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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    Guidance for the Prognostic Risk Assessment of Nanomaterials in Aquatic Ecosystems
    Koelmans, A.A. ; Diepens, N.J. ; Velzeboer, I. ; Besseling, E. ; Quik, J.T.K. - \ 2015
    Science of the Total Environment 535 (2015). - ISSN 0048-9697 - p. 141 - 149.
    engineered nanomaterials - tio2 nanoparticles - environmental fate - carbon nanotubes - manufactured nanoparticles - hediste-diversicolor - silver nanoparticles - scrobicularia-plana - cuo nanoparticles - fresh-water
    Our understanding of the environmental fate and effects of engineered nanomaterials (ENMs) is in a state of fast transition. Recent scientific developments open new and powerful perspectives to define a framework for the prognostic risk assessment of ENMs in aquatic ecosystems. This requires abandoning the reductionist's approach of mechanistic analysis on particle or cellular scales and calls for engineering solutions that deal with uncertainties by applying assessment factors and probabilistic approaches. An ecological risk assessment (ERA) framework for ENMs is similar to that for other classes of substances, in that it requires clear protection goals based on ecosystem services, evidence-based concepts that link exposure to effects, and a transparent tiered effect assessment. Here, we discuss approaches to assess exposure and effects of ENMs. This includes recent developments in ENP fate modeling that greatly expanded the potential of prognostic exposure assessments. For the effect assessment, we advise a cost-effective screening based on principles of read-across as a conservative first tier. The feasibility of using species sensitivity distributions as a higher tier option is discussed. Controlled model ecosystem field experiments are proposed as a highest experimental tier, and are required for the calibration of the lower tiers. An outlook to unify information from various tiers by experimental work, fate modeling, and effect modeling as cost-effective prognostic tools for the ERA of ENMs is provided.
    Comparison of endogenous loss and maintenance need for minerals in rainbow trout (Oncorhynchus mykiss) fed fishmeal or plant ingredient-based diets
    Antony Jesu Prabhu, P. ; Kaushik, S.J. ; Mariojouls, C. ; Surget, A. ; Fontagné-Dicharry, S. ; Schrama, J.W. ; Geurden, I. - \ 2015
    Fish Physiology and Biochemistry 41 (2015)1. - ISSN 0920-1742 - p. 243 - 253.
    salmon salmo-salar - true phosphorus digestibility - fingerling channel catfish - biliary copper excretion - juvenile chinook salmon - phytate soybean meals - atlantic salmon - magnesium requirement - potassium requirement - fresh-water
    Mineral needs as affected by changes in dietary protein and oil sources were studied in rainbow trout. Duplicate groups (n = 30 fish per replicate) of rainbow trout (initial BW: 37 g) were fed either a fish meal/fish oil-based (M) or a complete plant ingredient (V)-based diet at four graded ration (R) levels [apparent satiation (AS), R75, R50 and R25 % of AS]; one treatment group was maintained under starvation. The feeding trial lasted 12 weeks at a water temperature of 17 °C. Dietary intake, apparent digestibility and initial and final whole-body composition data were used to calculate mineral gain which was regressed against digestible mineral intake (both expressed as mg or µg kg-0.8 day-1). Starvation loss (SL), endogenous loss of fed fish (ELF, y-intercept at x = 0) and point of intake for zero balance (PZB, x-intercept at y = 0) were used as estimates of maintenance requirements. SL provided the lowest estimate, ELF provided the net requirement of a mineral for maintenance and PZB provided the digestible dietary intake required to meet maintenance (SL
    Managing the effects of multiple stressors on aquatic ecosystems under water scarcity
    Navarro-Ortega, A. ; Acuña, V. ; Bellin, A. ; Burek, P. ; Cassiani, G. ; Choukr-Allah, R. ; Dolédec, S. ; Elosegi, A. ; Ferrari, F. ; Ginebreda, A. ; Grathwohl, P. ; Jones, C. ; Ker Rault, P.A. ; Kok, K. ; Koundouri, P. ; Ludwig, R.P. ; Merz, R. ; Milacic, R. - \ 2015
    Science of the Total Environment 503-504 (2015). - ISSN 0048-9697 - p. 3 - 9.
    climate-change - fresh-water - mediterranean rivers - southern europe - management - scenarios - quality - systems
    Water scarcity is a serious environmental problem in many European regions, and will likely increase in the near future as a consequence of increased abstraction and climate change. Water scarcity exacerbates the effects of multiple stressors, and thus results in decreased water quality. It impacts river ecosystems, threatens the services they provide, and it will force managers and policy-makers to change their current practices. The EU-FP7 project GLOBAQUA aims at identifying the prevalence, interaction and linkages between stressors, and to assess their effects on the chemical and ecological status of freshwater ecosystems in order to improve water management practice and policies. GLOBAQUA assembles a multidisciplinary team of 21 European plus 2 non-European scientific institutions, as well as water authorities and river basin managers. The project includes experts in hydrology, chemistry, biology, geomorphology, modelling, socio-economics, governance science, knowledge brokerage, and policy advocacy. GLOBAQUA studies six river basins (Ebro, Adige, Sava, Evrotas, Anglian and Souss Massa) affected by water scarcity, and aims to answer the following questions: how does water scarcity interact with other existing stressors in the study river basins? How will these interactions change according to the different scenarios of future global change? Which will be the foreseeable consequences for river ecosystems? How will these in turn affect the services the ecosystems provide? How should management and policies be adapted to minimise the ecological, economic and societal consequences? These questions will be approached by combining data-mining, field- and laboratory-based research, and modelling. Here, we outline the general structure of the project and the activities to be conducted within the fourteen work-packages of GLOBAQUA.
    The impact of elevated water nitrite concentration on physiology, growth and feed intake of African catfish Clarias gariepinus (Burchell 1822)
    Roques, J.A.C. ; Schram, E. ; Spanings, T. ; Schaik, T. van; Abbink, W. ; Boerrigter, J. ; Vries, P. de; Vis, J.W. van de; Flik, G. - \ 2015
    Aquaculture Research 46 (2015)6. - ISSN 1355-557X - p. 1384 - 1395.
    channel catfish - rainbow-trout - fresh-water - ictalurus-punctatus - oncorhynchus-mykiss - na+/k+-atpase - carpio l. - toxicity - chloride - mechanism
    The nitrite threshold concentration in rearing water of African catfish (Clarias gariepinus) was assessed. African catfish with an initial mean (SD) weight of 219.7 (57.8) g were exposed to an increasing range of water nitrite from 6 (Control) to 928 µM nitrite for 28 days. Mean (SD) plasma nitrite concentrations increased from 5.0 (3.6) to 32.5 (12.6) µM at 928 µM ambient nitrite. The increase in nitrite was accompanied by gradual increase in plasma nitrate from 41.6 (28.4) µM to 420.2 (106.4) µM. Haematocrit, haemoglobin, methemoglobin, plasma concentrations of cortisol, glucose, lactate, osmolality, gill morphology and branchial Na+/K+-ATPase activity were not affected. Feed intake, final weight, SGR, FCR and mortality were not affected. We advise not to exceed a water nitrite concentration of 43 µM (0.6 mg L-1 NO2--N) to prevent the risk of reduced growth and feed intake in African catfish aquaculture.
