One decade of benthic macroinvertebrate biomonitoring in the River Meuse

The benthic macroinvertebrate community of the River Meuse was studied at four locations in Belgium and The Netherlands from 1983–1993. Macroinvertebrates were collected from artificial substrates, placed near the river bottom from June–August. The results were analyzed using autecological information. At an upstream sampling site in the Belgian Ardennes (Hastière) the most diverse fauna was found. One quarter of the taxa found at this site are known to be confined to running waters and none of the dominant or subdominant taxa could be characterized as a specialized riverine taxon. These findings indicate an impoverished riverine fauna. This was especially the case in years with low discharge, indicating a delicately balanced ecosystem, easily susceptible to disturbances in the environment. Further downstream, in the heavily industrialized region of Liège (Hermalle) and just across the Belgian-Dutch border (Borgharen) the macroinvertebrate fauna consisted of taxa tolerating severe organic pollution. The ecosystem at these sites is on the brink of collapse. Recent results indicate an improvement of this situation at Borgharen. The macroinvertebrate fauna in the lowland reach (Keizersveer) indicates ecological recovery. It is concluded that abatement of the severe pollution must be the first step for an ecological rehabilitation of the degraded ecosystem and for the safe drinking water supply for millions of people in Belgium and The Netherlands.This article is dedicated to my friend and colleague Nicole Frantzen, who died in 1992 at the age of 27.     

The filtration rate of the zebra mussel Dreissena polymorpha used for water quality assessment in Dutch rivers

The effects of contaminated river water on the filtration rate of zebra mussels from a clean reference site were studied. After a 48-h exposure period to filtered water from the rivers Rhine, Meuse and Amstel (The Netherlands), the filtration rate was measured. It was demonstrated that water from contaminated locations inhibited the filtration rate. Inhibition was higher during low water levels in the rivers Rhine and Meuse than during high water levels, suggesting that contaminants are diluted during high water levels. It is concluded that the shortterm filtration assay with D. polymorpha can be used for assessing water quality.     

Are zebra mussels restricted by toxicant levels in the River Meuse? a review

This paper questions if chemical barriers prevent the occurrence of benthic invertebrates in the river Meuse. To this purpose an ecotoxicological analysis is presented, using published observations on the zebra musselDreissena polymorpha, a tolerant species that maintains populations in the river. Zebra mussels collected or exposed at the Belgian-Dutch border contained high levels of several groups of toxicants, and mixture toxicity is likely to occur. A recently developed bio-assay, using the filtration rate of the zebra mussel, demonstrated strong inhibitory effects of water from the river Meuse. To determine which (combination of) toxicants cause such effects, laboratory experiments with toxicant mixtures were carried out. It was demonstrated that in a mixture of five metals (Cu, Zn, Ni, Cd, Pb) the metals contributed to the toxicity of the mixture below the No Observed Effect Concentrations (NOEC) for these metals when tested individually. The average concentration of Cu, Zn and possibly Pb in Meuse water exceed the NOEC values for filtration rate. Thus, it seems likely that joint effects of different (groups of) toxicants in the river Meuse cause the overall toxicity of the water for the zebra mussel, explaining the marginal populations at the test site, while other river species are absent there. It is suggested that toxicants in the river Meuse restrict the recolonisation of the river by invertebrate species more sensitive than the zebra mussel. This will be studied using invertebrates of different sensitivities (molluscs, arthropods), enabling the assessment of toxicity at different stages of water quality improvement of the river Meuse.     

Effect of Silt, Water and Periphyton Quality on Survival and Growth of the Mayfly Heptagenia Sulphurea

