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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    Mitigation options to reduce phosphorus losses from the agricultural sector and improve surface water quality: a review
    Schoumans, O.F. ; Chardon, W.J. ; Bechmann, M. ; Gascuel-Odoux, C. ; Hofman, G. ; Kronvang, B. ; Rubaek, G.H. ; Ulen, B. ; Dorioz, J.M. - \ 2014
    Science of the Total Environment 468-469 (2014). - ISSN 0048-9697 - p. 1255 - 1266.
    semiarid altered wetland - blue-green-algae - subsurface drainage - nutrient losses - fresh-water - particulate phosphorus - conservation tillage - constructed wetlands - manure application - buffer strips
    The EU Water Framework Directive (WFD) obliges Member States to improve the quality of surface water and groundwater. The measures implemented to date have reduced the contribution of point sources of pollution, and hence diffuse pollution from agriculture has become more important. In many catchments thewater quality remains poor. COST Action 869was an EU initiative to improve surfacewater quality that ran from2006 to 2011, in which 30 countries participated. Its main aim was a scientific evaluation of the suitability and costeffectiveness of options for reducing nutrient loss from rural areas to surface waters at catchment scale, including the feasibility of the options under different climatic and geographical conditions. This paper gives an overview of various categories of mitigation options in relation to phosphorus (P). The individual measures are described in terms of their mode of action, applicability, effectiveness, time frame, environmental side-effects (N cycling) and cost. In total, 83 measures were evaluated in COST Action 869.
    The effect of harvesting on biomass production and nutrient removal in phototrophic biofilm reactors for effluent polishing
    Boelee, N.C. ; Janssen, M. ; Temmink, H. ; Taparaviciute, L. ; Khiewwijit, R. ; Janoska, A. ; Buisman, C.J.N. ; Wijffels, R.H. - \ 2014
    Journal of Applied Phycology 26 (2014)3. - ISSN 0921-8971 - p. 1439 - 1452.
    afvalwaterbehandeling - biofilms - dikte - dichtheid - algen - biologische waterzuiveringsinstallaties - fototropie - stikstof - fosfor - verwijdering - biobased economy - waste water treatment - biofilms - thickness - density - algae - biological water treatment plants - phototropism - nitrogen - phosphorus - removal - biobased economy - waste-water treatment - photosynthetic efficiency - chlorella-sorokiniana - microalgal biofilms - phosphorus removal - mass-transport - fresh-water - light - growth
    An increasing number of wastewater treatment plants require post-treatment to remove residual nitrogen and phosphorus. This study investigated various harvesting regimes that would achieve consistent low effluent concentrations of nitrogen and phosphorus in a phototrophic biofilm reactor. Experiments were performed in a vertical biofilm reactor under continuous artificial lighting and employing artificial wastewater. Under similar conditions, experiments were performed in near-horizontal flow lanes with biofilms of variable thickness. It was possible to maintain low nitrogen and phosphorus concentrations in the effluent of the vertical biofilm reactor by regularly harvesting half of the biofilm. The average areal biomass production rate achieved a 7 g dry weight m-2 day-1 for all different harvesting frequencies tested (every 2, 4, or 7 days), corresponding to the different biofilm thicknesses. Apparently, the biomass productivity is similar for a wide range of biofilm thicknesses. The biofilm could not be maintained for more than 2 weeks as, after this period, it spontaneously detached from the carrier material. Contrary to the expectations, the biomass production doubled when the biofilm thickness was increased from 130 µm to 2 mm. This increased production was explained by the lower density and looser structure of the 2 mm biofilm. It was concluded that, concerning biomass production and labor requirement, the optimum harvesting frequency is once per week.
    Balancing carbon sequestration and GHG emissions in a constructed wetland
    Klein, J.J.M. de; Werf, A.K. van der - \ 2014
    Ecological Engineering 66 (2014). - ISSN 0925-8574 - p. 36 - 42.
