The influence of catchment characteristics on suspended sediment properties

In order to investigate the influence of catchment characteristics on suspended sediment properties, suspended sediment samples were collected from the outlets of 60 small catchments located throughout Southwest England over a 14-month period. The catchments were selected to provide a representative range of topographic, land use, soil and geological characteristics. The suspended sediment samples were collected using time-integrating trap samplers, emptied at monthly intervals. Laboratory analysis focused on a selection of suspended sediment properties, including particle size composition, cation exchange capacity, and organic carbon, nitrogen, metal, radionuclide and phosphorus content. The results presented show that despite the substantial variability of catchment characteristics associated with the 60 sampling sites, the suspended sediment properties generally fell within a relatively limited range. However, statistical analysis identified significant spatial variability of suspended sediment within Southwest England, which in turn can be linked to catchment characteristics.     

Structure and composition of benthic macroinvertebrates of a tropical forest stream, River Nyamweru, western Uganda

Benthic invertebrates from River Nyamweru, a tropical forest stream in western Uganda were sampled bimonthly between April and December 1997 using a modified Hess Sampler. A total of 3708 benthic fauna from thirteen taxonomic orders were collected. Benthic samples were dominated by Diptera (mainly Chironomidae) representing over 60% of all the organisms, followed by Ephemeroptera. Benthic invertebrate densities ranged from 63 ± 9.03 organisms/m² to 300 ± 33.36 organisms/m², with higher densities occurring during the dry season and lower densities during the wet season. The benthic community structure in River Nyamweru reflected mainly collectors and scrapers as the most important groups (83%), while predators were very rare (3.1%). River discharge influenced benthic abundance, with more invertebrates at lower discharge and fewer invertebrates at higher discharge. The applicability of the River Continuum Concept to tropical forest stream situation is discussed.     

Effects of a pulp and paper mill on the ecology of the La Trobe River,Victoria, Australia

Four riverine animal communities were measured to assess the impact of extensively treated wastewater from a pulp and paper mill on the lower La Trobe River in Victoria, Australia. Benthic macroinvertebrates in channel and bankside habitats were sampled using a new air-lift corer. Population density was expressed in relation to substrate volume. Other communities measured at five sites upstream and downstream of the mill's wastewater outfall were the zooplankton, and the animals associated with submerged littoral vegetation. Ten environmental variables were also measured during the two sampling periods.A total of 50 benthic macro-invertebrate taxa were dominated by Oligochaeta, Chironomidae and Bivalvia. Benthic communities upstream and downstream of the outfall were very similar. Benthic samples showed large unexplained variation between stations and seasons, despite the similarity of stations and the stratified sampling design, but within-sample variation was small. There was some evidence that benthic faunal patchiness was associated with patterns of stream-bed scouring and deposition in periods of high flow. Littoral samples collected 28 taxa, dominated by Decapoda and Hemiptera. The benthic and littoral communities were quite distinct, with only three species common to both.Only two of the biological and environmental variables responded to wastewater from the mill: total dissolved solids rose by 20–25% over upstream levels; and zooplankton density increased by 2–3 orders of magnitude. It was concluded that wastewater treatment had successfully avoided the major environmental problems often associated with pulp and paper mills.     

The use of turbidimeters in suspended sediment research

Accurate characterisation of the trend in suspended sediment concentration in streams throughout runoff events requires a sampling interval much shorter than the one hour typically used. For logistical reasons this is not usually feasible, so continuously recording turbidimeters offer a potential alternative. The variety of correlations and relationships between sediment concentration and turbidity reported in the literature is not surprising in view of the many confounding effects present in natural stream systems. Data from five sites in a small forested catchment indicated variability in the turbidity-suspended sediment concentration relationship, but improvements were obtained by considering the effects of very fine sediment and background water colour. Throughout runoff events variations in sediment properties, organic acids concentration and turbulence can occur. It is concluded that a good linear relationship between turbidity and suspended sediment concentration should not necessarily be expected and any observed hysteresis could actually help explain erosion and transport processes. The detail and continuity of data generated by turbidimeters provides the opportunity for greater understanding of storm sediment dynamics, however, calibration requires careful consideration of site characteristics.     

