Jürgen Böhmer

Assessing streams in Germany with benthic invertebrates: selection of candidate metrics.

Abstract The process of selecting invertebrate-based candidate metrics for the German stream assessment system is described. The aim was to identify metrics indicating degradation types other than organic pollution and acidification (“general degradation”). For 18 out of 24 German stream types a data base of roughly 2,000 benthic invertebrate samples was generated; for each sample 79 metrics were calculated. Data on land use in the catchment were compiled for all sampling sites, together with data on hydromorphology for many sampling sites. Hydromorphological and land use parameters, which describe a clear gradient in the data sets were identified by Non-metric Multidimensional Scaling (NMS). Correlation analyses between land use/hydromorphological parameters and metric results were calculated separately for the individual stream types. Among those metrics best indicating catchment- and hydromorphological degradation in the majority of stream types are: proportion of Ephemeroptera, Plecoptera and Trichoptera; proportion of Plecoptera (mainly suited for mountain streams); number of Plecoptera taxa; proportion of xenosaprobic taxa; proportion of epirhithral preferring taxa. Differences of metric correlations between stream types and between degradation types are discussed, leading to a list of candidate metrics for assessing German streams.

Macroinvertebrate functional feeding group methods in ecological assessment

Six functional feeding group (FFG) indices applied in ecological assessment were tested for their accuracy in detecting impairment in 12 cases of disturbance on 11 streams in south-western Germany. Three metrics — percentage of predators, percentage of shredders and Rhithron-Ernahrungstypen-Index RETI — performed well in small highland streams up to five m width. The FFG metrics were compared to the taxonomic measures ‘percentage of Chironomidae’ and ‘percentage of ephemeropteran, plecopteran and trichopteran taxa’ (EPT) used the USA, and to a metric based on locomotion type (percentage of sessile taxa). As the implementation of such metrics implies the use of ecological data tables, some aspects of the pro and contra of European ecological lists published in recent years were critically assessed.

Ecological status assessment of European lakes: a comparison of metrics for phytoplankton, macrophytes, benthic invertebrates and fish

Data on phytoplankton, macrophytes, benthic invertebrates and fish from more than 2000 lakes in 22 European countries were used to develop and test metrics for assessing the ecological status of European lakes as required by the Water Framework Directive. The strongest and most sensitive of the 11 metrics responding to eutrophication pressure were phytoplankton chlorophyll a, a taxonomic composition trophic index and a functional traits index, the macrophyte intercalibration taxonomic composition metric and a Nordic lake fish index. Intermediate response was found for a cyanobacterial bloom intensity index (Cyano), the Ellenberg macrophyte index and a multimetric index for benthic invertebrates. The latter also responded to hydromorphological pressure. The metrics provide information on primary and secondary impacts of eutrophication in the pelagic and the littoral zone of lakes. Several of these metrics were used as common metrics in the intercalibration of national assessment systems or have been incorporated directly into the national systems. New biological metrics have been developed to assess hydromorphological pressures, based on aquatic macrophyte responses to water level fluctuations, and on macroinvertebrate responses to morphological modifications of lake shorelines. These metrics thus enable the quantification of biological impacts of hydromorphological pressures in lakes.

The project VALIMAR (Validation of biomarkers for the assessment of small stream pollution): objectives, experimental design, summary of results, and recommendations for the application of biomarkers in risk assessment

Between 1995 and 1999, active and passivebiomonitoring experiments in two small streams,and tests with pollutant mixtures in thelaboratory were performed with brown trout(Salmo trutta f. fario) and stone loach(Barbatula barbatula) in order toevaluate the suitability of biomarkersrepresenting different levels of biologicalorganization for the assessment of pollution insmall streams. The following groups ofbiomarker responses were measured in bothspecies: (1) induction of stress proteins(hsp70) in fish liver, (2) alterations in theactivities of 13 metabolic enzymes and ofacetylcholine esterase in liver or brain in vivo as well as in cultured fish cells, (3)changes in phase I and II biotransformationenzyme activities in liver, (4) responses ofblood parameters, (5) histopathologicalalterations in liver, kidney, gills, andspleen, and (6) ultrastructural effects in theliver, gills, and kidney of individuals, aswell as in fish cell cultures. To supplementthese biomarker studies, (7) behavioral changesof fish and (8) impacts on embryo developmentwere also investigated. In parallel, the teststreams were characterized morphometrically,limnologically and analytically for five years.Furthermore, during the second-half of thisproject, ecological studies characterizingbrown trout and stone loach populationdemography and the fish, macro- andmeiozoobenthos communities in the two teststreams were also included. The present papersummarizes the aims and scopes and the generalresults of this project and provides a detaileddescription of the experimental designs whichare the basis of all related studies reportedin this issue. Recommendations are alsoprovided for the application of biomarkers inrisk assessment of small stream pollution.

