Eutrophication remains a major stress for freshwater biodiversity. Its deleterious consequences on biodiversity are well documented for large waterbodies. However, the impact of eutrophication may ...differ in smaller waterbodies, such as ponds and small lakes, which generally support naturally high levels of nutrients in lowlands. Furthermore, this response could depend on the scale considered, from local (individual waterbody, alpha diversity) to regional (the network of waterbodies, gamma diversity). It is also unclear whether the richness of threatened species responds in the same way as the richness of the whole assemblage. The present study investigates local‐ and regional‐scale consequences of eutrophication on taxonomic richness (all taxa) and conservation value (threatened taxa) in temperate lowland small waterbodies. Five taxonomic groups were investigated: macrophytes, gastropods, water beetles, adult dragonflies and amphibians, in a set of natural waterbodies and a set of enriched waterbodies covering a large nutrient gradient from mesotrophic to hypertrophic conditions. Globally, our study did not reveal consistent, systematic responses to eutrophication. For macrophytes, the richness and conservation value suffered from eutrophication at both local and regional scales. In contrast, for amphibians and gastropods, eutrophication did not impair biodiversity at the local nor the regional scale. Dragonflies and water beetles showed intermediate situations, with an impairment by eutrophication varying according to the type of waterbodies considered. At the regional scale, each trophic status, even the nutrient richest, brought an original contribution to biodiversity. Synthesis and applications. The management of eutrophication for small lowland waterbodies has to be considered differently than for lakes. For an individual waterbody (the local scale), nutrient enrichment is not necessarily a major impairment and its impact depends on the taxonomic group considered. Conversely, at the landscape scale, eutrophication is a major pressure on small waterbody biodiversity, especially because nutrient‐rich small waterbodies are dominant in the landscape. Therefore, conservation efforts should integrate the notion of pond regional networks or ‘pondscapes’, where the regional biodiversity is supported by a mosaic of trophic conditions, and promote the presence of less rich waterbodies.
High-altitude freshwater ecosystems and their biocoenosis are ideal sentinel systems to detect global change. In particular, pond communities are likely to be highly responsive to climate warming. ...For this reason, the Swiss National Park has included ponds as part of a long-term monitoring programme of the high-alpine Macun cirque. This cirque covers 3.6 km², has a mean altitude of 2,660 m a.s.l., and includes a hydrographic system composed of a stream network and more than 35 temporary and permanent ponds. The first two steps in the programme were to (i) make an inventory of the macroinvertebrates of the waterbodies in the Macun cirque, and (ii) relate the assemblages to local or regional environmental variables. Sampling was conducted in 25 ponds between 2002 and 2004. The number of taxa characterising the region (Macun cirque) was low, represented by 47 lentic taxa. None of them was endemic to the Alps, although several species were cold stenothermal. Average pond richness was low (11.3 taxa). Assemblages were dominated by Chironomidae (Diptera), and Coleoptera and Oligochaeta were also relatively well represented. Other groups, which are frequent in lowland ponds, had particularly poor species richness (Trichoptera, Heteroptera) or were absent (Gastropoda, Odonata, Ephemeroptera). Macroinvertebrate assemblages (composition, richness) were only weakly influenced by local environmental variables. The main structuring processes were those operating at regional level and, namely, the connectivity between ponds, i.e. the presence of a physical connection (tributary) and/or small geographical distance between ponds. The results suggest that during the long-term monitoring of the Macun ponds (started in 2005), two kinds of change will affect macroinvertebrate assemblages. The first change is related to the natural dynamics, with high local-scale turnover, involving the metapopulations characterising the Macun cirque. The second change is related to global warming, leading to higher local and regional richness through an increase in the number of colonisation events resulting from the upward shift of geographical ranges of species. At the same time the cold stenothermal species from Macun will be subject to extinction.
Manmade ecosystems provide a variety of resources that have strong economic values. We assessed the importance of 37 farm ponds for the biodiversity of Odonata in an agricultural landscape lacking ...natural wetlands in southwestern France. Farm ponds captured 40% of the regional species pool, including both common and rare species. The species assemblages were not correlated with pond use (e.g., cattle watering, duck farming, etc.) or to landscape variable. Species richness was correlated with pond area, suggesting that community diversity was primarily driven by autoecological processes. Farm ponds thus made a positive contribution to the maintenance of aquatic biodiversity. This added value for biodiversity should be considered when calculating the costs and benefits of constructing water bodies for human activities.
