Diversity Of Macroinvertebrate Communities Research Articles

Characteristics of Spatiotemporal Patterns in Benthic Macroinvertebrate Communities in Two Adjacent Headwater Streams.

Headwater streams provide various microhabitats, resulting in high diversity of macroinvertebrate community. In this study, we compared the differences of communities between two adjacent headwater streams (Jangjeon stream (GRJ; GRJ1-GRJ5) and Haanmi stream (GRH; GRH1-GRH3)) in Jungwang and Gariwang...

Basin risk explains patterns of macroinvertebrate community differences across small streams in the Fayetteville Shale, AR

Understanding the relationship between natural landscape characteristics and human activities is crucial to predicting conditions under which loss of freshwater biodiversity occurs. For example, region-specific human activities, like unconventional natural gas (UNG) development, are often absent from models because of their limited spatial extent, yet their effects may alter stream ecosystems. Unconventional natural gas development is an expanding human activity that requires land-clearing, water withdrawal, and chemicals for hydraulic fracturing that could alter stream habitat and water quality, yet the degree of alteration may depend on basin natural landscape characteristics. We modified a basin-specific multi-metric risk model and used it to predict differences in macroinvertebrate communities in small stream basins (range 5.71–90.96 km2) in the Fayetteville Shale, Arkansas. We modeled basin risk as the interaction between basin natural sensitivity to alterations and basin exposure to human activities. We predicted that macroinvertebrate communities in 18 basins exposed to a gradient of unconventional natural gas (UNG) in a pasture-dominated landscape would experience greater differences in macroinvertebrate metrics across a risk gradient than 22 basins with a similar gradient of pasture land. Macroinvertebrate metrics of diversity declined by as much as 88% across the basin risk gradient. In contrast, macroinvertebrate metrics of biomass and density increased by 28% across the same basin risk gradient. Basin risk explained more variation in macroinvertebrate communities than sensitivity or exposure alone, suggesting an interaction between basin natural landscape characteristics and human activities. In contrast to our prediction, all macroinvertebrate metrics responded similarly in basins with and without UNG, which suggests either there was no added stressor-effect of UNG or UNG alterations resulted in the same biological effects as pasture. However, macroinvertebrate metrics in basins with and without UNG responded differently across a sediment-specific risk model where dams were modeled as sediment traps instead of structures that alter flow and temperature. As land alterations continue in the Fayetteville Shale, our basin-specific risk model can be used as a tool to identify at-risk stream communities.

Diversity of macroinvertebrates positively correlates with diversity of macrophytes in karst ponds

Relations between diversity of macrophytes and macroinvertebrates in 16 karst ponds on the outskirts of SE Alps (Slovenia) were investigated. Inventory of macrophytes was performed and their cover values were estimated. Macroinvertebrates were sampled with hand net. Correlations between environmental factors and parameters of taxonomic richness and diversity of the communities were calculated. Influences of environmental parameters on the structure of communities were analyzed. Results confirmed significant positive correlations between diversity of macrophytes and macroinvertebrates. The most abundant and most species-rich group of plants were emergent macrophytes. Richness and diversity of macrophytes were more important than their coverage for diversity of macroinvertebrates. A negative direct influence of the cattle to macrophytes as well as to macroinvertebrates was calculated. We can conclude that diversity of macrophytes had a positive influence on diversity of macroinvertebrate community. High diversity of emergent macrophytes supports high diversity of macroinvertebrate communities – directly as higher number of hiding places, oviposition sites or food sources and indirectly with more efficient uptake of excessive nutrients. Despite the negative direct influence of the cattle to macrophytes that we calculated, trampling positively influences macrophytes and indirectly also macroinvertebrates in karst ponds, since it enables the existence of these specific waterbodies in the long run.

Urbanization reduces and homogenizes trait diversity in stream macroinvertebrate communities.

