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.

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Fatty acids and proteins from marine cold adapted microalgae for biotechnology
Schulze, Peter S.C. ; Hulatt, Christopher J. ; Morales-Sánchez, Daniela ; Wijffels, René H. ; Kiron, Viswanath - \ 2019
Algal Research 42 (2019). - ISSN 2211-9264
Cold water algae - Eicosapentaenoic acid (EPA) - Light - Polyunsaturated fatty acid (PUFA) - Protein - Temperature

Cold-adapted microalgae display unexpectedly high biomass production, pointing to their potential to produce high-value bioproducts under cold and light-limited conditions. From culture collections, we screened eight cold-adapted strains of different genera (Chlamydomonas, Chlorella, Tetraselmis, Pseudopleurochloris, Nannochloropsis and Phaeodactylum) for the production of fatty acids and proteins under low temperature and light regimes (T = 8, 15 °C; I = 50, 100 μmol s−1 m−2). Among the strains, the Arctic isolate Chlamydomonas sp. (RCC 2488) had better growth at 8 °C compared to 15 °C (up to 0.5 gDW L−1 d−1) and highest productivities of protein and polyunsaturated fatty acids (PUFA) (70 and 65 mg L−1 d−1, respectively). Two tested Tetraselmis strains (SAG 1.96, RCC 2604) achieved highest biomass productivities (0.7–1 gDW L−1 d−1), containing up to 50 mg PUFA gDW−1 and 15% proteins. Pseudopleurochloris antarctica (SAG 39.98) grew well at 15 °C (0.4 g L−1 d−1), with 23% proteins in biomass and the highest eicosapentaenoic acid (EPA) productivity (7.6 mg L−1 d−1). Chlorella stigmatophora (RCC 661) achieved productivities of 0.4 gDW L−1 d−1 at 15 °C and produced extracellular polymeric substances (EPS). The major cause for the observed shifts in biochemical profiles was biomass concentration, which is an indicator for the prevailing growth stage. Based on the current experimental design, Chlamydomonas sp. (RCC 2488), T. chuii and P. antarctica can be suggested as the most promising strains for the production of protein and (polyunsaturated-) fatty acids at low temperatures. However, additional strain-specific studies are necessary to statistically validate these findings.

Fine-scale tracking of ambient temperature and movement reveals shuttling behavior of elephants to water
Thaker, Maria ; Gupte, Pratik R. ; Prins, Herbert H.T. ; Slotow, Rob ; Vanak, Abi T. - \ 2019
Frontiers in Ecology and Evolution 7 (2019)JAN. - ISSN 2296-701X
GPS telemetry - Habitat - Loxodonta africana - Shuttle - Temperature - Thermoregulation - Water

Movement strategies of animals have been well studied as a function of ecological drivers (e.g., forage selection and avoiding predation) rather than physiological requirements (e.g., thermoregulation). Thermal stress is a major concern for large mammals, especially for savanna elephants (Loxodonta africana), which have amongst the greatest challenge for heat dissipation in hot and arid environments. Therefore, elephants must make decisions about where and how fast to move to reduce thermal stress. We tracked 14 herds of elephant in Kruger National Park (KNP), South Africa, for 2 years, using GPS collars with inbuilt temperature sensors to examine the influence of temperature on movement strategies, particularly when accessing water. We first confirmed that collar-mounted temperature loggers captured hourly variation in relative ambient temperatures across the landscape, and, thus, could be used to predict elephant movement strategies at fine spatio-temporal scales. We found that elephants moved slower in more densely wooded areas, but, unexpectedly, moved faster at higher temperatures, especially in the wet season compared to the dry season. Notably, this speed of movement was highest when elephants were approaching and leaving water sources. Visits to water showed a periodic shuttling pattern, with a peak return rate of 10-30 h, wherein elephants were closest to water during the hotter times of the day, and spent longer at water sources in the dry season compared to the wet season. When elephants left water, they showed low fidelity to the same water source, and traveled farther in the dry season than in the wet season. In KNP, where water is easily accessible, and the risk of poaching is low, we found that elephants use short, high-speed bursts of movement to get to water at hotter times of day. This strategy not only provides the benefit of predation risk avoidance, but also allows them to use water to thermoregulate. We demonstrate that ambient temperature is an important predictor of movement and water use across the landscape, with elephants responding facultatively to a "landscape of thermal stress."