Using indicators of fish health at multiple levels of biological organization to assess effects of stream pollution in southwest Germany

The health of fish populations and assemblagesin two degraded streams in south-westernGermany were investigated in order to validatethe use of biomarkers for the assessment ofsmall streams as part of the Valimar project.In the more severely polluted stream,recruitment was impaired and populationabundances were low. Extinction ofsite-specific species and appearance of nonsite-specific species has resulted in a shiftin the species composition from thatcharacteristic of unpolluted reference streams.In the less severely degraded stream, abundantrecruitment and relatively high densities ofadults indicated healthy, self sustaining fishpopulations. Missing species, however,indicated some effects of human influenceswithin the reference stream. The reproductivestatus of adult stone loach, Barbatulabarbatula, was not affected in any stream asreflected by normal production of eggs andreproductive behavior. Indices of energystorage differed between the investigated sitesbut could not be related to pollution. Theevaluation of biological integrity based onfish assemblages revealed that both sites inthe more severely impacted stream were in poorcondition. The two reference sites wereclassified in moderate and good condition,respectively. By excluding effects of migrationbarriers on the fish assemblage there was astronger correlation between chemical waterquality and biomarker responses. The resultsindicate the importance of assessing theeffects of pollution within the content oflongitudinal gradients in streams and theusefulness of measuring health effects overseveral levels of biological organization.

Reference conditions of German stream types analysed and revised with macroinvertebrate fauna

Abstract This study investigates reference conditions of German stream types using the top-down stream typology developed by Pottgiesser & Sommerhauser (2004) and 264 macrozoobenthos samples selected as representing reference status. With the aid of discriminant and correlation analyses, the use of typological parameters is investigated as regards their relevancy and the study aims to show whether the metrics used in the newly developed type-specific indices ( Bohmer et al. 2004b) reflect the reference conditions. The data cover 15 of the 24 German stream types. The use of stream size, of ecoregions as an indirect parameter for geographical altitude, and of the bottom substrate for the lowland stream types as typological factors can be confirmed, as can six stream types as separate and independent. As bottom substrate is an essential factor for the lowland stream types, their independency is at least probable. For the stream types of the lower mountain regions, a separation of siliceous and calcareous types seems not to be crucial for the bioassessment on metric level, while a new approach for and a possible splitting of the small streams in floodplains is recommended.

Establishing Causality between Pollution and Effects at Different Levels of Biological Organization: The VALIMAR Project

The study summarizes the objectives of the VALIMAR project and gives selected examples of biomarker responses that allow causal relationships to be established between exposure and biological effects at different levels of biological organization. In this project, active and passive biomonitoring experiments with brown trout (Salmo trutta f. fario) and stone loach (Barbatula barbatula) were performed in two small streams in southern Germany between 1995 and 1999 in parallel with investigations on contaminant mixtures in the laboratory in order to evaluate the suitability of biomarkers representing different levels of biological organization for the assessment of pollution in small streams. In addition to biomarker studies, the morphology of the test streams was characterized and limnological and chemical parameters were monitored. Early life stage tests and ecological studies of brown trout and stone loach population demography, of the fish assemblages, and the macro- and meiozoobenthos communities in the two test streams were included in the project. Several causality criteria were addressed by means of combined (1) laboratory and field studies, (2) chemical, biological, and statistical investigations, and (3) in vivo and in vitro studies that allowed establishment of cause-effect relationships at different biological levels. The comparison of results obtained at these levels allowed identification of mechanisms responsible for the respective effects (coherence of association, biological plausibility). Finally, individual responses (biomarkers, bioindicators) could be extrapolated to higher biological levels (population, community) thus addressing the criteria of ‘time order’ and ‘coherence of association’.

Macrozoobenthos communities and biocoenotic assessment of ecological status in relation to degree of human impact in small streams in southwest Germany

