Hyporheic Invertebrates Research Articles

Reply to comment by James W. Roy and Serban Danielescu on “Assessing invertebrate assemblages in the subsurface zone of stream sediments (0–15 cm deep) using a hyporheic sampler”

Among the techniques available for sampling invertebrates in the hyporheic zone, the methods based on pumping (Bilge or Bou-Rouch types) are still by far the most practical and most frequently used. Thus, it is important to understand as much as possible and to visualize more clearly what happens during water uptake in the alluvium, from both physical and biological points of view. However, despite the extensive method testing, many issues and methodological uncertainties still remain. Consequently, it is crucial to discuss these issues, but inevitably with an approach supported by hydrological sciences. The comment by Roy and Danielescu [2014] is very interesting because it provides a graphical and modeled representation of hydrological processes and water flow circulation patterns occurring within the sediments of a gravel bed stream during a Bou-Rouch pumping. To our knowledge, this is the first time since 1967, the date of publication of this method [Bou and Rouch, 1967; Bou, 1974], that so formal and precise hydrologic representations are given. As pointed out in our article, obtaining hyporheic quantitative samples remains a difficult task. This problem increases when sampling living organisms, among other things, because of an additional uncontrolled dimension related to organism behavior, including intra and interspecific variability. The second comment by Roy and Danielescu [2014] relates to the spatial variation of pore water velocity during pumping. The authors provide a vectored representation of such spatial variation and indicate that it might lead to a spatial variation in the extraction capacity of invertebrates by the pump, which is sensible. They conclude that the volume of water in which organisms undergo sufficient shear stress to be drawn in is reduced to the immediate vicinity of the well screen. This phenomenon is relatively well known and is reflected, among other things, by the sharp decrease of the abundance of organisms collected during pumping (e.g., organisms collected in ten consecutive 1 L samples [Boulton et al., 2004] or six consecutive 10 L samples [Danielopol, 1976]), which mirrors a decreasing amount of sand drawn in time. The issues related to pumping efficiency are precisely those raised by our work, because we wanted to know what fraction of the actual density and diversity is provided by a Bou-Rouch sample. Roy and Danielescu [2014] suggest that our system does not take in the entire volume of voids isolated by the Hess cylinder, as assumed during the implementation of the sampling design. Nevertheless, the error is certainly lower than suggested by Roy and Danielescu's model, because a negligible amount of invertebrates were drawn in through the bottom. Their comment is an illustration of the need of interdisciplinary efforts to better understand the hydrological processes that occur during faunal sampling, and generally for a more integrated ecological research in hyporheic and groundwater ecology. Our article may suffer from a weak hydrological support, but it nevertheless illustrates the shortcomings of the available pumping techniques to evaluate hyporheic invertebrate density and diversity. Any improvement in the current methodology that reduces the error highlighted by Roy and Danielescu [2014] is highly desirable. In order to minimize the methodologically sampling error, we suggest to eliminate the small volume of surface water trapped during the installation of the cylinder and to fit the size of the cylinder with both the desired pumped volume and the zone of influence of the pump. Obviously, the exact adjustments should be proposed after close monitoring of the hydrological processes and by modeling the interstitial water flow inside the cylinder.

Does large woody debris affect the hyporheic ecology of a small New Zealand pasture stream?

Rehabilitation of vertical hydrological exchange in small pasture streams is expected to improve hyporheic habitat, invertebrate life and ecosystem functioning, and may be achieved by adding large woody debris (LWD). This study investigated whether hyporheic improvement within 10 to 50 cm below streambed surface is evident around existing wood structures in a small New Zealand pasture stream in the Whatawhata area near Hamilton. Samples were taken around LWD and from areas where no wood was present in the pasture and from a control stream. At the pasture stream site, where the hyporheic zone was impacted by sedimentation and suffered from low dissolved oxygen (DO) levels (on average 8.4, 4.3 and 2.4 mg L−1 at 10, 30 and 50 cm depth, respectively), LWD was not associated with a significant improvement in vertical hydrological exchange, hyporheic habitat quality or invertebrate richness. However, higher densities in hyporheic invertebrates were found where LWD was present (100 vs. 56 individuals per L of sediment), in particular Leptophlebiidae and Oligochaeta. Potential pumping effects of LWD may have been hampered by large-scale deep groundwater upwelling in this reach. We conclude that in pasture streams where sedimentation is a legacy of land clearance on unstable slopes and where low hyporheic DO concentrations prevail, wood addition may not be an effective rehabilitation tool.

