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Papers by Ursula Riedmüller

Hydrobiologia, Jul 29, 2009

The intercalibration (IC) exercise is a key element in the implementation of the Water Framework ... more The intercalibration (IC) exercise is a key element in the implementation of the Water Framework Directive (WFD) in Europe. Its focus lies on the harmonization of national classification methods to guarantee a common understanding of 'Good Ecological Status' in surface waters. This paper defines reference conditions and sets class boundaries for deep (mean depth >15 m, IC lake type L-AL3) and moderately deep (mean depth 3-15 m, IC lake type L-AL4) Alpine lakes >0.5 km 2. Data were collated from each of the five EU member states included in the Alpine Geographical Intercalibration Group (Alpine GIG: Austria, France, Germany, Italy and Slovenia). Hydro-morphological, chemical and biological data from 161 sites (sampling stations) in 144 Alpine lakes over a period of seven decades were collated in a database. Based on a set of reference criteria, 18 L-AL3 and 13 L-AL4 reference sites were selected. Reference conditions were defined using a combined approach, based on historical, paleolimnological and monitoring data in conjunction with trophic modelling and expert judgement. Reference values and class boundaries were set for annual mean total biomass (biovolume), and then derived for annual mean chlorophyll-a using a regression between the two parameters. To allow for geographical differences within the Alpine GIG and to facilitate the inclusion of the broadly defined common IC types and national lake types, ranges were defined for each reference value. Range of reference values are 0.2-0.3 mg L-1 (L-AL3) and 0.5-0.7 mg L-1 (L-AL4) for total biovolume and 1.5-1.9 µg L-1 (L-AL3) and 2.7-3.3 µg L-1 (L-AL4) for chlorophyll-a. Depending on lake type and variable, the ecological quality ratios (EQR) for setting the class boundaries lie between 0.60 and 0.75 for the high/good class boundary and between 0.25 and 0.41 for the good/moderate class boundary. The response of sensitive phytoplankton taxa along a nutrient gradient and the occurrence of 'undesirable conditions and secondary effects' as defined in the WFD was used to validate the class boundary values, which are thus considered to be compliant with the requirements of the WFD.

Environmental Management, Apr 18, 2010

The concept of ''reference conditions'' describes the benchmark against which current conditions ... more The concept of ''reference conditions'' describes the benchmark against which current conditions are compared when assessing the status of water bodies. In this paper we focus on the establishment of reference conditions for European lakes according to a phytoplankton biomass indicator-the concentration of chlorophyll-a. A mostly spatial approach (selection of existing lakes with no or minor human impact) was used to set the reference conditions for chlorophyll-a values, supplemented by historical data, paleolimnological investigations and modelling. The work resulted in definition of reference conditions and the boundary between ''high'' and ''good'' status for 15 main lake types and five ecoregions of Europe: Alpine, Atlantic, Central/Baltic, Mediterranean, and Northern. Additionally, empirical models were developed for estimating site-specific reference chlorophyll-a concentrations from a set of potential

Natürliche, künstliche und erheblich veränderte Mittelgebirgsseen, calciumreich, relativ kleines ... more Natürliche, künstliche und erheblich veränderte Mittelgebirgsseen, calciumreich, relativ kleines Einzugsgebiet, geschichtet 6.1 Natürliche, künstliche und erheblich veränderte Mittelgebirgsseen, relativ kleines Einzugsgebiet, polymiktisch 6.2 Natürliche, künstliche und erheblich veränderte Mittelgebirgsseen, mäßig großes Einzugsgebiet, polymiktisch 6.3 Natürliche, künstliche und erheblich veränderte Mittelgebirgsseen, relativ großes Einzugsgebiet, polymiktisch 8 Natürliche, künstliche und erheblich veränderte Mittelgebirgsseen, calciumarm, relativ großes Einzugsgebiet, geschichtet 9 Natürliche, künstliche und erheblich veränderte Mittelgebirgsseen, calciumarm, relativ kleines Einzugsgebiet, geschichtet 10.1

