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Auteur Marc Ventura |
Documents disponibles écrits par cet auteur (6)
Affiner la rechercheAttenuation of ultraviolet radiation in mountain lakes: Factors controlling the among- and within-lake variability / Isabelle Laurion in Limnology and oceanography, 45 (6) (2000)
Titre : Attenuation of ultraviolet radiation in mountain lakes: Factors controlling the among- and within-lake variability Type de document : Imprimé Auteurs : Isabelle Laurion ; Marc Ventura ; Jordi Catalán ; Roland Psenner (1950-) ; Ruben Sommaruga Année de publication : 2000 Article en page(s) : 1274-1288 Langues : Anglais (eng) Catégories : [Thématique] Enjeux de conservation des lacs d'altitude Résumé : High-altitude lakes are exposed to high fluence rates of solar ultraviolet radiation (UVR; 29–400 nm) and contain low concentrations of dissolved organic carbon (DOC). While in most lowland lakes, DOC can be used to predict UV transparency with sufficient accuracy, current models fail to estimate UVR in clear alpine lakes. In these lakes, phytoplankton may contribute significantly to the UV attenuation either as particles or as a source of chromophoric dissolved organic matter (CDOM) with distinctive properties. We investigated a series of 26 lakes in the Alps and Pyrenees, situated at elevations ranging from 422 to 2,799 m above sea level and having DOC concentrations ranging from 0.2 to 3.5 mg L−1. CDOM, as measured by the absorptivity of filtered lake water, explained most of the variability in the attenuation of underwater UVR among lakes (r2 = 0.94, P < 0.001). However, within-lake variation in the UV attenuation revealed a significant contribution from phytoplankton in deeper waters (UV attenuation increasing with chlorophyll a concentration; r2 = 0.97, P = 0.002), only apparent when DOC concentrations were low (∼0.3 mg L−1). The DOC-specific absorptivity (ag*) was also important for characterizing the optical conditions in this series of lakes. Epilimnetic values of ag* were significantly lower in lakes located at high elevations (with low allochthonous CDOM inputs from the catchment), compared to lakes surrounded by trees and meadows. Moreover, ag* was generally lower in surface waters than in deeper water layers, suggesting the influence of photobleaching on UV transparency. The slope S of the exponential regression between CDOM absorptivity and wavelength did not show clear patterns, such as found in marine systems, and often presented lower values in the epilimnetic waters (in association with lower ag*). Collectively, our results suggest that in transparent alpine lakes, the dynamics of the CDOM pool and phytoplankton production will have a strong effect on temporal changes in UV underwater attenuation. Lien pérenne : DOI : 10.4319/lo.2000.45.6.1274
in Limnology and oceanography > 45 (6) (2000) . - 1274-1288Laurion, I., Ventura, M., Catalán, J., Psenner, R., Sommaruga, R. 2000. Attenuation of ultraviolet radiation in mountain lakes: Factors controlling the among- and within-lake variability. Limnology and oceanography, 45(6): 1274-1288.Documents numériques
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Article (2000)URL
Titre : Biodiversité des lacs des Pyrénées : améliorer les connaissances pour une gestion conservatoire Type de document : Imprimé Auteurs : François Prud'homme ; Frédéric Blanc ; Nicolas Gouix ; Victor Osorio ; Sylvain Rollet ; Marc Ventura ; Olivier Jupille Année de publication : 2020 Article en page(s) : 35-55 Langues : Français (fre) Catégories : [Thématique] Biodiversité
[Thématique] Eaux douces
[Géographique] PyrénéesRésumé : Les lacs pyrénéens hébergent une biodiversité spécifique et cependant mal connue notamment en raison des conditions d’accès (marche d’approche et milieu aquatique). Des investigations étaient nécessaires pour que des programmes de conservation et/ou de gestion sur la faune et la flore des lacs puissent être envisagés sur la base d’une connaissance plus complète, robuste et partagée. Bien que situés en tête de bassin, les lacs de haute montagne restent soumis à différentes pressions anthropiques (hydroélectricité, pastoralisme, pollution atmosphérique, introduction de poissons…). Ils sont également particulièrement recherchés et fréquentés pour diverses activités touristiques, sportives ou de loisirs. L'activité halieutique est ainsi très présente sur la chaîne pyrénéenne. Les lacs de haute montagne, naturellement apiscicoles dans la grande majorité des cas, ont fait l'objet d'introductions de poissons (salmonidés, vairons) particulièrement depuis la fin du XIXe. Ces empoissonnements n'ont pas été sans conséquence sur le fonctionnement et la richesse de ces écosystèmes, devenant de nos jours l'une des pires menaces. Les lacs de haute montagne constituent