Assessing invertebrate assemblages in the subsurface zone of stream sediments (0-15 cm deep) using a hyporheic sampler

[1] Quantitative comparisons between benthic and hyporheic invertebrate communities are crucial for understanding the biological functions of the hyporheic zone, such as storage, migrations, and exchanges of invertebrates with the surface stream. Such comparisons are still hampered by the use of different techniques adapted to each habitat (benthic versus hyporheic). This work combines two different techniques for sampling the upper layers of bed sediments (0–15 cm): the semiquantitative “Bou-Rouch” pump classically used to sample the hyporheic zone (>15 cm), and the quantitative Hess sampler commonly used to sample the benthic zone (≤15 cm), in order to evaluate the quantitative efficiency of the pump in this 0–15 cm zone. First, a Bou-Rouch sample (BR) was taken within the cylinder of a Hess inserted within the streambed, then a second sample (benthic complement, BC) was collected within the Hess after removing the pump, in order to catch all invertebrates not extracted with the pump. The BR samples collected on average 14.5% of the total abundance and about 50% of the actual richness. The large range of variation indicates that the combination of the two techniques is not valid for a quantitative evaluation of benthic communities. Contrary to expectations, the pump did not collect more interstitial and groundwater invertebrates and no differences in faunal composition between upstream and downstream riffle positions were observed. Our results do not question the use of the BR technique under standard conditions i.e., when sampling the hyporheic zone, but underline how it is crucial to know its quantitative limits.

Invertebrate distribution across nested geomorphic features in braided-river landscapes

AbstractRiver landscapes are increasingly viewed as a collection of nested geomorphic features, the hydrological effects of which juxtapose to create a mosaic of aquatic habitat conditions. We examined how the combined hydrological influences of stream reaches and gravel bars affect the composition of hyporheic invertebrate assemblages along the longitudinal and vertical dimensions of river landscapes. We worked in 12 braided-river valley segments of tributaries to the Rhone River, France. Valley segments were bounded downstream by geological knickpoints so that bedform-induced exchange flows beneath gravel bars and riffles were predictably embedded in exchange flows occurring at the valley-segment scale. In upstream reaches (UR) and downstream reaches (DR) of each valley segment, we collected invertebrates at the heads and tails of gravel bars in the hyporheic zone and at the upstream and downstream ends of riffles in surface channels adjacent to the bars. Patterns of vertical hydraulic gradient and spec...

Human alteration of groundwater–surface water interactions (Sagittario River, Central Italy): implication for flow regime, contaminant fate and invertebrate response

Many rivers worldwide are undergoing severe man-induced alterations which are reflected also in changes of the degree of connectivity between surface waters and groundwater. Pollution, irrigation withdrawal, alteration of freshwater flows, road construction, surface water diversion, soil erosion in agriculture, deforestation and dam building have led to some irreversible species losses and severe changes in community composition of freshwater ecosystems. Taking into account the impact of damming and flow diversion on natural river discharge, the present study is aimed at (i) evaluating the effects of anthropogenic changes on groundwater/surface water interactions; (ii) analyzing the fate of nitrogenous pollutants at the floodplain scale; and (iii) describing the overall response of invertebrate assemblages to such changes. Hydrogeological, geochemical and isotopic data revealed short- and long-term changes in hydrology, allowing the assessment of the hydrogeological setting and the evaluation of potential contamination by nitrogen compounds. Water isotopes allowed distinguishing a shallow aquifer locally fed by zenithal recharge and river losses, and a deeper aquifer/aquitard system fed by surrounding carbonate aquifers. This system was found to retain ammonium and, through the shallow aquifer, release it in surface running waters via the hyporheic zone of the riverbed. All these factors influence river ecosystem health. As many environmental drivers entered in action offering a multiple-component artificial environment, a clear relationship between river flow alteration and benthic and hyporheic invertebrate diversity was not found, being species response driven by the combination of three main stressors: ammonium pollution, man-induced changes in river morphology and altered discharge regime.

