Assessment of Littoral Benthic Invertebrate Communities at the Land–Water Interface in Lakes Recovering from Severe Acid- and Metal-Damage

Benthic invertebrate communities within confluence sites, or areas of sediment deposition, are shaped by the input of catchment products including coarse woody debris, organic and inorganic particulates, and contaminants, but these sites also appear to be potential “hotspots” where recolonization of severely damaged ecosystems begins. Two species of leaf packs and a sweep netting technique were used to assess benthic invertebrate communities across a gradient of 14 confluence sites in 3 recovering lakes near the copper and nickel smelters in Sudbury, Canada. Environmental variables including delta habitat composition, delta area and length, and composition of deposited materials were used to detect spatial patterns in littoral benthic invertebrate communities. Benthic invertebrate community relationships with water chemistry were also assessed. Partial redundancy analysis (pRDA) showed that all sampling methods detected similar gradients of increasing invertebrate community richness and diversity as area and length of the sediment delta and the surface organic matter abundance increased. Two-way nested ANOVAs showed significant differences (p < .05) in taxa richness and diversity metrics among sites. Of the three methods, the benthic invertebrate community measurements from the birch leaf packs provided the strongest correlations with measures of organic matter inputs or habitat characteristics of the confluence zones. These correlations suggest that tree planting in riparian areas, or organic matter or macrophyte additions to littoral zones, may enhance littoral benthic invertebrate richness and diversity in acid and metal damaged lakes.     

Habitat‐specific invertebrate responses to hydrological variability,anthropogenic flow alterations,and hydraulic conditions

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Recolonisation patterns of benthic invertebrates: a field investigation of restored former sewage channels

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Experimental wood addition in streams: effects on organic matter storage and breakdown

1. Channel complexity affects the physical structure, biotic communities and functioning of stream ecosystems. Large wood (LW) is a key element in the creation and maintenance of physically complex stream channels in forested areas. 2. In an attempt to enhance stream habitat quality and ecosystem functioning and to reduce inputs of organic matter to a downstream reservoir, LW was experimentally introduced into four mountain streams in the Basque Country (northern Spain), ranging in channel width from 3 to 13 m. Following a before–after/control–impact (BACI) design, streams were monitored during 1 year prior to wood addition and during 2 years after addition in one control and one experimental reach per stream. 3. Areal cover of benthic organic matter in the entire channel was measured from regular transects and the mass of stored organic matter from random Surber samples. Breakdown of organic matter was assessed in litter bag experiments performed with black alder leaves. When 50% of the initial mass in the bags remained, invertebrates associated with leaf bags were collected. 4. Wood placement produced a 2‐ to 70‐fold increase in the storage of organic matter, especially in thick deposits upstream from wood jams, with values in excess of 2 kg AFDM per m² in the small streams. The accumulation of organic matter produced by wood introduction decreased with increasing stream size. 5. Despite the large increase in the availability of organic matter, litter breakdown rates were unaffected by the experimental reaches, suggesting large increases in the total amount of organic matter consumed at the reach scale. 6. Numbers of invertebrates and shredders per gram of leaf litter did not respond to wood addition. Average body mass of invertebrates associated with leaf litter showed a non‐significant decreasing trend, which might reflect increased recruitment. 7. Although the effects of wood addition can depend on wood stability and stream size, adding LW to restore channel complexity can improve environmental conditions for invertebrate communities and affect stream ecosystem functioning, enhancing the efficiency to use organic matter inputs on a reach scale.     

Combined stable‐isotope and fatty‐acid analyses demonstrate that large wood increases the autochthonous trophic base of a macroinvertebrate assemblage

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Invertebrate hydraulic preferences and predicted impacts of changes in discharge in a large river

• 1 Instream habitat models are attractive tools for assessing the impacts of flow restoration on aquatic organisms, but have been rarely used for invertebrates due to the lack of knowledge of their hydraulic preferences.
• 2 In this study, we provide quantitative models of the hydraulic preferences for 66 invertebrate taxa found in the Upper Rhône River (France), and combine these preferences with a statistical habitat model (FSTress) to predict the effects of minimum flow restoration on invertebrate abundances in two bypassed sections of the river.
• 3 Many taxa show marked preferences for particular hydraulic conditions. Average preferred hydraulic conditions were significantly related to those observed in smaller streams (R² = 0.37).
• 4 Our model predicted that habitat values of 27 taxa should be enhanced by restoration operations, but also predicted a decrease of habitat values in the main channel for 12 limnophilic taxa. However, these taxa are expected to maintain populations by finding refuges in restored cut‐off channels and overall invertebrate diversity is predicted to increase in the two bypassed sections studied here.

