Macroinvertebrate indicators of lake acidification: analysis of monitoring data from UK, Norway and Sweden |
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Authors: | Ann Kristin Schartau S. Jannicke Moe Leonard Sandin Ben McFarland Gunnar G. Raddum |
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Affiliation: | 1. Norwegian Institute for Nature Research, Gaustadalléen 21, 0349, Oslo, Norway 2. Norwegian Institute for Water Research, Gaustadalléen 21, 0349, Oslo, Norway 3. Department of Environmental Assessment, Swedish University of Agricultural Sciences, P.O. Box?7050, Uppsala, 750 07, Sweden 4. Environment Agency, South West Region, Manley House, Kestrel Way, Exeter, EX2 7LQ, UK 5. Department of Biology, LFI-Unifob, University of Bergen, Thorm?lensgt. 49, 5006, Bergen, Norway
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Abstract: | Although the acid sensitivity of many invertebrate species in lakes is well known, methods for assessment of lake acidification based on macroinvertebrate samples are less developed than for rivers. This article analyses a number of existing metrics developed for assessment of river acidification, and evaluates their performance for assessment of lake acidification. Moreover, new species-based indicators of lake acidification were developed and tested. The selected dataset contains 668 samples on littoral macroinvertebrates from 427 lakes with almost 60% of the samples from Sweden and the rest from UK and Norway. Flexible, non-parametric regression models were used for explorative analyses of the pressure–response relationships. The metrics have been assessed according to their response to pH, the degree of non-linearity of the response and the influence of humic compounds. Acid-sensitive metrics often showed a threshold in response to pH between 5.8 and 6.5. Highly acid-tolerant metrics were typically dominant across the whole pH range. Humic level had a positive effect for most acid-sensitive metrics. Generally, most metrics showed a more non-linear response pattern for the humic lakes than for clear lakes. The significant relationship between these macroinvertebrate metrics and acidification shows that there is a potential for developing further the assessment systems for ecological quality of lakes based on these metrics, although the metrics explained a low % of the variation (<30%). In order to improve the predictive power of the biotic metrics across the acidified part of Europe, further harmonization and standardisation of sampling effort and taxa identification are needed. |
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Keywords: | Acidification indices Generalised additive regression models (GAM) Humic content Littoral macroinvertebrates pH Water Framework Directive |
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