Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Wild rodents and insectivores as carriers of pathogenic Leptospira and Toxoplasma gondii in The Netherlands
    Krijger, Inge M. ; Ahmed, Ahmed A.A. ; Goris, Maria G.A. ; Cornelissen, Jan B.W.J. ; Groot Koerkamp, Peter W.G. ; Meerburg, Bastiaan G. - \ 2020
    Veterinary Medicine and Science (2020). - ISSN 2053-1095 - 8 p.
    leptospirosis - mice - pathogen–host relationship - rats - reservoir - zoonoses

    Small mammals such as rodents can to carry zoonotic pathogens. Currently, there is impaired knowledge on zoonotic pathogens in rodents and insectivores in the Netherlands. This limits opportunities for preventive measures and complicates risk-assessments for zoonotic transmission to humans. Leptospira spp. and Toxoplasma gondii are present on a list of prioritized emerging pathogens in the Netherlands and were therefore the focus of this study. Both pathogens have the ability to survive under moist environmental conditions. In total, a group of 379 small mammals (rodents & insectivores) were tested on pathogenic Leptospira spp., and 312 on T. gondii. Rodents and insectivores were trapped at various sites, but mostly on pig and dairy farms throughout the country. Over five percent of the animals (5.3%, n = 379) tested positive for Leptospira DNA, and five of the animals (1.6%, n = 312) tested were positive for T. gondii DNA. The animals positive for T.gondii were all brown rats and the ones for Leptospira spp. were various species. Our results show that insectivores and rodents might be used as an indicator for the environmental contamination and/or the contamination in wildlife for Leptospira spp.

    Intercomparison of global river discharge simulations focusing on dam operation - Multiple models analysis in two case-study river basins, Missouri-Mississippi and Green-Colorado
    Masaki, Yoshimitsu ; Hanasaki, Naota ; Biemans, Hester ; Müller Schmied, Hannes ; Tang, Qiuhong ; Wada, Yoshihide ; Gosling, Simon N. ; Takahashi, Kiyoshi ; Hijioka, Yasuaki - \ 2017
    Environmental Research Letters 12 (2017)5. - ISSN 1748-9318
    flood control - flow regimes - reservoir - river discharge

    We performed an intercomparison of river discharge regulated by dams under four meteorological forcings among five global hydrological models for a historical period by simulation. This is the first global multimodel intercomparison study on dam-regulated river flow. Although the simulations were conducted globally, the Missouri-Mississippi and Green-Colorado Rivers were chosen as case-study sites in this study. The hydrological models incorporate generic schemes of dam operation, not specific to a certain dam. We examined river discharge on a longitudinal section of river channels to investigate the effects of dams on simulated discharge, especially at the seasonal time scale. We found that the magnitude of dam regulation differed considerably among the hydrological models. The difference was attributable not only to dam operation schemes but also to the magnitude of simulated river discharge flowing into dams. That is, although a similar algorithm of dam operation schemes was incorporated in different hydrological models, the magnitude of dam regulation substantially differed among the models. Intermodel discrepancies tended to decrease toward the lower reaches of these river basins, which means model dependence is less significant toward lower reaches. These case-study results imply that, intermodel comparisons of river discharge should be made at different locations along the river's course to critically examine the performance of hydrological models because the performance can vary with the locations.

    What drives the distribution of the bloom-forming cyanobacteria Planktothrix agardhii and Cylindrospermopsis raciborskii?
    Bonilla, S. ; Aubriot, L. ; Soares, M.C.S. ; Gonzalez-Piana, M. ; Fabre, A. ; Huszar, V.L.M. ; Lurling, M. ; Antoniades, D. ; Padisak, J. ; Kruk, C. - \ 2012
    FEMS microbiology ecology 79 (2012)3. - ISSN 0168-6496 - p. 594 - 607.
    oscillatoria-agardhii - phytoplankton communities - invasive cyanobacterium - northeast brazil - eutrophic lakes - shallow - light - temperature - reservoir - growth
    The cyanobacteria Planktothrix agardhii and Cylindrospermopsis raciborskii are bloom-forming species common in eutrophic freshwaters. These filamentous species share certain physiological traits which imply that they might flourish under similar environmental conditions. We compared the distribution of the two species in a large database (940 samples) covering different climatic regions and the Northern and Southern hemispheres, and carried out laboratory experiments to compare their morphological and physiological responses. The environmental ranges of the two species overlapped with respect to temperature, light and total phosphorus (TP); however, they responded differently to environmental gradients; C. raciborskii biovolume changed gradually while P. agardhii shifted sharply from being highly dominated to a rare component of the phytoplankton. As expected, P. agardhii dominates the phytoplankton with high TP and low light availability conditions. Contrary to predictions, C. raciborskii succeeded in all climates and at temperatures as low as 11 degrees C. Cylindrospermopsis raciborskii had higher phenotypic plasticity than P. agardhii in terms of pigments, individual size and growth rates. We conclude that the phenotypic plasticity of C. raciborskii could explain its ongoing expansion to temperate latitudes and suggest its future predominance under predicted climate-change scenarios.
