Interactions zooplancton-poissons dans une retenue oligotrophe de mise en eau récente (Ste-Croix, Provence, France)

Les peuplements zooplanctoniques et piscicoles de la retenue de Sainte-Croix (lac oligotrophe profond) ont été suivis de la mise en eau (1974) à 1986.La phase initiale de colonisation (1974-1975), caractérisée par le calanide Acanthodiaptomus denticornis et la dominance des espèces piscicoles peuplant antérieurement le Verdon lotique (Barbus fluvatilis, Leuciscus cephalus) a été de courte durée. Par la suite, les cladocères sont restés dominants avec cependant de profondes modifications dans la structure du peuplement. En 1977-78, Daphnia longispina était dominante tout au long de l'année (76 %). Plus récemment, cette espèce ne représentait plus que 34 %. des effectifs (1983-84), puis 24 % (1985-1986). La situation actuelle est caractérisée par la présence de Diaphanosoma brachyurum en été et l'abondance des petites formes (bosmines).L'ichtyofaune s'est elle aussi modifiée avec, notamment, une importante population d'ablette (Alburnus cluburnus), exploitant la zone pélagique. Son régime alimentaire est largement zooplanctonophage mais inclut mollusques et insectes lorsqu'elle est capturée en zone littorale.Cette augmentation de la pression de prédation a entraîné un net déplacement du spectre des tailles du zooplancton vers tes classes inférieures à 0,8 mm en 1986 (82 %) alors que les grandes formes ( > à 1 mm) représentaient 60 % des effectifs en 1977-78. Les densités de D. longispina et D. brachyurum décroissent rapidement entre 1983 et 1986.Les conséquences de cette prédation sélective sont discutées (évolution prévisible du système) ainsi que les causes pouvant expliquer l'absence de régulation efficace (densité-dépendance) dans un tel système prédateur-proie.The aim of this study was to identify relationships between changes that occurred, from 1974 to 1986, both in the limnetic zooplankton and the fish communities of the large reservoir of Sainte-Croix (Southern France).This reservoir (figure 1) is characterized by a capacity of 767 hm3 and a long average renewal period (280 days). It was filled up in 1974. Changes in levels can attain 16 m, especially in winter. During summer, the lake is clearly stratified : surface mater temperatures are about 22-250°C whereas waters below the thermocline are cooler ( < 10° C) but well oxygenated (more than 50 % saturation). According to the mean annual total phosphorus (19 mg/m3) and chlorophyll a (ranging from 0.5 to 2 mg/m3), the lake is oligotrophic.The zooplankton was collected with a Clarke-Bumpus devise sampler (125 µm mesh-size) during both the 1974-1978 and the 1983-1984 periods. More recently (1985-1986), vertical hauls of zooplankton were made with a 50 µm mesh-size aperture net. Only relative abundance of large species (excluding small rotifers) have been taken into account for comparisons between different periods (figure 2). For the last four years (1983-1986), a set of data on filtration efficiency and comparison between sampling methods provides information concerning the evolution of annual mean densities of zooplankton species (figure 3).Successive inventories of the fish species were made in 1976, 1977, 1984 and 1987 at the same location with 15 mm, 27 mm and 50 mm mesh-size nets respectively. Figure 1 shows that abundant autochtonous species (Chondrostoma chondrostoma, Barbus fluviatilis) during the first period (1976-1977) are now relatively scarce, whereas the roach (Rutilus rutilus), an introduced species, is now largely dominant. Likewise, the relative abundance of the bleak, Alburnus alburnus, also increased, especially during the last period (1984-1987). Only this last species was caught by fine mesh-size nets in the pelagic epilimnion. Adults fed mostly on zooplankton but also took more molluscs in the littoral area (stomach analysis).In 1974, one year after an overflow, the calanoid Acanthodiaptomus denticornis represented the majority of zooplankton collected but it disappeared quickly. Since 1976, cladocerans are largely dominant. General evolutive trends show a decrease in relative abundance of Daphnia longispina from 1978 to 1986 whereas Diaphanosoma brachyurum have been recorded since 1983. Quantitative data (figure 3), available for the fast 4 years (1983-1986) show that the population densities of both these two large cladoceran and cyclopoïd species (mainly Macrocyclops albius) declined radically. On the other hand, small species such as Bosmina longirostris, Bosmina coregoni and Asplancha priodonta exhibited the same population densities throughout the fast period. Comparisons of phytoplankton community structure from 1982 to 1986 do not show signicative trends. Thus, variations in resource abundance cannot explain the long-term evolution of zooplankton communities.By comparing the mean annual length frequency distributions of zooplankton in 1977-78 and 1986 (figure 4), a marked decline of large bodied forms is seen. The individuals larger than 1.0 mm represented 60 % of total organisms in 1977-73 against 14.5 % in 1986. Mean annual lenghts were 0.8 mm in 1977-78 and 0.3 mm in 1986. These results are in good agreement with BROOKS and DODSON hypothesis that planktivorous fish can have a profound effect on zooplankton community taxonomics and size structure. They show that the control of structure and abundance of zooplankton by fish predation in new man-made lakes is a reality.Most fish are general predators. As demonstrated by MURDOCH and BENCE (1987), this can explain the instability of the coupled predator-prey system in the pelagic portion of Sainte-Croix reservoir because of : i) the capacity of the bleak to use fat reserves and to change its diet when large zooplankton prey density is too low, ii) the generation time of the predator is much longer than that of planktonic preys. Thus, the classical density-dependence mechanisms do not stabilize the predator-prey system and the main planktonic prey tend to disappear (D. longispina, in our case).Nevertheless, some potentially stabilizing mechanisms could interfere in the system before the local extinction of the prey : compensatory responses by the prey and significant changes in the fish community. There is reason to consider :1) The existence of refuges in space. Vertical size distribution of D. longispina (unpublished data) show that there is a strong vertical size gradient during daylight hours. Larger-bodied reproductive forms (longer than 1 mm) are only present in the deeper layers (20-30 m) whereas, during the night all the organises migrate to the superficial layer.2) The existence of refuge in time. In the past (1976-1978), D. longispina was dominant all year around. More recently (1983-1986), population densities were high only in spring (figure 5). From April to June, bleaks tend to assemble in the littoral zone for reproduction.3) An increase in the bleak mortality rate due to a recent development of large predator populations, such as Esox esox, could permit a reduction or, at least, a stabilization of the bleak population growth rate