Effects of experimental flow regulation on invertebrate drift and stranding in the Flathead and Kootenai Rivers,Montana, USA

Studies were conducted to determine the effects of experimental manipulations of discharge on invertebrate drift in two regulated rivers in northwestern Montana, USA. During these studies the discharge regime in the Flathead River was characterized by frequent flow fluctuations, while in the Kootenai River high discharge was maintained for much longer periods before flow was reduced to minimum discharge. The magnitude of the response of invertebrates to disturbance was different in the two rivers, in part because of the different frequencies of flow changes. Midstream invertebrate drift increased an order of magnitude during increasing discharges in the Flathead River but was not substantially increased during decreasing discharges. When the prior discharge regime had been sustained at high levels in the Kootenai River, invertebrate drift densities as high as 300 000/100 m³ were measured along the shoreline following reductions in discharge, both immediately after flow began to decrease and after dark on the same day. There was also more recolonization of shoreline areas and more stranding of insects following dewatering of nearshore regions when there had been sustained high discharge levels prior to the flow reduction. More insect stranding occurred during a faster rate of decrease in discharge (50 000 to 100 000 organisms m⁻²).     

Effects of sediment releases from a reservoir on stream macroinvertebrates

Effects of sediment release from Guernsey Reservoir on macroinvertebrates of the North Platte River, Wyoming, were investigated during summer 1981. Suspended solids concentrations during sediment release increased from <20 mg l^–1 to >300 mg l^–1. Because fine particulates remained in suspension, mean particle size of substrates was unaltered. Densities of chironomids decreased 90% + during sediment release but recovered to initial levels in 3 weeks after the release ended. Densities of mayflies and oligochaetes increased. Changes in benthic populations were highly correlated with increases in suspended solids.     

Community structure of benthic invertebrates in interior Alaskan (USA) streams and rivers

Taxonomic composition of benthic invertebrates in interior Alaskan streams and rivers is summarized from published and unpublished data. Diptera dominate the Alaskan stream fauna and constitute a larger proportion of the benthos in Alaskan streams than in streams of temperate North America. Plecoptera and Ephemeroptera are the next most abundant in Alaskan streams with Trichoptera generally very scarce. Several orders that occur regularly in streams of temperate North America are absent (or in very low abundance) in interior Alaskan streams: Hemiptera, Odonata, Megaloptera, Coleoptera. Net-spinning caddisflies, burrowing mayflies, and several families of stoneflies (Pteronarcyidae, Peltoperlidae and Perlidae) are conspicuous by their absence or extreme scarcity. Taxonomic composition varies significantly among hydrologic regions (major watersheds) and among stream types (springs, headwater streams, small rivers, and large rivers). Only two taxa (Chironomidae and Nemouridae) significantly increase in proportional contribution from south to north while many taxa decrease.     

Effects of the lampricide, 3-trifluoromethyl-4-nitrophenol (TFM) on the macroinvertebrates of Wilmot Creek

The effects of the lampricide, TFM, on the abundance of macroinvertebrates in the benthos of Wilmot Creek, a hardwater tributary to Lake Ontario, was examined over 1 year. Drifting macroinvertebrates were also collected before, during and after TFM treatment. Significant decreases in benthic abundance were exhibited by Dolophilodes sp., Tubificoidea, Cricotopus sp. and Macrotendipes sp. throughout the 350 days following treatment. Only the decrease in abundance of Dolophilodes sp. and Tubificoidea could be attributed to TFM treatment. Increases in drift abundance observed during treatment were generally an accurate indicator of TFM-sensitive macroinvertebrates. The most sentive taxa (Dolophilodes sp., Dugesia sp. and Tubificoidea) responded immediately following the introduction of TFM. Branchiobdellida, Diamesa sp., Dicranota sp., Lumbricidae and Nemouridae exhibited increases in drift abundance 8–10 h after the introduction of TFM, however, were considered less sensitive than the former taxa because a decline in their abundance in the benthos was not detected.The response of the benthic invertebrates found in this hardwater creek was similar to those observed during studies of softwater streams. Only the most severely affected taxa were not present in the benthos 350 days after treatment.     