    waste-water treatment - phragmites-australis - methane emission - nitrous-oxide - emergent macrophytes - ecosystem services - restored wetlands - greenhouse gases - fresh-water - denitrification
    In many countries wetlands are constructed or restored for removing nutrients from surface water. At the same time vegetated wetlands can act as carbon sinks when CO2 is sequestered in biomass. However, it is well known that wetlands also produce substantial amounts of greenhouse gasses CH4 and N2O. Especially N2O, resulting from nitrification and denitrification, is a very potent GHG. To assess the environmental sustainability of constructed wetlands the benefit of carbon sink and the downside of GHG emissions have to be evaluated. Since nutrient and carbon cycles in wetlands are complex and variable among wetlands and in time such a balance always contains uncertainties. Several studies have addressed this issue and indicated that CW can be either a sink or a source of CO2 equivalents depending on the time scale of research and the environmental and management conditions involved. Here we balance carbon sequestration with CH4 and N2O emissions in a multi-functional constructed wetland, dominated by emergent Phragmites vegetation. Detailed measurements were combined with a nitrogen budget, and all fluxes were expressed as a range indicating the uncertainties in measurements and extrapolation techniques. Measured methane emissions were variable and showed clear relationship with temperature and density of the emergent vegetation. Average CH4 emissions in the vegetation were 7.8 at 15 °C and 24.5 mg m-2 h-1 at 24 °C. Estimated N2O emissions ranged from 0.5 to 1.9 g m-2 y-1. After converting the fluxes to CO2 equivalents we concluded that the Lankheet constructed wetland is most likely a sink of CO2 in the present conditions. Annual net sequestration of CO2 amounts 0.27–2.4 kg m-2 y-1 which represents 12–67% of the CO2 fixation in the biomass. N2O emissions represent a substantial part of the total effect of GHG emissions (12–29%) and should not be disregarded in budget studies. We acknowledge the limitations and uncertainties of our estimates, however, we are confident that our findings contribute to assessing the environmental sustainability of constructed wetlands.
    The impact of elevated water nitrate concentration on physiology, growth and feed intake of African catfish Clarias gariepinus (Burchell 1822)
    Schram, E. ; Roques, J.A.C. ; Abbink, W. ; Vries, P. de; Bierman, S.M. ; Vis, J.W. van de - \ 2014
    Aquaculture Research 45 (2014)9. - ISSN 1355-557X - p. 1499 - 1511.
    acid-base-balance - rainbow-trout - fresh-water - oxygen-affinity - astacus-astacus - channel catfish - na+/k+-atpase - nitrite - transport - toxicity
    The nitrate threshold concentration in rearing water of African catfish (Clarias gariepinus) was assessed. Female African catfish with an initial mean (SD) weight of 154.3 (7.5) g were exposed to 0.4 (Control), 1.5, 4.2, 9.7 and 27.0 mM nitrate for 42 days. Mean (SD) plasma concentrations of nitrate increased from 71 (29) to 6623 (921) µM at the highest ambient nitrate level. Mean (SD) plasma nitrite concentration ranged from 1.2 (0.5) to 7.9 (9.0) µM. Haematocrit, plasma concentrations of non-esterified fatty acids (NEFA), cortisol, glucose, lactate, osmolality, gill morphology and branchial Na+/K+-ATPase activity were not affected. Feed intake and specific growth rate were significantly reduced at the highest nitrate concentration. We advise not to exceed a water nitrate concentration of 10 mM (140 mg L-1 NO3-N) to prevent the risk of reduced growth and feed intake in African catfish aquaculture.
    Interactive effects of pH, temperature and light during ammonia toxicity events in Elodea canadensis
    Netten, J.J.C. ; Heide, T. van der; Smolders, A.J.P. - \ 2013
    Chemistry and Ecology 29 (2013)5. - ISSN 0275-7540 - p. 448 - 458.
    eelgrass zostera-marina - submerged macrophytes - environmental-change - nutritional-status - water chemistry - aquatic plants - nh4+ toxicity - fresh-water - eutrophication - growth
    Increased nutrient loading threatens many freshwater ecosystems. Elevated temperatures may increase the sensitivity to eutrophication in these ecosystems. Higher concentrations of possibly toxic reduced nitrogen (NHx) in the water layer may be expected as production and anaerobic breakdown rates will increase. Apart from temperature, NHx and its effect on aquatic macrophytes will also depend on pH and light. We examined the interactive effects of NHx, temperature, pH and light on Elodea canadensis in a full factorial laboratory experiment. Results demonstrate that high NHx and high temperature together with low pH and low light causes the strongest toxic effects regarding relative growth rate and leaf tissue mortality. The adverse effects of high temperature and low light are most likely caused by increased metabolic activity and reduced photosynthesis, respectively. Severe toxicity at low pH compared to high pH can be ascribed to the ability of E. canadensis to induce a specialised bicarbonate-concentrating pathway at high pH, resulting in much higher carbon availability, needed for detoxification of NHx. We conclude that NHx toxicity will become more pronounced under higher temperatures, but that effects on aquatic macrophytes will strongly depend on pH of the water layer and specific metabolic adaptations of different species.