    Water quality status and trends in agriculture-dominated headwaters; a national monitoring network for assessing the effectiveness of national and European manure legislation in The Netherlands
    Rozemeijer, J.C. ; Klein, J. ; Broers, H.P. ; Tol-Leenders, T.P. van; Grift, B. van der - \ 2014
    Environmental Monitoring and Assessment 186 (2014)12. - ISSN 0167-6369 - p. 8981 - 8995.
    flow route contributions - long-term change - surface-water - nutrient concentrations - temporal variability - groundwater quality - catchment discharge - fresh-water - land-use - phosphorus
    Large nutrient losses to groundwater and surface waters are a major drawback of the highly productive agricultural sector in The Netherlands. The resulting high nutrient concentrations in water resources threaten their ecological, industrial, and recreational functions. To mitigate eutrophication problems, legislation on nutrient application in agriculture was enforced in 1986 in The Netherlands. The objective of this study was to evaluate this manure policy by assessing the water quality status and trends in agriculture-dominated headwaters. We used datasets from 5 agricultural test catchments and from 167 existing monitoring locations in agricultural headwaters. Trend analysis for these locations showed a fast reduction of nutrient concentrations after the enforcement of the manure legislation (median slopes of -0.55 mg/l per decade for total nitrogen (N-tot) and -0.020 mg/l per decade for total phosphorus (P-tot)). Still, up to 76 % of the selected locations currently do not comply with either the environmental quality standards (EQSs) for nitrogen (N-tot) or phosphorus (P-tot). This indicates that further improvement of agricultural water quality is needed. We observed that weather-related variations in nutrient concentrations strongly influence the compliance testing results, both for individual locations and for the aggregated results at the national scale. Another important finding is that testing compliance for nutrients based on summer average concentrations may underestimate the agricultural impact on ecosystem health. The focus on summer concentrations does not account for the environmental impact of high winter loads from agricultural headwaters towards downstream water bodies.
    Iron oxidation kinetics and phosphate immobilization along the flow-path from groundwater into surface water
    Grift, B. van der; Rozemeijer, J.C. ; Griffioen, J. ; Velde, Y. van der - \ 2014
    Hydrology and Earth System Sciences 18 (2014)11. - ISSN 1027-5606 - p. 4687 - 4702.
    suspended sediment - ferrous iron - fresh-water - phosphorus limitation - nutrient dynamics - fe(ii) oxidation - arsenic removal - natural-waters - riparian zone - river
    The retention of phosphorus in surface waters through co-precipitation of phosphate with Fe-oxyhydroxides during exfiltration of anaerobic Fe(II) rich groundwater is not well understood. We developed an experimental field set-up to study Fe(II) oxidation and P immobilization along the flow-path from groundwater into surface water in an agricultural experimental catchment of a small lowland river. We physically separated tube drain effluent from groundwater discharge before it entered a ditch in an agricultural field. Through continuous discharge measurements and weekly water quality sampling of groundwater, tube drain water, exfiltrated groundwater, and surface water, we investigated Fe(II) oxidation kinetics and P immobilization processes. The oxidation rate inferred from our field measurements closely agreed with the general rate law for abiotic oxidation of Fe(II) by O-2. Seasonal changes in climatic conditions affected the Fe(II) oxidation process. Lower pH and lower temperatures in winter (compared to summer) resulted in low Fe oxidation rates. After exfiltration to the surface water, it took a couple of days to more than a week before complete oxidation of Fe(II) is reached. In summer time, Fe oxidation rates were much higher. The Fe concentrations in the exfiltrated groundwater were low, indicating that dissolved Fe(II) is completely oxidized prior to inflow into a ditch. While the Fe oxidation rates reduce drastically from summer to winter, P concentrations remained high in the groundwater and an order of magnitude lower in the surface water throughout the year. This study shows very fast immobilization of dissolved P during the initial stage of the Fe(II) oxidation process which results in P-depleted water before Fe(II) is completely depleted. This cannot be explained by surface complexation of phosphate to freshly formed Fe-oxyhydroxides but indicates the formation of Fe(III)-phosphate precipitates. The formation of Fe(III)-phosphates at redox gradients seems an important geochemical mechanism in the transformation of dissolved phosphate to structural phosphate and, therefore, a major control on the P retention in natural waters that drain anaerobic aquifers.
    Humic substances interfere with phosphate removal by lanthanum modified clay in controlling eutrophication
    Lurling, M.F.L.L.W. ; Waaijenberg, G.W.A.M. ; Oosterhout, J.F.X. - \ 2014
    Water Research 54 (2014). - ISSN 0043-1354 - p. 78 - 88.
    waterbodems - fosfaten - eutrofiëring - bioremediëring - laboratoriumproeven - water bottoms - phosphates - eutrophication - bioremediation - laboratory tests - rare-earth-elements - phosphorus-binding clay - organic-matter removal - modified bentonite clay - natural-waters - cyanobacterial toxins - polyaluminum chloride - cation binding - ion-binding - fresh-water
    The lanthanum (La) modified bentonite Phoslock® has been proposed as dephosphatisation technique aiming at removing Filterable Reactive Phosphorus (FRP) from the water and blocking the release of FRP from the sediment. In the modified clay La is expected the active ingredient. We conducted controlled laboratory experiments to measure the FRP removal by Phoslock® in the presence and absence of humic substances, as La complexation with humic substances might lower the effectiveness of La (Phoslock®) to bind FRP. The results of our study support the hypothesis that the presence of humic substances can interfere with the FRP removal by the La-modified bentonite. Both a short-term (1 d) and long-term (42 d) experiment were in agreement with predictions derived from chemical equilibrium modelling and showed lower FRP removal in presence of humic substances. This implies that in DOC-rich inland waters the applicability of exclusively Phoslock® as FRP binder should be met critically. In addition, we observed a strong increase of filterable La in presence of humic substances reaching in a week more than 270 µg La l-1 that would infer a violation of the Dutch La standard for surface water, which is 10.1 µg La l-1. Hence, humic substances are an important factor that should be given attention when considering chemical FRP inactivation as they might play a substantial role in lowering the efficacy of metal-based FRP-sorbents, which makes measurements of humic substances (DOC) as well as controlled experiments vital.
    Effect of Selected Plant Extracts and D- and L-Lysine on the Cyanobacterium Microcystis aeruginosa
    Lurling, M.F.L.L.W. ; Oosterhout, J.F.X. - \ 2014
    Water 6 (2014)6. - ISSN 2073-4441 - p. 1807 - 1825.
    moringa-oleifera seeds - controlling eutrophication - fresh-water - amino-acid - blooms - coagulation - inhibition - mechanism - substances - phosphorus
    We tested extracts from Fructus mume, Salvia miltiorrhiza and Moringa oleifera as well as L-lysine and D-Lysine as curative measures to rapidly suppress the cyanobacterium Microcystis aeruginosa NIVA-CYA 43. We tested these compounds under similar conditions to facilitate comparisons. We hypothesized that for each compound, relatively low concentrations—i.e., 5–50 mg L-1, would reduce M. aeruginosa biomass. At these low concentrations, only L-lysine caused a decline in M. aeruginosa biomass at =4.3 mg L-1. F. mume extract was effective to do so at high concentrations, i.e., at =240 mg L-1, but the others were virtually non-effective. Low pH caused by organic acids is a probable explanation for the effect of F. mume extract. No complete wipe-outs of the experimental population were achieved as Photosystem II efficiency showed a recovery after six days. L-lysine may be effective at low concentrations—meaning low material costs. However, the effect of L-lysine seems relatively short-lived. Overall, the results of our study did not support the use of the tested plant extracts and amino-acid as promising candidates for curative application in M. aeruginosa bloom control.
