Hyporheic Invertebrate Communities Research Articles

Invertebrate and Microbial Response to Hyporheic Restoration of an Urban Stream

All cities face complex challenges managing urban stormwater while also protecting urban water bodies. Green stormwater infrastructure and process-based restoration offer alternative strategies that prioritize watershed connectivity. We report on a new urban floodplain restoration technique being tested in the City of Seattle, USA: an engineered hyporheic zone. The hyporheic zone has long been an overlooked component in floodplain restoration. Yet this subsurface area offers enormous potential for stormwater amelioration and is a critical component of healthy streams. From 2014 to 2017, we measured hyporheic temperature, nutrients, and microbial and invertebrate communities at three paired stream reaches with and without hyporheic restoration. At two of the three pairs, water temperature was significantly lower at the restored reach, while dissolved organic carbon and microbial metabolism were higher. Hyporheic invertebrate density and taxa richness were significantly higher across all three restored reaches. These are some of the first quantified responses of hyporheic biological communities to restoration. Our results complement earlier reports of enhanced hydrologic and chemical functioning of the engineered hyporheic zone. Together, this research demonstrates that incorporation of hyporheic design elements in floodplain restoration can enhance temperature moderation, habitat diversity, contaminant filtration, and the biological health of urban streams.

In this Issue

i DOI: https://doi.org/10.3318/BIOE.2019.05 Biology and Environment: Proceedings of the Royal Irish Academy,Vol. 119, No. 1, i–ii (2019). © Royal Irish Academy Cite as follows: Osborne, B. 2019 Editorial / In this Issue. Biology and Environment: Proceedings of the Royal Irish Academy 2019. DOI: 10.33318/ BIOE.2019.05 EDITORIAL Bruce Osborne Despite the challenging times we live in with an­ ever-increasing number of journals plying for ­ papers in the biological and environmental areas,I am pleased to say that Biology and Environment is maintaining our impact factor above 0.65 (0.676). Whilst this is the good news,maintaining or even increasing our impact factor in the future is a significant challenge so we need to continue to ensure that we receive high-quality submissions.As editor a particular onus is placed on me, together with the other members of the editorial board, to ensure that this happens. We are, however, always open to new ideas and new publication initiatives that will increase the journal’s impact and readership and I would encourage, in particular, suggestions for new Praeger Reviews and special issues. In terms of new initiatives this issue contains the first of what I hope will be a series of so-called ‘data papers’.This initiative is based on the increasing body of numerical information that is often not suitable for more conventional publications as it is not specifically hypothesis-driven research. Nevertheless , well-documented metadata is an important and often essential resource for informing current and future research as well as providing the basis for wider collaborative initiatives. Moreover, these publications provide a way of recognising all those who contributed to the collection, management and curation of the data sets. I hope, therefore, that this is a publication opportunity that a number of you can take advantage of in the future. I would like finally to recognise all the Royal Irish Academy staff, editorial board members and reviewers who have contributed to Biology and Environment over the past year. Bruce Osborne IN THIS ISSUE Limestone lake crusts Limestone lakes are often characterised by a benthos consisting of charophyte algae and a microbial crust comprising of a range of microbes intermixed with inorganic minerals.Whilst the more visible charophyte beds have received considerable attention much less is known about the functional significance and formation of the microbial crusts. Doddy et al., in this issue point out that although these crusts are sometimes considered as largely inert inorganic minerals,they are complex substrates containing a diverse assemblage of living microorganisms. Both filamentous and coccoid cyanobacteria are present as are chlorophytes and diatoms that reflect, in part, the organisms present in the water column.As expected the crusts contain a high proportion of mineral particles that may be cemented together through the actions of filamentous cyanobacteria.In terms of the controls over crust formation Doddy et al. provide evidence that this is related to P availability, with crust deterioration evident at high water column P concentrations . Crusts may also act as a significant sink for P so that conservation of these habitats should consider any effects that impact on their functionality, including increased turbidity and modifications in water chemistry. Importantly, as improvements in water column quality may not be synonymous with improvements in the status of the microbial crusts, specific conservation measures are likely to be required that are targeted directly at the benthic community. Cattle impacts on the hyporheic zone The word hyporheic, from the Greek hypo (below) and rheos (flow), was first coined by the Romanian hydrobiologist Traian Orghidan in 1955 to denote the area below the stream bed where mixing of surface and ground water occurs.This is an important interface often characterised by a unique assemblage of organisms that control the exchange of organic material, water and nutrients between surface and ground water bodies. Importantly this zone can be strongly impacted by agricultural activity, as­ O’Sullivan et al., in this issue, show.The authors detail how cattle access to the shallow areas associated with headwater streams can increase downstream sediment flow and negatively impact on hyporheic invertebrate communities. In some cases this also resulted in a reduction...