Hyporheic invertebrates as bioindicators of ecological health in temporary rivers: A meta-analysis

Worldwide, many rivers cease flow and dry either naturally or owing to human activities such as water extraction. However, even when surface water is absent, diverse assemblages of aquatic invertebrates inhabit the saturated sediments below the river bed (hyporheic zone). In the absence of surface water or flow, biota of this zone may be sampled as an alternative to surface water-based ecological assessments. The potential of hyporheic invertebrates as ecological indicators of river health, however, is largely unexplored. We analysed hyporheic taxa lists from the international literature on temporary rivers to assess compositional similarity among broad-scale regions and sampling conditions, including the presence or absence of surface waters and flow, and the regional effect of hydrological phase (dry channel, non-flowing waters, surface flow) on richness. We hypothesised that if consistent patterns were found, then effects of human disturbances in temporary rivers may be assessable using hyporheic bioindicators. Assemblages differed geographically and by climate, but hydrological phase did not have a strong effect at the global scale. However, hyporheic assemblage composition within regions varied along a gradient of higher richness during wetter phases. This indicates that within geographic regions, hyporheic responses to surface drying are predictable and, by extension, hyporheic invertebrates are potentially useful ecological indicators of temporary river health. With many rivers now experiencing, or predicted to experience, lower flows and longer dry phases owing to climate change, the development of ecological assessment methods specific to flow intermittency is a priority. We advocate expanded monitoring of hyporheic zones in temporary rivers and recommend hyporheic invertebrates as potential bioindicators to complement surface water assessments.

Benthic and hyporheic invertebrate assemblages along a gradient of increasing streambed colmation by fine sediment

Streambed colmation by fine sediment, e.g. the deposition, accumulation and storage of fines in the substrate, is a major environmental concern throughout the world. Nevertheless, the ecological effects of streambed colmation on both benthic and hyporheic invertebrate assemblages have rarely been considered simultaneously. We studied a continuum of a naturally increasing percentage of fine sediment in three temperate rivers and hypothesized that the increasing percentage of fine sediment would decrease both benthic and hyporheic invertebrate densities and diversities, and reduce the similarities between them. To test these hypotheses, we first compared heavily, moderately and lightly clogged reaches located in downwelling areas and sampled invertebrates in the benthic zone and at 3 different depths (10, 30 and 50 cm) in the hyporheic zone. Secondly, we modified the sediment grain size distribution experimentally by increasing the percentage of fine sediment and using artificial substrates. The increasing colmation halved the hyporheic taxonomic richness and reduced benthic and hyporheic densities to a third. Some taxa were found in both zones, mainly in high colmation (e.g. Baetidae) or low colmation contexts (e.g. Orthocladiinae, Cyclopoida and Harpacticoida). The dissimilarity between benthic and hyporheic fauna (only at −50 cm) was significantly higher in heavily clogged reaches than in moderately and lightly clogged ones, suggesting reduced vertical exchange of invertebrates or differential impacts between zones. The total abundance, taxonomic richness, percentage of EPT taxa and densities of most organisms observed using the artificial substrates decreased linearly with the increasing percentage of fine sediment in the experiment. Only the Ephemeroptera Caenis spp. and Heptageniidae disappeared above 30 and 50 % of fine sediment, respectively, suggesting that the response to increasing colmation are strongly taxon-specific. High amount of fine sediments within the substrate significantly decreased habitat quality for benthic and hyporheic invertebrates and thus limit the production of streams and their capacity to recover after disturbance. Moreover, the use of hyporheic invertebrates seems more relevant than benthic invertebrates to assess the effect of colmation and thus could be tested in future research as indicators.