Removal of divalent ions from viscous polymer-flooding produced water and seawater via electrodialysis
Sosa-Fernandez, P.A. ; Post, J.W. ; Leermakers, F.A.M. ; Rijnaarts, H.H.M. ; Bruning, H. - \ 2019
Journal of Membrane Science 589 (2019). - ISSN 0376-7388
Desalination - Divalent ions - Partially hydrolyzed polyacrylamide - Temperature - Viscosity

The presence of multivalent ions in polymer-flooding produced water (PFPW) hampers its recycling mainly because i) they increase the risk of scaling and reservoir souring (sulfate), ii) they interfere with the viscosifying effect of the fresh polyelectrolyte. It is desirable to achieve the removal of most multivalent ions without completely desalting the stream. With the adequate process conditions, electrodialysis could help to achieve this goal, so this work focused on evaluating the removal of divalent ions from synthetic PFPW through varying operational conditions. The experimental work consisted on batch experiments run in an electrodialysis-stack composed of strong Neosepta ion-exchange membranes. Synthetic PFPW solutions containing a mixture of monovalent and divalent ions were desalted at four different current densities, and three different temperatures. Additionally, the effect of the dissolved polymer on the removal was assessed by performing half of the experiments on polymer-containing solutions and half of them on solutions without it. Our results demonstrate that it is possible to achieve preferential removal of divalent cations (calcium and magnesium) through electrodialysis, especially when employing low current densities (24 A/m2) and high temperature (40 °C). The removal of sulfate, a divalent anion, is also accelerated in these conditions. The presence of polyelectrolyte did not significantly affect the removal rate of divalent ions. Thus, it is concluded that meticulous application of ED to minimize concentrations of divalent ions in PFPW is a potential effective way for water and polymer recycling in enhanced oil recovery situations, as an alternative to the use of other non-selective desalination technologies.

Observed and model simulated twenty-first century hydro-climatic change of Northern Ethiopia
Tesfaye, Samuale ; Taye, Gebeyehu ; Birhane, Emiru ; Zee, Sjoerd E.A.T.M. van der - \ 2019
Journal of Hydrology: Regional Studies 22 (2019). - ISSN 2214-5818
Artificial neural networks - Climate change - GCM - Precipitation - Streamflow - Temperature

Study region: This study focuses on Tekeze river basin of northern Ethiopia, and it is characterized by a typical dry biogeophysical environment. Study focus: In recent years, recurrent droughts are having an adverse impact on agricultural production and water resources in northern Ethiopia. Climate change through changes on temperature, precipitation and streamflow, may further strain this critical situation. This study has investigated the observed (1961–2014) and potential (2006–2099) hydro-climatic changes in Tekeze river basin of northern Ethiopia. Artificial Neural Networks (ANNs) are used to downscale temperature and precipitation predicated by 30 General Circulation Models (GCMs) as well as the projected streamflow changes for two Representative Concentration Pathways (RCP4.5 and RCP8.5) scenario. New hydrological insights for the region: Results indicate that the variability of climatic factors as temperature and precipitation was observed to be both spatially and temporally diverse for the considered Tekeze river basin. Accordingly, the response of streamflow was also spatiotemporally complex. GCMs were evaluated with several performance indictors regarding patterns in hydro-climatic variables. The analysis showed the superiority of the multimodel ensemble means compared with individual GCM output. GCM projections for the 21century indicate a gradual reductions in streamflow attributed to the combined effect of increasing temperature and decreasing precipitation. The persistent increase of temperature and decrease of precipitation will have negative impacts on water availability and agriculture, hence site specific adaptation strategies are necessary.

The frost wave hypothesis : How the environment drives autumn departure of migratory waterfowl
Xu, Fei ; Si, Yali - \ 2019
Ecological Indicators 101 (2019). - ISSN 1470-160X - p. 1018 - 1025.
Autumn migration - Food deterioration - Migration phenology - Temperature - Wind selectivity

Migration phenology plays a critical role in shaping bird life histories. While the spring migration phenology of birds has been widely studied, our understanding about the mechanisms underlying autumn migration is limited. Frost is an indicator of cold weather, food scarcity, and water unavailability, but how frost drives the autumn departure of migratory birds has not yet been quantified. In this study we propose the ‘frost wave hypothesis’, which posits that the autumn departure of waterfowl is driven by a successive wave of the onset of frost. Using bird satellite tracking data and generalized linear mixed models, we analyze how the departure probability of two waterfowl species during autumn migration is affected by frost, accumulated temperature, food, snow, ice, short-term weather conditions (i.e., wind, temperature and precipitation), remaining migration distances, relative stopover duration, and flight distances between stopover sites. We find that bird autumn departure probability sharply increases after the first frost spell when the accumulated temperature reaches 0 °C, facilitated by surface meridional wind and longer remaining migration distances. We underline the dominant effect of frost on autumn departure, as birds tend to leave even under head wind if the time lag since the onset of frost is large. Time constraints that trigger southward departure are likely to be stronger when migrating birds are still far from their wintering site. By riding the frost wave, birds manage to maximize stopover site utilization while escaping harsh environmental conditions. Our findings improve the understanding of annual avian migration and help quantify the impact of global climate change on migratory waterfowl.

