The macroinvertebrate communities of two contrasting Norwegian glacial rivers in relation to environmental variables

1. Macroinvertebrate communities in two Norwegian glacial rivers, one in the western fjords (Dalelva) and one in the eastern mountains (Leirungsåi), were investigated during three time periods in 1996 and 1997.
2. Channel stability variables (substratum heterogeneity/Pfankuch index/hydraulic stress) and water temperature accounted for 54% of the total inertia in the principal components analysis (PCA) ordination of environmental variables. The importance of these variables was confirmed by cluster analysis.
3. The two rivers were well separated in the ordinations, with Leirungsåi showing much greater heterogeneity. This is explained by differences in altitudinal range, terrestrial vegetation and the importance and nature of tributary inputs.
4. Channel stability and temperature were also important in determining faunal communities in the two glacial rivers, supporting the main determining variables in the conceptual model of glacial streams ( Milner & Petts, 1994 ). However, clear temporal differences were apparent in the data, the two rivers being more similar during the summer period of high discharge dominated by glacial meltwater. During spring and especially during autumn environmental conditions and the macroinvertebrate fauna differed both within and between rivers.
5. Diamesinae dominated in the upper reaches of both rivers, with Orthocladiinae becoming more common downstream. The dominance of Diamesinae persisted further down Dalelva because of the continued influence of glacial tributaries, whereas in Leirungsåi the influence of non-glacial tributaries led to a change towards a greater proportion of Orthocladiinae. Lakes modified macroinvertebrate communities in both river systems.     

The influence of glacial runoff on stream macroinvertebrate communities in the Taillon catchment, French Pyrénées

1. Benthic communities were sampled from five sites within a glacial catchment in the Cirque du Gavaranie, French Pyrénées, over two consecutive years (i) to investigate whether longitudinal patterns in zoobenthic communities exist downstream of a glacial margin and (ii) to identify the principal environmental variables influencing such patterns. 2. There was a distinct zonation of communities with increasing distance from the glacial margin. Ordination of the zoobenthic distribution indicated sites were separated by the relative contributions of taxa rather than their presence or absence. A shift in community composition and diversity separated a kryal type community dominated by Diamesa spp., Prosimulium spp., Eriopterini and Empididae at ≥2200 m a.s.l., from a more rhithral community of Orthocladiinae, Ephemeroptera, Plecoptera and Trichoptera at 1900 m a.s.l. 3. Chironomidae showed a defined gradient in distribution from Pseudokiefferiella parva and Diamesa latitarsis groups close to the glacier, through D. zernyi and D. cinerella groups, Orthocladius, Parametriocnemus and Micropsectra further downstream with Rheocricotopus, Corynoneura and Nilotanypus furthest from the glacial margin. Diamesa cinerella/zernyi group was the most euryzonal taxon. 4. Gradients in channel and hydraulic stability, groundwater input and mean water temperature were identified as the principal environmental variables associated with the downstream distribution gradient of zoobenthos. Diamesa, Empididae, Eriopterini and Nematoda were most tolerant of channel and hydraulically unstable and cold water habitats. Simuliidae (Prosimulium), Crenobia alpina, Rhyacophila, Chaetopterygini, Drusus rectus, Capnioneura, Orthocladius and Parametriocnemus were associated with intermediate conditions. Corynoneura, Tanypodinae, Perlidae, Chloroperlidae, Agapetus fuscipes and Coleoptera were least tolerant of channel and hydraulic instability and low water temperature.     

Particulate organic matter inputs to a glacial stream ecosystem in the Swiss Alps

1. Traps for litterfall and for lateral transport of organic matter were sampled over a 1-year period along longitudinal and lateral transects in a glacial stream system (Val Roseg, Swiss Alps), which is characterized by single-thread reaches and a large subalpine floodplain.
2. Allochthonous inputs to the glacier stream were low close to the glacier terminus but increased as woody riparian vegetation and forests develop. Annual inputs varied from 0.4 g ash free dry matter (AFDM) m^–2 year^–1 (direct input) and 0.7 g AFDM m^–2 year^–1 (lateral input) in the proglacial area to 23.0 g AFDM m^–2 year^–1 (direct input) and 10.7 g AFDM m^–2 year^–1 (lateral input) in the lowest reach with adjacent subalpine forests.
3. Direct inputs of organic matter decreased exponentially from forests at the floodplain edge to the floodplain centre, while lateral inputs of organic matter correlated linearly with distance to trees. Direct litterfall dominated litter input close to the forest, while lateral transport was the major pathway for channels more than 20 m away from the forest.
4. A conceptual framework is developed illustrating the influence of terrestrial vegetation and fluvial morphology on organic matter input along the continuum of glacial streams.     