In this Issue

i DOI: https://doi.org/10.3318/BIOE.2019.05 Biology and Environment: Proceedings of the Royal Irish Academy,Vol. 119, No. 1, i–ii (2019). © Royal Irish Academy Cite as follows: Osborne, B. 2019 Editorial / In this Issue. Biology and Environment: Proceedings of the Royal Irish Academy 2019. DOI: 10.33318/ BIOE.2019.05 EDITORIAL Bruce Osborne Despite the challenging times we live in with an­ ever-increasing number of journals plying for ­ papers in the biological and environmental areas,I am pleased to say that Biology and Environment is maintaining our impact factor above 0.65 (0.676). Whilst this is the good news,maintaining or even increasing our impact factor in the future is a significant challenge so we need to continue to ensure that we receive high-quality submissions.As editor a particular onus is placed on me, together with the other members of the editorial board, to ensure that this happens. We are, however, always open to new ideas and new publication initiatives that will increase the journal’s impact and readership and I would encourage, in particular, suggestions for new Praeger Reviews and special issues. In terms of new initiatives this issue contains the first of what I hope will be a series of so-called ‘data papers’.This initiative is based on the increasing body of numerical information that is often not suitable for more conventional publications as it is not specifically hypothesis-driven research. Nevertheless , well-documented metadata is an important and often essential resource for informing current and future research as well as providing the basis for wider collaborative initiatives. Moreover, these publications provide a way of recognising all those who contributed to the collection, management and curation of the data sets. I hope, therefore, that this is a publication opportunity that a number of you can take advantage of in the future. I would like finally to recognise all the Royal Irish Academy staff, editorial board members and reviewers who have contributed to Biology and Environment over the past year. Bruce Osborne IN THIS ISSUE Limestone lake crusts Limestone lakes are often characterised by a benthos consisting of charophyte algae and a microbial crust comprising of a range of microbes intermixed with inorganic minerals.Whilst the more visible charophyte beds have received considerable attention much less is known about the functional significance and formation of the microbial crusts. Doddy et al., in this issue point out that although these crusts are sometimes considered as largely inert inorganic minerals,they are complex substrates containing a diverse assemblage of living microorganisms. Both filamentous and coccoid cyanobacteria are present as are chlorophytes and diatoms that reflect, in part, the organisms present in the water column.As expected the crusts contain a high proportion of mineral particles that may be cemented together through the actions of filamentous cyanobacteria.In terms of the controls over crust formation Doddy et al. provide evidence that this is related to P availability, with crust deterioration evident at high water column P concentrations . Crusts may also act as a significant sink for P so that conservation of these habitats should consider any effects that impact on their functionality, including increased turbidity and modifications in water chemistry. Importantly, as improvements in water column quality may not be synonymous with improvements in the status of the microbial crusts, specific conservation measures are likely to be required that are targeted directly at the benthic community. Cattle impacts on the hyporheic zone The word hyporheic, from the Greek hypo (below) and rheos (flow), was first coined by the Romanian hydrobiologist Traian Orghidan in 1955 to denote the area below the stream bed where mixing of surface and ground water occurs.This is an important interface often characterised by a unique assemblage of organisms that control the exchange of organic material, water and nutrients between surface and ground water bodies. Importantly this zone can be strongly impacted by agricultural activity, as­ O’Sullivan et al., in this issue, show.The authors detail how cattle access to the shallow areas associated with headwater streams can increase downstream sediment flow and negatively impact on hyporheic invertebrate communities. In some cases this also resulted in a reduction...