Genetic dissection of flowering time in Brassica rapa responses to temperature and photoperiod
Xiao, Dong ; Shen, Hao Ran ; Zhao, Jian Jun ; Wei, Yan Ping ; Liu, Dong Rang ; Hou, Xi Lin ; Bonnema, Guusje - \ 2019
Plant Science 280 (2019). - ISSN 0168-9452 - p. 110 - 119.
Brassica rapa - FLOWERING LOCUS C (FLC) - Flowering time - Photoperiod - QTL mapping - Temperature

The Brassica rapa (B. rapa) species displays enormous phenotypic diversity, with leafy vegetables, storage root vegetables and oil crops. These different crops all have different flowering time, which determine their growing season and cultivation area. Little is known about the effects of diverse temperature and day-lengths on flowering time QTL associated with FLC paralogues. We phenotyped the flowering time of a doubled haploid population, established from a cross between Yellow sarson and Pak choi under diverse environmental conditions. We identified flowering-time QTL (fQTL) in different photoperiod and temperature regimes in the greenhouse, and studied their colocation with known flowering time genes. As several fQTL colocalized with FLC paralogues, we studied the expression patterns of four FLC paralogues during the course of vernalization in parental lines. Under all environmental conditions tested the major fQTL that mapped to the BrFLC2_A02 locus was detected, however its effect decreased when plants were grown at low temperatures. Another fQTL that mapped to the FLC paralogue, BrFLC5_A03 was also identified under all tested environments, while no fQTL colocated with BrFLC1_A10 or BrFLC3_A03. Furthermore, the vernalization treatment decreased expression of all BrFLC paralogues in the parental lines, and showed the lowest transcript level after 28 days of vernalization. Transcript abundance stayed low after returning the plants for seven days to normal growth temperature. Interestingly, transcript abundance of BrFLC3_A03 and BrFLC5_A03 was repressed much stronger and already reached lowest levels after 14d in the early-flowering type YS-143. This study improves understanding of the effects of daylength and vernalization on flowering time in B. rapa and the role of the different BrFLC paralogues therein.

Determining sectoral and regional sensitivity to climate and socio-economic change in Europe using impact response surfaces
Fronzek, Stefan ; Carter, Timothy R. ; Pirttioja, Nina ; Alkemade, Rob ; Audsley, Eric ; Bugmann, Harald ; Flörke, Martina ; Holman, Ian ; Honda, Yasushi ; Ito, Akihiko ; Janes-Bassett, Victoria ; Lafond, Valentine ; Leemans, Rik ; Mokrech, Marc ; Nunez, Sarahi ; Sandars, Daniel ; Snell, Rebecca ; Takahashi, Kiyoshi ; Tanaka, Akemi ; Wimmer, Florian ; Yoshikawa, Minoru - \ 2019
Regional Environmental Change 19 (2019)3. - ISSN 1436-3798 - p. 679 - 693.
Gross domestic product (GDP) - Impact model - Population - Precipitation - Sensitivity analysis - Temperature

Responses to future changes in climatic and socio-economic conditions can be expected to vary between sectors and regions, reflecting differential sensitivity to these highly uncertain factors. A sensitivity analysis was conducted using a suite of impact models (for health, agriculture, biodiversity, land use, floods and forestry) across Europe with respect to changes in key climate and socio-economic variables. Depending on the indicators, aggregated grid or indicative site results are reported for eight rectangular sub-regions that together span Europe from northern Finland to southern Spain and from western Ireland to the Baltic States and eastern Mediterranean, each plotted as scenario-neutral impact response surfaces (IRSs). These depict the modelled behaviour of an impact variable in response to changes in two key explanatory variables. To our knowledge, this is the first time the IRS approach has been applied to changes in socio-economic drivers and over such large regions. The British Isles region showed the smallest sensitivity to both temperature and precipitation, whereas Central Europe showed the strongest responses to temperature and Eastern Europe to precipitation. Across the regions, sensitivity to temperature was lowest for the two indicators of river discharge and highest for Norway spruce productivity. Sensitivity to precipitation was lowest for intensive agricultural land use, maize and potato yields and Scots pine productivity, and highest for Norway spruce productivity. Under future climate projections, North-eastern Europe showed increases in yields of all crops and productivity of all tree species, whereas Central and East Europe showed declines. River discharge indicators and forest productivity (except Holm oak) were projected to decline over southern European regions. Responses were more sensitive to socio-economic than to climate drivers for some impact indicators, as demonstrated for heat-related mortality, coastal flooding and land use.

