Effets d'une perturbation anthropique sur les conditions hydrologiques de la langune de Smir (Nord-Ouest, Maroc)

La lagune de Smir a été sujette à un aménagement (construction d'un barrage et d'un port de plaisance) qui a contribué à la modification de son système hydrologique notamment, la disparition de certaines espèces de flore et de faune et la réduction de superficies considérables de cet écosystème.Une caractérisation des eaux de cette lagune a porté sur la mesure pendant le reflux, d'un ensemble de paramètres physico-chimiques. Une méthodologie a été suivie afin d'exprimer de façon cartographique les résultats. De même, des suivis d'une journée ont été réalisés pour les eaux entrantes et sortantes au niveau de deux stations fixes, dans une tentative de comprendre l'action de la marée sur l'hydrologie au sein de la lagune, de cerner les caractéristiques des eaux entrantes dans la lagune et celles sortantes de celle-ci et de suivre l'évolution des différents paramètres physico-chimiques au cours des cycles marégraphiques.L'évolution spatiale des paramètres hydrologiques au niveau de la lagune, se réalise sous forme de gradients entre l'aval et l'amont. Elle est fonction des saisons, de la marée et des apports de l'Oued Smir et du Chenal principal venant des marais. La lagune subit le flux et le reflux de la marée d'un mètre d'amplitude environ. Combinée avec le déficit en eaux douces, la communication permanente avec la mer a eu pour conséquence l'augmentation générale de la salinité dans le plan d'eau lagunaire et dans les marais. Le fonctionnement hydrologique de la lagune de Smir se trouve actuellement régi par les facteurs hydrodynamiques liés à la marée (réguliers) et aux apports d'eaux véhiculés par le chenal des marais (irréguliers), auxquels peuvent être ajoutés des facteurs physiques (évaporation intense), bathymétriques (faible profondeur) et physiologiques (photosynthèse des macrophytes et des phanérogames dans la lagune et dans les marais limitrophes).The Mediterranean Smir lagoon (35°43' N 5°20' W) is located in the extreme west of the Mediterranean basin, northwest of Morocco, 25 km south from the Gibraltar strait. The area of this lagoon is about 3 km2 with a maximum depth of 2.5 m. The bottom is dominated by silty and fine substrates with some sandy zones close to the entrance. The bottom is extensively covered with macrophytes (e.g., Enteromorpha and Ulva) and phanerogams (e.g., Rupia maritima and Zostera noltii). The lagoon receives water from the Smir Wadi but this input has decreased. It also receives fresh water via another channel (the marshes channel) from swamps that lie between the water body and M'diq city. This ecosystem has been subjected to unplanned dam and pleasure port constructions, and these changes led to a modification of the hydrologic system. Currently, this ecosystem communicates with the Kabila harbour (marina) and the sea across a narrow gully and is regularly subjected to tidal movements.This ecosystem, which functioned before as a lake, has been transformed into a coastal lagoon. This lagoon is changing and trends suggest a progressive evolution towards a neutral type lagoon, where water movement is exclusively influenced by the tidal rhythm. The salinity in the lagoon is comparable to sea salinity. This increase in salinity clearly influences the hydrologic conditions, and has altered the composition, structure and functioning of the biotic compartment. The biota has progressively changed and there has been a progressive colonization of halophyte plants within the marsh and a disappearance of fresh water species from the lagoon.The physicochemical parameters (salinity, conductivity, dissolved oxygen, pH, water temperature and sediment temperature) of the lake water were characterized. The methodology used allowed the results to be expressed cartographically. Similarly, the measurements for one day were analyzed for incoming and retreating waters at two stationary points, thus increasing the understanding of tidal action on the lagoon-lake hydrology.The salinity analyses clearly show a mixohalinity and strong spatial and temporal variabilities (9 - 40) within the lagoon. This parameter was influenced by tidal changes, rainfall and sunshine during the summer. The latter contributes to evaporation of lagoon water, which therefore increases salinity. Gradients established between the upstream and downstream regions are a function of tide and season. The salinity distribution is marked by maximum values recorded in the summer and minimum values recorded in the winter. The same evolution scheme evolution is also noticed for conductivity since it is a parameter