Macroinvertebrate assemblages in Andean Patagonian rivers and streams: environmental relationships

Macroinvertebrate communities from 29 streams and rivers of the mountain and the Andean Patagonian Plateau were analyzed. Samples were collected from six river basins, which were part of four different biozones of the Patagonian Ecoregion. Samples from mountain streams were dominated by Plecoptera, Ephemeroptera, Trichoptera and Diptera, while plateau rivers where mainly Diptera, Oligochaeta and Mollusca. Total invertebrate abundance ranged from 7 to 12249 ind.m^–2. Elmidae, Paratrichocladius, Chironomus, Smicridea annulicornis, Parasericostoma ovale and Meridialaris laminata were the most abundant insect taxa, while Nais communis and Hyalella curvispina were the most abundant non-insect taxa. Species-environmental relationships were examined using Canonical Correspondence Analysis. Current speed, conductivity, substrate size and abundance of aquatic plants, were identified as the major variables structuring faunal assemblages. Regression analyses revealed that species richness was negatively correlated with latitude, and positively correlated with water temperature and altitude. Macroivertebrate abundance increased with conductivity, altitude and water temperature. These results suggest that habitat heterogeneity was the strongest predictor of macroinvertebrate assemblages, but species richness could be predicted at a landscape scale using topographical and climatic features.     

Substrate specificity,environmental degradation and disturbance structuring macroinvertebrate assemblages in neotropical streams

Structure and composition of benthic macroinvertebrate assemblages were investigated in seven sampling sites with a gradient of environmental integrity and water quality conditions. Composite samples of the four most representative substrates were collected in order to characterize the riffle-pool dynamic in each sampling site. Spatial and temporal variability of macroinvertebrate assemblages were analyzed at two scales: using substrates and grouping samples for comparing sampling sites. Distribution of macroinvertebrates was influenced primarily by substrate type, but also by environmental integrity, water quality and sampling period. Species occurrence was highly dependent on substrate type. At local spatial scale, environmental degradation measured by the Riparian Channel Environmental Inventory and water chemistry were the determinants of assemblage patterns. We evaluated to which extent the substrates were influenced by environmental integrity and water chemistry, and we found that degradation influenced significantly the macroinvertebrate fauna on the four substrate types, although they were not responding to the same variables. Our results show that qualitatively communities were not influenced by seasonal changes, but abundance was stochastically dependent on rainfall.     

Benthic macroinvertebrates in Swedish streams: community structure, taxon richness, and environmental relations

Spatial scale, e.g. from the stream channel, riparian zone, and catchment to the regional and global scale is currently an important topic in running water management and bioassessment. An increased knowledge of how the biota is affected by human alterations and management measures taken at different spatial scales is critical for improving the ecological quality of running waters. However, more knowledge is needed to better understand the relationship between environmental factors at different spatial scales, assemblage structure and taxon richness of running water organisms. In this study, benthic macroinvertebrate data from 628 randomly selected streams were analysed for geographical and environmental relationships. The dataset also included 100 environmental variables, from local measures such as in-stream substratum and vegetation type, catchment vegetation and land-use, and regional variables such as latitude and longitude. Cluster analysis of the macroinvertebrate data showed a continuous gradient in taxonomic composition among the cluster groups from north to south. Both locally measured variables (e.g. water chemistry, substratum composition) and regional factors (e.g. latitude, longitude, and an ecoregional delineation) were important for explaining the variation in assemblage structure and taxon richness for stream benthic macroinvertebrates. This result is of importance when planning conservation and management measurements, implementing large-scale biomonitoring programs, and predicting how human alterations (e.g. global warming) will affect running water ecosystems.     

