Evaluation of European diatom trophic indices

doi:10.1016/j.ecolind.2010.06.017

Ecological Indicators

Volume 11, Issue 2, March 2011, Pages 456-467

https://doi.org/10.1016/j.ecolind.2010.06.017 Get rights and content

Abstract

Freshwater diatoms are considered to be reliable indicators of the trophic status of rivers and lakes. In the past 30 years, a number of indicator indices have been developed and used for the assessment of trophic conditions all over Europe. It is however still not clear whether the ecologic signature of diatoms differs between these indicator indices. The present study assessed a large number of published European indices on the response of freshwater diatoms to trophic conditions by evaluating the consistency in the use of taxa and their trophic score from seven European indicator indices. The STAR (Standardisations of River Classifications) diatom database, a large set of samples from European running waters, was used to test the application of trophic classifications in water quality assessment. The analysis of taxa in common within the trophic indices showed that there are considerable differences between the indices, for example in the score of trophic values. There was more agreement in classification of taxa within the oligotrophic and the hypertrophic preferences than within the mesotrophic range. Based on these results, a list of diatom taxa, that are consistently used in different trophic indices, was composed. It included 159 ‘reliable’ taxa that are not sensitive to regional setting, water type and taxonomic uncertainty. The list was further accompanied by a description of the taxa's trophic preferences. The large deviation in trophic scores for a number of diatom taxa could most probably be explained by taxonomic uncertainties. Application of these taxa for trophic assessment was questionable. The test set of the 359 STAR samples showed that differences between the trophic indices also lead to a significant variation in the water quality assessment results. Although trophic indices provide an excellent biomonitoring tool, they should be applied with caution, considering the recommendations provided in this paper.

Introduction

Trophic conditions are one of the most important determining factors influencing the freshwater diatom communities in rivers and lakes (Harper, 1992). The reliability of diatoms as indicators of the trophic conditions in aquatic environments has been demonstrated in multiple studies (Pan and Lowe, 1994, Pan et al., 1996, Potapova and Charles, 2007, Stevenson and Pan, 1999; see also Whitton and Rott, 1996). With the increasing eutrophication of European aquatic environments, the number of indicator indices used for the assessment of trophic conditions has risen. These indicator indices were developed independently for both lotic and lentic ecosystems, more often originated from regional datasets, and served mostly as basis for regional water quality assessment [Coring et al., 1999 (Germany); Hofmann, 1994, Hürlimann and Niederhauser, 2002 (Switzerland); Kelly and Whitton, 1995 (UK); Rott et al., 1999 (Austria); van Dam et al., 1994 (The Netherlands)]. The software package Omnidia (Lecointe et al., 1993) includes some 30 diatom indices and accompanying lists of taxa with ecological scores and is often used to assess water quality in various geographical regions assuming the cosmopolitan nature of diatoms. In some cases, users adjust the indices by incorporating new or corrected autecological information to apply in their specific region (A. Jarlman, pers. comm.).

The large variation in indicator indices also caused confusion and arbitrariness among researchers performing quality assessments. It is unclear whether there are significant differences between the results of the indices, and if so, what these differences are and what causes this variation. On the one hand, the cosmopolitan nature of diatoms should display a constant trophic preference. On the other hand, primarily in studies from the North America, it has been shown that European indicator indices may need to be calibrated to regional conditions (e.g. Fore and Grafe, 2002, Potapova and Charles, 2007). Moreover, a number of European phycologists argued that indices developed in certain regions of Europe were not effective in others (Kelly et al., 1998, Pipp, 2002, Rott et al., 2003).

In this study, we tested the causes of variation between trophic diatom indicator indices by mutually comparing individual species’ trophic scores. We extracted a common trophic preference score list to be used in a wide geographical area based on consistent species scores derived from different indices. We evaluated trophic diatom scores and the consistency of indicator indices results by applying them on a large set of samples from European running waters. As a result, we determined a list of recommendations to be applied in order to get a more objective and consistent diatom-based trophic evaluation.

Section snippets

Rescaling the indices

The Diatom Indicator Database version 3.2 (http://www.freshwaterecology.info) was developed within the EU Eurolimpacs project and represents the state-of-the-art knowledge of the ecological response of diatom taxa to climate change. It contains 17 trophic diatom indices originating from studies in running and standing freshwaters throughout different ecoregions in Europe and outside. The Diatom Indicator Database uses a standardised taxonomic diatom list (CEMAGREF taxa list, updated version May

Rescaling the indices

Trophic scores were more consistent for the indices GM B&O, GM Seen and Rott when based on phosphorus ranges. When based on word descriptions, trophic scores were more consistent for the indices Trophy D, TDI, Hoffmann and van Dam. The scale originally used to construct an index, phosphorus ranges or word descriptions, decides these results, with the exception of TDI since it had broader scale boundaries (Appendix 1).