Spatial Variation in Density and Total Size Estimates in Fragmented Primate Populations: The Golden-Crowned Sifaka (Propithecus tattersalli)

The golden-crowned sifaka (Propithecus tattersalli) is an endangered lemur species found only in the Daraina region, a very restricted area in north-eastern Madagascar. Its forest habitat is highly fragmented and expected to suffer from significant changes in the near future. The species is poorly known and only one census study, carried out in 2000, has ever been published. It is thus crucial to update the conservation status of the golden-crowned sifaka. before major anthropogenic environmental changes take place. Using the line-transect approach, we estimated the species density in the main forest fragments located in both the peripheral and central parts of the distribution range, including both protected and unprotected areas. In parallel, we tried to determine whether an edge effect could be detected by comparing densities at different distances from the forest edges. We found important variation of sifaka densities among forest fragments. The total species abundance is thus difficult to determine, but we estimated that it is likely to be over 18,000, two to three times higher than previously thought. However, our data also suggested that most P. tattersalli live in forests located in the central part of the distribution range and that the estimated densities in the central part were high (> 80 individuals/km(2)). Two forest fragments, found to host a large part of the total population, are currently outside the managed area and their incorporation to the managed area is strongly recommended. Lastly, as expected for a folivorous and not heavily hunted species, our results are consistent with the hypothesis that this species does not experience a clear edge effect, at least during the first half of the dry season. This could be due to a high resiliency to habitat fragmentation or to the fact that fragmentation has been going on for some time

Production primaire et relations trophiques chez les invertébrés des communautés halophiles de Camargue

