Hydraulic parameters and benthic invertebrate distributions in two gravel-bed New Zealand rivers

1. Benthic invertebrates were sampled over a matrix of about eighty combinations of mean velocity (10–150cms^?1) and depth (10–150cm) in two rivers that differed in substrate size variability. Vertical velocity profiles were measured at each sample site and substratum roughness was measured and estimated from percentage cover by stone size classes. The influence of depth on periphyton biomass was also measured. 2. The hydraulic and substrate data were used to investigate the correlations between conventional (mean velocity, depth, substrate size) and complex hydraulic variables (Froude number, shear velocity, and water column and boundary Reynolds number) that were either calculated from direct measurements or inferred from mean velocity, depth, kinematic viscosity and substrate roughness. The ecological relevance of these hydraulic variables was investigated by comparing their degree of correlation with invertebrate densities and community metrics. 3. The invertebrate variables had similar correlations with mean velocity and the complex near-bed hydraulic variables in the river with uniform cobble substrates. In the river with diverse substrates, however, average correlations with Froude number, and inferred shear velocity and boundary Reynolds number were 25–45% higher than with velocity. Of all the individual hydraulic parameters, the boundary Reynolds number, calculated from simple measures, was most strongly correlated with benthic invertebrate distributions and taxa richness. However, invertebrate distributions were more strongly correlated with predictions of multiple regression models, incorporating substrate size, depth and mean velocity, than with any single hydraulic variable. 4. Hydraulic influences on food availability and oxygen concentration in the benthos are likely mechanisms affecting the hydraulic preferences of several taxa. Lower periphyton biomass with depth, partly attributable to light attenuation, appeared to have a non-hydraulic influence on a collector-browser species.     

Macroinvertebrate community structure along gradients of hydraulic and sedimentary conditions in a large gravel-bed river

1. The spatial distribution of macroinvertebrate species was examined in relation to hydraulic and sedimentary conditions in a large gravel‐bed river, the Fraser River, Canada. Mean annual discharge in the Fraser River is 2900 m3 s?1 and annual flood discharge, due to snowmelt in May and June, averages 8760 m3 s?1.
2. Invertebrates were sampled from four water depths (0.2, 0.5, 1.5, 3.0 m) at various levels of discharge that together captured the spatial and temporal variability of the physical habitat. Several hydraulic (near‐bed shear velocity, Boundary Reynolds number, turbulence intensity, depth‐averaged velocity, Froude number, Reynolds number) and substratum variables (mean grain size, Trask's sorting coefficient, Nikuradse's roughness, percentage of fine sediment, and Shields entrainment function) were measured for each sample of macroinvertebrates. Concentrations of fine and coarse particulate organic matter were also assessed.
3. The physical habitat was characterized by a major gradient of hydraulic conditions that corresponded positively with increasing water depth and accounted for 52% of the total variation in the habitat data. Substratum conditions and the concentration of organic matter explained 24% of the total variation in the habitat data.
4. The distribution of invertebrates was correlated significantly with hydraulic variables and suggests that hydraulic conditions represent a major physical gradient along which the benthic community is organized. The distribution of organic matter and substratum texture were also important for some species. The spatial distribution of most species reflected morphological and trophic suitability to particular habitat conditions.
5. Hydraulic stress associated with foraging and maintaining position, as well as organic matter retention in coarse substrata, are probable mechanisms affecting the spatial distribution of macroinvertebrates.     