    Pesticide risk assessment and management in a globally chgangin world - report from a european interdisciplinary workshop
    Babut, M. ; Arts, G.H.P. ; Barra Caracciolo, A. ; Carluer, N. ; Domage, N. - \ 2013
    Environmental Science and Pollution Research 20 (2013)11. - ISSN 0944-1344 - p. 8298 - 8312.
    semipermeable-membrane devices - photosystem-ii inhibitors - passive sampling devices - climate-change - fresh-water - herbicide losses - surface-water - in-situ - environmental-protection - potential application
    A Device to Study the Behavioral Responses of Zooplankton to Food Quality and Quantity
    Bukovinszky, T. ; Helmsing, N.R. ; Grau, R.A. ; Bakker, E.S. ; Vos, M. ; UIttenhout, H. ; Verschoor, A.M. - \ 2013
    Journal of Insect Behavior 26 (2013)4. - ISSN 0892-7553 - p. 453 - 465.
    vertical migration - time allocation - daphnia-pulex - fresh-water - habitat - temperature - gradients - selection - culture - algae
    In order to explore the behavioral mechanisms underlying aggregation of foragers on local resource patches, it is necessary to manipulate the location, quality and quantity of food patches. This requires careful control over the conditions in the foraging arena, which may be a challenging task in the case of aquatic resource-consumer systems, like that of freshwater zooplankton feeding on suspended algal cells. We present an experimental tool designed to aid behavioral ecologists in exploring the consequences of resource characteristics for zooplankton aggregation behavior and movement decisions under conditions where the boundaries and characteristics (quantity and quality) of food patches can be standardized. The aggregation behavior of Daphnia magna and D. galeata x hyalina was tested in relation to i) the presence or absence of food or ii) food quality, where algae of high or low nutrient (phosphorus) content were offered in distinct patches. Individuals of both Daphnia species chose tubes containing food patches and D. galeata x hyalina also showed a preference towards food patches of high nutrient content. We discuss how the described equipment complements other behavioral approaches providing a useful tool to understand animal foraging decisions in environments with heterogeneous resource distributions.
    Dietary electrolyte balance affects the nutrient digestibility and maintenance energy expenditure of Nile tilapia
    Subramanian, S. ; Geurden, I. ; Orozco, Z.G.A. ; Kaushik, S.J. ; Verreth, J.A.J. ; Schrama, J.W. - \ 2013
    The British journal of nutrition 110 (2013). - ISSN 0007-1145 - p. 1948 - 1957.
    acid-base-balance - cation-anion difference - water rainbow-trout - juvenile african catfish - clarias-gariepinus burchell - fresh-water - alkaline tide - oreochromis-niloticus - gastrointestinal-tract - oncorhynchus-mykiss
    Acid–base disturbances caused by environmental factors and physiological events including feeding have been well documented in several fish species, but little is known about the impact of dietary electrolyte balance (dEB). In the present study, we investigated the effect of feeding diets differing in dEB ( - 100, 200, 500 or 800 mEq/kg diet) on the growth, nutrient digestibility and energy balance of Nile tilapia. After 5 weeks on the test diet, the growth of the fish was linearly affected by the dEB levels (P<0·001), with the lowest growth being observed in the fish fed the 800 dEB diet. The apparent digestibility coefficient (ADC) of fat was unaffected by dEB, whereas the ADC of DM and protein were curvilinearly related to the dEB levels, being lowest and highest in the 200 and 800 dEB diets, respectively. Stomach chyme pH at 3 h after feeding was linearly related to the dEB levels (P<0·05). At the same time, blood pH of the heart (P<0·05) and caudal vein (P<0·01) was curvilinearly related to the dEB levels, suggesting the influence of dEB on postprandial metabolic alkalosis. Consequently, maintenance energy expenditure (MEm) was curvilinearly related to the dEB levels (P<0·001), being 54 % higher in the 800 dEB group (88 kJ/kg0·8 per d) than in the 200 dEB group (57 kJ/kg0·8 per d). These results suggest that varying dEB levels in a diet have both positive and negative effects on fish. On the one hand, they improve nutrient digestibility; on the other hand, they challenge the acid–base homeostasis (pH) of fish, causing an increase in MEm, and thereby reduce the energy required for growth.