More than one-half of the world's population lives in urban areas, so quantifying the effects of urbanization on ecological communities is important for understanding whether anthropogenic stressors homogenize communities across environmental and climatic gradients. We examined the relationship of impervious surface coverage (a marker of urbanization) and the structure of stream macroinvertebrate communities across the state of Maryland and within each of Maryland's three ecoregions: Coastal Plain, Piedmont, and Appalachian, which differ in stream geomorphology and community composition. We considered three levels of trait organization: individual traits, unique combinations of traits, and community metrics (functional richness, functional evenness, and functional divergence) and three levels of impervious surface coverage (low [<2.5%], medium [2.5% to 10%], and high [>10%]). The prevalence of an individual trait differed very little between low impervious surface and high impervious surface sites. The arrangement of trait combinations in community trait space for each ecoregion differed when impervious surface coverage was low, but the arrangement became more similar among ecoregions as impervious surface coverage increased. Furthermore, trait combinations that occurred only at low or medium impervious surface coverage were clustered in a subset of the community trait space, indicating that impervious surface affected the presence of only a subset of trait combinations. Functional richness declined with increasing impervious surface, providing evidence for environmental filtering. Community metrics that include abundance were also sensitive to increasing impervious surface coverage: functional divergence decreased while functional evenness increased. These changes demonstrate that increasing impervious surface coverage homogenizes the trait diversity of macroinvertebrate communities in streams, despite differences in initial community composition and stream geomorphology among ecoregions. Community metrics were also more sensitive to changes in the abundance rather than the gain or loss of trait combinations, showing the potential for trait-based approaches to serve as early warning indicators of environmental stress for monitoring and biological assessment programs.

Local environment rather than past climate determines community composition of mountain stream macroinvertebrates across Europe.

Community assembly is determined by a combination of historical events and contemporary processes that are difficult to disentangle, but eco-evolutionary mechanisms may be uncovered by the joint analysis of species and genetic diversity across multiple sites. Mountain streams across Europe harbour highly diverse macroinvertebrate communities whose composition and turnover (replacement of taxa) among sites and regions remain poorly known. We studied whole-community biodiversity within and among six mountain regions along a latitudinal transect from Morocco to Scandinavia at three levels of taxonomic hierarchy: genus, species and haplotypes. Using DNA barcoding of four insect families (>3100 individuals, 118 species) across 62 streams, we found that measures of local and regional diversity and intraregional turnover generally declined slightly towards northern latitudes. However, at all hierarchical levels we found complete (haplotype) or high (species, genus) turnover among regions (and even among sites within regions), which counters the expectations of Pleistocene postglacial northward expansion from southern refugia. Species distributions were mostly correlated with environmental conditions, suggesting a strong role of lineage- or species-specific traits in determining local and latitudinal community composition, lineage diversification and phylogenetic community structure (e.g., loss of Coleoptera, but not Ephemeroptera, at northern sites). High intraspecific genetic structure within regions, even in northernmost sites, reflects species-specific dispersal and demographic histories and indicates postglacial migration from geographically scattered refugia, rather than from only southern areas. Overall, patterns were not strongly concordant across hierarchical levels, but consistent with the overriding influence of environmental factors determining community composition at the species and genus levels.

Temporal variations in macroinvertebrate communities from the tributaries in the Three Gorges Reservoir Catchment, China