    Beating the blues: Is there any music in fighting cyanobacteria with ultrasound?
    Lurling, M.F.L.L.W. ; Tolman, Y. - \ 2014
    Water Research 66 (2014). - ISSN 0043-1354 - p. 361 - 373.
    oppervlaktewater - cyanobacteriën - ultrageluid - waterkwaliteit - surface water - cyanobacteria - ultrasound - water quality - anabaena-flos-aquae - microcystis-aeruginosa - effective microorganisms - harmful cyanobacteria - growth-inhibition - climate-change - bloom control - gas vesicles - fresh-water - eutrophication
    The hypothesis that cyanobacteria can be controlled by commercially available ultrasound transducers was tested in laboratory experiments with cultures of the cyanobacteria Anabaena sp., Cylindrospermopsis raciborskii and Microcystis aeruginosa and the green alga Scenedesmus obliquus that were grown in the absence or presence of ultrasound (mix of 20, 28 and 44 kHz). The Scenedesmus experiment also included a treatment with the zooplankton grazer Daphnia magna. Chlorophyll-a and biovolume-based growth of Anabaena was significantly lower in ultrasound exposed cultures than in controls. Particle based growth rates were higher in ultrasound treatments. Filaments were significantly shorter in ultrasound exposed cultures reflecting filament breakage. Photosystem II efficiency was not affected by ultrasound. In Cylindrospermopsis chlorophyll-a based growth rates and photosystem II efficiencies were similar in controls and ultrasound treatments, but biovolume-based growth was significantly lower in ultrasound exposed cultures compared to controls. Despite biovolume growth rates of the filamentous cyanobacteria were reduced in ultrasound treatments compared to controls, growth remained positive implying still a population increase. In Microcystis and Scenedesmus growth rates were similar in controls and ultrasound treatments. Hence, no effect of ultrasound on these phytoplankton species was found. Ultrasound should not be viewed "environmental friendly" as it killed all Daphnia within 15 min, releasing Scenedesmus from grazing control in the cultures. Based on our experiments and critical literature review, we conclude that there is no music in controlling cyanobacteria in situ with the commercially available ultrasound transducers we have tested.
    Effects of commercially available ultrasound on the zooplankton grazer Daphnia and consequent water greening in laboratory experiments
    Lürling, M.F.L.L.W. ; Tolman, Y. - \ 2014
    Water 6 (2014)11. - ISSN 2073-4441 - p. 3247 - 3263.
    algal bloom control - microcystis-aeruginosa - cyanobacterial toxins - fresh-water - eutrophication - phytoplankton - frequencies - ecosystems - marine
    We tested the hypothesis that ultrasound in controlling cyanobacteria and algal blooms is “environmental friendly” by exposing the non-target zooplankton grazer Daphnia magna to ultrasound produced by commercially available ultrasound transducers. In populations of 15 Daphnia (~2 mm body size) exposed in 800 mL of water to ultrasound supplied at 20 kHz, 28 kHz, 36 kHz or 44 kHz, all animals were killed between 10 min (44 kHz) and 135 min (20 kHz). Differently sized Daphnia (0.7–3.2 mm) were all killed between 4 and 30 min when exposed to 44 kHz. Increasing water volumes up to 3.2 L and thus lowering the ultrasound intensity did not markedly increase survival of Daphnia exposed to 44 kHz ultrasound. A tank experiment with six 85 L tanks containing a mixture of green algae, cyanobacteria and D. magna was performed to study the effect of ultrasound over a longer time period (25 d). In controls, when Daphnia flourished, algal biomass dropped and the water became clear. In contrast, in ultrasound treatments, Daphnia abundance was extremely low releasing phytoplankton from grazing control, which resulted in high phytoplankton biomass. Hence, we conclude that ultrasound from commercially available transducers sold to clear ponds, aquaria and small reservoirs, should not be considered environmentally friendly and cannot be viewed as efficient in controlling phytoplankton.
    Alternative stable states in large shallow lakes?
    Janssen, A.B.G. ; Teurlincx, S. ; An, S.Q. ; Janse, J.H. ; Paerl, H. ; Mooij, W.M. - \ 2014
    Journal of Great Lakes Research 40 (2014)4. - ISSN 0380-1330 - p. 813 - 826.
    catastrophic regime shifts - ecosystem model pclake - drinking-water source - detroit river system - taihu lake - fresh-water - aquatic vegetation - spatiotemporal patterns - macrophyte communities - spatial heterogeneity
    Many lakes worldwide are experiencing great change due to eutrophication. Consequently, species composition changes, toxic algal blooms proliferate, and drinking water supplies dwindle. The transition to the deteriorated state can be catastrophic with an abrupt change from macrophyte to phytoplankton domination. This has been shown repeatedly in small lakes. Whether such alternative stable states also exist in large shallow lakes is less clear, however. Here we discuss the characteristics that give rise to alternative stable states in large shallow lakes either in the lake as whole or restricted to specific regions of the lake. We include the effect of lake size, spatial heterogeneity and internal connectivity on a lake's response along the eutrophication axis. As a case study, we outline the eutrophication history of Lake Taihu (China) and illustrate how lake size, spatial heterogeneity and internal connectivity can explain the observed spatial presence of different states. We discuss whether these states can be alternatively stable by comparing the data with model output (PCLake). These findings are generalised for other large, shallow lakes. We conclude that locations with prevailing size effects generally lack macrophytes; and, therefore, alternative stable states are unlikely to occur there. However, most large shallow lakes have macrophytes whose presence remains unexplained when only size effect is taken into account. By including spatial heterogeneity in the analysis, the presence of macrophytes and alternative stable states in large shallow lakes is better understood. Finally, internal connectivity is important because a high internal connectivity reduces the stability of alternative states.
    Effects of hydrogen peroxide and ultrasound on biomass reduction and toxin release in the cyanobacterium, microcystis aeruginosa
    Lurling, M.F.L.L.W. ; Meng, D. ; Faassen, E.J. - \ 2014
    Toxins 6 (2014)12. - ISSN 2072-6651 - p. 3260 - 3280.
    waste stabilization ponds - water-treatment processes - blue-green-algae - fresh-water - human health - harmful cyanobacteria - liquid-chromatography - phosphatase bioassay - membrane integrity - mass spectrometry
    Cyanobacterial blooms are expected to increase, and the toxins they produce threaten human health and impair ecosystem services. The reduction of the nutrient load of surface waters is the preferred way to prevent these blooms; however, this is not always feasible. Quick curative measures are therefore preferred in some cases. Two of these proposed measures, peroxide and ultrasound, were tested for their efficiency in reducing cyanobacterial biomass and potential release of cyanotoxins. Hereto, laboratory assays with a microcystin (MC)-producing cyanobacterium (Microcystis aeruginosa) were conducted. Peroxide effectively reduced M. aeruginosa biomass when dosed at 4 or 8 mg L-1, but not at 1 and 2 mg L-1. Peroxide dosed at 4 or 8 mg L-1 lowered total MC concentrations by 23%, yet led to a significant release of MCs into the water. Dissolved MC concentrations were nine-times (4 mg L-1) and 12-times (8 mg L-1 H2O2) higher than in the control. Cell lysis moreover increased the proportion of the dissolved hydrophobic variants, MC-LW and MC-LF (where L = Leucine, W = tryptophan, F = phenylalanine). Ultrasound treatment with commercial transducers sold for clearing ponds and lakes only caused minimal growth inhibition and some release of MCs into the water. Commercial ultrasound transducers are therefore ineffective at controlling cyanobacteria.
