Macroinvertebrate community response to natural and forest harvest gradients in western Oregon headwater streams

1. To examine the effects of forest harvest practices on headwater stream macroinvertebrates, we compiled a 167 site database with macroinvertebrate, fish, physical habitat and catchment land cover data from the three forested ecoregions in western Oregon. For our analysis, headwater streams were defined by catchment areas <10 km² and perennial water during summer low flows. Almost all sites in the database were selected using a randomised survey design, constituting a representative sample of headwater streams in these ecoregions. 2. Macroinvertebrate taxonomic and functional feeding group composition were very similar among the three ecoregions in the study area (Coast Range, Cascades and Klamath Mountains). On average, 55% of the individuals at each site were in the orders Ephemeroptera, Plecoptera or Trichoptera. Dipteran taxa (mostly chironomids) accounted for another 34%. At almost all sites, non‐insects made up <10% of the macroinvertebrate assemblage. Almost half (49%) of the assemblages were collectors; remaining individuals were about evenly divided among scrapers, shredders and predators. 3. There were 189 different macroinvertebrate taxa at the 167 sites with richness at individual sites ranging from 7 to 71 taxa. Ordination by non‐metric multidimensional scaling revealed a strong association between % Ephemeroptera, especially Baetis, and site scores along the first axis. This axis was also strongly related to % coarse substratum and fast water habitat. The second axis was strongly related to % intolerant individuals, site slope and altitude. No strong relationships were evident between any ordination axis and either logging activity, presence/absence of fish, catchment size or ecoregion. 4. Based on macroinvertebrate index of biotic integrity (IBI) scores, 62% of the sites had no impairment, 31% of the sites had slight impairment and only 6% of the sites had moderate or severe impairment. IBI scores were not strongly related to forest harvest history. All four severely impaired sites and five of the seven sites with moderate impairment were lower altitude, shallower slope stream reaches located in the Coast Range with evidence of agricultural activity in their catchment or riparian zone. % sand + fine substratum was the environmental variable most strongly related to macroinvertebrate IBI.     

Flow permanence and macroinvertebrate community diversity within groundwater dominated headwater streams and springs

The response of aquatic macroinvertebrate communities to flow permanence within limestone springs and headwater streams was examined across the English Peak District. At the regional scale, macroinvertebrate communities of perennial and intermittent springs displayed significant differences in the number of taxa, macroinvertebrate community abundance, diversity indices (Shannon and Simpson indices) and the Berger–Parker dominance index at intermediate discharge. However, no significant difference was recorded between intermittent and perennial sites at high discharge or when all sampling occasions were pooled. At the catchment scale, the number of taxa, community abundance and Bray–Curtis similarity coefficients within the River Lathkill differed significantly between intermittent springs and other habitats. At both the regional and catchment scale the macroinvertebrate communities of intermittent springs were characterised by a small number of taxa displaying life cycle adaptations to intermittent aquatic habitats, particularly Trichoptera.     

Drought refuges,spatial scale and recolonisation by invertebrates in non‐perennial streams

1. If resistance traits drive recolonisation after drought, then drought refuges should contribute strongly to assemblage composition within streams. If resilience traits drive recolonisation, macroinvertebrates emerging from refuges may disperse widely, colonising many streams. To determine whether the contribution of drought refuges to macroinvertebrate recolonisation in non‐perennial streams was mostly local (within stream) or broader scale (across streams), we measured the association between the composition of invertebrate assemblages in different types of in‐stream drought refuge and the assemblage composition of streams when flow resumed. 2. We sampled 16 streams of varying hydrological regime on the western side of the Victoria Range in the Grampians National Park, Victoria, Australia. Drought refuges (perennial pools, dry sediment, damp sediment, seeps, patches of leaf litter, beneath stones) were identified and sampled during autumn. Most taxa were found in perennial pools; few taxa were found aestivating beneath stones or having desiccation‐resistant stages in dry sediment. Perennial pools and perennially flowing reaches were the refuges that harboured the greatest diversity of macroinvertebrate taxa. 3. Streams were sampled again during spring. Assemblage composition of non‐perennial reaches in spring was unrelated to composition in nearby refuges in the previous autumn. In contrast, assemblage composition in perennial reaches during spring was strongly correlated with composition during autumn. Therefore, drought refuges did not directly influence assemblage composition locally within non‐perennial streams. Rather, both perennially flowing reaches and perennial pools acted as drought refuges across the broader landscape. Resilience traits are likely to drive recolonisation in these streams. 4. Monitoring of drought refuges in a particular stream will therefore not predict species composition when flow resumes. Drought refuges are likely to sustain biodiversity over larger spatial scales such as groups of streams or whole drainage networks. Consequently, stream networks will need to be managed as entities rather than as single waterways and the focus of drought refuge protection should be on perennial pools and reaches.     

