R.C. Nijboer

The Effect of Taxonomic Resolution on the Assessment of Ecological Water Quality Classes

Within the ecological assessment of running waters based on benthic macroinvertebrates different levels of taxonomic resolution (species, genus, family and higher) are in use. Although assessment systems are often developed with detailed data on species level, water managers and other end-users could like to use data on higher taxonomic levels to assess the ecological quality of a water body because of limited human or money resources. The question that arises is, if an assessment system built with species level data is also applicable using data with a higher taxonomic resolution.Within the AQEM project a multimetric assessment system was developed to evaluate the ecological quality classes (from bad (1) to high (5) ecological quality) of different stream types throughout Europe. The present study focuses on the question whether the resulting water quality class changes using the AQEM Assessment Software (AAS) with different taxonomic resolutions and if yes, how large the deviations of ecological quality classes from the original classes are and if the deviations are unidirectional. For analyses data from four Austrian and two Dutch stream types were used.It is demonstrated that the assignment of a site to an ecological quality class may change if different taxonomic levels are used. Deviations in both directions (higher/lower ecological quality class) were observed. In most cases the divergence was only one ecological quality class, but also larger deviations occasionally occurred. The causes of changes in the assessment were investigated by separately looking into the underlying metrics of the multimetric system. Some of the evaluated metrics rely on autecological information on species level and are simply not applicable on higher taxonomic levels. Other metrics worked on higher taxonomic levels as well and showed more or less good distinctions between ecological quality classes.It is concluded that the AQEM Assessment Software is not applicable if data on higher taxonomic levels are used. As the deviations were not unidirectional and ranged from one to three ecological quality classes, it is not possible to include a correction factor for using the software with higher taxonomic resolution data.

Towards a Multimetric Index for the Assessment of Dutch Streams Using Benthic Macroinvertebrates

This study describes the development of a macroinvertebrate based multimetric index for two stream types, fast and slow running streams, in the Netherlands within the AQEM project. Existing macroinvertebrate data (949 samples) were collected from these stream types from all over the Netherlands. All sites received a ecological quality (post-)classification ranging from 1 (bad status) to 4 (good status) based on biotic and abiotic variables, using a combination of multivariate analysis and expert-judgement. A number of bioassessment metrics was tested for both stream types (fast and slow running streams) to examine their power to discriminate between streams of different ecological quality within each stream type. A metric was selected for inclusion in the final multimetric index when there was no overlap of the 25th and 75th percentile between one (or more) ecological quality class(es). Out of all metrics tested, none could distinguish between all four ecological quality classes without overlap of the 25th and 75th percentile between one or more of the classes. Instead, metrics were selected that could distinguish between one (or more) ecological quality class(es) and all others. Finally, 10 metrics were selected for the assessment of slow running streams and 11 metrics for the assessment of fast running streams. Class boundaries were established, to make the assignment of scores to the individual metrics possible. The class boundaries were set at the 25th and/or 75th percentile of the individual metric values. The individual metrics were combined into a multimetric index. Calibration showed that 67% of the samples from slow running streams and 65% of the samples from fast running streams were classified in accordance to their post-classification. In total, only 8% of the samples differed more than one quality class from the post-classification. The multimetric index was validated with data collected in the Netherlands from 82 sites for the purpose of the AQEM project. Validation showed that 54% of the streams were classified correctly.

Macrophyte communities of European streams with altered physical habitat

The impact of altering hydro-morphology on three macrophyte community types was investigated at 107 European stream sites. Sites were surveyed using standard macrophyte and habitat survey techniques (Mean Trophic Rank Methodology and River Habitat Survey respectively). Principal Components Analysis shows the macrophyte community of upland streams live in a more structurally diverse physical habitat than lowland communities. Variables representing the homogeneity and diversity of the physical environment were used to successfully separate un-impacted from impacted sites, e.g. homogeneity of depth and substrate increased with decreasing quality class for lowland sites (ANOVA p < 0.05). Macrophyte attribute groups and structural metrics such as species richness were successfully linked to hydro-morphological variables indicative of impact. Most links were specific to each macrophyte community type, e.g., the attribute group liverworts, mosses and lichens decreased in abundance with increasing homogeneity of depth and decreasing substrate size at lowland sites but not at upland sites. Elodea canadensis, Sparganium emersum and Potamogeton crispus were indicative of impacted lowland sites. Many of the indicator species are also known to be tolerant to other forms of impact. The potential for a macrophyte tool indicative of hydro-morphological impact is discussed. It is concluded one could be constructed by combining indicator species and metrics such as species richness and evenness.