BackgroundThe seasonal variations in macroinvertebrate communities in tropical, temperate and subarctic regions have been observed and well documented to date, but similar studies conducted in subtropical rivers at the regional scale are relatively rare. In this paper, the macroinvertebrate communities from the main tributaries in the Three Gorges Reservoir Catchment (TGRC) were investigated as a function of the four seasons to explore the temporal variations in macroinvertebrate communities and further tests the temporal stability of certain metrics that are based on macroinvertebrates under a routine bioassessment framework.ResultsThe taxa richness reached the highest point in spring, followed by winter, autumn and summer. The taxa Chironomidae, Heptageniidae, Corbiculidae and Baetidae dominated the communities across seasons. The temporal variations in communities were mainly reflected in the changes in taxa proportions between seasons. The percentages of the taxa Heptageniidae and Baetidae were the highest in autumn (normal discharge period) and lowest in summer (high discharge period). The abundance of macroinvertebrates was the lowest in summer, increased in autumn and winter, and then decreased in spring. Natural fluctuations of aquatic ecosystems (temporal effects) resulted in variations that were apparent in macroinvertebrate-based metrics, such as EPT%, Baetidae%, Caenidae%, Ephemerellidae% and Hydropsychidae%.ConclusionsThe results of our study demonstrated that the macroinvertebrate communities in the main tributaries of the TGRC varied as a function of seasons. This variation was fundamentally similar to the seasonal patterns in subarctic and temperate streams. Different hydro-morphological characteristics and water quality during the high discharge period (summer), low discharge period (winter) and normal discharge period (spring and autumn) strongly affected the distribution patterns of macroinvertebrate communities. Discharge variation among seasons resulted in seasonal fluctuations in the density of macroinvertebrates. In the TGRC, autumn was the important hatching period for mayflies (Ephemeroptera). The variations in metrics related to macroinvertebrates indicated that temporal effects should not be neglected under a biomonitoring framework in future studies.

Assessing the suitability of genetic diversity of Chironomus riparius (Meigen) as an indicator of environmental pollution

Reliable and cost-effective indicators are needed to reduce uncertainty in ecological risk assessments of chemicals so that their long-term and evolutionary impacts in the dynamics of stressed biological communities can be accounted for.In the present study we investigate the suitability of genetic diversity as an indicator of ecological disturbance of freshwater ecosystems. For that, we selected three freshwater systems with well-known histories of metal contamination and three nearby reference sites located in Northern Portugal and the effects of metal contamination were assessed both in the levels of genetic diversity of the non-biting midge Chironomus riparius Meigen (at microsatellite markers) and in the diversity and composition of the benthic macroinvertebrate communities.Results showed a remarkable impoverishment in the abundance and diversity of macroinvertebrate communities of metal polluted sites in which most sensitive taxa were eliminated and replaced by more opportunistic ones belonging mainly to Oligochaeta and Diptera. In contrast, no evidence for pollution-induced genetic erosion was found in C. riparius populations in the studied area, with genetic diversity of the species being indeed higher in sites with impoverished macroinvertebrate communities and poor habitat quality.Our findings suggest that there are important limitations to the use of measures of genetic diversity of C. riparius per se to unravel ecological disturbance. Field studies aiming at quantifying pollutant-driven genetic erosion need to carefully consider the ecological and demographic aspects of potential target species.

Influence of discharge patterns on temporal variation of macroinvertebrate communities in forested and deforested streams in a tropical agricultural landscape

Deforestation of riparian forests can directly influence stream macroinvertebrate communities, through changes in resource availability, habitat quality, and hydrological alterations. Here we evaluated whether mean discharge and discharge coefficient of variation (CV), estimated over a 15-month study, influenced forested and deforested stream macroinvertebrate communities. Higher diversity and mean discharge were recorded in deforested streams, and community composition was strongly related to mean discharge. Streams formed a gradient of both mean discharges and discharge CV, which both influenced patterns of diversity. Discharge CV negatively influenced diversity in a nonlinear model, whereas both mean discharge and discharge CV influenced differentiation of macroinvertebrate communities among five sampling occasions. Similarity among sampling times within each stream estimated by the Morisita–Horn index decreased with increasing mean discharge, whereas response to CV was quadratic, with higher similarity at intermediate values and lower similarity at more extreme values. These results suggest that stability of stream macroinvertebrate communities display different responses to mean discharge and discharge CV, and that hydrological alterations can interact with land use changes to determine community dynamics at local scales.