Patch scale response of hyporheic invertebrates to fine sediment removal in two chalk rivers

Patch scale response of hyporheic invertebrates to fine sediment removal in two chalk rivers

Benthic and hyporheic invertebrate assemblages along a flow intermittence gradient: effects of duration of dry events

1. A large proportion of the total river length on Earth comprises rivers that are temporary in nature. However, the effects of periodical dry events have received far less attention from ecologists than those of floods and low flows. 2. This study concomitantly examined the effects of flow intermittence on invertebrates from the streambed surface and from a depth of 30 cm in the hyporheic zone. Invertebrates were collected during 3 years in the Albarine River, France, before and after summer dry events from 18 sites (seven were perennial) distributed along a longitudinal flow intermittence gradient. 3. I predicted benthic and hyporheic density and taxonomic richness to decrease, and assemblage composition to shift from desiccation-sensitive to desiccation-resistant taxa with increased dry event duration. Second, I predicted benthic and hyporheic assemblages from sites that dried for longer periods to be nested subsets of assemblages from sites that dried for shorter periods. Last, I predicted a convergence in benthic and hyporheic assemblage composition with increasing duration of dry events, resulting from increased vertical migration of benthic taxa into the hyporheic sediments to cope with dry events. 4. Increased dry event duration in the Albarine River led to a decrease in both benthic and hyporheic density and taxonomic richness. Invertebrate assemblage composition shifted along the gradient of increasing flow intermittence, but broad taxonomic overlap between perennial and temporary reaches and nestedness patterns indicated that these shifts were because of the loss of taxa susceptible to drying rather than selection for desiccation-resistant specialists. 5. Assemblage composition between benthic and hyporheic invertebrates diverged with increasing dry event duration, suggesting that the hyporheic zone did not act as a refuge during dry events in this river. 6. Quantitative studies on the relationships between ecology and intermittence are still rare but are needed to predict the consequences of future changes in flow intermittence. The relationships found in this study should be tested across a wide range of temporary rivers to better evaluate the generality of these findings.

Spatial and temporal variability of hyporheic invertebrate community within a stream reach of the River Bača (W Slovenia)

We studied spatio-temporal distribution of hyporheic invertebrate community at the stream-reach scale in the River Bača on three sampling occasions (January, March, May) in 2005. On each sampling occasion, invertebrates were collected from the shallow hyporheic zone (RB1; depth 30-60 cm, 3 replicates), and deeper hyporheic zone (RB2; depth 60-90 cm, 2 replicates) in the river bed, and adjacent gravel bar (GB; depth 60-90 cm, 3 replicates) using Bou-Rouch piston pump. Concurrently, temperature, conductivity and oxygen were measured in the surface water and in hyporheic water at each sampling station. Differences in hyporheic community between dates and habitats were analysed by using two-way ANOVA (dates and habitats as fixed factors) and explored by principal component analysis (PCA). Altogether, 21,657 specimens from 63 taxa were collected. Cyclopoida juveniles, Leuctra sp. (Plecoptera), Chironomidae (Diptera), Acanthocyclops vernalis (Fischer, 1853) and Diacyclops languidus (G. O. Sars, 1863) were the most abundant in the samples. Two-way ANOVA showed significant differences between habitats (RB1 and GB), but no differences between dates when using taxonomic richness as dependent variable. No differences between habitats and dates were calculated when invertebrate densities were applied. PCA of hyporheic invertebrate data showed a gradient in community composition from shallow hyporheic zone (RB1) to deeper hyporheic zone (RB2) and gravel bar (GB). The differences were most probably due to different sediment composition in the studied habitats and less frequent disturbances due to floods in deeper layers and lateral gravel bars.

Spatial distribution patterns of the hyporheic invertebrate communities in a polluted river in Romania

The purpose of this study was to examine the sensitivity, in a field situation, of the hyporheic fauna to pollution by heavy metals and also to test the use of oxidative stress enzymes produced by this fauna as a sensitive indicator of oxidative stress generated by chemical contamination. This was done by surveying the patterns of distribution, structure, and composition of hyporheic invertebrate communities in one of the most polluted rivers in Romania. Twelve permanent sampling stations with differing water qualities were established along a 180 km transect of the Aries River. Data on hyporheic invertebrate abundance and richness, chemistry of the surface and hyporheic water and interstitial suspended particles were analyzed via multifactorial analyses. In the downstream, more polluted stations, epigean species were less abundant and hyporheic communities, especially macrocrustaceans and oligochetes, became dominant. The higher levels of hyporheic invertebrate biodiversity in the moderately polluted stations compared to highly polluted, and the increase of the number of some hyporheos (especially macrocrustaceans) in the moderately polluted stations, suggested that the hyporheic fauna was more tolerant of heavy metal pollution than the surface water fauna of the area. However, the different richness and abundance of hyporheic fauna in sites of similar water chemistry suggested that additional factors, such as sediment structure are shaping the spatial distribution of hyporheic fauna. Strong correlations between superoxide dismutase (SOD) activity in pooled tissues extracts and some chemical parameters suggest that oxidative stress enzymes may prove to be sensitive indicators of chemical pollution in hyporheic zones.

