Long-term recovery of a mountain stream from clear-cut logging: the effects of forest succession on benthic invertebrate community structure

1. Changes in benthic invertebrate community structure following 16 years of forest succession after logging were examined by estimating benthic invertebrate abundance, biomass and secondary production in streams draining a forested reference and a recovering clear-cut catchment. Benthic invertebrate abundance was three times higher, and invertebrate biomass and production were two times higher in the disturbed stream.
2. Comparison of invertebrate community abundance 1, 5 and 16 years after clear-cutting indicated that the proportion of scrapers had decreased, whereas shredders had increased. Functional group percentage similarity indicated that the invertebrate community in the disturbed stream 16 years after clear-cutting was more similar to the reference than to that found earlier in the disturbed stream.
3. The five indices calculated from data collected over the past 16 years, as well as the abundance, biomass and production data collected during this study, proved to be of differing value in assessing recovery of the disturbed stream from logging. Percent dominant taxon and EPT (Ephemeroptera, Plecoptera and Trichoptera) taxon richness failed to show any initial differences between reference and disturbed streams, indicating that these indices may not be useful for measuring recovery from logging. The percentage Baetis and shredder–scraper indices showed significant differences only during the 1977 study and suggest recovery (no difference between reference and disturbed) by 1982. The North Carolina Biotic Index showed continued differences during 1982 in the riffle and depositional habitats and recovery by 1993. Total macroinvertebrate abundance, biomass and production, as well as EPT abundance, indicated continued differences between the reference and disturbed streams in the 1993 study.     

Stream hydraulics as a major determinant of benthic invertebrate zonation patterns

SUMMARY. 1. Studies on the zonation of benthic fauna in fourteen streams situated in a variety of latitudes from Alaska to New Zealand have been evaluated.
2. We suggest that physical characteristics of flow ('stream hydraulics') are the most important environmental factor governing the zonation of stream benthos on a world-wide scale.
3. From the source to the mouth of a stream, zones of transition in stream hydraulics' occur, to which the general pattern of stream invertebrate assemblages can be related. In these zones benthic community stability and resilience must be different from those upstream and downstream of the hydraulic transition zones.     

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.     

The influence of microhabitat on availability of drifting invertebrate prey to a net-spinning caddisfly

SUMMARY. 1. Invertebrate drift was sampled at both a rockface and a deep pebble riffle site in streams draining both a clearcut and a forested catchment.
2. A sampler was designed to separate the bottom 2 cm of flow, encompassing the effective range of caddisfly (Hydropsychidae: Trichoptera) catchnets. from upper flow.
3. No significant difference in drift density (numbers per cubie metre) was seen between sites within each stream. However, numbers per square centimetre intake area per day at the rockface sites were 4 times higher in the clearcut and 10 times higher in the forested stream than at the pebble-riffle site.
4. Rockface habitat which had highest drift availability was also the site of maximum secondary production of the predaceous collector- filterer Parapsyche cardis in both streams studied.
5. Increased sediment load in the clearcut stream may influence the efficiency of utilization of invertebrate drift by collector-filterers.     

Physico-chemistry and aquatic insects of a glacier-fed and a spring-fed alpine stream

1. Physico-chemical conditions and benthic macroinvertebrates were studied in two adjacent alpine streams in the Tyrolean Alps, Austria, for 2 years, and aquatic insect emergence was recorded for 1 year.
2. In the spring-fed system, maximum discharge and increased concentrations of suspended solids, nitrate and particulate phosphorus occurred during snowmelt in June. In the glacier-fed stream, high discharge and strong diel fluctuations in flow and concentrations of suspended solids created a harsh and unstable environment during summer. Glacial ablation, variation in groundwater inflow, and water inputs from tributaries draining calcareous rocks caused water chemistry to vary both seasonally and longitudinally in glacier-fed Rotmoosache.
3. A total of 126 aquatic or semi-aquatic invertebrate taxa were collected, 94 of which were found in the glacier-fed stream and 120 in the spring-fed stream. Chironomid abundance was 2–8 times and taxa richness 2–3 times lower in the glacier-fed stream than in the spring-fed stream, as was the number of chironomid taxa (72 versus 93 total).
4. These results broadly support the conceptual model by Milner & Petts (1994) concerning glacier-fed stream systems. However, single samples and seasonal means showed relatively high invertebrate abundance and richness, especially during winter, indicating a considerable degree of spatial and temporal variability.
5. We suggest that the seasonal shifts from harsh environmental conditions in summer to less severe conditions in autumn and a rather constant environment in winter are an important factor affecting larval development, life-history patterns and the maintenance of relatively high levels of diversity and productivity in glacier-fed streams.     

