Submerged macrophyte vegetation and the European Water Framework Directive: assessment of status and trends in shallow,alkaline lakes in the Netherlands |
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Authors: | H Coops F C M Kerkum M S van den Berg I van Splunder |
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Institution: | (1) Institute for Inland Water Management and Wastewater Treatment (RIZA), P.O. Box 17, 8200 AA Lelystad, The Netherlands |
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Abstract: | The submerged macrophyte vegetation of lakes created after enclosing former estuaries, situated in the central and south-western
part of the Netherlands, has been monitored annually from 1992 onwards. Between 1992 and 2004, pronounced changes in overall
cover and species composition of the submerged vegetation have occurred, resulting from changes of water quality and morphology
in the lakes. In most cases vegetation cover and species diversity increased or remained stable, with the exception of two
lakes in the southwest part of the country. Abundance and species composition were assessed according to the requirements
of the EU Water Framework Directive, using the assessment procedure proposed to assess macrophytes in natural water bodies
in the Netherlands. The assessment procedure included calculation of the ‘ecological quality ratio’ (EQR) for each of eleven
water bodies in each of 13 years, based on transect monitoring data. The EQR indicating Good Ecological Status for Macrophytes
was achieved in only three of the lakes. The consequences of hydromorphological modifications, and measures necessary to achieve
the desired condition are discussed. Nutrient concentrations should be reduced further, while additional management measures
are necessary to improve conditions for macrophytes. |
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Keywords: | Assessment Biological monitoring Submerged macrophytes Water Framework Directive |
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