    Evaluation of Electrical Stunning of Atlantic Cod (Gadus morhua) and Turbot (Psetta maxima) in Seawater
    Lambooij, E. ; Digre, H. ; Erikson, U. ; Reimert, H.G.M. ; Burggraaf, D. ; Vis, J.W. van de - \ 2013
    Journal of Aquatic Food Product Technology 22 (2013)4. - ISSN 1049-8850 - p. 371 - 379.
    catfish clarias-gariepinus - fresh-water - slaughter - salmon - consciousness - behavior - quality - l.
    The aim of this study was to assess electrical stunning of Atlantic cod and turbot in seawater to develop a protocol for the process of stunning and killing. An induced general epileptiform insult (unconscious) had a duration of 40 ± 27 s (n =14) in cod (2.6 ± 0.5 kg) and 34 ± 18 s (n = 19) in turbot (520 ± 65 g). Seven cod and 3 turbot displayed a physical reaction, and 11 turbot registered an electroencephalogram (EEG) response to pain stimuli administered 30 s post-stun. The heart rate was 32 ± 6 beats/min in cod and 25 ± 7 beats/min in turbot prior to stunning. Post-stunning, the electrocardiogram (ECG) revealed fibrillation and reduced activity post-stun. EEG, ECG recordings, and behavioral observations indicate that when a bipolar square wave current was applied with a frequency of 133 Hz and 43% duty cycle side to side (turbot) and at 170 Hz and 33% duty cycle (cod) head to tail, both species were stunned in seawater at current densities of 3.2 A/dm2 and 2.5 A/dm2, respectively. For turbot, a 5 s exposure to electricity followed by chilling in ice water for 15 min is sufficient to prevent recovery. For cod, a killing method needs to be established.
    A comparative review of recovery processes in rivers, lakes, estuarine and coastal waters
    Verdonschot, P.F.M. ; Spears, B.M. ; Feld, C.K. ; Brucet, S. ; Keizer-Vlek, H.E. ; Borja, A. ; Elliot, M. ; Kernan, M. ; Johnson, R.K. - \ 2013
    Hydrobiologia 704 (2013)1. - ISSN 0018-8158 - p. 453 - 474.
    large woody debris - long-term - stream restoration - climate-change - fresh-water - fish communities - marine systems - dam removal - ecological relationships - anthropogenic pressures
    The European Water Framework Directive aims to improve ecological status within river basins. This requires knowledge of responses of aquatic assemblages to recovery processes that occur after measures have been taken to reduce major stressors. A systematic literature review comparatively assesses recovery measures across the four major water categories. The main drivers of degradation stem primarily from human population growth and increases in land use and water use changes. These drivers and pressures are the same in all four water categories: rivers, lakes, transitional and coastal waters. Few studies provide evidence of how ecological knowledge might enhance restoration success. Other major bottlenecks are the lack of data, effects mostly occur only in short-term and at local scale, the organism group(s) selected to assess recovery does not always provide the most appropriate response, the time lags of recovery are highly variable, and most restoration projects incorporate restoration of abiotic conditions and do not include abiotic extremes and biological processes. Restoration ecology is just emerging as a field in aquatic ecology and is a site, time and organism group-specific activity. It is therefore difficult to generalise. Despite the many studies only few provide evidence of how ecological knowledge might enhance restoration success.
    Nutrient Discharge from aquaculture operations in function of system design and production enviorment
    Verdegem, M.C.J. - \ 2013
    Reviews in Aquaculture 5 (2013)3. - ISSN 1753-5123 - p. 158 - 171.