Macroinvertebrate communities associated with duckweed (Lemnaceae) in two Eastern Cape rivers, South Africa

The functional feeding groups and diversity of macroinvertebrate communities associated with duckweed mats in the New Years River (two sites) and Bloukrans River (two sites), Eastern Cape province, South Africa, were assessed. Duckweed (Lemnaceae) is a ubiquitous family of floating macrophytes. A total of 41 macroinvertebrate families were collected monthly over a six-month period from February to July 2014. Duckweed biomass in both rivers was highly variable both temporally and spatially. The majority of identified macroinvertebrate taxa were predators and detritivores, with a small percentage of herbivores. An average of approximately 26% of the macroinvertebrate taxa found were from families that include species from more than one functional feeding group. Although overall measures of diversity and ecosystem health (Fisher’s α and Simpson’s index) remained constant over time in the New Years River, significant differences in macroinvertebrate community structure were seen between sites and months on both rivers, with dissimilarity being driven by a larger number of species in the New Years River. This high variability within macroinvertebrate assemblages probably reflects a combination of heterogeneous duckweed distribution, variation in physico-chemistry, opportunistic behaviours of macroinvertebrate predators and/or successional colonisation of duckweed mats.

Characterization of Macroinvertebrate Communities in the Hyporheic Zone of River Ecosystems Reflects the Pump-Sampling Technique Used.

The hyporheic zone of river ecosystems provides a habitat for a diverse macroinvertebrate community that makes a vital contribution to ecosystem functioning and biodiversity. However, effective methods for sampling this community have proved difficult to establish, due to the inaccessibility of subsurface sediments. The aim of this study was to compare the two most common semi-quantitative macroinvertebrate pump-sampling techniques: Bou-Rouch and vacuum-pump sampling. We used both techniques to collect replicate samples in three contrasting temperate-zone streams, in each of two biogeographical regions (Atlantic region, central England, UK; Continental region, southeast France). Results were typically consistent across streams in both regions: Bou-Rouch samples provided significantly higher estimates of taxa richness, macroinvertebrate abundance, and the abundance of all UK and eight of 10 French common taxa. Seven and nine taxa which were rare in Bou-Rouch samples were absent from vacuum-pump samples in the UK and France, respectively; no taxon was repeatedly sampled exclusively by the vacuum pump. Rarefaction curves (rescaled to the number of incidences) and non-parametric richness estimators indicated no significant difference in richness between techniques, highlighting the capture of more individuals as crucial to Bou-Rouch sampling performance. Compared to assemblages in replicate vacuum-pump samples, multivariate analyses indicated greater distinction among Bou-Rouch assemblages from different streams, as well as significantly greater consistency in assemblage composition among replicate Bou-Rouch samples collected in one stream. We recommend Bou-Rouch sampling for most study types, including rapid biomonitoring surveys and studies requiring acquisition of comprehensive taxon lists that include rare taxa. Despite collecting fewer macroinvertebrates, vacuum-pump sampling remains an important option for inexpensive and rapid sample collection.

An inter-catchment assessment of macroinvertebrate communities across groundwater-fed streams within Denali National Park, interior Alaska

Groundwater-fed streams are typically hotspots of aquatic biodiversity within glacierized catchments. Surface water physicochemistry and macroinvertebrate communities within five groundwater-fed streams were characterised across catchments in Denali National Park, interior Alaska. The main aim of this study was to assess whether hydrological controls on macroinvertebrate communities (e.g. flow permanence) identified within previous catchment-specific studies are present at wider spatial scales, across multiple groundwater-fed streams located on alluvial terraces within glacierized catchments. Macroinvertebrate community diversity, in general, was shown to be high and relatively invariant across the groundwater-fed streams assessed. Flow permanence was shown to be responsible for the greatest differences in macroinvertebrate communities. Although ephemeral and perennial streams exhibited no differences in diversity, perennial streams maintained higher total abundance and taxonomic richness of macroinvertebrates than ephemeral streams. Furthermore, macroinvertebrate community structure was also shown to be different, with ephemeral streams composed of a smaller number of specialised taxa able to withstand disturbance from periodic dewatering. Relationships between physicochemical variables and macroinvertebrate diversity, however were not observed across the catchments. The high diversity and structural heterogeneity of macroinvertebrate communities observed across alluvial terrace streams indicated the importance of these systems as biodiversity hotspots in regions under threat from climate change.

Associations Between Macroinvertebrates and Paralemanea mexicana, an Endemic Freshwater Red Alga from a Mountain River in Central Mexico.