The herbivorous mayfly Heptagenia sulphurea is characteristic of rivers with stony bottoms. Records from the 20th century showed that this species had disappeared from the Common Meuse in the Netherlands, probably due to river regulation or changes in water quality. A field survey in 2003 showed that H. sulphurea was present in the Geul tributary, approximately 300 m upstream of its confluence with the Common Meuse. H. sulphurea has not recolonized the Common Meuse despite improvements in water quality over the last decades. Concentration of suspended sediments in the River Meuse, however, is still high, much higher than in the beginning of the 20th century. The presence of a silt layer may limit the return of H. sulphurea in this river by reducing availability and quality of its food. The prime objective of this study was to investigate the impact of silt on survival and growth of H. sulphurea in a laboratory experiment. Furthermore, the impact of water and periphyton quality from the Common Meuse on survival and growth of this mayfly was also investigated. Results showed that neither water quality nor cultured periphyton from the Common Meuse reduced survival and growth of H. sulphurea. The presence of a silt layer resulted in a significantly lower growth rate of the mayfly larvae. It is concluded that the silt layer reduces the accessibility of the food. Covering of food is possibly one of the main factors limiting the recolonization of H. sulphurea and probably other benthic grazers in the Common Meuse.     

Monitoring of algae in Dutch rivers: does it meet its goals?

Observations on phytoplankton in the lower reaches of the rivers Rhine and Meuse were carried out in the framework of the national monitoring programme of the main water systems in The Netherlands. Seasonal changes in density and species composition were analysed to detect the major variables and to discuss whether this monitoring meets its goals. Phytoplankton reached peak densities of 140 and 65 μg L^-1 Chl a in the Rhine and Meuse, respectively. Overall density was correlated with seasonal variation in water discharge rather than with nutrient concentrations, that are high in both rivers. The position of sampling sites in relation to the downstream development of the plankton was very important, especially in the regulated Meuse. Despite hydrographic and chemical differences between the two rivers, many species, predominantly diatoms and green algae, were shared. The occurrence of the diatom Skeletonema subsalsum in the Rhine and the green algae Neodesmus danubialis, Micractinium pusillum and Pseudotetrastrum punctatum in the Meuse (1992, but not 1996) was interpreted as a feature related, respectively, to the high salinity of the Rhine and specific riverine conditions of the Meuse. In general the potamoplankton was characterised as an opportunistic assemblage exploiting the high nutrient contents and disturbed hydrography of both rivers. Nevertheless, the phytoplankton contributed to the characterisation of the present river communities, ones that differ rather strongly in historic records. Although year to year variation in phytoplankton density is mainly related to variation in water discharge, phytoplankton biomass did increase as a result of eutrophication over a period of decades. The widespread nature of many of today's potamoplankton species in the two rivers render these organisms less useful for indicating short-term changes in water quality. However the importance of phytoplankton in trophic relationships merits its inclusion in the monitoring of riverine ecosystems. This revised version was published online in June 2006 with corrections to the Cover Date.     

The rivers Rhine and Meuse in The Netherlands: present state and signs of ecological recovery

The ecosystems of the rivers Rhine and Meuse have suffered drastic environmental changes, for example because of the regulation of the stream bed and the construction of weirs and dams. Furthermore, discharges of industrial and municipal waste water have caused the water quality of these rivers to deteriorate; this problem became acute in the sixties and seventies. Recently some chemical parameters of water quality have improved in the Rhine, and as a consequence some aquatic communities are showing signs of recovery after decades of severe degradation. This paper describes the present state of the aquatic communities in the Dutch part of the rivers Rhine and Meuse, using published observations on plankton, macrophytes, invertebrates, and fish. The sparse information on the food chain in these rivers is summarized. The main channels of the Rhine and Meuse are characterized by a dense plankton that develops rapidly in the nutrient-rich river waters. The stream beds, now dominated by wave-exposed sand and gravel, have a sparse fauna and flora. The river banks, mostly consolidated by blocks of stone, offer a substratum for numerous benthic organisms, particularly now that the water quality has improved. The floodplain waters and old river channels harbour a flora and fauna rich in species. The degree of water exchange with the river is crucial for the ecological development of the river and its backwaters. Today the freshwater tidal reaches of the rivers occupy a very restricted area, and only remnants of the previously abundant vegetation of rushes are found. Losses in the numbers of animal and plant species, notably those specific to rivers, are evident, but over the last 15 years several species have returned. Allochthonous species (exotics), including crustaceans and molluscs, have also settled in the Rhine and Meuse. Fish species characteristic of these rivers, such as river lamprey, sea trout, barbel, and flounder, have recently been observed in appreciable numbers. The Rhine Action Programme provides a framework for the large-scale rehabilitation of the Rhine. Experiments on re-stocking the Rhine with Atlantic salmon and on the ecological rehabilitation of floodplains are being carried out on the assumption that there will be a further reduction of the pollution load. A similar programme is required for the Meuse.     

