Stream Invertebrate Communities Research Articles

The Value of Long-Term Stream Invertebrate Data Collected by Citizen Scientists.

The purpose of this investigation was to systematically examine the variability associated with temporally-oriented invertebrate data collected by citizen scientists and consider the value of such data for use in stream management. Variability in invertebrate data was estimated for three sources of variation: sampling, within-reach spatial and long-term temporal. Long-term temporal data were also evaluated using ordinations and an Index of Biotic Integrity (IBI). Through two separate investigations over an 11-year study period, participants collected more than 400 within-reach samples during 44 sampling events at three streams in the western United States. Within-reach invertebrate abundance coefficient of variation (CV) ranged from 0.44–0.50 with approximately 62% of the observed variation strictly due to sampling. Long-term temporal CV ranged from 0.31–0.36 with 27–30% of the observed variation in invertebrate abundance related to climate conditions (El Niño strength) and sampling year. Ordinations showed that citizen-generated assemblage data could reliably detect differences between study streams and seasons. IBI scores were significantly different between streams but not seasons. The findings of this study suggest that citizen data would likely detect a change in mean invertebrate density greater than 50% and would also be useful for monitoring changes in assemblage. The information presented here will help stream managers interpret and evaluate changes to the stream invertebrate community detected by citizen-based programs.

Negative effects of stagnation and drought on benthic invertebrate communities in lowland streams

Streams are extremely vulnerable to water abstraction across the world because of increasing water demand from humans, as well as because precipitation is decreasing in many areas. To determine how water abstraction affects water chemistry, hydromorphological variables and invertebrate assemblages, we conducted an experiment in which we mimicked two levels of disturbance: stagnation and drought. The experiment was performed at two lowland streams in Galicia (north-west Spain), which were similar in physical conditions but differed in trophic status (high v. low P). Samples were taken both before and after manipulation at the upstream control and downstream-disturbed stretches. There was a significant overall effect of water abstraction on both disturbed stretches, but invertebrate assemblages responded differently between streams and within stretches. In the low-P stream, invertebrate densities remained unchanged in the drought stretch but declined in the stagnation stretch relative to the control. At the same time, the high-P stream exhibited a strong loss of diversity in both the stagnation and drought stretches. These results suggest that short-term flow reductions driven by increasing water scarcity and abstraction put benthic communities in lowland streams at risk, and that risk would be greater (in terms of biodiversity loss) in streams that are initially impaired by high-P loading.

Individual and combined effects of fine sediment and glyphosate herbicide on invertebrate drift and insect emergence: a stream mesocosm experiment

Pesticides and deposited fine sediment have been associated independently with changes in relative abundance and number of sensitive species in aquatic ecosystems, but the interplay between these stressors in agricultural streams is poorly understood. We used a 28-d experiment in outdoor streamside mesocosms to examine the effects of varying levels of fine sediment and a glyphosate-based herbicide on 2 important aspects of macroinvertebrate community dynamics, invertebrate drift and adult insect emergence. We applied 4 levels of each stressor in a full factorial, repeated-measures design (4 glyphosate × 4 sediment levels × 2 replicates of each treatment combination). We focused on the propensities of the invertebrates to drift or emerge (number drifting per mesocosm/benthic individuals per m2). Sediment addition affected drift propensities of 4 of the 10 most common invertebrate taxa, community-level measures of drift (total taxon and Ephemeroptera, Plecoptera, Trichoptera [EPT] richness) and adult emergence (total propensity and taxon richness), whereas glyphosate addition affected drift propensity of only 1 taxon. These results suggest that glyphosate entering streams during terrestrial herbicide operations may be less problematic for aquatic invertebrate community dynamics than fine sediment from catchment erosion. No significant sediment × glyphosate interaction was detected for any individual taxon drift propensity or community-level drift or emergence measure, indicating that the 2 stressors acted additively, rather than synergistically or antagonistically. The dynamic measures (invertebrate drift and adult insect emergence propensities) often showed the opposite pattern compared to benthic invertebrate densities in the same experiment, a result highlighting the value of using dynamic aspects of stream invertebrate communities to identify mechanisms underlying stressor effects on benthic standing stocks.

