Macroinvertebrate Drift Research Articles

Stream macroinvertebrate drift response to pulsed exposure of the synthetic pyrethroid lambda‐cyhalothrin

Outdoor experimental channels were used to study the behavioral changes of stream macroinvertebrates exposed to a pulse of the pyrethroid insecticide lambda-cyhalothrin. The primary end point was the number of macroinvertebrates drifting, but the mobility of macroinvertebrates caught in the drift also was assessed. A specified number of two insect species, Baetis rhodani and Leuctra fusca/digitata, and of the amphipod Gammarus pulex were introduced into small replicated subsections of the experimental channels. Macroinvertebrates were allowed to acclimatize for 26 h prior to a 60-min pulsed exposure to lambda-cyhalothrin. Measurement was initiated 2 h before pesticide application and continued for the following 24 h. Pulse concentrations of lambda-cyhalothrin of 0.001, 0.01, 0.1, and 1.0 microg L(-1) were applied, and each experiment was replicated 8 times. All three species responded to the pesticide pulse with catastrophic drift. The 0.001 microg L(-1) treatment caused a significant increase in the drift of Gammarus, whereas the drift response threshold was 0.01 microg L(-1) for the two insect species. Drift response onset followed the applied pulse concentration, with the highest concentrations resulting in more individuals of all species entering drift at an early stage. The majority of individuals caught in drift samples during low concentrations showed no change in mobility. At the two highest concentrations, however, both Baetis and Leuctra were in the process of being immobilized, with Leuctra the more sensitive of the two. In contrast, only a few of the Gammarus individuals caught showed changes in mobility after the high-concentration treatments. The present study shows that lambda-cyhalothrin is a potential hazard for macroinvertebrate populations in headwater streams. The clear species-specific responses indicate that sublethal doses have the potential to change the macroinvertebrate community structure.

Effects of electroshocking on macroinvertebrate drift in three cold water streams

The effect of electroshocking and walking on the substrate on macroinvertebrate drift was evaluated in three streams located in southwestern Oregon, USA. A randomized block experimental design was used to determine treatment (electroshocking and walking, electroshocking-only, walking-only) and drift distance effects on the number, biomass, and length of macroinvertebrates drifting up to 30 m downstream. In all streams, electroshocking caused significantly (p 0.05) was observed in mean biomass between electroshocking and walking on the substrate among the drift distances. The longest macroinvertebrates were collected from the electroshocking treatment at the shortest drift distance (2.5 m) in all of the streams. The length of macroinvertebrates collected between electroshocking and walking on the substrate were similar at drift distances of 10 m and greater and represented predominately the smaller, poor swimming taxa.

Macroinvertebrate community response to pulse exposure with the insecticide lambda‐cyhalothrin using in‐stream mesocosms

Pesticides are constantly being applied to agricultural catchments, but little is known about their impact on aquatic biota during natural exposure. In the present study, the impact of the pyrethroid lambda-cyhalothrin was studied in an in-stream mesocosm setup. Twice during the summer of 2002, the natural macroinvertebrate community was exposed in situ to a 30-min pulse of lambda-cyhalothrin. Pyrethroid doses were released through a modified drip set with nominal concentrations of 0.10, 1.00, and 10.0 microg L(-1) during the first exposure and 0.05, 0.50, and 5.00 microg L(-1) in the second exposure. Before, during, and after exposure, drifting macroinvertebrates were caught in nets. Quantitative benthic samples were taken both before and on two occasions after exposure. Macroinvertebrate drift increased immediately after the pulse exposure, with total drift being significantly higher at all concentrations. Gammarus pulex, various Ephemeroptera, Leuctra sp., and Simuliidae were some of the taxa showing the most pronounced drift response. Structural change in the community was found only at 5.00 and 10.0 microg L(-1), and recovery occurred within approximately two weeks. The present study may be valuable in assessing extrapolations based on laboratory results as well as in evaluating pyrethroid impact on natural freshwater environments.