The relationship between Callitriche L. clones and environmental variables using genotyping

The genetic variation and clonality in Callitriche L. populations from 16 headwater rivers in Belgium were determined by random amplified polymorphic DNA (RAPD). It was shown that samples of morphological C. obtusangula can be separated into at least two genetically distinct groups. Both gene pools occurred within each considered river basin, i.e. Nete and Meuse. A multivariate analysis showed that the variability among different clones, as characterized by their genotypes, can be explained through ecological indicator values such as diatom saprobity and environmental variables related to water quality type. This study showed that multilocus genotypes or gene pools might have a non-random distribution in the rivers and in their particular environments.     

Occurrence of the Rhodophycean algaThorea ramosissima Bory in the River Meuse

Recently the red algaThorea ramosissima Bory has been found in three localities in the Dutch stretch of the river Meuse. The species was already known from a number of localities along the river Meuse and its tributary the river Sambre in Belgium. Consequently, the known northern border of the species has shifted considerably. In spite of this there are no clear indications that the species has extended its range. On the contrary it seems more likely that it has been overlooked in the past.Th. ramosissima occurs only on solid substrates in the lower part of theCladophora glomerata (L.) Kütz. belt or deeper, and is characteristic of well-aerated running water.     

The contribution of neighbouring countries to pesticide levels in Dutch surface waters

Compared with other European countries, Dutch consumption of pesticides is high, particularly in agriculture, with many of the compounds found in surface waters in high concentrations and various standards being exceeded. Surface water quality is routinely monitored and the data obtained are published in the Dutch Pesticides Atlas. One important mechanism for reducing pesticide levels in surface waters is authorisation policy, which proceeds on the assumption that the pollution concerned has taken place in the Netherlands. The country straddles the delta of several major European rivers, however, and as river basins do not respect national borders some of the water quality problems will derive from neighbouring countries. Against this background the general question addressed in this article is the following: To what extent do countries neighbouring on the Netherlands contribute to pesticide pollution of Dutch surface waters? To answer this question, data from the Pesticides Atlas for the period 2005-2009 were used. Border zones with Belgium and Germany were defined and the data for these zones compared with Dutch data. In the analyses, due allowance was also made for authorised and non-authorised compounds and for differences between flowing and stagnant waters. Monitoring efforts in the border zones and in the Netherlands were also characterised, showing that efforts in the former are similar to those in the rest of the country. In the border zone with Belgium the relative number of non-authorised pesticides exceeding the standards is clearly higher than in the rest of the Netherlands. These exceedances are observed mainly in flowing waters. In contrast, there is no difference in the relative number of standard-exceeding measurements between the border zones and the rest of the Netherlands. In the boundary zones the array of standard-exceeding compounds clearly deviates from that in the rest of the Netherlands, with compounds authorised in the neighbouring countries but not in the Netherlands, such as flufenacet, featuring prominently. The share of the neighbouring countries in the total number of exceedances in the Netherlands is roughly proportional to the relative area of the border zones. Although there is a certain influx of pesticides from across national borders, the magnitude of the problem appears to be limited.     

Phytoplankton dynamics in the River Meuse as affected by pollution

The temporal and spatial dynamics of phytoplankton in the River Meuse and a number of physical and chemical parameters were analyzed to gain insight into the pollution level in the river affecting the phytoplankton community. During 1993, samples were taken every two months at eight stations along the River Meuse for physical, chemical and biological characterization of the water. In February, water samples were also taken for laboratory incubations of the natural plankton community. The algae showed a rapid successive development with highest densities (up to 77 mg chlorophylla l^–1) in the middle reach of the river in spring and summer. During winter algal biomass remained very low. A substantial input of nutrients (nitrogen, phosphorus) was observed in the middle reach of the river. Concurrently, an increase in temperature and a reduction in pH was observed. Furthermore, the toxicity of polar organic compounds in the Microtox test showed a strong increase up to the city of Liège and the Belgian/Dutch border; the water quality improved further downstream. The relatively high toxicity at the location Liège was reflected in relatively low growth rates of phytoplankton in the laboratory experiments using water from these locations.     

