Establishing Reference Conditions for European Streams

Summary 1. International river catchments pose challenges for effective water resource management. Catchment‐wide strategies are often complicated by differences in national bioassessment and quality classification. Intercalibration efforts aim to harmonise these differences, but rely on the consistent delineation of near‐natural reference sites that are almost unavailable in today’s landscape, especially for large rivers. 2. We introduce the concept of alternative benchmarking that is based on the notion of aquatic communities at similar (low) levels of impairment associated with least‐disturbed conditions (LDC) as defined by abiotic criteria. Using data acquired during the second Joint Danube Survey, we defined LDC sites based on a multivariate gradient of anthropogenic pressures, mostly related to morphological deterioration, that spans the entire navigable Danube. 3. The river was subdivided into four stretches, each featuring homogeneous biological assemblages. Indirect gradient analysis revealed relationships between the pressure gradient and selected features of the macroinvertebrate and macrophyte community but not for diatoms or phytoplankton. 4. We identified biological metrics suitable for the quality classification of individual stretches or the entire river. Impoundment is the major hydromorphological alteration on the Danube but various metrics still responded significantly to differences in the morphological condition of sites not affected by impoundment. 5. A comparison of macroinvertebrate sampling techniques (airlift versus kick‐and‐sweep) revealed differences in how the acquired data reflect the effects of anthropogenic pressure. Biological metrics based only on kick‐and‐sweep sample data were insensitive to habitat deterioration in the heavily modified Upper Danube. 6. This study exemplifies the empirical approach of alternative benchmarking in intercalibration and offers practical solutions to some of the challenges of large river bioassessment.

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“…Nijboer et al, 2004;Baattrup-Pedersen et al, 2009). Nijboer et al, 2004;Baattrup-Pedersen et al, 2009).…”

Section: Key Principles Of Alternative Benchmarkingunclassified

Harmonising the bioassessment of large rivers in the absence of near‐natural reference conditions – a case study of the Danube River

Birk

Kouwen²,

Willby

2012

Freshwater Biology

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“…However, various difficulties have been faced in fulfilling this task (Carletti and Heiskanen, 2009;Willby et al, 2014). All currently used metrics and indexes were developed based on information gathered from previous investigations, modelling, literature, expert judgement, or a combination of these (Nijboer et al, 2004;Carletti and Heiskanen, 2009). The EU WFD requires that the boundaries between the ecological quality classes should be verified through intercalibration exercises (European Commission, 2000).…”

Section: Discussionmentioning

confidence: 99%

Testing and development of different metrics and indexes describing submerged aquatic vegetation for the assessment of the ecological status of semi-enclosed coastal water bodies in the NE Baltic Sea

Torn

Martin²,

Rostin³

2014

Estonian J. Ecol.

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A national assessment system for the classification of the ecological status of coastal waters according to the requirements of the EU Water Framework Directive was established in Estonia in the year 2007. The Estonian Phytobenthos Index was used to assess the ecological status of coastal waters based on submerged aquatic vegetation. After the testing period it appeared that the selected method did not respond to anthropogenic pressure in two national water types: the Väinameri and Pärnu Bay. During this study new indexes were developed and validated against pressure for these areas. The PCF index was combined from the proportion of perennial species, charophytes, and Fucus spp. This index is suitable for the assessment of the ecological status in the Väinameri area. In Pärnu Bay the depth distribution of higher plants and the proportion of opportunistic species showed the strongest correlation with eutrophication variables. These metrics were combined into the HPO index. The class boundaries for assessing the ecological status of water quality were determined for both indexes. The paper describes the calculation of the indexes.

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“…This has a very good explanation: the reference criteria for physicochemical, hydromorphological and pressure criteria cannot be fulfilled (Wallin, Wiederholm & Johnson ) when applied in the lowlands (Nijboer et al . ; Chaves et al . ; Baattrup‐Pedersen et al .…”

Section: Introductionmentioning

confidence: 99%

A new paradigm for biomonitoring: an example building on the Danish Stream Plant Index

et al. 2016

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Summary Despite intensive efforts for more than a decade to develop Water Framework‐compliant assessment systems, shortcomings continue to appear. In particular, the lack of reference conditions has hindered the development of assessment systems capturing the heart of the Water Framework Directive (WFD) – that ecological status should be set as the deviation from the natural, undisturbed condition. Recently, the Danish Stream Plant Index (DSPI) was developed. This system contrasts existing systems in that it builds on an expert interpretation of the normative definitions of ecological status classes in the WFD without taking pressure–impact relationships into account. Here, we substantiate the approach taken in the development of DSPI and examine whether the DSPI class decreases with increasing level of anthropogenic stress and, additionally, whether the deviation from the natural undisturbed condition increases with decreasing DSPI class sensu WFD using trait composition of plant assemblages from Danish streams around year 1900 as a reference. We furthermore examine the trait composition of the vegetation in sites classified into different DSPI status classes to explore whether predictable patterns exist that can be used to identify the ultimate cause(s) of failure to meet ecological goals and help guide the selection of appropriate mitigation measures. We observed that DSPI declined with several parameters indicative of environmental stress in Danish streams and, furthermore, that the deviation from the natural undisturbed condition regarding the trait composition of plant communities declined with increasing DSPI, implying that the trait composition of plant communities in the high DSPI status class was most similar to those occurring in Danish streams around year 1900. We also found that trait characteristics capable of disentangling important stressors in Danish streams varied consistently among sites classified into different DSPI classes. Based on our findings, we call for new thinking. We suggest that more effort should be directed at describing reference conditions and interpreting the normative definitions of good, moderate, poor and bad instead of focusing solely on developing assessment systems using pressure–impact frameworks. We find this particularly important with respect to streams as these are seldom impacted by only a single stressor.

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Establishing Reference Conditions for European Streams

Cited by 29 publications

References 14 publications

Harmonising the bioassessment of large rivers in the absence of near‐natural reference conditions – a case study of the Danube River

Harmonising the bioassessment of large rivers in the absence of near‐natural reference conditions – a case study of the Danube River

Testing and development of different metrics and indexes describing submerged aquatic vegetation for the assessment of the ecological status of semi-enclosed coastal water bodies in the NE Baltic Sea

A new paradigm for biomonitoring: an example building on the Danish Stream Plant Index

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