Re-engineering buried urban streams: Daylighting results in rapid changes in stream invertebrate communities

Stream daylighting is a radical form of restoration which aims to improve morphological, chemical and ecological condition through the re-creation of an open channel from a buried or piped channel. Whilst empirical assessments of its efficacy are lacking, it is hypothesised that the substantial changes in habitat, channel form and energy supply arising from daylighting would lead to a significant changes in stream invertebrate communities, particularly where source populations of macroinvertebrates exist upstream. In this first published study of the ecological outcomes arising from a daylighting project, changes in the invertebrate community were assessed in two reaches of an urban stream catchment in Auckland, New Zealand's largest city, which were daylighted in early 2013. The two reaches allowed a paired assessment, where one of the reaches had a large area of intact native forest in its headwaters. Stream macroinvertebrates were sampled monthly pre- and post-daylighting to assess changes in stream macroinvertebrate communities.Community composition significantly changed pre- to post-daylighting (PERMANOVA Pseudo-F=2.0978, P=0.0018), where communities in different reaches changed by 58% and 71%, respectively. Taxonomic richness did not change with daylighting; however taxa replacements were apparent with 44 new taxa being collected in daylighted reaches and 11 taxa disappearing. Daylighting resulted in marked changes in energy resources and improved habitat in the short-term which altered invertebrate communities from biofilm feeding collector-browser communities to algal grazer communities. Although daylighting did not fully restore these streams from the effects of urbanisation, it is one practical option for the management of urban streams. Further, the presence of a local source population was an important determinant of stream community structure. Where source populations existed upstream community responses to daylighting were greater, including increased abundances of sensitive taxa.

Hydrology shapes taxonomic and functional structure of desert stream invertebrate communities

Hydrology is a fundamental factor influencing ecosystem dynamics, life-history strategies, and diversity patterns in running-water habitats. However, it remains unclear how hydrology may structure the taxonomic and functional composition of communities, especially in systems with high spatiotemporal variability in flow. We examined invertebrate diversity from 7 desert streams in the Huachuca Mountains of southeastern Arizona, USA, that span a flow permanence continuum from highly intermittent to perennial. We examined the relative roles of flow permanence, habitat size, season, and microhabitat in determining taxonomic and functional structure (according to 7 species traits compiled for 234 taxa) of these communities. We predicted that both functional and taxonomic diversity would be positively related to flow permanence and negatively related to the duration and number of stream drying events. As predicted, increased flow permanence was associated with increased functional richness, functional evenness, and taxonomic richness. Conversely, drying events reduced functional diversity across all measured indices. We found a saturating relationship between functional richness and taxonomic richness, indicating functional redundancy in species-rich communities, which may promote resilience of ecosystem function to environmental variation. Our study adds further evidence that hydrology is a key determinant of aquatic invertebrate diversity, and that stream hydroperiod strongly influences both functional and taxonomic diversity in arid-land streams.

Stream macroinvertebrate communities change with grassland afforestation in central Argentina

Lotic ecosystems are highly affected by land use changes such as afforestation of natural areas for management or commercial purposes. The aim of this study was to analyze the effect of pine plantations on benthic invertebrate communities in mountain grassland streams. Additionally, we assessed if the hydrological period modifies the effect of afforestation on stream invertebrates. Three headwater streams draining grasslands (reference streams) and three draining plantations of Pinus elliottii were selected in a mountain watershed of Córdoba province (Argentina). Hydrologic and physicochemical variables were registered and benthic invertebrate samples were collected in each stream at two different hydrological periods. Total invertebrate abundance, richness and diversity were reduced in afforested streams as well as the number of indicator taxa. In addition, invertebrate functional structure (i.e. taxonomic richness and total and relative abundance of functional feeding groups, FFG) showed differences between streams with different riparian vegetation and between hydrological periods. Total abundance of all FFGs was lower in afforested streams and scrapers’ relative abundance was higher in grassland streams at the low water period. In addition, in most FFGs richness was diminished in afforested streams. Changes in light intensity, hydrology and coarse organic matter inputs produced by afforestation alter fluvial habitats and consequently the composition and trophic structure of invertebrate communities in grassland streams of Córdoba mountains.

