Effects of repeated sediment bypassing on stream ecosystems in a Japanese mountainous river

Sediment bypassing connects the upstream and downstream regions of dam impoundments through tunnels and is expected to partly restore natural processes (flood pulse and sediment regime) in dam-altered river ecosystems. However, few reports examined the effects of restoration on stream biota. We examined the effectiveness of repeated sediment bypassing (12 times) over a period of 5 years in a Japanese dammed river using a before-after-reference-impact design. We compared the abiotic parameters (water quality and substrate environment), biotic assemblages (algae, macroinvertebrates, and fish), and similarities between the dam downstream and undammed reference reaches. The reference sites exhibited high temporal variability in abiotic environments and species composition over the 5-year period. Most abiotic and biotic parameters downstream of the dam improved and approached those of the changing reference states. However, these indices returned to pretrial conditions after the last trial. Biotic similarities between the downstream and reference reaches gradually increased throughout successive sediment-bypassing trials for macroinvertebrates and algae; however, these similarities diminished after the last trial. Conversely, the abundance-based composition of fish assemblages in the restored reach consistently diverged from that of the reference conditions throughout the study period. Our results show that the success and failure of restoration by sediment bypassing may be affected by the amount of bedload in the flushing flows and other regional processes such as migratory connectivity. Sediment bypassing can partially re-establish natural processes and is a useful tool for improving sediment-associated environments and biota.     

Distribution of benthic algae and macroinvertebrates along a thermal stream gradient

The distribution and abundance of benthic algae and macroinvertebrates were examined along a natural thermal gradient formed by hot springs in Little Geysers Creek, Sonoma Co., California, USA. Maximum water temperatures ranged from 52 °C at the uppermost station to 23 °C at a station 400 m downstream. Benthic chlorophyll a decreased exponentially from 2.5 g m^–2 at 52 °C to less than 0.1 g m^–2 at 23 °C, a pattern of decline also exhibited by algal phaeophytin. Blue-green algae dominated at higher temperatures but were replaced by filamentous green algae and diatoms at lower temperatures.Macroinvertebrates were absent at temperatures 45 °C; the highest density (> 150 000 m^–2, mainly Chironomidae) occurred at 34 °C, whereas biomass was highest (4.6 g m^–2, as dry weight) at 23 °C and species richness (15 species) was highest at 27 °C. The two predominant macroinvertebrate populations (the midge Tanytarsus sp. and the caddisfly Helicopsyche borealis) occurred at sites that were several degrees below their lethal thermal threshold, suggesting that a temperature buffer is maintained.     

Effects of total dissolved solids on growth and mortality predict distributions of stream macroinvertebrates

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The influence of highway construction on the macroinvertebrates and epilithic algae of a high mountain stream

The response of a high elevation Rocky Mountain stream to highway construction activities was investigated over a three-year period during the ice-free season. Suspended solids and the proportion of fine sediment in the substrate increased at impacted sites, but rapidly returned to levels similar to reference sites following cessation of construction activities. During snowmelt runoff when suspended solids levels increased, there was little or no sedimentation of fine particles, even in depositional areas. At impacted sites algal species diversity and the organic content of the epilithon were reduced, and the detrital component was increased. The epilithon recovered less rapidly than suspended solids or substrate. The macroinvertebrate community was altered by construction activities at some locations but not others, and was generally less severely affected than anticipated. However, where an alteration occurred, reduction in density, abundance, and diversity were apparent, and the taxonomic composition was modified. The severity of the response was a function of the flow regime and the timing and duration of the impact at a given site. The hydrologic regime and high gradient of the study stream appeared to ameliorate to some extent the potentially adverse effects of short-term perturbations engendered by highway construction activities.     

Development of a biotic index using stream macroinvertebrates to assess stress from deposited fine sediment

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Stable isotope analysis of macroinvertebrates and their food sources in a glacier stream

