Diatom assemblages in Portuguese temporary rivers

During a survey of benthic diatoms in watercourses from Portugal in spring and summer 2006 and 2007, 76 sites in temporary streams (according to the National Water Institute classification) have been studied. These streams belong to the Ribeiras do Algarve (10 sites), Guadiana (19 sites), Mira (7 sites), Sado (16 sites), Tejo (20 sites), and Douro (4 sites) watersheds. Among these 76 sites, the National Water Institute classified only 48 as reference sites, and only these were therefore considered in the statistical analysis performed. A total of 276 diatom taxa have been identified in the 48 reference sites, from which 112 were present in abundance above 2% in at least one inventory. The most frequent taxa, present in more than 50% of the studied sites, were Achnanthidium minutissimum (Kützing) Czarnecki, Amphora pediculus (Kützing) Grunow, Cocconeis euglypta Ehrenberg, Eolimna minima (Grunow) Lange-Bertalot, Gomphonema parvulum Kützing, G. rosenstockianum Lange-Bertalot & E. Reichardt, Navicula gregaria Donkin, N. veneta Kützing, Nitzschia inconspicua Grunow and Planothidium frequentissimum (Lange-Bertalot) Lange-Bertalot. These are neutrophilous to alcaliphilous, mesosaprobous to -meso-saprobous, eutraphentic to indifferent taxa. Furthermore, a multivariate analysis relating diatom assemblages with environmental parameters is presented and the ecological preferences of not yet well known taxa, such as G. rosenstockianum, are provided

MORPHOLOGICAL DIVERSITY WITHIN THE ACHNANTHIDIUM MINUTISSIMUM SPECIES COMPLEX

During a survey of benthic diatoms sampled in watercourses from Mainland Portugal, several Achnanthidium populations morphologically ascribable to the A. minutissimum complex have been found. They clearly belong to the genus Achnanthidium on the basis of the valve outline, radiate striae, uniseriate, wider spaced striae in the centre of the valve and cells shallow‐V‐shaped in girdle view. The raphe valve has a straight central raphe hardly expanding at the centre and a row of elongated areolae in the mantle. Within the genus Achnanthidium these morphotypes belong to the complex of A. minutissimum (Kützing) Czarnecki, due to their straight terminal raphe fissures, in opposition to the species with terminal raphe fissures clearly deflected on the same side of the valve. Since these individuals were abundant in numerous sites, especially in the Centre and North of Portugal, a more detailed examination was performed by means of light (LM) and scanning electron microscopy (SEM). Furthermore, the examination of the environmental characteristics of the sites where they have been sampled allowed us to gather sufficient information on the ecological preferences of the different taxa. The main features that allow the separation of these taxa among each other and from all the other known Achnanthidium species are the different valve outline and dimensions, the size and shape of the central area, the apices shape and the density of the striae throughout the valve and near the apices. The LM and SEM analyses of the type materials of Achnanthidium microcephalum Kützing, Achnanthes minutissima Kützing and A. minutissima var. cryptocephala Grunow in Van Heurck have been done in order to help to clarify the taxonomy of this group. A comparison with the literature on Achnanthidium minutissimum species complex was performed, but the new Portuguese Achnanthidium taxa present a set of distinct morphological and ecological features that separate them well from all other similar species. Furthermore, two of these taxa have already been recorded from French watercourses with similar environmental characteristics

Identifying the origins of local atmospheric deposition in the steel industry basin of Luxembourg using the chemical and isotopic composition of the lichen Xanthoria parietina

Trace metal atmospheric contamination was assessed in one of the oldest European industrial sites of steel production situated in the southern part of the Grand-Duchy of Luxembourg. Using elemental ratios as well as Pb, Sr, and Nd isotopic compositions as tracers, we found preliminary results concerning the trace metal enrichment and the chemical/isotopic signatures of the most important emission sources using the lichen Xanthoria parietina sampled at 15 sites along a SW-NE transect. The concentrations of these elements decreased with increasing distance from the historical and actual steel-work areas. The combination of the different tracers (major elements, Rare Earth Element ratios, Pb, Sr and Nd isotopes) enabled us to distinguish between three principal sources: the historical steel production (old tailings corresponding to blast-furnace residues), the present steel production (industrial sites with arc electric furnace units) and the regional background (baseline) components. Other anthropogenic sources including a waste incinerator and major roads had only weak impacts on lichen chemistry and isotopic ratios. The correlation between the Sr and Nd isotope ratios indicated that the Sr–Nd isotope systems represented useful tools to trace atmospheric emissions of factories using scrap metal for steel production