Ecology of a saline stream: community responses to spatial gradients of environmental conditions

Spatial changes in structural and functional characteristics of fish and macroinvertebrate communities in eastern Kentucky were investigated in a drainage system chronically exposed to high levels of chloride salts from nearby oilfield operations. Salinity levels at biological monitoring stations ranged from 0.12–31.3‰. Lotic regions with salinities greater than 10‰ were dominated by larvae of the dipterans Ephydra and Culicoides. In regions with salinities less than 10‰ species richness increased more or less linearly with decreasing levels of chloride salts. Ephemeropterans appeared to be one of the major invertebrate groups least tolerant of elevated NaCl levels and were absent in regions with salinities greater than 2‰ Availability of food resources, such as periphyton and particulate organic matter, did not appear to be grossly altered in disturbed regions, and it is suggested that the observed distribution of macroinvertebrate fauna was largely in response to taxonomic differences in salt tolerance. Fish seemed to be more tolerant of highly saline conditions, and several species were observed in regions experiencing salinities as high as 15‰. Accordingly, assemblages of fish taxa along the salinity gradient may have been influenced by trophic factors, such as spatial limitations in availability of invertebrate prey.     

Longitudinal and seasonal distribution patterns of the benthic fauna of an alpine glacial stream (Val Roseg, Swiss Alps)

1. Seasonal changes in longitudinal patterns of environmental conditions and macroinvertebrate community distributions were examined in an alpine glacial stream (Roseg River, Switzerland). 2. Physico‐chemical parameters reflected seasonal changes in glacial influence via shifts in water sources and flowpaths (glacial meltwater versus ground water), and were best described by turbidity, particulate phosphorus and specific conductance. High nitrogen concentrations indicated snowmelt was the main water source in June. 3. Macroinvertebrate densities and taxon richness were highest during spring (4526 m^–2 and 16 taxa, all sites combined) and late autumn/early winter (8676–13 398 m^–2 with 16–18 taxa), indicating these periods may be more favourable for these animals than summer when glacial melting is maximal. Diamesa spp. (Chironomidae) dominated the fauna at the upper three sites (>95% of zoobenthos) and were abundant at all locations. Other common taxa at lower sites (1.2–10.6 km downstream of the glacier terminus) included other chironomids (Orthocladiinae, Tanytarsini), the mayflies Baetis alpinus and Rhithrogena spp., the stoneflies Leuctra spp. and Protonemura spp., blackflies (Simulium spp., Prosimulium spp.), and Oligochaeta. 4. Co‐inertia analysis revealed a strong relationship between environmental conditions and benthic macroinvertebrate assemblages. Furthermore, it elucidated temporal variability in longitudinal response patterns, as well as a similarity in temporal patterns among individual sites. 5. Our results suggest that zoobenthic gradients are not solely related to temperature and channel stability. Seasonal shifts in sources and pathways of water (i.e. extent of glacial influence), and periods of favourable environmental conditions (in spring and late autumn/early winter) also strongly influenced zoobenthic distributions.     

Macroinvertebrate species and assemblages in the headwater streams of the River Tyne,northern England in relation to land cover and other environmental variables

The macroinvertebrate species and assemblages of headwater streams of the River Tyne catchment in northern England were classified and their relationship with environmental variables based on stream structure, water acidity, distance from source and land cover investigated using constrained ordination and logistic regression. Fuzzy classification of data from 322 stream sites generated five assemblages. Stream structure, quantified as an exposure index, was found to be the most important environmental variable, with water acidity also important. Distance from source and land cover had less influence on species and assemblage distribution. A considerable amount of variation in assemblage distribution was explained using a two-variable logistic regression with stream structure (exposure index) and water acidity (pH) in a template. Site structure and water acidity appeared to be related to drift, geology and topography with little anthropogenic influence. The applicability of the habitat template concept for explaining the distribution of stream macroinvertebrates is discussed.     