Community–environment relationships of riverine invertebrate communities in central Chinese streams

Chinese rivers are both highly biodiverse and highly under pressure, hence an urgent need exists to understand ecological drivers and disentangle different scales of stressors to support water management. Our aims were to (1) determine the most influential variables for benthic invertebrate occurrence, (2) compare results related to communities as opposed to metrics and (3) examine the role of spatial scales with relevance to management. Benthic invertebrate sampling was performed at 37 sites in selected tributaries of the middle reaches of the Yangtze, covering an environmental gradient with a focus on organic pollution (stratified sampling design). Ten metrics commonly used in biomonitoring were derived and analysed in parallel to assemblage data. Environmental variables covered 74 parameters from three different spatial scales, namely local, reach and catchment scale. We ran a CCA with each of the three subsets to find out the significant determining/explanatory variables, followed by pCCA and pRDA (for metric data) with these variables with forward selection to determine single variables important for each subset; we further used variation portioning for benthic invertebrate data. A high percentage of overall variability (70 %) of the assemblage structure was explained, with catchment- and local-scale variables being almost equally important. Small-scale variables tended to be more important than large-scale variables for the metric-based approach but not for the assemblage approach. Our results emphasise the need for spatially explicit regional studies in freshwater systems and suggest testing multi-metric assessment approaches to tackle water management and environmental health questions in China.

Meta‐community theory and stream restoration: evidence that spatial position constrains stream invertebrate communities in a mine impacted landscape

Mining activities, particularly acid mine drainage, often result in adverse effects on stream diversity and ecosystem functioning, and increased concern about these effects has generated a focus on restoration of mine‐impacted waterways. However, many stream restoration projects have not led to increased stream diversity and ecological recovery. One reason for this failure may be that restoration practitioners focus on local environmental conditions and fail to consider the importance of dispersal as a driver of stream invertebrate composition. To test this hypothesis, we used a meta‐community analysis to compare the influence of the local stream conditions with the regional supply of colonists. Invertebrate communities and physico‐chemical conditions were sampled in 37 streams across a mine‐impact gradient on the Stockton Plateau, West Coast of New Zealand's South Island. We found that pH, temperature, dissolved metals, and sediment significantly influenced invertebrate community composition. Furthermore, the spatial location of streams was a good predictor of stream diversity and invertebrate communities, independent of local environmental conditions. This result indicates an important role for regional dispersal barriers in determining stream invertebrate communities. Consequently, consideration of both the locations and strategic preservation of future colonist source streams and potential dispersal barriers during mine planning would enhance post‐mining restoration.

Diversification of stream invertebrate communities by large wood

Summary To evaluate the effects of large wood (LW) on benthic habitats and macroinvertebrates in sand‐bed lowland rivers, we compared invertebrate communities recorded on four pieces of LW (12 samples in total) and around them (60 samples) with those in four control sites in the same river (four samples). Mean flow velocity was 32% lower in the channel areas surrounding the LW than in control sites, while median sediment grain size was 50% higher, and the organic matter content of the riverbed sediments was 287% higher. At the same time, habitat conditions showed threefold to 1000‐fold increases in variance for five key abiotic habitat descriptors in the surrounding channel extending at least 60 cm upstream and 160 cm downstream of the LW. Three habitat patches typically occurred around the LW pieces: scouring pools, sand bars and accumulations of organic matter. These patches were colonised by distinctive invertebrate communities (e.g. accumulations of organic matter and gravel hosted 15 and 2 indicator taxa, respectively) that overall harboured 110% more taxa and exhibited a 168% higher diversity than control sites. The LW itself contributed only a small fraction to these increases, exhibiting a 15% increase in taxa richness and a 21% increase in species diversity compared to the control sites. The diversification of benthic invertebrate communities colonising streambed sediments around LW could be directly linked to the much more heterogeneous habitat conditions recorded there. Thus, local additions of large wood within river restoration programmes have the potential to promote the establishment of diverse invertebrate communities in extended areas of a river channel.

Habitat heterogeneity drives the geographical distribution of beta diversity: the case of New Zealand stream invertebrates.