Ponds are now widely recognized to contribute significantly to regional freshwater biodiversity. Therefore, tools to easily and rapidly assess biological quality specifically for these aquatic ...habitats have been increasingly requested by conservation planners and nature managers. In close association with practitioners, we developed such a method for Switzerland; the pond biodiversity index "IBEM". The IBEM-Index is based on the assessment of the taxonomic richness of 5 groups: aquatic vegetation, Gastropoda, Coleoptera, adult Odonata and Amphibia. No abundance data are necessary and genus level identification is required for all groups except Amphibia (species level). The sampling methodology is a stratified random strategy and allows the use of richness estimators to transform the observed taxonomic richness (S sub(obs)) into true taxonomic richness (S sub(true)). As the IBEM assessment follows the methodology presented in the Water Framework Directive, it is based on the calculation of the ratio of true taxonomic richness (S sub(true)) to reference-based predicted richness (S sub(ref)). Each of the five taxonomic groups is assessed separately and the overall biological quality of any given pond (i.e. the IBEM-Index) is the average of the five ratios. This score is later converted into one of five quality classes for each pond: bad (0 to 0.2), poor (> 0.2 to 0.4), moderate (> 0.4 to 0.6), good (> 0.6 to 0.8), and high (> 0.8 to 1). In this paper, the implementation of the IBEM-Index is described in detail. The sampling methodologies are developed (for the biodiversity and the environmental variables) as well as the assessment methodology. Finally, two examples are presented in detail, for a "good" quality pond and for a "bad" quality pond. The method implementation also includes a website (http://campus.hesge.ch/ibem) which allows the online calculation of the index, and provides support for both sampling and assessment methodologies to users. The IBEM-Index is a rapid assessment method which gives an overall value of pond biodiversity in terms of taxa richness and can be used, for example, in regional screenings or site monitoring in Switzerland. Moreover, as biodiversity is generally recognized as a good indicator of global ecological quality, the IBEM-Index can also be used to investigate ecosystem quality.Original Abstract: Esta ampliamente reconocido que las pequenas masas de agua (charcas) contribuyen de forma significativa a la biodiversidad regional de las aguas dulces. Por tanto, las herramientas que de manera rapida facil evaluen especificamente la calidad biologica de estos habitats acuaticos estan siendo requeridas cada vez mas por profesionales de la gestion y conservacion del medio natural. En estrecha colaboracion con estos profesionales, se ha desarrollado un metodo de este tipo para Suiza; el indice de biodiversidad de charcas "IBEM". El Indice-IBEM se basa en la evaluacion de la riqueza taxonomica de 5 grupos: vegetacion acuatica, gasteropoda, coleopteros, odonatos (adultos) y anfibios. No son necesarios datos de abundancia y se requiere un nivel identificacion de genero para todos los grupos excepto para los anfibios (nivel de especie). Se usa un muestreo aleatorio estratificado que permite obtener estimadores para transformar la riqueza taxonomica observada (S sub(obs)) en riqueza taxonomica real (S sub(true)). La evaluacion IBEM sigue la metodologia de la Directiva Marco del Agua, que se basa en el calculo de la relacion entre la riqueza taxonomica real (S sub(true)) y la riqueza esperable en un estado de referencia (S sub(ref)). Cada uno de los cinco grupos taxondmicos se evalua por separado y la calidad biologica de una charca determinada (Indice-IBEM) es la media de los cinco coeficientes. Este resultado es posteriormente asignado a una de las cinco clases de calidad: malo (0 a 0.2), deficiente (> 0.2 a 0.4), moderado (> 0.4 a 0.6), bueno (> 0.6 to 0.8), y muy bueno (> 0.8 a 1). En este articulo, se describe detalladamente la aplicacion del indice IBEM y se desarrollan las metodologias de muestreo (para la biodiversidad y las variables ambientales) y de valoracion utilizadas. Por ultimo, se presentan con detalle dos ejemplos, una charca con "buena" calidad y otra con "mala" calidad. Se incluye tambien una pagina web (http://campus.hesge.ch/ibem), que permite el calculo del indice a traves de internet y sirve de apoyo a los usuarios en las metodologias de muestreo y de valoracion. El indice IBEM es un metodo de evaluacion rapida que da un valor general de la diversidad biologica de una charca en terminos de riqueza de taxones y se puede utilizar, por ejemplo, a nivel regional o en el seguimiento de una localidad, en Suiza. Ademas, como la biodiversidad es un buen indicador de la calidad ecologica global, el indice IBEM tambien se puede usar para evaluar el estado del ecosistema.