The effect of in-stream gravel extraction in a pre-alpine gravel-bed river on hyporheic invertebrate community

We investigated the effect of in-stream gravel extraction in a pre-alpine gravel-bed river on hyporheic invertebrate community, together with changes in the hyporheic geomorphology, physico-chemistry and biofilm activity. Hyporheic invertebrates were collected, together with environmental data, on seven sampling occasions from June 2004 to May 2005, at two river reaches—at the site of in-stream gravel extraction and at a site 2.5 km upstream. The hyporheic samples were taken from the river bed and from the gravel bars extending laterally from the stream channel. The invertebrate community was dominated by insect larvae (occasional hyporheos), followed by meiofauna (permanent hyporheos). Stygobionts were present at low species richness and in low densities. Gravel extraction from the stream channel led to changes in the patterns of water exchange between surface and subsurface and changes in the sediment composition at the site. Immediate reductions in density and taxonomic richness of invertebrates were observed, together with changes in their community composition. The hyporheic invertebrate community in the river recovered relatively fast (in 2.5 months) by means of density and taxonomic richness, while by means of community composition invertebrates needed 5–7 months to recover. The impact of fine sediments (<0.1 mm) on biofilm activity measured through ETS activity and hyporheic invertebrate density and taxonomic richness was strongly confirmed in this study.

Invertebrate drift during in-stream gravel extraction in the River Baca , Slovenia

Spatial and temporal variation in invertebrate drift during in-stream gravel extraction in a gravel-bed river in south western Slovenia (SE Europe) was investigated. Drift samples were collected at three sites (an upstream control site and two downstream impacted sites) on the first and third days of gravel extraction. Drift measured during gravel extraction was compared to the hyporheic invertebrate community at the site of gravel extraction. Significant differences in drift were observed between the sites (ANOVA, n = 18, F = 23.29, p <0.001 for the number of individuals h -1 , and F = 13.15, p <0.001 for the number of taxa h -1 ). Two way analysis of ANOVA revealed the significance of site (p < 0.01) for number of individuals h -1 , and of site (p <0.001) and site * date interaction (p < 0.001) for taxa number h -1 . Insect larvae dominated drift at the control site, while crustaceans dominated the drift on the third day at both impacted sites. PCA of drift and hyporheic samples explained 37.8 % of the variance in data by the first two ordination axes. Drift composition was most similar to the shallow hyporheos on the third day of excavation. The study demonstrates that gravel extraction induces drifting of meiofauna which normally do not occur in the drift and that mass drift can occur up to 200 m from the site of excavation. Drift rates were much higher (approximately 30 fold) than the rates observed during increased discharge (from 2-5 fold).

Benthic and hyporheic invertebrate community responses to seasonal flow recession in a groundwater‐dominated stream

AbstractNatural hydrological variability in lotic ecosystems can include prolonged periods of flow recession. A reduction in discharge is accompanied by abiotic changes in benthic and hyporheic habitats, often including reductions in habitat availability. Whilst the benthic invertebrate community response to low flows is well documented, little research has considered how the composition of the community within the hyporheic zone is affected. We examined benthic and hyporheic invertebrate community composition during flow recession in a temperate karst stream, at sites with contrasting historic flow permanence regimes. Changes in benthic invertebrate community composition primarily reflected changes in habitat availability associated with discharge variability; in particular, the population density of the dominant amphipod, Gammarus pulex, increased as the area of submerged benthic sediments declined. Concurrent significant increases in the hyporheic abundance of G. pulex, and moderate increase in the proportion of the total G. pulex population inhabiting the hyporheic zone were recorded. It is postulated that G. pulex migrated into the hyporheic zone to reduce exposure to intensifying biological interactions in the benthic sediments. An increase in the hyporheic abundance of G. pulex was particularly pronounced at sites with historic intermittent flow, which could be attributed to downwelling stream water dominating vertical hydrologic exchange. The increase in G. pulex abundance reduced community diversity in the benthic sediments, but had no apparent detrimental effects on hyporheic invertebrate assemblages. Copyright © 2010 John Wiley &amp; Sons, Ltd.