To define whether the beta diversity of stream invertebrate communities in New Zealand exhibits geographical variation unexplained by variation in gamma diversity and, if so, what mechanisms (productivity, habitat heterogeneity, dispersal limitation, disturbance) best explain the observed broad-scale beta diversity patterns. We sampled 120 streams across eight regions (stream catchments), spanning a north–south gradient of 12° of latitude, and calculated beta diversity (with both species richness and abundance data) for each region. We explored through a null model if beta diversity deviates from the expectation of stochastic assembly processes and whether the magnitude of the deviation varies geographically. We then performed multimodel inference analysis on the key environmental drivers of beta diversity, using Akaike's information criterion and model and predictor weights to select the best model(s) explaining beta diversity. Beta diversity was, unexpectedly, highest in the South Island. The null model analysis revealed that beta diversity was greater than expected by chance in all eight regions, but the magnitude of beta deviation was higher in the South Island, suggesting differences in environmental filtering and/or dispersal limitation between North and South Island. Habitat heterogeneity was the predominant driver of beta diversity of stream macroinvertebrates, with productivity having a secondary, and negative, contribution. This is one of the first studies accounting for stochastic effects while examining the ecological drivers of beta diversity. Our results suggest that local environmental heterogeneity may be the strongest determinant of beta diversity of stream invertebrates, more so than regional- or landscape-scale variables.

Effects of repeated salt pulses on ecosystem structure and functions in a stream mesocosm

Rivers and streams affected by mining activities often receive short-term sharp salinity increases due to water-soluble stockpiled materials being washed into receiving water bodies. We conducted a mesocosm study to explore the response of structural (diatom and stream invertebrate communities) and functional descriptors (chlorophyll a concentration, fungal biomass and leaf decomposition) to repeated short salinity pulses (3h of duration, with nominal electrical conductivities of 5, 10 and 15mScm−1), mimicking the exposure pattern occurring at salt-mine affected rivers. The experiment was conducted in 12 artificial flow-through stream systems over 16days. The effect of the salt pulses on the ecosystem structure and functioning did not fully match most of our initial hypotheses, with the community response being weaker than predicted. The diatom community was, however, dominated by salt-tolerant species throughout the experiment, showing no consistent response to the treatment. The invertebrate response was associated with statistically significant changes in community structure (i.e. abundance of the different taxa) but no statistically significant changes in taxa richness. The salt pulses affected some functional descriptors of the ecosystem: fungal biomass exhibited a unimodal response to treatment magnitude, algal growth (i.e. chl a biomass) was hampered with increasing conductivity and leaf decomposition was significantly reduced in the high treatment.

A long-term study of the factors that influence compositional stability of stream invertebrates

Long-term studies have seldom considered the compositional stability (i.e., invariability of community composition) of stream invertebrate communities. Compositional stability could potentially be related to variations in species richness, habitat complexity, or hydrological and physicochemical conditions. Invertebrate species data were obtained for 21 sites that had been sampled over 16 to 20 years in Victoria, southern Australia. Stability of community composition at a site was measured with the mean Bray-Curtis coefficient, which was calculated for all comparisons between samples taken over the sampling period using only presence/absence data. Three datasets were compiled: one containing all species, one containing only insects, and one with family-level data. Multiple regressions demonstrated that stability at a site was related directly to species richness and habitat complexity and inversely to daily discharge; stability was not related to physicochemical conditions. The first 2 factors accounted for 45–49% of the variance while flow accounted for 9–16% but was not significant at the family level. The positive relation between stability and species richness may be due to higher variability in colonization at species-poor sites and thus lower compositional stability, while increased habitat complexity enhances stability by providing more refuges. Increased flow may result in more invertebrate drift and movement and thus lower stability, but the relationship was weak and provided little support to the idea that hydrology is an important ecological characteristic for invertebrates of southern Australian rivers.

Calcium concentration in leaf litter affects the abundance and survival of crustaceans in streams draining warm–temperate forests

Summary Stream ecosystems receive large quantities of nutrients from terrestrial ecosystems that influence community dynamics. However, few studies have investigated the effects of subsidiary calcium, an essential element of animals, on stream ecosystems. We focused on differences in calcium concentrations of leaf litter between tree species. In particular, litter of Japanese cedar (Cryptomeria japonica) has a higher concentration of calcium than other taxa, and the tree is planted in many parts of Japan. Therefore, we predicted that a C. japonica plantation would affect the supply of subsidiary calcium to stream ecosystems. We compared calcium concentration of leaf litters, soils, stream water and stream benthic invertebrates sampled at nine sites in catchments composed of cedar plantations, evergreen broad‐leaved forest and clear‐cut areas. In addition, we placed 10 Gammarus nipponensis in each of 10 nylon cages in the nine streams and after one month surveyed the number of surviving individuals. Calcium concentration in stream water and soil, and the density and survival of the dominant crustacean (Gammarus nipponensis) were significantly higher at sites dominated by C. japonica compared with other forest types. Furthermore, invertebrate community composition was correlated with total calcium and nitrate in stream water, indicating that terrestrial vegetation can affect stream invertebrate communities, particularly crustaceans.

