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Indice Diatomique Réunion (IDR): a new river diatom index dedicated to a specific ultramarine and tropical biogeographical context

Abstract : The Water Framework Directive (JOCE 2000) needs to be applied on the European continental area as for other ultramarine territories as French overseas departments (in our case, Reunion Island). For such specific territories with a strong biogeographical concern, biological indexes set-up and validated in continental Europe cannot work properly. The main problems encountered result from strong specificities in the field of geochemical and climatic conditions, of taxa list and of their local ecology. Under the joint demand of the Reunion Water Office, local services of Environment Ministry (DEAL Reunion) and ONEMA, a scientific consortium grouping ASCONIT Consultancy and IRSTEA drove a 3 year-study based on network sites and other particular sites, aiming to: 1) describe in situ abiotic environmental condition of rivers (physico-chemistry, chemistry, descriptors of general ambiance like shading, flow velocity, depth...); 2) identify and count relative abundances of taxa; and 3) set-up a new Diatom Index dedicated to Reunion, based on relationships between abiotic descriptors and taxa ecology. The study was based on 256 samples and records obtained during 3 years at 55 different sites along five field campaigns covering 2 different seasons. A huge work was to identify and count the species in this new context. 343 different species have been observed, of which 162 determined at the species level. 28 other species were close to a known species (cf or aff.), 153 identified at the genus level were given a number code at the species level. 175 enough occurring species were used to build the index and were given an ecological profile. Because of a very dilutive context, we chose to principally base the index calculation on a list of alarm taxa named "Taxa –", which presence is synonym of strong anthropogenic alteration. This new index provides satisfying assessment results which will be presented.
Mots-clés : REUNION ILE
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Submitted on : Friday, May 15, 2020 - 10:47:12 PM
Last modification on : Wednesday, September 28, 2022 - 4:20:10 PM


  • HAL Id : hal-02597586, version 1
  • IRSTEA : PUB00036523



François Delmas, Sébastien Boutry, Gilles Gassiole, Juliette Tison-Rosebery, J.L. Giraudel, et al.. Indice Diatomique Réunion (IDR): a new river diatom index dedicated to a specific ultramarine and tropical biogeographical context. Use of Algae for Monitoring Rivers, Jun 2012, Madrid, Spain. pp.1. ⟨hal-02597586⟩



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