Relations Between River Plant Richness in the Portuguese Floodplains and the Widespread Water Knotgrass <Emphasis Type="Italic">(Paspalum Paspalodes</Emphasis>)

We examined the variability of macroinvertebrate assemblage structure, species identities, and functional feeding group composition in relation to stream size, tributary position, and in-stream factors in a boreal watershed in Finland. Our study included three riffle sites in each of three stream sections in each of three stream size classes. Multi-response permutation procedure, indicator value method, and canonical correspondence analysis revealed clear differences in assemblage structure among the stream size classes, with a gradual increase of species richness as the stream size increased. Significant differences in assemblage structure were also found among the tributary river systems. The functional feeding group composition broadly followed the river continuum concept, i.e., headwaters were dominated by shredders, gatherers, or filterers, whereas scrapers increased in relative abundance with stream size. There was, however, considerable variation in the functional feeding group composition both among and within the headwater stream sections. Our findings refer to a strong influence of stream size on macroinvertebrate assemblages, but also factors prevailing at the scale of individual riffles should be considered in biodiversity conservation of lotic ecosystems.     

Macroinvertebrate communities in streams with contrasting water sources in the Japanese Alps

Alpine streams are typically fed from a range of water sources including glacial meltwater, snowmelt, groundwater flow, and surface rainfall runoff. These contributions are projected to shift with climate change, particularly in the Japanese Alps where snow is expected to decrease, but rainfall events increase. The overarching aim of the study was to understand the key variables driving macroinvertebrate community composition in groundwater and snowmelt‐fed streams (n = 6) in the Kamikochi region of the northern Japanese Alps (April–December 2017). Macroinvertebrate abundance, species richness, and diversity were not significantly different between the two stream types. Community structure, however, was different between groundwater and snowmelt‐fed streams with macroinvertebrate taxa specialized for the environmental conditions present in each system. Temporal variation in the abundance, species richness, and diversity of macroinvertebrate communities was also significantly different between groundwater and snowmelt streams over the study period, with snowmelt streams exhibiting far higher levels of variation. Two snowmelt streams considered perennial proved to be intermittent with periodic drying of the streambed, but the macroinvertebrates in these systems rebounded rapidly after flows resumed with no reduction in taxonomic diversity. These same streams, nevertheless, showed a major reduction in diversity and abundance following periods of high flow, indicating floods rather than periodic drying was a major driver of community structure. This conclusion was also supported from functional analyses, which showed that the more variable snowmelt streams were characterized by taxa with resistant, rather than resilient, life‐history traits. The findings demonstrate the potential for significant turnover in species composition with changing environmental conditions in Japanese alpine stream systems, with groundwater‐fed streams potentially more resilient to future changes in comparison to snowmelt‐fed streams.     

Macroinvertebrate community loss as a result of headwater stream acidification in the Vosges Mountains (N-E France)

The relationships between water chemistry and aquatic macroinvertebrate communities of 41 headwater streams were studied in the Vosges Mountains (N-E of France) in an attempt to assess the impact of acidification on macroinvertebrate diversity. The taxa richness of macroinvertebrates decreased drastically in headwater streams which were characterized by low pH, low calcium and high aluminum content. All taxonomic groups were affected, but Molluscans, Crustaceans and Ephemeroptera disappeared totally from strongly acidified streams. Simple indices based on taxa richness such as the coefficient of community loss may provide accurate tools to quickly assess the impact of acidification on macroinvertebrate communities. Despite the reduction of atmospheric SO₂ emissions, acidification of freshwater in the Vosges Mountains continues to affect streams which were believed in the past to constitute refuge biotopes for numerous species. Consequently, acidification represents a real threat for numerous invertebrates. This study arises the question of the evolution in the future of headwater stream ecosystems. Urgent decisions and interventions are required to preserve non-acidified streams and to restore impacted ecosystems while awaiting spontaneous recovery.     

