneous zooplankton communities are also observed in the WAP, but patches of comparatively large (40 mm) Antarctic krill are present and often dominate the scattering. In both regions, striking patterns are evident in the backscatter that can be related to the biological community structure and physical processes. Differences in community structure, however, strongly affect the quantitative inferences that can be made based on the acoustic data. Combining direct biological and environmental information with recently developed scattering models has allowed dominant scatterers to be identified and inferences to be made regarding the physical factors influencing backscatter variability, though only under limited conditions. Highlights from these studies and lessons learned regarding our ability to interpret multifrequency acoustics are presented.

  4. Effects of stochastic population fluctuations in two models of biological macroevolution

    NASA Astrophysics Data System (ADS)

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

    Two mathematical models of macroevolution are studied. These models have population dynamics at the species level, and mutations and extinction of species are also included. The population dynamics are updated by difference equations with stochastic noise terms that characterize population fluctuations. The effects of the stochastic population fluctuations on diversity and total population sizes on evolutionary time scales are studied. In one model, species can make either predator-prey, mutualistic, or competitive interactions, while the other model allows only predator-prey interactions. When the noise in the population dynamics is strong enough, both models show intermittent behavior and their power spectral densities show approximate 1/f fluctuations. In the noiseless limit, the two models have different power spectral densities. For the predator-prey model, 1/f2 fluctuations appears, indicating random-walk like behavior, while the other model still shows 1/f noise. These results indicate that stochastic population fluctuations may significantly affect long-time evolutionary dynamics.

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

    PubMed Central

    Mould, D R; Upton, R N

    2012-01-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

    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.

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

    EPA Science Inventory

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

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

    USGS Publications Warehouse

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

    2003-01-01

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

  9. Interacting trophic forcing and the population dynamics of herring.

    PubMed

    Lindegren, Martin; Ostman, Orjan; Gårdmark, Anna

    2011-07-01

    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

  10. A Population Genetics Model of Marker-Assisted Selection

    PubMed Central

    Luo, Z. W.; Thompson, R.; Woolliams, J. A.

    1997-01-01

    A deterministic two-loci model was developed to predict genetic response to marker-assisted selection (MAS) in one generation and in multiple generations. Formulas were derived to relate linkage disequilibrium in a population to the proportion of additive genetic variance used by MAS, and in turn to an extra improvement in genetic response over phenotypic selection. Predictions of the response were compared to those predicted by using an infinite-loci model and the factors affecting efficiency of MAS were examined. Theoretical analyses of the present study revealed the nonlinearity between the selection intensity and genetic response in MAS. In addition to the heritability of the trait and the proportion of the marker-associated genetic variance, the frequencies of the selectively favorable alleles at the two loci, one marker and one quantitative trait locus, were found to play an important role in determining both the short- and long-term efficiencies of MAS. The evolution of linkage disequilibrium and thus the genetic response over several generations were predicted theoretically and examined by simulation. MAS dissipated the disequilibrium more quickly than drift alone. In some cases studied, the rate of dissipation was as large as that to be expected in the circumstance where the true recombination fraction was increased by three times and selection was absent. PMID:9215918

  11. 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)

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

    2009-12-01

    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.

  12. Networks and Models with Heterogeneous Population Structure in Epidemiology

    NASA Astrophysics Data System (ADS)

    Kao, R. R.

    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).