    baltic sea consideration - recirculating aquaculture - fresh-water - coagulation/flocculation aids - antibiotic-resistance - biogeochemical cycles - constructed wetlands - marine ecosystems - reduction measure - farm effluent
    In aquaculture, nutrient loading is defined as the difference between nutrients supplied with fertilizers and feed and nutrients harvested in the form of finfish, crustaceans, molluscs and seaweeds. On average, the production of finfish and crustaceans results in a net nutrient loading, while for the production of molluscs and seaweeds the nutrient loading is negative. In marine and brackish water aquaculture, on a global scale, more nutrients are extracted than added to the environment. However, in freshwater, more nutrients are loaded than extracted. In 2008, the global aquaculture production of finfish and crustaceans resulted in an environmental loading of 1.7 million metric tonnes of nitrogen (N) and 0.46 million metric tonnes of phosphorus (P). This nitrogen loading represents 0.9% of the human input to the N-cycle and 0.4% of the global N-cycle. For phosphorus, the loading from finfish and crustacean aquaculture represents 2.3% of the global annual fertilizer supply. With cage aquaculture, nutrients are directly discharged to the environment. Mitigation measures should be shared equally between all polluters involved. For land-based aquaculture, the development of water re-use systems is still in its infancy. Although still a minor contributor to global aquaculture production, recirculation technology shows that control and mitigation of pollution from aquaculture is possible. A 15–20 year goal should be to have all inland aquaculture operations applying water re-use and purification technology and generating useful (waste) outputs in addition to standard aquaculture products
    Measuring sedimentation in tidal marshes: a review on methods and their applicability in biogeomorphological studies
    Nolte, S. ; Koppenaal, E.C. ; Esselink, P. ; Dijkema, K.S. ; Schuerch, M. ; Groot, A.V. de; Bakker, J.P. ; Temmerman, S. - \ 2013
    Journal of Coastal Conservation 17 (2013)3. - ISSN 1400-0350 - p. 301 - 325.
    sea-level rise - fallout pb-210 measurements - high-precision measurements - regenerative-dose protocol - rapidly subsiding wetland - barrier salt-marsh - san-francisco bay - fresh-water - ecosystem engineers - accumulation rates
    It is increasingly recognised that interactions between geomorphological and biotic processes control the functioning of many ecosystem types as described e.g. by the ecological theory of ecosystem engineering. Consequently, the need for specific bio-geomorphological research methods is growing recently. Much research on bio-geomorphological processes is done in coastal marshes. These areas provide clear examples of ecosystem engineering as well as other bio-geomorphological processes: Marsh vegetation slows down tidal currents and hence stimulates the process of sedimentation, while vice versa, the sedimentation controls ecological processes like vegetation succession. This review is meant to give insights in the various available methods to measure sedimentation, with special attention to their suitability to quantify bio-geomorphological interactions. The choice of method used to measure sedimentation is important to obtain the correct parameters to understand the biogeomorphology of tidal salt marshes. This review, therefore, aims to be a tool for decision making regarding the processes to be measured and the methods to be used. We, subdivide the methods into those measuring suspended sediment concentration (A), sediment deposition (B), accretion (C) and surface-elevation change (D). With this review, we would like to further encourage interdisciplinary studies in the fields of ecology and geomorphology.
    Estimating salinity stress in sugarcane fields with spaceborne hyperspectral vegetation indices
    Hamzeh, S. ; Naseri, A.A. ; Alavi Panah, S.K. ; Mojaradi, B. ; Bartholomeus, H. ; Clevers, J.G.P.W. ; Behzad, M. - \ 2013
    International Journal of applied Earth Observation and Geoinformation 21 (2013). - ISSN 0303-2434 - p. 282 - 290.
    salt-affected soils - difference water index - spectral reflectance - precision agriculture - chlorophyll content - canopy reflectance - plant-leaves - fresh-water - hyperion - leaf
    The presence of salt in the soil profile negatively affects the growth and development of vegetation. As a result, the spectral reflectance of vegetation canopies varies for different salinity levels. This research was conducted to (1) investigate the capability of satellite-based hyperspectral vegetation indices (VIs) for estimating soil salinity in agricultural fields, (2) evaluate the performance of 21 existing VIs and (3) develop new VIs based on a combination of wavelengths sensitive for multiple stresses and find the best one for estimating soil salinity. For this purpose a Hyperion image of September 2, 2010, and data on soil salinity at 108 locations in sugarcane (Saccharum officina L.) fields were used. Results show that soil salinity could well be estimated by some of these VIs. Indices related to chlorophyll absorption bands or based on a combination of chlorophyll and water absorption bands had the highest correlation with soil salinity. In contrast, indices that are only based on water absorption bands had low to medium correlations, while indices that use only visible bands did not perform well. From the investigated indices the optimized soil-adjusted vegetation index (OSAVI) had the strongest relationship (R2 = 0.69) with soil salinity for the training data, but it did not perform well in the validation phase. The validation procedure showed that the new salinity and water stress indices (SWSI) implemented in this study (SWSI-1, SWSI-2, SWSI-3) and the Vogelmann red edge index yielded the best results for estimating soil salinity for independent fields with root mean square errors of 1.14, 1.15, 1.17 and 1.15 dS/m, respectively. Our results show that soil salinity could be estimated by satellite-based hyperspectral VIs, but validation of obtained models for independent data is essential for selecting the best model.