     

In the mood for wood-habitat specific colonization patterns of benthic invertebrate communities along the longitudinal gradient of an Austrian river

Instream large wood (LW) constitutes an indispensable element of natural river ecosystems. It affects local hydraulics, morphology, nutrient budget, overall habitat complexity, and dynamics. Despite numerous studies about LW as a habitat for benthic communities, information on the varying importance along the longitudinal gradient of a river is lacking. The focus of this study is therefore to investigate general differences between lithal and xylal colonizers and to further investigate trends along the river course. We analyzed lithal and xylal communities at ten sites along the medium-sized Lafnitz River in Southeast Austria. Our results significantly show (1) a general differentiation between lithal and xylal communities, (2) an increasing distinction of the lithal and xylal fauna along the longitudinal gradient of the river, and (3) a distinct correlation between the distance from source and the number of exclusive xylal and nowadays predominantly rare taxa. The presence of LW is therefore directly linked to higher aquatic biodiversity compared to rocky substrates and presents a unique element for river restoration, especially in lower river sections.     

Interim Responses of Benthic and Snag‐Dwelling Macroinvertebrates to Reestablished Flow and Habitat Structure in the Kissimmee River,Florida, U.S.A.

A critical component in the effort to restore the Kissimmee River ecosystem is the reestablishment of an aquatic invertebrate community typical of free‐flowing rivers of the southeastern United States. This article evaluates early responses of benthic and snag‐dwelling macroinvertebrates to restoration of flow and habitat structure following Phase I construction (interim period) of the Kissimmee River Restoration Project. Replicate benthic and snag samples were collected from remnant river channels in Pool A (Control site), and Pool C, the site of the first phase of restoration (Impact site). Samples were collected quarterly for 2 years prior to construction (baseline) and monthly or quarterly for 3 years following Phase I construction and restoration of flow. Baseline benthic data indicate a community dominated by taxa tolerant of organic pollution and low levels of dissolved oxygen, including the dipterans Chaoborus americanus (Chaoboridae) and the Chironomus/Goeldichironomus group (Chironomidae). Baseline snag data indicate a community dominated by gathering‐collectors, shredders, and scrapers. Passive filtering‐collector invertebrates were rare. Following restoration of flow, benthic invertebrate communities are numerically dominated by lotic taxa, including bivalves and sand‐dwelling chironomids (e.g. Polypedilum spp., Cryptochironomus spp., and Tanytarsini). Snags within the Phase I area support an invertebrate community dominated by passive filtering‐collectors including Rheotanytarsus spp. (Chironomidae) and Cheumatopsyche spp. (Hydropsychidae). Results indicate that restoration of flow has resulted in ecologically significant changes to the river habitat template not observed in Pool A. Observed shifts in benthic and snag macroinvertebrate community structure support previously developed hypotheses for macroinvertebrate responses to hydrologic restoration.     

The relation between invertebrate drift and two primary controls,discharge and benthic densities,in a large regulated river

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The lentic and lotic characteristics of habitats determine the distribution of benthic macroinvertebrates in Mediterranean rivers

1. The importance of flow‐related factors to benthic organisms, as well as the role of habitat conditions in shaping aquatic communities during low‐flow periods, have been recognised. Despite this, the preferences of macroinvertebrates to the ratio of lentic to lotic habitats at the reach scale have not been accurately quantified in most instances.
2. Aquatic invertebrates and habitat features in a range of temporary rivers in Sardinia were investigated. The investigation focused on the flow‐related characteristics that contribute to defining the lentic–lotic condition of the river reaches. The relation of habitat features to benthic taxa distributions was assessed using multidimensional scaling. The main aim of the paper was to quantify the responses of taxa to the different lentic and lotic habitat conditions by applying hierarchical logistic regressions. Finally, taxon optima were aligned along the lentic–lotic gradient and the responses of different taxonomic groups compared.
3. Unbroken waves and imperceptible flow were correlated with benthic taxa variability, suggesting local hydraulics and turbulence have a major role in regulating community composition. The overall lentic–lotic character of the river reaches was also clearly related to the benthic taxa distribution. More than 80% of taxa were significantly related to the lentic–lotic gradient, and an asymmetrical response curve was the predominant model.
4. Benthic groups showed taxon optima clustered in different ranges of the lentic–lotic gradient. Odonata, Coleoptera, Hemiptera, and Mollusca preferred clearly lentic conditions. Diptera mainly ranged on the lotic side of the gradient, while Trichoptera were relatively uniformly distributed across the gradient. Ephemeroptera taxa clustered in intermediate lentic–lotic conditions, with two species preferring extremely lentic habitats. In general, optima converged at intermediate and extremely lentic conditions, presumably due, respectively, to the coexistence of different lentic and lotic features and to the highly diverse environmental characteristics under extremely lentic situations.
5. These results support the conclusion that dissimilar ecological factors act on benthic taxa along the lentic–lotic range and species favouring different lentic–lotic conditions are subjected to pressures of different nature. This should not be ignored when defining species preferences and studying community structure or relationships between species in Mediterranean rivers, which cyclically vary their habitat composition. In addition, the uneven distribution of optima of different groups along the lentic–lotic gradient might affect macroinvertebrate metrics when assessing ecological status or establishing reference conditions under variable climatic conditions.