  13. Biomass of zooplankton in the eastern Arctic Ocean - A base line study

    NASA Astrophysics Data System (ADS)

    Kosobokova, Ksenia; Hirche, Hans-Jürgen

    2009-09-01

    Only a few historical assessments of the zooplankton biomass in the Arctic Ocean exist are difficult to compare due to methodological differences including incomplete sampling of the water column. We present assessments of the zooplankton biomass for 66 locations scattered over the Eurasian and Makarov Basins of the Arctic Ocean and analyze regional variability and factors affecting the biomass distribution. The study is based on material from several summer expeditions of RV Polarstern (1993-1998) that was collected and processed using consistent methods, i.e. stratified sampling of the entire water column from the bottom to the surface with very similar gear and standardized calculation of biomass. Total zooplankton biomass varied strongly from 1.9 to 23.9 g DW m -2 dry mass. Regional variability was mainly related to the circulation pattern, but local food availability was also important. A belt of elevated biomass along the Eurasian continental margin was associated with the advection of Atlantic pelagic populations within the Arctic Ocean Boundary Current along the Siberian shelves and returning branches along mid-ocean ridges. Biomass was highest in the core of the Atlantic inflow and remained rather stable along the continental margins, but species composition changed, pointing to different adaptation levels to local conditions by advected species. Biomass gradually decreased towards the shelves and basins and was lowest in the centers of the basins north of 85°N. In the slope region, three Calanus species ( C. hyperboreus, C. glacialis, C. finmarchicus) and Metridia longa contributed most to the biomass, chaetognaths ( Eukrohnia hamata) were also important. In the basins, C. hyperboreus was dominant, copepods made up to 97% of total biomass. Vertical distribution was similar at all stations with biomass maxima in the upper 50 m layer except for stations near Fram Strait and northern Kara Sea, the gateways of Atlantic water to the Arctic Ocean, where maxima where between 25 and 100 m. As there was only very little interannual variability of temperature and current velocity in the regions of the Atlantic inflow we suggest that the majority of our samples, collected in 1993 and 1995, represents the phase of the 1990s warm event in the Nordic Seas.

  14. Demographic population model for American shad: will access to additional habitat upstream of dams increase population sizes?

    USGS Publications Warehouse

    Harris, Julianne E.; Hightower, Joseph E.

    2012-01-01

    American shad Alosa sapidissima are in decline in their native range, and modeling possible management scenarios could help guide their restoration. We developed a density-dependent, deterministic, stage-based matrix model to predict the population-level results of transporting American shad to suitable spawning habitat upstream of dams on the Roanoke River, North Carolina and Virginia. We used data on sonic-tagged adult American shad and oxytetracycline-marked American shad fry both above and below dams on the Roanoke River with information from other systems to estimate a starting population size and vital rates. We modeled the adult female population over 30 years under plausible scenarios of adult transport, effective fecundity (egg production), and survival of adults (i.e., to return to spawn the next year) and juveniles (from spawned egg to age 1). We also evaluated the potential effects of increased survival for adults and juveniles. The adult female population size in the Roanoke River was estimated to be 5,224. With no transport, the model predicted a slow population increase over the next 30 years. Predicted population increases were highest when survival was improved during the first year of life. Transport was predicted to benefit the population only if high rates of effective fecundity and juvenile survival could be achieved. Currently, transported adults and young are less likely to successfully out-migrate than individuals below the dams, and the estimated adult population size is much smaller than either of two assumed values of carrying capacity for the lower river; therefore, transport is not predicted to help restore the stock under present conditions. Research on survival rates, density-dependent processes, and the impacts of structures to increase out-migration success would improve evaluation of the potential benefits of access to additional spawning habitat for American shad.

  15. An isotopic (Δ14C, δ13C, and δ15N) investigation of particulate organic matter and zooplankton biomass in Lake Superior and across a size-gradient of aquatic systems

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    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 (Δ14C) and stable isotope (δ13C, δ15N) 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 Δ14C 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.

  16. Within and Among Population Item Fit with the Simple Logistic Model.

    ERIC Educational Resources Information Center

    Andrich, David; Kline, Paul

    1981-01-01

    The Rasch simple logistic model is used to examine the relative item parameter values of a personality inventory with respect to populations cross-classified by sex and country. While items conform to the model within each of the populations, half the items show significant discrepancies among the populations. (Author/RL)

  17. Population synthesis modelling of luminous infrared galaxies at intermediate redshift

    NASA Astrophysics Data System (ADS)

    Giovannoli, E.; Buat, V.; Noll, S.; Burgarella, D.; Magnelli, B.