    The good, the bad and the plenty: interactive effects of food quality and quantity on the growth of different Daphnia species
    Bukovinszky, T. ; Verschoor, A.M. ; Helmsing, N.R. ; Bezemer, T.M. ; Bakker, E.S. ; Vos, M. ; Domis, L.N.D. - \ 2012
    PLoS ONE 7 (2012)9. - ISSN 1932-6203 - 8 p.
    life-history - fresh-water - aquatic herbivores - body size - stoichiometry - zooplankton - limitation - performance - diets - cladocerans
    Effects of food quality and quantity on consumers are neither independent nor interchangeable. Although consumer growth and reproduction show strong variation in relation to both food quality and quantity, the effects of food quality or food quantity have usually been studied in isolation. In two experiments, we studied the growth and reproduction in three filter-feeding freshwater zooplankton species, i.e. Daphnia galeata x hyalina, D. pulicaria and D. magna, on their algal food (Scenedesmus obliquus), varying in carbon to phosphorus (C:P) ratios and quantities (concentrations). In the first experiment, we found a strong positive effect of the phosphorus content of food on growth of Daphnia, both in their early and late juvenile development. Variation in the relationship between the P-content of animals and their growth rate reflected interspecific differences in nutrient requirements. Although growth rates typically decreased as development neared maturation, this did not affect these species-specific couplings between growth rate and Daphnia P-content. In the second experiment, we examined the effects of food quality on Daphnia growth at different levels of food quantity. With the same decrease in P-content of food, species with higher estimated P-content at zero growth showed a larger increase in threshold food concentrations (i.e. food concentration sufficient to meet metabolic requirements but not growth). These results suggest that physiological processes such as maintenance and growth may in combination explain effects of food quality and quantity on consumers. Our study shows that differences in response to variation in food quality and quantity exist between species. As a consequence, species-specific effects of food quality on consumer growth will also determine how species deal with varying food levels, which has implications for resource-consumer interactions
    First report of (homo)anatoxin-a and dog neurotoxicosis after ingestion of benthic cyanobacteria in The Netherlands
    Faassen, E.J. ; Harkema, H. ; Begemann, L.L.J. ; Lürling, M.F.L.L.W. - \ 2012
    Toxicon 60 (2012)3. - ISSN 0041-0101 - p. 378 - 384.
    zwemwater - cyanobacteriën - toxinen - waterverontreiniging - oppervlaktewater - ijsselmeer - nederland - swimming water - cyanobacteria - toxins - water pollution - surface water - lake ijssel - netherlands - blue-green-algae - fresh-water - anatoxin-a - mass-spectrometry - homoanatoxin-a - identification - cylindrospermopsin - biosynthesis - microcystin
    In April and May 2011, three dogs died and one dog became ill after swimming in Lake IJmeer (The Netherlands). At the time, the lake was infested with the benthic cyanobacterial species Phormidium. A Eurasian Coot (Fulica atra) and a Black-headed Gull (Chroicocephalus ridibundus) also died near Lake IJmeer in the same period. One of the dogs and both birds were subjected to a pathological investigation. Furthermore, the Phormidium mat; algal samples from the dikes; contents of the animals' digestive systems and organ tissues were analysed for the following cyanobacterial toxins: (homo)anatoxin-a; (7-deoxy-)cylindrospermopsin; saxitoxins and gonyautoxins by LC-MS/MS. Samples were also analysed for the nontoxic (homo)anatoxin-a metabolites dihydro(homo)anatoxin-a and epoxy( homo) anatoxin-a. The dog necropsy results indicated neurotoxicosis and its stomach contained Phormidium filaments. Anatoxin-a was detected in the Phormidium mat (272 mu g g(-1) dry weight, stdev 65, n = 3) and in the dog's stomach contents (9.5 mu g g(-1) dry weight, stdev 2.4, n = 3). Both samples also contained the anatoxin-a metabolite dihydroanatoxin-a, and a trace of homoanatoxin-a was detected in the Phormidium mat. The birds were in bad nutritive condition at the time of necropsy and their stomachs and intestines did not contain any cyanobacterial material. Furthermore, no cyanobacterial toxins were detected in their stomachs, intestines and organs and they both had lesions that are not associated with cyanobacterial intoxication. This is the first report of anatoxin-a and homoanatoxina occurrence in The Netherlands, these toxins have likely caused the deaths of three dogs. The birds probably died of other causes. Dutch recreational waters are at this moment only screened for pelagic cyanobacterial species, the current bathing water protocol therefore does not protect humans and animals from negative effects of blooms of benthic cyanobacteria.