Application of manganese oxides under anoxic conditions to remove diclofenac from water
Liu, Wenbo ; Langenhoff, Alette A.M. ; Sutton, Nora B. ; Rijnaarts, Huub H.M. - \ 2018
Journal of Environmental Chemical Engineering 6 (2018)4. - ISSN 2213-2929 - p. 5061 - 5068.
Anoxic abiotic pharmaceutical removal - Application - Co-solutes - Manganese oxides - MnO:diclofenac ratio - Temperature

This study focuses on the potential of applying manganese oxides (MnO2) under anoxic conditions (absence of oxygen) to remove diclofenac (DFC). By investigating parameters that are important for application, including temperature, MnO2: DFC molar ratio, and co-solutes, the DFC removal potential is evaluated in terms of efficiency and observed initial kinetics (kobs,init). Four commonly-used kinetic models are compared in this study and the best fitting one is employed. Overall, DFC removal and kobs,init both increase upon changing temperature from 10 to 30°C and both decrease after further increasing temperature to 40°C. Increasing the MnO2: DFC molar ratio improves degradation, as this provides more reactive surface sites for DFC conversions. However, DFC removal does not further increase when increasing the MnO2:DFC from 2200:1 to 8900:1. The presence of metal ions inhibits DFC removal, possibly because the ions adsorb onto the reactive sites at the MnO2 surface and compete with DFC. Phosphate has a diverse effect on DFC degradation: low concentrations inhibit and high concentrations promote removal. The presence of humic acids significantly promotes diclofenac removal. These findings are a first step towards further developing pharmaceutical removal technology using MnO2 under anoxic conditions.

Optimizing air flow distribution in maritime refrigerated containers
Lukasse, L.J.S. ; Staal, M.G. - \ 2018
In: 8th International Postharvest Symposium. - International Society for Horticultural Science (Acta Horticulturae ) - ISBN 9789462611900 - p. 1391 - 1398.
Cover - Gradient - Homogeneity - Reefer - T-bar - Temperature - Uniformity
Ever more intercontinental fruit transport takes place in reefer containers. The global installed fleet of 40 ft high cube reefer containers counts approximately 1,000,000 units. The reefer market has generally realized a compound annual growth (CAGR) of 5%. Product temperature requirements are very tight for highly temperature-sensitive fruit like grape and kiwi. Another application where temperature requirements are particularly tight is in cold treatment shipments, required as a quarantine measure by authorities of importing countries. In cold treatment shipments it is often hard to maintain the warmest product temperature below the regulatory imposed treatment limit, without causing chilling injury in the cold spots. Temperature gradients are reduced by good air flow distribution. T-bars make up the air ducts of reefer containers. Unfortunately most air escapes from the ducts before reaching the container door-end if no further measures are taken. An appropriate T-floor cover could help to guide more air to the locations where it is needed most. This paper reports on an experimental study with the aim to design an optimised T-floor cover and assess its effect on fruit temperature distribution. In a series of climate chamber tests it is investigated how temperature gradients are affected by four different T-bar cover designs. During the tests the container is stuffed with palletized empty cartons, with zero autonomous heat production. The results show clear positive effects of T-bar covers. The best of the four covers is non-perforated, of a trapezoidal-like shape, installed in the container with the narrowest end towards the door-end. It reduces the temperature difference between warmest and coldest measurement location by nearly 50%, and also accelerates temperature recovery after a power off period. In view of the promising results it is recommended to follow-up with real transport tests.
Re-evaluating the role of bacteria in gerbera vase life
Schouten, Rob E. ; Verdonk, Julian C. ; Meeteren, Uulke van - \ 2018
Postharvest Biology and Technology 143 (2018). - ISSN 0925-5214 - p. 1 - 12.
Antimicrobial compounds - Elongation - Temperature - Transpiration - Water uptake
The relation between bacteria numbers in vase water and vase life of gerbera cut flowers has recently been challenged because of reported negative effects of bactericidal compounds. This relation is investigated using two types of experiments that do not rely on antimicrobial compounds. The first type controls vase water temperature (4, 15, 22 or 28 °C) independently from air temperature (15, 22 or 28 °C) to investigate whether fresh weight behavior for two mini gerbera cultivars (‘Okidoki’ and ‘Kimsey’) is affected by bacterial growth and leaking of soluble sugars in the vase water, or by senescence of the flower head. Fresh weight loss, when compared at constant water temperatures, was higher at higher air temperatures. At higher water temperatures and constant air temperatures fresh weight loss was not higher, although bacterial levels were high enough to expect water uptake issues. Also sugar consumption in the vase water depended on water temperature. This indicates that senescence was the main reason for the decline in fresh weight for these flowers, not bacterial growth. The second type of experiments was based on adding predetermined levels of bacteria (0, 103 or 105 CFU mL−1) and sugars (0.1% glucose or 0.2% sucrose) into vase water of flowers of three large-bloomed (‘Carambole’, ‘Candela’ and ‘Iceberg’) cultivars harvested with closed stem-ends and had their scapes sterilized before the start of vase life. When bacteria were added varying types of responses were observed. ‘Carambole’ flowers showed lower water uptake and lower transpiration and, early scape bending. Petal wilting was observed for ‘Candela’ flowers. ‘Carambole’ flowers showed higher scape sugar leakage levels in the vase water while ‘Candela’ flowers had higher scape firmness. ‘Iceberg’ flowers were also affected by bacteria, resulting in early scape bending, although sugar levels in the vase water were low. Furthermore, adding sucrose and/or bacteria in the vase water of one ‘Iceberg’ and one ‘Carambole’ flower in the same flask resulted in later scape bending for ‘Iceberg’ flowers compared to having two ‘Carambole’ or two ‘Iceberg’ flowers. The results indicate that bacteria interactions with gerbera flowers depend strongly on genotype.
Factors that inhibit growth of Listeria monocytogenes in nature-ripened Gouda cheese: A major role for undissociated lactic acid
Wemmenhove, E. ; Valenberg, H.J.F. van; Hooijdonk, A.C.M. van; Wells-Bennik, M.H.J. ; Zwietering, M.H. - \ 2018
Food Control 84 (2018). - ISSN 0956-7135 - p. 413 - 418.
Acetic acid - Diacetyl - Free fatty acids - Gouda cheese - Growth inhibition - Growth limit - L. monocytogenes - Lactoferrin - Nisin - Nitrate - Nitrite - pH - Safety criteria - Temperature - Undissociated lactic acid - Water activity
In this study, factors relevant to nature-ripened Gouda cheese were evaluated for their potential to inhibit growth of Listeria monocytogenes. Factors included water activity, pH, undissociated acetic and lactic acid, diacetyl, free fatty acids, lactoferrin, nitrate, nitrite and nisin. In addition, the effect of temperature was evaluated. For each factor, the actual concentrations and values relevant to Gouda cheese were obtained and the inhibitory effect of these individual factors on growth of L. monocytogenes was assessed. This evaluation revealed that undissociated lactic acid is the most important factor for growth inhibition of L. monocytogenes in Gouda cheese and that, additionally, low water activity as present in the cheese rind and after prolonged ripening times can also cause full growth inhibition. Gouda cheeses have a typical total lactic acid content of 1.47% w/w. In a 2-week old Gouda cheese, with a pH value of 5.25 and a moisture content of 42% w/w, the concentration of undissociated lactic acid in the water phase is 10.9 mM. Growth of L. monocytogenes is not supported when the undissociated lactic acid concentration is > 6.35 mM. Concentrations of undissociated lactic acid in the water phase of Gouda cheese will be higher than this value when the total lactic acid content is > 0.86% w/w at a pH < 5.25 (relevant to young Gouda cheese), or > 1.26% w/w at a pH < 5.50 for mature Gouda cheese (moisture content of 35% w/w). This study underlines the importance of undissociated lactic acid as growth inhibitor for L. monocytogenes in Gouda cheese.
Effects of long-term deforestation and remnant forests on rainfall and temperature in the Central Rift Valley of Ethiopia
Muluneh, Alemayehu ; Loon, Emiel van; Bewket, Woldeamlak ; Keesstra, Saskia ; Stroosnijder, Leo ; Burka, Ashenafi - \ 2017
Forest Ecosystems 4 (2017)1. - ISSN 2095-6355
Deforestation - Elevation - Forest - Rainfall - Slope - Temperature

