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Rimet F.,French National Institute for Agricultural Research | Trobajo R.,Institute of Agriculture and Food Research and Technology | Mann D.,Royal Botanic Garden Edinburgh | Kermarrec L.,ASCONIT Consultants | And 3 more authors.
Protist | Year: 2014

DNA barcoding, being developed for biomonitoring, requires a database of reference sequences and knowledge of how much sequences can deviate before they are assigned to separate species. The molecular hunt for hidden species also raises the question of species definitions. We examined whether there are objective criteria for sequence-based species delimitation in diatoms, using Nitzschia palea, an important monophyletic indicator species already known to contain cryptic diversity. Strains from a wide geographical range were sequenced for 28S rRNA, COI and rbcL. Homogeneity indices and the Chao index failed to objectively select a precise number of species existing in N. palea as well as an evolutionary method based on coalescence theory. COI always gave higher diversity estimations than 28S rRNA or rbcL. Mating data did not provide a precise calibration of molecular species thresholds. Rarefaction curves indicated that further MOTUs would be detected with more isolates than we sampled (81 clones, 42 localities). Although some genotypes had intercontinental distributions, there was a positive relationship between genetic and geographical distance, suggesting even higher richness than we assessed, given that many regions were not sampled. Overall, no objective criteria were found for species separation; instead barcoding will need a consensual approach to molecular species limits. © 2014 Elsevier GmbH. Source

Benito X.,Institute of Agriculture and Food Research and Technology | Benito X.,Rovira i Virgili University | Trobajo R.,Institute of Agriculture and Food Research and Technology | Ibanez C.,Institute of Agriculture and Food Research and Technology
Journal of Paleolimnology | Year: 2015

The contemporary distribution of benthic diatoms and their use as ecological indicators were examined in a coastal wetland, the Ebro Delta, as a representative of environmental conditions in Mediterranean coastal wetlands. A total of 424 diatom taxa were identified across 24 sites encompassing a wide range of wetland habitat types (coastal lagoons, salt and brackish marshes, shallow bays, microbial mats and nearshore marine waters) and conductivities. Canonical correspondence analysis showed that water conductivity and water depth were the main factors structuring the diatom assemblages. Cluster analysis identified five habitat types according to the similarity in diatom species composition: salt marshes, brackish marshes, brackish coastal lagoons and bays, coastal lagoons with fresher conditions, and nearshore open sea. For each wetland habitat, diatom indicator species were identified. Partial canonical correspondence analysis showed that water conductivity, a proxy for salinity, was the most statistically significant and independent variable for explaining the distribution of benthic diatoms in the study area. A transfer function, using a weighted average regression model, was developed for conductivity and displayed reasonable performance (r2 = 0.64; RMSEP = 0.302 log10 mS/cm). Our study in the Ebro Delta provides a basis for using diatom assemblages to make quantitative conductivity inferences, and for using diatom indicator species to identify wetland habitats. These approaches are complementary and may be valuable for paleoenvironmental studies of (1) effects of large-scale, natural changes in the Delta (e.g. sea-level fluctuations), and (2) impacts of short-term anthropogenic changes, such as the introduction and development of rice agriculture. © 2015, Springer Science+Business Media Dordrecht. Source

Fantke P.,University of Stuttgart | Wieland P.,University of Stuttgart | Wieland P.,Robert Bosch GmbH | Juraske R.,ETH Zurich | And 5 more authors.
Environmental Science and Technology | Year: 2012