Genetic characterization of Western European noble crayfish populations (<Emphasis Type="Italic">Astacus astacus</Emphasis>) for advanced conservation management strategies

One central goal of conservation biology is to conserve the genetic diversity of species in order to protect their adaptive potential. The main objective of this study was to identify management units (MUs) for the threatened noble crayfish (Astacus astacus) in Western Europe by utilizing sequence and microsatellite analysis to determine populations in need of focused conservation programs. With the analysis of noble crayfish from 31 sampling sites from Belgium, France, The Netherlands and Germany, and further comparison of this data with a European-wide dataset, we propose four distinct MUs: the French Meuse (MU 1), the French Rhine (MU 2), the Belgian Scheldt and Meuse (MU 3) as well as populations from the French Seine (MU 4). This knowledge enables advanced A. astacus conservation management practises in these catchments by distinguishing between outbreeding and inbreeding populations and by preserving the maximum genetic diversity. When required, a high genetic diversity can be conserved by strengthen existing populations via stocking with populations that either bear the most common haplotype or population-specific private haplotypes in order to maintain recent and regional adaptions. Above all, stocking with populations that exhibit haplotypes from outside Western Europe should be avoided in these catchments. This study supports the preservation of the genetic diversity of noble crayfish in Western Europe and provides thus a proposition for advanced conservation management.     

Zooplankton distribution in flowing waters and its implications for sampling: case studies in the River Meuse (Belgium) and the River Moselle (France, Luxembourg)

Zooplankton spatial distribution was studied on four occasions by transect sampling on the rivers Moselle and Meuse in July 1996. Sampling sites were selected for their variety in morphology. A pseudoreplicate-based sampling scheme was adopted that allowed small-scale longitudinal variations in density to be tested along with transversal position and depth. In the Moselle, zooplankton were unevenly distributed transversally, an observation tentatively linked with the complexity of the river channel and the influence of tributaries. In the Meuse, spatial heterogeneity was stronger, and depth also played a key role. Its effect was different for rotifers and microcrustaceans. The occurrence of zooplankton patches, similar to those commonly reported from lakes, was noted. The factors leading to the establishment of such distribution patterns, and their relevance to routine sampling, are briefly discussed; a short list of recommendations for sampling in large rivers is proposed.      

The Mayfly,Ephoron Virgo (Olivier), back in the Dutch parts of the rivers Rhine and Meuse

Due to severe water pollution, the mayflyEphoron virgo (Olivier) disappeared from the Dutch parts of the rivers Rhine and Meuse in the first half of this century. In August 1991, however, larvae were found in the littoral zone of the Rhine near the Dutch-German border. Later, other stages were found along the Rhine branches and a small section of the Meuse. The occurrence in The Netherlands is the result of further expansion from the upstream regions of the Rhine.     

On the occurrence of the Asiatic cyprinid Pseudorasbora parva in the Netherlands

A large scale inventory along the Meuse River (the Netherlands), showed that floodplain lakes function as spawning, nursery and adult habitats, while the main river channel merely serves as a dispersal corridor for adult Pseudorasbora parva , one of the most successful invasive fish species that have colonized Europe.     

Spatial variation in ciliate communities with respect to water quality in the Delhi NCR stretch of River Yamuna,India

The River Yamuna emerges from Saptarishi Kund, Yamunotri and merge with River Ganges at Allahabad, India. Anthropogenic stress has affected the water quality of the river Yamuna drastically in the stretch traversing Delhi and its satellite towns (National Capital Region, NCR). In the present study, effect of water quality on the microbial life in the River Yamuna was analyzed using ciliate communities (Protista, Ciliophora) as bio-indicators. Water samples were collected from six sampling sites chosen according to the levels of pollution along the river and water quality was analysed using standard physicochemical factors. As the river traverses Delhi NCR, water quality deteriorates considerably as indicated by the Water Quality Index at the selected sampling sites. Seventy-four ciliate species representing nine classes were recorded. Based on the Shannon diversity index, maximum species diversity was found at the point where the river enters Delhi. The saprobity index showed the river water was beta-mesosaprobic when the river enters Delhi and alpha-mesosaprobic at downstream sites after the first major drain outfall. Significant relationship between the spatial variation in ciliate communities and abiotic parameters indicate that ciliates can be used as effective bioindicators of pollution in the River Yamuna.     