Les biomasses végétales mesurées dans les zones émergées de la sansouire camarguaise sont relativement élevées dans le Sali cornietum fruticosae, de l’ordre de 3 kg de matière sèche par m2 alors qu’elles n’atteignent que 0,4 kg/m2 dans Y Arthrocnemetum. La production primaire annuelle du S. fruticosae se situe entre 0,5 et 1 kg de matière sèche par m2, soit du même ordre que celle d’un peuplement à Quercus ilex étudié sous le même climat. Elle est réalisée pour l’essentiel en trois mois, de mai à juillet. Ensuite l’abaissement de la nappe aquifère, conséquence de la forte évapo ration estivale, se traduit par une chute du potentiel hydrique et par une régulation efficace de la transpiration. L’étude des niveaux de consommation chez les Invertébrés terrestres montre, qu’en dehors de périodes exceptionnelles de pullulation des chenilles de deux espèces de microlépidoptères, la forte production primaire de S. fruticosae n’est pas utilisée directement. Les détritivores (Coléoptères, Collemboles) et les décomposeurs jouent un rôle essentiel. Dans les zones à submersion temporaire l’abondance des débris végétaux desséchés pendant l’été qui s’ajoute à la production alguale pendant l’inondation hivernale permet la pullulation des Crustacés planctoniques, en particulier celle des Copépodes Cala nides filtreurs dont plusieurs espèces de tailles différentes peuvent proliférer ensemble. Ces populations de Crustacés ainsi que les larves aquatiques d’insectes procurent lors de l’assèchement une nourriture abondante pour la communauté ripicole où les Coléoptères Carabiques sont bien représentés.The above-ground plant biomass in the emerged zones of the Camargue “ sansouire ” is relatively high in Salicornietum fruticosae, about 3 kg of dry matter per square metre, whereas it only reaches 0.4 kg/m2 in Arthrocnemetum. The above-ground annual primary production of Salicornietum fruticosae ranges from 0.5 to 1.0 kg/m2/year, which is approximately equal to that of Quercus ilex stands in the same climate. Production essentially takes place during a three month period from May to July. Afterwards the lowering of the water table resulting from the high level of evaporation during the summer is marked by a decrease in water potential and by an efficient regulation of transpiration. Aside from exceptional outbreaks of caterpillars of two species of microlepidoptera, the primary production of Salicornia is not used by primary consumers, but by detritus feeders (beetles and springt ails) and decomposers. In the areas temporarily flooded, algal production during winter flooding and the accumulation of dried plant debris in summer, allow planktonic Crustacea, Calanoid Copepods particularly, to reach high population densities. These Copepods, together with the larvae of aquatic insects, provide an abundant food for Carabid beetles and other riparian invertebrates when water recedes and the “ sansouire ” dries out

The benefits of participatory methodologies to develop effective community dialogue in the context of a microbicide trial feasibility study in Mwanza, Tanzania

BACKGROUND: As part of a microbicide trial feasibility study among women at high-risk of HIV and sexually transmitted infections in Mwanza City, northern Tanzania we used participatory research tools to facilitate open dialogue and partnership between researchers and study participants. METHODS: A mobile community-based sexual & reproductive health service was established in ten city wards. Wards were divided into seventy-eight geographical clusters and representatives at cluster and ward level elected in a process facilitated by the projects Community Liaison Officer. A city-level Community Advisory Committee (CAC) with representatives from each ward was established. Workshops and community meetings at ward and city-level were conducted to explore project-related concerns using tools adapted from participatory learning and action techniques such as listing, scoring, ranking, chapatti diagrams and pair-wise matrices. RESULTS: Key issues identified included beliefs that blood specimens were being sold for witchcraft purposes; worries about specula not being clean; inadequacy of transport allowances; and delays in reporting laboratory test results to participants. To date, the project has responded by inviting members of the CAC to visit the laboratory to observe how blood and genital specimens are prepared; demonstrated the use of the autoclave to community representatives; raised reimbursement levels; introduced HIV rapid testing in the clinic; and streamlined laboratory reporting procedures. CONCLUSIONS: Participatory techniques were instrumental in promoting meaningful dialogue between the research team, study participants and community representatives in Mwanza, allowing researchers and community representatives to gain a shared understanding of project-related priority areas for intervention

Transcribing "Le Pèlerinage de Damoiselle Sapience": Scholarly Editing Covid19-Style

This article describes a methodological experiment conducted during the 13th Annual (Virtual) Schoenberg Symposium on Manuscript Studies in the Digital Age, hosted by the University of Pennsylvania, November 18–20, 2020. The experiment consisted of a “relay style” event in which three teams transcribed, revised, and prepared for submission to this journal a full edition of the “Le Pèlerinage de Damoiselle Sapience” and other texts from UPenn Ms Codex 660, ff. 86r–95v within the three-day timespan of the conference. The project used methods typical of crowdsourcing and drew participants from all over the world and from all different stages of their careers. After one group completed its work, the results were passed into the hands of the next. The final result—in the form of a finished manuscript edition, ready for submission to Digital Medievalist—was presented on the last day of the conference. The main purpose of this experiment was to demonstrate how the work of the transcriber and editor might be structured as a short-term digital event that relied wholly on virtual interactions with both the source materials and among collaborators. This method also reveals the positive aspects of the many challenges posed by working simultaneously, remotely, and globally

Étude biologique et biométrique du Copepode Mixodiaptomus kupelwieseri en Camargue

Une étude biométrique a été entreprise afin de comparer le Diaptomide Mixodiaptomus kupelwieseri récolté en Camargue avec deux formes différentes de ce même Copépode, décrites en Italie. En Camargue, les deux formes ont été trouvées, à la même époque, dans la même station. Elles ont la valeur de phénotypes résultant de l'influence de la température sur le développement. Le cycle biologique a été établi en Camargue à partir du comptage des différents stades évolutifs; il comporte une seule génération, qui prolifère, en hiver, dans une intervalle de températures basses favorables

Spatial distribution of aquatic macrophytes in the recent reservoir of Ste Croix, Provence, France.