Background: Some evidence suggests that forests attract rain and that deforestation contributes to changes in rainfall and temperature. The evidence, however, is scant, particularly on smaller spatial scales. The specific objectives of the study were: (i) to evaluate long-term trends in rainfall (1970–2009) and temperature (1981–2009) and their relationships with change in forest cover, and (ii) to assess the influence of remnant forests and topographical factors on the spatial variability of annual rainfall. Methods: This study investigated the forest-rainfall relationships in the Central Rift Valley of Ethiopia. The study used 16 long-term (1970–2009) and 15 short-term (2012–2013) rainfall and six long term (1981–2009) temperature datasets. Forest and woodland cover decline over the past 40 years (1970–2009) and the measured distances between the remnant forests and rainfall stations were also used. The long-term trends in rainfall (1970–2009) and temperature (1981–2009) were determined using Mann-Kendall (MK) and Regional Kendall (RK) tests and their relationships with long-term deforestation were evaluated using simple linear regression. Influence of remnant forests and topographical variables on the spatial variability of rainfall were determined by stepwise multiple regression method. A continuous forest and woodland cover decline was estimated using exponential interpolation. Results: The forest and woodland cover declined from 44% in 1973 to less than 15% in 2009 in the Central Rift Valley. Annual rainfall on the valley floor showed an increase by 37.9 mm/decade while annual rainfall on the escarpments/highlands decreased by 29.8 mm/decade. The remnant forests had a significant effect (P-value <0.05, R2 = 0.40) on the spatial variability of the number of rainy days observed over two years (2012–2013), but had little effect on the variability of rainfall distribution. For the total annual rainfall, slope was the best predictor which explained 29% of the rainfall variability in the Central Rift Valley. For the annual number of rainy days, both slope and elevation explained most of the variability (60%) of annual number of rainy days. Conclusion: This study did not find a significant correlation between long-term rainfall trend and forest and woodland cover decline. The rift valley floor warmed significantly due to long-term deforestation in the Central Rift Valley. Topographic factors play a significant role than forest cover in explaining the spatial variability of annual rainfall in the long-term and short term time scale in the Central Rift Valley. But, the short-term rainfall data indicated that the remnant forest had a significant effect on the spatial variability of the number of rainy days.