Influence of Total Organic Carbon and UV-B Radiation on Zinc Toxicity and Bioaccumulation in Aquatic Communities

The effects of total organic carbon (TOC) and UV-B radiation on Zn toxicity and bioaccumulation in a Rocky Mountain stream community were assessed in a 10-d microcosm experiment. We predicted that TOC would mitigate Zn toxicity and that the combined effects of Zn and UV-B would be greater than Zn alone. However, TOC did not mitigate Zn toxicity in this study. In fact, treatments with TOC plus Zn had significantly lower community respiration as compared with the controls and Zn concentrations associated with the periphyton increased in the presence of TOC. UV-B had no additive effect on periphyton Zn accumulation or community respiration. Heptageniid mayflies (Ephemeroptera) were particularly sensitive to Zn, and reduced abundances were observed in all Zn treatments. UV-B did not additionally impact Heptageniid abundances; however UV-B did have a greater effect on macroinvertebrate drift than Zn alone. Ephemeroptera, Plecoptera, and Trichoptera (groups typically classified as sensitive to disturbance) were found in highest numbers in the drift of UV-B + Zn treatments. Measures of Zn accumulation in the caddisfly Arctopsyche grandis, periphyton biomass, and total macroinvertebrate abundance were not sufficiently sensitive to differentiate effects of TOC, UV-B, and Zn. These results indicate that UV-B and TOC affect Zn bioavailability and toxicity by impacting species abundance, behavior, and ecosystem processes.

Vertical Distrubution in the Water Column of Drifting Stream Macroinvertebrates

ABSTRACT We examined the macroinvertebrate composition and drift density in a Mediterranean lotic system, the Erro River (northwestern Italy). Drift density and composition were sampled for one year at three levels of the water column; temperature and flow velocity were also measured. We found that drift density was generally highest near the bottom. We also noticed that various taxa tended to drift at preferential levels of the water column, with 41.4 % of taxa mainly at the bottom level and 31.0 % mainly at the top. Drift density decreased with increasing water temperature. Both taxa richness and macroinvertebrate abundance in the drift were positively associated with natural riverbed richness and abundance.

Drift benthos relationships in the seasonal colonization dynamics of alpine streams

We examined seasonal patterns in macroinvertebrate benthic abundance and drift in relation to their colonization dynamics in five contrasting streams. The streams, within an alpine glacial flood plain, differed over an annual cycle in flow permanence and surface hydrologic connectivity with the main floodplain channel. Study streams included an upper and lower main channel, a side-channel seasonally connected upstream to the main channel, and an intermittent side-slope tributary and permanent springbrook having no upstream surface connection to the main channel. Flow in the main and side-channels was influenced seasonally by upstream glaciers, whereas the tributary and springbrook had no direct glacial input. Macroinvertebrate assemblages differed markedly among streams. Density, biomass, and taxonomic richness typically were lowest in the upper main channel and highest in the springbrook. Seasonal changes in assemblage composition were more pronounced in the main and side-channels than in the tributary and springbrook. In the upper main channel, larvae colonizing cages filled with natural substrata reflected benthic assemblage structure regardless of season and colonizing taxa exhibited a high propensity to drift. In contrast, larval colonists differed significantly from benthic assemblages in the tributary and springbrook, and colonists were mostly from drift. The lower main and side-channels displayed high seasonality in colonization dynamics, being related to their hydrologic connectivity to other streams that may have provided larval colonists. Benthos to drift abundance ratios suggested that the upper main channel represented a relatively closed system with little interaction among other streams in the flood plain, whereas the springbrook and tributary seasonally subsidized larval colonists to downstream channels.