Consistency of index scores

Two groups of indices, with on average a mutual similarity higher or lower

Discussion

The similarity in taxonomic composition of the trophic indices correlated to the origin of the underlying data. The indices of group 2 (Rott, TDI, van Dam, Hofmann) were obtained from the Omnidia program, whereas those of group 1 (GM B&O, GM Seen, Trophy D) were extracted from the original papers. Taxonomic correctness and consistency is crucial for any comparison or assessment. All taxa were converted to a common taxon list. Group 1 taxa were converted to the most recent specific level

Conclusions and recommendations

Despite the upscaling of the seven trophic indices to a common reference scale, the trophic assessment results varied significantly. A detailed comparison of the autecological information between the indices revealed a difference in both composition of the taxonomic lists and of the trophic scores of diatom taxa. Common valid taxonomy has up to now been a practical barrier for comparison studies. A first step would be to accompany new water quality indicator indices by taxonomic notes and a

Acknowledgements

This paper is a result of the EU-funded project Eurolimpacs (6th Framework Programme; contract number: GOCE-CT-2003-505540). Prof. Luc Ector, Mrs. Amelie Jarlman and Dr. Martyn Kelly are thanked for stimulating discussions. We also thank Mr. Martin van den Hoorn and Mr. Jos Sinkeldam for technical assistance in processing the data. The comments of two anonymous reviewers greatly improved the manuscript.

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Original articleEvaluation of European diatom trophic indices

Abstract

Introduction

Section snippets

Rescaling the indices

Rescaling the indices

Consistency of index scores

Discussion

Conclusions and recommendations

Acknowledgements

Protist

Ecol. Indic.

Ecol. Indic.

Taxonomy and ecology of characteristic Eunotia species in headwaters with low electric conductivity

Nov. Hedw.

Rapid Bioassessment Protocols for Use in Streams and Wadeable Rivers, Periphyton, Benthic Macroinvertebrates, and Fish

Güteklassenbezogene Zielvorgaben zur Nährstoffreduzierung im Berliner Gewässersystem

Ber. IGB

A habitat matrix conceptual model for stream periphyton

Archiv. Hydrobiol.

Guilds of benthic algae along nutrient gradients, relationships to algal community diversity

J. N. Am. Benthol. Soc.

Large-scale regional variation in diatom–water chemistry relationship, rivers of the eastern United States

Hydrobiologia

Durchgehendes Trophiesystem auf der Grundlage der Trophieindikation mit Kieselalgen

Using quantitative PCR to determine the distribution of a semicryptic benthic diatom, Navicula phyllepta (Bacillariophyceae)

J. Phycol.

Calibration of littoral diatoms to water chemistry in standing fresh waters Flanders, lower Belgium, inference models for historical sediment assemblages

J. Paleolim.

Algal periphyton growth on nutrient-diffusing substrates, an in situ bioassay

Ecology

Using diatoms to assess the biological condition of large rivers in Idaho (USA)

Freshw. Biol.

The ecological status of European rivers: evaluation and intercalibration of assessment methods

Hydrobiologia

The STAR project, context, objectives and approaches

Hydrobiologia

Eutrophication of Freshwaters

Aufwuchs diatoms in Seen und ihre Eignung als Indikatoren der Trophie

Bibl. Diat.

Méthode d’analyse et d’appréciation des cours d’eau en Suisse, Diatomées, niveau R région

Limnofauna Europaea

The trophic Diatom Index, a new index for monitoring eutrophication in rivers

J. Appl. Phycol.

Recommendations for the routine sampling of diatoms for water quality assessments in Europe

J. Appl. Phycol.

Littoral diatoms as indicators for the eutrophication of shallow lakes

Hydrobiologia

Süsswasserflora von Mitteleuropa. Bacillariophyceae 2. teil. Bacillariaceae, Epithemiaceae, Surirellaceae

New species, combinations and synonyms in the genus Nitzschia

Bacillaria

A first “Red List” of endangered taxa in the diatom flora of Germany and of Central Europe – interpretation and comparison

Original article
Evaluation of European diatom trophic indices