Macrophyte communities in unimpacted European streams: variability in assemblage patterns, abundance and diversity

Macrophytes are an important component of aquatic ecosystems and are used widely within the Water Framework Directive (WFD) to establish ecological quality. In the present paper we investigated macrophyte community structure, i.e., composition, richness and diversity measures in 60 unimpacted stream and river sites throughout Europe. The objectives were to describe assemblage patterns in different types of streams and to assess the variability in various structural and ecological metrics within these types to provide a basis for an evaluation of their suitability in ecological quality assessment. Macrophyte assemblage patterns varied considerably among the main stream types. Moving from small-sized, shallow mountain streams to medium-sized, lowland streams there was a clear transition in species richness, diversity and community structure. There was especially a shift from a predominance of species-poor mosses and communities dominated by liverwort in the small-sized, shallow mountain streams to more species-rich communities dominated by vascular plants in the medium-sized, lowland streams. The macrophyte communities responded to most of the features underlying the typological framework defined in WFD. The present interpretation of the WFD typology may not, however, be adequate for an evaluation of stream quality based on macrophytes. First and most important, by using this typology we may overlook an important community type, which is characteristic of small-sized, relatively steep-gradient streams that are an intermediate type between the small-sized, shallow mountain streams and the medium-sized, lowland streams. Second, the variability in most of the calculated metrics was slightly higher when using the pre-defined typology. The consistency of these results should be investigated by analysing a larger number of sites. Particularly the need of re-defining the typology to improve the ability to detect impacts on streams and rivers from macrophyte assemblage patterns should be investigated.

The effect of excluding taxa with low abundances or taxa with small distribution ranges on ecological assessment

The present study aims to investigate whether taxa with a small distribution range or taxa with low abundances indicate specific habitats or a high ecological quality and what the effect is if these taxa are excluded from ecological assessment. We compared autecological features between stream dwelling taxa with a mean abundance >5 individuals per sample and a mean abundance ≤5 individuals per sample as well as between taxa with a small distribution range and taxa with a large distribution range. The number of rare taxa (either with a small distribution range or with low abundances) in a sample was related to the ecological quality classes. To test the effect of exclusion of rare taxa we constructed 8 data sets all including 142 samples of Dutch lowland streams. From each data set we stepwise excluded taxa that had low abundances or taxa that were known to be restricted in their distribution range. With help of the AQEM assessment software we calculated the final ecological quality classes and the metrics that were included in the multimetric for the original data and the 8 selected data sets.Autecological features of the taxa within the different selections showed that taxa with small distribution ranges were often running water taxa, living on stones and gravel and indicating oligosaprobic water conditions in contrast to taxa that had a large distribution range. There were only small differences between taxa with low and high abundances. However, current velocity preference was lower for taxa with abundance ≤5 individuals per sample, saprobic values were higher and scores for typical stream habitats, such as lithal, psammal and akal were lower compared to high abundant taxa. If taxa with low abundances were excluded a higher ecological quality class was achieved in most cases, while excluding taxa with a small distribution range resulted in lower ecological quality classes. In conclusion, excluding taxa with a small distribution range led to worse ecological quality classes because these taxa have special autecological features that often indicate natural streams. On the other hand, excluding taxa with low abundances resulted in higher ecological quality classes because these taxa indicate more disturbed situations and because the number of taxa per sample was strongly reduced. Although the documentation of rare taxa (either with low abundances or with small distribution ranges) is often time and cost-intensive regarding field work, laboratory work, data processing, and analyses, the indicative power of these taxa for natural circumstances is essential and therefore rare taxa should be included in ecological assessment studies.

Diversity and distribution of Tubificidae, Naididae, and Lumbriculidae (Annelida: Oligochaeta) in the Netherlands: an evaluation of twenty years of monitoring data

Data from 24 water management districts and the rivers Rhine and Meuse in the Netherlands were used to study geographical distribution, relative occurrence, and environmental requirements of 76 aquatic oligochaetes (families Tubificidae, Naididae, and Lumbriculidae) (Annelida, Clitellata). Approximately 50% of the 76 species that occur in the Netherlands are uncommon, rare, or very rare. The other half of the species are common, very common or abundant. The abundant species are: Stylaria lacustris, Ophidonais serpentina, Limnodrilus claparedeianus, Limnodrilus hoffmeisteri, and Lumbriculus variegatus. With the exception of several brackish water species (those restricted in distribution to water management districts close to the sea that are influenced by salt water influx) and specific running water species (restricted mainly to the eastern part of the Netherlands), most of the species occurred throughout the whole Netherlands. The species distribution was related to environmental variables using ordination. In general, species distribution was correlated with either large waters with high chloride and phosphorus concentrations and a high hydrogen ion concentration (as pH), or with small forested (running) waters in more natural (undeveloped) areas that occasionally become intermittent. Vegetation cover was positively correlated with several swimming species in the family Naididae. While the distribution of aquatic oligochaetes in some families occurring in the Netherlands is known to some extent, the occurrence and distribution of rare and small taxa, particularly those that are difficult to identify taxonomically, is virtually unknown. Some of the rare oligochaete taxa, especially those associated with unique habitats, have received only cursory attention. Also in the data studied, the observations of the more rare species were too few to draw conclusions. To improve our knowledge of oligochaete distribution in the Netherlands, additional research should focus on rare species associated with special habitats and water types (natural areas) and those taxa in poorly known families. The standardisation of sampling and processing methodologies, particularly the use of nets and sieves with fine-meshed screening, will ensure the collection of the smaller species of oligochaetes. Subsequently, oligochaetes should be identified to species level by experienced taxonomists trained in oligochaete identification. Finally, many aquatic oligochaete species are identifiable only when sexually mature and therefore the time of year in which samples are collected is critical to the accurate representation of true oligochaete diversity at any given site. For analysing the relation between species and environmental variables the best option is to use composite data from spring and autumn.