closely linked to salinity.The lagoon and the main channel waters had higher salinity in the summer (S‰=40) due in part to marine waters that pervaded this channel, and the evaporation of inflow currents. Low salinity aureoles were detected in the Smir Wadi mouth indicating that fresh waters dilute marine waters. Marine waters that enter the Wadi channel by the inflow currents blend with fresh rainfall waters or stagnant saline waters or with groundwater inputs.Two periods were distinguishable based on the surface water temperature; hot summer conditions and cold winter conditions. The continental effect was compensated by the sea buffer effect that played an important role in the regulation of the temperature within the Smir lagoon. During the period of decreasing temperature gradients from the downstream region towards the upstream region (by stretching from sea towards continent), marine waters played a significant role by moderating the freshwater temperatures cooled down from the continent during cold periods (winter and autumn). In contrast, during decreasing temperature gradients from the upstream region towards the downstream region, the oceanic waters cooled the high temperatures of internal lagoon waters resulting from hot seasons (summer and spring). Furthermore, the shallow lagoon depth and the long exposure to sunshine, especially in the summer, resulted in water heating.In addition, the water temperature was influenced by hot marsh channel waters that occupy the upper region and spread with the low tide up to the lagoon entrance. Waters brought by the marsh channel also were distinguishable by high oxygen values, which demonstrate the role played by the swamp vegetation in the oxygenation of these waters. The low oxygen values recorded at the Smir Wadi mouth reflected the effect of suspended elements (turbidity). The Wadi contribution to the oxygen distribution in the lagoon waters was notable as it brings less oxygenated waters because of their strong turbidity.Nevertheless, the lagoon waters showed good dissolved oxygen saturation and no under-saturation was observed during the study period. This relates not only to the permanent exchanges with the sea, but also to the rather remarkable abundance of marsh vegetation and to the development of macrophytes and phanerogams within the lagoon. The dissolved oxygen isovalue distribution curves overlapped remarkably with isotherms, even as the temperature increased, because the entire zone that stretches up to the gully was occupied by a dense meadow. This biomass supplies oxygen to the central zone and can contribute to over-saturation. The lagoon inside was less covered with vegetation and showed comparatively low oxygen values. Besides the photosynthesis activity, the shallow depth and the uninterrupted lagoon waters mixed by the tidal currents explain the over-saturation sometimes observed within lagoon, especially in its downstream region.Variations in pH appeared to be closely linked to dissolved oxygen and water temperature. The three parameters present comparable distribution patterns showing the influence of the marsh waters on the lagoon hydrology. The pH varied between 8.0 and 9.0, demonstrating an elevated alkalinity in some lagoon waters. This alkalinity trend was due to the constant seawater entrance and to the stopping of Smir Wadi fresh water supplies.The sediment temperature measured at 5 cm deep gave insight into different daily and seasonal variations. The temperature of both air and marsh waters was comparatively well reflected in the sediments; the temperature distribution in the sediments overlaps with the water isotherms, with temperature values varying from 14 to 28°C. The inside part of the lagoon showed temperatures widely different from those recorded close to the entrance.The spatial evolution of hydrologic parameters in the lagoon resulted from gradients between the downstream and upstream regions. These gradients are a function of seasons, tide, Smir Wadi inputs and also the main channel coming from the swamps. The lagoon is subjected to high and low tides. In addition to freshwater shortages, the permanent communication with the sea resulted in a general increase of salinity in lagoon waters and marshes. The lagoon hydrologic functioning is currently governed by hydrodynamic factors that are related to the tide (regular) and to the fresh water supplied by the marsh channel (irregular). In addition, physical (intense evaporation), bathymetrical (shallow depth) and physiological (photosynthesis by macrophytes and phanerogams in the lagoon and the neighboring marshes) variables also influence the functioning of the lagoon