Identifying the scales of variability in stream macroinvertebrate abundance, functional composition and assemblage structure

1. Many natural ecosystems are heterogeneous at scales ranging from microhabitats to landscapes. Running waters are no exception in this regard, and their environmental heterogeneity is reflected in the distribution and abundance of stream organisms across multiple spatial scales. 2. We studied patchiness in benthic macroinvertebrate abundance and functional feeding group (FFG) composition at three spatial scales in a boreal river system. Our sampling design incorporated a set of fully nested scales, with three tributaries, two stream sections (orders) within each tributary, three riffles within each section and ten benthic samples in each riffle. 3. According to nested anova s, most of the variation in total macroinvertebrate abundance, abundances of FFGs, and number of taxa was accounted for by the among‐riffle and among‐sample scales. Such small‐scale variability reflected similar patterns of variation in in‐stream variables (moss cover, particle size, current velocity and depth). Scraper abundance, however, varied most at the scale of stream sections, probably mirroring variation in canopy cover. 4. Tributaries and stream sections within tributaries differed significantly in the structure and FFG composition of the macroinvertebrate assemblages. Furthermore, riffles in headwater (second order) sections were more variable than those in higher order (third order) sections. 5. Stream biomonitoring programs should consider this kind of scale‐dependent variability in assemblage characteristics because: (i) small‐scale variability in abundance suggests that a few replicate samples are not enough to capture macroinvertebrate assemblage variability present at a site, and (ii) riffles from the same stream may support widely differing benthic assemblages.     

Differences in litter characteristics and macroinvertebrate assemblages between litter patches in pools and riffles in a headwater stream

We compared the abundance of litter categories (coarse particulate organic matter 1–16 mm, leaves >16 mm, and small woody detritus 16–100 mm) and macroinvertebrate assemblages between natural litter patches in pools and riffles in a headwater stream. Litter patches in pools were formed under conditions of almost no current (<6 cm s⁻¹), but in riffles they were formed under variable current velocities (13–89 cm s⁻¹). Although the abundance of each litter category exhibited seasonal change, leaves were more abundant in riffles, and coarse particulate organic matter and small woody detritus were more abundant in pools throughout the study period. Macroinvertebrate assemblages in pools and riffles also changed seasonally but distinctly differed from each other. Shredders, collector-gatherers, and predators were the dominant functional groups in abundance in both pools and riffles, but the dominant shredders were caddisflies in pools and stoneflies in riffles. It is considered that the hydraulic conditions affected macroinvertebrate assemblages directly and indirectly through influences on the characteristics of litter retained in the patches. Our results suggest that the relative abundance of litter patches in pools and riffles largely affects the macroinvertebrate community structure of the headwater stream. Received: July 19, 2001 / Accepted: December 19, 2001     

Influence of morphohydraulic habitat structure on invertebrate communities (Ephemeroptera,Plecoptera and Trichoptera)

Fluvial geomorphology proposes the methodology of cognition and assessment of the riverine landscape and points to the possibilities of exploitation of its results in hydrobiological research. Habitat structure of two reaches of the Drietomica brook (Biele Karpaty Mts, Slovakia) was assesed at level of morphological and morphohydraulic units in the sense of the River Morphology Hierarchical Classification (RMHC)). Physical habitats were described by flow hydraulics and substrate properties as directly measured variables (current velocity, depth, substrate size) and related variables (flow type, Froude and Reynolds numbers). According to the shear stress (expressed by Fr and Re), the morphological units were divided into two main groups — with low shear stress — pools, glides, edgewaters, bar nooks and bars; with high shear stress — riffles, runs, rapids and scours; characterized also by different Ephemeroptera, Plecoptera and Trichoptera (EPT) communities. The EPT communities were analyzed in relation to the morphological, hydraulic and substrate characteristics of the stream channel. The main environmental gradient responsible for the variation in EPT fauna was found using Principal Component Analysis and was related to gradient of flow in term of current velocity and other hydraulic attributes covered by Fr and Re numbers. The EPT communities (by means of abundance, feeding types, current, microhabitat and zonation preferences) showed preferences for different morphological units, flow type and current velocity. Depth and substrate grain size showed only weak relation to EPT communities.     