One of the major objectives of the VALIMAR project is to determine the ecological significance of various fish biomarker studies as indicators of chronic pollution in small streams in southwest Germany. Results of these fish biomarker investigations were compared to information from complementary studies on the meiobenthos, macrobenthos, and fish community studies to assess the ecological significance of these biomarker investigations. The main objective of this study was to provide biological assessments of the biomarker sites on the basis of the macrozoobenthos communities. Since no validated framework for the assessment of the biological integrity existed in Germany, two multimetric approaches were adapted to the whole stream system by investigating benthos and fish communities of 46 sites of varying degrees of human disturbance. Assessment of the communities was conducted in accordance with the European Community Water Framework Directive. Species distribution of benthos depended upon stream type and pollution status of streams. Biological attributes and bioindices of benthos communities, however, did not correlate with typological parameters like stream size or dominant substrate but correlated better with pollution parameters like conductivity or chloride concentration. Using a set of 18 measures, such as portion of sessile individuals, Rheoindex, oxygen availability index, and portion of pool dwellers, the benthos communities were characterized and evaluated. The composition of the fish communities was mainly determined by stream type, pollution and migration barriers. The influence of chemical parameters could be assessed by developing a“fish chemistry index”, which calculatesthe similarity of the present fish community with the potential natural community, but excludes those species strongly effected by deficits in stream channel morphology. Both fish chemistry index and benthic indices strongly correlated with pollution index parameters, clearly distinguishing between the more polluted Körsch sites and the less pollutedKrähenbach and Aich sites. Most of the single bioindices as well as overall assessment by multimetric indices indicated a gradient of decreasing quality from the reference stream Krähenbach to theslightly polluted Aich and Körsch upstream site (KE, upstream of all sewage treatment plants) and finally to the most polluted Körsch site directlybelow the most upstream sewage treatment plant (KD). According to the Water Framework Directive, the classification of ecological status of the benthos communities ranges from “high” (best of 5 classes) forthe reference stream to “bad” (5th class) for KD. Assessment of the fish community tends to score somewhat worse than the benthos due to deficits in morphological quality of the stream reaches.The benthos assessment and the newlydeveloped “fish chemistry index” correlated well with chemical water quality and hence with biomarkers, whereas ecological status of fish and overall ecological status was also influenced by river morphology. In conclusion all tested assessment methods on biocoenotic level are reliable indicators for the degree of human disturbance on small streams, whereas biomarkers are more suited for risk assessment and the investigation ofcause-effect-relationships.

Fish communities and migrations in the vicinity of fishways in a regulated river (Enz, Baden-Württemberg, Germany)

Abstract We evaluated the effects of fishway design and stream habitat on fish distribution and migrations within a 50 km section of the Enz River (108 km long, 16.7 m 3 · s −1 mean annual discharge), a second order tributary of the Rhine River. On 12 different occasions between August 1994 and September 1995, we collected fish electrically upstream, downstream, and inside three different types of fish-passes: a concrete channel (site I), an artificial stream (site II), and a step and pool fishway (site III). During electrofishing, species identity and fish lengths were recorded separately for specific habitats or sections within the fishways, and traps were installed for 3–5 week long periods at the upstream outlets of the fishways. More than 3550 fish >5 cm and approximately 5800 young-of-year individuals of 28 species were captured. 772 fish marked by subcutaneous injection of alcian blue dye were released downstream of two fishways. Almost 1150 fish, including 5 marked individuals, were captured in the traps, providing direct evidence for migration through the fishway. The total number of species recorded decreased downstream from 21 at site I to 18 at site II, and 17 at site III. This shift in numbers and also in species composition between sites could be partially related to differences in the available habitat. There were pronounced changes in the abundance of most of the dominant species downstream and upstream of the fishway at site III, and, to a lesser degree at sites I and II, indicating species (and size) specific differences in the effectiveness of the three designs for fish passage. Furthermore, marked differences in relative fish abundance between downstream locations and inside the fishway itself, and in the relative numerical composition of the trap catch at sites I and II, clearly demonstrate that some species ( Cottus gobio, Barbatula barbatula, Salmo trutta, Leuciscus cephalus ) use these fishways as a habitat, whereas others ( Phoxinus phoxinus, Gobio gobio ) simply migrate through. Only inside the artificial stream did we find early life stages of seven species, suggesting that passage of the other fishways is restricted to older fish. Our results demonstrate that fishway design is crucial in providing continuous fish passage for all species and life-stages, and that a nature-like fishway is the most functional solution.

Upstream movements of benthic macroinvertebrates in two different types of fishways in southwestern Germany

Upstream movements and migrations of benthic macroinvertebrates are an important component of running water dynamics. Many lotic organisms perform upstream movements at some stage in their life-cycle. We investigated whether a boulder ramp and a concrete bypass fishway on two streams in Baden-Württemberg, Germany, are successfully used by benthic invertebrates to reach upstream areas. We compared macroinvertebrate distribution at sites upstream and downstream of the fishways, rated the fishways according to their constructional features and conducted migration experiments with marked Gammaridae in the passages. The number of taxa and densities of macroinvertebrates did not significantly differ between upstream and downstream sites in both rivers. Constructional features and the results of the mark-recapture experiments indicated that the boulder ramp allows upstream migrations in principal, whereas the bypass is more difficult for macroinvertebrates to ascend. Both fishways immediately exit into an impoundment, which is a potential barrier for migrating invertebrates. High average current velocities, lack of lenitic banks and sheltered interstices, as well as problems caused by the operation of a power plant are factors explaining why the Enz River bypass is only marginally functional for invertebrates. The investigation concludes that in constructing fishways suitable for upstream movements of lotic invertebrates, more attention should be paid to their specific requirements.