1. Food sources and trophic structure of the macroinvertebrate community along a longitudinal gradient were examined in a glacier stream of the Swiss Alps (Val Roseg). Analysis of multiple stable isotopes (δ¹³C and δ¹⁵N) and measurement of C : N ratios were used to differentiate between allochthonous and autochthonous organic matter.
2. Although isotopic signatures of algae varied widely among sites and dates, it was possible to discriminate between allochthonous and autochthonous food sources using a site-specific approach.
3. Dominant food sources of herbivorous invertebrates in all main channel sites were epilithic diatoms and the filamentous gold alga Hydrurus foetidus . Allochthonous organic matter was of some importance only in a groundwater-fed stream close to the floodplain margin.
4. Seasonal changes in the δ¹³C signature of the macroinvertebrates corresponded with seasonal changes in δ¹³C of the gold alga H. foetidus . This indicated that the energy base remains autochthonous throughout the year.
5. Because of limited food sources, feeding plasticity of the invertebrate community was high. Both grazers and shredders fed predominantly on algae, whereas gatherer-collectors seemed to be omnivorous.
6. The overall enrichment of δ¹⁵N was 2.25‰ ( r ²=0.99) per trophic level. On a gradient from the glacier site to a downstream forested site trophic enrichment was constant but variation in δ¹⁵N within trophic levels decreased.     

Variable effects of sediment addition on stream benthos

Two upper Piedmont streams were studied to determine the effects of road construction, especially sediment inputs. Benthic macroinvertebrate data suggest that the stream community responded to sediment additions in two different ways. Under high flow conditions the benthic fauna occurs mainly on rocky substrates. As sediment is added to a stream the area of available rock habitat decreases, with a corresponding decrease in benthic density. There is, however, little change in community structure. Under low flow conditions, stable-sand areas may support high densities of certain taxa. Density of the benthic macroinvertebrates in these areas may be much greater than the density recorded in control areas, and there are distinct changes in community structure.     

Colonization and succession of benthic macroinvertebrates in a new reservoir

The purpose of this study was to examine the colonization and succession of benthic macroinvertebrates in shallow areas (<7 m) of Lake Anna, a new mainstream impoundment in the southeastern U.S.A. Benthic macroinvertebrates were sampled for the first three years after filling by means of artificial substrates placed on the bottom and retrieved with SCUBA. Lake Anna was well colonized by benthic macroinvertebrates during the summer season immediately after impoundment. The total density of organisms increased in each of the first three years. Major changes in the fauna occurred between the first and second years, but the changes between the second and third years were more subtle. The fauna could be divided into two distinct groups based upon the time when the organisms were most consistently abundant. The first colonizers appeared to be dependent upon the components of the former terrestrial ecosystem for food and habitat. As autochthonous factors began to regulate succession, diversity increased and the dominant species shifted to an assemblage of second colonizers. These factors included: (1) decomposition of terrestrial vegetation and detritus leaving bare substrate, (2) sedimentation, (3) improved food quality of the organic matter in the sediment because of ingestion and egestion by the organisms themselves, (4) increased plankton populations, and (5) appearance of macrophytes. As the second colonizers became firmly established in the third year, distinct patterns of spatial distribution began to appear among species with similar niches.     

Colonization and succession of benthic macroinvertebrates in Arcadia Lake,a South-Central USA reservoir

Colonization and succession of benthic macroinvertebrates in Arcadia Lake, an urban reservoir, were studied for four years. Physicochemical conditions including water temperature, dissolved oxygen concentrations, pH, specific conductance, and Secchi disc depth were also recorded. Colonization of the reservoir occured fairly rapidly through a sequence of three invasions. The first, and most significant, colonists were primarily facultative species already present in streams and ponds that were inundated by the impoundment. Later arrivals tended to be limnophilic species that probably came from other bodies of water. Of 30 species encountered in a pre-impoundment collection, only six were still present three years following impoundment. Thirty-three additional benthic macroinvertebrates species invaded the area following impoundment. Dominant taxa in the reservoir included Dero nivea, Limnodrilus sp., Chaoborus punctipennis, Chironomus sp., and Procladius sp. Pollutants accumulating in this urban reservoir, including metals and pesticides, and siltation probably have kept benthic populations relatively low and possibly reduced potential species diversity.     

Effects of fine sediment inputs from a logging road on stream insect communities:a large-scale experimental approach in a Canadian headwater stream