Prediction of benthic macroinvertebrate composition using microhabitat characteristics derived from stereo photography

1. Benthic macroinvertebrate community and habitat features varying at the microscale ( 0.09 m ² ) were measured on one sampling occasion in the Thredbo River, Kosciusko National Park, NSW, Australia.
2. Most of the substratum habitat variables were measured in three dimensions using stereo photography. This is the first time that this method has been used so extensively for this purpose in freshwater ecology.
3. Microhabitat variables most related to benthic macroinvertebrate distribution and abundance were selected with multivariate analyses included rock length, height, area and water velocity. Individual variables alone could not account for macroinvertebrate variation, indicating the importance of interactions among variables.
4. Nine selected habitat variables were used to predict macroinvertebrate taxonomic content of additional sites. Predictions were 87% accurate for taxa with a > 50% chance of occurrence and 93% accuracy for taxa with a > 70% chance of occurrence. Variability observed in macroinvertebrate assemblages at the time of sampling was largely physically controlled and highly deterministic.     

Hydraulic requirements of stream communities: a case study on invertebrates

1. We relate invertebrate assemblages to direct measurements of near‐bed hydraulic conditions that integrate the complex three‐dimensional structure of flow close to the bottom. 2. We sampled invertebrate taxa from a Mediterranean River along a spatial gradient of increasing shear stress in two seasons (spring and autumn) with different hydrological conditions. We used a recently described ordination technique, Outlying Mean Index (OMI) analysis, to study the response of stream invertebrates to near‐bed hydraulic parameters. 3. The distribution of nearly 70% of the taxa collected was significantly related to the hydraulic parameters assessed. In both seasons, shear stress and Froude number were the most important hydraulic parameters whereas substratum particle size and bed roughness had less influence. Most of the 31 taxa collected in both seasons had a higher OMI (an index showing the deviation between the mean environmental conditions used by a taxon and the mean environmental conditions used by a theoretical taxon uniformly distributed across the studied gradient) in autumn (when flow was greater) and were found in samples with high shear stress and high Froude number. This suggests that benthic invertebrates changed their preferences according to flow conditions. 4. Taxon richness declined with increased shear stress during lower flow in spring. Finally, and agreeing with previous results, the proportion of filter feeders and collector‐gatherers was inversely related to shear stress. 5. Our results are a first step towards better habitat suitability models that could inform management decisions.     

Two lowland stream riffles – linkages between physical habitats and macroinvertebrates across multiple spatial scales

The physical structure of two riffles in a lowland Danish stream was studied and its importance for the composition and density of the macroinvertebrate communities was evaluated. The two riffles were visually assessed to be very similar, but measurements revealed that they differed in overall hydraulic conditions, stability, substratum composition and consolidation. Differences affected abundance of both burrowing and surface dwelling macroinvertebrates. The unstable unconsolidated riffle had higher total macroinvertebrate abundance (4137 m⁻² vs. 1698 m⁻²), diptera abundance (2329 m⁻² vs. 386 m⁻²) and total estimated species richness (31.7 vs. 28.8) as well as lower evenness (0.77 vs. 0.83) than the compact riffle. Among samples within the unconsolidated riffle, variations in macroinvertebrate communities were related to differences in mean substratum particle size. Here a linear log–log relationship existed between macroinvertebrate abundance, the abundance of EPT taxa and the median particle size (r ² _total = 0.46, p = 0.002; r ² _EPT = 0.73, p < 0.001). No similar relationships were evident on the consolidated riffle. Moreover, macroinvertebrate communities on the unconsolidated riffle were dominated by species with a high colonising potential. Despite being assessed to the same morphological unit, physical variation between riffles was surprisingly high as the riffles differed substantially with respect to consolidation, substratum heterogeneity and overall hydraulic structure. Macroinvertebrate community structure and composition also differed between riffles despite being drawn from the same species pool. The findings address the question if we use the correct methods and parameters when assessing the macroinvertebrate communities at the scale of the morphological unit.     