Loss of functionally important and regionally endemic species from streams forced into intermittency by global warming

Climate change is altering hydrological cycles globally, and in Mediterranean (med-) climate regions it is causing the drying of river flow regimes, including the loss of perennial flows. Water regime exerts a strong influence over stream assemblages, which have developed over geological timeframes with the extant flow regime. Consequently, sudden drying in formerly perennial streams is expected to have large, negative impacts on stream fauna. We compared contemporary (2016/17) macroinvertebrate assemblages of formerly perennial streams that became intermittently flowing (since the early 2000s) to assemblages recorded in the same streams by a study conducted pre-drying (1981/82) in the med-climate region of southwestern Australia (the Wungong Brook catchment, SWA), using a multiple before-after, control-impact design. Assemblage composition in the stream reaches that remained perennial changed very little between the studies. In contrast, recent intermittency had a profound effect on species composition in streams impacted by drying, including the extirpation of nearly all Gondwanan relictual insect species. New species arriving at intermittent streams tended to be widespread, resilient species including desert-adapted taxa. Intermittent streams also had distinct species assemblages, due in part to differences in their hydroperiods, allowing the establishment of distinct winter and summer assemblages in streams with longer-lived pools. The remaining perennial stream is the only refuge for ancient Gondwanan relict species and the only place in the Wungong Brook catchment where many of these species still persist. The fauna of SWA upland streams is becoming homogenised with that of the wider Western Australian landscape, as drought-tolerant, widespread species replace local endemics. Flow regime drying caused large, in situ alterations to stream assemblage composition and demonstrates the threat posed to relictual stream faunas in regions where climates are drying.     

Macroinvertebrate survival during cessation of flow and streambed drying in a lowland stream

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Across-reach consistency in macroinvertebrate distributions among litter patch types in Japanese headwater streams

Different types of litter patches with contrasting macroinvertebrate assemblages have been observed within a stream reach. This study examined whether distributions of macroinvertebrates among three litter patch types (riffle, middle, edge) were consistent between reaches with different channel characteristics in headwater streams in central Japan. Mass of leaves per unit area was significantly higher in riffle and edge patches than in middle patches, which was consistent between reaches, while no consistent pattern was evident between reaches for mass of either woody material or small litter fragments. Distribution among the patch types was consistent between reaches for 11 out of 13 dominant macroinvertebrate taxa; density was highest in riffle patches for 5 taxa and in middle patches for 5 taxa. Although we previously related densities of some taxa to mass of woody material or small litter fragments, hydraulic characteristics (water depth, current velocity), which were consistent between reaches, may be more important determinants of macroinvertebrate distributions among the patch types, even within pools (i.e. middle and edge patches) where current is uniformly low. The results of this study indicate that a reach-scale macroinvertebrate community structure associated with litter is likely to vary according to litter patch type composition, which would be affected by channel characteristics of the reaches.     

Macroinvertebrate community structure,secondary production and trophic‐level dynamics in urban streams affected by non‐point‐source pollution

1. Despite non‐point‐source (NPS) pollution being perhaps the most ubiquitous stressor affecting urban streams, there is a lack of research assessing how urban NPS pollution affects stream ecosystems. We used a natural experimental design approach to assess how stream macroinvertebrate community structure, secondary production and trophic structure are influenced by urban NPS pollution in six streams. 2. Differences in macroinvertebrate community structure and secondary production among sites were highly correlated with stream‐water specific conductivity and dissolved inorganic phosphorus (DIP) concentrations. Macroinvertebrate richness, the Shannon diversity index and the Shannon evenness index were all negatively correlated with specific conductivity. These patterns were driven by differences in the richness and production of EPT and other intolerant taxa. Production of the five most productive taxa, tolerant taxa, non‐insect taxa and primary consumers were all positively correlated with stream‐water DIP. 3. Despite the positive correlation between primary consumer production and DIP, there was no correlation between macroinvertebrate predator production and either total or primary consumer macroinvertebrate production. This was observed because DIP was positively correlated with the production of non‐insect macroinvertebrate taxa assumed to be relatively unavailable for macroinvertebrate predator consumption. After removing production of these taxa, we observed a strong positive correlation between macroinvertebrate predator production and production of available prey. 4. Our results suggest that urban NPS pollution not only affects macroinvertebrate community structure, but also alters secondary production and trophic‐level dynamics. Differences in taxon production in our study indicate the potential for altered energy flow through stream food webs and potential effects on subsidies of aquatic insect prey to riparian food webs.     

