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Canton, Switzerland

Cordonier A.,Water Ecology Service | Gallina N.,University of Geneva | Nirel P.M.,Water Ecology Service
Vie et Milieu | Year: 2010

The goal of this study is to evaluate the influence of four Geneva geotypes (characterized by the composition of trace elements in water), of the season and of water quality on the distribution of epilithic diatoms in the main rivers in the canton of Geneva (Switzerland). To achieve this, we used 72 samples of diatoms as well as some physical-chemical and bacteriological analyses. The sampling was conducted in the framework of monitoring the surface water quality between 1998 and 2004. For each of these 72 samples, the season (winter-spring or summer) as well as one of the four geotypes ("Jura", "Plaine", "Alpes", "Marais") was accounted for. Nine sample groups based upon the distribution of 120 diatom taxa were defined by statistical analyses. The flora of these nine groups is mainly composed of common and frequentlyoccurring species in the surface waters of the Swiss Plateau that represents good to average water quality. Nonetheless, some of the rarest species confined to poorly-nourished calcareous regions, were sampled only in certain groups. Our results show that in addition to the water quality, the geochemical signature influences the floral composition of Geneva's diatoms. It would be interesting to expand this type of study to the Swiss hydrographical network, to define its ecoregions, to measure its influence on the assemblage of diatoms and to ultimately adapt it to our objectives of biological quality.

Visco J.A.,University of Geneva | Apotheloz-Perret-Gentil L.,University of Geneva | Cordonier A.,Water Ecology Service | Esling P.,University of Geneva | And 4 more authors.
Environmental Science and Technology | Year: 2015

Diatoms are widely used as bioindicators for the assessment of water quality in rivers and streams. Classically, the diatom biotic indices are based on the relative abundance of morphologically identified species weighted by their autoecological value. Obtaining such indices is time-consuming, costly, and requires excellent taxonomic expertise, which is not always available. Here we tested the possibility to overcome these limitations using a next-generation sequencing (NGS) approach to identify and quantify diatoms found in environmental DNA and RNA samples. We analyzed 27 river sites in the Geneva area (Switzerland), in order to compare the values of the Swiss Diatom Index (DI-CH) computed either by microscopic quantification of diatom species or directly from NGS data. Despite gaps in the reference database and variations in relative abundance of analyzed species, the diatom index shows a significant correlation between morphological and molecular data indicating similar biological quality status for the majority of sites. This proof-of-concept study demonstrates the potential of the NGS approach for identification and quantification of diatoms in environmental samples, opening new avenues toward the routine application of genetic tools for bioassessment and biomonitoring of aquatic ecosystems. (Graph Presented). © 2015 American Chemical Society.

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