A cross-continental comparison of stream invertebrate community assembly to assess convergence in forested headwater streams

We studied two forested, headwater streams to compare patterns of invertebrate community structure and consequences for ecosystem functioning in two temperate locations, Galicia (NW Spain) and Vancouver (SW Canada). The two sites were selected due to the similar dominance of congeneric invertebrate species, as well as similarity in their hydromorphological and physico-chemical characteristics. Field experiments tested for similarities and dissimilarities in the invertebrate community assembly in leaf packs in streams. Our results indicated that alder leaves always decomposed faster than eucalyptus leaves, from threefold higher in Galicia to tenfold in Vancouver. At the species level, the biogeographic factor was the main source of variation on invertebrate assemblages (84.9 %), but this percentage quickly decreased at higher levels of taxonomic resolution, i.e. family. Moreover, there was a strong leaf species influence in both sites. There were more invertebrates colonizing leaves (per unit mass) in Vancouver than in Galicia (fourfold on average), though alder leaves seemed to be always the preferred resource (5.5-fold higher density on average). Regardless, a similar trophic structure was found between sites and leaf species. Brillia spp. and Corynoneura spp., a shredder and a collector-gatherer, respectively, seemed to be the most important species and showed similar colonization patterns in both sites with potential to strongly influence the leaf processing and nutrient cycling in these ecosystems. Even though our results are limited to the similarity found between only two sites, results from other studies, where the same species have been found coexisting during leaf pack processing, reinforces our results that common rules and mechanisms determine patterns of key ecological processes on a biogeographical scale.

Stress as a modifier of biodiversity effects on ecosystem processes?

Does stress, defined as a reduction in growth by external constraints, modify biodiversity effects on ecosystem functioning? That is, are diversity effects stronger under stressful, as opposed to favourable conditions? The study by Fugère et al. (2012) in this issue borrows the stress-gradient hypothesis from plant ecology to explore this issue in an aquatic detritus-detritivore system. Although they find weak support for their hypothesis, the study opens the door for future experimental and theoretical investigations into the role of stress in modifying the relationship between the diversity of animal communities and ecosystem processes.

Acid Mine Drainage Index (AMDI): a benthic invertebrate biotic index for assessing coal mining impacts in New Zealand streams

Acid mine drainage (AMD) is a widespread phenomenon globally. Drainage into streams from coal mines often contains a cocktail of acidic waters high in dissolved metals, and consequently stream invertebrate communities may be severely impacted. Traditionally, the intensity of impacts has been assessed by combinations of water chemistry and benthic invertebrate metrics; however, a metric specifically designed for assessing mining impacts has not been developed. We propose a benthic invertebrate biotic index: the Acid Mine Drainage Index (AMDI), based on species presence data. The AMDI has been developed by associating water chemistry and benthic invertebrate community data collected from 91 sites. AMD indicator scores for 57 taxa were calculated using weighted averaging. Site scores can range from 0 (severely impacted) to 100 (unimpacted) and sites can be categorised as ‘severely impacted’, ‘impacted’ or ‘unimpacted’. Comparisons between AMDI and traditional indices indicated the AMDI is more accurate at detecting mine drainage.

Anadromous alewives in linked lake–stream ecosystems: do trophic interactions in lakes influence stream invertebrate communities?