Diet composition of two larval headwater stream salamanders and spatial distribution of prey

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长白山源头溪流底栖动物群落结构季节动态

源头溪流是河流生态系统物质循环和能量流动的重要区域,对底栖动物的生物多样性维持具有重要意义。目前,针对我国源头溪流底栖动物群落结构的研究薄弱,对长白山源头溪流底栖动物季节动态的研究尚未见报道。采用野外原位定量取样的方法,力图阐释长白山源头溪流底栖动物群落结构的季节动态特征及其主要环境驱动因子。研究结果表明:(1)共计采集底栖动物90个分类单元,隶属于3纲9目38科。其中,水生昆虫85属,占绝对优势。底栖动物群落结构的季节动态明显,底栖动物密度及多样性在夏、秋季显著高于冬季和春季,并在冬季达到最低值。(2)底栖动物功能摄食类群以收集者占优势,其次为撕食者、捕食者和刮食者,滤食者相对丰度最低。不同功能摄食类群的季节动态不一致,但密度和物种丰富度整体表现为秋季最高。(3)水温、凋落叶分布和流速是长白山源头溪流底栖动物群落结构季节动态的主要环境驱动因子。本研究可为长白山源头溪流后续相关研究及长白山松花江水系生态修复提供基础数据支持及参考。     

The effect of fine sedimentation on tropical stream macroinvertebrate assemblages: a comparison using flow-through artificial stream channels and recirculating mesocosms

In-situ artificial stream channels and ex-situ laboratory mesocosms were used to measure the responses of macroinvertebrate assemblages, from upland and lowland tropical streams, to high loads of fine clay sediment. Significant responses were observed mainly in the in-situ channels in the upland stream, where densities and the number of taxa were lower in the treatment channels than in controls. There was no evidence of any taxon being particularly sensitive to sedimentation, with a general decrease in densities across several taxa and differences only detectable for abundant taxa. Animals moved downstream in response to the treatment, but only a short distance within the channels. However, further colonization after the treatment was impeded in the treatment channels. In the mesocosm experiments, the upland macroinvertebrate assemblage demonstrated some negative effects; however, the lowland fauna was very tolerant to sedimentation, even when exposure was extended to 15 days. Together, the mesocosm and in-situ experiments indicate that there is a behavioural response to sedimentation because of a change in the habitat, and that the lowland macroinvertebrate assemblage is more tolerant of sedimentation, at least in the short term. Handling editor: D. M. Harper     

Energy flow and the trophic basis of macroinvertebrate and amphibian production in a neotropical stream food web

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Macroinvertebrate Assemblages of an Andean High‐Altitude Tropical Stream: The Importance of Season and Flow

We studied the Piburja stream, a high‐altitude tropical stream in Ecuador. Our main goals were to determine whether the macroinvertebrate community composition and abundance differed between seasons, reaches and velocity patches. Likewise, we aimed to examine the importance of the hydrological regime in determining these differences. Flow was significantly higher in the wet season, but the stability of flow was higher in the dry season. There was a strong increase in macroinvertebrate community metrics (richness, density and diversity) in the dry season. Seasons and velocity patches better explained the community composition. Reaches did not show differences at the community level, but some taxa showed significant differences among reaches. Our findings differed from those published in previous studies that have suggested that mountain tropical streams are non‐seasonal. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Structural and functional aspects of treated mine water and aquaculture effluent streams

Multiple effluent streams may flow into a single receiving stream making it difficult to understand the effects of a single effluent source or the interactions between effluents. In this study, we examined benthic community structure and function in an effluent stream formed by the release of treated mine water, in treated mine water that had been used as a water source for flow-through aquaculture and below the confluence of the two. This study demonstrated that macroinvertebrate communities, while taxonomically simple, developed in treated mine water. The addition of aquaculture effluent to the treated mine water allowed colonization by additional taxa, increased leaf decomposition rates and may have conferred resistance to a turbidity event. Ecosystem responses were mediated by the surrounding terrestrial environment. In shaded conditions macroinvertebrate densities could be as much as 10× higher and the taxa were dominated by simuliids and chironomids, while in open conditions filamentous algae flourished and the taxa were dominated by hydroptilids and chironomids. Consequently, consideration of stream processes that promote preferred ecological processes, such as macroinvertebrate production and organic matter processing, when siting effluent streams may reduce impacts on receiving streams.     