山地河流浅滩深潭生境大型底栖动物群落比较研究——以重庆开县东河为例

浅滩和深潭是山地河流中常见的河流生境结构。2011年7月,在重庆开县东河上游双河口-杉木桥河段,选择21个浅滩和深潭,调查大型底栖动物,研究影响不同生境中底栖动物组成、分布和多样性的生态机理。结果表明:调查河段浅滩和深潭中大型底栖动物分别为31种和24种,密度分别为450.62 个/m²和86.24 个/m²,生物量分别为2.88 g/m²和0.55 g/m²。浅滩有指示种11种,即纹石蛾(Hydropsyche sp.)、假蜉(Iron sp.)、假二翅蜉(Pseudocloeon sp.)、舌石蛾(Glossosoma sp.)、高翔蜉(Epeorus sp.1)、背刺蜉(Notacanthurus sp.)、Heterocloeon sp、锯形蜉(Serratella sp.)、朝大蚊(Antocha sp.)、等蜉(Isonychia sp.)、溪颏蜉(Rhithrogena sp.)。深潭指示种仅蜉蝣(Ephemera sp.)和黑大蚊(Hexatoma sp.)两种。刮食者为两类生境的优势功能摄食类群。浅滩中滤食者和刮食者比例显著高于深潭,而收集者和捕食者显著低于深潭。两类生境中大型底栖动物群落结构差异显著。浅滩中大型底栖动物的密度、生物量、丰富度指数、Shannon-Wiener 指数、改进的Shannon-Wiener指数均明显高于深潭。受地貌形态、水力特征和冲淤变化规律影响的生境稳定性和异质性差异是导致大型底栖动物群落差异的主要原因。     

Factors influencing macroinvertebrate assemblages in artificial subtropical ponds of Taiwan

Macroinvertebrate assemblages and its association with environmental factors at the 11 artificial subtropical ponds of Taiwan were examined using the multivariate analysis software STATICO. The aims of the study were to determine whether spatial and seasonal variation of macroinvertebrate assemblages changed seasonally, to examine which environmental factors determined the spatial and temporal structure of maroinvertebrate assemblages, and to compare between-pond variations in the taxon composition of macroinvertebrates. Macroinvertebrates were collected seasonally by a corer and a sweep net in 2007, and 13 physical and chemical factors were measured at the same time. A total of 31 macroinvertebrate taxa were collected during the sampling period, and the most dominant taxa were Chironomidae (31.7% of total animal abundance) and Tubificidae (22.4%). STATICO identified pond size, pond depth, sediment depth, and altitude as the major abiotic factors and Bufo melanostictus (Amphibia) as the major biotic factor to influence macroinvertebrate assemblages at these ponds. These factors changed with seasonality. For example, the abundance of B. melanostictus was the most important factor during the spring but became much less important in other seasons. According to the spatial distribution patterns of macroinvertebrate assemblages, macroinvertebrates could be split into two groups based on their dispersal. The active dispersers, such as insect taxa, were strongly associated with pond size and the passive dispersers, such as non-insect taxa, were strongly associated with the pond depth and/or sediment depth. The results of this study suggested that pond size might influence macroinvertebrate assemblages through their dispersal mechanisms and that the environmental factors which influenced the macroinvertebrate assemblages most changed with seasons in this study area.     

Stream community structure in relation to spatial variation: the influence of mesohabitat characteristics

Community structure of benthic macroinvertebrates was studied in six first- through fourth-order streams in northeast France, to elucidate changes in richness, abundance, diversity and evenness of mesohabitat assemblages as a function of environmental conditions. Patch samples were subjected to multivariate analyses to determine: (i) relationships among seven indices describing community structure (structure parameters); (ii) relationships among seven environmental variables; (iii) the relationship between community structure and environmental characteristics of patches. Faunal data showed that indices measuring the distribution of individuals among taxa (evenness, dominance) and richness are prominent in describing the structure of macroinvertebrate communities of mesohabitats. The analysis of environmental data demonstrated a major differentiating ability of current velocity and strong inter-relations among in-stream hydraulic-dependent parameters in structuring the mesohabitat environment. The co-structure (= relationship) between community organization and environmental variables indicated that substrate may be a primary determinant of community structure. Current velocity and water depth emerged as secondary factors. Trends in community structure were closely related to the spatial variability of mesohabitats. Species richness increased with habitat heterogeneity. Total abundance increased with trophic potentialities of patches. Equitability and diversity seemed to increase with patch stability. This revised version was published online in July 2006 with corrections to the Cover Date.     