The effects of riparian forestry on invertebrate drift and brown trout in upland streams of contrasting acidity

Abstract. Variations in macroinvertebrate drift and benthic invertebrate abundance were assessed in 30 upland Welsh streams of varying acidity (pH < 5.7 or pH.> 6.0) and riparian land-use (conifer, moorland or native broadleaf). The consequences for the diet and condition of wild brown trout Salmo trutta were also assessed. As expected from previous studies, there were significant reductions in benthic invertebrate abundance, aquatic drift density (by >60%), aquatic drift biomass (by >35%), total drift density (by >35%) and total drift biomass (by >20%) at acid sites by comparison with circumneutral sites due largely to the scarcity of mayflies. Absolute drift from terrestrial sources was unrelated to stream pH but formed a significantly greater proportion of total drift at acid sites (30-65% of density) than at circumneutral sites (20-40%) as aquatic contributions declined. Most of this apparent land use effect reflected significantly increased terrestrial drift under broadleaves. There was no significant reduction in terrestrial or aquatic drift at conifer forest sites per se after accounting for low pH. Trout diet varied substantially between locations partly reflecting variations in drift: significantly fewer mayflies and stoneflies were eaten at acid sites, and significantly more terrestrial prey were eaten under broadleaves. However, acidity did not reduce trout condition or gut-fullness. Unexpectedly, trout condition was significantly enhanced at conifer sites, irrespective of their pH. Hence, acidity has greater effects on the benthic abundance and drift density of invertebrates in upland streams than does riparian land use. However, trout forage flexibly enough to offset any possible food deficit, for example by switching to chironomids and terrestrial invertebrates. Enhanced terrestrial contributions to invertebrate drift from riparian broadleaf trees may be important in supplementing foraging opportunities for trout where aquatic prey are scarce. These data illustrate the value of native tree species in riparian locations in upland Britain and the energy subsidy they provide might well be disproportionately important for otherwise impoverished acid streams Keywords: brown trout, land-use, acidification, drift, forestry, streams

SMALL‐SCALE EXPERIMENTS SUPPORT CAUSAL RELATIONSHIPS BETWEEN METAL CONTAMINATION AND MACROINVERTEBRATE COMMUNITY RESPONSES

Routine biomonitoring studies that compare abundance of benthic macroinvertebrates upstream and downstream from contaminant discharges generally cannot be used to demonstrate causal relationships between stressors and biological responses. In this study I describe stream microcosm and field experiments designed to support results of a 12‐year monitoring project in the metal‐polluted Arkansas River, Colorado. Microcosm experiments established concentration–response relationships between heavy metals and several structural (abundance, richness) and functional (macroinvertebrate drift, community respiration) endpoints. EC10 values, the metal concentration that reduced abundance or richness by 10%, were generally lowest for mayflies and stoneflies, indicating greater metal sensitivity for these groups. Macroinvertebrate drift and community respiration showed highly significant concentration–response relationships with heavy metals and were generally more sensitive than structural measures. Potential interactions among metals were investigated by comparing community‐level responses to Zn alone, Zn+Cd, and Zn+Cu+Cd. Results showed that macroinvertebrate responses to a mixture of three metals were generally greater than responses to either Zn alone or Zn+Cd. Long‐term monitoring in the Arkansas River (Colorado) before and after remediation of metal inputs provided correlative evidence that elevated heavy metal concentrations altered community composition and reduced abundance of metal‐sensitive organisms. However, these field data were not especially useful for estimating safe concentrations of heavy metals that would be protective of benthic communities. Microcosm and field experiments provided further support for the hypothesis that metals caused alterations in benthic community structure and provided more precise estimates of safe metal concentrations.

Effect of low dissolved oxygen on survival, emergence, and drift of tropical stream macroinvertebrates

The effect of different dissolved oxygen (DO) concentrations on the macroinvertebrate assemblages from 2 Australian tropical streams (1 upland, 1 lowland) was measured using artificial stream mesocosms. Responses to 5-d exposures were tested. Both the upland and lowland assemblages showed a similar response. Most taxa tolerated all but very low DO levels (<10% saturation), although a reduction in emergence of insect taxa at intermediate levels (25–35% and 10–20% saturation) was observed. Mayflies showed the highest sensitivity to low oxygen conditions, and lethal effects were observed at DO levels <20% saturation for several upland and lowland species. For other taxa, including several Chironomidae, mortality was observed when oxygen concentrations were below 8% saturation. A drift response was observed only when oxygen concentrations reached near lethal levels (≤10% saturation). The lack of a drift response at DO concentrations of 25 to 35% and 10 to 20% saturation indicates that, in moderately poor oxygen conditions, macroinvertebrates will remain at a location and, hence, experience sublethal effects such as suppressed emergence. It is clear that these animals can persist in hypoxic conditions in the short term. However, because of sublethal effects, understanding how low DO concentrations affect natural assemblages of aquatic macroinvertebrates may require studies of populations over several generations.