Macrophytes are common inhabitants of lotic environments and, depending on their morphological traits, possess adaptations that provide shelter to aquatic invertebrates against strong river flow and predators. They may also be used as a food source by macroinvertebrates. The main goal of this study was to determine the relationship between the red alga Paralemanea mexicana and its role as a shelter and/or food source for lotic macroinvertebrates. We also conducted research on the role of microhabitat and morphological variations of the alga in determining macroinvertebrate taxon abundance, diversity, and functional group composition in a high-current velocity river. Results showed that changes in cover and morphology of P. mexicana were mostly correlated with river current velocity, irradiance, and seasonal variation. In turn, these were related to changes in abundance and diversity of the associated macroinvertebrate community. In addition, six macroinvertebrate functional feeding groups were evaluated for associations with the red alga: filtering and gathering collectors, piercers, scrapers, herbivore shredders, and predators. The results showed that the Trichoptera Hydroptilidae genera Ochrotrichia and Metrichia use P. mexicana as a food source and case-building material. The Trichoptera Glossosomatidae Mortoniella uses the alga as a substrate. The biotic interactions between P. mexicana and associated macroinvertebrates reveal the importance of macrophytes as purveyors of substrate, as food and shelter for macroinvertebrates, and also as promoters of macroinvertebrate community diversity. In addition, it was shown that macroinvertebrate herbivory likely facilitates vegetative propagation of the red alga through increased release and germination of carpospores and new gametophytes.

Aquatic macroinvertebrate biodiversity associated with artificial agricultural drainage ditches

Agricultural drainage ditches are ubiquitous features in lowland agricultural landscapes, built primarily to facilitate land drainage, irrigate agricultural crops and alleviate flood risk. Most drainage ditches are considered artificial waterbodies and are not typically included in routine monitoring programmes, and as a result the faunal and floral communities they support are poorly quantified. This paper characterises the aquatic macroinvertebrate diversity (alpha, beta and gamma) of agricultural drainage ditches managed by an internal drainage board in Lincolnshire, UK. The drainage ditches support very diverse macroinvertebrate communities at both the site (alpha diversity) and landscape scale (gamma diversity) with the main arterial drainage ditches supporting greater numbers of taxa when compared to smaller side ditches. Examination of the between site community heterogeneity (beta diversity) indicated that differences among ditches were high spatially and temporally. The results illustrate that both main arterial and side ditches make a unique contribution to aquatic biodiversity of the agricultural landscape. Given the need to maintain drainage ditches to support agriculture and flood defence measures, we advocate the application of principles from ‘reconciliation ecology’ to inform the future management and conservation of drainage ditches.

Intermittent pool beds are permanent cyclic habitats with distinct wet, moist and dry phases.

Recognition that intermittent pools are a single habitat phase of an intermittent pool bed that cycles between aquatic and terrestrial habitat greatly enhances their usefulness for addressing general questions in ecology. The aquatic phase has served as a model system in many ecological studies, because it has distinct habitat boundaries in space and time and is an excellent experimental system, but the aquatic to terrestrial transition and terrestrial phase remain largely unstudied. We conducted a field experiment within six replicate natural intermittent pool beds to explore macroinvertebrate community dynamics during the transition from aquatic to terrestrial habitat and during the terrestrial phase. We monitored and compared macroinvertebrate communities within leaf packs that i) remained wet, ii) underwent drying (i.e., started wet and then dried), and iii) remained dry. Our results show that i) a diverse macroinvertebrate community inhabits all phases of intermittent pool beds, ii) pool drying involves colonization by an assemblage of macroinvertebrates not recorded in permanently terrestrial leaf packs, iii) the community within dried leaf packs remains distinct from that of permanently terrestrial leaf packs for an extended period following drying (possibly until subsequent refilling), and iv) there are likely to be strong spatial and temporal resource linkages between the aquatic and terrestrial communities. The unique environmental characteristics of intermittent pool beds, which repeatedly cycle from aquatic to terrestrial habitat, should continue to make them valuable study systems.