    Enhanced Input of Terrestrial Particulate Organic Matter Reduces the Resilience of the Clear-Water State of Shallow Lakes: A Model Study
    Lischke, B. ; Hilt, S. ; Janse, J.H. ; Kuiper, J.J. ; Mehner, T. ; Mooij, W.M. ; Gaedke, U. - \ 2014
    Ecosystems 17 (2014)4. - ISSN 1432-9840 - p. 616 - 626.
    climate-change - food webs - humic substances - resource use - fresh-water - loch ness - land-use - carbon - ecosystem - phosphorus
    The amount of terrestrial particulate organic matter (t-POM) entering lakes is predicted to increase as a result of climate change. This may especially alter the structure and functioning of ecosystems in small, shallow lakes which can rapidly shift from a clear-water, macrophyte-dominated into a turbid, phytoplankton-dominated state. We used the integrative ecosystem model PCLake to predict how rising t-POM inputs affect the resilience of the clear-water state. PCLake links a pelagic and benthic food chain with abiotic components by a number of direct and indirect effects. We focused on three pathways (zoobenthos, zooplankton, light availability) by which elevated t-POM inputs (with and without additional nutrients) may modify the critical nutrient loading thresholds at which a clear-water lake becomes turbid and vice versa. Our model results show that (1) increased zoobenthos biomass due to the enhanced food availability results in more benthivorous fish which reduce light availability due to bioturbation, (2) zooplankton biomass does not change, but suspended t-POM reduces the consumption of autochthonous particulate organic matter which increases the turbidity, and (3) the suspended t-POM reduces the light availability for submerged macrophytes. Therefore, light availability is the key process that is indirectly or directly changed by t-POM input. This strikingly resembles the deteriorating effect of terrestrial dissolved organic matter on the light climate of lakes. In all scenarios, the resilience of the clear-water state is reduced thus making the turbid state more likely at a given nutrient loading. Therefore, our study suggests that rising t-POM input can add to the effects of climate warming making reductions in nutrient loadings even more urgent.
    Resolving the polyphyletic nature of Pyricularia (Pyriculariaceae)
    Klaubauf, S. ; Tharreau, D. ; Fournier, E. ; Groenewald, J.Z. ; Crous, P.W. ; Vries, R.P. de; Lebrun, M.H. - \ 2014
    Studies in Mycology 79 (2014). - ISSN 0166-0616 - p. 85 - 120.
    rice blast fungus - magnaporthe-oryzae - juncus-roemerianus - molecular-data - fresh-water - grisea - phylogeny - genera - specificity - resistance
    Species of Pyricularia (magnaporthe-like sexual morphs) are responsible for major diseases on grasses. Pyricularia oryzae (sexual morph Magnaporthe oryzae) is responsible for the major disease of rice called rice blast disease, and foliar diseases of wheat and millet, while Pyricularia grisea (sexual morph Magnaporthe grisea) is responsible for foliar diseases of Digitaria. Magnaporthe salvinii, M. poae and M. rhizophila produce asexual spores that differ from those of Pyricularia sensu stricto that has pyriform, 2-septate conidia produced on conidiophores with sympodial proliferation. Magnaporthe salvinii was recently allocated to Nakataea, while M. poae and M. rhizophila were placed in Magnaporthiopsis. To clarify the taxonomic relationships among species that are magnaporthe- or pyricularia-like in morphology, we analysed phylogenetic relationships among isolates representing a wide range of host plants by using partial DNA sequences of multiple genes such as LSU, ITS, RPB1, actin and calmodulin. Species of Pyricularia s. str. belong to a monophyletic clade that includes all P. oryzae/P. grisea isolates tested, defining the Pyriculariaceae, which is sister to the Ophioceraceae, representing two novel families. These clades are clearly distinct from species belonging to the Gaeumannomyces pro parte/Magnaporthiopsis/Nakataea generic complex that are monophyletic and define the Magnaporthaceae. A few magnaporthe- and pyricularia-like species are unrelated to Magnaporthaceae and Pyriculariaceae. Pyricularia oryzae/P. grisea isolates cluster into two related clades. Host plants such as Eleusine, Oryza, Setaria or Triticum were exclusively infected by isolates from P. oryzae, while some host plant such as Cenchrus, Echinochloa, Lolium, Pennisetum or Zingiber were infected by different Pyricularia species. This demonstrates that host range cannot be used as taxonomic criterion without extensive pathotyping. Our results also show that the typical pyriform, 2-septate conidium morphology of P. grisea/P. oryzae is restricted to Pyricularia and Neopyricularia, while most other genera have obclavate to more ellipsoid 2-septate conidia. Some related genera (Deightoniella, Macgarvieomyces) have evolved 1-septate conidia. Therefore, conidium morphology cannot be used as taxonomic criterion at generic level without phylogenetic data. We also identified 10 novel genera, and seven novel species. A re-evaluation of generic and species concepts within Pyriculariaceae is presented, and novelties are proposed based on morphological and phylogenetic data.
    Odonata of Curacao, southern Caribbean, with an update to the fauna of the ABC islands
    Paulson, D.R. ; Haseth, C. de; Debrot, A.O. - \ 2014
    The International Journal of Odonatology 17 (2014)4. - ISSN 1388-7890 - p. 237 - 249.
    fresh-water - west-indies - bonaire - libellulidae - anisoptera - orthemis - fishes - aruba
    A three-year field study (January 2011–December 2013) of the Odonata of Curaçao, supported by photos and exuvial collections, recorded a total of 21 species from the island, almost doubling its previously known fauna. The lists of Odonata known from Aruba and Bonaire were also updated by specimen and photo records, and 24 species are now known from these three islands. During the period of the study, odonates decreased in abundance and diversity in Curaçao, apparently because heavy rains just before the study began led to colonization of the island by several nonresident species that subsequently declined and disappeared as wetlands diminished during a period with normal rainfall
    The Global Invertebrate Genomics Alliance (GIGA). 2014. Developing Community Resources to Study Diverse Invertebrate Genomes
    Pomponi, S.A. - \ 2014
    Journal of Heredity 105 (2014)1. - ISSN 0022-1503 - p. 1 - 18.
    marine natural-products - gene-expression - draft genome - tetranychus-urticae - human microbiome - whole-genome - fresh-water - evolution - phylogeny - coral
    Over 95% of all metazoan (animal) species comprise the “invertebrates,” but very few genomes from these organisms have been sequenced. We have, therefore, formed a “Global Invertebrate Genomics Alliance” (GIGA). Our intent is to build a collaborative network of diverse scientists to tackle major challenges (e.g., species selection, sample collection and storage, sequence assembly, annotation, analytical tools) associated with genome/transcriptome sequencing across a large taxonomic spectrum. We aim to promote standards that will facilitate comparative approaches to invertebrate genomics and collaborations across the international scientific community. Candidate study taxa include species from Porifera, Ctenophora, Cnidaria, Placozoa, Mollusca, Arthropoda, Echinodermata, Annelida, Bryozoa, and Platyhelminthes, among others. GIGA will target 7000 noninsect/nonnematode species, with an emphasis on marine taxa because of the unrivaled phyletic diversity in the oceans. Priorities for selecting invertebrates for sequencing will include, but are not restricted to, their phylogenetic placement; relevance to organismal, ecological, and conservation research; and their importance to fisheries and human health. We highlight benefits of sequencing both whole genomes (DNA) and transcriptomes and also suggest policies for genomic-level data access and sharing based on transparency and inclusiveness.
