Riparian Invertebrates Research Articles

Fast but transient recovery of aquatic and terrestrial communities after a large dam removal

IntroductionEcological restoration through dam removals receives increasing attention from scientists, environmental managers and policy makers. However, most dam removal projects focus on small structures (< 10 m in height) and on few ecosystem compartments at a time (e.g. river morphology, reservoir sedimentation, aquatic invertebrates, terrestrial vegetation), but rarely aquatic and riparian ecosystems simultaneously.MethodsWe explored the joint taxonomic recovery (temporal patterns in α- and β-diversity) of three communities after the removal of the Vezins dam (36 m in height; Sélune River, France): aquatic benthic invertebrates, riparian invertebrates, and the riparian vegetation. These communities were monitored yearly, during three years after the dam removal, on sites located within (n = 3; restored sites) and outside (n = 3; two upstream and one downstream; non-impounded sites) the former reservoir.ResultsResults showed a fast recovery of the three ecological communities, as patterns in α-diversity between restored and non-impounded sites were not necessarily different from each other 1.5 years after complete reservoir dewatering. The mean number of species or morphospecies (± standard deviation) reached up to 28.2 ± 5.2, 17.0 ± 2.3 and 77.5 ± 11.2 for the aquatic invertebrates, and the riparian vegetation and invertebrates, respectively. Relative to the sampled area, the riparian invertebrates were the most diversified of all ecological communities with > 500 taxa (i.e., pooling all sites and years). In addition, in some restored sites, α-diversity kept increasing over time while species turnover (β-diversity) remained high after three years for all ecological communities suggesting a transient recovery (i.e., still facing temporal changes in species diversity and composition). This recovery was mediated by the identity of the ecological community as inter-annual changes in α- and β-diversity of the riparian vegetation were less pronounced compared to those of aquatic and terrestrial invertebrates. This recovery depended also on site-specific features as the most distant restored site from the former dam had more time for recovery following the slow reservoir dewatering and through increased sedimentation in the downstream site.DiscussionDifferential patterns of recovery in α- and β-diversity found in this study are discussed in light of species functional traits and ecosystem functioning.

A standardized multi‐method survey to enhance characterization of riparian invertebrate communities

AbstractRiparian invertebrate communities are species rich, but variability in sampling methods hampers assessment of their distributions and inference of the quality of their habitats. To reduce this variability, a standardized, multi‐method survey protocol was recently developed. Here, riparian beetle community surveys conducted before and after the protocol's introduction were used to evaluate its effectiveness in characterizing communities and in limiting variability among surveys. Use of the standardized protocol reduced variability in sampling effort, and this had a limited effect on estimates of taxonomic richness. Surveys using the protocol captured significantly more species than surveys done before its introduction, evidencing the benefits of standardized multi‐method survey protocols. Our study highlights that standardized multi‐method survey protocols may enable identification and prioritization of sites requiring management to improve habitat quality. As such, we recommend the integration of such protocols into monitoring programmes, to enhance protection of biodiverse invertebrate communities in vulnerable riparian habitats.

Riparian Vegetation Structure Influences Terrestrial Invertebrate Communities in an Agricultural Landscape

Stream and terrestrial ecosystems are intimately connected by riparian zones that support high biodiversity but are also vulnerable to human impacts. Landscape disturbances, overgrazing, and diffuse pollution of agrochemicals threaten riparian biodiversity and the delivery of ecosystem services in agricultural landscapes. We assessed how terrestrial invertebrate communities respond to changes in riparian vegetation in Romanian agricultural catchments, with a focus on the role of forested riparian buffers. Riparian invertebrates were sampled in 10 paired sites, with each pair consisting of an unbuffered upstream reach and a downstream reach buffered with woody riparian vegetation. Our results revealed distinct invertebrate community structures in the two site types. Out of 33 invertebrate families, 13 were unique to either forested (6) or unbuffered (7) sites. Thomisidae, Clubionidae, Tetragnathidae, Curculionidae, Culicidae, and Cicadidae were associated with forested buffers, while Lycosidae, Chrysomelidae, Staphylinidae, Coccinellidae, Tettigoniidae, Formicidae, and Eutichuridae were more abundant in unbuffered sites. Despite statistically equivocal results, invertebrate diversity was generally higher in forested riparian buffers. Local riparian attributes significantly influenced patterns in invertebrate community composition. Our findings highlight the importance of local woody riparian buffers in maintaining terrestrial invertebrate diversity and their potential contribution as a multifunctional management tool in agricultural landscapes.

