Biodiversité

Préserver la biodiversité

Les préoccupations concernant la préservation de la biodiversité finissent souvent par se retrouver du côté des perdants quand il s’agit de mettre dans la balance les intérêts conflictuels et leur perte n’est habituellement quantifiée qu’en termes financiers quand il est déjà trop tard. Nous cherchons à comprendre ce que signifie réellement la biodiversité, les avantages qu'elle apporte, et quelles mesures peuvent être utilisées pour la préserver.

Actualités

Comment les écosystèmes réagissent-ils aux apports excessifs de nutriments ?

16 octobre 2019

Dans les écosystèmes aquatiques, les mollusques et les plantes aquatiques filtrent et épurent l'eau, si bien que le développement algal reste habituellement modéré. Des essais menés dans les étangs expérimentaux de l'Eawag montrent cependant que cet équilibrage peut être mis en échec lorsque les deux filtreurs coexistent.

En savoir plus

Origine de la diversité des épinoches du Lac de Constance : une énigme résolue

23 septembre 2019

De nouvelles espèces peuvent apparaître rapidement lorsqu’elles colonisent de nouvelles niches. Mais les mutations génétiques sont rares, aussi comment une spéciation écologique si rapide est-elle possible ? Les écotypes fluviaux et lacustres d’épinoches qui sont apparus depuis peu dans le lac de Constance apportent une réponse surprenante à cette question. En savoir plus

More news

Événements

23.10.​2019,
14h00
Eawag Kastanienbaum
Eco-evolutionary dynamics of intraspecific variation
30.10.​2019,
14h00
Eawag Kastanienbaum
Prospects for genomics research in Tanzania: Opportunities and challenges
06.11.​2019,
14h00
Eawag Kastanienbaum
Eco-evolutionary dynamics in complex systems

Publications académiques

A combinatorial view on speciation and adaptive radiation

Speciation is often thought of as a slow process due to the waiting times for mutations that cause incompatibilities, and permit ecological differentiation or assortative mating. Cases of rapid speciation and particularly cases of rapid adaptive radiation into multiple sympatric species have remained somewhat mysterious. We review recent findings from speciation genomics that reveal an emerging commonality among such cases: reassembly of old genetic variation into new combinations facilitating rapid speciation and adaptive radiation. The polymorphisms in old variants frequently originated from hybridization at some point in the past. We discuss why old variants are particularly good fuel for rapid speciation, and hypothesize that variation in access to such old variants might contribute to the large variation in speciation rates observed in nature.
Marques, D. A.; Meier, J. I.; Seehausen, O. (2019) A combinatorial view on speciation and adaptive radiation, Trends in Ecology and Evolution, 531-544, doi:10.1016/j.tree.2019.02.008, Institutional Repository

Microbial residence time is a controlling parameter of the taxonomic composition and functional profile of microbial communities

A remaining challenge within microbial ecology is to understand the determinants of richness and diversity observed in environmental microbial communities. In a range of systems, including activated sludge bioreactors, the microbial residence time (MRT) has been previously shown to shape the microbial community composition. However, the physiological and ecological mechanisms driving this influence have remained unclear. Here, this relationship is explored by analyzing an activated sludge system fed with municipal wastewater. Using a model designed in this study based on Monod-growth kinetics, longer MRTs were shown to increase the range of growth parameters that enable persistence, resulting in increased richness and diversity in the modeled community. In laboratory experiments, six sequencing batch reactors treating domestic wastewater were operated in parallel at MRTs between 1 and 15 days. The communities were characterized using both 16S ribosomal RNA and non-target messenger RNA sequencing (metatranscriptomic analysis), and model-predicted monotonic increases in richness were confirmed in both profiles. Accordingly, taxonomic Shannon diversity also increased with MRT. In contrast, the diversity in enzyme class annotations resulting from the metatranscriptomic analysis displayed a non-monotonic trend over the MRT gradient. Disproportionately high abundances of transcripts encoding for rarer enzymes occur at longer MRTs and lead to the disconnect between taxonomic and functional diversity profiles.
Mansfeldt, C.; Achermann, S.; Men, Y.; Walser, J.-C.; Villez, K.; Joss, A.; Johnson, D. R.; Fenner, K. (2019) Microbial residence time is a controlling parameter of the taxonomic composition and functional profile of microbial communities, ISME Journal, 13(6), 1589-1601, doi:10.1038/s41396-019-0371-6, Institutional Repository

Light limitation increases multidimensional trait evenness in phytoplankton populations