Seasonal variations of pollution biomarkers in two populations of Corbicula fluminea (Müller)

Seasonal variations of pollution biomarkers have been studied in two populations of Corbicula fluminea (Müller) for 2 years. Clams were collected from the Sanguinet lake and the Dronne river (Southwest France), sites characterised by water of excellent and passable quality, respectively. Biological parameters studied were enzymatic activity (catalase, propionylcholinesterase, glutathione S-transferase, NADPH-cytochrome c reductase and NADH-cytochrome c reductase activities) and indicators of physiological (protein, carbohydrate, lipid and ash contents, fresh and dry tissue weights, condition factor) and reproductive (amount of oocytes present in gonads and clams incubating larvae in gills) status. Environmental parameters (e.g. water temperature, chlorophyll a concentration) were also monitored. Effects of site, sampling date and season (from spring to winter) were studied, as well as relationships between abiotic and biotic factors. Finally, an index of variability was calculated for each biomarker. Catalase, propionylcholinesterase, NADH-cytochrome c reductase and lipids experienced the most pronounced seasonal fluctuations, whereas glutathione S-transferase, NADPH-cytochrome c reductase and proteins suffered less pronounced ones. For some parameters, results differed depending on the site. Most seasonal changes were related to the reproductive cycle and/or water temperature. Implications of such variations in the use of pollution biomarkers in environmental surveys are discussed.     

Biodiversity in the Lower Rhine and Meuse river-floodplains: Its significance for ecological river management

The diversity of aquatic biota in two large river systems of The Netherlands,viz. the Lower Rhine and Meuse, is discussed in order to: (1) reveal historical changes in biodiversity; (2) examine the role of river-floodplain connectivity; (3) set guide lines for ecological river management. The taxonomical diversity, or species richness, is used to describe the former and recent state of aquatic biota in these river systems. The ecological diversity, obtained by incorporating the concept of ecological groups into the concept of biodiversity, appears very useful in delineating guide-lines for ecological river management. The present species richness in the main channels still appears to be relatively low, despite major water quality improvements. Although present biodiversity is much improved compared with a few decades ago, it is evident that the present species are mainly eurytopic, including many exotics. The inhibition of a further biodiversity recovery results from river regulation and normalization, which have caused the deterioration and functional isolation of main channel and floodplain biotopes. The importance of connectivity for the diversity of aquatic biota is found to be different for various taxa. Moreover, a transversal zonation by the biota in the floodplain lakes is found, emphazising the importance of differences in the degree of connectivity for a diverse aquatic flora and fauna. It is concluded that floodplain lakes contribute significantly to the total biodiversity of the entire riverine ecosystem. The redevelopment of active secondary channels is required to restore the most typical riverine habitats and biota.     

Comparative monitoring of diatoms, macroinvertebrates and macrophytes in the Woluwe River (Brussels, Belgium)

The river Woluwe in Brussels and Flanders (Belgium) is a small tributary of 15 km length that drains an area of 9400 ha in the Schelde river basin. The headwaters of the Woluwe are highly fragmented by diverse pond systems and are vaulted in the Brussels agglomeration. Hyporheic zones locally influence the water quality. The downstream stretch of the river receives sewage waters from households and industry. As the river Woluwe within a short distance represents a typical gradient from groundwater-fed sources in the forest towards severely polluted water, a comparative monitoring using diatoms, macroinvertebrates and macrophytes was done. The saprobic index based on diatoms, the Belgian Biotic Index (BBI) for macroinvertebrates and a macrophyte index based on the N-values of Ellenberg were used in this comparison and for estimating the correlation with the bimonthly measured chemical variables in 16 sampling stations. The diatom saprobic index and the macrophyte index were strongly correlated. Both groups showed strong correlations with phosphate, ammonium and chemical oxygen demand. The Belgian Biotic Index showed lower correlations with the nutrient variables, but was slightly better correlated to chemical oxygen demand, chloride and dissolved oxygen. None of the indices showed a correlation with nitrate. Local substrate or light conditions could interfere with the indicator system, especially for the macrophytes and occasionally for the macroinvertebrates. It was concluded that at least in this particular river system, the indices based on the primary producers were more indicative for the trophic status, whereas the BBI showed a broader relationship to the general degree of pollution. Therefore, these three indices are considered as complementary for monitoring the biological quality and the ecological status of a river system.     