Small Patches of Riparian Woody Vegetation Enhance Biodiversity of Invertebrates

Patches of riparian woody vegetation potentially help mitigate environmental impacts of agriculture and safeguard biodiversity. We investigated the effects of riparian forest on invertebrate diversity in coupled stream-riparian networks using a case study in the Zwalm river basin (Flanders, Belgium). Agriculture is one of the main pressures in the basin and riparian forest is limited to a number of isolated patches. Our 32 study sites comprised nine unshaded “unbuffered” sites which were paired with nine shaded “buffered” sites on the same stream reach, along with five ‘least-disturbed’ sites and nine downstream sites. We sampled water chemistry, habitat characteristics and stream and riparian invertebrates (carabid beetles and spiders) at each site. Three methods were used to quantify riparian attributes at different spatial scales: a visually-assessed qualitative index, quantitative estimates of habitat categories in six rectangular plots (10 × 5 m) and geographic information system (GIS)-derived land cover data. We investigated relationships between invertebrates and riparian attributes at different scales with linear regression and redundancy analyses. Spiders and carabids were most associated with local riparian attributes. In contrast, aquatic macroinvertebrates were strongly influenced by the extent of riparian vegetation in a riparian band upstream (100–300 m). These findings demonstrate the value of quantifying GIS-based metrics of riparian cover over larger spatial scales into assessments of the efficacy of riparian management as a complement to more detailed local scale riparian assessments in situ. Our findings highlight the value of even small patches of riparian vegetation in an otherwise extensively disturbed landscape in supporting biodiversity of both terrestrial and freshwater invertebrates and emphasize the need to consider multiple spatial scales in riparian management strategies which aim to mitigate human impacts on biodiversity in stream-riparian networks.

Maintaining mechanisms of riparian invertebrate biodiversity: A review

Riparian zones, the critical ecological interfaces between terrestrial and aquatic ecosystems, are species rich habitats. However, riparian zones are seriously threatened by human activities in the world. Riparian invertebrates represent a large proportion of riparian biodiversity, perform various ecological functions, and provide an essential link between aquatic and terrestrial ecosystems. Although many studies have investigated the riparian invertebrate communities, there is lacking a comprehensive summary of maintaining mechanisms underlying riparian invertebrate diversity. This review discussed seven characteristics of riparian zones that might support high riparian invertebrate diversity: flood and drought, nutrient, microhabitat diversity, riparian vegetation, microclimate gradients, food resources and river spatial gradients. Further, we summarized the maintaining mechanisms of riparian invertebrate diversity. Disturbances of periodic flood and drought trigger the reproduction and migration of invertebrates, increase the turnover of invertebrate communities, and create suitable conditions for riparian invertebrates. Adequate nutrients support a high invertebrate diversity by increasing primary productivity of riparian habitats. Elevated microhabitat diversity provides a variety of niche space for specialist riparian invertebrates. Strong microclimate gradients provide complex and diverse habitats and thus facilitate the coexistence of aquatic and terrestrial invertebrates in riparian zones. Cross-ecosystem resource subsidies increase food availability and contribute unique food sources to riparian invertebrates. The differentiation of these factors along river longitudinal and lateral gradients provides conditions for the diversification of riparian invertebrates at a larger scale. Understanding the maintaining mechanisms of riparian invertebrate diversity is important for conservation of riparian biodiversity and integrated management of river ecosystems.