Ecological function of constructed perennial stream channels on reclaimed surface coal mines

Mountaintop removal–valley fill mining results in the conversion of steep, forested headwater catchments to low gradient and open canopy channels. We compared the ecological functions of five reference stream channels to five constructed channels (age ranging from 3 to 20 years) on reclaimed mines in southern West Virginia. Variables included stream flow, habitat, water chemistry, riparian vegetation, organic matter (OM) processing, and invertebrate and amphibian communities. Although dissolved metal concentrations remained low, constructed channels produced significantly higher levels of conductivity and total dissolved solids as compared to reference streams. Macroinvertebrate and amphibian richness were comparable between constructed and reference channels; however, there was a distinct shift from sensitive lotic taxa in reference channels to tolerant lentic taxa in constructed channels. Constructed channels also had reduced OM decomposition rates. Nevertheless, constructed channels had significantly higher OM retention than reference channels, and consequently exhibited significantly higher overall OM processing and higher dissolved carbon concentrations. As the time since reclamation increased, we observed slight declines in conductivity and significant increases in total invertebrate richness. Our results provide measures of functional equivalencies between reference and constructed streams, which can serve as a basis for informed permitting and mitigation decisions in mined watersheds.     

Hydrological extremes modulate nutrient dynamics in mediterranean climate streams across different spatial scales

We studied benthic macroinvertebrate communities upstream and downstream of five small reservoirs (surface release in autumn–winters) (north Spain) to assess the effect of flow regulation on structural and functional characteristics of stream ecosystems. We based our approach on the use of structural metrics (density, biomass, richness and diversity) in combination with two functional diversity indices based on biological and ecological traits: FD_PG index, related to species richness, and FD_Q, which incorporates evenness across taxa. Although water physicochemical parameters were unaffected by the reservoirs during the study period (autumn–winter), macroinvertebrate metrics were lower below the dams, with detritivores (shredders and collector-gatherers) being the most affected. The alder leaf breakdown rate estimated by the litter-bag technique was related to the density, biomass, richness, diversity and FD_PG index of shredders, compromising the ecosystem functioning. The most plausible origin for the observed differences in macroinvertebrate metrics between upstream and downstream reaches was the change of the flow regime caused by the impoundments at downstream sites, leading to droughts in summer in those naturally permanently flowing streams. The observed functional diversity loss might reduce the chances of the community to override natural or man-induced fluctuations in their environment with possible repercussions on important ecosystem functions and services.     

Macroinvertebrate community structure and altitudinal changes in the upper reaches of a warm temperate southern African river

1. The Buffalo River rises 1200m above sea level, drops 600m in the first 7km, and a further 100m in the next 30 river kilometres. Macroinvertebrates were sampled, and environmental variables measured monthly in 1987, at four sites along this part of the river. 2. Flow at the headwater site (1120m a.s.l., 1 km from the source) was seasonal, though pools remained and subterranean flow was continuous. Twelve macroinvertebrate taxa were found exclusively at this site, where conductivity, pH and nutrient concentrations were low. 3. Flow at the foothill site (530m a.s.l., 7km from the source) was perennial. The invertebrate community, although distinct from that at downstream sites, lacked the unique taxa of the headwater site. Conductivity, pH and nutrient concentrations were higher. 4. The two sites downstream of the foothills (450m a.s.l., 18km from the source, and 410m a.s.l., 31 km from the source), had similar invertebrate communities. Conductivity, pH and nutrient concentrations were higher than at the upper sites. 5. Community structure changed most between the headwater and foothill sites. This paralleled changes in river steepness rather than changes in measured physicochemical variables.     

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.