Forests and the temperature of upland streams in Wales: a modelling exploration of the biological effects

SUMMARY. 1. Daily temperature data from six streams in upland Wales were used to explore the thermal effects of afforestation on stream ecology. The data were linked to published biological models to simulate fish and invertebrate development.
2. Mean daily temperatures in forest streams were lower than those of moorland streams in spring and summer, and higher in winter. These spatial comparisons were supported by the results of experimental bank-side clearance at a forest site, where there was evidence that stream temperatures fell in winter and rose in spring following treatment.
3. Simulations indicated that brown trout (Salmo trutta) could weigh over 30% more by the end of their second growing season in a moorland compared with a forest stream. Several species of insects showed slower simulated egg development at forest sites. For two ephemeropteran species simulated nymphal growth was also retarded, suggesting significant alterations to the life cycle. Two plecopteran species were affected only slightly by the different temperature regimes.
4. Overall, the simulations suggested that afforestation, by reducing summer temperatures, could lead to marked reductions in rates of development of some invertebrates and fish.     

Macroinvertebrate community structure in relation to environmental variables in a Swiss glacial stream

1. Benthic macroinvertebrate distribution was examined in relation to channel characteristics (including stability), substratum, hydraulic variables, primary production (chlorophyll a ) and coarse particular organic matter (CPOM) in an alpine glacial stream, the Mutt (Upper Rhône valley, Switzerland). Co-inertia analysis and canonical correspondence analysis were used to identify the major environmental gradients influencing community variations.
2. The Mutt (length: 3.6 km, altitudinal range: 1800–3099 m a.s.l.) exhibited typical characteristics of a kryal stream. Average summer temperature remained below 2 °C immediately downstream from the snout but was on average 5 °C higher 1700 m downstream. Seasonal variations in water sources were evidenced by the high late-summer (September) contribution of groundwater with increased conductivity.
3. Sixty-six taxa were recorded from the five reaches sampled at three periods (snowmelt, ice melt and low water in late summer) in 1996 and 1997, of which 29 were Chironomidae. Three taxa of Diamesinae were the first colonizers of the stream below the glacier, but 16 taxa, including Ephemeroptera, Plecoptera and Trichoptera, were already recorded 200 m downstream. Water depth, channel slope and Pfankuch's Index of channel stability were strongly correlated with the longitudinal faunal gradient. Maximum temperature, current velocity and water conductivity were also correlated, but to a lesser extent.
4. The rapid incorporation of non-chironomid taxa into the stream community represented a departure from Milner & Petts's (1994) conceptual model of invertebrate succession downstream of glacial margins. The results confirmed that glacial stream communities are primarily driven by physical determinants.     

Setting Attainable Goals of Stream Habitat Restoration from a Macroinvertebrate View

Many efforts have been undertaken to reduce the impairment of stream ecosystems by wastewaters and other pollution, leading to a remarkable improvement of the water quality in most parts of Central Europe. Actually, the most severe disturbance to stream systems in Central Europe is the structural degradation of stream morphology. Restoration practices increasing the structural heterogeneity of formerly degraded stream sections are necessary to create new habitats at different scales that could provide habitat for a diverse invertebrate community. Increasing biodiversity of aquatic invertebrates strengthens the ecological integrity of streams and is therefore a desirable goal in stream restoration. Nevertheless, recent studies focusing on the effect of structural restoration of stream sections often displayed results that did not really met the preset goal of increasing invertebrate diversity. This might be due to sometimes severe disturbance caused by the restoration practice itself, impairing the established invertebrate community in the restored stream section. Additionally, the potential for immigration of new species into the restored stream section is often limited. Therefore, several important prerequisites must be accounted for in the planning of restoration practices to improve structurally degraded stream sections, when the goal of restoration is increasing invertebrate diversity.     

Stimulation of leaf litter decomposition and associated fungi and invertebrates by moderate eutrophication: implications for stream assessment