Comparison of biotic index used in monitoring of 2 lotic systems in north-western Argentina

Two lotic bodies located in a subtropical semi-arid region in north-western Argentina were studied: the Arias-Arenales and the Rosario rivers. Both rivers are located in Salta Province, and belong to the high basin of river Juramento, connected to the river Río de la Plata and the Atlantic Ocean. The study was conducted between March 1997 and March 1998. The region is known by its sustained economic development and one of the highest population growth rates in the country (4% per year). The objective of this work was the assessment of organic pollution spatial gradients in both rivers, as a function of the hydrological regime (a long period of drought from May to October and floodings the rest of the year). Three groups of biotic indices were applied to characterize the level of organic pollution and were based on planktonic microalgae to evaluate water quality. The relative performance of these indices was then compared for use to biomonitoring programs. The diversity indices: Shannon-Weaver and Whilm-Dorris were not highly sensible to detect moderate pollution. The saprobity indices (Pantle and Buck and Diatom Assemblage Index of Watanabe et al.), were useful to detect intermediate levels of organic load, but their sensitivity dropped at high pollution levels. The second index precisely discriminated the most deteriorated part of river Rosario, with values between 0.3-0.7 (extreme poli-saprobity). Raw sewage discharges along the most polluted sector of river Arias-Arenales were assigned a value between 10 and 11 in both periods of the hydrological regime. Both saprobity indices consider the same indicator pollution value of species. The first one is based on the relative abundance of the species while the second one is calculated with the species relative frequency. The second index is better than the first one in considering non-dominant species that were constant in each particular environmental condition. The principal component analysis allowed a representation of time and space pollution patterns and showed the specific microalgae assemblage for all the sampling stations and for both periods in the hydrological cycle. Only the latter proved to be fully useful and correct for the biological characterization of water quality system.     

Relationships between mesohabitats, ichthyological communities and IBI metrics adapted to a European river basin (The Meuse, Belgium)

We investigated the influence of mesohabitats on fish communities and on attributes of a multimetric index of fish integrity in the River Meuse basin. Three consecutive 150 m sectors in a Meuse tributary (Ourthe, Belgium), each divided in two or three sub-sections presenting various percentages of mesohabitats (riffles, runs and pools), were sampled by electrofishing. In each sub-section, relative and absolute biomasses of each fish species were estimated. The presence of limnophilic cyprinids was inversely correlated (r ² = 0.70 and 0.56 for absolute and relative biomass, respectively) with the percentage of riffles. Salmonids preferred runs and their absolute biomass was highly dependent (r ² = 0.71) on the proportion of this mesohabitat, whereas biomass of limnophilic cyprinids was highly correlated (r ² = 0.75 and r ² = 0.82 for absolute and relative biomass, respectively) with pools. A positive correlation (r ² = 0.58) was established between relative biomass of predators and the percentage of this mesohabitat. An IBI was calculated for the three sectors on the basis of results from the entire Meuse catchment. Scores of most metrics showed low variation among sectors but values of two metrics (% of individuals as tolerant, % of individuals as ubiquitous spawners) were greatest in sector 2, where pools predominated. Further, the lowest IBI score (51/65, integrity class: fair to good) was recorded in sector 2 where pools dominated, while sector 1 (where runs dominated) obtained the highest score (63/65, integrity class: excellent). Sector 3 which has a balanced proportion of riffles and runs obtained an intermediate score (57/65). Considering the response of IBI to the natural variation of mesohabitat proportions, it appears that an accurate sampling requires the prospection of a variety of mesohabitats (with a majority of runs) for the evaluation of river quality.