Due to legal requirements, nature managers increasingly have to carry out assessments of biodiversity for conservation purposes. For ponds, a type of waterbody now widely recognized as an important ...reservoir for freshwater biodiversity, standardized bioassessment methods are needed, but still rare. We produced such a tool for small lowland waterbodies in Switzerland: the Pond Biodiversity Index ("IBEM"). This Index is the adaptation of a method used by researchers for assessing the biodiversity in ponds, PLOCH, which does not currently meet the requirements for routine use by nature managers because it is too expensive and requires a high skill level in taxonomic identification. A method intended for practitioners has to be simple, standardized, cheap, adjustable, and consistent with the legislative framework. In order to fulfill these requirements, the theoretical and practical aspects of IBEM were developed with a group of representative end users including nature conservation managers, consultants, governmental organizations and taxonomic experts. To develop the method, we used a species dataset from 63 Swiss lowland ponds which included five taxonomic groups: aquatic plants, aquatic Gastropoda, aquatic Coleoptera, adult Odonata and Amphibia. The following topics were addressed: (i) the number and type of taxonomic groups which should be used for producing the index (is it possible to use surrogates?) (ii) the level of identification for each taxonomic group (species? genus? family?) (iii) the sampling strategy (sampling technique, number of replicates), (iv) the calculation of a unique index and the strategy for assessing its score, and (v) the transfer of this new method to end users. The new method IBEM uses all five taxonomic groups, because a subset of groups did not produce reliable assessments of pond biodiversity. Identification to genus level is required for four groups (aquatic plants, aquatic Gastropoda, aquatic Coleoptera, adult Odonata) and species level for Amphibia. The sampling methodology is based on the stratified random strategy used in the PLOCH method, but with a slight modification in the number of samples per pond. The assessment follows the methodology adopted by the European Water Framework Directive, and the ratio of the observed richness to a reference-based predicted richness is translated into one of five quality categories for each pond. The final index is the mean of the five assessment scores. To facilitate the implementation of the IBEM method, a website (http://campus.hesge.ch/ibem) enables online calculation of the index, and provides instructions on both sampling and assessment methodologies. Furthermore, training courses are organized by the authors of the method for end users.Original Abstract: Debido a requerimientos legales, es cada vez mas necesario que los gestores del medio ambiente lleven a cabo evaluaciones de la biodiversidad dirigidas a la conservacion de la naturaleza. Para las charcas, pequenas masas de agua ampliamente reconocidas como importantes reservorios de diversidad bioldoica acuatica, los metodos normalizados de bio-evaluacion son necesarios, pero aun escasos. Para esta tipologia de pequenas masas de agua situadas a baja altitud en Suiza, se ha elaborado el indice de Biodiversidad de charcas ("IBEM"). Este indice es la adaptacion de un metodo utilizado por los investigadores para evaluar la diversidad biologica en charcas, PLOCH, que no cumplia los requisitos para un uso rutinario por parte de los gestores del medio natural por ser demasiado caro y requerir un alto nivel de experiencia en la identificacion taxonomica. Un metodo destinado a estos profesionales tiene que ser sencillo, estandarizado, econdmico, ajustable y en consonancia con el marco legislativo. Con el fin de cumplir estos requisitos, los aspectos teoricos y practicos de IBEM se han desarrollado con un grupo representativo de posibles usuarios, incluyendo gestores conservadores, consultores, organizaciones gubernamentales y expertos en taxonomia. Para desarrollar el metodo, se ha utilizado una base de datos de 63 charcas Suizas, situadas en altitudes bajas, que incluye cinco grupos