Design and implementation of rapid assessment approaches for water resource monitoring using benthic macroinvertebrates

Abstract Benthic macroinvertebrates are the group of organisms most widely used for assessment of water resources. Rapid assessment approaches are intended to be efficient and cost effective; savings are found in reduced sampling and more efficient data analysis. Rapid bioassessment programmes have been quickly accepted and now cover most of the United States (US) and equivalent programmes cover all of the United Kingdom (UK). Rapid bioassessment programmes are designed to screen large regions, pinpointing trouble spots worthy of more detailed attention. Fundamental to all rapid bioassessment methods is the classification of streams so that comparisons can be made between reference areas and areas of concern, or test sites with similar characteristics. Both the UK and US approaches assess habitat characteristics. These characteristics are used to predict the fauna expected at a test site in the UK approach; in the US they are used as an aid to classification and interpretation of aquatic faunal data. Habitat assessments in the US are also used to determine whether poor water quality or degraded habitat are stressing the invertebrate communities. This is a major development in approaches to water resource assessment. In the UK, a model developed using multivariate statistics uses a few environmental variables thought to be unaffected by human activities to predict the fauna expected at a test site. The US approaches analyse data using several indices (or metrics) presumed to represent ecological features of interest. These indices have a range of sensitivities to different kinds of stress and must be calibrated for the area of interest. The two approaches have been developed in isolation but may have much to offer each other. Developing programmes are advised to consider both. Future needs include: development of procedures that can be applied to large rivers and to lakes; further refinement of ecological principles underlying metric choice; the inclusion of chemical criteria and toxicity tests to establish thresholds that indicate impairment; and development of criteria indicating the necessity for implementation of quantitative assessment studies.     

Ecological Effects of Serial Impoundment on the Cotter River, Australia

This study examines the ecological effects of serial impoundments (three dams) on a rocky upland stream in southeastern Australia. Physical, chemical and biological changes were quantified and interpreted within a three-level hierarchy of effects model developed previously by Petts [1984, Impounded Rivers. John Wiley and Sons, New York] and the Australian Rivers Assessment System (AUSRIVAS) to predict pre-dam biota. First-order effects were decreased median monthly discharges and floods of lesser magnitude following construction of the dams. No effect on water characteristics (pH, electrical conductivity and major ions) was evident. The second-order effect on channel morphology was a decrease in bank-full cross-sectional area by up to 75% because of reduced flows. At all sites, the predominantly cobble streambed was armoured and generally highly stable. The discharge required to initiate movement of the streambed surface sediments (38.9 m³ s⁻¹) was 40% less frequent since construction of the dams, implying alteration to the natural disturbance regime for benthic biota. Benthic algal growth appeared more prolific at sites directly below dams. Fewer macroinvertebrate taxa than expected and modified assemblages within 1 km of all three dams were third-order effects. Compared to reference conditions, macroinvertebrate samples from the sites directly below the dams had relatively more Chironomidae larvae, Oligochaeta and Acarina, and fewer of the more sensitive taxa, Plecoptera, Ephemeroptera, Trichoptera and Coleoptera. Biological recovery to the macroinvertebrate assemblage was evident within 4 km downstream of the second dam.     