Dispersal capacity shapes responses of river island invertebrate assemblages to vegetation structure, island area, and flooding

Abstract Riparian invertebrate communities occupy a dynamic ecotone where hydrogeomorphological (e.g. river flows) and ecological (e.g. succession) processes may govern assemblage structure by filtering species according to their traits (e.g. dispersal capacity, niche). We surveyed terrestrial invertebrate assemblages (millipedes, carabid beetles, spiders) in 28 river islands across four river catchments over 2 years. We predicted that distinct ecological niches would produce taxon‐specific responses of abundance and species richness to: (i) disturbance from episodic floods, (ii) island area, (iii) island vegetation structure, and (iv) landscape structure. We also predicted that responses would differ according to species’ dispersal ability (aerial vs. terrestrial only), indicating migration was sustaining community structure. Invertebrate abundance and richness was affected by different combinations of vegetation structure, island area, and flood disturbance according to species’ dispersal capacity. Carabid abundance related negatively to episodic floods, particularly for flightless species, but the other taxa were insensitive to this disturbance. Larger islands supported greater abundance of carabids and all invertebrates able to disperse aerially. Vegetation structure, particularly tree canopy density and plant richness, related positively to invertebrate abundance across all taxa and aerial dispersers, whereas terrestrial disperser richness related positively to tree cover. Landscape structure did not influence richness or abundance. Multiple ecological processes govern riparian invertebrate assemblages. Overall insensitivity to flood disturbance and responses contingent on dispersal mode imply that spatial dynamics subsidise the communities through immigration. Particular habitat features (e.g. trees, speciose vegetation) may provide refuges from disturbance and concentration of niches and food resources.

Bright lights, big city: influences of ecological light pollution on reciprocal stream–riparian invertebrate fluxes

Cities produce considerable ecological light pollution (ELP), yet the effects of artificial night lighting on biological communities and ecosystem function have not been fully explored. From June 2010 to June 2011, we surveyed aquatic emergent insects, riparian arthropods entering the water, and riparian spiders of the family Tetragnathidae at nine stream reaches representing common ambient ELP levels of Columbus, Ohio, USA, streams (low, 0.1-0.5 lux; moderate, 0.6-2.0 lux; high, 2.1-4.0 lux). In August 2011, we experimentally increased light levels at the low- and moderate-treatment reaches to 10-12 lux to represent urban streams exposed to extremely high levels of ELP. Although season exerted the dominant influence on invertebrate fluxes over the course of the year, when analyzed by season, we found that light strongly influenced multiple invertebrate responses. The experimental light addition resulted in a 44% decrease in tetragnathid spider density (P = 0.035), decreases of 16% in family richness (P = 0.040) and 76% in mean body size (P = 0.022) of aquatic emergent insects, and a 309% increase in mean body size of terrestrial arthropods (P = 0.015). Our results provide evidence that artificial light sources can alter community structure and ecosystem function in streams via changes in reciprocal aquatic-terrestrial fluxes of invertebrates.

Effect of catchment urbanization on ant diversity in remnant riparian corridors

The conversion of rural land to residential use is occurring rapidly as the global trend of city expansion continues. The impact of this land use change on riparian biodiversity was investigated by examining ant communities from 12 remnant riparian corridors in northwest Sydney, Australia. Ants were sampled from rural and urban catchments using pitfall traps. Data on vegetation floristics, habitat structure and stream water quality were also collected. No significant differences in ant diversity metrics or assemblage structure were found between urban and rural sites. Similarly, very few environmental variables revealed significant differences between land use types. One exception, however, was the percentage cover of exotic plants, which was related to ant assemblage structure. Small-leaved and broad-leaved privet (Ligustrum spp.) were highly correlated with total weed cover. The results suggest that ants respond mostly to small-scale habitat characteristics, especially those related to the dominance of exotic plants. As all sites had experienced some level of human impact, it is possible that all the sites have already transgressed an ecological threshold due to the earlier catchment land use change from natural to agricultural use. This apparent sensitivity may explain the failure to observe any significant differences between the urban and rural catchments examined in this study. It is recommended that managers looking to protect the integrity of riparian invertebrate communities should focus on addressing local habitat pressures in human-modified catchments.