A Framework for Analyzing Longitudinal and Temporal Variation in River Flow and Developing Flow‐Ecology Relationships1

Larned, Scott T., David B. Arscott, Jochen Schmidt, and Jan C. Diettrich, 2010. A Framework for Analyzing Longitudinal and Temporal Variation in River Flow and Developing Flow‐Ecology Relationships. Journal of the American Water Resources Association (JAWRA) 46(3):541‐553. DOI: 10.1111/j.1752‐1688.2010.00433.xAbstract: We propose a framework for analyzing longitudinal flow variation and exploring its ecological consequences in four steps: (1) generating longitudinally continuous flow estimates; (2) computing indices that describe site‐specific and longitudinal flow variation, including intermittence; (3) quantifying and visualizing longitudinal dynamics; (4) developing quantitative relationships between hydrological indices and ecological variables (flow‐ecology relationships). We give examples of each step, using data from a New Zealand river and an empirical longitudinal flow model, ELFMOD. ELFMOD uses spot‐gauging data and flow or proxy variable time series to estimate flow magnitude and state (flowing or dry) at user‐defined intervals along river sections. Analyses of flow‐ecology relationships for the New Zealand river indicated that fish and benthic and hyporheic invertebrate communities responded strongly to variation in mean annual flow permanence, flow duration, dry duration, drying frequency, inter‐flood duration, and distances to flowing reaches. To put longitudinal flow variation into a broader context and guide future research, we propose a conceptual model that combines elements of two contrasting perspectives: rivers as longitudinal continua, and rivers as patch mosaics. In this conceptual model, hydrologically complex rivers are composed of linear sequences of nested hydrological gradients, which are bordered by hydrogeomorphic discontinuities, and which collectively generate hydrological dynamics at river‐section scales.

Ecology of the hyporheic zone: origins, current knowledge and future directions

Traian Orghidan's seminal paper on the hyporheic zone was published in German in Archiv fur Hydrobiologie 50 years ago. To celebrate this anniversary, it has now been translated into English and republished in Fundamental and Applied Limnology, the successor to Archiv fur Hydrobiologie, as part of this special issue on hyporheic zone ecology. Here we examine the development and current state of knowledge of four aspects of hyporheic zone ecology first articulated by Orghidan. First, we consider the ecotonal nature of the hyporheic zone (HZ) and its relationship to the wider stream ecosystem; second, surface water and groundwater habitat interconnectivity within the hyporheic zone; third, the spatial and temporal heterogeneity of the HZ and how this may influence its function as a refugium for taxa during disturbances; and lastly interactions between hyporheic invertebrates and pore water volume, bacterial densities and particulate organic carbon. We outline the characteristics of the hyporheic zone that may determine how effective it will be as a refugium for benthic taxa during disturbances and consider the biological traits of benthic species most able to utilise the HZ as a refugium. Finally, we examine an important avenue of research that has developed since Orghidans paper reflecting significant scientific and technological advances; the role of the hyporheic zone in stream nutrient dynamics. We conclude by considering some areas where further research is likely to advance our understanding of the hyporheic zone and its interaction with the wider stream ecosystem.

Hyporheic flowpaths and interstitial invertebrates associated with stable and eroded river sections: interactions between micro- and meso-scales

