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Étude de la variabilité et de l'incertitude de l'indice IPLAC : application sur les grands lacs aquitains

Abstract : Implemented nationally since 2012, the IPLAC (Lacustrine Phytoplankton Index) index is used to assess the ecological status of water bodies from the taxonomic composition of the phytoplankton communities and the average chlorophyll a. It is based on 3 sampling campaigns to represent the entire annual phytoplankton development cycle (spring, summer and autumn). The objective of this study was to evaluate the variability and the temporal robustness of the IPLAC index, by studying the influence of the choosing dates of the campaigns on the value of the final note and on the ecological status class of the water body. This work was based on monthly (or near-monthly) phytoplankton analysis of the waters of the 4 major Aquitaine lakes from 2010 to 2016. The IPLAC values and its associated metrics (specific composition metric - MCS and algal biomass metric - MBA) were calculated for all possible combinations of campaigns. These values were then compared to the target values determined with the totality of the campaigns carried out over a year. IPLAC values have also been correlated with phosphorus levels (eutrophication proxy of water bodies). While for the statistical tests, the temporal variability of the campaigns has no effect on the IPLAC score, nevertheless this study has shown significant variability in terms of change in ecological status class and difference with the target value. This variability depends on the depth of the lakes: shallow lakes have greater variability than those of higher average depths. It also depends on the proximity of the class boundaries which is positively correlated with the percentage of ecological status classification error of the water body relative to the class of the target value.
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https://hal.inrae.fr/hal-02608847
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Submitted on : Saturday, May 16, 2020 - 5:03:41 PM
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  • HAL Id : hal-02608847, version 1
  • IRSTEA : PUB00060542

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Christophe Laplace-Treyture, G.M. Tzvetan. Étude de la variabilité et de l'incertitude de l'indice IPLAC : application sur les grands lacs aquitains. [Rapport de recherche] irstea. 2019, pp.102. ⟨hal-02608847⟩

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