Benthic diatom assemblages in mountain streams: community structure in relation to environmental and human pressures

The objective of this study was to determine the environmental factors that best explain the distribution and community composition of benthic diatoms in undisturbed mountain streams in the Eastern Highlands of Zimbabwe. Benthic diatoms were sampled during the dry season from 21 sampling sites established along altitudinal gradient of the study rivers. A total of 119 diatom species belonging to 38 genera and twelve families were recorded for all the 21 sites sampled. No significant differences were observed in species diversity and equitability amongst the three river systems. However, species richness, diversity and equitability decreased significantly along the longitudinal gradient of the rivers, with the highest richness, diversity and evenness being recorded in the upper reaches. Temperature, velocity, NO₃^? and Ca²⁺ levels were strongly associated with changes in diatom communities in the three rivers. Inventory of diatom communities has applications in many fields of biological research including conservation and biological monitoring of ecosystem changes.     

Benthic macroinvertebrate assemblages of coastal and continental streams and large rivers of southwestern British Columbia, Canada

In southwestern British Columbia (BC, Canada) and within a relatively small geographic area, lotic environments range from streams in coastal rainforests, to streams in arid continental grasslands, to very large rivers. Little is known about the invertebrate communities in large rivers in general, or in the streams of continental BC. The purpose of this study was to determine whether the benthic invertebrate community structure changes spatially between small coastal and small interior streams; between small streams versus large rivers; and whether changes in the benthic community are related to the environmental conditions. Kicknet samples and environmental data were collected from three coastal streams, three continental streams and two large rivers (discharge of 781 and 3620 m³/s, respectively). The large river sites had low invertebrate abundance, species richness and diversity, relative to the small streams. The coastal streams had the highest species richness and the continental streams had the highest invertebrate abundance. A number of taxa were specific to each class of stream. Invertebrate abundance decreased with river size, and increased with elevation, pH, conductivity, alkalinity, NO₂NO₃-N, total Kejldahl nitrogen and percent carbon in suspended solids.     

Concordance between ecotypes and macroinvertebrate assemblages in Mediterranean streams

1. According to the guidelines of the European Water Framework Directive, assessment of the ecological quality of streams and rivers should be based on ecotype-specific reference conditions. Here, we assess two approaches for establishing a typology for Mediterranean streams: a top-down approach using environmental variables and bottom-up approach using macroinvertebrate assemblages.
2. Classification of 162 sites using environmental variables resulted in five ecotypes: (i) temporary streams; (ii) evaporite calcareous streams at medium altitude; (iii) siliceous headwater streams at high altitude; (iv) calcareous headwater streams at medium to high altitude and (v) large watercourses.
3. Macroinvertebrate communities of minimally disturbed sites ( n  = 105), grouped using UPGMA (unweighted pair-group method using arithmetic averages) on Bray–Curtis similarities, were used to validate four of the five ecotypes obtained using environmental variables; ecotype 5, large watercourses, was not included as this group had no reference sites.
4. Analysis of similarities ( anosim ) showed that macroinvertebrate assemblage composition differed among three of the four ecotypes, resulting in differences between the bottom-up and top-down classification approaches. Siliceous streams were clearly different from the other three ecotypes, evaporite and calcareous ecotypes did not show large differences in macroinvertebrate assemblages and temporary streams formed a very heterogeneous group because of large variability in salinity and hydrology.
5. This study showed that stream classification schemes based on environmental variables need to be validated using biological variables. Furthermore, our findings indicate that special attention should be given to the classification of temporary streams.     

Decreased habitat specialization in macroinvertebrate assemblages in anthropogenically disturbed streams

Habitat specialists are considered to be more sensitive to anthropogenic disturbance than habitat generalists. However, a number of studies have shown that habitat specialists can be tolerant to or even benefit from environmental degradation, suggesting that the effect of disturbance on distributions and abundances of habitat generalists and specialists can be unpredictable. In this study, we assessed the effects of anthropogenic disturbance on the degree of specialization of stream macroinvertebrates in boreal streams. We first measured the niche width for each macroinvertebrate species using the Outlying Mean Index (OMI) analysis and then, using independent data sets of near-pristine and anthropogenically altered streams, we examined the effects of human disturbances on stream macroinvertebrates with different tolerances to environmental conditions. As expected, human disturbance significantly decreased the level of the specialization in stream macroinvertebrate assemblages, and taxa with narrow environmental tolerances were more sensitive to disturbance than taxa with wide tolerances. Despite being more sensitive to disturbance, taxa with narrow environmental tolerances were locally more abundant than tolerant taxa in near-pristine streams, indicating their better performance in their optimal environments. However, many tolerant taxa decreased in their occurrence in disturbed streams, suggesting that habitat generalists also tend to negatively respond to disturbance. Species-rich assemblages harboured more taxa with narrow tolerances compared with species poor assemblages, suggesting a high conservation value of streams with diverse macroinvertebrate assemblages. Consistent with findings for many biological groups, our results indicate that macroinvertebrate species specialised in certain habitats are more sensitive to environmental degradation than habitat generalists. However, contrary to many previous studies, our results suggest that only a few species are likely to benefit from anthropogenic disturbance and, therefore, environmental degradation does not necessary result in macroinvertebrate assemblages composed of a few tolerant taxa.     