Impacts of small hydropower plants on macroinvertebrate communities

Several nitrogen (N) field experiments were carried out in Nanjing and Anyang, China, to study the dynamic characteristics of biomass accumulation and N uptake, and to define the dilution curve for critical N concentration in cotton reproductive organ over the growth period. The results show that the total biomass and N accumulation were affected significantly by the rate of N application, exhibiting a sigmoid curve over time. The beginning time of fast N accumulation was 1–5 d earlier than that of biomass accumulation. The cotton lint yield was correlated with N concentration in the reproductive organ and fluctuated with varying N concentration, indicating the existence of luxurious N consumption in the cotton reproductive organ. The N concentration increased with increasing N application rates, and decreased gradually during the growth period. The relationship between biomass and N concentration can be described with a power equation. The patterns of the N concentration dilution model were consistent at both experimental sites, but the model parameter values of a differed. The results presented in this paper indicate that a critical N concentration dilution curve for cotton reproductive organ is independent of ecological region and can be described with a power equation.     

引水型电站对河流底栖动物群落结构的影响

于2005年10月对香溪河干流5个小水电站对河流底栖动物的影响进行调查研究,按影响情况,各电站设5个采样点.应用底栖动物物种组成、现存量、优势类群、功能摄食类群等参数,衡量小水电站对河流底栖动物群落结构的影响.在研究区域共采集到底栖动物4656条,平均密度为658ind./m2,蜉蝣目的四节蜉属(Baetis spp.)是该区域的优势类群.研究结果表明:电站的修建对河流水化学指标没有显著影响,但河流生境的物理因子(如流速和水深)都发生了较大的改变;对河流底栖动物的各方面均有一定的影响,特别是密度在5个样点间差异显著,而功能摄食类群中滤食者和捕食者的百分含量也有明显差异.另外,各项指标在5个样点间均有一致的变动趋势.相似性分析表明,坝下3号样点的群落组成差异最大,这意味着完全阻隔的坝不利于河流生物多样性的保护.     

Relating macroinvertebrate community structure to environmental characteristics and sediment contamination at the scale of the St. Lawrence River

There is still no assessment of the impact of sediment chemicals and environmental conditions on macroinvertebrates at the scale of the St. Lawrence River. In order to assess these impacts in the fluvial section of the St. Lawrence River including the Montreal harbour, the community structure of macroinvertebrates using different taxonomic aggregations (genus and family) and taxa attributes (abundance, presence–absence, indicator taxa) was assessed. The goal of the study was to determine the indicator taxa of macroinvertebrates along the fluvial continuum and relate changes in macroinvertebrate community to sediment chemical conditions and environmental characteristics of habitats using variance partitioning. This study also evaluated which taxonomic level and taxa attributes of macroinvertebrates were the most suitable for bioassessment of quality of sediments and habitat environment in the St. Lawrence River. Four different macroinvertebrate assemblages were found distributed along the fluvial continuum using either abundance or presence–absence data and genus or family levels. Indicator taxa characteristic of the different macroinvertebrate communities were associated with the sediment contamination gradient. However, habitat environmental characteristics (water masses, sulphur and DOC in sediments) had more influence on macroinvertebrate assemblages than sediment contamination. Our study confirms that family level analysis can give information comparable to the genus level analysis using presence–absence or abundance of macroinvertebrates, yet a higher number of indicator taxa were detected at the genus level.     

Macroinvertebrate community dynamics in a temperate European Atlantic river. Do they conform to general ecological theory?