    Seasonal variation in mineralization rates (C-N-P-Si) of mussel Mytilus edulis biodeposits
    Jansen, H.M. ; Verdegem, M.C.J. ; Smaal, A.C. - \ 2012
    Marine Biology 159 (2012)7. - ISSN 0025-3162 - p. 1567 - 1580.
    la-madeleine quebec - sediment-water interface - biogeochemical fluxes - temperature-dependence - benthic respiration - nutrient fluxes - fresh-water - new-zealand - decomposition - culture
    To determine seasonal variability in mineralization dynamics of mussel biodeposits, we applied a multiple-element approach measuring mineralization rates of carbon (C), nitrogen (N), phosphorus (P) and silicate (Si) during three periods (March, August and November). The results of this study showed that mineralization rates vary between seasons and between elements and that mineralization dynamics were influenced by both temperature and biodeposit nutrient composition. Mineralization rates were 3.2 ± 0.4 mmol C, 0.17 ± 0.04 mmol N, 0.06 ± 0.02 mmol P and 3.91 ± 3.75 mmol Si per gram biodeposit (DW) per day, which represented 24 % of the particulate organic C and 17 % of the particulate organic N in mussel biodeposits. Seasonal variability was largest for Si mineralization with 60–80-fold higher rates measured in March compared to August and November. This difference is most likely related to the difference in biodeposit nutrient composition. It was furthermore shown that the labile fraction of biodeposits became mineralized after, respectively, 18, 9 and 13 days during the experimental periods in March, August and November. This indicates that temperature enhances biodeposit decomposition with approximately 2–3 times faster turnover at a 10 °C temperature interval (Q10).
    Use of chemicals and biological products in Asian aquacultire and their potential environmental risks: a critical review
    Rico, A. ; Satapornvanit, K. ; Haque, M.M. ; Min, J. ; Nguyen, P.T. ; Telfer, T. ; Brink, P.J. van den - \ 2012
    Reviews in Aquaculture 4 (2012)2. - ISSN 1753-5123 - p. 75 - 93.
    species sensitivity distributions - fresh-water - macrobrachium-rosenbergii - veterinary antibiotics - aquatic environment - malachite green - mangrove areas - shrimp ponds - toxicity - fish
    Over the past few decades, Asian aquaculture production has intensified rapidly through the adoption of technological advances, and the use of a wide array of chemical and biological products to control sediment and water quality and to treat and prevent disease outbreaks. The use of chemicals in aquaculture farms has raised environmental concerns owing to their potential impacts on downstream aquatic ecosystems. Currently little is known about the environmental fate and effects of the chemicals used in Asian aquaculture. Consequently, we reviewed recent information on the use of chemical and biological products in the most important Asian aquaculture producing countries and briefly summarize their main potential environmental impacts. We provide an overview of the main factors controlling the use of these chemicals and describe the international risk assessment guidelines available for aquaculture chemicals. Finally, data gaps and research needs for their implementation in Asian countries are discussed. Our review aims to form a basis for developing environmental risk assessment studies of the chemicals used in Asian aquaculture.
    Assessing effectiveness of electrical stunning and chillingin ice water of farmed yellowtail kingfish, common sole and pike-perch
    Llonch, P. ; Lambooij, E. ; Reimert, H.G.M. ; Vis, J.W. van de - \ 2012
    Aquaculture 364-365 (2012). - ISSN 0044-8486 - p. 143 - 149.
    catfish clarias-gariepinus - atlantic cod - fresh-water - fish - temperature - quality - stress - brain - l.