1. We investigated the effect of moderate eutrophication on leaf litter decomposition and associated invertebrates in five reference and five eutrophied streams in central Portugal. Fungal parameters and litter N and P dynamics were followed in one pair of streams. Benthic invertebrate parameters that are considered useful in bioassessment were estimated in all streams. Finally, we evaluated the utility of decomposition as a tool to assess stream ecosystem functional integrity. 2. Decomposition of alder and oak leaves in coarse mesh bags was on average 2.3–2.7× faster in eutrophied than in reference streams. This was attributed to stimulation of fungal activity (fungal biomass accrual and sporulation of aquatic hyphomycetes) by dissolved nutrients. These effects were more pronounced for oak litter (lower quality substrate) than alder. N content of leaf litter did not differ between stream types, while P accrual was higher in the eutrophied than in the reference stream. Total invertebrate abundances and richness associated with oak litter, but not with alder, were higher in eutrophied streams. 3. We found only positive correlations between stream nutrients (DIN and SRP) and leaf litter decomposition rates in both fine and coarse mesh bags, associated sporulation rates of aquatic hyphomycetes and, in some cases, total invertebrate abundances and richness. 4. Some metrics based on benthic invertebrate community data (e.g. % shredders, % shredder taxa) were significantly lower in eutrophied than in reference streams, whereas the IBMWP index that is specifically designed for the Iberian peninsula classified all 10 streams in the highest possible class as having ‘very good’ ecological conditions. 5. Leaf litter decomposition was sufficiently sensitive to respond to low levels of eutrophication and could be a useful functional measure to complement assessment programmes based on structural parameters.     

Invertebrate colonisation of the gravel substratum of an experimental recirculating channel

The development of an invertebrate community in a large scale, experimental stream system is described. Colonisation was chiefly by means of ovipositing adult insects with lesser components introduced with water and stones. A succession of taxa was recorded with large peaks of numbers in the spring and the autumn, comparable to those observed in studies on natural streams. Diversity of the fauna increased quickly at first and then more slowly, possibly because of the reduced availability of ovipositing adults later in the year. Even in the absence of drift and migration, recruitment of insect larvae, which naturally favour gravel substrata in running water, can be rapid and will produce a varied community in which Chironomidae and Ephemeroptera play an important role.     

A comparison of bacteria and benthic invertebrates as indicators of ecological health in streams

1. We set out to evaluate the reliability of bacterial communities as an indicator of freshwater ecological health.
2. Samples of epilithic biofilm were taken over a 1-year period from four streams, each impacted by varying degrees of human modification. The bacteria within each sample were characterised using a whole community DNA fingerprinting technique (automated ribosomal intergenic spacer analysis). Spatial and temporal differences in community structure between samples were visualised using multi-dimensional scaling and quantified using permutational multivariate anova . Macrobenthic invertebrates, which are commonly used as indicators of stream ecological health, were also sampled for comparison.
3. Multivariate analysis revealed a clear gradient in macroinvertebrate community structure between sites exposed to increased human impact. Bacterial communities, however, could only distinguish the most impacted site from the remainder.
4. Additional research is required to increase the sensitivity of bacterial community analyses before endorsing their use as an indicator of freshwater ecological health.     

Forest canopy cover determines invertebrate diversity and ecosystem process rates in depositional zones of headwater streams

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Community structure in some southern English streams: the influence of species interactions

SUMMARY. 1. The results of a survey of thirty-four stream sites, differing in pH and invertebrate species richness, indicated that the pool of locally available, suitably adapted species was smaller in the acid streams. This plays a part in determining the general pattern of lower species richness at more acid sites.
2. Diversity of feeding categories increased with species richness, indicating that a greater range of food resources was available in the less acid, more species-rich communities.
3. The pattern of predation varied with pH and species richness. The numbers of large insect predators were lower in the less acid, more species-rich communities and this was correlated with the presence of fish.
4. A detailed study of the guild of detritivorous stoneflies in four streams differing in species richness provided evidence that density compensation occurs, niche width decreases and niche overlap declines as species richness increases.
5. We discuss the roles that competition and predation play in determining the structure and richness of stream invertebrate communities.     

Vegetation and flow regime in lowland streams

1. The hydrological regime is important to the distribution of benthic organisms in streams. The objective of this study was to identify relationships between hydrological variables, describing the flow regime, and macrophyte cover, species richness, diversity and community composition in Danish lowland streams.
2. We quantified macrophyte vegetation in 44 Danish streams during summer by cover, species richness and diversity. Flow regime was characterized by 18 non-intercorrelated variables describing magnitude, frequency and duration of low and high flow events, timing or predictability of flow and general flow variability.
3. We found support in the stepwise multiple regressions analysis for our expectation that macrophyte cover is lowest in streams with high flow variability and highest in streams with long duration of low flow and low flow variability. We found support for the intermediate disturbance hypothesis as there were significant quadratic relationships between species richness and diversity as functions of disturbance frequency. There was poor discrimination in a detrended correspondence analysis (DCA) analysis of macrophyte community composition between four twinspan groups separating streams with different hydrological properties. Moreover, we did not find any relationship between the presence of disturbance-tolerant species and hydrological disturbance, suggesting that plant community composition developed independently of stream hydrology.     