Seasonal patterns of sediment loading and benthic invertebrate community dynamics in Lake Tanganyika, Africa

1. This study investigated the spatiotemporal dynamics of benthic invertebrate communities located close to the mouths of the Kalambo and Lunzua Rivers, at the southern end of Lake Tanganyika, and subject to varying degrees of sediment load. 2. Metrics of exposure to riverine sediments were associated inversely with abundance and diversity of benthic organisms at sampling locations adjacent to both river mouths, indicating a major effect of riverine sediments on the structure of near‐shore benthic communities. 3. A lower abundance of benthos was found at the mouth of the Lunzua River, which exports significantly higher sediment loads than the Kalambo. 4. Seasonal cycles of abundance and diversity in the benthos varied with distance from river mouths. This has important implications for monitoring programmes investigating benthic communities close to the mouths of rivers. 5. Our findings suggest that recent increases in the sediment loading of Lake Tanganyika, owing to anthropogenic catchment disturbance, impact significantly on biological diversity throughout the lake littoral, which provides habitat for the majority of species in the lake.     

Effects of increased flow in the main stem of the River Rhine on the invertebrate communities of its tributaries

1. We hypothesised that increased flow in the main stem of the River Rhine would influence the invertebrate communities of its tributaries and therefore investigated the invertebrate fauna of six tributaries over 2 years. 2. We collected quantitative invertebrate samples at three sites in each tributary: in the tributary mouth (influenced by Rhine water whenever flow in the Rhine exceeded mean annual level), in the zone reached by average floods (return period 1.5 years) in the Rhine (average flood level sites), and immediately upstream of the range of extreme Rhine floods (reference sites). Samples were taken in spring, summer and autumn of each year, at different flow levels of the Rhine. We also compared substratum composition at the three sites. 3. Tributary mouth sites had the finest substratum, the lowest total invertebrate density and the lowest taxon richness. At average flood level and reference sites, these three parameters were similar. 4. Taxa known to prefer larger rivers were mostly confined to the tributary mouth sites, and species preferring upland streams dominated at the average flood level and reference sites. 5. Multivariate analyses confirmed the influence of the Rhine on the tributary mouth sites. Invasive invertebrate species, which usually appear only in the Rhine itself, were found at the tributary mouth sites but not further up in the tributaries. 6. Our study shows that increased flow in the main stem of the Rhine influenced substratum composition and invertebrate communities at the tributary mouth sites. These results imply that the relationship between the main stem of a river and its tributaries is not one‐way (from tributary to main stem), but rather a two‐way interaction.     

In situ measurements confirm the seasonal dominance of benthic algae over phytoplankton in nearshore primary production of a large lake

1. Despite the recognition of its importance, benthic primary production is seldom reported, especially for large lakes. We measured in situ benthic net primary production by monitoring flux in dissolved inorganic carbon (DIC) concentration in benthic incubation chambers, based on continuous measurements of CO_2(aq) flux, alkalinity, and the temperature‐dependent dissociation constants of carbonic acid (K₁ and K₂). This methodology has the advantages of monitoring net primary production directly as change in carbon, maintaining continuous water recirculation, and having sufficient precision to detect change in DIC over short (i.e. 15 min) incubations, even in alkaline waters. 2. Benthic primary production on Cladophora‐dominated rocky substrata in western Lake Ontario was measured biweekly. Maximum biomass‐specific net photosynthetic rates were highest in the spring (2.39 mgC g Dry Mass^?1 h^?1), decreased to negative rates by early summer (?0.76 mgC g DM^?1 h^?1), and exhibited a regrowth in late summer (1.98 mgC g DM^?1 h^?1). 3. A Cladophora growth model (CGM), previously validated to predict Cladophora biomass accrual in Lake Ontario, successfully simulated the seasonality and magnitude of biomass‐specific primary production during the first cohort of Cladophora growth. Averaged over this growing season (May–Aug), mean areal net benthic production at the estimated depth of peak biomass (2 m) was 405 mg C m^?2 d^?1. 4. We measured planktonic primary production in proximity to the benthic study and constructed a depth‐resolved model of planktonic production. Using the CGM, benthic primary production was compared with planktonic primary production for the period May–Aug. Net benthic production from the shoreline to the 12 m contour (1–2 km offshore) equalled planktonic production. Closer to shore, benthic primary production exceeded planktonic primary production. Failure to account for benthic primary production, at least during abundant Cladophora growth, will lead to large underestimates in carbon and nutrient flows in the nearshore zone of this Great Lake.     