aussi des milieux privilégiés pour mettre en place un réseau de suivi standardisé du changement climatique et de la biodiversité à l’échelle de la chaîne pyrénéenne. Trois années d’études partenariales autour d’un projet transfrontalier (programme Green : Gestion et mise en réseau des espaces naturels) ont permis de s’appuyer sur un réseau de 36 lacs dans 3 pays (Espagne, Andorre et France) sur lesquels ont été réalisés des inventaires standardisés. Ceux-ci ont porté sur la flore (plantes vasculaires, characées et bryophytes), la faune (mammifères semi-aquatiques, amphibiens, et certains groupes d’insectes) ainsi que des données environnementales (bathymétrie, qualité de l’eau, structure des berges…). Les inventaires ont donné lieu à la production d’une grande quantité de données naturalistes inédites. Ces données permettent d’esquisser des premières synthèses pyrénéennes et de dresser un état des lieux de la biodiversité lacustre des sites retenus. Elles permettront aux gestionnaires de faire des choix éclairés quant aux sites à restaurer ou conserver et donc de définir une stratégie spécifiquement dédiée à la gestion des lacs de haute montagne. A titre d’exemple, une action de désempoissonnement a été entreprise en 2019 en zone cœur du Parc national des Pyrénées en vue d’un retour à un état apiscicole des lacs d’Araillé. Une des ambitions de ce travail est de remettre la biodiversité des lacs de montagne au cœur des enjeux de conservation des espaces protégés, du réseau Natura 2000 et de la stratégie pyrénéenne de valorisation de la biodiversité. Lien pérenne : DOI : 10.4000/dynenviron.3835
in Dynamiques environnementales > 45 (2020) . - 35-55Prud'homme, F., Blanc, F., Gouix, N., Osorio, V., Rollet, S., Ventura, M., Jupille, O. 2020. Biodiversité des lacs des Pyrénées : améliorer les connaissances pour une gestion conservatoire. Dynamiques environnementales, 45: 35-55.Exemplaires (1)
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Article (2020)URL
Titre : High mountain lakes: extreme habitats and witnesses of environmental changes Type de document : Imprimé Auteurs : Jordi Catalán ; Lluis Camarero ; Marisol Felip ; Sergi Pla ; Marc Ventura ; Teresa Buchaca ; Frederic Bartumeus ; Guillermo de Mendoza ; Alexandre Miró ; Emilio O Casamayor ; Juan Manuel Medina-Sánchez ; Montserrat Bacardit ; Maddi Altuna ; Mireia Bartrons ; Daniel Díaz de Quijano Année de publication : 2006 Article en page(s) : 35 Langues : Français (fre) Catégories : [Thématique] Changement climatique
[Thématique] Enjeux de conservation des lacs d'altitude
[Thématique] Lac d'altitudeRésumé : High mountain lakes offer research opportunities beyond what could be expected from their quantitative relevance in the Earth system. In this article we present a brief summary of the research carried out in the lakes of the Pyrenees in the last twenty years by the group of limnology of the Centre for High Mountain Research (CRAM) of the University of Barcelona. The studies can be included in three main topics: life in extreme conditions, catchment-lake relationships and environmental changes. Lien pérenne : DOI : 10.23818/limn.25.38
in Limnética > 25 (1-2) (June 2006) . - 35Catalán, J., Camarero, L., Felip, M., Pla, S., Ventura, M., Buchaca, T., Bartumeus, F., Mendoza, G.d., Miró, A., Casamayor, E.O., Medina-Sánchez, J.M., Bacardit, M., Altuna, M., Bartrons, M., de Quijano, D.D. 2006. High mountain lakes: extreme habitats and witnesses of environmental changes. Limnética, 25(1-2): 35.Documents numériques
Article (2006)URL
Titre : Introduced fish in Pyrenean high mountain lakes : impact on amphibians and other organisms, and conservation implications Type de document : Imprimé Auteurs : Alexandre Miró ; Marc Ventura Année de publication : 2020 Article en page(s) : 283-297 Langues : Anglais (eng) Catégories : [Thématique] Enjeux de conservation des lacs d'altitude
[Géographique] PyrénéesRésumé : Pyrenean high mountain lakes are naturally fishless due to hydrographic barriers that have prevented the natural colonisation of fish species from lower elevation streams. However, there have been numerous introductions of trout and minnows to such ecosystems, either in historical and recent periods. Trout and minnow introductions can cause large ecological problems and ecosystem changes in high mountain lakes, since both taxa occupy the top of a lake’s food web. The study had two objectives. First, we wanted to investigate which particular anthropogenic and environmental factors best explained fish presence in the Pyrenean lakes. For that purpose we collected data on trout and minnow occurrence from 520 high mountain lakes >0.5 ha in the southern Pyrenees. The second objective was to investigate the effect of introduced fish on several groups of organisms such as amphibians, conspicuous