Spatial and temporal dynamics of macroinvertebrate communities have usually been linked to several environmental and anthropic factors. The aim of this study is to elucidate how important are these factors in structuring macroinvertebrate communities from temperate regions. Regarding the macroinvertebrate number of taxa, the Habitat Template Model, the Dynamic Equilibrium Hypothesis and the Intermediate Disturbance Hypothesis will be tested in order to know how important the diversity of instream elements and the hydrological disturbance frequency are in defining the macroinvertebrate taxonomic richness. Thus, the structure and composition of macroinvertebrate communities were analysed in nine sites of the Pas River basin, a temperate Atlantic basin in northern Spain, during winter, spring, summer and autumn 2005, together with water physicochemical and environmental characteristics. Macroinvertebrate abundance increased downstream and during summer, probably favoured by lower hydraulic stress and water organic enrichment. As predicts the Habitat Template Model, the macroinvertebrate number of taxa was related to habitat heterogeneity. However, no clear relationship amongst macroinvertebrate richness and water quality was found. The macroinvertebrate taxonomic richness did not correspond exactly with the Dynamic Equilibrium Hypothesis and the Intermediate Disturbance Hypothesis because it was relatively high in the absence of hydrological disturbances (summer). Thus, disturbance events may play a secondary role in determining the seasonal dynamic of the number of taxa. However, hydrological disturbances can be considered the most important factors explaining the seasonal pattern of macroinvertebrate abundance. On the other hand, spatial patterns of macroinvertebrate community structure and composition were mainly determined by resource availability, hydraulic conditions, habitat heterogeneity and human alterations, whilst hydrological predictability and resource availability might play a major role in determining seasonal dynamics.     

The effects of habitat complexity and hydraulic conditions on the establishment of benthic stream macroalgae

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Inter-annual patterns in macroinvertebrate communities of wilderness streams in Idaho, U.S.A.

This study examined the inter-annual variation in macroinvertebrate assemblages in six wilderness streams in central Idaho over a 6-year period (1990–1995). Benthic macroinvertebrates and associated environmental correlates were sampled during baseflow each summer. Little environmental change, as assessed using coefficients of variation (CVs) for substrate size and embeddedness, width, depth and periphyton standing crops, occurred in the streams over the period of study. There was also little temporal change in macroinvertebrate assemblages based on the relative abundance of the 10 most abundant taxa, all shredder taxa and all plecopteran taxa. CVs for individual taxa were substantially greater than those of most community measures, with rare taxa contributing 30–50% of the variation for any one stream. Frequency distributions for taxa CVs excluding rare taxa were more normally distributed. Differences in assemblage structure among streams were attributed to stream size (shift in shredder assemblages) and temperature (shift in plecopteran taxa). These data indicate a long-term (multi-year) persistence in the macroinvertebrate composition of these pristine streams, thus supporting the premise that such streams are excellent references for use in long-term biomonitoring programs.     

Spatio-temporal changes of benthic macroinvertebrates in a cold Arkansas tailwater

This paper investigates spatial, seasonal and long-term changes in benthic macroinvertebrates in riffles of a cold tailwater. Cold tailwaters initially disrupt previously existing macroinvertebrate assemblages, but little is known about the long-term biological effects of a stable cold thermal regime. Assemblages at an upstream and downstream site of the Little Red River, Arkansas were investigated almost 30 years apart (1971 and 1999). Based upon published literature demonstrating the stability of benthic assemblages within unaltered environments, we predicted that the assemblages would be similar for each variable investigated. The benthic macroinvertebrate assemblages can be characterized as low diversity, with a total of 17 taxa identified. Isopods and Diptera comprised ~80% of all individuals. Other than chironomids, insects and particularly EPT taxa were poorly represented. Recent macroinvertebrate densities were significantly greater compared to the historical study period for the downstream site. Assemblage comparisons revealed moderate differences between study periods. Macroinvertebrate density was significantly greater upstream than downstream in the 1971 study period, yet taxa richness was significantly greater downstream for both study periods. Faunal composition was significantly different for upstream and downstream sites. Seasonal differences in numerical standing crop were identified for the 1971 upstream and 1999 downstream data sets. Low to moderate levels of seasonal, spatial and historical variation among benthic macroinvertebrate assemblages were attributed to environmental (temperature and flow) stability. The lack of aquatic insects other than chironomids over a 30-year period is indicative of the extreme constraints placed upon insect development within this cold regulated river.