    2011-01-01

    Context. Luminous InfraRed Galaxies (LIRGs) are particularly important for studying the build-up of the stellar mass from z = 1 to z = 0, and for determining physical properties of these objects at redshift 0.7. LIRGs are now identified as playing a major role in galaxy evolution from z = 1 to 0. The global star formation rate (SFR) at z ~ 0.7 is mainly produced by LIRGs. Aims: We perform a multiwavelength study of an LIRGs sample in the Extended Chandra Deep Field South at z = 0.7, selected at 24 μm by MIPS onboard Spitzer Space Telescope and detected in 17 filters. Data go from the near-ultraviolet to the mid-infrared. This multiwavelength dataset allows us to place strong constraints on the spectral energy distributions (SEDs) of galaxies, and thus to efficiently derive physical parameters such as the SFR, the total infrared luminosity, attenuation parameters, and star formation history. We distinguish a subsample of galaxies detected at 70 μm, which we compare to the rest of the sample to investigate the relative importance of this wavelength in determining of the physical parameters. An important part of this work is elaboration of a mock catalogue that allows us to have a reliability criterion for the derived parameters. Methods: We studied LIRGs by means of the SED-fitting code CIGALE. At first, this code creates synthetic spectra from the Maraston stellar population models. The stellar population spectra are attenuated by using a synthetic Calzetti-based attenuation law before adding the dust emission as given by the infrared SED library. The originality of CIGALE is that it allows us to perform consistent fits of the dust-affected ultaviolet-to-infrared wavelength range. This technique appears to be a very powerful tool in the case where we can have access to a dataset that is well-sampled over a wide range of wavelengths. Results: We are able to derive a star formation history and to estimate the fraction of infrared luminosity reprocessed by an active galactic nucleus. We study the dust temperatures of our galaxies detected at 70 μm and find them colder than predicted by models. We also study the relation between the SFR and the stellar mass and do not find a tight correlation between either of them, but instead a flat distribution and a large scatter, which is interpreted in terms of variations in star formation history.

  18. Population differentiation in Daphnia alters community assembly in experimental ponds.

    PubMed

    Pantel, Jelena H; Leibold, Mathew A; Juenger, Thomas E

    2011-03-01

    Most studies of community assembly ignore how genetic differentiation within species affects their colonization and extinction. However, genetic differentiation in ecologically relevant traits may be substantial enough to alter the colonization and extinction processes that drive community assembly. We measured significant molecular genetic and quantitative trait differentiation among three Daphnia pulex × pulicaria populations in southwestern Michigan ponds and investigated whether this differentiation could alter the assembly of pond zooplankton communities in experimental mesocosms. In this study, we monitored the invasion success of different D. pulex × pulicaria populations after their introduction into an established zooplankton community. We also monitored the invasion success of a diverse array of zooplankton species into different D. pulex × pulicaria populations. Zooplankton community composition depended on the D. pulex × pulicaria source population. Daphnia pulex × pulicaria from one population failed to invade zooplankton communities, while those from other populations successfully invaded similar communities. If population differentiation in other species plays a role in community assembly similar to that demonstrated in our study, assembly may be more sensitive to evolutionary processes than has been previously generally considered. PMID:21460540

  19. POPULATION-BASED EXPOSURE MODELING FOR AIR POLLUTANTS AT EPA'S NATIONAL EXPOSURE RESEARCH LABORATORY

    EPA Science Inventory

    The US EPA's National Exposure Research Laboratory (NERL) has been developing, applying, and evaluating population-based exposure models to improve our understanding of the variability in personal exposure to air pollutants. Estimates of population variability are needed for E...

  20. Simulation model of Cryptomonas ovata population dynamics in southern Kootenay Lake, British Columbia

    USGS Publications Warehouse

    Cloern, James E.