Benthic macroinvertebrate distributions in the riffle-pool communities of two east Texas streams

The benthic macroinvertebrate riffle-pool communities of two east Texas streams were sampled monthly for a period of one year. In contrast to previous studies in primarily upland areas, pools in Alazan Creek and Bernaldo Bayou contained significantly higher densities and biomass, as well as a significantly higher diversity and number of taxa. The majority of taxa collected could be characterized as pool adapted organisms, with the Diptera, Ephemeroptera, Coleoptera, and Odonata having greater numbers in pools. Perlesta, Baetis, and Cheumatopsyche were the only genera to have significant numbers in riffles at both sampling sites. A greater number of taxa were restricted to pools at both sampling locations, and although an unstable, sandy substrate was a factor in limiting colonization of riffles, riffles were not as productive as pools even in the presence of suitable substrate conditions. A cluster analysis based on similarity indices indicated that like habitats between streams were more similar to each other, than were adjacent riffle-pool complexes within streams.     

Effects of episodic acidification on macroinvertebrate assemblages in Swiss Alpine streams

1. Despite long‐standing ecotoxicological evidence that episodes of acidification in streams are important biologically, there is still uncertainty about their effects on invertebrate communities. We surveyed 20 streams in an acid sensitive Alpine area (Canton Ticino, Switzerland), where episodes are driven by snowmelt in spring and by rainstorms at other times of the year. Samples of water and macroinvertebrates were collected in pre‐event conditions (winter and summer) and during periods of high flow (spring and autumn). 2. Using pH, [Ca²⁺] and [Alⁿ⁺], streams were clustered into six acid–base groups that were either well buffered (groups 4–6), soft‐water with stable pH (group 3), or poorly buffered with low pH at high flow (groups 1 and 2). 3. Severe episodes occurred during snowmelt, when the group 1 streams became acidic with pH down to 5.0 and [Alⁿ⁺] up to 140 μg L^?1. pH declined to 6.2 in streams of group 2, but remained > 6.6 in groups 3–6. 4. Detrended canonical correspondence analysis showed that the streams sensitive to episodes (groups 1 and 2) had different invertebrate assemblages from well‐buffered sites (groups 4 and 5) or soft‐water stable streams (group 3), with faunal differences largest following spring snowmelt. Empididae, Isoperla rivulorum, Rhithrogena spp. and Baetis spp. were scarce in streams sensitive to episodes (groups 1 and 2). By contrast, Amphinemura sulcicollis was scarcer in hard‐water streams (groups 4–6). Taxonomic richness was lower in the episodic streams of group 1 than in other streams. 5. Together, these results indicate clear biological differences between acid‐sensitive streams with similar low‐flow chemistry but contrasting episode chemistry. Severe episodes of acidification appear to affect macroinvertebrate assemblages in streams in the southern Swiss Alps.     

Benthic macroinvertebrate assemblages detect the consequences of a sewage spill: a case study of a South American environmental challenge

Limnology - Benthic macroinvertebrate assemblages are used to assess anthropogenic stressors and pressures globally—although considerable spatial and temporal variability in those assemblages...     