Macroinvertebrate/sediment relationships along a pesticide gradient in Danish streams

Twenty-nine Danish streams were investigated in September 1998. The streams drained catchments of varying hydrology, topography, soil type and land use. In each stream, the newly accumulated streambed sediment was sampled and subsequently analysed for pesticides. In each stream, five replicate macroinvertebrate samples were taken in the same sediments as the pesticide samples. In addition, five samples were taken in riffles to provide a complete picture of macroinvertebrate community composition. The number of detected pesticides reflected soil type and land use: in agricultural catchments on clay soils the average number of pesticides were 4.3±2.2; on sandy soils 2.6±1.0, while only 1.5±0.6 pesticides were found in streams without agricultural activities. The macroinvertebrate composition showed clear changes along this gradient of sediment pesticide concentrations. The number of the amphipod Gammarus pulex was negatively correlated with sediment pesticide concentration, while the number of Oligochaeta and Hirudinae was positively correlated. The findings indicate that pesticides have a potential to structure macroinvertebrate communities in Danish streams. However, agricultural impact is more than pesticides, and several other factors, such as channelisation, affect the macroinvertebrate community and these are not easily separated.     

Patterns of macroinvertebrate traits along three glacial stream continuums

1. Glacier‐fed streams are characterised by low spatial but high temporal heterogeneity, manifested in seasonal and diurnal discharge and suspended sediment peaks induced by glacial runoff. These streams shelter macroinvertebrate communities adapted to such harsh environmental conditions. Studies relating macroinvertebrate traits to environmental conditions in glacial streams could provide important insights into the structure and function of glacial stream communities. 2. From data collected in three glacial streams from the central Swiss and southern French Alps, we analysed the relationships among six biological traits to define five groups of macroinvertebrate taxa with similar suites of traits. 3. The longitudinal distribution of the five groups and of individual traits was analysed, as well as their variation according to a glaciality index combining water temperature, conductivity, suspended solids and substrate stability. 4. The trait diversity along the three streams showed a strong upstream‐downstream gradient. The upper reaches were dominated by a single group of taxa characterised by small, crawling, deposit feeders. The other trait‐based groups appeared progressively downstream. 5. Changes in the relative frequency of trait‐based groups along the glaciality gradient highlighted the dominance of all‐rounder resistant/resilient traits in the three streams and confirmed that environmental conditions in the glacial streams are too harsh or uniform to allow macroinvertebrate communities to develop alternative suites of traits. The findings are discussed in relation to the question of trait coding in the available literature.     

Macroinvertebrate community traits and nitrate removal in stream sediments

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Benthic macroinvertebrate community structure in relation to food and environmental variables

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

Invertebrate drift in a glacial river and its non-glacial tributary

1. Invertebrate drift was studied in a glacially fed river and a non-glacial tributary in western Norway. Samples were taken during two consecutive 24-h periods in May, July and October 1997. The 3 months are characterized by snowmelt, ice melt and rainfall runoff, respectively. The main glacial river has colder, more turbid water, especially during the period of maximum ice melt during summer.
2. Chironomidae, especially the genus Diamesa , dominated the drift in the main river in May and October, constituting 97 and 99% of total numbers, respectively. Simuliidae, Plecoptera, Ephemeroptera and Trichoptera were the other main components.
3. A comparison of drift and benthos data revealed that the tributary was of little significance for colonization of the main glacial river. Only some additional species in very low numbers were recorded downstream of the confluence.
4. During July significant differences in diel drift pattern of Chironomidae and Simuliidae existed between the glacial and non-glacial reaches. There was a mid-day peak independent of discharge in the glacial river, but this peak was not noted in the tributary. Species of the genus Diamesa appear to be adapted for daytime drift, possibly evolved through the absence of predators and competitors that are typical of rhithral systems where nocturnal drift is more usual.     

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.     