Runoff-related endosulfan contamination and aquatic macroinvertebrate response in rural basins near Buenos Aires, Argentina.

Information in the open literature about the fate and effects of pesticides in small streams from agricultural areas of Argentina is very rare. The objective of the present work was to study the pesticide contamination and potential biological effects in basins that have undergone intense agricultural activity, mainly related to the cultivation of soybeans. Three streams (Maguire, Helves, and Horqueta) with a low-flow discharge (0.1 and 0.2 m3/s) in March close to the city of Arrecifes were studied during the period of maximum insecticide application, between February and April 2001. Various sampling devices were installed to trap suspended particles, runoff, and floodwater plus sediment throughout the study period. The suspended-particle samples were analyzed for the insecticides endosulfan (END), chlorpyrifos, and cypermethrin. Water chemistry and the macroinvertebrate communities were assessed on four occasions and the organismic drift was measured continuously. Following a 184-mm rainfall on March 1, 2001, beta-endosulfan concentrations up to 318 and 43 microg/kg were measured from suspended-particle samples from Horqueta and Helves, respectively. No END contamination was detected in Maguire. Chlorpyrifos and cypermethrin were not detected in any of the streams. A significant decrease in the average macroinvertebrate species density was observed in Horqueta (from 12.8 +/- 0.5 to 9 +/- 0.7 species; ANOVA, p < 0.05) and Helves (from 10.8 +/- 1.7 to 3.3 +/- 1.3 species; p < 0.001) following the same rainfall event at the beginning of March, while the species density in Maguire remained constant at 7.9 +/- 0.3 species. The runoff primarily reduced species abundances of Odonata and Ephemeroptera significantly (p < 0.01) in Horqueta and Helves but not in Maguire. A greater drift of Smicridae (Trichoptera) and Ephemeroptera occurred in Helves and Horqueta during this runoff event, while no changes in the macroinvertebrate drift were detectable in Maguire. This study highlights the potential pesticide effects on macroinvertebrate communities in Argentinian rural streams. It is suggested that a small wetland area formed by Maguire between the agriculturally used catchment and the sampling site contributes to the absence of contamination and effects at this site.

Multiscale spatial variation of stone recolonization by macroinvertebrates in a Costa Rican stream

The process of stone recolonization by macroinvertebrates was studied at different spatial scales in a stream in Costa Rica. A hierarchical design was used with riffles nested into reaches, and individual stones nested into riffles. Macroinvertebrate abundance and taxon richness varied at riffle scale, although patterns of variation seemed to change with time of recolonization, and taxonomic composition varied mostly at reach scale. Patterns of variation of background communities and macroinvertebrate drift at different spatial scales suggest that the contribution of these two sources of colonists to stone recolonization depends on spatial scale. Macroinvertebrate abundance was related to local environmental variables during recolonization, but taxon richness was related to the local environment only in the very first stage of the process. The need for explicitly determining the appropriate spatial scale in the study of substrate recolonization is emphasized.

Effects of wildfire ash on water chemistry and biota in South‐Western U.S.A. streams