Testing the Effects of an Introduced Palm on a Riparian Invertebrate Community in Southern California

Despite the iconic association of palms with semi-arid regions, most are introduced and can invade natural areas. Along the San Diego River (San Diego, California, USA), the introduced Canary Island date palm (Phoenix canariensis) forms dense patches among native riparian shrubs like arroyo willow (Salix lasiolepis). The structural differences between the palm and native shrubs are visually obvious, but little is known about palm’s effects on the ecosystem. We tested for the effects of the palm on a riparian invertebrate community in June 2011 by comparing the faunal and environmental variables associated with palm and willow canopies, trunks and ground beneath each species. The palm invertebrate community had lower abundance and diversity, fewer taxa feeding on the host (e.g., specialized hemipterans), and more taxa likely using only the plant’s physical structure (e.g., web-builders, oak moths, willow hemipterans). There were no observed effects on the ground-dwelling fauna. Faunal differences were due to the physical and trophic changes associated with palm presence, namely increased canopy density, unpalatable leaves, trunk rugosity, and litter accumulations. Palm presence and resulting community shifts may have further ecosystem-level effects through alteration of physical properties, food, and structural resources. These results were consistent with a recent study of invasive palm effects on desert spring arthropods, illustrating that effects may be relatively generalizable. Since spread of the palm is largely localized, but effects are dramatic where it does occur, we recommend combining our results with several further investigations in order to prioritize management decisions.

Reciprocal fluxes of stream and riparian invertebrates in a coastal California basin with Mediterranean climate

AbstractStream and riparian food webs are connected by reciprocal fluxes of invertebrates, and a growing number of studies demonstrate strong effects of these subsidies on consumers and food webs in both habitats. However, despite its importance in understanding energy flow between these habitats, seasonality of reciprocal subsidies has been examined only in a single temperate system in Japan. We measured input of terrestrial invertebrates and emergence of adult aquatic insects for 14 months in two adjacent streams in a coastal Mediterranean basin in California to assess seasonal patterns, annual fluxes, and local variation. Fluxes of terrestrial and aquatic invertebrates fluctuated seasonally and were relatively synchronous, although in the fall of 2004, terrestrial inputs peaked 1–2 months earlier than emergence. Terrestrial inputs were similar in the two streams with annual flux of 7.9–8.6 g dry mass m−2 year−1. Emergence differed between the streams: annual emergence was 7.8 g m−2 year−1 (similar to terrestrial flux) in one reach but 5.3 g m−2 year−1 from the other. The presence of streambed travertine in the reach with lower emergence was the primary difference in habitat between the streams, suggesting that travertine may reduce emergence and alter net reciprocal flux. Comparison of our results with those from Japan suggests that seasonality and net annual flux of reciprocal stream‐riparian subsidies vary among biomes due to differences in climate, vegetation, and geography. Our results also indicate that local factors, such as travertine, may cause reciprocal fluxes to vary at finer spatial scales.

Including wildlife habitat in the definition of riparian areas: The beaver (Castor canadensis) as an umbrella species for riparian obligate animals

Riparian wildlife is as important as vegetation in maintaining watercourse ecological integrity, yet present riparian buffer guidelines often fail to maintain sufficient terrestrial habitat for a variety of riparian species in North America. This is of particular concern for the conservation of riparian obligate animals, defined as freshwater-dependent species for which the terrestrial habitat immediately adjacent to watercourses is indispensable to complete their life history. Terrestrial habitat requirements of riparian obligate species are reviewed in this paper using the North American beaver (Castor canadensis) as a focal species. As an ecosystem engineer, the beaver has a profound influence on the shape and function of riparian ecosystems and creates diverse habitat patches. Published data show that 95% of woody plants cut by beavers on land are obtained within 50 m of the water’s edge. A review of riparian invertebrates, amphibians, reptiles, mammals, and birds indicates that a 50 m-wide riparian buffer (measured from the high water mark) in its natural state (intact native vegetation) is the minimum area for supporting the majority of riparian obligate species. Exceptions are moose and some amphibian species that also need habitat well beyond 50 m from the water’s edge to complete their life history. To conserve these wide-ranging species it is recommended that riparian buffers be continuous and integrated in a connectivity plan including upland reserves. Such a watershed-wide plan will also ensure that riparian buffers can serve as travel and dispersal corridors for both riparian and upland wildlife.