Ecology of leaf pack macroinvertebrate communities in streams of the Fraser River Basin, British Columbia

1. To characterise geographic and small scale variation in the structure of macroinvertebrate communities in stream leaf packs, we collected one to three natural leaf pack communities from 119 reference streams in the Fraser River Basin and quantified their variability and correlation with aspects of the stream environment at several scales. We also sampled leaf packs in 19 test streams in the same geographic area exposed to stressors (nine logged, seven farmed, three mined catchments) to evaluate the leaf pack community as a tool for bioassessment. 2. There was substantial variation in the composition of invertebrate communities in leaf packs among reference streams of the Fraser River Basin. Capnia and Zapada (stoneflies), Baetis and Ephemerella (mayflies) and Tvetnia (midge) were the most common taxa found in the leaf packs. There were three types of assemblages identified by non‐metric multidimensional scaling; Capnia, Baetis and Ephemerella communities. 3. Leaf pack communities from the 19 test streams were plotted on a non‐metric multidimensional scaling ordination of the reference communities, and 14 of 19 sites fell outside the 80% confidence ellipse of the reference sites, including eight of nine logged, four of seven farmed and one of three mined catchments. Most of these streams plotted on the ordination near the Ephemerella reference communities. Reference stream communities had a similar number of genera per leaf pack (12.0) and genera per site (18.7) as the test streams (12.6 genera per leaf pack and 18.7 genera per site). Among the test sites, the farmed catchments had higher genera per leaf pack (17.8) and genera per site (21.9) than either the logged (11.5 genera per leaf pack; 19.9 genera per site) or mined (3.4 genera per leaf pack; 7.7 genera per site) catchments. 4. Heterogeneity of leaf pack communities within a site decreased as the number of genera found at the site increased. This was determined by allometric regression of the number of genera found at a site on the maximum number of genera possible, given the average number found per leaf pack. 5. There was a significant relationship between the composition of the leaf pack invertebrate community and stream geography (latitude, longitude, altitude, stream order). Canonical correspondence analysis showed differences among ‘big river’, ‘mountain stream’ and ‘southern’ communities. 6. There was no relationship between the composition of the leaf pack invertebrate community and stream channel and flow characteristics (bank dimensions, flow, slope). There was a significant relationship between the composition of the leaf pack invertebrate community and water quality of the stream (oxygen, nitrogen, phosphorus, conductivity, pH, temperature). ‘Cold, oxygen rich water’ communities were distinguishable from communities in streams with warmer, lower oxygen concentration. ‘High nutrient water’ communities were also distinct from communities in low nutrient streams. There was no relationship between the composition of the leaf pack invertebrate community and the nature of the leaf pack itself (i.e. morphology, decomposition, coniferous needle content). 7. Invertebrate communities in leaf packs show substantial, interpretable variation among reference streams. They are sensitive to human stressors at a landscape scale such as forestry and agriculture. Their diversity and composition varies at different spatial scales in a way that is at least partially explained by the environment of the stream and its catchment area.     

Biophysical Controls on Community Succession in Stream Biofilms

Biofilm formation is controlled by an array of coupled physical, chemical, and biotic processes. Despite the ecological relevance of microbial biofilms, their community formation and succession remain poorly understood. We investigated the effect of flow velocity, as the major physical force in stream ecosystems, on biofilm community succession (as continuous shifts in community composition) in microcosms under laminar, intermediate, and turbulent flow. Flow clearly shaped the development of biofilm architecture and community composition, as revealed by microscopic investigation, denaturing gradient gel electrophoresis (DGGE) analysis, and sequencing. While biofilm growth patterns were undirected under laminar flow, they were clearly directed into ridges and conspicuous streamers under turbulent flow. A total of 51 biofilm DGGE bands were detected; the average number ranged from 13 to 16. Successional trajectories diverged from an initial community that was common in all flow treatments and increasingly converged as biofilms matured. We suggest that this developmental pattern was primarily driven by algae, which, as “ecosystem engineers,” modulate their microenvironment to create similar architectures and flow conditions in all treatments and thereby reduce the physical effect of flow on biofilms. Our results thus suggest a shift from a predominantly physical control to coupled biophysical controls on bacterial community succession in stream biofilms.     