An approach for estimating human exposure to pesticides via consumption of six important food crops is presented that can be used to extend multimedia models applied in health risk and life cycle impact assessment. We first assessed the variation of model output (pesticide residues per kg applied) as a function of model input variables (substance, crop, and environmental properties) including their possible correlations using matrix algebra. We identified five key parameters responsible for between 80% and 93% of the variation in pesticide residues, namely time between substance application and crop harvest, degradation half-lives in crops and on crop surfaces, overall residence times in soil, and substance molecular weight. Partition coefficients also play an important role for fruit trees and tomato (Kow), potato (Koc), and lettuce (Kaw, Kow). Focusing on these parameters, we develop crop-specific models by parametrizing a complex fate and exposure assessment framework. The parametric models thereby reflect the framework's physical and chemical mechanisms and predict pesticide residues in harvest using linear combinations of crop, crop surface, and soil compartments. Parametric model results correspond well with results from the complex framework for 1540 substance-crop combinations with total deviations between a factor 4 (potato) and a factor 66 (lettuce). Predicted residues also correspond well with experimental data previously used to evaluate the complex framework. Pesticide mass in harvest can finally be combined with reduction factors accounting for food processing to estimate human exposure from crop consumption. All parametric models can be easily implemented into existing assessment frameworks. © 2012 American Chemical Society. Source

Fantke P.,University of Stuttgart | Juraske R.,ETH Zurich | Anton A.,Institute of Agriculture and Food Research and Technology | Friedrich R.,University of Stuttgart | And 2 more authors.
Environmental Science and Technology | Year: 2011

A new dynamic plant uptake model is presented to characterize health impacts of pesticides applied to food crops, based on a flexible set of interconnected compartments. We assess six crops covering a large fraction of the worldwide consumption. Model estimates correspond well with observed pesticide residues for 12 substance-crop combinations, showing residual errors between a factor 1.5 and 19. Human intake fractions, effect and characterization factors are provided for use in life cycle impact assessment for 726 substance-crop combinations and different application times. Intake fractions typically range from 10 -2 to 10 -8 kg intake kgapplied-1. Human health impacts vary up to 9 orders of magnitude between crops and 10 orders of magnitude between pesticides, stressing the importance of considering interactions between specific crop-environments and pesticides. Time between application and harvest, degradation half-life in plants and residence time in soil are driving the evolution of pesticide masses. We demonstrate that toxicity potentials can be reduced up to 99% by defining adequate pesticide substitutions. Overall, leafy vegetables only contribute to 2% of the vegetal consumption, but due to later application times and higher intake fractions may nevertheless lead to impacts comparable or even higher than via the larger amount of ingested cereals. © 2011 American Chemical Society. Source

Itoiz E.S.,Institute of Agriculture and Food Research and Technology | Fantke P.,University of Stuttgart | Juraske R.,ETH Zurich | Kounina A.,Ecole Polytechnique Federale de Lausanne | Vallejo A.A.,Institute of Agriculture and Food Research and Technology
Chemosphere | Year: 2012

Lettuce greenhouse experiments were carried out from March to June 2011 in order to analyze how pesticides behave from the time of application until their intake via human consumption taking into account the primary distribution of pesticides, field dissipation, and post-harvest processing. In addition, experimental conditions were used to evaluate a new dynamic plant uptake model comparing its results with the experimentally derived residues. One application of imidacloprid and two of azoxystrobin were conducted. For evaluating primary pesticide distribution, two approaches based on leaf area index and vegetation cover were used and results were compared with those obtained from a tracer test. High influence of lettuce density, growth stage and type of sprayer was observed in primary distribution showing that low densities or early growth stages implied high losses of pesticides on soil. Washed and unwashed samples of lettuce were taken and analyzed from application to harvest to evaluate removal of pesticides by food processing. Results show that residues found on the Spanish preharvest interval days were in all cases below officially set maximum residue limits, although it was observed that time between application and harvest is as important for residues as application amounts. An overall reduction of 40-60% of pesticides residues was obtained from washing lettuce. Experimentally derived residues were compared with modeled residues and deviate from 1.2 to 1.4 for imidacloprid and azoxystrobin, respectively, presenting good model predictions. Resulting human intake fractions range from 0.045kgintakekgapplied-1 for imidacloprid to 0.14kgintakekgapplied-1 for azoxystrobin. © 2012 Elsevier Ltd. Source

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