Longitudinal macroinvertebrate assemblages in contrasting discontinuities: the effects of damming in tropical streams

The study assessed the impact of damming on water quality and macroinvertebrate assemblages. It also assessed the response of macroinvertebrate‐based indices of water quality to damming. Macroinvertebrate community and physicochemical variables data were collected from 86 sites. Twenty‐nine sites downstream of dams were compared with 27 sites above impoundments and 30 sites on nearby unregulated streams. Of the downstream sites, 13 were situated <1 km from a dam while the other 16 were situated >1 km from a dam. A decrease in temperature, dissolved oxygen, conductivity and total dissolved solids was observed in sites immediately downstream of impoundments. Macroinvertebrate community structure and South African Scoring System (SASS) scores closely followed the damming‐induced changes in water quality. However, water quality variables, macroinvertebrate community structure and SASS scores reverted back to typical upstream conditions in distances around 1 km from dams. Stream recovery from dam‐induced changes was demonstrated with streams recovering at distances around 1 km from the point of regulation in corroboration with predictions of the serial discontinuity concept (SDC). These dam‐induced changes also reflected themselves in SASS scores suggesting potential usefulness of SASS in monitoring ecological integrity of tropical rivers following disturbances like damming.     

Spatio-temporal variation in macroinvertebrate assemblages of glacial streams in the Swiss Alps

1. Changes in water chemistry, benthic organic matter (BOM), and macroinvertebrates were examined in four different glacial streams over an annual cycle. The streams experienced strong seasonal changes in water chemistry that reflected temporal changes in the influence from the source glacier, especially in water turbidity, particulate phosphorus and conductivity.
2. Nitrogen concentrations were high (nitrate-N values were 130–274 μg L^–1), especially during spring snowmelt runoff. Benthic organic matter attained >600 g m^–2 dry mass at certain times, peaks being associated with seasonal blooms of the alga Hydrurus foetidus .
3. Macroinvertebrate taxon richness was two to three times higher (also numbers and biomass) in winter than summer suggesting winter may be a more favourable period for these animals. Benthic densities averaged 1140–3820 ind. m^–2, although peaking as high as 9000 ind. m^–2. Average annual biomass ranged from 102 to 721 mg m^–2, and reached >2000 mg m^–2 at one site in autumn.
4. Taxa common to all sites included the dipterans Diamesa spp. and Rhypholophus sp., the plecopterans Leuctra spp. and Rhabdiopteryx alpina , and the ephemeropterans Baetis alpinus and Rhithrogena spp. Principal components analysis clearly separated winter assemblages from those found in summer.     

Microbial assemblages reflect environmental heterogeneity in alpine streams

Alpine streams are dynamic habitats harboring substantial biodiversity across small spatial extents. The diversity of alpine stream biota is largely reflective of environmental heterogeneity stemming from varying hydrological sources. Globally, alpine stream diversity is under threat as meltwater sources recede and stream conditions become increasingly homogeneous. Much attention has been devoted to macroinvertebrate diversity in alpine headwaters, yet to fully understand the breadth of climate change threats, a more thorough accounting of microbial diversity is needed. We characterized microbial diversity (specifically Bacteria and Archaea) of 13 streams in two disjunct Rocky Mountain subranges through 16S rRNA gene sequencing. Our study encompassed the spectrum of alpine stream sources (glaciers, snowfields, subterranean ice, and groundwater) and three microhabitats (ice, biofilms, and streamwater). We observed no difference in regional (γ) diversity between subranges but substantial differences in diversity among (β) stream types and microhabitats. Within‐stream (α) diversity was highest in groundwater‐fed springs, lowest in glacier‐fed streams, and positively correlated with water temperature for both streamwater and biofilm assemblages. We identified an underappreciated alpine stream type—the icy seep—that are fed by subterranean ice, exhibit cold temperatures (summer mean <2°C), moderate bed stability, and relatively high conductivity. Icy seeps will likely be important for combatting biodiversity losses as they contain similar microbial assemblages to streams fed by surface ice yet may be buffered against climate change by insulating debris cover. Our results show that the patterns of microbial diversity support an ominous trend for alpine stream biodiversity; as meltwater sources decline, stream communities will become more diverse locally, but regional diversity will be lost. Icy seeps, however, represent a source of optimism for the future of biodiversity in these imperiled ecosystems.     