Biophysical controls on community succession in stream biofilms

Biofilm formation is controlled by an array of coupled physical, chemical, and biotic processes. Despite the ecological relevance of microbial biofilms, their community formation and succession remain poorly understood. We investigated the effect of flow velocity, as the major physical force in stream ecosystems, on biofilm community succession (as continuous shifts in community composition) in microcosms under laminar, intermediate, and turbulent flow. Flow clearly shaped the development of biofilm architecture and community composition, as revealed by microscopic investigation, denaturing gradient gel electrophoresis (DGGE) analysis, and sequencing. While biofilm growth patterns were undirected under laminar flow, they were clearly directed into ridges and conspicuous streamers under turbulent flow. A total of 51 biofilm DGGE bands were detected; the average number ranged from 13 to 16. Successional trajectories diverged from an initial community that was common in all flow treatments and increasingly converged as biofilms matured. We suggest that this developmental pattern was primarily driven by algae, which, as "ecosystem engineers," modulate their microenvironment to create similar architectures and flow conditions in all treatments and thereby reduce the physical effect of flow on biofilms. Our results thus suggest a shift from a predominantly physical control to coupled biophysical controls on bacterial community succession in stream biofilms.     

Microbial leaf degraders in boreal streams: bringing together stochastic and deterministic regulators of community composition

1. Leaves that fall into the water represent a new habitat for microorganisms to colonise in streams, providing an opportunity to study colonisation and the subsequent regulation of community structure. We explored community composition of bacteria and fungi on decomposing alder leaves in nine streams in central Sweden, and describe their relationship with environmental variables. Succession of the microbial community was studied in one of the streams for 118 days. Microbial community composition was examined by denaturing gradient gel electrophoresis on replicate samples of leaves from each stream. 2. During succession in one stream, maximum taxon richness was reached after 34 days for bacteria and 20 days for fungi respectively. Replicate samples within this stream differed between each other earlier in colonisation, while subsequently such variation among replicate communities was low and remained stable for several weeks. Replicate samples taken from all the nine streams after 34 days of succession showed striking similarities in microbial communities within‐streams, although communities differed more strongly between streams. 3. Canonical analysis of microbial communities and environmental variables revealed that water chemistry had a significant influence on community composition. This influence was superimposed on a statistical relationship between the properties of stream catchments and microbial community composition. 4. The catchment regulates microbial communities in two different ways. It harbours the species pool from which the in‐stream microbial community is drawn and it governs stream chemistry and the composition of organic substrates that further shape the communities. We suggest that there is a random element to colonisation early in succession, whereas other factors such as species interactions, stream chemistry and organic substrate properties, result in a more deterministic regulation of communities during later stages.     

Microhabitat availability in Welsh moorland and forest streams as a determinant of macroinvertebrate distribution

SUMMARY. 1 Eighteen streams in mid-Wales were sampled for macro-invertebrates in both riffles and margins in April 1985–87. Stream macro-flora, substrata and marginal habitats were surveyed in May 1988.
2. TWINSPAN classification of the macroinvertebrate data indicated three major stream groups. One was distinguished by circumneutral pH and had a flora and fauna typical of such conditions. The other two groups consisted of acidic streams with moorland and conifer afforested catchments respectively. The forest streams were the more acidic but the two groups also differed significantly in the composition of their marginal habitats.
3 The acidic moorland streams had more vegetation ('soft' features) in the margins and supported several invertebrate taxa which were relative more abundant there than in the riffles. These taxa may be excluded from forest streams because the margins are 'hard' due to greater erosiveness and shading.
4. In view of the increasing cover by conifer afforestation in Britain, it is clearly necessary to elucidate all its effects on stream ecosystems, which include changes to the physical environment.     

Successional colonization of temporary streams: An experimental approach using aquatic insects

The metacommunity concept studies the processes that structure communities on local and regional scales. This concept is useful to assess spatial variability. However, temporal patterns (e.g., ecological succession and colonization) are neglected in metacommunity studies, since such patterns require temporally extensive, and hard to execute studies. We used experimental habitats in temporary streams located within the Brazilian Cerrado to evaluate the importance of succession for the aquatic insect metacommunity. Five artificial habitats consisting of wrapped crushed rock were set transversally to the water flow in five streams. The habitats were sampled weekly to assess community composition, and replaced after sampling to identify new potential colonizers. We analyzed the accumulation of new colonizers after each week using a logistic model. We selected pairs of experimental habitats and estimated the Bray-Curtis dissimilarity index to assess the community composition trajectory during the experiment. We used the dissimilarity values in ANOVA tests, identifying the importance of time and space for the community. The number of new taxa stabilized in the third week, and we estimated a weekly increase of 1.61 new taxa in the community after stabilization. The overall pattern was a small change on community composition, but one stream had a higher weekly turnover. Our results showed a relevant influence of time in the initial communities of aquatic insects of temporary streams. However, we must observe the temporal pattern in a spatial context, once different streams have different successional history regarding number of taxa and community turnover. We highlight the importance of aerial dispersal and movement to seek oviposition sites as an important factor in determining colonization patterns.