macroinvertebrates, planktonic crustaceans and littoral epilithic community. For that purpose we sampled 1736 lakes and ponds at different levels of intensity. The distribution of Salmo trutta in the lakes of the southern slopes of the Pyrenees was best explained by both anthropogenic factors and lake characteristics, while only anthropogenic factors linked to recreational fishing were associated with the distribution of the exotic trout Salvelinus fontinalis and Oncorhynchus mykiss. In the case of minnow occurrence, previous presence of trout in the lake was the most explanative variable, confirming its association with its use as live-bait in recreational fishing. Fish presence was linked with the disappearance of most amphibian species. Despite fish had a high local effect, at Pyrenean range scale, western-eastern patterns of some environmental variables were the main drivers of amphibian species distribution. Minnows also showed a sizeable impact on the pelagic habitat, reducing the occurrence of some crustacean zooplankton species that appeared to be unaffected by trout. In addition, we confirmed the presence of a littoral trophic cascade that defines most of the characteristics of the littoral epilithon of Pyrenean high mountain lakes and ponds through fish predation of tadpoles and hence, by a drastic reduction of grazing activity. Lien pérenne : DOI : 10.23818/limn.39.19
in Limnética > 39 (1) (2020) . - 283-297Miró, A., Ventura, M. 2020. Introduced fish in Pyrenean high mountain lakes : impact on amphibians and other organisms, and conservation implications. Limnética, 39(1): 283-297.Documents numériques
Article (2020)URL
Titre : Non-native minnows threaten quillwort populations in high mountain shallow lakes Type de document : Imprimé Auteurs : Esperança Gacia i Passola ; Teresa Buchaca ; Nayeli Bernal-Mendoza ; Ibor Sabás ; Enric Ballesteros (1958-) ; Marc Ventura Année de publication : 2018 Article en page(s) : 329 Langues : Français (fre) Catégories : [Thématique] Enjeux de conservation des lacs d'altitude Résumé : Submersed aquatic plants are a key component of shallow, clear water lakes contributing to primary production and water quality. High mountain lakes are naturally fishless although invasive trout and most recently minnows have been introduced causing a major impact on fauna richness. The Pyrenean high mountain range has preserved soft-water oligotrophic boreal isoetids in their southern limit of distribution but the recent fish introduction is a potential factor of stress that needs to be addressed. We here work under the hypothesis that due to contrasting ecological features, trout will not be heavily affecting quillwort populations while minnows will have a stronger effect on zooplankton and zoobenthos that will promote algal growth and reduce light availability for the underwater meadows. Ten Pyrenean shallow lakes representative of three scenarios -fishless, with trout and with minnows-, were sampled for meadow structure, water column and benthic environment characterization in mid-summer 2015 and 2016. Quillwort biomass allocation (above vs. belowground), epiphytic load, and composition of the algal community (abundant cyanobacteria) differed in the presence of minnows. In trout lakes biomass allocation and epiphytic load were average and the algal community composed by chlorophytes and diatoms as in fishless lakes. Biomass ratio was close to thresholds of negative buoyancy in minnow lakes indicating that meadows were at risk of uprooting and consequent de-vegetation. Total and soluble carbohydrates were lower and the sporangia contained significantly less reserves to constrain growth and expansion in the presence of minnows. Lake scenarios were coupled to physicochemical differences with low light, high phosphorus and Chl-a (mesotrophia) in minnow lakes, while trout and fishless lakes remained oligotrophic. This is the first study assessing the impact of non-native fish on soft-water isoetids from mountain lakes and shows that minnows are a major threat to quillworts. The impaired light environment (from epiphytic algal overgrow and water column Chl-a) entails consequent regression (i.e., no recruitment) and de-vegetation (uprooting) of the meadows. Since soft-water oligotrophic mountain lakes are protected under the Habitats Directive, some action needs to be urgently implemented not only to preserve quillworts but to the overall ecological integrity of the lakes. Lien pérenne : DOI : 10.3389/fpls.2018.00329
in Frontiers in plant sience > 9 (2018) . - 329Gacia i Passola, E., Buchaca, T., Bernal-Mendoza, N., Sabás, I., Ballesteros, E., Ventura, M. 2018. Non-native minnows threaten quillwort populations in high mountain shallow lakes. Frontiers in plant sience, 9: 329.Documents numériques
Article (2018)URL