A forest headwater stream was manipulated (logging road-crossing amended) to induce fine sediment inputs. Benthic inorganic sediment concentrations .particles 1.5–250 μm increased from a 2-year pre-disturbance average of about 800 g m^–2 to over 5000 g m^–2 that persisted for 3 years. Aquatic insect communities were examined over the 5-year study period in the manipulated and nearby reference streams. Overall, the effects of the fine sediment increases on aquatic insect communities were minimal. There were no significant effects of sedimentation on total aquatic insect abundance or biomass. An index of multivariate dispersion gave no evidence of community stress at the manipulated site. Multivariate ordination plots and time trends among univariate community metrics indicated only subtle changes in community structure. Among the univariate metrics (16 time series analyses in total), six gave evidence of a sediment impact on aquatic insect communities. Of those, the clearest indications of an effect were small reductions in diversity and richness of spring communities. These resulted from a significant decline in the proportion of spring shredders, accompanied by a significant increase in the percent Chironomidae. This large-scale experimental approach integrated the realism of a whole-stream study with the control of a manipulative study by including pre-manipulation measurements and excluding other confounding catchment disturbances. In this regard, it may provide a more realistic measure of benthic community level responses to sedimentation in streams at a magnitude associated with logging activity than many previous studies.     

Proficiencies of two artificial substrates in collecting stream macroinvertebrates

Proficiencies in collecting stream macroinvertebrates by two types of artificial substrates, #200 3M conservation webbing and cone-shaped concrete blocks, were compared with bottom net collections. Conservation webbing collected more individuals than cone substrates, but fewer taxa than either cone substrates or bottom nets. Diversity indices calculated for collections made with the three techniques were lowest for webbing collections, highest for net collections and intermediate for cone collections. It was concluded that collections made with webbing substrates gave an extremely distorted view of macroinvertebrate community balance due to a preponderance of net spinning and case building forms, and that cone substrates were better suited for use in the particular situation studied.Department of Biology, Virginia Polytechnic Institute and State University.Center for Environmental Studies, Virginia Polytechnic Institute and State University.     

Altitudinal distribution limits of aquatic macroinvertebrates: an experimental test in a tropical alpine stream

1. Temperature and oxygen are recognised as the main drivers of altitudinal limits of species distributions. However, the two factors are linked, and both decrease with altitude, why their effects are difficult to disentangle. 2. This was experimentally addressed using aquatic macroinvertebrates; larvae of Andesiops (Ephemeroptera), Claudioperla, (Plecoptera), Scirtes (Coleoptera) and Anomalocosmoecus (Trichoptera), and the amphipod Hyalella in an Ecuadorian glacier‐fed stream (4100–4500 m a.s.l.). The following were performed: (i) quantitative benthic sampling at three sites to determine altitudinal patterns in population densities, (ii) transplants of the five taxa upstream of their natural altitudinal limit to test the short‐term (14 days) effect on survival, and (iii) in situ experiments of locomotory activity as a proxy for animal response to relatively small differences in temperature (5 °C vs. 10 °C) and oxygen saturation (55% vs. 62%). 3. The transplant experiment reduced survival to a varying degree among taxa, but Claudioperla survived well at a site where it did not naturally occur. In the in situ experiment, Scirtes and Hyalella decreased their activity at lower oxygen saturation, whereas Andesiops and Anomalocosmoecus did so at a low temperature. The decrease in activity from a high to a low temperature and oxygen for the five taxa was significantly correlated with their mortality in the transplant experiment. 4. Together the present experiments indicate that even relatively small differences in temperature and oxygen may produce effects explaining ecological patterns, and depending on the taxon, either water temperature or oxygen saturation, without clear interacting effects, are important drivers of altitudinal limits.     

Macroinvertebrate/sediment relationships along a pesticide gradient in Danish streams

Twenty-nine Danish streams were investigated in September 1998. The streams drained catchments of varying hydrology, topography, soil type and land use. In each stream, the newly accumulated streambed sediment was sampled and subsequently analysed for pesticides. In each stream, five replicate macroinvertebrate samples were taken in the same sediments as the pesticide samples. In addition, five samples were taken in riffles to provide a complete picture of macroinvertebrate community composition. The number of detected pesticides reflected soil type and land use: in agricultural catchments on clay soils the average number of pesticides were 4.3±2.2; on sandy soils 2.6±1.0, while only 1.5±0.6 pesticides were found in streams without agricultural activities. The macroinvertebrate composition showed clear changes along this gradient of sediment pesticide concentrations. The number of the amphipod Gammarus pulex was negatively correlated with sediment pesticide concentration, while the number of Oligochaeta and Hirudinae was positively correlated. The findings indicate that pesticides have a potential to structure macroinvertebrate communities in Danish streams. However, agricultural impact is more than pesticides, and several other factors, such as channelisation, affect the macroinvertebrate community and these are not easily separated.     