Rare and common macroinvertebrates: definition of distribution classes and their boundaries

Rarity of macroinvertebrates can be used in assessing the ecological quality or conservation value of freshwaters. To select target species for nature conservation and to compare rarity or commonness between regions a classification of species distributions is needed. A distribution classification for Dutch macroinvertebrate taxa is presented. Frequencies of occurrence in surface waters of aquatic macroinvertebrate taxa were extracted from databases of water district managers and included data from 7608 sites from 1980 to 1998. Six classes were defined: very rare, rare, uncommon, common, very common, and abundant. The boundaries for these classes were established using the number of occurrences of the taxa and the expert opinion of a committee of water district managers and taxonomic experts. A distribution class was assigned to each of 1544 taxa, including 1514 species and 30 taxa on higher taxonomic level (groups, aggregates, genera). There were still many taxa for which the distribution was unknown due to their small size, their special habitat requirements, or identification difficulties due to immature animals and incomplete taxonomic information. The number of rare species differed between the 24 water management districts and depended on characteristics of the area, sampling strategy, and sampling intensity. The percentage of rare species differed between taxonomic groups. The definition of distribution classes and their boundaries can be applied at different scales, (e. g., water management district or national scale), which makes results comparable between scales and provides a broad application in bioassessment and conservation.

Taxonomic adjustment affects data analysis: an often forgotten error

Macroinvertebrate assemblages are often used in water assessment and water management. (e.g. ARMITAGE et al. 1983, }OHNSON & WIEDERHOLM 1989, REAL et al. 1993, NIJBOER & VERDONSCHOT 1998}. Macroinvertebrate taxa are grouped and related to environmental conditions. By including all taxa to describe assemblages, inter-species relationships may be taken into account. One of the techniques used for constructing assemblages is duster analysis, whereby groups of samples (dusters} that have a comparable species composition are identified. Results of dustering are combined with ordination results to relate clusters to environmental factors (VERDONSCHOT & NIJBOER 2000}. The data set should be consistent to ensure that duster results are unambiguous (GAUCH 1982, JoNGMAN et al. 1987}. This means no taxa may overlap, because taxonomic overlap results in a multiplication of the same information in a sample. Taxonomic overlap can also result in artificial differences between samples. Table l shows an example of an inconsistent data set. Some specimens were identified to the genus Gammarus and other specimens were identified to G. fossarum and G. pulex. Both genus and species occur in more than one third of the samples. The same problem exists in the family Tubificidae, but in this group the species are less abundant. lnconsistency of a data set can be caused by: different sampling and sorting techniques; seasonal variation; early larval instars that are difficult to identify; • limited taxonomic knowledge about certain groups; • use of different identification keys; • availability of specialists for identification. lnconsistent data need to be identified and removed from the data set before analysis. Either the species or the higher taxon (genus or family) should be skipped if they are both present. However, skipping higher taxa can lead to a loss of groups, especially in samples in which no species of Table l. Example of an inconsistent data set. The table shows the numbers of occurrences and of individuals for the genus Gammarus and the family Tubificidae. Taxon Numberof Numberof occurrences individuals Gammarus sp. 30 5360 G.pukx 29 8347 G.fossarum Tubificidae 38 8021 Tubifex tubiftx 16 2113 Potamotrix hammoniemis 145 Ilyodrilus templetoni 4 39 Aulodrilus limnobius 3 133 A. pluriseta 9 215 Rhyacodrilus coccineus 2 19

Aquatic Oligochaete Biology VIII

Three species of the oligochaete ge nus Pristina (Nai didae, Clitellata) , one of them new to sc ience, are described from so il and litte r samples orig ina ting fro m terra firme sites of the pr ima ry rain fores t at the Brazili an Agroforestry Research Fac ility in Ce ntra l Amazonia : P. marcusi sp. nov., P. j enkina e (Stephenso n, 1931 ) and P. no topora Cernosvitov, 1937 . Investigat ion s were ca rrie d out on live and preserved material, with emphasis on non-chaetal , nonsexual characters of the live anatomy, usually neglected in recent Naididae taxonom y. P. marcusi sp. nov. is characterized by simple-pointed and bayonet-shaped needle chaetae and by a regul ar pattern of ellip soid intrastomachal cavi ties . P. notopora is redescri bed in full detail for the first time since its original description , incl uding the exceptiona l dorsal opening of the nephridia.