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

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

Macroinvertebrate drift in a Rocky Mountain stream

An extensive series of drift collections from a Rocky Mountain stream was used to investigate quantitative patterns in the taxonomic composition of drift throughout spring, summer and fall for 1975–1978. Drift was estimated by drift rate, the number of organisms drifting past a point per 24 h; and by drift density, the numbers of organisms collected per 100 m³ of water sampled.Drift densities were up to ten times greater by night than by day, and 24 h drift densities for the total fauna approached 2000 per 100 m³ in June–July, declining to <500 by autumn. Ephemeroptera, and especially Baetis, dominated the drift. Drift rates were greatest in late spring, around 10⁶ per 24 h, which are among the highest values reported for small trout streams. Drift rates declined to <10⁵ during the summer, and shifts in the taxonomic composition are described.Multiple regression analysis of the relationship between drift rate and density, and the independent variables discharge, benthic density and temperature, showed that discharge typically was a significant predictor of 24 h drift rate, usually the best single predictor. In contrast, 24 h drift density most frequently was independent of discharge, indicating that this measure tends to correct for seasonal variation in discharge, as suggested in the literature. However, this was not invariably true. Drift density significantly correlated with benthic density in five of eight taxa inspected, thus seasonal declines in the benthos probably accounted for parallel declines in drift density.     

Macroinvertebrate assemblages in 25 high alpine ponds of the Swiss National Park (Cirque of Macun) and relation to environmental variables

High-altitude freshwater ecosystems and their biocoenosis are ideal sentinel systems to detect global change. In particular, pond communities are likely to be highly responsive to climate warming. For this reason, the Swiss National Park has included ponds as part of a long-term monitoring programme of the high-alpine Macun cirque. This cirque covers 3.6 km², has a mean altitude of 2,660 m a.s.l., and includes a hydrographic system composed of a stream network and more than 35 temporary and permanent ponds. The first two steps in the programme were to (i) make an inventory of the macroinvertebrates of the waterbodies in the Macun cirque, and (ii) relate the assemblages to local or regional environmental variables. Sampling was conducted in 25 ponds between 2002 and 2004. The number of taxa characterising the region (Macun cirque) was low, represented by 47 lentic taxa. None of them was endemic to the Alps, although several species were cold stenothermal. Average pond richness was low (11.3 taxa). Assemblages were dominated by Chironomidae (Diptera), and Coleoptera and Oligochaeta were also relatively well represented. Other groups, which are frequent in lowland ponds, had particularly poor species richness (Trichoptera, Heteroptera) or were absent (Gastropoda, Odonata, Ephemeroptera). Macroinvertebrate assemblages (composition, richness) were only weakly influenced by local environmental variables. The main structuring processes were those operating at regional level and, namely, the connectivity between ponds, i.e. the presence of a physical connection (tributary) and/or small geographical distance between ponds. The results suggest that during the long-term monitoring of the Macun ponds (started in 2005), two kinds of change will affect macroinvertebrate assemblages. The first change is related to the natural dynamics, with high local-scale turnover, involving the metapopulations characterising the Macun cirque. The second change is related to global warming, leading to higher local and regional richness through an increase in the number of colonisation events resulting from the upward shift of geographical ranges of species. At the same time the cold stenothermal species from Macun will be subject to extinction. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: R. Céréghino, J. Biggs, B. Oertli & S. Declerck The ecology of European ponds: defining the characteristics of a neglected freshwater habitat     

青弋江流域大型底栖动物群落结构及水质评价

研究河流大型底栖动物群落结构特征及水环境质量对水生态的保护与修复具有重要意义。以青弋江流域为研究对象,于2020年9月进行了大型底栖动物及水体理化因子的调查,采用相对重要性指数、生物多样性指数及Jaccard相似性系数分析了大型底栖动物群落结构特征,运用丰度/生物量比较曲线法及冗余分析法探究了底栖动物群落受到的干扰程度及其主要影响环境因子,最后利用水生态环境质量综合指数对河流水质进行评价。研究结果表明：(1)共采集鉴定大型底栖动物61种,隶属于3门6纲17目,平均丰度为265.9个/m~2,平均生物量41.6 g/m~2。相对重要性指数分析显示,日本沼虾(Macrobrachium nipponensis)、中国圆田螺(Cipangopaludina chinensis)、羽摇蚊(Chironomus plumosus)及扁蜉(Ecdyrus)为群落中的主要优势种。(2)由群落相似性分析知,Jaccard相似性系数较低,调查点位之间存在较强的空间异质性。(3)冗余分析表明,电导率、氨氮浓度及流速是影响底栖动物群落结构的主要环境因子。(4)生物指数分析结果显示该流域水质为轻度污染或中度污...     