    The role of wild rodents in spread and transmission of Coxiella burnetii needs further elucidation
    Meerburg, B.G. ; Reusken, C.B.E.M. - \ 2011
    Wildlife Research 38 (2011)7. - ISSN 1035-3712 - p. 617 - 625.
    serological cross-reactions - q-fever infection - home-range size - hantavirus infection - rattus-norvegicus - phase-i - uttar-pradesh - risk-factors - epidemiology - reservoir
    Rodents are known to cause massive food losses, but are also implicated as reservoirs for a wide variety of zoonotic pathogens. This review discusses the contribution of rodents in the spread and transmission of Coxiella burnetii, the causative agent of Q-fever. We found that rodents have been implicated as reservoirs for Q-fever, but their role in pathogen maintenance, geographic spread and transmission still remains to be clarified. As there are indications for a role of rodents in Q-fever epidemiology, including during the 2007–10 outbreak in the Netherlands, the overall lack of knowledge on the role of rodents warrants studies into their contribution in transmission of C. burnetii from the sylvatic cycle to the domestic cycle, in within-herd transmission, in transmission to surrounding farms and in direct transmission to humans. Although the basic sylvatic and domestic cycles of C. burnetii infection can operate independently, they will overlap in many instances as many areas in the world are occupied by both domestic and wild animals. This area of Q-fever ecology is of interest and research should focus on this aspect of Q-fever epidemiology and, in particular, on the role of rodents therein. More studies are needed that elicit the exact role of rodents in epidemiology of C. burnetii to further optimise disease control.
    Millennium Ecosystem Assessment Scenario drivers (1970-2050): Climate and hydrological alterations
    Fekete, B.M. ; Wisser, D. ; Kroeze, C. ; Mayorga, E. ; Bouwman, A.F. ; Wollheim, W.M. ; Vörösmarty, C.J. - \ 2010
    Global Biogeochemical Cycles 24 (2010)GB0A12. - ISSN 0886-6236 - p. 1 - 12.
    water-balance - global-scale - evaporation - reservoir - models - irrigation - runoff - sea
    This study was carried out to support and enhance a series of global studies assessing contemporary and future changes in nutrient export from watersheds (Global Nutrient Export from Watersheds (NEWS)). Because hydrography is one of the most important drivers in nutrient transport, it was essential to establish how climatic changes and direct human activities (primarily irrigation and reservoir operations) affect the hydrological cycle. Contemporary and future hydrography was established by applying a modified version of a global water balance and transport model (WBMplus) driven by present and future climate forcing, as described in the Millennium Ecosystem Assessment scenarios (1970-2050). WBMplus represents a major upgrade to previous WBM implementations by incorporating irrigational water uptake and reservoir operations in a single modeling framework. Contemporary simulations were carried out by using both observed climate forcings from the Climate Research Unit of East Anglia (CRU) data sets and from Global Circulation Model (GCM) simulations that are comparable to the future simulations from the same GCM forcings. Future trends in three key human activities (land use, irrigation, and reservoirs operation for hydropower) were taken from the Integrated Model to Assess the Global Environment (IMAGE). The reservoir operation required establishing a realistic distribution of future reservoirs since the IMAGE model provided only the hydropower potentials for the different future scenarios.
    Effects of the cyanobacterium Cylindrospermopsis raciborskii on feeding and life-history characteristics of the grazer Daphnia magna
    Soares, M.C.S. ; Lürling, M.F.L.L.W. ; Panosso, R. ; Huszar, V.M. - \ 2009
    Ecotoxicology and Environmental Safety 72 (2009)4. - ISSN 0147-6513 - p. 1183 - 1189.