Individual-level variation arising from responses to environmental gradients influences population and community dynamics. How such responses empirically relate to the mechanisms that govern species coexistence is, however, poorly understood. Previous results from lake phytoplankton communities suggested that the evenness of organismal traits in multiple dimensions increases with resource limitation, possibly due to resource partitioning at the individual level. Here we experimentally tested the emergence of this pattern by growing two phytoplankton species (Pseudokirchneriella subcapitata and Microcystis aeruginosa) under a gradient of light intensity, in monoculture and jointly. Under low light (resource) conditions, the populations diversified into a wide range of phenotypes, which were evenly distributed in multidimensional trait space (defined by four pigment-related trait dimensions), consistent with the observed field pattern. Our interpretation is that under conditions of light limitation, individual phytoplankton cells alter photosynthetic traits to reduce overlap in light acquisition, acquiring unexploited resources and thereby likely maximising individual success. Our results provide prime experimental evidence that resource limitation increases the evenness of conspecific and heterospecific microbial phenotypes along trait axes, advancing our understanding of trait-based coexistence.
Fontana, S.; Thomas, M. K.; Reyes, M.; Pomati, F. (2019) Light limitation increases multidimensional trait evenness in phytoplankton populations, ISME Journal, 13, 1159-1167, doi:10.1038/s41396-018-0320-9, Institutional Repository

Multiple-stressor effects on freshwater fish: importance of taxonomy and life stage

Interactions among multiple anthropogenic stressors threaten freshwater fish and pose challenges for fisheries management and conservation. Previous studies of multiple‐stressor effects on freshwater fish suggest a prevalence of antagonistic interactions. However, taxonomy, life stage and/or environmental context likely modify the magnitude and direction of fish responses to multiple stressors. Stressor intensity, impact mechanism, exposure time and ecosystem size may further affect interaction outcomes. Large‐scale studies quantifying how these variables moderate stressor interactions are lacking. To address this knowledge gap, we performed a meta‐analysis of 29 factorial multiple‐stressor experiments to examine the influence of seven potential moderator variables on the magnitude and direction of stressor interactions. Using weighted random‐effects meta‐analytic models, we demonstrate the importance of taxonomic identity and life stage for interaction outcomes. In particular, Cypriniformes showed stronger antagonisms than Salmoniformes, as did larval fish compared to juveniles. Interaction outcomes also varied among the measured fish responses with survival yielding stronger antagonisms than biomass. Increasing experimental duration and volume of the experimental units both drove interactions towards synergisms, supporting findings from previous studies that synergisms take time and space to develop. In an era when the number of stressors affecting freshwater systems is increasing rapidly, our study provides a vital step towards identifying generalities in multiple‐stressor outcomes and thus improved predictions of multiple‐stressor impacts. Furthermore, our meta‐analysis complements studies in real streams, rivers and lakes by providing an experimentally derived context for the growing number of multiple‐stressor assessments in research, management and conservation of freshwater fish.
Lange, K.; Bruder, A.; Matthaei, C. D.; Brodersen, J.; Paterson, R. A. (2018) Multiple-stressor effects on freshwater fish: importance of taxonomy and life stage, Fish and Fisheries, 19(6), 974-983, doi:10.1111/faf.12305, Institutional Repository

Estimating species distribution and abundance in river networks using environmental DNA

All organisms leave traces of DNA in their environment. This environmental DNA (eDNA) is often used to track occurrence patterns of target species. Applications are especially promising in rivers, where eDNA can integrate information about populations upstream. The dispersion of eDNA in rivers is modulated by complex processes of transport and decay through the dendritic river network, and we currently lack a method to extract quantitative information about the location and density of populations contributing to the eDNA signal. Here, we present a general framework to reconstruct the upstream distribution and abundance of a target species across a river network, based on observed eDNA concentrations and hydro-geomorphological features of the network. The model captures well the catchment-wide spatial biomass distribution of two target species: a sessile invertebrate (the bryozoan Fredericella sultana) and its parasite (the myxozoan Tetracapsuloides bryosalmonae). Our method is designed to easily integrate general biological and hydrological data and to enable spatially explicit estimates of the distribution of sessile and mobile species in fluvial ecosystems based on eDNA sampling.
Carraro, L.; Hartikainen, H.; Jokela, J.; Bertuzzo, E.; Rinaldo, A. (2018) Estimating species distribution and abundance in river networks using environmental DNA, Proceedings of the National Academy of Sciences of the United States of America PNAS, 115(46), 11724-11729, doi:10.1073/pnas.1813843115, Institutional Repository
A la bibliothèque