Near-surface temperature inversion growth rate during the onset of the stable boundary layer
Hooijdonk, Ivo G.S. van; Clercx, Herman J.H. ; Abraham, Carsten ; Holdsworth, Amber M. ; Monahan, Adam H. ; Vignon, Etienne ; Moene, Arnold F. ; Baas, Peter ; Wiel, Bas J.H. van de - \ 2017
Journal of the Atmospheric Sciences 74 (2017)10. - ISSN 0022-4928 - p. 3433 - 3449.
Boundary layer - Classification - In situ atmospheric observations - Radiative forcing - Single column models - Temperature

This study aims to find the typical growth rate of the temperature inversion during the onset of the stable boundary layer around sunset.The sunset transition is a very challenging period for numerical weather prediction, since neither accepted theories for the convective boundary layer nor those for the stable boundary layer appear to be applicable. To gainmore insight in this period, a systematic investigation of the temperature inversion growth rate is conducted. A statistical procedure is used to analyze almost 16 years of observations from the Cabauw observational tower, supported by observations from two additional sites (DomeCandKarlsruhe). The results show that, on average, the growth rate of the temperature inversion (normalized by the maximum inversion during the night) weakly declines with increasing wind speed. The observed growth rate is quantitatively consistent among the sites, and it appears insensitive to various other parameters. The results were also insensitive to the afternoon decay rate of the net radiation except when this decay rate was very weak. These observations are compared to numerical solutions of three models with increasing complexity: a bulk model, an idealized single-column model (SCM), and an operational-level SCM. It appears only the latter could reproduce qualitative features of the observations using a first-order closure. Moreover, replacing this closure with a prognostic TKE scheme substantially improved the quantitative performance. This suggests that idealized models assuming instantaneous equilibrium flux-profile relations may not aid in understanding this period, since history effects may qualitatively affect the dynamics.