The role of microhabitat and food availability in determining riparian invertebrate distributions on gravel bars: a habitat manipulation experiment

AbstractExposed riverine sediments (ERS) are an important ecotone, where aquatic and terrestrial habitats and species interact. Within an area of ERS, invertebrate species richness tends to be highest along the water's edge ecotone. In this article, we discuss a habitat manipulation experiment which was conducted to test the hypotheses that ERS invertebrate distribution is linked to: (1) the availability of food items (emerging and stranded aquatic invertebrates) and (2) favourable physical microhabitat and microclimate (temperature and moisture). Four experimental plots were created (wet, wet‐fed, dry‐fed and dry control plot), replicated three times. The plots were wetted using a capillary pump system, and fed with dried blood worms (Chironomids) for 28 days. Sediment temperature was measured at 15‐min intervals. Hand searches were undertaken on 25% of each plot after 7, 14, 21 and 30 days. Significant temperature differences were observed between the wet and dry sediment and the air temperature. Wet plots were 1·9 °C cooler on average than the dry plots and had a smaller temperature range; all plots remained significantly warmer than the air temperature. The wet and wet‐fed plots yielded significantly greater numbers of beetles than the dry and dry‐fed plots; however, no significant difference was found between the wet and wet‐fed plots. Spiders were significantly associated with dry plots and showed no response to food variability. These results suggest that micro‐environment and not food availability is the main driving factor underlying beetle distribution and movement, although it is possible that they are using lower temperatures and increased moisture as a cue for aquatic food availability. Copyright © 2011 John Wiley & Sons, Ltd.

Order and disorder in the river continuum: the contribution of continuity and connectivity to floodplain meadow biodiversity

AbstractAim Aspects of connectivity and continuity operating in the River Meuse were analysed for their contribution to the biodiversity of the floodplain. From this analysis of the diversity and composition of the meadow communities, we aimed to derive effective biodiversity conservation strategies.Location The River Meuse is one of the larger rivers in the European Western Plains ecoregion. The alluvial plains of the river have a long history of cultivation, and for these plains the floodplain meadow vegetation is a highly appreciated and valuable nature conservation asset.Method We sampled floodplain meadows from 400 km of the six geomorphic reaches of the middle to lower course of the River Meuse. For each, 50 vascular plant relevés were recorded, representing the spectrum of floodplain meadow communities of that reach. Beta diversity was calculated to quantify similarity in species pools between the reaches. A dissimilarity formula was used to determine the turnover between the reaches, and these dissimilarities were compared with a Mantel test to detect whether species composition of the floodplain meadows exhibited connectivity and continuity between the reaches. Species richness for the floodplain vegetation data of the reaches was compared with data for riparian invertebrate communities. The vegetation data sets were ordinated using detrended correspondence analysis (DCA) to reveal patterns in the floodplain meadow species composition, and the DCA axes were related to plant functional groups and population strategies. The axis scores of the species and plots were linked to river and plant species traits.Results We did not observe an overall continuity trend in similarity, nor one in diversity in a downstream direction. Lateral connectivity was highlighted by the dissimilarity between the reaches and in the influxes of species from adjacent ecoregions. The DCA ordination showed statistically significant separations between reaches and between the plant functional groups. The second DCA axis related to the longitudinal gradient of the river, whereas the first axis showed stronger correlations with river and plant species traits. We termed this axis the ‘disorder axis’. Plant invaders and avoiders are located at the left side of the disorder axis, whereas the true river‐adapted categories of resisters and endurers are at the right extremity. Contributions to the disorder were identified in terms of connectivity with adjacent ecoregions and the physical disturbance regime of natural and anthropogenic perturbations, resulting in community changes between the reaches.Main conclusions We concluded that a single overall strategy for biodiversity conservation of the river or its floodplains is not feasible. Strategies can, however, be derived for separate river reaches based on functional groups in the communities, the disorder characteristics of the reach, and the influence of surrounding ecoregions.