Longitudinal variation of macroinvertebrate communities in a Mediterranean river subjected to multiple anthropogenic stressors

ABSTRACTRiver impoundments and waste water discharge are a serious threat to the integrity and biodiversity of river ecosystems, especially in central Italy. Benthic macroinvertebrates were sampled in autumn and summer along the Aniene River to assess the cumulative biological effect of the numerous dams and sewage treatment plants that affect its middle and lower course. We hypothesized that (i) increasing habitat impairment would promote the formation of nestedness in species assemblage, where species poor locations support only a sub‐set of organisms from richer sites; (ii) specific life‐history traits would confer sensitivity to habitat degradation. Patterns of macroinvertebrate richness and diversity along the river tracked the distribution of dams and sewage treatment plants. Partial Mantel test showed that dissimilarity in assemblages increased with the number of dams and treatment plants between reaches after controlling for longitudinal distance. Assemblages were significantly nested, and nestedness appeared related to both water quality gradients (phosphorous, turbidity) that reflected anthropogenic inputs, and to natural gradient in altitude. Reaches with nested assemblages (supporting a sub‐set of the species pool) were characterized by greater representations of taxa with shorter life cycles, while, in contrast, species rich sites supported taxa with longer life cycles and lower dispersal ability. These results suggest that the cumulative effect of dams and sewage treatment plants promoted the formation of nested subsets in species distribution. Moreover, it appeared that certain functional traits that conferred sensitivity also dictated the progressive non‐random loss of taxa in face of multiple anthropogenic stressors. These findings have conservation implications in the regions, but need to be considered preliminary since anthropogenic and natural factors co‐varied systematically along the study river precluding the identification of single factor effects.

Environmental drivers - spatial and temporal variation of macroinvertebrate communities in island streams: the case of the Azores Archipelago

Environmental drivers - spatial and temporal variation of macroinvertebrate communities in island streams: the case of the Azores Archipelago

Drivers of beta diversity of macroinvertebrate communities in tropical forest streams

Summary1. There has recently been increasing interest in patterns of beta diversity but we still lack a comprehensive understanding of these patterns in various regions (e.g. the tropics), ecosystems (e.g. streams) and organism groups (e.g. invertebrates).2. Our aim was to investigate the patterns of beta diversity of stream macroinvertebrates in relation to key environmental (i.e. stream size, pH and habitat degradation) and geographical variables (i.e. latitude, longitude, altitude) in a tropical region. We surveyed a total of 8–10 riffle sites in each of 34 streams (altogether 337 riffle sites were sampled) in Peninsular Malaysia to examine variation in macroinvertebrate community composition at within‐stream and among‐stream scales.3. Based on test of homogeneity of dispersion, we found that the streams studied differed significantly in within‐stream variation in community composition (i.e. among‐site variation of within stream beta diversity). The patterns were similar based on Bray–Curtis coefficient on abundance data, Sorensen coefficient on presence–absence data and Simpson coefficient on presence–absence data. We also found that within‐stream beta diversity was significantly related to stream size, pH and latitude, with each of these variables individually accounting for around 20% of the variation in beta diversity in simple regressions, while the total variation explained by the three significant variables amounted to around 50% in multiple regressions. By contrast, habitat degradation, longitude and altitude were not significantly related to beta diversity. We also found that the factor drainage basin accounted for much of the variation in beta diversity in general linear models, suppressing the effects of environmental variables.4. We concluded that within‐stream beta diversity is mainly related to a combination of the identity of a drainage basin and stream environmental factors. Our findings provide important background for stream environmental assessment and conservation planning by emphasising that (i) macroinvertebrate communities within streams are not homogeneous, but show considerable beta diversity, (ii) streams differ in their degree of within‐stream beta diversity, (iii) stream size and water pH should be considered in applied contexts related to within‐stream beta diversity and (iv) historical effects may be different in different drainage basins and may affect present‐day patterns of within‐stream beta diversity.