Influence of light and temperature on flower development in gerbera
Dueck, T.A. ; Kempkes, F.L.K. ; Helm, F. Van Der; Groot, M. De - \ 2017
In: International Symposium on New Technologies and Management for Greenhouses - GreenSys2015 International Society for Horticultural Science (Acta Horticulturae ) - ISBN 9789462611665 - p. 943 - 950.
Gerbera - HPS - Hybrid - LED - Light sum - Photoperiod - Temperature
Higher intensities artificial lighting are currently being installed for gerbera crops, mainly because of the relatively low costs of high-capacity HPS lamps with a higher light output. In addition, LED lighting systems are becoming even more efficient. In order to gain insight on increasing production with various high-capacity lighting systems, an experiment was performed with three lighting systems. Gerbera, cv. Kimsey was grown under HPS, hybrid (combination of HPS and LED) and under a LED lighting system in three greenhouses of 144 m2. Different light and temperature set points were used to investigate the effects of the light sum and light spectrum in combination with greenhouse air temperature and plant temperature on growth, development and production. A lower plant temperature under HPS lighting with lower air temperatures was expected to result in more generative growth, but this did not appear to be the case. Even though, gerbera under HPS during the winter months produced more flowers, but overall the differences in production under HPS and LED lighting were small. Although growers suspected that under LED-lighting, either a hybrid or LED-only lighting system, botrytis infection might increase due to the lack of radiative heat for the crop, no increase in botrytis infection was observed. Additional measurements of air and plant temperature under HPS and LED lighting were performed to investigate the influence of both factors on the initiation and development rate of gerbera flowers. These results are presented and discussed in the light of optimizing cultivation conditions for gerbera.
Numerical simulation of the effect of different mulches on the heat storage capacity of a Mediterranean greenhouse soil
Baeza, E.J. ; Sapounas, A. ; Stanghellini, C. ; Bonachela CastaAo, S. ; Hernández, J. ; Montero, J.I. ; López, J.C. ; Granados, M.R. ; Muñoz, P. ; Lorenzo, P. ; Fernández-Del Olmo, P. - \ 2017
In: International Symposium on New Technologies and Management for Greenhouses - GreenSys2015 International Society for Horticultural Science (Acta Horticulturae ) - ISBN 9789462611665 - p. 119 - 127.
Black film - CFD - Sand - Semi-transparent film - Temperature
In the Mediterranean greenhouse areas, a large majority of growers rely on passive techniques to improve the microclimate of the greenhouse during the winter period, rather than using more expensive systems such as active heating. Some of these techniques such as different types of mulch (sand, plastic films, etc.) are used to improve the heat storage capacity of the greenhouse soil. A proper modeling of the role of the greenhouse soil a heat store would allow the verification of which techniques have a larger positive effect on the heat store capacity of the soil (i.e. type, color and thickness of the mulch, soil moisture content, etc.) and how to optimize their management by the grower. In recent years, CFD has been successfully used to model the greenhouse microclimate under very different scenarios, but little has been done to include in the simulations the role of passive techniques in the winter period microclimate, such as the role of the soil as a heat store. In the present work, a CFD model of a Mediterranean greenhouse and its soil has been developed, and the effect on the heat storage capacity of the soil as well as in the ambient of 2 different types of mulch (black plastic film, semi-transparent plastic film) was evaluated, by comparing the temperature measured at 4 different depths and ambient temperature (at two heights), during daytime period with the values provided by the model. The evolution of the temperatures at different soil depths followed the same pattern in both the experiments and the simulations. Good quantitative agreement was found between values predicted by the model and the measurements with differences being always lower than 2°C.
How to quench your thirst. The effect of water-based products varying in temperature and texture, flavour, and sugar content on thirst
Belzen, L. van; Postma, E.M. ; Boesveldt, S. - \ 2017
Physiology and Behavior 180 (2017). - ISSN 0031-9384 - p. 45 - 52.
Liquids - Saliva - Solids - Temperature - Thirst - Thirst-quenching
The sensation of thirst plays an important role in the consumption of water or other fluids to rehydrate the body in order to keep bodily functions working properly. An increase in saliva secretion, wetting the mouth by ingestion of liquids, and cooling and sour components in products can alleviate this sensation already before absorption of fluids by the body. This study aimed to investigate the thirst-quenching ability of water-based products differing in temperature and texture (cold solids and cool liquids), flavour (flavoured and non-flavoured) and sugar content in two consecutive experiments. The first experiment tested four products of 10 ml each (flavoured popsicles, flavoured beverages, ice cubes, and water). 45 healthy, thirsty participants (8 men and 37 women, mean age 25.7 years SD ± 6.6) were randomly assigned to a flavour group representing the flavour of the popsicles and beverages: mint, lemon, raspberry. Each flavour group tasted all four products (popsicles, beverages, water, ice cubes) in four sessions on consecutive days. Participants rated their thirst and four attributes (flavour intensity, thirst-quenching, refreshing, saliva stimulating) during 3 min of consumption on a 100 mm VAS scale and ranked all four products on thirst-quenching ability at the end of the last session. The second experiment was performed similarly (n = 61, 6 men and 55 women, mean age 23.5 years SD ± 2.87), but used sugar-reduced popsicles to compare to the regular popsicles from the first experiment. In addition, saliva was collected before and after consumption. In the first experiment, cold solid (55.8 ± 0.99) and flavoured (55.9 ± 0.95) products were found to be more thirst-quenching than cool liquid (52.8 ± 0.96) and non-flavoured products (52.8 ± 0.96). The second experiment confirmed that saliva production increased upon consumption of these popsicles, with an increase of saliva weight from 1.7 g SD ± 0.15 before consumption to 2.0 SD ± 0.22 after consumption. Sugar-reduced popsicles were similar in thirst-quenching ability compared to regular popsicles. Overall, cold, solid, flavoured products (such as popsicles) performed best in quenching thirst, and it appeared that sugar-reduction in these products to create healthier alternatives can be achieved without compromising on thirst-quenching abilities. These results can be useful for optimisation of products to alleviate thirst in daily life, as well as in clinical settings for patients where fluid restriction is needed.
Comparative life history traits of indigenous Italian parasitoids of Drosophila suzukii and their effectiveness at different temperatures
Rossi Stacconi, Marco Valerio ; Panel, Aurore ; Baser, Nuray ; Ioriatti, Claudio ; Pantezzi, Tommaso ; Anfora, Gianfranco - \ 2017
Biological Control 112 (2017). - ISSN 1049-9644 - p. 20 - 27.
Leptopilina heterotoma - Longevity - Pachycrepoideus vindemiae - Spotted wing drosophila - Temperature - Trichopria drosophilae

Drosophila suzukii, or spotted wing drosophila (SWD), is a highly polyphagous invasive pest which has recently invaded Europe and the Americas. Its huge economic impact is due in part to the lack of specialised natural enemies suppressing population outbreaks in newly invaded areas. By establishing new associations, endemic parasitoid species native to the invaded areas can play an important role in controlling the pest. This study aims to provide a range of baseline information on the developmental parameters and parasitisation efficacy of three Italian populations of D. suzukii parasitoids at different temperatures. The species tested were a larval parasitoid, Leptopilina heterotoma (Thomson), and two pupal parasitoids, Pachycrepoideus vindemiae (Rondani) and Trichopria drosophilae (Perkins). Two comparative experiments were set up: the first assessing longevity and the lifetime fecundity of each species at 23 °C, and the second investigating the effect of temperature on parasitisation efficacy, developmental time and sex-ratio. The results revealed different fecundity patterns for the three parasitoids, probably due to a different level of synovigeny. For T. drosophilae and P. vindemiae, the lifetime sex ratio was biased towards an increasing number of males, whereas L. heterotoma showed the opposite trend. Moreover, temperature markedly affected host-parasitoid interaction and was positively correlated with the parasitoid's developmental time, whereas the sex-ratio was not significantly influenced. On the basis of these experiments, T. drosophilae appears to be the best candidate for developing a biological control strategy.