    Animals should be rendered unconscious before slaughter in order to avoid suffering or pain. The objective of this study was to evaluate an electrical stunning after dewatering to induce instantaneous unconsciousness and insensibility in yellowtail kingfish (Seriola lalandi), common sole (Solea solea) and pike-perch (Stizostedion lucioperca). To kill without recovery, the current was applied for 5 s, followed by chilling in ice water for 10 min. Loss of consciousness and sensibility were assessed by neural (EEG), physiological (ECG) and behavioural parameters. An epileptiform insult was observed in all yellowtail kingfish (n = 27), common sole (n = 25) and pike-perch (n = 25) after administering a current of 0.54 +/- 0.12 A(rms) (124 V dc and 11 V-rms ac; 100 Hz), 0.65 +/- 0.23 A(rms) (98 V dc and 8.4 V-rms ac; 100 Hz) and 0.75 +/- 0.24 A(rms) (144 V dc and 13 V-rms ac; 100 Hz) during 1 s through the head of individual fish, respectively. When yellowtail kingfish (n = 11) was submitted to a 5 s electrical stun followed by chilling in ice water, this resulted in passing 0.72 +/- 0.13 A(rms) for 5 s and no recovery during chilling. In the case of common sole (n = 10) and pike-perch (n = 12), passing 1.4 +/- 0.64 and 0.75 +/- 0.24 A(rms) during 5 s followed by chilling in ice water for 10 min resulted in an irrecoverable stun in 9 out 10 fish and 11 out 12 fish, respectively. We conclude that for yellowtail kingfish the investigated combination of electrical stunning and chilling is suitable for humane slaughter, whereas for common sole and pike-perch this procedure needs to be optimised. (C) 2012 Elsevier B.V. All rights reserved.
    Climate change impacts on the leaching of a heavy metal contimination in a small lowland catchment
    Visser, A. ; Kroes, J.G. ; Vliet, M.T.H. van; Blenkinsop, S. ; Fowler, H.J. ; Broers, H.P. - \ 2012
    Journal of Contaminant Hydrology 127 (2012)1-4. - ISSN 0169-7722 - p. 47 - 64.
    surface-water contamination - regional climate - soil-moisture - model data - groundwater recharge - nitrogen deposition - multimodel ensemble - hydrological model - river flows - fresh-water
    The Keersop catchment (43 km2) in the south of The Netherlands has been contaminated by the emissions of four zinc ore smelters. The objective of this study was to assess the effects of future projected climate change on the hydrology and the leaching of heavy metals (i.e. Cd and Zn) in the catchment. The numerical, quasi-2D, unsaturated zone Soil Water Atmosphere Plant model was used with 100-year simulated daily time series of precipitation and potential evapotranspiration. The time series are representative of stationary climates for the periods 1961–1990 (“baseline”) and 2071–2100 (“future”). The time series of future climate were obtained by downscaling the results of eight regional climate model (RCM) experiments, driven by the SRES A2 emissions scenario, using change factors for a series of climate statistics and applying them to stochastic weather generator models. The time series are characterized by increased precipitation in winter, less precipitation in summer, and higher air temperatures (between 2 °C and 5 °C) throughout the year. Future climate scenarios project higher evapotranspiration rates, more irrigation, less drainage, lower discharge rates and lower groundwater levels, due to increased evapotranspiration and a slowing down of the groundwater system. As a result, lower concentrations of Cd and Zn in surface water are projected. The reduced leaching of heavy metals, due to drying of the catchment, showed a positive impact on a limited aspect of surface water quality. --------------------------------------------------------------------------------
    Global Water Availability and Requirements for Future Food Production
    Gerten, D. ; Heinke, J. ; Hoff, H. ; Biemans, H. ; Fader, M. ; Waha, K. - \ 2011
    Journal of Hydrometeorology 12 (2011)5. - ISSN 1525-755X - p. 885 - 899.
    high-resolution - climate-change - fresh-water - resources - agriculture - vegetation - scenarios - nations - balance - trade
    This study compares, spatially explicitly and at global scale, per capita water availability and water requirements for food production presently (1971-2000) and in the future given climate and population change (2070-99). A vegetation and hydrology model Lund-Potsdam-Jena managed Land (LPJmL) was used to calculate green and blue water availability per capita, water requirements to produce a balanced diet representing a benchmark for hunger alleviation [3000 kilocalories per capita per day (1 kilocalorie = 4184 joules), here assumed to consist of 80% vegetal food and 20% animal products], and a new water scarcity indicator that relates the two at country scale. A country was considered water-scarce if its water availability fell below the water requirement for the specified diet, which is presently the case especially in North and East Africa and in southwestern Asia. Under climate (derived from 17 general circulation models) and population change (A2 and B1 emissions and population scenarios), water availability per person will most probably diminish in many regions. At the same time the calorie-specific water requirements tend to decrease, due mainly to the positive effect of rising atmospheric CO(2) concentration on crop water productivity which, however, is very uncertain to be fully realized in most regions. As a net effect of climate, CO(2), and population change, water scarcity will become aggravated in many countries, and a number of additional countries are at risk of losing their present capacity to produce a balanced diet for their inhabitants.
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