Effects of Water Removal on a Hawaiian Stream Ecosystem

A 3-year study of Wainiha River on Kaua'i, Hawai'i, was carried out to determine the impact that water removal had on key stream ecosystem parameters and functions. The study area included a diversion dam for a hydroelectric plant that removes water at an elevation of 213 m and returns it to the stream about 6 km downstream at an elevation of 30 m. There were two highelevation sites, one with undiverted flow and one with reduced flow, and two low-elevation sites, one with reduced flow and one with full flow restored. Monthly samples were taken of instream and riparian invertebrates and plants. When samples from similar elevations were compared, dewatered sites had lower concentrations of benthic photosynthetic pigments than full-flow sites, and benthic ash-free dry mass (AFDM) was higher at the two low-elevation sites regardless of flow. Benthic chlorophyll a (chl a) and AFDM were higher in summer months than in the winter. Benthic invertebrate abundance was highest at the full-flow, low-elevation site and benthic invertebrate biomass was highest at the full-flow, high-elevation site. Season had only marginal effects on abundance and biomass of benthic invertebrates. Diversity of benthic invertebrates was higher at the more-downstream sites. Abundance of drifting invertebrates was highest at the site above the diversion dam and generally higher in winter than in summer months. Biomass of drifting invertebrates was also highest at the above-dam site but there was little seasonal difference. Almost all parameters measured were lowest at the site just downstream of the diversion dam. The biotic parameters responded only weakly to flows that had occurred up to 1 month before the measurements were made. Flow, elevation, and season interact in complex ways that impact ecosystem parameters and functions, but water diversion can override all these environmental factors.

Impact of a 100‐year flood on vegetation, benthic invertebrates, riparian fauna and large woody debris standing stock in an alpine floodplain

AbstractThis paper investigates the impact of a 100‐year flood in May 1999 on community composition and large woody debris standing stock in an alpine floodplain (Isar, Germany). Detailed pre‐flood data sampled from 1993 to 1998 are compared with the situation directly after the flood. In those parts of the Isar floodplain mainly covered with pioneer vegetation prior to flooding, the coverage of unvegetated gravel bars increased by 22% following the flood. However, the flood did not remove larger amounts of older successional vegetation stages (willow thickets, floodplain forest). No significant changes in the benthic invertebrate fauna were recorded. The lowest densities of riparian ground beetles (Carabidae) within the study were recorded one month after the flood. Two months later, the ground beetle densities increased to the highest values ever recorded, indicating the ground beetle's high potential for recolonization. These results highlight the degree of resilience of both the aquatic and the riparian invertebrate fauna. The flood also caused a significant increase in large woody debris standing stock; in one section the number of logs increased tenfold and the volume increased by a factor of 20, leading to the assumption that most woody debris in alluvial flood‐plains is provided by catastrophic events. Copyright © 2004 John Wiley & Sons, Ltd.

Analysis of wet edaphic riparian communities of a Mediterranean hydrographic network: the Arc (Bouches-du-Rh�ne, France)

The composition of benthic communities is a good criterion to estimate water quality. Is this also true of the wet edaphic riparian invertebrates, less directly exposed to the impact of the water? What abiotic factors determine the distribution of species within a hydrosystem? These questions were addressed, using the River Arc and its hydrographic network, subject to various anthropogenic aggressions (urbanization, industry, agriculture) and offering varied hydrochemical situations. The riparian population (158 taxa) was analysed, using Reciprocal Averaging (9 sampling points on the main course and its tributaries). Results show that spatial variation of the edaphic riparian zoocenosis is chiefly determined by the nature of the substratum and, to a lesser extent, by the hydrologic instability of the water course. However, it can respond to some constraints of the environment like benthic macroinvertebrates.

Observations on behaviour and foraging of the Ibisbill Ibidorhyncha struthersii in Nepal

In March and April 1984, I studied the territorial, courtship and foraging behaviour of Ibisbills Ibidorhyncha struthersii, mainly on Langtang Khola in Nepal. On their river‐bed breeding grounds, Ibisbills were territorial, rival birds meeting on shingle banks and performing prolonged circling displays. Aquatic invertebrates, especially stoneflies, mayflies and caddisflies, were the main prey, but fish and riparian invertebrates were taken also. When the water temperature was below 5oC, invertebrates were inactive and hidden beneath submerged stones, where the birds probed for them. When the water temperature was above 5oC, many invertebrates drifted in the water and Ibisbills switched to pecking at them from preferred feeding stations. Riparian foraging involved probing beneath stones on shingle banks and probing into soil. Foraging responses to changes in prey behaviour were similar to those of the Black Stilt Himantopus novaezealandiae on New Zealand river‐beds.