Publications professionelles

Methoden zur Untersuchung und Beurteilung der Fliessgewässer. Makrophyten - Stufe F (flächendeckend) und Stufe S (systembezogen). Entwurf zur Vernehmlassung

Im Rahmen des Modul-Stufen-Konzepts (MSK) werden Methoden zur Untersuchung und Bewertung der Fliessgewässer für die Bereiche Hydrodynamik und Morphologie, Chemie und Ökotoxikologie sowie Biologie erarbeitet. Es sind Methoden auf zwei Stufen vorgesehen, die sich in ihrer Bearbeitungsintensität und ihrem räumlichen Bezug unterscheiden. Der vorliegende Bericht beschreibt, wie die aquatische Vegetation der Fliessgewässer flächendeckend in einem grösseren Gebiet (Stufe F) oder systembezogen, mittels eines höher aufgelösten Messstellennetzes, in einem Einzugsgebiet (Stufe S) erfasst und beurteilt werden kann. Bei der Kartierung von Gewässerabschnitten mit einheitlichen Standortverhältnissen werden alle Gefässpflanzen, Armleuchterlagen, Moose und grün gefärbten Fadenalgen sowie polsterbildenden Algen auf der Gewässersohle erfasst. Von der Ufervegetation werden nur Arten berücksichtigt, die ihre Hauptverbreitung im regelmässig überfluteten Uferbereich haben. Die Gewässerabschnitte werden aufgrund von abiotischen Standortfaktoren (Beschattung, Gefälle, Abfluss, Wassertiefe, Substratzusammensetzung) einem von sechs verschiedenen Vegetations-Flusstypen unterschiedlicher Abflussklassen zugewiesen. Die Vegetation wird anschliessend durch Vergleich des Istzustandes mit einer möglichst naturnahen Referenz für den jeweiligen Vegetations-Flusstyp typspezifisch beurteilt. Die Bewertung, die sich an den ökologischen Zielen in Anhang 1 der Gewässerschutzverordnung (GSchV) orientiert, erfolgt mittels typ-spezifischer Zielhierarchien und Wertefunktionen in fünf Beurteilungsklassen. Bewertet werden die Bereiche Diversität (Anzahl typgerechte Arten und Wuchsformen), Zusammensetzung (Anteile typgerechter Wuchsformen und Neophyten sowie Dominanzstruktur) und Biomasse (absolute Deckung höherer Makrophyten und Algen) im Abschnitt. Ergänzend zu dieser gewässerökologischen Bewertung erfolgt eine Bewertung aus Sicht Naturschutz, anhand der nationalen Prioritätseinstufung der vorhandenen Arten sowie ihrem Beitrag zur Biodiversität, anhand von Leitwerten. Im Anschluss an die Typisierung und Bewertung, die durch ein elektronisches Auswertungs-Tool erfolgt, prüfen die Bearbeitenden die Resultate auf Plausibilität. Als Endprodukte werden einerseits Datentabellen mit allen Informationen zu den kartierten Untersuchungsabschnitten generiert, andererseits erfolgt eine Zusammenstellung der wichtigsten Informationen pro Untersuchungsabschnitt.
Känel, B.; Michel, C.; Reichert, P. (2018) Methoden zur Untersuchung und Beurteilung der Fliessgewässer. Makrophyten - Stufe F (flächendeckend) und Stufe S (systembezogen). Entwurf zur Vernehmlassung, 119 p, Institutional Repository

Conseil et transfert de savoir

Bureau de conseil pour la pêche (FIBER)

Programme cours d'eau suisses

Les départements principalement concernés par ce domaine

Expertes et experts

Prof. Dr. Martin Ackermann
  • bactéries
  • génétique
  • antibiotiques
  • résistances
  • évolution
  • ecologie
Prof. Dr. Florian Altermatt
Dr. Jakob Brodersen
  • isotopes
  • ecologie
Dr. Helmut Bürgmann
Dr. Philine Feulner
Prof. Dr. Jukka Jokela
  • algues
  • ecotoxicologie aquatique
  • poissons
  • génétique
  • plancton
  • protéomique
Dr. Carlos Melian
Dr. Francesco Pomati
Dr. Katja Räsänen
Prof. Dr. Ole Seehausen
  • poissons
  • génétique
  • ecologie
  • évolution
PD Dr. Piet Spaak
  • plancton
  • sédiments
Prof. Dr. Christoph Vorburger
Dr. Christine Weber