SUMMARY1. We monitored streams within the Gila River drainage in south‐western New Mexico, U.S.A., over a 5‐year period, to investigate the influence of ash input on water quality and stream biota following forest wildfires.2. Nutrients [ammonium, nitrate, soluble reactive phosphate (SRP)], potassium and alkalinity were most affected by fires; all were increased in stream water following ash input. Concentrations of each returned to prefire conditions within 4 months. Ammonium and nitrate also increased in stream water as a result of atmospheric fallout (e.g. smoke) from fires outside the catchment.3. Periphyton biomass was not affected significantly by wildfires, although there was a shift in diatom assemblage to smaller more adnate taxa. Cocconeis placentula was frequently the dominant postfire species.4. The influence of wildfires on macroinvertebrates ranged from minimal to dramatic reductions in density depending upon the duration of ash flows and the characteristics of the ash material that entered each system. Macroinvertebrate densities returned to prefire conditions within 1 year.5. An in‐situ ashing experiment was conducted on a first‐order stream in the Gila River drainage to monitor on‐site physiochemical and biotic responses during and after fire ash addition, for comparison with ash delivery from real wildfires on monitored streams. Physical–chemical parameters and algae and macroinvertebrates were monitored in an ashed and upstream reference reach for 13 months. Results generally substantiated findings from monitored streams.6. Concentrations of major ions and nutrients, as well as turbidity, conductivity and pH, increased immediately in stream water below the point of ashing, while dissolved oxygen decreased. Changes in water chemistry were short‐lived (=24 h) except for SRP. The concentration of SRP in stream water was significantly higher in the ashed reach than the control reach for at least 1 month after ash input.7. Periphyton biomass and diatom assemblages were not significantly altered in the ashing study, whereas macroinvertebrate density was measurably lower in the ashed reach for nearly a year. Macroinvertebrate drift was over 10‐fold greater in the ashed reach compared with the reference reach during ashing. Dissimilarity between macroinvertebrate communities in the reference and ashed reaches was significantly greater than variation within reaches for nearly a year.

Macroinvertebrate drift in Amazon streams in relation to riparian forest cover and fish fauna

Macroinvertebrate drift was studied in 12 sites in 9 lowland streams (400m), three mid-altitude streams (2100 m) and three high-altitude streams (3800 m) in Ecuador. The purposes of our study was 1) to examine levels and periodicity of drift in relation to altitude, 2) to examine levels and periodicity of drift in relation to environmental site characteristics and 3) to examine the effect of deforestation and specific fish families on levels and diel periodicity of drift in the lowland streams. At all altitudes, day drift of terrestrial invertebrates was equal to or greater than that of aquatic invertebrates, while aquatic invertebrates always dominated drift at night. Mean day drift density of aquatic invertebrates was the same at the two high altitudes, while it was lower in the lowland streams. In contrast, night drift density was higher in lowland stream compared to the two highland stream groups. In all lowland streams drift of aquatic invertebrates was higher at night than at daytime (night: day drift ratio 2-45, mean: 10), while it was largely aperiodic in both groups of highland streams. In all lowland streams, drift was dominated by insects (mean 99.6 %). No significant correlations were found between drift density, drift % or periodicity and riparian forest cover, benthic macroinvertebrate densities or any other environmental site characteristic in the lowland streams. However, path analyses indicated that riparian forest had a significantly negative indirect effect on night and day drift densities, because an increase in riparian cover was associated with a decline in the abundance of fish and benthos. Species richness, density and biomass of fish were directly correlated with invertebrate drift. These parameters had no effect on total day or night drift densities or drift %, but were positively correlated with the night: day drift ratio. The night: day drift ratios were more closely correlated with the species richness of Loricariidae catfish than to any other fish family. Loricariidae are night active, benthic herbivorous-detritivorous scrapers of biofilm, and their presumed effect on drift periodicity is due to physical disturbance of benthic invertebrates during the night, and not necessarily to a behavioural response from benthic invertebrates. Drift of the dominant invertebrate families (Leptophlebiidae, Baetidae, Tricorythidae, Hydropsychidae and Chironomidae) varied among localities, but night: day drift ratios of all families were positively correlated with species richness of fish, although this pattern was only significant for Leptophlebiidae and Baetidae.

Spatial and Temporal Variation of Macroinvertebrate Drift in Two Neotropical Streams1

ABSTRACTThe detection of spatial variation in macroinvertebrate drift depends on the spatial scale of investigation in streams of the La Selva Biological Station, Costa Rica. Drift samples were taken in a spatially nested design, with two streams, two reaches per stream, two riffles per reach, and four replicate samples per riffle. Drift showed little variation among streams, but varied significantly at the scales of reach and riffle, with variation among samples also high. In addition, sampling took place at two temporal scales: diel and at two different periods that differed in rainfall conditions. Drift diel periodicity was a clear pattern, while only density of individuals varied among sampling periods. This is the first study of macroinvertebrate drift at multiple spatial scales, despite the recognition that multi‐scale studies are essential for a more complete understanding of community patterns and processes.