    1978-01-01

    The model simulates well the timing and magnitude of all observed population changes and, more importantly, it gives insight into the important mechanisms which regulate population density of C. ovata in this natural system.

  1. Simple graph models of information spread in finite populations

    PubMed Central

    Voorhees, Burton; Ryder, Bergerud

    2015-01-01

    We consider several classes of simple graphs as potential models for information diffusion in a structured population. These include biases cycles, dual circular flows, partial bipartite graphs and what we call ‘single-link’ graphs. In addition to fixation probabilities, we study structure parameters for these graphs, including eigenvalues of the Laplacian, conductances, communicability and expected hitting times. In several cases, values of these parameters are related, most strongly so for partial bipartite graphs. A measure of directional bias in cycles and circular flows arises from the non-zero eigenvalues of the antisymmetric part of the Laplacian and another measure is found for cycles as the value of the transition probability for which hitting times going in either direction of the cycle are equal. A generalization of circular flow graphs is used to illustrate the possibility of tuning edge weights to match pre-specified values for graph parameters; in particular, we show that generalizations of circular flows can be tuned to have fixation probabilities equal to the Moran probability for a complete graph by tuning vertex temperature profiles. Finally, single-link graphs are introduced as an example of a graph involving a bottleneck in the connection between two components and these are compared to the partial bipartite graphs. PMID:26064661

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

    PubMed Central

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

    1997-01-01

    The detrimental effects of elevated intensities of mid-UV radiation (UVB), a result of stratospheric ozone depletion during the austral spring, on the primary producers of the Antarctic marine ecosystem have been well documented. Here we report that natural populations of Antarctic zooplankton also sustain significant DNA damage [measured as cyclobutane pyrimidine dimers (CPDs)] during periods of increased UVB flux. This is the first direct evidence that increased solar UVB may result in damage to marine organisms other than primary producers in Antarctica. The extent of DNA damage in pelagic icefish eggs correlated with daily incident UVB irradiance, reflecting the difference between acquisition and repair of CPDs. Patterns of DNA damage in fish larvae did not correlate with daily UVB flux, possibly due to different depth distributions and/or different capacities for DNA repair. Clearance of CPDs by Antarctic fish and krill was mediated primarily by the photoenzymatic repair system. Although repair rates were large for all species evaluated, they were apparently inadequate to prevent the transient accumulation of substantial CPD burdens. The capacity for DNA repair in Antarctic organisms was highest in those species whose early life history stages occupy the water column during periods of ozone depletion (austral spring) and lowest in fish species whose eggs and larvae are abundant during winter. Although the potential reduction in fitness of Antarctic zooplankton resulting from DNA damage is unknown, we suggest that increased solar UV may reduce recruitment and adversely affect trophic transfer of productivity by affecting heterotrophic species as well as primary producers. PMID:9037040

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

    SciTech Connect

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

    1997-02-18

    The detrimental effects of elevated intensities of mid-UV radiation (UVB), a result of stratospheric ozone depletion during the austral spring, on the primary producers of the Antarctic marine ecosystem have been well documented. Here we report that natural populations of Antarctic zooplankton also sustain significant DNA damage [measured as cyclobutane pyrimidine dimers (CPDs)] during periods of increased UVB flux. This is the first direct evidence that increased solar UVB may result in damage to marine organisms other than primary producers in Antarctica. The extent of DNA damage in pelagic icefish eggs correlated with daily incident UVB irradiance, reflecting the difference between acquisition and repair of CPDs. Patterns of DNA damage in fish larvae did not correlated with daily UVB flux, possibly due to different depth distributions and/or different capacities for DNA repair. Clearance of CPDs by Antarctic fish and krill was mediated primarily by the photoenzymatic repair system. Although repair rates were large for all species evaluated, they were apparently inadequate to prevent the transient accumulation of substantial CPD burdens. The capacity for DNA repair in Antarctic organisms was highest in those species whose early life history stages occupy the water column during periods of ozone depletion (austral spring) and lowest in fish species whose eggs and larvae are abundant during winter. Although the potential reduction in fitness of Antarctic zooplankton resulting from DNA damage is unknown, we suggest that increased solar UV may reduce recruitment and adversely affect trophic transfer of productivity by affecting heterotrophic species as well as primary producers. 54 refs., 4 figs., 2 tabs.