Ó The Author(s) 2010. This article is published with open access at Springerlink.com Abstract The... more Ó The Author(s) 2010. This article is published with open access at Springerlink.com Abstract The concept of ‘‘reference conditions’ ’ describes the benchmark against which current conditions are compared when assessing the status of water bodies. In this paper we focus on the establishment of reference conditions for European lakes according to a phytoplankton biomass indicator—the concentration of chlorophyll-a. A mostly spatial approach (selection of existing lakes with no or minor human impact) was used to set the reference conditions for

Die vorliegende Verfahrensbeschreibung enthält alle Änderungen, die mit dem LAWA-Expertenkreis fü... more Die vorliegende Verfahrensbeschreibung enthält alle Änderungen, die mit dem LAWA-Expertenkreis für Seen bis Dezember 2016 abgestimmt wurden und folgende Überarbeitungsbereiche betreffen: 1) Es erfolgte eine erhebliche Verfahrenserweiterung für Seen im Mittelgebirge sowie für künstliche und stark veränderte Seen (AWB und HMWB), worunter unter anderem die Talsperren und die Baggerseen fallen. Nach einem ersten Verfahrensentwurf (Hoehn et al. 2009) wurden die Bewertungsgrenzen sowie die Seetypologie nach den Ergebnissen eines Praxistestes der Bundesländer stark überarbeitet (Riedmüller & Hoehn 2011). 2a) Es wurden die Grenzwerte für die Kenngröße "Biomasse" an die Grenzwerte für die Trophiestufen des neuen Trophie-Index nach LAWA (2014) angepasst. 2b) Wie im Trophie-Index nach LAWA wurden alle Saisonmittel im PSI auf ein direktes Mittel aus den Termindaten umgestellt und nicht mehr wie bisher über den Umweg von Monatsmitteln. Dies betrifft auch den PTSI-Jahreswert. 3) Für die...

author-produced version of the final draft post-refeering the original publication is available at

Leibniz-Institut für Gewässerökologie und Binnenfischerei, 2016

One of the key actions identified by the Water Framework Directive (WFD; 2000/60/EC) is to develo... more One of the key actions identified by the Water Framework Directive (WFD; 2000/60/EC) is to develop ecological assessment tools and carry out a European intercalibration (IC) exercise. The aim of the Intercalibration is to ensure that the values assigned by each Member State to the good ecological class boundaries are consistent with the Directive’s generic description of these boundaries and comparable to the boundaries proposed by other MS. In total, 83 lake assessment methods were submitted for the 2nd phase of the WFD intercalibration (2008-2012) and 62 intercalibrated and included in the EC Decision on Intercalibration (EC 2013). The intercalibration was carried out in the 13 Lake Geographical Intercalibration Groups according to the ecoregion and biological quality element. In this report we describe how the intercalibration exercise has been carried out in the Central Baltic Lake Phytoplankton IC group.

Environmental Management, 2010

Handbuch Angewandte Limnologie: Grundlagen - Gewässerbelastung - Restaurierung - Aquatische Ökotoxikologie - Bewertung - Gewässerschutz, 2004

This chapter describes the revised method to assess lakes based on phytoplankton in accordance wi... more This chapter describes the revised method to assess lakes based on phytoplankton in accordance with the proposal by Mischke et al. (2008) and corresponds to Chapter 3 of the German report. The German phytoplankton-based assessment system for lakes yields a multi-metric index value, the Phyto-See-Index (PSI), and differentiates between different lake types. It classifies water bodies into one of five status classes in accordance with the Water Framework Directive (WFD). The PSI consists of three mandatory metrics: "biomass", "algal classes" and the "Phytoplankton-Taxa-Seen-Index" (PTSI). A step-by-step calculation of the German PSI is included. The first proposal (Nixdorf et al. 2005b) was extensively modified in response to the outcome of both a national exercise and the European intercalibration exercise. This chapter will serve as the basis for a final publication in the form of a manual on the German system for phytoplankton-based assessment of lakes...

Hydrobiologia, 2009