Effect of Bull Trout and Brook Trout Interactions on Foraging Habitat, Feeding Behavior, and Growth

Abstract Observations of free-ranging sympatric bull trout Salvelinus confluentus and nonnative brook trout S. fontinalis in two eastern Oregon headwater streams provided little evidence of habitat partitioning. Both species held focal feeding points in similar microhabitats and fed primarily from the water column rather than from the surface or benthos. In an instream experiment, 20 enclosures were assigned one of three treatments: two bull trout, four bull trout, or a mix of two bull trout and two brook trout. In the enclosures, macroinvertebrate drift was restricted and trout densities were elevated, creating an environment of reduced food and habitat resources. Under these conditions, there was no indication of a niche shift by bull trout; feeding behavior and habitat use by bull trout did not differ depending on the presence or absence of brook trout. Brook trout in the mixed-species treatment were the most aggressive, maintained dominance in 75% of the enclosures, and exhibited significantly higher ...

Seasonal patterns in macroinvertebrate drift and seston transport in streams of an alpine glacial flood plain

1. We measured drift of macroinvertebrates and organic matter in five different channel types (upper and lower main channel, intermittent side‐channel, side‐slope tributary, and a groundwater channel) draining a glacial flood plain in the Swiss Alps. Samples were collected seasonally over 3 years (May 1997 to November 1999) to encompass major periods of floodplain expansion and contraction.2. Total wetted channel length ranged from ≤ 5 km during maximum floodplain contraction to ≥ 24 km under system expansion. Principal components analysis (PCA) of key physical and chemical measures collected over an annual cycle showed that the main and side channel sites differed spatially and seasonally from the tributary and groundwater sites, reflecting the glacial influence on the former.3. Two‐way ANOVA indicated a significant Site × Date interaction for all measured variables. Transported organic matter, caused by blooms of Hydrurus foetidus, was typically five to 10 times higher in the lower main channel and side‐channel than the other channel types, and was least variable among dates in the groundwater and tributary channels.4. The number of drifting macroinvertebrates was usually highest in the groundwater channel, although highly variable among years. Other channel types had highest drift rates in November and lowest rates in May, reflecting seasonal changes in the life cycles of particular taxa, such as Baetis alpinus and the Simuliidae. The lower main channel exhibited the greatest, and the groundwater the lowest, seasonality in drift compared with the other channels.5. The Chironomidae displayed the highest drift rates in most seasons, especially in summer when other taxa were relatively low in the drift. The number of taxa in the drift also varied among channel types and season, ranging from less than two in early spring to four to six in other seasons.6. The observed differences in drift rate and transported organic matter among channel types and seasons have important implications for ecosystem dynamics, through its effect, for instance, on dispersal among channel types or on organic matter exchange.

Spatial and Temporal Variation of Macroinvertebrate Drift in Two Neotropical Streams1

The detection of spatial variation in macroinvertebrate drift depends on the spatial scale of investigation in streams of the La Selva Biological Station, Costa Rica. Drift samples were taken in a spatially nested design, with two streams, two reaches per stream, two riffles per reach, and four replicate samples per riffle. Drift showed little variation among streams, but varied significantly at the scales of reach and riffle, with variation among samples also high. In addition, sampling took place at two temporal scales: diel and at two different periods that differed in rainfall conditions. Drift diel periodicity was a clear pattern, while only density of individuals varied among sampling periods. This is the first study of macroinvertebrate drift at multiple spatial scales, despite the recognition that multi-scale studies are essential for a more complete understanding of community patterns and processes.