    Post-prandial changes in plasma mineral levels in rainbow trout fed a complete plant ingredient based diet and the effect of supplemental di-calcium phosphate
    Antony Jesu Prabhu, P. ; Schrama, J.W. ; Mariojouls, C. ; Godin, S. ; Fontagné-Dicharry, S. ; Geurden, I. ; Surget, A. ; Bouyssiere, B. ; Kaushik, S.J. - \ 2014
    Aquaculture 430 (2014). - ISSN 0044-8486 - p. 34 - 43.
    salmon salmo-salar - fecal phosphorus excretion - european sea-bass - low fish-meal - oncorhynchus-mykiss - atlantic salmon - fresh-water - channel catfish - dicentrarchus-labrax - tricalcium phosphate
    Post-prandial changes in plasma mineral levels and utilisation of minerals in rainbow trout fed complete plant ingredient based diets with or without supplemental di-calcium phosphate (DCP) were studied over an 8 week period. Three diets were used: diet M was FM and fish oil (FO) based diet (control); diets VP0 and VP + (V diets) were completely based on plant derived protein and lipid sources. One of the V diets (VP +) was supplemented with DCP to supply 5 g kg- 1 dry matter available phosphorus (P); while the other diet (VP0) was not supplemented with DCP. Change in dietary protein source significantly affected the post-prandial pattern in plasma levels of P (p <0.05), Ca (p <0.007), Mg (p <0.001) and Zn (p <0.03). Area under the curve analysis indicated that compared to VP0, DCP supplementation in VP + improved plasma levels of P (p <0.01) and K (p <0.05); Cu (p <0.002), Se (p <0.009) and Zn (p <0.001) levels were reduced while Ca, Mg and Fe levels were unaffected (p > 0.05). Based on measurement of apparent digestibility, growth and whole body composition analyses, mineral balances were established showing that supplementation of DCP led to significant increase in whole body P concentration and P retention in VP +, comparable to fish fed diet M with significantly (p <0.05) reduced faecal and non-faecal P losses. There was improved post-absorptive retention (as % of available intake) of Ca (p <0.05), Mg (p <0.05) and K (p <0.05) in VP + compared to VP0. Utilisation of Cu (p <0.05) and Zn (p <0.01) was negatively affected. DCP supplementation to complete plant ingredient based diet increased the post-prandial plasma levels, whole body concentration and utilisation of macro-minerals (P, Ca, Mg and K) whereas that of micro-minerals especially Zn and Cu were negatively affected.
    Comparative effects of zinc oxide nanoparticles and dissolved zinc on zebrafish embryos and eleuthero-embryos: Importance of zinc ions
    Brun, N.R. ; Lenz, M. ; Wehrli, B. ; Fent, K. - \ 2014
    Science of the Total Environment 476-477 (2014). - ISSN 0048-9697 - p. 657 - 666.
    in-vitro evaluation - zno nanoparticles - oxidative stress - fresh-water - aggregation kinetics - silver nanoparticles - cell-line - bulk zno - toxicity - nanomaterials
    The increasing use of zinc oxide nanoparticles (nZnO) and their associated environmental occurrence make it necessary to assess their potential effects on aquatic organisms. Upon water contact, nZnO dissolve partially to zinc (Zn(II)). To date it is not yet completely understood, whether effects of nZnO are solely or partly due to dissolved Zn(II). Here we compare potential effects of 0.2, 1 and 5 mg/L nZnO and corresponding concentrations of released Zn(II) by water soluble ZnCl2 to two development stages of zebrafish, embryos and eleuthero-embryos, by analysing expressional changes by RT-qPCR. Another objective was to assess uptake and tissue distribution of Zn(II). Laser ablation-ICP-MS analysis demonstrated that uptake and tissue distribution of Zn(II) were identical for nZnO and ZnCl2 in eleuthero-embryos. Zn(II) was found particularly in the retina/pigment layer of eyes and brain. Both nZnO and dissolved Zn(II) derived from ZnCl2 had similar inhibiting effects on hatching, and they induced similar expressional changes of target genes. At 72 hours post fertilization (hpf), both nZnO and Zn(II) delayed hatching at all doses, and inhibited hatching at 1 and 5 mg/L at 96 hpf. Both nZnO and Zn(II) lead to induction of metallothionein (mt2) in both embryos and eleuthero-embryos at all concentrations. Transcripts of oxidative stress related genes cat and Cu/Zn sod were also altered. Moreover, we show for the first time that nZnO exposure results in transcriptional changes of pro-inflammatory cytokines IL-1ß and TNFa. Overall, transcriptional alterations were higher in embryos than eleuthero-embryos. The similarities of the effects lead to the conclusion that effects of nZnO are mainly related to the release of Zn(II).
    Lanthanum from a modified clay used in eutrophication control is bioavailable to the marbled crayfish (Procambarus fallax f. virginalis)
    Oosterhout, F. van; Goitom, E. ; Roessink, I. ; Lurling, M. - \ 2014
    PLoS ONE 9 (2014)7. - ISSN 1932-6203 - 9 p.
    phosphorus binding clay - copper nickel smelters - rare-earth-elements - heavy-metals - fresh-water - lakes - toxicity - accumulation - phoslock(r) - sediment
    To mitigate eutrophication in fresh standing waters the focus is on phosphorus (P) control, i.e. on P inflows to a lake as well as a lake's sediment as internal P source. The in-lake application of the lanthanum (La) modified clays – i.e. La modified bentonite (Phoslock) or La modified kaolinite, aim at dephosphatising the water column and at reducing the release of P from a lake's sediment. Application of these clays raises the question whether La from these clays can become bioavailable to biota. We investigated the bioavailability of La from Phoslock in a controlled parallel groups experiment in which we measured the La in carapace, gills, ovaries, hepatopancreas and abdominal muscle after 0, 14 and 28 days of exposure to Phoslock. Expressing the treatment effect as the difference of the median concentration between the two treatment groups (Phoslock minus control group) yield the following effects, the plus sign (+) indicating an increase, concentrations in µg g-1 dry weight: Day 14: carapace +10.5 µg g-1, gills +112 µg g-1, ovaries +2.6 µg g-1, hepatopancreas +32.9 µg g-1 and abodminal muscle +3.2 µg g-1. Day 28: carapace +17.9 µg g-1; gills +182 µg g-1; ovaries +2.2 µg g-1; hepatopancreas +41.9 µg g-1 and abodminal muscle +7.6 µg g-1, all effects were statistically significant. As La from Phoslock is bio-available to and taken up by the marbled crayfishes (Procambarus fallax f. virginalis), we advocate that the application of in-lake chemical water treatments to mitigate eutrophication should be accompanied by a thorough study on potential side effects
    Vibrio vulnificus outbreaks in Dutch eel farms since 1996: strain diversity and impact.