    paralytic shellfish toxins - aphanizomenon-flos-aquae - 2 german lakes - north-queensland - microcystis-aeruginosa - carbon transfer - subba raju - 1st report - reservoir - zooplankton
    Laboratory experiments were used to test the hypothesis that feeding and growth of the zooplankton grazer Daphnia magna will decrease with increasing proportions of the cyanobacterium Cylindrospermopsis raciborskii in the diet (mixed feeds with the green alga Scenedesmus obliquus). A strain of C. raciborskii, which does not produce cylindrospermopsin but contains saxitoxins and gonyautoxins, was not acutely toxic to Daphnia, as the daphnids survived slightly longer in suspensions with the cyanobacterium as the sole feed than in medium without food. Daphnia growth rates were only depressed at feeds comprised of 75% C. raciborskii or more. Daphnids were larger with increased proportions of Scenedesmus in the food, but there was no difference between animals reared on mixed feeds and those grown on different proportions of a pure diet of Scenedesmus. Daphnia clearance rates on feeds with a high share of C. raciborskii were significantly lower than on mixtures with a low share of C. raciborskii. Consequently, in cylindrospermopsin-free strains, chemotypes that have been observed so far in Europe and Brazil, feeding inhibition and the resulting energy limitation might be the dominant factor affecting growth of large-bodied cladocerans
    Observations and model estimates of diurnal water temperature dynamics in mosquito breeding sites in western Kenya
    Paaijmans, K.P. ; Jacobs, A.F.G. ; Takken, W. ; Heusinkveld, B.G. ; Githeko, A.K. ; Dicke, M. ; Holtslag, A.A.M. - \ 2008
    Hydrological Processes 22 (2008)24. - ISSN 0885-6087 - p. 4789 - 4801.
    anopheles-gambiae diptera - aquatic stages - malaria transmission - culicidae larvae - land-cover - habitats - survival - highlands - reservoir - village
    Water temperature is an important determinant of the growth and development of malaria mosquito immatures. To gain a better understanding of the daily temperature dynamics of malaria mosquito breeding sites and of the relationships between meteorological variables and water temperature, three clear water pools (diameter × depth: 0·16 × 0·04, 0·32 × 0·16 and 0·96 × 0·32 m) were created in Kenya. Continuous water temperature measurements at various depths were combined with weather data collections from a meteorological station. The water pools were homothermic, but the top water layer differed by up to about 2 °C in temperature, depending on weather conditions. Although the daily mean temperature of all water pools was similar (27·4-28·1 °C), the average recorded difference between the daily minimum and maximum temperature was 14·4 °C in the smallest versus 7·1 °C in the largest water pool. Average water temperature corresponded well with various meteorological variables. The temperature of each water pool was continuously higher than the air temperature. A model was developed that predicts the diurnal water temperature dynamics accurately, based on the estimated energy budget components of these water pools. The air-water interface appeared the most important boundary for energy exchange processes and on average 82-89% of the total energy was gained and lost at this boundary. Besides energy loss to longwave radiation, loss due to evaporation was high; the average estimated daily evaporation ranged from 4·2 mm in the smallest to 3·7 mm in the largest water pool
    Exploration of relationships between phytoplankton biomass and related environmental variables using multivariate statistic analysis in a eutrophic shallow lake: A 5-year study
    Wang, X.L. ; Lu, Y.L. ; He, G.Z. ; Han, Jingyi ; Wang, T.Y. - \ 2007
    Journal of Environmental Sciences 19 (2007)8. - ISSN 1001-0742 - p. 920 - 927.
    chemical factors - chlorophyll - patterns - china - chemistry - reservoir - taihu
    Understanding the process of the changing phytoplankton patterns can be particularly useful in water quality improvement and management decisions. However, it is generally not easy to illustrate the interactions between phytoplankton biomass and related environmental variables given their high spatial and temporal heterogeneity. To elucidate relationships between them, in a eutrophic shallow lake, Taihu Lake, relative long-term data set of biotic and abiotic parameters of water quality in the lake were conducted using multivariate statistical analysis within seasonal periodicity. The results indicate that water temperature and total phosphorus (TP) played governing roles in phytoplankton dynamics in most seasons (i.e. temperature in winter, spring and summer; TP in spring, summer and autumn); COD (chemical oxygen demand) and BOD (biological oxygen demand) presented significant positive relationships with phytoplankton biomass in spring, summer and autumn. However, a complex interplay was found between phytoplankton biomass and nitrogen considering significant positive relationships occurring between them in spring and autumn, and conversely negative ones in summer. As the predatory factor, zooplankton presented significant grazing-pressure on phytoplankton biomass during summer in view of negative relationship between them in the season. Significant feedback effects of phytoplankton development were identified in summer and autumn in view that significant relationships were observed between phytoplankton biomass and pH, Trans (transparency of water) and DO. The results indicate that interactions between phytoplankton biomass and related environmental variables are highly sensitive to seasonal periodicity, which improves understanding of different roles of biotic and abiotic variables upon phytoplankton variability, and hence, advances management methods for eutrophic lakes.
