Austrian Index Macrophytes (AIM-Module 1) for lakes: a Water Framework Directive compliant assessment system for lakes using aquatic macrophytes |
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Authors: | Karin Pall and Veronika Moser |
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Institution: | (1) Systema GmbH, Bensasteig 8, 1140 Vienna, Austria |
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Abstract: | We describe a new macrophyte-based assessment tool for Austrian lakes elaborated according to the requirements of the European
Water Framework Directive. Data from 38 out of 45, WFD-relevant (≥50 ha) lakes in Austria collected with the help of a new
mapping procedure form the basis for a macrophyte-based lake typology and the definition of reference conditions. Module 1
of the Austrian Index Macrophytes (AIM) focuses on the assessment of trophic state and general impairment of lakes. Several
metrics were developed and applied in combination with existing indices to classify lakes into five ecological status classes.
The metric “vegetation density” focuses on the overall abundance of macrophytes. Since the lower limit of the macrophyte vegetation
in lakes is mainly regulated by the water transparency, the metric “vegetation limit” is closely related to the trophic state
of the lake. In deep lakes, macrophytes normally form different vegetation zones. As a result of alteration of the shoreline,
artificial water level fluctuations or wave action and even eutrophication, specific zones can be missing. The metric “characteristic
zonation” helps to check, if all type-specific vegetation zones are present. The metric “trophic indication” uses the Macrophyte
Index after Melzer (Hydrobiologia, 395/396: 181–190, 1999). This term indicates the lake trophic state but, in contrast to the metric “vegetation limit”, it tends to show not only
the trophic state of the water column but also, in particular, the nutrient conditions in the sediment. With the help of the
metric “species composition,” the species spectrum and the species abundances of the current transect are compared with the
species composition at reference sites. The similarity of the datasets is measured as Bray–Curtis Distance (Beals, Advances
in Ecological Research, 14: 1–55, 1984). The established metrics cover different aspects of macrophyte vegetation and allow analysing the prevailing pressure. Since
the different metrics have a different temporal response to eutrophication and reoligotrophication, additional information
on the current state of the lake in relation to these processes can be derived. The successful application of AIM-Module 1
is presented for two Austrian lakes and discussed in relation to other assessment tools.
Guest editors: P. N?ges, W. van de Bund, A.C. Cardoso, A. Solimini & A.-S. Heiskanen
Assessment of the Ecological Status of European Surface Waters |
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Keywords: | Water Framework Directive Macrophytes Lakes Water quality Mapping method Assessment system |
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