Trophic interactions can influence the flux of energy and nutrients between donor and recipient ecosystems, thereby altering recipient food webs and communities. We investigated the potential for anadromous alewife to influence filter-feeding insects in lake outflow streams by altering seston and zooplankton export from lakes to streams through size-selective consumption of zooplankton in lakes. We compared spring and summer zooplankton biomass and body size and seston concentration in 6 lakes and their respective outflow streams (3 with alewife access, 3 without alewife access) in Maine, USA. The contribution of seston particles ≥500-µm and mean pelagic zooplankton size decreased from spring to summer in alewife lakes, but not in lakes without alewife. However, we found no seasonal change in zooplankton body size and seston ≥500-µm in the outflow streams of alewife lakes. Furthermore, zooplankton biomass and seston concentration differed between lakes and streams, a result indicating the influence of additional factors on seston movement from lakes to streams. Last, we found no relationship between filter-feeder biomass or community structure and seston quantity, a result indicating that stream communities probably were not strongly regulated by seston availability. Our results illustrate that strong trophic interactions may not be propagated from lakes to streams and suggest the importance of boundaries in modulating the extent to which trophic interactions in one ecosystem can influence the flow of energy to adjacent ecosystems.

Temporal and spatial variability of invertebrate communities in potential reference headwater streams of the Georgia Piedmont

Standard bioassessment protocols compare macroinvertebrate communities in potentially impacted streams to communities in reference streams. However, in many landscapes ‘pristine’ reference streams may not exist and researchers may be forced to use the best available alternatives. The objective of this study was to evaluate macroinvertebrate communities in potential reference streams in the highly impacted Piedmont physiographic region of Georgia. We determined the influence of season, substrate, and reach-scale habitat type on macroinvertebrate assemblages in five forested, headwater streams that were minimally disturbed by current anthropogenic activities. The five streams represented three different reach-scale substrate compositions (gravel, sand, and bedrock). We predicted that macroinvertebrate communities in these streams would be influenced by season and by substrate composition. Streams were sampled in May, August, and November 2003, using a corer to sample riffles and a Hess sampler to sample runs and pools. Four of the five streams studied exhibited distinct seasonal variation, which exceeded spatial variation among those streams. Invertebrate community compositions among streams were not consistently predicted by reach-scale substrate in our study. The communities in the two sand streams were unique but generally dissimilar to each other. The two gravel streams supported similar communities across seasons. Riffle and wood habitats supported distinct invertebrate communities that were dissimilar to the run and pool habitats. Our data indicated that potential reference streams can vary widely in invertebrate community compositions and we cannot always predict that variability simply by substrate alone. Thus, selecting reference streams for bioassessment projects in the Georgia Piedmont may be complex.

Response of stream invertebrates to short-term salinization: A mesocosm approach

Salinization is a major and growing threat to freshwater ecosystems, yet its effects on aquatic invertebrates have been poorly described at a community-level. Here we use a controlled experimental setting to evaluate short-term stream community responses to salinization, under conditions designed to replicate the duration (72 h) and intensity (up to 5 mS cm−1) of salinity pulses common to Mediterranean rivers subjected to mining pollution during runoff events. There was a significant overall effect, but differences between individual treatments and the control were only significant for the highest salinity treatment. The community response to salinization was characterized by a decline in total invertebrate density, taxon richness and diversity, an increase in invertebrate drift and loss of the most sensitive taxa. The findings indicate that short-term salinity increases have a significant impact on the stream invertebrate community, but concentrations of 5 mS cm−1 are needed to produce a significant ecological response.

Trophic Interactions Between Insects and Stream-Associated Amphibians in Steep, Cobble-Bottom Streams of the Pacific Coast of North America

Two native, stream-associated amphibians are found in coastal streams of the west coast of North America, the tailed frog and the coastal giant salamander, and each interacts with stream insects in contrasting ways. For tailed frogs, their tadpoles are the primary life stage found in steep streams and they consume biofilm from rock surfaces, which can have trophic and non-trophic effects on stream insects. By virtue of their size the tadpoles are relatively insensitive to stream insect larvae, and tadpoles are capable of depleting biofilm levels directly (exploitative competition), and may also “bulldoze” insect larvae from the surfaces of stones (interference competition). Coastal giant salamander larvae, and sometimes adults, are found in small streams where they prey primarily on stream insects, as well as other small prey. This predator-prey interaction with stream insects does not appear to result in differences in the stream invertebrate community between streams with and without salamander larvae. These two examples illustrate the potential for trophic and non-trophic interactions between stream-associated amphibians and stream insects, and also highlights the need for further research in these systems.