     

Enhanced invertebrate prey production following estuarine restoration supports foraging for multiple species of juvenile salmonids (Oncorhynchus spp.)

Estuaries provide crucial foraging resources and nursery habitat for threatened populations of anadromous salmon. As such, there has been a global undertaking to restore habitat and tidal processes in modified estuaries. The foraging capacity of these ecosystems to support various species of out‐migrating juvenile salmon can be quantified by monitoring benthic, terrestrial, and pelagic invertebrate prey communities. Here, we present notable trends in the availability of invertebrate prey at several sites within a restoring large river delta in Puget Sound, Washington, U.S.A. Three years after the system was returned to tidal influence, we observed substantial additions to amphipod, copepod, and cumacean abundances in newly accessible marsh channels (from 0 to roughly 5,000–75,000 individuals/m²). In the restoration area, terrestrial invertebrate colonization was dependent upon vegetative cover, with dipteran and hymenopteran biomass increasing 3‐fold between 1 and 3 years post‐restoration. While the overall biodiversity within the restoration area was lower than in the reference marsh, estimated biomass was comparable to or greater than that found within the other study sites. This additional prey biomass likely provided foraging benefits for juvenile Chinook, chum, and coho salmon. Primary physical drivers differed for benthic, terrestrial, and pelagic invertebrates, and these invertebrate communities are expected to respond differentially depending on organic matter exchange and vegetative colonization. Restoring estuaries may take decades to meet certain success criteria, but our study demonstrates rapid enhancements in foraging resources understood to be used for estuary‐dependent wildlife.     

Anadromous sea lampreys (Petromyzon marinus) are ecosystem engineers in a spawning tributary

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Taxonomic and functional homogenisation of macroinvertebrate communities in recently intermittent Alpine watercourses

1. Mountain streams in southwestern European Alps are currently shifting from perennial to intermittent flow due to the combined effects of climate change and local anthropogenic pressures. Given that flow intermittency is a recently documented phenomenon in the Alps, only scattered studies have investigated functional and taxonomical diversity of benthic invertebrate communities in recently intermittent Alpine streams.
2. We used a hierarchical sampling design to investigate patterns in taxonomic and functional diversity of benthic invertebrate communities in 13 recently intermittent Alpine streams in north-west Italy. in April 2017, we sampled benthic communities in two reaches of each stream with different hydrological conditions: a control reach, with permanent flow; and an intermittent reach, which recently experienced non-flow periods in summer.
3. We tested for the response of taxonomic richness at multiple spatial scales by partitioning total diversity into the average richness of local communities and the richness due to variation among local communities both within and among reaches. By partitioning total diversity (γ) into its local (α) and turnover (β) components we showed a decrease in local and regional species richness both within and among reaches, whereas variation among communities was significantly lower in intermittent reaches at the reach scale only.
4. The analysis of multidimensional trait space of macroinvertebrate communities in reaches with different hydrological conditions revealed a significant reduction of functional diversity, dispersion, and evenness in intermittent reaches. There was trait overdispersion in intermittent reaches, as these hosted both typical Alpine taxa and organisms adapted to flow intermittency. In particular, we observed the replacement of taxa with aquatic respiration and those preferring medium- to fast-flowing oligotrophic waters by taxa adapted to lentic habitats, air breathing and with larval dormancy phases.
5. These results indicate that recent flow intermittency has caused drastic changes in benthic invertebrate communities in Alpine streams. Our work highlights the importance of integrating taxonomic and functional diversity to thoroughly assess the impacts of flow intermittency.