    Seasonal variation in primary production of a large high altitude tropical lake (Lake Tana, Ethiopia): effects of nutritient availability and water transparency
    Wondie, A. ; Mengistu, S. ; Vijverberg, J. ; Dejen, E. - \ 2007
    Aquatic Ecology 41 (2007)2. - ISSN 1386-2588 - p. 195 - 207.
    barbs barbus - turbid waters - species flock - cyprinidae - reservoir
    Primary production rates, chlorophyll and phytoplankton biovolume were measured monthly from April 2003 to November 2004 in Lake Tana, a large tropical lake in the highlands of Ethiopia. The lake is characterised by low nutrient concentrations, and a low water transparency due to high silt load of the inflowing rivers during the rainy seasons (May¿November) and daily resuspension of sediments in the inshore zone. The mean chlorophyll-a concentrations varied seasonally and ranged from 2.6 mg m¿3 to 8.5 mg m¿3 (mean: 4.5 mg m¿3) in the offshore zone. Primary production was measured using the light¿dark bottles technique. We incubated only at three depths, i.e. 0.6, 1.2 and 1.8 m. Therefore, we may have missed a substantial part of the depth production profile and probably also frequently missed P max. Gross primary production in the openwater averaged 2.43 g O2 m¿2 d¿1 and ranged between 0.03 g O2 m¿2 d¿1 and 10.2 g O2 m¿2 d¿1; production was significantly higher in the inshore zone. The highest production rates were observed in the post-rainy season (Oct¿Nov), which coincided with a bloom of Microcystis and higher chlorophyll levels. This seasonal high production is probably caused by a relatively high nutrient availability in combination with favourable light conditions. The gross primary production rates of L. Tana are among the lowest compared with other tropical lakes. This will be partly the result of our underestimation of gross primary production by often missing P max. Another cause is the oligotrophic nature of the lake in combination with its relatively low water transparency. The gross primary production per unit chlorophyll in the openwater zone was in the same range as in 30 other tropical lakes and reservoirs. The higher primary production in the inshore zone is probably the result of the daily water column mixing (Z mix ¿ Z t) in this area, enhancing nutrient recycling. A large proportion of the annual primary production is realised in one of the four seasons only. This productive post-rainy season is relatively short (2 months) and therefore efficiency of transfer of matter between the first and second trophic level of the Lake ecosystem will be poor.
    Stochastic simulation of large grids using free and public domain software
    Bruin, S. de; Wit, A.J.W. de - \ 2005
    Computers and Geosciences 31 (2005)7. - ISSN 0098-3004 - p. 828 - 836.
    soil acidification - uncertainty - program - reservoir - entropy
    This paper proposes a tiled map procedure enabling sequential indicator simulation on grids consisting of several tens of millions of cells, without putting excessive memory requirements. Spatial continuity across map tiles is handled by conditioning adjacent tiles on their shared boundaries. Tiles across the area can be characterized by dissimilar models of spatial continuity (semi-variograms) thus relieving the requirement of a global stationarity decision. Additionally, the approach provides a simple mechanism for reseeding the pseudo random number generator. Implementation of the algorithm involved small modifications to a GSLIB program and Bash and awk scripting. The software was stable on several platforms, including 32-bit systems with a 4 Gb memory addressing limit. In an experiment we simulated 25 realizations of a 11,274×13,000 grid representing local uncertainty in the Dutch land cover at 25 m resolution. With the objective of mimicking the typical absence of well-distributed hard reference data, the simulations were only conditioned on local prior class probabilities and semi-variograms. Output was evaluated on the basis of reproduction of target levels of (1) cover type proportions, (2) overall class label accuracy and (3) spatially averaged local Shannon entropy. As expected, the realized statistics differed significantly from the target levels. However, the differences were consistent over the borders and the insides of map tiles. Thus, they did not result from the tiled map procedure but rather should be attributed to the used semi-conditional sequential indicator simulator. The current implementation can easily be adapted to accept other simulation algorithms
    Drought in groundwater-drought distribution and performance indicators
    Peters, E. ; Lanen, H.A.J. van; Torfs, P.J.J.F. ; Bier, G. - \ 2005
    Journal of Hydrology 306 (2005)1-4. - ISSN 0022-1694 - p. 302 - 317.
