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Title: Use of diatoms for evaluating ecological status in UK freshwaters
Author: M.G. Kelly
Author: S. Juggins
Author: H. Bennion
Author: A. Burgess
Author: M. Yallop
Author: H. Hirst
Author: L. King
Author: B.J. Jamieson
Author: R. Guthrie
Author: B.. Rippey
Author: Environment Agency
Document Type: Monograph
Annotation: Environment Agency Project ID:EAPRJOUT_1424, Representation ID: 481, Object ID: 2579; Environment Agency Project ID:EAPRJOUT_1429, Representation ID: 485, Object ID: 2584; Environment Agency Project ID:EAPRJOUT_1527, Representation ID: 530, Object ID: 2665
This report describes the development and testing of a diatom-based tool to fulfil UK obligations to include phytobenthos in the assessment of ecological status of freshwaters. Separate tools have been developed for lakes and rivers, although they share many features, including a conceptual underpinning, in common. The new tool is based on the Trophic Diatom Index (TDI), a metric already in use with UK statutory agencies to monitor eutrophication in rivers. The conceptual framework for the model is based around a quantitative and qualitative 'visualisation' of the state of biofilms in UK rivers and lakes in the absence of anthropogenic pressures. This recognises that such biofilms are dynamic, with both composition and abundance of the taxa present changing over relatively short periods of time. The hydrological regime and grazing pressure, in particular, will influence the phytobenthos and, as a result, there is a considerable amount of within-site variability, particularly in flowing waters. Lakes were divided into three types, based on their alkalinity, and reference sites were established using a combination of palaeoecological techniques and expert judgement. A separate index - the Lake Trophic Diatom Index (LTDI) - was established via recalibration of the TDI and EQR values were calculated in the same manner as for rivers except that a separate reference LTDI value was defined for each lake type. Whereas the lake tool can be validated using a combination of spatial and palaeoecological studies, the river tool was developed using only contemporary spatial data. In order to establish that there have, in fact, been changes in diatom assemblages over time and that these are driven by nutrients, we removed diatoms from herbarium specimens of common aquatic macrophytes collected before 1930. In some cases, specimens were > 100 years old. Compared with the contemporary diatom flora, almost all the herbarium samples had assemblages that suggested much lower nutrient concentrations. Both tools have been tested extensively, and results of tests of the river tool on the Rivers Wye and Axe, and the lakes tool on the Lake District lakes are also reported.
Publisher: Environment Agency
Subject Keywords: PhytobenthosWater Framework DirectiveDiatomsRiversFreshwater ecologyLakesWater qualitySampling
Taxonomic Keywords: Bacillariophyceae
Extent: 171
Total file downloads: 44

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