Performance of leaf wetness sensor used in winter wheat disease management

Wetness on crop leaves has particular epidemiological significance because many fungal diseases affect plants only when free moisture is present on leaves. The leaf wetness sensor detects the presence of wetness on a leaf’s surface, enabling researchers and producers to forecast disease and protect plant canopies, and consequently to optimize fungicide application and often reduce environmental load. This research project aimed at better understanding the leaf wetness duration and its influence in winter wheat disease. Measurement of surface wetness duration by three electronic flat-plate sensors (Model 237-Campbell Scientific, Inc) in wheat fields were compared with tactile and visual observations in replicated field experiments at the site of Arlon (Belgium) during the period May-July 2006 and April-July 2007. Performances of the sensor were evaluated against SWEB model outputs and visual observations of disease symptoms. On the field, dew-onset and dry-off of wetness on leaves were observed visually (with a flash light for dew-onset) at 15-minute intervals. Each sensor was placed close the flag leaf. For the three sensors, the two dew-onset and dry-off times measured in both 2006 and 2007 crop seasons gave a leaf wetness duration (LWD) which was on average one hour less than visual observations. In order to establish a relationship between the surface wetness periods and wheat foliar diseases, LWD was compared with the Septoria leaf blotch (SLB) development risk (main winter wheat disease). A minimal surface wetness duration favourable to infection for SLB was established.Weather-radar data ; Rainfall ; Septoria tritici ; Forecasting system ; Winter wheat ; Epidemiological model ; Surface wetness duration ; Spatializatio

Dynamic NanoSIMS ion imaging of unicellular freshwater algae exposed to copper

This work demonstrates the capabilities of nanoscale secondary-ion mass spectrometry, using the Cameca NanoSIMS50 ion microprobe, to detect and image the copper-ion distribution in microalgal cells exposed to nanomolar and micromolar copper concentrations. In parallel to 63Cu− secondary-ion maps, images of 12C−, 12C14N−, and 31P− secondary ions were collected and analysed. A correlation of 63Cu− secondary-ion maps with those found for 12C14N− and 31P− demonstrated the possible association of Cu with cell components rich in proteins and phosphorus. The results highlighted the potential of NanoSIMS for intracellular tracking of essential trace elements such as Cu in single cells of the microalga Chlorella kesslerii. Figure 12C14N-, 63Cu- secondary-ion distributions in algal cel

Rouille brune du blé, un modèle pour évaluer les risques

peer reviewedL’article présente un outil de prévision de la rouille brune au G.-D. de Luxembourg. De 2000 à 2003, cette maladie apparaissait à la fin de l’épiaison, mais depuis 2003, elle apparaît de plus en plus tôt (GS45 stade gonflement). Cette apparition précoce est probablement liée à des températures printanières supérieures par rapport à la normale 1971-2000. Une analyse des données météorologiques nocturnes et des données d’observation de la maladie sur quatre sites expérimentaux (Everlange, Christnach, Burmerange et Reuler) entre 2000 et 2003 a révélé une forte corrélation positive entre la prédiction de la maladie basée sur le critère d’au moins 12 heures consécutives avec une température comprise entre 8 et 16°C et une humidité supérieure à 60% et la maladie observée sur la F1 (R = 0.93 ; P < 0.05) et sur la F2 (R = 0.87 ; P < 0.05). Les sorties de ce modèle qui a été développé sur base d’une approche stochastique ont été utilisées dans les bulletins d’avertissements diffusés conjointement par le Centre de Recherche Public – Gabriel Lippmann et l’Université de Liège-Campus d’Arlon à partir de 2004. La mise en application de ce modèle a montré un taux de réussite oscillant entre 80 et 85% pour la simulation de la rouille brune au G.-D. de Luxembourg. L’effort se poursuit pour spatialiser les sorties du modèle sur tout le territoire luxembourgeois et faciliter son utilisation par tous les vulgarisateurs agricoles