Benthic macroinvertebrate community structure in relation to food and environmental variables

The relative contribution of sediment food (e.g. organic matter, carbohydrates, proteins, C, N, polyunsaturated fatty acids) and environmental variables (e.g. oxygen, pH, depth, sediment grain size, conductivity) in explaining the observed variation in benthic macroinvertebrates is investigated. Soft bottom sediments, water and benthic macroinvertebrates were sampled in several water systems across The Netherlands. The variance partitioning method is used to quantify the relative contributions of food and environmental variables in structuring the benthic macroinvertebrate community structure.It is assumed that detritivores show a significant relationship with sediment food variables and carnivores and herbivores do not. The results of the variance partitioning method with data sets containing only detritivores, herbivores or carnivores confirm this assumption. This indicates that the variance partitioning method is a useful tool for analyzing the impact of different groups of variables in complex situations. Approximately 45% of the total variation in the macroinvertebrate community structure could be explained by variables included in the analyses. The variance partitioning method shows that sediment food variables contributed significantly to the total variation in the macroinvertebrate dataset. The relative importance of food depends on the intensity of other environmental factors and is lower on broad spatial scales than on smaller scales.The results of the partitioning depend on the selected variables that are included in the analyses. The method becomes problematic in case variables from different groups of variables (e.g. one food variable and one environmental variable) have a high inflation factor and thus are collinear. The choice of the variable that is left out impacts the variance allocated to the different groups of variables.The variance partitioning method was able to detect the spatial scale dependent contribution of food variables in structuring macroinvertebrate communities. This spatial scale dependency can also be caused by the size, the composition, and the heterogeneity of the dataset. Performing extra analyses in which specific samples are removed from the original dataset can give insight in under- or overestimation of the impact of certain factors and offers the possibility to test the robustness of the obtained results.     

Benthic insects in Swedish lake-outlet streams: patterns in species richness and assemblage structure

1. We studied how species richness of three hierarchical insect species groups, namely all benthic, lotic and filtering taxa, were related to a number of environmental variables in a data set from fifteen Swedish lake outlets. 2. In partial least-squares analyses, we found that size-related factors (stream width, discharge) and velocity-related factors (current velocity, substratum particle size) were positively associated, and productivity-related factors (chlorophyll a, seston energy, conductivity) negatively associated, with the species richness of the three groups. 3. The weak and negative relationship of richness with productivity largely negated theoretical predictions, whereas the species-environment results corroborated earlier findings from running water systems. 4. The most important factors associated with the species composition of the lake outlets studied included pH, lake area, discharge, channel width and detritus. 5. Of the filter feeders, most species of blackflies (Diptera: Simuliidae) showed a negative relationship with pH. 6. A nested subset analysis demonstrated that species-poor sites did not have a subset of species found at more species-rich sites in any of the three hierarchical groups.     

Realism of model ecosystems: an evaluation of physicochemistry and macroinvertebrate assemblages in artificial streams

Ecological realism is an important yet rarely reported feature of model ecosystems. In this case study, we assess the realism of four outdoor artificial stream mesocosms (4 m²) bordering a chalk river in southern England. Comparisons of physiochemical conditions and benthic macroinvertebrate assemblages were made between the mesocosm units and the parent water body, a side arm of the River Frome. Physicochemistry of the mesocosm replicates was similar to that of the source stream, with congruent temporal variation evident between the real system and each of the models. The high realism of the mesocosms was explained by the outdoor location and close physical proximity of the array to the source stream, and the short mesocosm residence time of water sourced from the parent feeder system. Mesocosms supported a diverse array of benthic macroinvertebrates (60 families from 14 taxonomic orders), including all macroinvertebrate families in the source stream. Individual mesocosms contained a mean of 89% of source stream biota. We conclude that once-through mesocosms can be satisfactory analogues of natural systems, particularly where model and natural scales overlap. Handling editor: D. Dudgeon     