The impacts of cattle access to headwater streams on hyporheic zones

The hyporheic zone is an important ecotone occupying the interface between surface and ground water bodies, providing a range of important ecosystem services such as biochemical cycling, temperature regulation and downstream flood attenuation. Despite its importance in freshwater ecosystems in terms of services provided, the hyporheic zone has often been overlooked as a research topic. This study assessed the impact of cattle access to headwater streams on hyporheic zone parameters. The results indicate increases in levels of interstitial, hyporheic fine sediment downstream of cattle access points and the potential for this to negatively affect hyporheic invertebrate communities. Invertebrate community composition changes were observed at some sites with changes representing a shift to less diverse communities of smaller bodied invertebrates. The results presented here should help inform water resources managers and encourage them to consider the hyporheic zone as a part of an integrated freshwater ecosystem.

The impacts of cattle access to headwater streams on hyporheic zones

The hyporheic zone is an important ecotone occupying the interface between surface and ground water bodies, providing a range of important ecosystem services such as biochemical cycling, temperature regulation and downstream flood attenuation. Despite its importance in freshwater ecosystems in terms of services provided, the hyporheic zone has often been overlooked as a research topic. This study assessed the impact of cattle access to headwater streams on hyporheic zone parameters. The results indicate increases in levels of interstitial, hyporheic fine sediment downstream of cattle access points and the potential for this to negatively affect hyporheic invertebrate communities. Invertebrate community composition changes were observed at some sites with changes representing a shift to less diverse communities of smaller bodied invertebrates. The results presented here should help inform water resources managers and encourage them to consider the hyporheic zone as a part of an integrated freshwater ecosystem.

Helophyte impacts on the response of hyporheic invertebrate communities to inundation events in intermittent streams

AbstractThe effects of experimental inundation on invertebrate communities in artificial flumes fed with treated wastewater were investigated. Flumes, designed to simulate intermittent river conditions, were planted with 3 species of helophytes widely used in river restoration around the water‐stressed regions of Europe. Different species of vegetation had different capabilities to reduce the invertebrate's negative reaction to inundation, related mostly to rhizosphere density. Of the 3 helophyte species tested, only 1, Lysimachia vulgaris, showed significant capabilities to reduce invertebrate negative reaction on inundation. Species richness of invertebrates before and after the inundation did not change in any of the flumes, whereas species density significantly declined in all flumes except one planted with L. vulgaris. This helophyte species was associated with high densities of the Culicidae larvae (common mosquitos), which has severe implications for river restoration and vector management in the region. This study indicates that the selection and establishment of different helophyte species will impact invertebrate communities in restored streams, especially streams experiencing variable inundation conditions.

The influence of water quality on hyporheic invertebrate communities in agricultural catchments

Despite knowing that agricultural practices affect river ecosystems, studies on water quality and associated hyporheic invertebrate communities are rare. Yet such knowledge is essential for sustainable use of agricultural and water resources. This study, carried out in the agricultural region of south-eastern Ireland in Spring 2007, examined the effect of water pollution on hyporheic fauna. Six river sites of known water quality were assigned to two treatments, namely, clean and polluted rivers. Two hyporheic habitats, below the wetted channel (hyporheic substream) and below the exposed gravel bank (parafluvial), were sampled within each treatment. Total invertebrate densities and richness, crustacean densities and richness, and densities of Ephemeroptera, Plecoptera and Trichoptera (EPT) were significantly reduced in polluted hyporheic and parafluvial habitats. A higher recorded concentration of nitrate in the polluted hyporheic substream habitats was a significant factor in determining the invertebrate assemblages, with reductions in total and crustacean densities, and EPT richness. Similarly, invertebrate density and richness were reduced in polluted parafluvial habitats, likely being related to agricultural intensity, management practices and reduced riparian buffering. This study highlights the direct effects of agricultural practices on the invertebrate communities of hyporheic habitats and emphasises the need for holistic management and conservation measures to ensure future protection.