  4. Statistical Mechanics of Population --- The Lattice Lotka-Volterra Model ---

    NASA Astrophysics Data System (ADS)

    Matsuda, H.; Ogita, N.; Sasaki, A.; Sato, K.

    1992-12-01

    To derive the consequence of heritable traits of individual organisms upon the feature of their populations, the lattice Lotka-Volterra model is studied which is defined as a Markov process of the state of the lattice space. A lattice site is either vacant or occupied by an individual of a certain type or species. Transition rates of the process are given in terms of parameters representing the traits of an individual such as intrinsic birth and death and migration rate of each type. Density is a variable defined as a probability that a site is occupied by a certain type. Under a given state of a site the conditional probability of its nearest neighbor site being occupied by a certain type is termed environs density of the site. Mutual exclusion of individuals is already taken into account by the basic assumption of the lattice model. Other interaction between individuals can be taken into account by assuming that the actual birth and death and migration rates are dependent on the environs densities. Extending the notion of ordinary Malthusian parameters, we define Malthusians as dynamical variables specifying the time development of the densities. Conditions for the positive stationary densities and for the evolutional stability (ES) against the invasion of mutant types is given in terms of Malthusians. Using the pair approximation (PA), a simplest decoupling approximation to take account of spatial correlation, we obtain analytical results for stationary densities, and critical parameters for ES in the case of two types. Assuming that the death rate is dependent on the environs density, we derive conditions for the evolution of altruism. Comparing with computer simulation, we discuss the validity of PA and its improvement.

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

    USGS Publications Warehouse

    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

    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.

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

    PubMed

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

    2013-10-01

    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. PMID:23565966

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

    PubMed

    Medici, Emília Patrícia; Desbiez, Arnaud Leonard Jean

    2012-12-01

    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

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

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    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.

  9. A stochastic population model to evaluate Moapa dace (Moapa coriacea) population growth under alternative management scenarios

    USGS Publications Warehouse

    Perry, Russell W.; Jones, Edward; Scoppettone, G. Gary

    2015-01-01

    Increasing or decreasing the total carrying capacity of all stream segments resulted in changes in equilibrium population size that were directly proportional to the change in capacity. However, changes in carrying capacity to some stream segments but not others could result in disproportionate changes in equilibrium population sizes by altering density-dependent movement and survival in the stream network. These simulations show how our IBM can provide a useful management tool for understanding the effect of restoration actions or reintroductions on carrying capacity, and, in turn, how these changes affect Moapa dace abundance. Such tools are critical for devising management strategies to achieve recovery goals.

  10. An agent-based computational model for tuberculosis spreading on age-structured populations

    NASA Astrophysics Data System (ADS)

    Graciani Rodrigues, C. C.; Espíndola, Aquino L.; Penna, T. J. P.

    2015-06-01

    In this work we present an agent-based computational model to study the spreading of the tuberculosis (TB) disease on age-structured populations. The model proposed is a merge of two previous models: an agent-based computational model for the spreading of tuberculosis and a bit-string model for biological aging. The combination of TB with the population aging, reproduces the coexistence of health states, as seen in real populations. In addition, the universal exponential behavior of mortalities curves is still preserved. Finally, the population distribution as function of age shows the prevalence of TB mostly in elders, for high efficacy treatments.