Drought intensification alters the composition,body size,and trophic structure of invertebrate assemblages in a stream mesocosm experiment

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Macroalgae of a stream in southeastern Brazil: composition,seasonal variation and relation to physical and chemical variables

Macroalgal seasonality was studied monthly in a second-order stream in the north-west of São Paulo State, S.E. Brazil. Seasonal variation was based on frequency and percentage cover. Seven species were found during the study period, three of which (Chantransia stage of Sirodotia delicatula, Homoeothrix juliana and Klebsormidium subtile) were encountered throughout the year and showed well-defined seasonal patterns as well as the highest value of frequency and percentage cover. Chantransia and H. juliana dominated in summer and fall, while for K. subtile winter was the most favourable period. The remaining species (Oscillatoria agardhii, Microcoleus subtorulosus, Oedogonium sp. and Chaetophora elegans) had no clear seasonal pattern, in addition to their low values of frequency and percentage cover. Individually, K. subtile correlated with higher number of physical and chemical variables (oxygen, pH, precipitation, temperature, daylength, conductance and turbidity) than Chantransia and H. juliana (discharge and depth). Principal component analyses revealed that no single variable was responsible for the macroalgal seasonal dynamics. The variables most closely related to seasonal variation of the macroalgal community were daylength, precipitation, discharge, turbidity and dissolved oxygen. Precipitation and flow were suggested as key factors in determining seasonality of the macroalgae.     

Diel foraging in relation to available prey in an Adirondack Mountain stream fish community

The diets of the fish community of Trucka Brook, a small stream located in the central Adirondack Mountains in northern New York, were examined in relation to the bottom fauna and invertebrate drift. Measures of overlap were calculated between the diets of each fish species examined, brook trout (Salvelinus fontinalis), blacknose dace (Rhinichthys atratulus), creek chub (Semotilus atromaculatus) and pearl dace (Semotilus margarita). Overlap was also examined between the fish diets and bottom and drift samples. Blacknose dace, pearl dace and brook trout had the most similar diets which were closely associated with the benthos. Creek chub had the most distinctive diets which did not compare well with any other fish species during either diurnal or nocturnal periods. The mayfly nymph Litobranchia recurvata was the most abundant bottom invertebrate and was the major prey of benthic feeding fishes. The invertebrate drift did not compare favorably with any of the fishes' diets because of the predominance of large cased limnephilid larvae (primarily Psychoglypha sp.) which were not readily consumed by fish.     

Does rapid glacial recession affect feeding habits of alpine stream insects?

1. Glacial retreat, accompanied by shifts in riparian vegetation and glacier meltwater inputs, alters the energy supply and trophic structure of alpine stream food webs. Our goal in this study was to enhance understanding of dietary niches of macroinvertebrates inhabiting different alpine streams with contrasting glacial and non‐glacial (groundwater, precipitation, snowmelt) water inputs in conjunction with seasonal and habitat‐specific variation in basal resource availability.
2. We measured a range of stream physico‐chemical attributes as well as carbon and nitrogen isotopes (δ¹³C, δ¹⁵N) of macroinvertebrates and primary food sources at seven sites across seasons within a Swiss glaciated catchment (Val Roseg) undergoing rapid glacial retreat (1–2 km between 1997 and 2014). Sampling sites corresponded to streams used in a previous (1997/1998) study within the same alpine catchment.
3. Physico‐chemical attributes showed wide variation in environmental conditions across streams and seasons. Significant correlation among physico‐chemical proxies of glacier meltwater (phosphate‐P, total inorganic carbon, conductivity, turbidity) and macroinvertebrate δ¹³C, δ¹⁵N, and size‐corrected standard ellipse area (a proxy for feeding niche width) values showed that the extent of glacial water input shapes the energy base among alpine streams. Feeding niche differences among common alpine stream insect taxa (Chironomidae, Baetidae, Heptageniidae) were not significant, indicating that these organisms probably are plastic in feeding behaviour, opportunistically relying on food resources available in a particular stream and season.
4. Seasonal trends in macroinvertebrate δ¹³C largely followed patterns in periphyton δ¹³C values, indicating that autochthonous resources were the main consumer energy source within the stream network, as shown previously. The overall range in macroinvertebrate δ¹³C (?33.5 to ?18.4‰) and δ¹⁵N (?6.9 to 6.7‰) values also corresponded to values measured in the previous study, suggesting that macroinvertebrates altered diets in line with changes in environmental conditions and food resources during a period of rapid glacial retreat. Our results suggest that environmental changes brought on by rapid glacial retreat have not yet caused a profound change in the trophic structure within these fluvial networks.