Weed populations in the main cultures of Luxembourg: control options and monitoring in a complex environmental and political framework

Chemische Unkrautbekämpfung wird aufgrund von ökotoxikologischen Bedenken diskutiert. Um Landwirten zu helfen, die Ausbreitung von Unkräutern auch bei sinkender Verfügbarkeit von Herbiziden begrenzen zu können, wurden Projekte zu modifizierten Fruchtfolgen zur Reduzierung des Unkrautdruckes, digitale Ansätze für bessere Entscheidungen zum Herbizideinsatz und zur besseren Integration von nicht-chemischen Unkrautbekämpfungsmaßnahmen begonnen. In einem ersten Monitoring in den Rapsbeständen Luxemburgs wurden relativ weit verbreitete Arten wie Stellaria media, Viola arvensis, Polygonum aviculare sowie Poa annua, Elymus repens, und Apera spica-venti gefunden. Chenopodium album wurde neben den im Frühjahr keimenden Polygonum-Arten in moderater bis hoher Individuenzahl im Mais gefunden. Polygonum convolvulus wurde nach chemischer Bekämpfung in hoher Dichte am Standort Kuborn gefunden, wohingegen C. album schlecht von mechanischen Methoden bekämpft wurde. Alopecurus myosuroides-Pflanzen mit reifen Samen wurden nahezu ausschließlich im Süden Luxemburgs gefunden. Alle 35 bislang getesteten A. myosuroides Sämlingsproben waren resistent gegen Stomp® Aqua (mit dem K1 Hemmstoff Pendimethalin). Im Fall von Sigma® Maxx (mit den ALS-Inhibitoren Iodosulfuron+Mesosulfuron), waren jeweils 2 von 35 Proben sensitiv bzw. moderat resistent. 31 Proben waren resistent gegenüber Sigma® Maxx. 17 von 35 Proben waren sensitiv gegenüber Axial® (mit dem ACC-ase Inhibitor Pinoxaden), während 18 Proben resistent gegenüber Axial® waren.Due to ecotoxicological and environmental reasons, chemical treatments for weed control are under discussion. To help farmers in coping with challenges imposed by restricted herbicide availability, projects on using modified crop rotations for reducing weed pressure, digital approaches for better decision support, and a better integration of non-chemical weeding were initiated. First monitoring programs in winter oilseed rape in Luxembourg offered a preliminary overview about mainly widespread weed species like Stellaria media, Viola arvensis, Polygonum aviculare as well as Poa annua, Elymus repens and Apera spica-venti. Chenopodium album was found in moderate and high numbers in maize, as well as the spring-germinating Polygonum species. Polygonum convolvulus escaped from or re-emerged after the chemical control at location Kuborn, while C. album was poorly controlled by the mechanical treatments. Alopecurus myosuroides plants with mature seeds were almost exclusively found in the South of Luxembourg. All 35 A. myosuroides seedling samples tested so far were resistant towards Stomp® Aqua (containing the microtubule assembly inhibitor pendimethalin). In case of Sigma® Maxx (containing the ALS inhibitors iodosulfuron+mesosulfuron), 2 out of 35 samples were sensitive and moderately resistant, respectively. 31 samples were resistant to Sigma® Maxx. 17 out of 35 samples were sensitive to Axial® (containing the ACC-ase inhibitor pinoxaden), while 18 samples were resistant to Axial®

Catalogue of continental diatoms from Portugal, including the Archipelagos of Azores and Madeira: updated nomenclature, distribution and bibliography

876 p.Catalogue of continental diatoms from Portugal, including the Archipelagos of Azores and Madeira: updated nomenclature, distribution and bibliograph

Catalogue of continental diatoms from Portugal, including the Archipelagos of Azores and Madeira: updated nomenclature, distribution and bibliography

611 p.Catalogue of continental diatoms from Portugal, including the Archipelagos of Azores and Madeira: updated nomenclature, distribution and bibliograph