Investigations on horizontal and vertical distribution of aquatic vegetation have been carried out in the regulated lake Sainte Croix from 1985 to 1987. This reservoir, being filled in 1974, has been recently colonized by submersed vegetation. Mac- rophyte data have been collected by using direct observations, echosoundings and grapnel sampling. Two remarkable macroalgae (Tolypella glomerata, Charophyta from temporary water bodies with high alkalinity, and Vaucheria nicholsii, Xanthophyta less known in Europe) and six cosmopolitan phanerogams typical of alkaline waters were recorded in the littoral zone, especially in the bays of Bauduen, Les Salles and Moustiers. Macroalgae reached a maximum growth during spring. Phanerogams developed the most in summer. Myriophyllum spicatum was the dominant species in the whole lake, being associated with Potamogeton crispus in the bay of Moustiers and P nodosus in the bays of Les Salles and Bauduen. Macrophyte depth ranged from 1.9 to 11.3 m. Mean depth was 4.4 m for all the species, varying from 3.5 m (Potamogeton pusillus) to 5.5 m (K nicholsii). The capacity of several predictive models to predict the depth distribution of macrophytes in relation to transparency (Secchi disc) and water level fluctuations is discussed. The best estimation occurs with a model based on mean annual regulation level. Some other environmental parametres, such as nutrient-rich inflows, particularly from sewage supplies, may explain the clustered vegetation communities in some localized stations

Le cycle biologique de Cyclops vicinus vicinus (Copepoda, Cyclopoida) dans la retenue de Serre-Ponçon (Hautes-Alpes)

L'étude du cycle biologique de Cyclops vicinus vicinus à trois stations du réservoir de Serre-Ponçon révèle l'existence d'une hétérogénéité du milieu, tant au niveau des effectifs que du nombre de générations annuelles. Les variations observées s'expliquent par des phases de vie latente (diapause ou quiescence) dont le déterminisme est discuté

CONTRIBUTION A L'ÉTUDE ÉCOLOGIQUE DE LA CORSEI. — LES COPÉPODES DES EAUX STAGNANTES

International audienc

Factors influencing individuals attitudes toward voluntary active euthanasia and physician assisted suicide

Issues of right to life, as well as death have surfaced as topics of hot debate. In particular, questions about when and if individuals have the right to end their own lives have emerged and gained considerable attention as health policy issues having the potential to affect all Americans.. The purpose of this study was to identify the factors that are most likely to influence an individual's decision to support or not support voluntary active euthanasia (VAE) and physician assisted suicide (PAS) in specific medical situations. This study also examined the differences in medical vignettes by various demographic and attitudinal factors. Data were collected from a sample of classified staff members at two institutions of higher learning in Oregon. A survey was used to collect all data. Paired sample T-tests, stepwise multiple regression analysis and repeated measures multiple analysis of variance (MANOVA) were used to analyze the data. Based on survey results, there were significant differences in attitudes toward PAS and VAE for each medical vignette. Religious beliefs, fear of dependency, and fear of death were the most powerful predictors of individual support for PAS in each medical situation. In the case of VAE, there were differences in support on each medical situation in terms of the most powerful predictors: fear of dependency and religious beliefs for the cancer vignette, fear of dependency, religious beliefs, and age for the ALS vignette, and religious beliefs and fear of dependency for the paralysis vignette. The repeated measures MANOVA revealed that in general, the older the individual was, the less likely they were to support PAS or VAE. However, women over age 66 in this study were more likely to support VAE than were the males age 66 and over. Males in the 51-65 year old category were more supportive of VAE than females in this age category. Also, those who were more fearful of death were more likely to have a higher level of support for VAE. In all three vignettes (Cancer, Amyotrophic lateral sclerosis (ALS), and paralysis) for both PAS and VAE, there was a significantly different level of support measured on a seven point Likert scale