Relationships between stream acidity and bacteria,macroinvertebrates, and fish: a comparison of north temperate and south temperate mountain streams,USA

A comparative study of relationships between stream acidity and bacteria, macroinvertebrates, and fish in the Adirondack Mountains of upper New York state and in the Southern Blue Ridge Mountains of eastern Tennessee, USA, was conducted. Although the study sites in both regions spanned a pH range from approximately 4.5 to 6.4, considerably greater seasonal variability in pH and higher monomeric Al concentrations characterized the Adirondack sites. Relationships between several biological characteristics and stream water acidity were similar in both regions, including lower production of epilithic bacteria and bacteria on decomposing leaves, lower leaf decomposition rates, lower density and generic richness of scraper/grazer macroinvertebrates, particularly Ephemeroptera, and lower fish abundance and survival in more acidic streams. Densities of total macroinvertebrates and densities of macroinvertebrates and bacteria inhabiting or closely associated with stream sediments were generally not related to stream water acidity.Regional differences occur in some of the relationships between biological characteristics and stream water acidity. Negative correlations between bacterial production on rocks and pH, between bacterial production on decomposing leaves and pH, and between densities of Ephemeroptera and scrapers and pH were stronger in the Adirondacks than in the Southern Blue Ridge. Higher Al concentrations in the Adirondacks may be responsible for the stronger relationships with pH there. The steeper slopes of the relationships between Ephemeroptera density and all forms of Al in the Adirondacks compared with the Southern Blue Ridge suggests that there may be some adaptation among a few acid/aluminum-tolerant species in the seasonally more constant acidic Southern Blue Ridge streams. Fish bioassays indicated longer survival times in acidic streams in the Adirondacks compared with the Southern Blue Ridge, but these results may be an artifact associated with the use in the Southern Blue Ridge of rainbow trout as the test species which is known to be more acid sensitive compared with brook trout, the test species used in the Adirondacks.     

Influence of seasonal variation on bioassessment of streams using macroinvertebrates

The EU Water Framework Directive requires assessment of the ecological quality of running waters using macroinvertebrates. One of the problems of obtaining representative samples of organisms from streams is the choice of sampling date, as the scores obtained from macroinvertebrate indices vary naturally between seasons, confounding the detection of anthropogenic environmental change. We investigated this problem in a 4th order calcareous stream in the western Carpathian Mountains of central Europe, the Stupavsky potok brook. We divided our 100 m study site into two stretches and took two replicate samples every other month alternately from each stretch for a period of 1 year, sampling in the months of February, April, June, August, October and December. Multivariate analysis of the macroinvertebrate communities (PCA) clearly separated the samples into three groups: (1) April samples (2) June and August samples (3) October, December and February samples. Metric scores were classified into two groups those that were stable with respect to sampling month, and those that varied. Of the metrics whose values increase with amount of allochthonous organic material (ALPHA_MESO, hyporhithral, littoral, PASF, GSI new, DSI, CSI), the highest scores occurred in February, April, October and December, while for metrics whose values decrease with content of organic material (DSII, DIS, GFI D05, PORI, RETI, hypocrenal, metarhithral, RP, AKA, LITHAL, SHRED, HAI) the highest values occurred in February, April, June and December. We conclude that sampling twice a year, in early spring and late autumn, is appropriate for this type of metarhithral mountain stream. Sampling in summer is less reliable due to strong seasonal influences on many of the metrics examined while sampling in winter is inappropriate for logistical reasons. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.     

Temporal variability of stream bioassessments using benthic macroinvertebrates

1. When using benthic macroinvertebrate communities for bioassessment, temporal variation may influence judgement as to whether or not a site is degraded.
2. In a survey of sixteen reference and sixteen test sites in the upper Thames River catchment area (UTRCA) in south-western Ontario, Canada, consistent differences between summer and winter samples were found for taxon richness (increase; P = 0.06) and the Family Biotic Index (decrease; P = 0.11). A bioassessment based on these results would indicate better water quality in the same streams in winter relative to summer. No consistent pattern of seasonal difference was detected for Simpson's Diversity and Equitability, or percentage Dominant Taxon.
3. The Reference Condition Approach to bioassessment uses predictive modelling to explain variation in reference communities with the environmental conditions at these sites as predictors. The community at a test site is compared with that predicted by the model. Several predictive models were constructed using simple geographic and habitat characteristics (i.e. catchment area, distance to source, stream width, substrate and habitat diversity) as predictors. By including season of sampling in the models, we increased their predictive power and the ability of the bioassessment to detect degradation. The best results were achieved when separate predictive models were built for each sampling season.     

