Water quality indices across Europe—a comparison of the good ecological status of five river basins

Abstract

The European Water Framework Directive (WFD) requires the definition of near-natural reference conditions to determine the extent of water bodies' deviation from "good ecological status" caused by stress gradients. However, the classification of ecological quality depends on the assessment method applied and the stressor concerned. While assessment methods that are generally applicable would be favourable, many European countries employ the locally developed water quality metrics that assess the impact of organic pollution (including eutrophication) and the associated decrease in dissolved oxygen. These indices do not specifically address stress from organic toxicants, such as pesticides. The aim of this study was to examine the performance of presently used assessment methods to identify reference conditions of non-contaminated streams in five selected European river basins, covering the geographical region from Spain to Finland, as a crucial prerequisite to indicate toxic gradients. The analysis comprised the Belgium biotic index (BBI), the biological monitoring working party (BMWP) scoring system and the revised German saprobic index. For comparison, we included an adaptation of the recently developed SPEAR index. In two previous field studies, this metric highly correlated with measured pesticide gradients. In this study, SPEAR was the only indicator that was generally applicable to all monitoring data and capable of determining "high ecological status" of reference conditions in all basins. Thus, based upon previous and own results, the authors suggest the species at risk (SPEAR) index to be potentially useful as a European-wide index to address deviations from "good ecological status" due to organic toxicants and recommend it for consideration in integrated water-resource evaluations under the WFD.

Method of predicting reference condition biota affects the performance and interpretation of ecological indices

“…No single ecological index developed to date completely captures all the varied ecological responses that natural assemblages exhibit to human‐caused stress (e.g. von der Ohe et al. , 2007), but probing index behaviour in as many ways as possible should go far towards allowing practitioners to see the whole ‘elephant’ of ecological condition and promote the selection of indices based on well‐understood ecological and statistical properties.…”

A catchment scale evaluation of multiple stressor effects in headwater streams

“…For six of the sites, the %SPEAR pesticides abundance was even below 10 suggesting a very strong impact of pesticides on the macroinvertebrate communities. Among the previous studies reporting SPEAR values from 112 different streams from different locations in the world (primarily headwater streams), less than 10% of the sites were characterised by %SPEAR pesticides values below 10 (compare McKnight et al, 2012;Rasmussen et al, 2012;Schletterer et al, 2010;Schäfer et al, 2007;2011;von der Ohe et al, 2007). Despite much weaker correlations with the DCA axis scores, other qualitative indicators of ecological quality (EPT abundance, DSFI and LIFE scores) all obtained very low values indicating strong ecological impairment in the studied headwater streams.…”

Utility of environmental DNA for monitoring rare and indicator macroinvertebrate species

“…We chose species that live in rivers and lakes and are either rare or belong to indicator groups used for waterquality assessment in the study area (von der Ohe et al 2007). We chose species that had been detected in the study area by the conventional biodiversity monitoring conducted by the Office of Waste, Water, Energy, and Air (WWEA/AWEL) of the Canton of Zurich over the years 1995(AWEL 2012 and were known to be part of the regional species pool.…”