taxondmicos: plantas acuaticas, gasteropodos acuaticos, coleopteros acuaticos, odonatos adultos y anfibios. Se han estudiado los siguientes aspectos: (i) el numero y tipo de grupos taxonomicos que se deben utilizar (es posible el uso de sustitutos?) (ii) nivel de identificacion para cada grupo taxonomico (especie, genero, familia?) (iii) estrategia de muestreo (tecnica, numero de replicas), (iv) calculo de un indice unico y procedimiento para la asignacion de valores y (v) la transferencia de este metodo a los posibles usuarios. El nuevo metodo IBEM utiliza los cinco grupos taxonomicos, ya que un subconjunto de ellos no produciria evaluaciones fiables de la diversidad biologica de la charca. La identificacion a nivel de genero es necesaria para cuatro de estos grupos (plantas acuaticas, gasteropodos acuaticos, coleopteros acuaticos, y odonatos adultos) y para los anfibios es necesario el nivel de especie. El muestreo sigue un diseno aleatorio estratificado, utilizado en el metodo PLOCH, pero con una ligera modificacion en el numero de muestras por charca. La evaluacion sigue la metodologia adoptada por la Directiva Marco de Aguas, y la relacion entre la riqueza observada y la del estado de referencia se traduce en una de las cinco categorias de calidad para cada charca. El indice final es la media de las cinco puntuaciones de la evaluacion. Para facilitar la aplicacion del metodo IBEM, un sitio web (http://campus.hesge.ch/ibem) permite calculo del indice a traves de la red y proporciona instrucciones tanto de las metodologias de muestreo como de la valoracion. Ademas, los autores han organizado cursos de formacion sobre el metodo para los usuarios.
Nutrient-rich freshwater ecosystems are generally considered as having low ecological quality and low associated biodiversity. In such systems we analysed the effects of water quality on biodiversity ...of several species groups, to determine tipping points and tools for monitoring. We investigated the water quality of 99 eutrophic and hypertrophic shallow lakes with extensive fish culture during a 3-year study, through the measures of physico-chemical parameters, phytoplankton biomass and structure. In a second step, we related the water quality with richness of aquatic plants, macroinvertebrates and dragonflies. With concentrations of chlorophyll-a above 30 or 70 μg l
−1
, shallow lakes are normally classified, respectively, in a poor or bad ecological state. However, our results show that chlorophyll-a concentrations up to 78 μg l
−1
could be found together with relatively high species or family richness of aquatic plants, invertebrates and dragonflies. We identified most tipping points with 50–60 μg l
−1
of chlorophyll-a, values above which a significant decrease of species diversity was found. For monitoring of these shallow lakes we propose to use chlorophyll-a concentrations in combination with water transparency during spring. These parameters are easily applicable and cheap and they yield a good forecast of the biodiversity for the species groups studied.
We assessed the benefit of 11 gravel pits for the settlement of waterbird communities in an urbanized area lacking natural wetlands. Gravel pits captured 57% of the regional species pool of aquatic ...birds. We identified 39 species, among which five were regionally rare. We used the Self-Organizing Map algorithm to calculate the probabilities of presence of species, and to bring out habitat conditions that predict assemblage patterns. The age of the pits did not correlate with assemblage composition and species richness. There was a positive influence of macrophyte cover on waterbird species richness. Larger pits did not support more species, but species richness increased with connectivity. As alternative wetland habitats, gravel pits are attractive to waterbirds, when they act as stepping stones that ensure connectivity between larger natural and/or artificial wetlands separated in space.
Sur les Causses arides du Quercy (S.-O. de la France), de nombreuses mares ont été creusées dans la roche. Ces mares constituent les seules eaux superficielles de ce plateau calcaire où l'eau ...s'infiltre rapidement.