    Haenen, O.L.M. ; Zanten, E. van; Jansen, R. ; Roozenburg, I. ; Engelsma, M.Y. ; Dijkstra, A. ; Boers, S.A. ; Voorbergen-Laarman, M. ; Möller, A.V.M. - \ 2014
    Diseases of Aquatic Organisms 108 (2014)3. - ISSN 0177-5103 - p. 201 - 209.
    diseased european eel - anguilla-anguilla - biotype 2 - clinical-manifestations - fresh-water - serovar-e - infection - pathogen - tilapia - fish
    Vibrio vulnificus is a potentially zoonotic bacterial pathogen of fish, which can infect humans (causing necrotic fasciitis). We analysed 24 V. vulnificus isolates (from 23 severe eel disease outbreaks in 8 Dutch eel farms during 1996 to 2009, and 1 clinical strain from an eel farmer) for genetic correlation and zoonotic potential. Strains were typed using biotyping and molecular typing by high-throughput multilocus sequence typing (hiMLST) and REP-PCR (Diversilab®). We identified 19 strains of biotype 1 and 5 of biotype 2 (4 from eels, 1 from the eel farmer), that were subdivided into 8 MLST types (ST) according to the international standard method. This is the first report of V. vulnificus biotype 1 outbreaks in Dutch eel farms. Seven of the 8 STs, of unknown zoonotic potential, were newly identified and were deposited in the MLST database. The REP-PCR and the MLST were highly concordant, indicating that the REP-PCR is a useful alternative for MLST. The strains isolated from the farmer and his eels were ST 112, a known potential zoonotic strain. Antimicrobial resistance to cefoxitin was found in most of the V. vulnificus strains, and an increasing resistance to quinolones, trimethoprim + sulphonamide and tetracycline was found over time in strain ST 140. Virulence testing of isolates from diseased eels is recommended, and medical practitioners should be informed about the potential risk of zoonotic infections by V. vulnificus from eels for the prevention of infection especially among high-risk individuals. Additional use of molecular typing methods such as hiMLST and Diversilab® is recommended for epidemiological purposes during V. vulnificus outbreaks.
    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.
    Modeling global N2O emissions from aquatic systems
    Ivens, W.P.M.F. ; Tysmans, D.J.J. ; Kroeze, C. ; Löhr, A.J. ; Wijnen, J. van - \ 2011
    Current Opinion in Environmental Sustainability 3 (2011)5. - ISSN 1877-3435 - p. 350 - 358.
    nitrous-oxide emissions - fresh-water - rivers - future - budget - inputs - ocean - combustion - trends - impact
    Human activities on land have increased the N inputs to rivers and coastal waters worldwide. This increased aquatic emissions of nitrous oxide (N2O). Global, spatially explicit modeling of N flows from land to sea and associated N2O emissions have been developed for a number of decades. During the 1990s, global N2O studies focused to a large extent on closing the global budget. Since then, aquatic emissions of N2O have been subject of scientific discussions. Although it is widely recognized that human activities on land increase aquatic N2O emissions, quantification is difficult because of lack of experimental data. In order to reduce uncertainties, additional long-term studies are required measuring N and N2O concentrations in aquatic systems. More explicit modeling of N2O formation and the underlying biogeochemical cycling in aquatic systems would improve our understanding of aquatic N2O emissions. Global models preferably include both N cycling, N2O production, and river transport in a spatially explicit way, as well as biogeochemical cycling in coastal seas and oceans. Integrative studies are needed that account for the interactions between different impacts of increased levels of reactive N in the environment. We argue that it is still difficult to close the global N2O budget.
    Effects of aquatic vegetation type on denitrification
    Veraart, A.J. ; Bruijne, W.J.J. de; Peeters, E.T.H.M. ; Klein, J.J.M. de; Scheffer, M. - \ 2011
    Biogeochemistry 104 (2011)1-3. - ISSN 0168-2563 - p. 267 - 274.
    sloten - waterplanten - zoetwaterecologie - stikstof - aquatische ecologie - nitrificatie - ditches - aquatic plants - freshwater ecology - nitrogen - aquatic ecology - nitrification - fresh-water - submersed macrophytes - drainage ditches - nitrate removal - lemna-minor - sediment - plant - eutrophication - ecosystems
    In a microcosm 15N enrichment experiment we tested the effect of floating vegetation (Lemna sp.) and submerged vegetation (Elodea nuttallii) on denitrification rates, and compared it to systems without macrophytes. Oxygen concentration, and thus photosynthesis, plays an important role in regulating denitrification rates and therefore the experiments were performed under dark as well as under light conditions. Denitrification rates differed widely between treatments, ranging from 2.8 to 20.9 µmol N m-2 h-1, and were strongly affected by the type of macrophytes present. These differences may be explained by the effects of macrophytes on oxygen conditions. Highest denitrification rates were observed under a closed mat of floating macrophytes where oxygen concentrations were low. In the light, denitrification was inhibited by oxygen from photosynthesis by submerged macrophytes, and by benthic algae in the systems without macrophytes. However, in microcosms with floating vegetation there was no effect of light, as the closed mat of floating plants caused permanently dark conditions in the water column. Nitrate removal was dominated by plant uptake rather than denitrification, and did not differ between systems with submerged or floating plants
    Warming can boost denitrification disproportionately due to altered oxygen dynamics
    Veraart, A.J. ; Klein, J.J.M. de; Scheffer, M. - \ 2011
    PLoS ONE 6 (2011)3. - ISSN 1932-6203 - 6 p.
    nitrous-oxide - estuarine sediments - gaseous nitrogen - fresh-water - temperature - nitrate - nitrification - ecosystems - soils - model
    Background - Global warming and the alteration of the global nitrogen cycle are major anthropogenic threats to the environment. Denitrification, the biological conversion of nitrate to gaseous nitrogen, removes a substantial fraction of the nitrogen from aquatic ecosystems, and can therefore help to reduce eutrophication effects. However, potential responses of denitrification to warming are poorly understood. Although several studies have reported increased denitrification rates with rising temperature, the impact of temperature on denitrification seems to vary widely between systems. Methodology/Principal Findings - We explored the effects of warming on denitrification rates using microcosm experiments, field measurements and a simple model approach. Our results suggest that a three degree temperature rise will double denitrification rates. By performing experiments at fixed oxygen concentrations as well as with oxygen concentrations varying freely with temperature, we demonstrate that this strong temperature dependence of denitrification can be explained by a systematic decrease of oxygen concentrations with rising temperature. Warming decreases oxygen concentrations due to reduced solubility, and more importantly, because respiration rates rise more steeply with temperature than photosynthesis. Conclusions/Significance - Our results show that denitrification rates in aquatic ecosystems are strongly temperature dependent, and that this is amplified by the temperature dependencies of photosynthesis and respiration. Our results illustrate the broader phenomenon that coupling of temperature dependent reactions may in some situations strongly alter overall effects of temperature on ecological processes
    Estimating the critical phosphorus loading of shallow lakes with the ecosystem model PCLake: Sensitivity, calibration and uncertainty
    Janse, J.H. ; Scheffer, M. ; Lijklema, L. ; Liere, L. van; Sloot, J.S. ; Mooij, W.M. - \ 2010
    Ecological Modelling 221 (2010)4. - ISSN 0304-3800 - p. 654 - 665.