Is Catchment Imperviousness a Keystone Factor Degrading Urban Waterways? A Case Study from a Partly Urbanised Catchment (Georges River, South-Eastern Australia)

The extent of catchment impervious surface is recognised to be an important factor associated with the condition of urban freshwater streams. We tested the hypothesis that the degree of catchment imperviousness predicted the relative ecological condition of freshwater reaches within the network of streams and rivers in the partly urbanised Georges River catchment in temperate south-eastern Australia. The 2-year study involved two spring and two autumn assessments of water quality (chemical and physical) and ecological condition, using benthic macroinvertebrates, riparian vegetation and calculation of catchment imperviousness. The study revealed that highly urbanised streams had strongly degraded water quality and macroinvertebrate communities, compared to clean non-urban reference streams. We found three clear groups of sites with varying degrees of ecological condition, being categorised according to the level of catchment effective imperviousness (low 18.0 %). Water pollution also varied according to these categories. A combination of two water chemistry attributes (total nitrogen and calcium), along with catchment imperviousness and riparian vegetation condition, were identified as being the factors most strongly associated with variation of macroinvertebrate communities. Based on our results, we recommend that protection of the ecological condition of streams should focus on not only water quality but also include catchment imperviousness and riparian vegetation condition.

Temporal variability in taxonomic completeness of stream macroinvertebrate assemblages

Natural temporal variation in biological assemblages is generally acknowledged, but rarely controlled for in existing bioassessment approaches. Many bioassessment methods ignore the variation of assemblage structure through time and, thus, lack a process to evaluate the effects of natural temporal variation on their outcomes. We used an 11-y data set from 24 near-pristine reference streams (validation sites) and a 5-y data set from 10 streams exposed to human disturbance (test sites) in northern Finland to examine: 1) the amount of interannual variation in macroinvertebrate communities in both types of streams measured as variation in taxonomic completeness (i.e., ratio of observed/expected taxa; O/E ratio), and 2) how temporal variability affects bioassessment outcomes. Most of the variation in O/E values was explained by stream type (validation or test). Interannual variation in O/E was low at both validation and test sites, a result supporting the assumption of high constancy of biological assemblages through time. Temporal variation in O/E at validation sites was related to climatic factors (regional precipitation) and to some local environmental variables, e.g., substratum heterogeneity. Communities in validation and test sites responded differentially to climatic variation. The low interannual variation in O/E suggests that 1-y data from reference sites can be extrapolated across years relatively safely, but climatically extreme years may be problematic. Temporal variability in O/E was low at both types of sites, but it was still high enough to result in variable ecological status assessments across years, mainly at test sites with lower O/E ratios. Thus, at test sites, use of only 1-y data may cause erroneous management decisions, and accurate assessment of the biological quality of test sites might require repeated sampling over several years.

Macroinvertebrate Community Composition of Temporary Prairie Wetlands: A Preliminary Test of the Effect of Rotational Grazing

Over half the temporary wetlands in the prairie pothole region of North America (PPR) have been drained for agricultural purposes and nearly all those remaining have agriculturally impacted margins. Cattle grazing is a common practice in the PPR. Rotational grazing utilizes several pastures, with cattle grazing one pasture while the others are rested. The success of this practice in increasing the suitability of rested wetlands for macroinvertebrates has not been evaluated for temporary wetlands. We repeatedly sampled macroinvertebrate communities in 13 rotationally grazed temporary wetlands. Seven wetlands were in an early grazed pasture (i.e., grazed when wetlands were wet), and six wetlands were in an adjacent late grazed pasture (i.e., grazed when wetlands were dry). The communities were examined from two perspectives, traditional taxonomy and an emerging functional traits perspective. Late grazed wetlands contained more abundant and diverse macroinvertebrate communities than early grazed wetlands. Chironomidae were significantly more abundant in late grazed wetlands. Scrapers were more common in the early grazed wetlands, whereas late grazed wetlands contained more gatherers. Our results suggest that rotational grazing may have a positive influence on macroinvertebrate diversity by allowing some wetlands to escape grazing pressure during the wet season.