     

Environmental drivers of macroinvertebrate communities in high Arctic rivers (Svalbard)

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Combined effects of an anthropogenic (forest harvesting) and natural (extreme rainfall event) disturbance on headwater streams in New Zealand

1. Although extreme hydrological events are a natural component of river ecosystem disturbance regimes, their frequency is predicted to increase with climate change. Anthropogenic activities have the potential to exacerbate the impact of such disturbances but there are few studies on the combined effects of both anthropogenic and extreme hydrological disturbances on stream ecosystems.
2. We investigated the recovery of stream ecosystems over a 5-year period following the impact of an anthropogenic (forest clear-cut harvesting) and an extreme rainfall disturbance (estimated one-in-100 year average return interval) that generated debris flows in three headwater streams in New Zealand.
3. Initially, most of the riparian vegetation was eliminated and showed little recovery 1 year later. Subsequent riparian recovery was led by wind-borne, light-demanding, pioneering exotic weed species, lengthening and altering the long-term successional and recovery trajectories to a pre-disturbance composition of indigenous shrubs.
4. Stream shade, water temperature, and habitat had largely recovered after 5 years. However, the contribution of large wood to channel morphology and in-stream habitat was compromised due to diminished wood supplies in the stream channel and a hiatus in up-slope wood inputs until the riparian vegetation re-establishes and the next crop of trees matures.
5. After an initial decline, most indigenous fish taxa thrived in the post-disturbance conditions, with significant increases in densities and biomass. The more sensitive fish taxa were scarce or absent, particularly those taxa that prefer pools with overhead and in-stream cover provided by riparian vegetation and wood. Recovery of these taxa was outside the time frame of this study. Riffle dwelling fish communities were more resilient than pool dwelling fish communities.
6. Invertebrate densities showed a similar response to fish. Post-event invertebrate community composition differed from that typically found in post-harvest headwater streams, comprising comparatively lower proportions of Chironomidae, Oligochaetes, and Mollusca taxa, and higher proportions of Trichoptera taxa. Progression toward pre-event community composition was evident 5 years after the event.
7. The compounding effect of forest removal from harvesting, along with riparian vegetation and wood removal by debris flows, lengthened the recovery of riparian vegetation and wood supplies with cascading effects on in-stream habitat and biological communities.

     

Niche breadth of invertebrate shredders in tropical forest streams: which taxa have restricted habitat preferences?

Despite the importance of shredders in organic matter processing in streams, information about the habitat specificities of different taxa is scarce. Herein, we evaluated the habitat preferences of invertebrate shredders in tropical forest streams. A total of 72 leaf patches were sampled in three Atlantic Forest streams (SE Brazil). For each sample, 20 environmental variables were measured, including water properties and characteristics of the leaf patch. We used an Outlying Mean Index analysis to evaluate the niche breadth and overlap of each taxon found as well as habitat preferences. In total, we found 14 shredder taxa in 68 leaf patches, and the gradient of environmental conditions influenced the distribution of most taxa. Considering taxa that occurred in atypical habitats in the study sites, Blaberidae (semiaquatic cockroaches) and Trichodactylus fluviatilis (Decapoda) showed niche segregation, while Macrobrachium potiuna (Decapoda), Tupiperla (Plecoptera), and Nectopsyche (Trichoptera) showed niche overlap. On the other hand, Heterelmis (Coleoptera), Stenochironomus (Diptera), Phylloicus major, and Triplectides gracilis (Trichoptera) occurred in typical habitats. These results showed that shredder taxa had different habitat preferences. The observed differences in niche breadths and habitat specificities among taxa probably result in different leaf processing rates across leaf patches in Atlantic Forest streams.

     

Hydromorphological restoration of running waters: effects on benthic invertebrate assemblages

1. River restoration has received considerable attention, with much recent focus on restoring river hydromorphology to improve impoverished aquatic communities. However, we still lack a clear understanding of the response of aquatic biota to river restoration. 2. We studied the effects of hydromorphological restoration on benthic invertebrate assemblages in 25 river sites in Germany using standardised methods. Restoration efforts were primarily aimed to restore habitat heterogeneity; correspondingly, habitat diversity increased at most sites. 3. Similarity of benthic invertebrate assemblages between restored and unrestored river sections was low (mean similarity was 0.32 for Jaccard and 0.46 for Sørensen). Community‐based metrics, such as the percentage of Ephemeroptera, Plecoptera and Trichoptera taxa, also differed between restored and unrestored sections. 4. Only three of the 25 restored sections were classified as having ‘good ecological quality’ class according to the European Water Framework Directive criteria; hence, poor water quality is probably one factor impeding recolonisation. 5. Our results show that isolated restoration measures do not necessarily result in positive effects on aquatic biota and that better understanding of the interconnectedness within a catchment is required before we can adequately predict biotic responses to structural river restoration.     

Effects of retention site on breakdown of organic matter in a mountain stream

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Land‐use legacy and the differential response of stream macroinvertebrates to multiple stressors studied using in situ experimental mesocosms

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Streamlined eco‐engineering approach helps define environmental flows for tropical Andean headwaters

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