    ecological models - fresh-water - eutrophication - prediction - simulation - netherlands - management - retention
    There is avast body of knowledge that eutrophication of lakes may cause algal blooms. Among lakes, shallow lakes are peculiar systems in that they typically can be in one of two contrasting (equilibrium) states that are self-stabilizing: a 'clear' state with submerged macrophytes or a 'turbid' state dominated by phytoplankton. Eutrophication may cause a switch from the clear to the turbid state, if the P loading exceeds a critical value. The ecological processes governing this switch are covered by the ecosystem model PCLake, a dynamic model of nutrient cycling and the biota in shallow lakes. Here we present an extensive analysis of the model, using a three-step procedure. (1) A sensitivity analysis revealed the key parameters for the model output. (2) These parameters were calibrated on the combined data on total phosphorus, chlorophyll-a, macrophytes cover and Secchi depth in over 40 lakes. This was done by a Bayesian procedure. giving a weight to each parameter setting based on its likelihood. (3) These weights were used for an uncertainty analysis, applied to the switchpoints (critical phosphorus loading levels) calculated by the model. The model was most sensitive to changes in water depth, P and N loading, retention time and lake size as external input factors, and to zooplankton growth rate, settling rates and maximum growth rates of phytoplankton and macrophytes as process parameters. The results for the 'best run' showed an acceptable agreement between model and data and classified nearly all lakes to which the model was applied correctly as either 'clear' (macrophyte-dominated) or 'turbid' (phytoplankton-dominated). The critical loading levels for a standard lake showed about a factor two uncertainty due to the variation in the posterior parameter distribution. This study calculates in one coherent analysis uncertainties in critical phosphorus loading, a parameter that is of great importance to water quality managers.
    N:P:Si nutrient export ratios and ecological consequences in coastal seas evaluated by the ICEP approach
    Garnier, J. ; Beusen, A. ; Thieu, V. ; Billen, G. ; Bouwman, A.F. - \ 2010
    Global Biogeochemical Cycles 24 (2010)4. - ISSN 0886-6236 - 12 p.
    dinoflagellate alexandrium-tamarense - western black-sea - baltic sea - north-sea - marine eutrophication - yangtze-river - danube river - seine river - fresh-water - land-use
    The Indicator for Coastal Eutrophication Potential (ICEP) for river nutrient export of nitrogen, phosphorus, and silica at the global scale was first calculated from available measurement data. Positive values of ICEP indicate an excess of nitrogen and phosphorus over silica and generally coincide with eutrophication. The sign of ICEP based on measured nutrient fluxes was in good agreement with the corresponding one calculated from the Global-NEWS models for more than 5000 watersheds in the world. Calculated ICEP for the year 2050 based on Global NEWS data for the four Millennium Ecosystem Assessment scenarios show increasing values particularly in developing countries. For further evaluation of the ICEP at the outlet of the rivers of the world based on measurements, there is a need for additional determination silica fluxes and concentrations, which are scarcely documented.
    The health status of European silver eels, Anguilla anguilla, in the Dutch River Rhine Watershed and lake IJsselmeer
    Haenen, O.L.M. ; Lehmann, J. ; Engelsma, M.Y. ; Stürenberg, F.J. ; Roozenburg, I. ; Kerkhoff, S. ; Klein Breteler, J.G.P. - \ 2010
    Aquaculture 309 (2010)1-4. - ISSN 0044-8486 - p. 15 - 24.
    crassus nematoda - herpesvirus-anguillae - parasite communities - fresh-water - netherlands - l. - dracunculoidea - infections - germany - diversity
    The worldwide decline of the eel population is thought to be caused by several factors, among which eel diseases. To investigate diseases of European silver eels Anguilla anguilla in the Netherlands, in Nov–Dec 2004 12 silver eels, and in Aug–Dec 2005 80 eels were caught in downstream parts (rivers) of the River Rhine and in Lake IJsselmeer. The eels were measured and weighed, necrotized, and individually checked for presence of external and internal parasites, bacterial infections and viruses, and blood smears were made for haematology. This is the first multidisciplinary study of the health of Dutch silver eels. In the small (2 × 6 eels) pilot study of 2004 in the River Rhine and Lake IJsselmeer respectively, most eels showed aspecific fin haemorrhages, some had ectoparasites, nearly none had parasites in the intestine, half of the groups had Anguillicola crassus in their swimbladder, only few had Trypanosoma's in their blood, and no primary virus or bacterial infections were found, although one eel from Lake IJsselmeer was positive for anguillid herpesvirus 1 (AngHV-1, former Herpesvirus anguillae, HVA) in the PCR test only. The blood of all 6 and 2/6 of the eels respectively was considered abnormal, and the eels had a proper condition. In 2005, in 50 eels from the River Rhine and 30 from Lake IJsselmeer respectively, again aspecific fin haemorrhages were often seen, some of the eels had ectoparasites and parasites in the intestine, most eels had A. crassus in their swimbladder, 32% and 53% had Trypanosoma's in their blood, from 44% and 13% of the eels AngHV-1 was isolated, and 44% and 27% were tested positive by PCR, with a peak in August, 10% of both groups of eels had an internal bacterial infection, mostly due to Aeromonas spp. The blood of about half of the eels was considered abnormal, but the eels had a proper condition. It was concluded, that the silver eels of this study had a proper Fulton condition factor (values 2.00–2.26), with aspecific fin haemorrhages, often were Trypanosoma-, A. crassus- and AngHV-1-infected, dependent on the season, and often showed an abnormal haematology. A. crassus causes injuries and is a chronic stress factor, more than the other parasites, which were mostly found less prevalent. In fact, lymphocytosis was directly related to A. crassus infection. Stress and injuries by A. crassus might induce disease through the presence of virus (AngHV-1), relevant in the health status of the silver eels during their spawning migration if ambient water temperatures would enhance a clinical infection of AngHV-1 disease. Moreover this virus might potentially decrease the survival of the silver eels by itself, because spawning migration to the Sargasso Sea takes wild eels to temperate/tropical areas in which the clinical infection by AngHV-1 is surely enhanced.