Urbanization,sedimentation, and the homogenization of fish assemblages in the Etowah River Basin,USA

We tested the hypothesis that urbanization alters stream sediment regimes and homogenizes fish assemblages in 30 sub-basins of the Etowah River. Sediment variables included average particle size (mean phi) of the stream bed, percent fines (<2 mm) in riffles, and baseflow turbidity (NTU). Homogenization was quantified as ratios of endemic to cosmopolitan species richness (E_r:C_r) and abundance (E_a:C_a). High NTU and fine stream beds were associated with homogenized assemblages (i.e., lower E:C ratios). Mean phi and NTU were significantly correlated with E:C ratios (r = –0.74 to –0.76) and, when combined using multiple regression, accounted for 73% of the variance in ratios. Stream slope strongly covaried with mean phi (r = –0.92) and percent fines in riffles (r = –0.79), but multiple regression models showed that urbanized sites had finer beds and riffles than predicted by slope alone. Urban land cover was the primary predictor of NTU (r ² = 0.42) and, combined with slope in multiple regression, explained 51% of the variance in NTU. Our results indicate that stream slope is a background variable predicting particle size and E:C ratios in these streams. Urbanization disrupts these relationships by transforming clear streams with coarse beds into turbid streams with finer beds. These conditions favor cosmopolitan species, ultimately homogenizing fish assemblages. Bed texture was linked to urbanization; however, NTU was the best indicator of urban impacts because it was statistically independent from slope.     

Variability and transport of suspended sediment,particulate and dissolved organic carbon in the tidal freshwater Hudson River

Measurements of suspended matter, particulate organic carbon and dissolved organic carbon were made over a three year period at stations spanning 150 km of the tidal freshwater Hudson River. Suspended matter concentrations varied from year-to-year and were not related to freshwater discharge. The increase in suspended matter with depth in vertical profiles suggests that, during medium to low flow conditions, resuspension of bottom sediments was as important a source of sediment as loadings from tributaries. Particulate organic carbon showed significant variability among stations, and both autochthonous primary production and detrital organic matter are contributing to POC standing stocks. Dissolved organic carbon represented over half of the total organic carbon in the water column and showed little variation among stations.Examining downstream changes in transport showed that there was significant production of both suspended matter and POC within the study reach during the ice-free season. Tributary loadings within the study reach do not appear to be the cause of these increases in downstream transport. Dissolved organic carbon behaved conservatively in that there was no evidence for net production or net consumption within the river.The spatial/temporal patterns and analyses of transport suggest that suspended matter and POC, but not DOC, were controlled to a significant extent by processes occurring within the river and were not simply related to loadings from outside.     

Trace metals in the benthic habitat of the Maarsseveen Lakes system,The Netherlands

The cadmium, zinc, lead and copper concentrations in benthic invertebrates and sediment were determined during two consecutive winters in the Maarsseveen Lakes system. A sequential extraction procedure was applied to estimate the bioavailability of the trace metals in the sediment. Based on the trace metal analyses of organisms and sediment, it is concluded that the Maarsseveen Lakes system has background levels of cadmium, zinc, lead and copper. As the majority of metals was present in geochemically more stable sediment phases, the sequential extractions provided limited additional information on trace metal bioavailability.     