Factors influencing fish productivity in a newly formed watershed in Kenai Fjords National Park, Alaska

Delusion Creek in McCarty Fjord, southcentral Alaska, was studied over three field seasons from 1992 to 1994 to investigate the factors influencing salmonid colonization and productivity of a new stream system formed by glacial ice recession within the last 40 years. Stream discharge was extremely variable during the summer months. Frequent spate events were a major factor in maintaining an unstable channel and in raising turbidity levels, which limit primary production and the abundance and diversity of invertebrates in the main stream channel available to rearing fish. However, in less than 40 years, coho (Oncorhynchus kisutch), pink (O. gorbuscha), and sockeye (O. nerka) salmon have colonized Delusion Creek, and over 1,000 sockeye salmon were observed to spawn along the margin of the upper lake in 1993. Ninety-three percent of juvenile sockeye salmon remained in the lakes for two years prior to smolting. Kettle ponds, formed after ice recession, were also found to be important rearing areas for juvenile coho salmon. In the main stream channel, Dolly Varden (Salvelinus malma) char were the most abundant juvenile rearing fish. Water chemistry of the lakes indicated that nitrogen was likely a limiting nutrient to primary production. Experiments with artificial channels showed that enrichment with nitrogen and phosphorus increased chlorophyll-a levels and macroinvertebrate drift was significantly reduced from enriched channels. We suggest that primary productivity and invertebrate abundance may be enhanced by the colonization of spawning anadromous salmon which may, thus, act as a positive feedback to productivity of this new stream.

Man‐made secondary channels along the River Rhine (The Netherlands); results of post‐project monitoring

AbstractOwing to river regulations in the past and intensive farming, the ecological value of the floodplains of the River Rhine in The Netherlands has decreased dramatically. One way to restore riverine biotopes is to create permanently flowing channels in the floodplain. Along the River Waal, the main branch of the Lower River Rhine, two such secondary channels have been created since 1994. A post‐project monitoring programme of 5 years was set up, which included hydrological, morphological and ecological parameters. This article focuses on the monitoring of aquatic macrophytes, aquatic macroinvertebrates, fish and wading‐birds.The results show that man‐made, excavated secondary channels function as a biotope for riverine species including the more demanding rheophilic species. The demands for shipping and protection against flooding on the River Waal cause constraints on secondary channels. Despite these constraints there is still enough space for hydromorphological processes to create new habitats in secondary channel 1, near Opijnen. The space for hydromorphological processes is less in secondary channel 2, near Beneden‐Leeuwen. The density and the number of (rheophilic) species are for a large part influenced by the water level and frequent inundation caused by the high hydrological connectivity. Man‐made secondary channels seem to provide suitable habitat that is currently lacking for a broad range of rheophilic macroinvertebrate and fish species in the Lower River Rhine in The Netherlands. Owing to the lack of suitable habitats for rheophilic macroinvertebrate and fish species before the creation of the secondary channels, the importance of longitudinal and transversal migration could be illustrated by the drift of macroinvertebrates during floods and the seasonal migration of Age‐0 and Age‐1+ fish species. Copyright © 2001 John Wiley &amp; Sons, Ltd.

Invertebrate drift and physico-chemical variables in the tributaries of the Mutt, a Swiss glacial stream

The study of the invertebrate assemblages in a small glacial catchment of the Swiss Alps (the Mutt) was designed to categorise sites in relation to their water sources and assess the contribution of small headwater tributaries to the biodiversity of such Alpine catchments. Physico-chemical characteristics and macroinvertebrate drift were monitored in seven streams during three contrasting hydrological periods in June. August and September 1997. Physico-chemical characteristics clearly differentiated kryal (glacial) and krenal (groundwater-fed) streams. The glacial waters showed a broader amplitude in environmental variation, depending on altitude, geology and season. Macroinvertebrate drift composition was significantly correlated with the environmental conditions. In kryal streams, where harsh conditions prevailed, diversity and abundance were low, while the krenal streams showed highly diversified and dense macroinvertebrate communities, favoured by physico-chemical constancy. However, the low number of taxa found at the same time in these groundwater-fed tributaries and in the main Mutt stream indicated a low contribution from these small streams to the communities of the main stream. Nevertheless, the habitat heterogeneity generated by different water origins in the tributaries favoured the coexistence of diversified macroinvertebrate communities in a rather small catchment area. Therefore these tributaries played an important part in the biodiversity of the glacial catchment.