    Cyanobacteria blooms cannot be controlled by effective microorganisms (EM) from mud- or Bokashi-balls
    Lürling, M.F.L.L.W. ; Tolman, Y. ; Oosterhout, J.F.X. - \ 2010
    Hydrobiologia 646 (2010)1. - ISSN 0018-8158 - p. 133 - 143.
    fresh-water - phosphorus uptake - phytoplankton - nutrient - bacteria - bacterioplankton - nuisance - cultures - toxins - algae
    In controlled experiments, the ability of ‘‘Effective Microorganisms (EM, in the form of mudballs or Bokashi-balls)’’ was tested for clearing waters from cyanobacteria. We found suspensions of EM-mudballs up to 1 g l-1 to be ineffective in reducing cyanobacterial growth. In all controls and EM-mudball treatments up to 1 g l-1 the cyanobacterial chlorophyll-a (Chl-a) concentrations increased within 4 weeks from&120 to 325–435 lg l-1. When pieces of EM-mudballs (42.5 g) were added to 25-l lake water with cyanobacteria, no decrease of cyanobacteria as compared to untreated controls was observed. In contrast, after 4 weeks cyanobacterial Chl-a concentrations were significantly higher in EM-mudball treatments (52 lg l-1) than in controls (20 lg l-1). Only when suspensions with extremely high EM-mudball concentrations were applied (i.e., 5 and 10 g l-1), exceeding the recommended concentrations by orders of magnitude, cyanobacterial growth was inhibited and a bloom forming concentration was reduced strongly. In these high dosing treatments, the oxygen concentration dropped initially to very low levels of 1.8 g l-1. This was most probably through forcing strong light limitation on the cyanobacteria caused by the high amount of clay and subsequent high turbidity of the water. Hence, this study yields no support for the hypothesis that EM is effective in preventing cyanobacterial proliferation or in terminating blooms. We consider EM products to be ineffective because they neither permanently bind nor remove phosphorus from eutroficated systems, they have no inhibiting effect on cyanobacteria, and they could even be an extra source of nutrients.
    Nonylphenol mass transfer from field-aged sediments and subsequent biodegradation in reactors mimicking different river conditions
    Weert, J.P.A. de; Streminska, M.A. ; Hua, D. ; Grotenhuis, J.T.C. ; Langenhoff, A.A.M. ; Rijnaarts, H.H.M. - \ 2010
    Journal of Soils and Sediments 10 (2010)1. - ISSN 1439-0108 - p. 77 - 88.
    fresh-water - lakes - alkylphenols - desorption - kinetics - octylphenol - ecosystems - events
    Sediments can function as secondary source for water pollution of aerobically biodegradable non-halogenated organic compounds, which are persistent in anaerobic sediments. The mass transfer of compounds from sediment to bulk water depends on hydraulic conditions. In this study, desorption, mass transfer and biodegradation are investigated under settled and resuspended sediment conditions for branched nonylphenol (NP), which was used as model compound for aerobically biodegradable and anaerobic persistent compounds. Continuous flow through reactor experiments were performed in duplicate with aged NP polluted sediment under sterile and non-sterile conditions to investigate the mass transfer and combined mass transfer and biodegradation. The mass transfer of NP from the sediment bed to the bulk water decreased from 5.1 +/- 0.6 mu g d(-1) to a stable value of 0.3 +/- 0.02 mu g d(-1). The desorbed NP in the non-sterile reactors was biodegraded in the first 20 days of the experiment. At the end of the settled sediment conditions, the biodegradation became very limited, and the mass transfer was comparable to the mass transfer under sterile conditions. Upon resuspension, the NP concentration in the bulk water increased instantaneously in all reactors with a factor of 100. This immediate, increased mass transfer of NP from the sediment was larger than the amount that can be biodegraded under optimal conditions. Under non-sterile conditions, a second increase in the mass transfer was observed. However, the amount of desorbing NP during this second increase in mass transfer can be biodegraded under optimal environmental conditions. NP desorbs continuously at low concentrations from the sediment bed into the bulk water, which can almost be completely biodegraded. Resuspension of NP-polluted sediment initially led to an increase in the desorbing NP concentrations and can be followed by a subsequent reduction of the concentrations due to biodegradation under environmental conditions where biodegradation of NP can occur.
    Industrial dry electro-stunning followed by chilling and decapitation as a slaughter method in Claresse (Heteroclarias sp.) and African catfish (Clarius gariepinus)
    Sattari, A. ; Lambooij, E. ; Sharifi, H. ; Abbink, W. ; Reimert, H. ; Vis, J.W. van de - \ 2010
    Aquaculture 302 (2010)1-2. - ISSN 0044-8486 - p. 100 - 105.
    anguilla-anguilla l. - bass dicentrarchus-labrax - behavioral-assessment - humane slaughter - product quality - welfare aspects - fresh-water - eels - consciousness
    This study evaluated the industrial application of dry electro-stunning for Claresse® and African catfish via monitoring of brain and heart activities, behavioral responses to noxious stimuli and meat quality. Dry electro-stunning (150 V, AC + DC, 100 Hz) of Claresse® for 0.7 ± 0.2 s (mean ± SD) resulted in unconsciousness for 48 ± 15 s, fulfilling the welfare requirements for obtaining pre-slaughter unconsciousness in less than 1 s. Current input for 5.2 ± 0.5 s with a measured current of 0.57 ± 0.16 A followed by chilling, resulted in prolonged unconsciousness for 124 ± 20 s in Claresse®. Loss of behavioral responses to noxious stimuli and then death within 5 min in 9 out of 10 African catfish resulted from stunning for 9.1 ± 0.4 s (0.91 ± 0.18 A) followed by decapitation. The meat quality did not reveal any difference in color between electro-stunned (0.76 A, 150 V, AC + DC for 15 s) and chilled-only Claresse®. Although flesh acidification was significantly higher in the stunned group on the day of the experiment, after 24 h the groups showed similar pH changes for the next six days. We conclude that dry electro-stunning (150 V, AC + DC) followed by chilling and decapitation is a reliable method for industrial pre-slaughter unconsciousness of Claresse® and African catfish and stunning (150 V, AC + DC) leaves no significant effect on flesh quality of Claresse® compared to chilling method.
    Tailfin clipping, a painful procedure: Studies on Nile tilapia and common carp
    Roques, J.A.C. ; Abbink, W. ; Geurds, F. ; Vis, J.W. van de; Flik, G. - \ 2010
    Physiology and Behavior 101 (2010)4. - ISSN 0031-9384 - p. 533 - 540.
    branchial chloride cells - fresh-water - oreochromis-niloticus - oncorhynchus-mykiss - cyprinus-carpio - rainbow-trout - na+/k+-atpase - fish - nociception - perception
    The fish welfare debate is intensifying. Consequently, more research is carried out to further our knowledge on fish welfare in aquaculture. We define here a series of key parameters to substantiate an acute response to a supposedly painful stimulus: a standardized tailfin clip. Ultrastructural analysis of common carp (Cyprinus carpio) tailfin indicates the presence of A-d and C-type axons, which are typical for transmitting nociceptive signals in (higher) vertebrates. In Nile tilapia (Oreochromis niloticus), responses to a tailfin clip were studied and the unavoidable acute stress associated with the handling required for this procedure. A series of key parameters for further studies was defined. The responses seen in ‘classical’ stress parameters (e.g., changes in plasma cortisol, glucose and lactate levels) did not allow discrimination between the clipping procedure and the handling stress. However, three parameters indicated a differential, stronger response to the clip stimulus itself: first, swimming activity increased more and clipped fish spent more time in the light (in a tank where half the volume is covered by dark material); second, the gill's mucus cells released their content as observed 1 h after the clip, and this response is transient (no longer observed at 6 h post clipping). Third, branchial Na+/K+-ATPase activity assayed in vitro was not affected by the procedures, but a remarkable migration of Na+/K+-ATPase immunoreactive (chloride) cells into the lamellar epithelium was observed as of 6 h post clipping. We conclude that the differential response to clipping supports that this is a painful procedure that evokes a transient specific physiological status.
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