Oleoquímica I: Estudios sobre la preparación y la estructura de los jabones de litio.

Lithium stéarate, palmitate, myristate, laurate, caprate and caprylate were prepared by means of fusion method. Elementary analysis and the infrared absorptions spectra of the prepared lithium soaps as well as their X-ray diffractions and the thermogravimetric analyses were carried out. The anhydrous lithium salts of fatty acids with 12 carbon atoms or less showed thermal stability up to ca. 300 ± 78 °C depending on the chain length. On other hand the salts with 14 carbon atoms or more were decomposed at 126 ± 4 °C leading to formation of lithium carbonate. The homologous lithium soaps had very similar crystal structure among them and their metal -to- oxygen bonds were similar for the acyl chains between 8 and 18 carbons. However the angle of inclination of the molecular axes to the basal plane increased with the decreasing of the number of carbon atoms of the fatty acid chain, as determined by X-ray diffraction. In addition, the ionic character of the metal -to- oxygen bond was enhanced with the decrease of the number of carbon atoms as shown by infrared spectroscopy.Se han preparado estearato, palmitato, miristato, laurato, caprato y caprilato de litio por fusión. Se ha realizado el análisis elemental, los espectros de absorción en el infrarrojo y las difracciones de rayos X de los Jabones de litio preparados, además del análisis termogravimétrico de los mismos. Las sales de litio anhidra de los ácidos con 12 átomos de carbono o menos mostraron una estabilidad térmica hasta los 300 ± 78 °C dependiendo de la longitud de la cadena. Por otro lado las sales con 14 átomos de carbono o más se descompusieron a 126 ± 4 °C formándose carbonato de litio. Los jabones homólogos de litio mostraron una estructura cristalina similar, siendo los enlaces metal-oxígeno del mismo tipo para los ácidos grasos de número de átomos de carbono entre 8 y 18. Sin embargo el ángulo de inclinación que forma la molécula con el plano basal aumentó con la disminución del número de átomos de carbono, lo que se observó por difracción de rayos X. Se comprobó por espectroscopia infrarroja la intensificación del carácter iónico del enlace metal-oxígeno al disminuir el número de átomos de carbono

From financial performance to sustainable development: A great evolution and an endless debate

The concept of ‘Performance’ is one of the most used words, both in the academic and professional spheres, due to its importance in all fields. In addition to its very high frequency of use, its definition is polysemous. This paper aims to focus on the surrounding of the performance, by listing several definitions and tracing its evolution over time. This paper also proposes the treatment of performance in all its facets, from the financial one to the global and sustainable one, and by highlighting the complementary aspect of the different approaches of treatment of this concept. To do this, we were interested in articles and books referenced in the Scopus, Cairn, Electre and Google Scholar databases, and we selected the scientific production between 1960 and 2020, which deals with either the definition or the link between the concepts ‘Performance’, ‘CSR’, ‘CSP’ and ‘Sustainable Development’, to synthesize them in this article following a chronological and logical order. This article is intended as a synthetic guide for any researcher or professional interested in the concept of performance, since it traces its evolution and its ramifications through the highlighting of the complementarity and the relevant use of this concept

Determining spatial and temporal scales for management: lessons from whaling

Selection of the appropriate management unit is critical to the conservation of animal populations. Defining such units depends upon knowledge of population structure and upon the timescale being considered. Here, we examine the trajectory of eleven subpopulations of five species of baleen whales to investigate temporal and spatial scales in management. These subpopulations were all extirpated by commercial whaling, and no recovery or repopulation has occurred since. In these cases, time elapsed since commercial extinction ranges from four decades to almost four centuries. We propose that these subpopulations did not recover either because cultural memory of the habitat has been lost, because widespread whaling among adjacent stocks eliminated these as sources for repopulation, and/or because segregation following exploitation produced the abandonment of certain areas. Spatial scales associated with the extirpated subpopulations are frequently smaller than those typically employed in management. Overall, the evidence indicates that: (1) the time frame for management should be at most decadal in scope (i.e., \u3c100 yr) and based on both genetic and nongenetic evidence of population substructure, and (2) at least some stocks should be defined on a smaller spatial scale than they currently are

Contraintes du milieu sur les populations de Donax trunculus L. et Donax venustus Poli du littoral atlantique marocain