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.

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.

Hyporheic invertebrate community composition in streams of varying salinity in south‐western Australia: diversity peaks at intermediate thresholds

AbstractMany streams of southwestern Australia have become secondarily saline through land clearance and other human activities in their catchments. Elevated salinities impact on aquatic biota and ecological processes of surface streams but little is known of the effects on the diversity and community composition of hyporheic (subsurface) invertebrates occupying the saturated sediments where surface and groundwaters exchange. We hypothesized that biodiversity of hyporheic invertebrates would decline with increasing salinity, especially where saline groundwater upwelled into the surface stream. We also predicted changes in community composition associated with salinity and direction of vertical hydrological exchange. Water and hyporheic invertebrates were sampled from downwelling and upwelling zones of 13 streams in southwestern Australia ranging in median surface water salinity from 0.27 to 17.86 g L−1. Overall, taxa richness of hyporheic invertebrates was uncorrelated with salinity but, surprisingly, correlated positively with the salinity of upwelling water. However, when the sites were divided into ‘fresh’ (&lt;3 g L−1) and ‘mesosaline’ (&gt;3 g L−1) groups, this relationship became non‐significant. Instead, taxa richness and total abundance were correlated positively with salinity of downwelling water in fresh sites and negatively in mesosaline sites, resulting in a peak in richness at intermediate salinities. Community composition was unrelated to direction of hydrological exchange but was strongly associated with hyporheic salinity. Hyporheic assemblages of ‘fresh’ rivers were typified by harpacticoid copepods and candoniid ostracods, whereas the amphipod Austrochiltonia and several dipteran groups were more common below ‘mesosaline’ rivers. Although many hyporheic taxa collected in this study apparently have broad tolerances to salinity, secondary salinization due to human activities potentially changed community composition, possibly altering rates of ecological processes such as organic matter breakdown occurring within the sediments of streams undergoing salinization. Copyright © 2007 John Wiley &amp; Sons, Ltd.

The response of hyporheic invertebrate communities to a large flood in the Hunter River, New South Wales

Previous studies on recovery in hyporheic communities have found that communities rapidly return to pre-disturbance levels. However, most of these studies have concentrated on small floods or ones with short return periods. I studied the impact of a large 1 in 6 year flood on the hyporheic community at 2 sites in the Hunter River, a large coastal river in New South Wales with a mean daily flow of 15 m3 s−1. The flood peaked at 1270 m3 s−1 and afterwards invertebrate densities at the 2 sites were 83 and 67% less than they were before. Recovery to pre-flood densities was slow but was aided by increases in the oligochaete and cyclopoid populations. At Site 1, there was a boom in oligochaete and cyclopoid numbers 61 d after the flood, but the communities resumed their pre-flood densities by Day 139. Recovery at Site 2 took 139 d. Most groundwater taxa (stygobites) living in the hyporheic zone did not recover from the disturbance when compared to non-stygobites. Apart from Microturbellaria and the harpacticoid Parastenocaris sp., numbers of all stygobite taxa continued to decline after the flood, becoming absent after 61 d. The poor recovery of stygobites is probably due to their adaptations for survival in the relatively stable groundwater environment. This study shows that hyporheic communities are sensitive to large bed-moving floods and supports the hypothesis that ecotonal species with a strong affinity to one ecosystem can be poor at recovering from disturbances that occur in an adjacent ecosystem.