Erosion of the river beds linked to human activities is currently a crucial issue. By inducing strong changes in river dynamics, this erosion alters many of the related ecological processes. The modification of the relationships between the river and its aquifer due to erosion is not really understood. The large scale consequences of erosion for the interactions between river and the underlying aquifer must be clarified, together with the small scale effects of river erosion on hyporheic flowpaths. The role of water exchange within the hyporheic zone on the distribution of interstitial invertebrates is universally recognized, but nothing is known on the potential links between riverbed erosion, the subsequent modification of water exchange at a local scale and their consequences on the distribution and biomass of hyporheic invertebrates. Two sections, stable versus eroded, were studied on the Herbasse, a third-order stream, by sampling hyporheic water and invertebrates at two depths within the substrate (−15 and −50 cm deep), upstream and downstream of ten riffles. Seven physical and chemical parameters were used to identify the hydrological flowpaths at both the riffle (up and downwelling areas) and the section scales (eroded vs stable) and to specify the level of nutrients in the hyporheic habitat. Significant differences were observed between the stable and eroded sections both in the vertical and longitudinal dimensions, with for example available oxygen decreasing with depth and along hyporheic flowpaths, and revealing more obvious differences in the eroded section gaining groundwater than in the stable section. Most of the hypogean organisms (Niphargus sp., Salentinella juberthiei, and Proasellus sp.) were most abundant at the deepest level, in the upwelling zones and the eroded section, while typical epigean taxa (Gammarus sp., Plecoptera and Ephemeroptera) were mostly present near the surface and in the stable section, suggesting that erosion processes may influence the development of hyporheic assemblages at riffle and reach scales.

Ecology and management of the hyporheic zone: stream–groundwater interactions of running waters and their floodplains

AbstractOver the last 25 y, stream ecosystem theory has expanded to include explicitly the vertical dimension of surface–groundwater linkages via the hyporheic zone and below alluvial floodplains. Hydrological exchange between the stream and hyporheic zone mediates transport of products from the biogeochemical activities within the sediments. Hot-spots of primary productivity in the surface stream often result from upwelling nutrient-rich water. Conversely, downwelling surface water supplies organic matter and dissolved O2 to hyporheic invertebrates and microbes, enhancing hyporheic productivity. Many of the papers seminal to conceptual and empirical advances in hyporheic research have been published in J-NABS, reflecting stream benthologists’ awareness of the relevance of processes and biota in the hyporheic zone. However, major research gaps remain. One is the need for further empirical data to test the predictions of several current conceptual frameworks that hypothesize conditions under which the hypo...

Low flow controls on benthic and hyporheic macroinvertebrate assemblages during supra‐seasonal drought

AbstractDespite the widely accepted importance of the hyporheic zone as a habitat for stream macroinvertebrates during floods, few data exist regarding community composition and distribution during periods of low flow or drought in perennial streams. Integrating research on hyporheic invertebrates with results from a long‐term study of a UK river provided the opportunity to examine how benthic and hyporheic macroinvertebrate communities respond to inter‐annual variability in river flow and periods of groundwater drought. Changes in the riverine macroinvertebrate community associated with low flow included a reduction in species richness and the number of individuals per sample, particularly aquatic insects. The hyporheic community was characterized by a relatively homogeneous composition during a period of severe low flow, punctuated by short‐term changes associated with variation in water temperature rather than changes in discharge. We present a conceptual model of the processes influencing benthic and hyporheic invertebrates under low‐flow conditions. Previous studies have seldom integrated these two assemblages and their interactions. The model presented highlights the potential importance of surface water and hyporheic zone linkages for riverine invertebrate communities under a range of flow conditions. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Impact of hydropeaking on hyporheic invertebrates in an Alpine stream (Trentino, Italy)

The impact of repeated hydropeaking events was assessed in the Alpine stream Noce Bianco (Trentino, NE Italy). Three stations were selected, one upstream and two at 0.25 km and 6 km downstream from a hydropower plant which causes 7-fold discharge increases. We collected hyporheic invertebrates for two years. Taxa diversity and abundance were reduced in the impacted sites, especially affecting the stygobites, which were significantly less abundant at the impacted sites, whereas stygoxene invertebrates increased exponentially. Repeated hydropeaking events alter the physical-chemical characteristics of the hyporheic habitat, resulting in the recorded faunistic pattern. The deposition of the fine sediment transported by the turbinated water downstream of the power plant and the absence of natural peak floods which remove fine sediments, probably cause a reduction of the interstitial space interstitial habitat available to stygobitic taxa. Surface water natural thermal regime is altered by the hypolimnetic discharges, and such alterations propagate into the hyporheic, affecting the stenothermic taxa. Some benthic taxa used the hyporheic habitat as a refuge to avoid catastrophic drift during hydropower production operation. The main trophic roles represented in the hyporheic assemblages do not support an important role for biological interactions such as predation in determining the fine-scale patchiness of the hyporheos.