Long-term patterns in fish phenology in the western Dutch Wadden Sea in relation to climate change
Walraven, Lodewijk Van; Dapper, Rob ; Nauw, Janine J. ; Tulp, Ingrid ; Witte, Johannes IJ. ; Veer, Henk W. van der - \ 2017
Journal of Sea Research 127 (2017). - ISSN 1385-1101 - p. 173 - 181.
Long-term changes - Phenology - Fish fauna - Wadden Sea - Temperature
Long-term patterns in fish phenology in the western Dutch Wadden Sea were studied using a 53 year (1960–2013) high resolution time series of daily kom-fyke catches in spring and autumn. Trends in first appearance, last occurrence and peak abundance were analysed for the most common species in relation to mode of life (pelagic, demersal, benthopelagic) and biogeographic guild (northern or southern distribution). Climate change in the western Wadden Sea involved an increase in water temperature from 1980 onwards. The main pattern in first day of occurrence, peak occurrence and last day of occurrence was similar: a positive trend over time and a correlation with spring and summer water temperature. This is counterintuitive; with increasing temperature, an advanced immigration of fish species would be expected. An explanation might be that water temperatures have increased offshore as well and hence fish remain longer there, delaying their immigration to the Wadden Sea. The main trend towards later date of peak occurrence and last day of occurrence was in line with our expectations: a forward shift in immigration into the Wadden Sea implies also that peak abundance is delayed. As a consequence of the increased water temperature, autumn water temperature remains favourable longer than before. For most of the species present, the Wadden Sea is not near the edge of their distributional range. The most striking phenological shifts occurred in those individual species for which the Wadden Sea is near the southern or northern edge of their distribution.
Digital growth response maps for assessment of cooling requirement in greenhouse production of tomato
Shamshiri, R. ; Che Man, H. ; Zakaria, A.J. ; Beveren, Peter van; Wan Ismail, W.I. ; Ahmad, D. - \ 2017
Acta Horticulturae 1152 (2017). - ISSN 0567-7572 - p. 117 - 124.
Computer simulation - Cooling requirement - Greenhouse - Growth response map - Temperature - Tomato - Tropical lowland

The objective of this work was to generate a series of digital growth response maps that address specific times of cooling requirement for tomato production in a tropical lowland greenhouse. Collected data from a net-screen covered greenhouse were processed by a computer model that utilized a mathematical approach to simulate tomato's growth responses (GR) to air temperature at early growth and development growth stages. Orthogonal projection was applied on three-dimensional GR plots to create top-view sketch to demonstrate variations with respect to changes in hours and days. Results indicated that air temperature inside the greenhouse was 65% optimal at the early growth stage and 72% optimal at the development growth stage of tomato.

Combined physical, chemical and biological factors shape Alexandrium ostenfeldii blooms in the Netherlands
Brandenburg, Karen M. ; Senerpont Domis, Lisette N. de; Wohlrab, Sylke ; Krock, Bernd ; John, Uwe ; Scheppingen, Yvonne van; Donk, Ellen van; Waal, Dedmer B. van de - \ 2017
Harmful Algae 63 (2017). - ISSN 1568-9883 - p. 146 - 153.
Alexandrium - Grazing - Nutrients - Salinity - Temperature - Wind speed

Harmful algal blooms (HABs) are globally expanding, compromising water quality worldwide. HAB dynamics are determined by a complex interplay of abiotic and biotic factors, and their emergence has often been linked to eutrophication, and more recently to climate change. The dinoflagellate Alexandrium is one of the most widespread HAB genera and its success is based on key functional traits like allelopathy, mixotrophy, cyst formation and nutrient retrieval migrations. Since 2012, dense Alexandrium ostenfeldii blooms (up to 4500 cells mL−1) have recurred annually in a creek located in the southwest of the Netherlands, an area characterized by intense agriculture and aquaculture. We investigated how physical, chemical and biological factors influenced A. ostenfeldii bloom dynamics over three consecutive years (2013–2015). Overall, we found a decrease in the magnitude of the bloom over the years that could largely be linked to changing weather conditions during summer. More specifically, low salinities due to excessive rainfall and increased wind speed corresponded to a delayed A. ostenfeldii bloom with reduced population densities in 2015. Within each year, highest population densities generally corresponded to high temperatures, low DIN:DIP ratios and low grazer densities. Together, our results demonstrate an important role of nutrient availability, absence of grazing, and particularly of the physical environment on the magnitude and duration of A. ostenfeldii blooms. Our results suggest that predicted changes in the physical environment may enhance bloom development in future coastal waters and embayments.

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