Populations of Donax trunculus and Donax venustus were sampled along the Moroccan Atlantic coast from Tanger to Tarfaya (Cape Juby) in 1986 and 1987. All the investigated beaches are surf-exposed and belong to the dissipative system. The geographical distribution of the dominant species D. trunculus appears to be obviously influenced by swell-related hydrodynamics. This phenomenon is controlled by the slope on the nearshore side of a critical 30 m depth, and can be expressed in terms of the distance from the coast of the corresponding isobath. A model of adult density distribution is based on this parameter. When the distance in question is less than 2 km, Donax are absent. The maximal densities observed are on the whole weak and suggest the limiting function of this hydrodynamic instability. Analysis of the geographical distribution of D. venustus also suggests a climatic influence, the occurrence of this species on the shore being correlated with the intensity of the trade winds. The explanation is to be found in the relative stenothermy of a species with subtidal affinity, the temperature range being reduced in these upwelling areas.Les populations de Donax trunculus et Donax venustus sont échantillonnées le long du littoral atlantique marocain de Tanger à Tarfaya (cap Juby) en 1986 et 1987. La répartition géographique de l'espèce dominante D. Vtrunculus apparaît largement influencée par l'hydrodynamisme lié aux houles. Ce phénomène se révèle conditionné par le degré d'inclinaison des fonds subtidaux au niveau de l'avant-côte en deçà d'une profondeur limite correspondant à l'isobathe de 30 m. Un modèle de distribution est établi en fonction de ce paramètre. Au-dessous d'une valeur-seuil de 2 km les plages n'hébergent pas de Donax. Les densités maximales relevées sur l'ensemble des sites restent peu élevées et suggèrent le rôle de «facteur limitant» de l'instabilité hydrodynamique. L'analyse de la distribution de Donax venustus révèle l'intervention du facteur climatique. Cette espèce apparaît uniquement sur les estrans soumis à une nette influence des vents alizés. L'explication peut être attribuée au caractère relativement sténotherme d'une espèce à affinité subtidale, les écarts thermiques étant atténués dans ces secteurs en raison du phénomène d'upwelling

Spatial organisation of macrozoobenthic communities in response to environmental factors in a coastal lagoon of the NW African coast (Merja Zerga, Morocco)

Merja Zerga lagoon, located on the Moroccan Atlantic coast, is a site of international value (Ramsar Site) in terms of its ornithological diversity. However, the lagoon is heavily exploited for its clams and fishes. In an effort to further understanding of lagoon ecosystems, and thus to facilitate the management and conservation of their resources, an ecological survey of its benthic component was carried out. Benthos is a valuable food source for birds, fishes and humans. This work involved identifying the macrozoobenthic communities in the lagoon and assessing their spatial distribution. The study was based on monthly sampling of the intertidal zone and seasonal sampling in subtidal zone, over a one-year period. In the intertidal zone, salinity and median diameter and silt content of the sediment exhibited a gradient extending from the entrance to the inner lagoon, according to tidal flow. Sediment grain size characteristics reflected a gradual decrease of tidal currents from the lagoon entrance towards the inner parts of the lagoon, i.e. silt content increased with distance from the entrance. In the subtidal zone, the tidal currents were fairly strong throughout the lagoon, leading to the presence of coats er sediments than in the intertidal zone. Based on these physical, chemical and substratum characteristics, three communities were identified:, (i) Cerastoderma edule and (ii) Scrobicularia Plana communities were located in both the intertidal and subtidal zones; and (iii) a Tapes decussata community that was only found in the subtidal zone. The assemblages in the subtidal zone were more diverse and the mean abundances of the constituent species were higher than in the intertidal zone, which is an interesting feature for a lagoon environment. Communities were distributed along an ecological gradient, without showing a discontinuity or ecotone. The lagoon functioned like an estuary in which the community structure was controlled by edaphic factors in the intertidal zone, and by the hydrological factors in the subtidal zone.La lagune de Merja Zerga, située sur la côte atlantique marocaine, présente un intérêt international (Site Ramsar) pour sa diversité ornithologique. Toutefois, elle est très exploitée pour ses palourdes et ses poissons. Dans le but de bien connaître le fonctionnement de l’écosystème lagunaire pour aider à sa gestion et la conservation de ses ressources, un suivi écologique a été mené sur l’écosystème benthique, compartiment–proie essentiel pour les oiseaux et pour l’homme. Ce travail vise à identifier les communautés macrozoobenthiques et à préciser leur répartition spatiale. L’étude est basée sur un échantillonnage mensuel de la zone intertidale et sur des prélèvements saisonniers de la zone subtidale, sur une période d’une année. En zone intertidale, la salinité, la médiane granulométrique et les taux de pélites présentent des gradients allant de l’ouverture vers l’intérieur de la lagune, en suivant le flot engendré par la marée. Les caractéristiques granulométriques traduisent l’affaiblissement progressif des courants de marée de l’aval à l’amont, i.e. les teneurs de pélites augmentent en s’éloignant de l’ouverture. En zone subtidale, les courants de marée restent assez forts tout au long de la lagune, ce qui conduit à la présence de sédiments plus grossiers qu’en zone intertidale. Selon ce schéma de structure physico-chimique et édaphique, trois communautés sont identifiées : les communautés à (i) Cerastoderma edule et à (ii) Scrobicularia plana, localisées à la fois en zones intertidale et subtidale et (iii) une communauté à Tapes decussata, présente uniquement en zone subtidale. Les assemblages sont plus diversifiés en zone subtidale et les abondances moyennes des espèces y sont plus fortes qu’en zone intertidale, ce qui constitue une originalité pour un milieu lagunaire. Les communautés se distribuent le long d’un gradient écologique sans stade de transition ou écotone. La lagune fonctionne selon un modèle estuarien dans lequel la structure des communautés est contrôlée par les facteurs édaphiques en zone intertidale et par les facteurs hydrologiques en zone subtidale