Biological traits of stream macroinvertebrates from a semi-arid catchment: patterns along complex environmental gradients

1. The relationships between biological traits of macroinvertebrates and environmental characteristics were investigated in streams with contrasting physical, chemical or landscape level attributes. We used an ordination technique, RLQ analysis, which links an environmental table (R) with traits table (Q) through an abundance table (L) to investigate the relationship between habitat characteristics and biological traits.
2. A major environmental axis explaining the distribution of species and their distinctive biological features was obtained. This axis included variables of anthropogenic pressure (agricultural and urban uses) and natural variability (climatic and geologic) that are strongly intercorrelated in the study area, with a clear spatial component.
3. The attributes of species from frequently disturbed systems (small size, multivoltinism, diapause, ovoviviparity, etc.) were associated with semi-arid areas whereas traits common in more stable and favourable environments (large body size, semi-voltinism, isolated eggs, etc.) were found in upland forested areas.
4. The natural climatic variation was proposed as a disturbance axis of a theoretical habitat templet (driven by the intense hydrological disturbances typical of semi-arid streams), while anthropogenic pressure (mainly intensive agriculture) and high salinity, a natural consequence of geology, was proposed as an adversity axis. Different life-histories associated with contrasting environmental features were superimposed in this habitat templet.
5. The ecological–evolutionary scenario in which stream macroinvertebrates have evolved and by which their communities are organized, is closely linked to disturbance, environmental harshness and human pressure.     

Effects of the lampricide, 3-trifluoromethyl-4-nitrophenol (TFM) on the macroinvertebrates within the hyporheic region of a small stream

The effect of the lampricide, 3-trifluoromethyl-4-nitrophenol (TFM), on the benthic macroinvertebrates within the hyporheic region of Dam Creek, Ontario was investigated. Organisms were regularly found to a depth of 70 cm in the substrate throughout the study period. Of the eight major taxa found at both the treated and untreated sites only Tubificoidea exhibited a decrease in abundance attributable to TFM.One day after treatment, TFM concentrations were greatest at a depth of 55 cm, the greatest depth to which water samples were taken. The movement of TFM into the hyporheic region during the present study may be due to the large convective forces created by the rapid decrease in surface water temperature. These convective forces are usually greatest in the late fall and winter when TFM is not applied. The greater part of TFM stream treatments are carried out during the summer when surface water temperatures remain fairly constant. It is suggested that the hyporheic region may act as a refuge zone for benthic macroinvertebrates against the lampricide during most of the TFM application season.     

Short-term recovery of benthos following disturbance from stream habitat rehabilitation

The recovery of benthic macroinvertebrates after disturbance from stream rehabilitation was studied in the River Livojoki, northern Finland. The stream that had been channelized for log transport was rehabilitated on 1 July 1992 by digging holes and inserting boulders. We measured habitat characteristics and sampled benthic animals before and after rehabilitation, including an unrehabilitated control site. The immediate effect of rehabilitation was a slight decrease in the abundances of benthic insects. Recolonization occurred rapidly, within 10 days. Disturbance of the rehabilitation did not have a detectable effect on the macroinvertebrate community. Most species-level changes and community patterns reflected seasonal life history events. Timing of such rehabilitation work can be critical for the recovery rate, which depends on the colonization abilities of the species present after disturbance. We suggest that many disturbances (including minor floods and moderate rehabilitation procedures) may have only small, short-term effects on benthic communities. We emphasize the importance of considering seasonality in studies of disturbance in streams.     

The role of leaf litter macroinvertebrates in stream-floodplain dynamics

The floodplain has been viewed as a transitional system or ecotone between aquatic and terrestrial habitats. This research has evaluated the role of floodplain macroinvertebrates in the degradation of leaf litter in a Michigan woodland floodplain, and examined the interrelationships among floodplain-stream macroinvertebrates, microbial colonization and selected environmental factors. Although taxonomically different decomposer groups operate in both systems, their functional roles as leaf litter detritivores are basically the same. Leaf litter processing rates were compared and contrasted between the stream and adjacent floodplain using leaf packs and litter bags, respectively. In the stream, the major time period for detritus processing by invertebrates is in the fall and winter, while in the floodplain it is during the spring. Therefore, the sequence of events involved in processing are similar, yet the timing and rate of these events are strikingly different. An understanding of the significant ecological processes linking the stream and floodplain as complementary systems is discussed within the context of watershed management.