Physical and geochemical characteristics of suspended solids,Wilton Creek,Ontario

To understand the nature of sediment-associated nutrient and contaminant transport dynamics in fluvial systems, a stormflow sampling program of suspended solids is reported for one water year in a representative rural diffuse source catchment of southeastern Ontario. Bulk samples of subsieve suspended solids were obtained using field-portable continuous-flow centrifuge apparatus. The physical and geochemical properties of suspended solids show no significant intersite differences over reaches of 1 500–2 000 m, yet display distinctive seasonal trends. Systematic seasonal changes in particle size, organic content, and Ca, P, Mn, Al, Ti, Fe, and K appear to reflect the changing role of partial area hydrology. Ca, P, and Mn are bioaccumulated by stream algae. Mineral signature is relatively constant over the year. This article first appeared in the Canadian Journal of Earth Sciences. Volume 18, pp. 1365–1379 (1981). Permission of the copyright holders to reprint the article is gratefully acknowledged.     

A simulation of the process of sedimentation of suspended solids in the Yoshii River estuary

A vertical plane 2D model has been applied to the Yoshii River estuary, Japan, as a means of simulating the process of sedimentation. The current velocity and isohaline distributions were well reproduced in the estuary and the model simulated the concentration distribution of suspended solids for 8 particle size classes by using a transport equation based only on physical processes. The changes of the particle size distribution in surface water were well reproduced by the model. The vertical velocity component plays an important role in the behaviour of suspended solids.     

Effects of sediment loads on the fish and invertebrates of a Sierra Nevada river, California

This study examined the effects of sedimentloadings from an abandoned hydraulic miningsite on potential trout spawning gravels, largeaquatic macroinvertebrates, and fish growth,survival and reproduction in the South YubaRiver (Nevada County) California. Effects ofsediment loadings, which are transported to theSouth Yuba River via Humbug Creek, wereinvestigated by comparing data from sites onthe South Yuba River upstream and downstream ofHumbug Creek. The study did not find anydeleterious effects of sediment loadings onfish survival and reproduction (based onsnorkel survey data), or large aquaticmacroinvertebrate populations. In addition,the lack of a significant difference in thepercentage of 0.30 to 3.35 mm material insubstrate samples suggests that sediment loadsare not affecting trout spawning gravels. Incontrast, Sacramento pikeminnow(Ptychocheilus grandis) growth appears to beaffected by both water temperatures andsediment loadings. Downstream of Humbug Creek,growth during the first year was significantlyfaster, based on calculated standard lengths atthe age 1 annulus, but condition factor wassignificantly lower than above Humbug Creek.     

Effects of the lampricide, 3-trifluoromethyl-4-nitrophenol (TFM) on the macroinvertebrates of a hardwater river

The effects of the lampricide, TFM, on the benthic macroinvertebrates in the Rouge River, a hardwater tributary to Lake Ontario was examined at 1 untreated and 2 treated sites over a 7 month period. Drift samples were collected from one one of the treated sites during the 5 days bracketing treatment. Significant decreases in relative abundance attributable to TFM were recorded for Chimarra sp., Dugesia sp. and Tubificoidea 2–19 d following treatment. Large reductions were also exhibited by Caenis sp. and Lumbricidae. Two-thirds of the Chironomidae genera and Nematoda tended to decline in abundance 2 d after treatment at only one of the treated sites, probably due to a 2.5 h longer treatment. This decline was followed by a significant increase to greater than pretreatment abundances 17 d later undoubtedly as a result of an upward migration of macroinvertebrates from within the hyporheos. Partial recolonization of the TFM-sensitive benthic taxa was evident 19 d after lampricide treatment with complete recolonization 6.5 months later. With the exception of Caenis sp. those taxa in the present study found to be TFM-sensitive were in accordance with those found in softwater field studies. Chimarra sp., Dugesia sp., Hemerodromia sp., Lumbricidae and Tubificoidea exhibited substantial increases in drift abundance resulting from TFM treatment. Generally drift abundance of the taxa returned to pretreatment levels within 12 h following the completion of treatment. The drift abundance of Chimarra sp. and Dugesia sp. remained above normal throughout the rest of the sampling period likely due to continued irritation or mortalities induced by the presence of TFM in the substrate. Generally, drift was a good indicator of those taxa likely to experience a decline in abundance as a result of TFM treatment.