  11. Lipids of gelatinous Antarctic zooplankton: Cnidaria and Ctenophora.

    PubMed

    Nelson, M M; Phleger, C F; Mooney, B D; Nichols, P D

    2000-05-01

    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 low in all zooplankton (0.1-5 mg g wet mass) and included primarily polar lipids (59-96% of total lipid). Triacylglycerols were 0-26% of total lipids, and wax esters were 0-11% in all species. Cholesterol was the major sterol in all Cnidaria (50-63% of total sterols) whereas in most ctenophores it was lower at 26-45%. These cholesterol levels are consistent with a combined carnivorous and phytoplanktivorous diet in the ctenophores, with the carnivorous diet more dominant in the Cnidaria. Other sterols included primarily trans-dehydrocholesterol, desmosterol, 24-methylcholest-5,22E-dien-3beta-ol, 24-nordehydrocholesterol, and 24-methylenecholesterol. Total stanols were 0-6% in all zooplankton. Eicosapentaenoic acid and docosahexaenoic acid were the major polyunsaturated fatty acids (PUFA) in all samples (7-25% of total fatty acids) except for A. wyvillei in which docosapentaenoic acid was 10% of total fatty acids. The PUFA 18:5n-3 was not detected in 1997 samples, but constituted 0.2-0.8% in most 1998 samples. Monounsaturated fatty acids included primarily 18:1n-9c, 16:1n-7c, and 18:1n-7c. The principal saturated fatty acids in all samples were 16:0, 18:0, and 14:0. These data are the first for many of these zooplankton species and the first sterol data for most species. The use of the signature lipid approach has enabled examination of aspects of trophodynamics not obtainable by conventional techniques. PMID:10907790

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

    EPA Science Inventory

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

  13. 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...

  14. Distribution of zooplankton biomass and potential metabolic activities across the northern Benguela upwelling system

    NASA Astrophysics Data System (ADS)

    Fernández-Urruzola, I.; Osma, N.; Packard, T. T.; Gómez, M.; Postel, L.

    2014-11-01

    The distribution of zooplankton biomass and potential metabolic rates, in terms of electron transport system (ETS) and glutamate dehydrogenase (GDH), were analyzed along a cross-shelf transect in waters off Namibia. The highly variable dynamics of upwelling filaments promoted short-term fluctuations in the zooplankton biomass and metabolism. Maximum values were characteristically found over the shelf-break, where zooplankton biomass as dry mass (DM) reached peaks of 64.5 mg m- 3 within the upper 200 m in late August. Two weeks later, the zooplankton-DM decreased by more than a third (19 mg DM m- 3). Zooplankton potential respiration and NH4+ excretion averaged 234 μmol O2 m- 3 d- 1 and 169 μmol NH4+ m- 3 d- 1 in the Namibian shelf, respectively. High protein-specific ETS activities even in the low-chlorophyll waters outside the filament suggested a shift into greater omnivory seaward. In this light, zooplankton elemental and isotopic compositions were used to investigate the pelagic food web interactions. They evidenced spatial changes in the carbon resource for zooplankton as well as changes in the form of nitrogen that fueled the biological production in aging advected waters. Overall, both aspects of zooplankton metabolism impacted the primary productivity at a level less than 10% under all the different oceanographic conditions.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  16. 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...

  17. Assessment of Zooplankton Size Fractionation for Monitoring Fry and Fingerling Culture Ponds

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Methodology was formulated for use in the rapid assessment of zooplankton in channel catfish ponds. Understanding zooplankton prey size is useful for effective pond management. Size fractionation using differential sieve sizes was an effective means of separating size classes in live material, whe...

  18. Cladoceran zooplankton abundance under clear and snow-covered ice

    USGS Publications Warehouse

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

    2003-01-01

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

  19. Viability of marine phytoplankton in zooplankton fecal pellets

    NASA Astrophysics Data System (ADS)

    Fowler, S. W.; Fisher, N. S.

    1983-09-01

    Zooplankton fecal pellets collected from sediment traps or freshly excreted by euphausiids grazing in situ at natural phytoplankton levels in the pelagic Mediterranean were incubated under laboratory conditions and always contained viable