Thermography for characterization of soil water repellency at larger spatial scales

Soil water repellency (SWR) is natural phenomenon occurring in soils throughout the world. It is a surface property that reduces the attraction of soil for water. Measurement of soil water repellency is done at the point scale; however its role in the environment often evaluated at the landscape scale. This disparity is due to limitation in the scale of measurements. The objective of this study is improving characterization of soil water repellency at larger spatial scales through thermography. Thermography shows promise to track the temporal and spatial dynamics of soil water repellency. In a lab experiments, it has been demonstrated that there was a huge potential for thermal imaging in SWR mapping to distinguish between highly repellent areas and wettable ones. However, the proposed technique had a number of limitations. One major drawback was its poor performance to detect low SWR areas which is often present in the environment. Another issue is the induction of a temperature gradient to reveal SWR, while also changing the surface properties of SWR. A strategy to help in distinguishing the differences in SWR is to assess the energy balance and evaporative fluxes of the soil surface. A lab calibration experiment will be presented to distinguish the link between thermal regime, evaporative flux, soil water content and soil water repellency. A field survey using thermography to map soil water repellency at larger spatial scales will improve understanding of how SWR can affect hydrologic processes at larger scales. Through this innovative technique, we will be able to predict and model the behaviour of water dynamics in water repellent soil and therefore improve management of water and soil resources. We will further understand the role soil water repellency plays for ecosystem services

Behavioural similarities in different species of sandhoppers inhabiting transient environments

On sandy shores, physical constraints are expected to be the main driving force in defining both the presence and behaviour of the suite of resident species. We tested the orientation of sandhoppers found on the Atlantic shores of Morocco, on two banks of an ephemeral river mouth, which presented different ecological characteristics. Replicates were carried out before and after summer, when a seasonal change of both natural and human-driven environmental features is expected, due to increasing temperatures, dryness and frequency of tourists. These features affected the two wadi banks differently, providing a natural set of environmental conditions to be tested. Three species were found at the site, each with a different distribution on the two banks: Africorchestia spinifera was found on both banks; Talorchestia brito on the left bank only and Talitrus saltator on the right bank only. Although the occurrence of sandhoppers decreased after summer, the multiple regression models developed from the orientation datasets and selected with the Akaike Information Criterion retained the same variables to explain the orientation of the individuals tested: environment (the river bank); intrinsic (the sex); and immediate (the time of the day) one. This highlighted the environment role, including human pressures, in shaping: a) the occurrence of sandhopper species; and b) a common behavioural strategy to cope with environmental changes, disregarding the species. The occurrence and behaviour of talitrids were thus at least partly independent of one another. These experiments also provided the first behavioural data for the species A. spinifera and its comparison with other supralittoral amphipod species