L'évolution naturelle des mares conduit à leur atterrissement et une étude comparative de trois mares à différents stades de comblement a montré l'évolution des paramètres abiotiques (température, concentration en oxygène dissous...) en fonction du niveau de comblement. Parallèlement, les mares varient en terme de richesse spécifique de la faune et de la flore. Chaque stade de comblement abrite une faune particulière et participe à la biodiversité globale de ces milieux et même de l'écosystème caussenard dans son ensemble.
Pour analyser ces milieux à une échelle supérieure, des échantillons ont été récoltés sur trente mares afin d'étudier les facteurs affectant la distribution de la faune dans un réseau de mares. Nous avons identifié 230 espèces d'invertébrés et 6 espèces de vertébrés. Les résultats ainsi obtenus ne permettent pas de dresser une typologie des mares ni de dégager des peuplements caractéristiques ou de réaliser une classification ascendante de ces milieux. Les mares entourées d'une matrice terrestre sont assimilables à des îles pour la faune aquatique.
C'est pourquoi nous avons choisi d'étudier plus précisément la distribution de cinq groupes ayant des capacités de dispersion différentes : Odonates, Coléoptères, Amphibiens, Mollusques et Oligochètes. La surface des mares affecte la distribution des Odonates. Le pourcentage de forêt autour des mares influence la distribution des
Amphibiens. Pour les Mollusques et les Oligochètes, les animaux à dispersion passive, les résultats indiquent que la distribution des espèces est similaire à une distribution au hasard. Pour les Coléoptères, la distribution des espèces n'est pas due au hasard mais nous n'avons pas pu mettre en évidence les facteurs explicatifs de cette distribution.
Nous avons utilisé la méthode de capture-marquage-recapture pour estimer le degré de lien de trois populations en patch d'Odonates. Nous avons montré que trois facteurs influencent la dispersion des Odonates : des facteurs abiotiques (conditions météorologiques), des différences inter spécifique (sensibilité aux conditions météorologiques, taille et comportement des espèces), des différences intra spécifiques (âge et sexe).
Ces travaux mettent en évidence le rôle des mares au niveau de la biodiversité, le rôle du réseau de mares et de l'évolution temporelle des paramètres dans le maintien de cette biodiversité. Les différents résultats obtenus sont discutés en vue de proposer une méthode de gestion rationnelle et durable de ces milieux.
The influence of draining a large reservoir (Pareloup, South of France) on the population structure and the growth of roach is studied in this work. This reservoir, with an area of 13 km
2, drained ...in June 1993, was refilled 2 months later. Fish were sampled monthly before draining (1981) and after refilling (1997) by nylon monofilament gill nets used at the same catching effort for both periods. This permitted a comparison to be made between the density of roach and length distribution before and after refilling. Changes in growth were determined by scalimetry. The observed difference in population structure and growth underlined that the differences are mainly due to a greater growth rate after refilling during the first 2 years of roach life. These growth changes are explained by the decrease in roach density and the increase in 1993 of the biomass of Zooplankton, which constitute the main feeding resource for 0
+ and 1
+ roach. The study led us to propose hypotheses on the ecological significance of growth changes induced by refilling, which can be considered as a rejuvenation of the aquatic ecosystem.
Cette étude décrit l'influence de la vidange d'un grand réservoir (lac de Pareloup, France) sur la structure et la croissance d'une population de gardons. Ce réservoir, d'une surface de 13 km
2, vidangé en juin 1993, a été remis en eau après une période d'assec de deux mois. Les poissons ont été échantillonnés mensuellement avant vidange (1981) et après vidange (1997) à l'aide de filets maillants utilisés avec un effort de pêche similaire pour les deux périodes. Cela a permis de comparer les densités de gardon et les distributions de tailles avant et après vidange. Les changements de croissance ont été déterminés par scalimétrie, les différences observées dans la structure en taille et la croissance révèlent une meilleure croissance des gardons durant leurs deux premières années de vie après la vidange. Cette accélération de croissance peut être expliquée par une diminution de la densité de gardon et par une augmentation de la biomasse de zooplancton en 1993 qui constitue la principale source de nourriture des 0
+ et 1
+. Cette étude a conduit à proposer des hypothèses quant à la signification écologique des changements de croissance induits par la vidange qui peut être considérée comme un rajeunissement de l'écosystème aquatique.
PDF