Habitat characteristics and macroinvertebrate assemblages in boreal forest streams: relations to catchment silvicultural activities

We compared the stream habitat characteristics and macroinvertebrate assemblages of boreal headwater streams in both the Finnish and the Russian parts of a single river basin, the Koitajoki River. Over the last 50 years, the Finnish side of the catchment has been managed using modern forestry techniques, whereas Russian side has remained nearly unexploited and is near to its natural state. Differences in silvicultural activities were observed to contribute to differences in habitat structure. The channel habitats were in fairly natural state in the Russian reference streams, whereas the impacted Finnish sites were cleared and straightened. In comparison with the impacted channels, the abundance of coarse woody debris (CWD) was 10–100-fold higher in the reference streams. Implications on the forestry-induced deterioration of water quality were also observed. On the contrary, only small differences in macroinvertebrate assemblages were detected. Despite the lower amount of retentive structures (CWD), significantly higher relative abundance of shredders was observed in the forestry-impacted streams. Otherwise the zoobenthic communities were quite similar in the two subcatchments. We suggest that several mechanisms may explain this similarity: (1) community structure is controlled by naturally acidic conditions, (2) the adverse impacts of forestry on habitat structure and water quality of streams may be compensated by increased input of deciduous litter and organic compounds from drained, structurally young riparian forests and (3) macroinvertebrate species have flexible feeding habits and may thus readily adapt to changing conditions.     

城市溪流中径流式低坝对底栖动物群落结构的影响

调查了浙江省安吉县内具径流式低坝的城市溪流(6个样点)和参照溪流(3个样点)的底栖动物群落,目的是了解城市溪流底栖动物群落结构退化规律和径流式低坝(2—3 m)对城市溪流底栖动物群落组成与结构的影响。结果表明,参照样点的底质组成以大石块(35.92%)和卵石(33.66%)为主,城市溪流以砾石为主(57.97%)。城市溪流水温和电导率显著高于参照溪流,TN和TP高于参照溪流。底栖动物总分类单元数和EPT分类单元数显著低于参照溪流。城市溪流河道内水坝上下游之间的流速(P=0.273)和宽深比(P=3.92)无显著差异。坝下游水体中的TP高于坝上游,电导率、溶解氧、pH值和水温在坝上下游之间几乎一致。除BI指数坝下游高于坝上游外,坝上下游间底栖动物总分类单元数、EPT分类单元数以及多样性指数、优势度和均匀度指数没有显著差异。但坝下游的耐污类群比例显著高于坝上游,敏感类群比例则显著低于坝上游。与坝上游相比,坝下游捕食者比例上升和集食者比例下降。NMDS结果进一步表明,城市溪流内水坝的建设导致坝上下游底栖动物群落物种组成明显改变。     

A comparison of benthic macroinvertebrate assemblages among different types of alpine streams

1. Benthic macroinvertebrate assemblages were compared among a diverse array of first‐order alpine tundra streams of the Swiss Alps. 2. A principal components analysis separated sites into three main groups: rhithral streams, rhithral lake outlets, and kryal sites including outlets and streams. Rhithral streams contained the most diverse and taxon rich assemblages, being colonised by both non‐insect taxa and Ephemeroptera, Plecoptera, Trichoptera and Diptera. 3. Rhithral lake outlets supported high densities of non‐insect taxa such as Oligochaeta, Nemathelminthes and crustaceans. Despite low taxon richness, kryal sites had high Ephemeroptera and Plecoptera abundances. Chironomidae were most common at all sites. 4. Collector‐gatherers were dominant at all sites, whereas filter‐feeders were rare. Scrapers and shredders were more common in streams than lake outlets. 5. Water temperature and algal standing crops were higher at rhithral lake outlets than rhithral streams, perhaps providing more favourable habitat for non‐insect taxa. Glacial runoff was the dominant factor influencing macroinvertebrate assemblages of kryal streams and kryal lake outlets. Alpine lakes influenced the environmental conditions of their outlets and, consequently, their macroinvertebrate assemblages unless being constrained by a glacial influence.