Abiotic features and macroinvertebrate colonization of the hyporheic zones of two tributaries of the river Elbe (Germany)

Whole-ecosystem experiments may reach statistical pertinence when reference and treatment sites are compared. Therefore at least two similar systems must be found. To this aim we tried to answer the question if the hyporheic zones of both streams have similar features. We postulated that both streams would be unsuitable for a comparison in an ecosystem experiment if the structure of their hyporheic invertebrate communities differs significantly. Although pH, electrical conductivity and nitrate concentration differed in the surface water, variability of all chemical criteria studied in the hyporheic zones was much lower between the two streams compared to the variability within each stream. Thus the structure of both hyporheic invertebrate communities did not differ significantly. Because of this uniformity both streams are regarded to be suitable for a comparison in a whole-ecosystem experiment.

Influence of hydrologic exchange patterns on water chemistry and hyporheic invertebrate communities in three gravel‐bed rivers

The influence of hydraulic exchange patterns on hyporheic water chemistry and invertebrate community composition was measured in three gravel‐bed rivers of southern Hawke's Bay, North Island, New Zealand. Based on patterns reported overseas we predict that down‐welling waters will be similar to surface waters in chemical characteristics and epigean animals will be more common in down‐welling waters than in up‐wellings, which would have a different chemical signature to the surface waters and a fauna dominated by hypogean invertebrates. Conductivity, pH, and temperature of hyporheic water were least like those of surface waters at up‐wellings in the groundwater‐fed Makaretu River. Only 6% of the invertebrate fauna of these up‐wellings comprised epigean animals. In contrast, in the groundwater‐recharging Tukituki and Waipawa Rivers, hyporheic water chemistry was similar to that of surface water in down‐wellings and 40% of the community comprised epigean animals by abundance. Significant increases (P < 0.05) in species diversity and taxonomic richness was also identified in down‐welling zones compared with up‐wellings. Species diversity and taxonomic richness were lowest in up‐wellings in the Makaretu where hypogean animals dominated the hyporheic fauna. Species diversity and taxonomic richness were higher in down‐wellings than up‐wellings because more epigean taxa were present.

Relationships between metals and hyporheic invertebrate community structure in a river recovering from metals contamination

Biota and chemistry from hyporheic samplers were used to describe environmental changes, after treatment of mine drainage, in the shallow hyporheic zone in the upper Arkansas River, Colorado, U.S.A. Samples were collected (1992–1997) from above and below the mine drainage source, and further downstream where a historically cleaner tributary enters the system. Hyporheic metal concentrations were high during spring runoff at the impacted site even after initiation of treatment, but declined after several years. Correspondence analysis and increased invertebrate taxa richness suggested that hyporheic macroinvertebrates were recovering at the previously impacted site. Differences in substrate between sites and high water flows in 1995 also appeared to affect hyporheic communities. High taxa richness and abundance, taxa unique from those found at the surface, and high concentrations of metals found in the shallow hyporheic zone suggests that sampling this zone is important for monitoring recovery of polluted streams.

Comparison of Channel and Hyporheic Invertebrate Communities in a Southwestern USA Desert Stream

ABSTRACT We collected invertebrates seasonally from the channel surface and hyporheic zone of a perennial desert stream in central Arizona, U.S.A. Channel collections were made with a Hess sampler and hyporheic collections were taken with a vacuum bilge pump and sand-point probe. Diptera, Plecoptera, Nematoda and Cyclopoida comprised 86% of total annual abundance in the hyporheic zone, while Diptera and Trichoptera made up 85% of the total annual abundance in the channel. Pot samplers with two substratum sizes and chamber depths were also buried in the channel during the summer for comparison with Hess and sand-point probe collections. Densities of invertebrates in the channel surface were higher (3,400 animals/m2) than those of subchannel pots (528 animals/m2); however, pots collected 71 animals/L compared to 1.3 animals/L for sand-point probe collections with no significant difference (p >0.20) in selection for substratum size and depth. Hyporheic communities may be restricted in arid biomes and/or in r...