    droogte - grondwateraanvulling - tijdreeksen - meteorologie - grondwater - watersystemen - bodemwaterbalans - klimaat - drought - groundwater recharge - time series - meteorology - groundwater - water systems - soil water balance - climate - vulnerability - reliability - precipitation - resilience - simulation - frequency - reservoir - series
    In order to investigate how droughts are changed by the groundwater system and to analyse the performance of groundwater during drought, 10 time series of 1000 years of recharge and groundwater discharge were generated. The 10×1000 years of synthetic daily data were generated using Nearest Neighbour resampling based on 37 years of observed daily meteorological data. The root zone was simulated by a non-linear water balance model and the groundwater system by a linear reservoir model. The size and thus the response time of the reservoir was characterised by a reservoir coefficient. Subsequently, the deficit and duration of the droughts were derived from the time series of recharge and groundwater discharge using the threshold level approach. An analysis of the distribution of these droughts shows that for droughts with small return periods, the deficit in the groundwater discharge is smaller than in the recharge. For droughts with large return periods, the deficit in the groundwater discharge is larger than in the recharge. The performance of groundwater systems with respect to droughts was evaluated using three classical performance indicators (reliability, resilience and vulnerability), a combination of these three indicators (Loucks' sustainability index) and three newly defined overall performance indicators. The newly defined indicators combine the severity and frequency of the droughts, instead of analysing these separately in reliability and vulnerability. The performance is estimated for the groundwater recharge and for the discharge of groundwater systems with three different values of the reservoir coefficient. Of all the performance indicators used, one of the newly introduced overall performance indicators with a strong emphasis on droughts with a high return period appeared to characterise the groundwater droughts best. This indicator shows a more or less constant performance for low and medium high reservoir coefficients and an increasing performance for higher reservoir coefficients
    Temporal and spatial distribution of microcrustacean zooplankton in relation to turbidity and other environmental factors in a large tropical lake (L. Tana, Ethiopia)
    Dejen, E. ; Vijverberg, J. ; Nagelkerke, L.A.J. ; Sibbing, F.A. - \ 2004
    Hydrobiologia 513 (2004)1-3. - ISSN 0018-8158 - p. 39 - 49.
    barbs barbus-humilis - aquatic organisms - suspended clay - population-dynamics - community structure - reservoir - reproduction - cladocerans - abundance - dispersal
    The spatial and seasonal distribution of microcrustacean zooplankton of Lake Tana (Ethiopia) was monthly studied for 2 years. Concurrently, various environmental parameters were measured and related to zooplankton distribution. Canonical Correspondence Analysis (CCA) was used to estimate the influence of abiotic factors and chlorophyll a content in structuring the zooplankton assemblage. Among the environmental factors, zooplankton abundance correlated most strongly with turbidity. Turbidity was negatively correlated with species abundance, especially for Daphnia spp. and to the least extent for Diaphanosoma spp. Analysis of variance (ANOVA) was used to determine spatial (littoral, sublittoral and pelagic zone) and temporal (four seasons) variation in zooplankton abundance. We observed significant temporal differences in zooplankton abundance, with highest densities during dry season (November-April). Only cladocerans showed significant differences in habitat use (highest densities in the sublittoral zone).
    Isolation of thermophilic Desulfotomaculum strains with methanol and sulphite from solfataric mud pools, and characterization of Desulfotomaculum solfataricum
    Goorissen, H.P. ; Stams, A.J.M. ; Hansen, T.A. - \ 2003
    International Journal of Systematic and Evolutionary Microbiology 53 (2003). - ISSN 1466-5026 - p. 1223 - 1229.
    sulfate-reducing bacterium - oil-field waters - gen-nov - anaerobic bacterium - thermodesulfobacterium-commune - reductive dechlorination - marine sediment - tetrachloroethene - reservoir - deep
    Four strains of thermophilic, endospore-forming, sulfate-reducing bacteria were enriched and isolated from hot solfataric fields in the Krafla area of north-east Iceland, using methanol and sulfite as substrates. Morphologically, these strains resembled thermophilic Desulfotomaculum species. The strains grew with alcohols, including methanol, with glucose and fructose as electron donors, and with sulfate, sulfite or thiosulfate as electron acceptors. For all four strains, the optimum temperature and pH for growth were 60 degreesC and pH 7.3, respectively; no added NaCl was required. Phylogenetic analysis based on partial 16S rRNA gene sequence comparisons showed high levels of similarity of the novel strains (> 92 %) with Desulfotomaculum kuznetsovii and Desulfotomaculum luciae. However, DNA-DNA hybridization studies with D. kuznetsovii revealed that the four strains belonged to one novel species. A representative of this group of isolates, strain V21(T), is proposed as the type strain of a novel species of the spore-forming, sulfate-reducing genus Desulfotomaculum, namely Desulfotomaculum solfataricum (type strain V21(T) = DSM 114956(T) = CIP 107984(T)).
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