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- Bailet, Bonnie
(författare)
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New methods for improving water management - Exploring the role of diatoms in ecosystems
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Diatoms are photosynthetic microalgae which are well known to react quickly to environmental changes and are widely used as bioindicators within Water Framework Directive. However, diatom identification by light microscopy is time-consuming and error-prone, creating a need for alternative, faster and more reproducible methods for characterising diatom communities. This thesis describes the development and application of two such methods: a molecular approach using metabarcoding and a trait-based approach using combinations of different diatom morphological traits. Both approaches were shown to have potential for use in environmental assessment, as they revealed the response of diatoms to environmental change and enabled better representation of the diatom community. However, results from the two approaches were not directly comparable to results obtained by conventional microscopy and diatom DNA and trait data should not be used with tools calibrated for morphotaxa data. Discrepancies in molecular output data between laboratories revealed a strong need for standardisation and best-practice guidelines. Nutrient indices developed for each novel approach performed well and showed potential for use in assessment of total phosphorus levels in Fennoscandia freshwater. The molecular-based index showed differences in performance for stream and lake samples. The trait-based index performed equally well for both types of site, but current limitation of this index is that selection of meaningful traits must be done for each new gradient. Further work is needed on diatom traits and their response to environmental changes, to obtain reproducible and comparable molecular outputs and to continue the development of new indices calibrated to diatom DNA and trait data.
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| 2. |
- Kahlert, Maria, et al.
(författare)
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Same same, but different: The response of diatoms to environmental gradients in Fennoscandian streams and lakes-barcodes, traits and microscope data compared
- 2021
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Ingår i: Ecological Indicators. - : Elsevier BV. - 1470-160X .- 1872-7034. ; 130
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Tidskriftsartikel (refereegranskat)abstract
- We developed and compared the performance of freshwater benthic diatom indices calculated from (i) traditional morphological species identification, (ii) Amplicon Sequence Variants (ASVs) obtained via DNA metabarcoding, and (iii) morphological traits to indicate eutrophication in rivers and lakes in Fennoscandia. Based on the results, we provided recommendations for the future routine use of diatom bioassessment tools in environmental monitoring and assessment. Our results show that ASVs are the most promising candidates to be used in environmental assessment. Indices based on ASVs correlated better with TotP concentrations than morphological taxa data, whereas the trait indices correlated least. We could see by studying the taxonomic assignments of the ASVs that traditional morphotaxa were divided up into several ASVs with different ecological profiles, which explained part of the better index performance and also encourages further studies on diatom diversity and ecological preferences. In general, ASV- and morphotaxon-specific optima differed slightly between streams and lakes, but were significantly correlated with each other. This means that it should be possible to develop a common index that is applicable in both streams and lakes, but boundary values with respect to TotP might need to be set separately for them. More knowledge on diatom traits is required to enable their use for environmental assessment.
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