Effects of forest fire on headwater stream macroinvertebrate communities in eastern Washington,U.S.A.

1. Recent increases in fire frequency in North America have focused interest on potential effects on adjacent ecosystems, including streams. Headwaters could be particularly affected because of their high connectivity to riparian and downstream aquatic ecosystems through aquatic invertebrate drift and emergence. 2. Headwater streams from replicated burned and control catchments were sampled in 2 years following an intense forest fire in northeastern Washington (U.S.A.). We compared differences in benthic, drift and emergent macroinvertebrate density, biomass and community composition between five burned and five unburned catchments (14–135 ha). 3. There were significantly higher macroinvertebrate densities in burned than control sites for all sample types. Macroinvertebrate biomass was greater at burned sites only from emergence samples; in benthic and drift samples there was no significant difference between burn and control sites. 4. For all sample types, diversity was lower in the burned catchments, and the macroinvertebrate community was dominated by chironomid midges. 5. Compared to the effects of fire in less disturbed ecosystems, this study illustrated that forest fire in a managed forest may have greater effects on headwater macroinvertebrate communities, influencing prey flow to adjacent terrestrial and downstream aquatic habitats for at least the first 2 years post‐fire.     

Macroinvertebrate communities in Phragmites australis (Cav.) Trin. ex Steud. reed beds and open bank habitats in central victorian streams in Australia

Reed invasion is a common phenomenon of open streams with disturbed riparian vegetation in river catchments. Knowledge of the effects of such vegetation change on aquatic communities is fundamental to river management. Macroinvertebrate fauna in Phragmites australis (Cav.) Trin. ex Steud. and open bank habitats were examined in three rivers in central Victoria in order to understand the effect of such littoral habitat on macroinvertebrates. Data were analysed using Partially Nested Factorial ANOVA with season, river and habitats as main effects. Habitat structure had a significant effect (p<0.05) on macroinvertebrate species richness, however this was not seasonally consistent across the three rivers. There was a significant increase (p<0.05) in macroinvertebrate taxa richness in Phragmites habitats during winter and spring seasons. Total abundance of taxa showed no consistent significant differences in the two habitats. Results of Canonical Analysis of Principle Coordinates indicated significant differences (p<0.05) in macroinvertebrate assemblages between Phragmites and bare bank habitats in all seasons. Habitat selection by taxa could be related to the microphysical environment of the habitats. This study suggests that reed beds create important littoral habitat structures which support diverse macroinvertebrate assemblages.     

Salamander diversity alters stream macroinvertebrate community structure

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Macroinvertebrate and diatom communities as indicators for the biological assessment of river Picentino (Campania,Italy)

Pollution of rivers is an increasing problem that affects biological diversity and structure of natural ecosystem. The present study reported the results of the preliminary analysis of diatom and macroinvertebrate communities of river Picentino (Italy, Campania) in respect of the WFD/60/2000/EC. Because of the sensitive to a variety of environmental factors the two categories of organism are used as excellent indicators of changes taking place in water ecosystems, especially eutrophication. Sampling of benthic diatoms and macroinvertebrates has been carried out in five stations along the river during April–May 2014 in order to apply the ICMi and the STAR_ICMi and assess river quality. The data showed a diversification in diatomic and macroinvertebrate communities in relation to environmental stresses and level of pollution, with the disappearance of species higher sensitive to eutrophication and organic load in the upper course of the river. River water quality was found to deteriorate from the upperstream to the downstream because of the increasing of human impact and the intensive agriculture activity along the river.We conclude that the monitoring of diatomic and macroinvertebrate communities could give detailed information about the ecological status of rivers. However it is necessary to increase the achieved data by monitoring other biological communities in order to define adequated strategies to save and preserve the rivers habitat.     

Fire,flow and dynamic equilibrium in stream macroinvertebrate communities

1. The complex effects of disturbances on ecological communities can be further complicated by subsequent perturbations within an ecosystem. We investigated how wildfire interacts with annual variations in peak streamflow to affect the stability of stream macroinvertebrate communities in a central Idaho wilderness, USA. We conducted a 4‐year retrospective analysis of unburned (n = 7) and burned (n = 6) catchments, using changes in reflectance values (Δ NBR) from satellite imagery to quantify the percentage of each catchment’s riparian and upland vegetation that burned at high and low severity. 2. For this wildland fire complex, increasing riparian burn severity and extent were associated with greater year‐to‐year variation, rather than a perennial increase, in sediment loads, organic debris, large woody debris (LWD) and undercut bank structure. Temporal changes in these variables were correlated with yearly peak flow in burned catchments but not in unburned reference catchments, indicating that an interaction between fire and flow can result in decreased habitat stability in burned catchments. 3. Streams in more severely burned catchments exhibited increasingly dynamic macroinvertebrate communities and did not show increased similarity to reference streams over time. Annual variability in macroinvertebrates was attributed, predominantly, to the changing influence of sediment, LWD, riparian cover and organic debris, as quantities of these habitat components fluctuated annually depending on burn severity and annual peak streamflows. 4. These analyses suggest that interactions among fire, flow and stream habitat may increase inter‐annual habitat variability and macroinvertebrate community dynamics for a duration approaching the length of the historic fire return interval of the study area.     

Land-use effects on structural and functional composition of benthic and leaf-associated macroinvertebrates in four Andean streams

The replacement of native forests by pastures takes place widely in the Andes. The effects of such land-use change on aquatic assemblages are poorly understood. We conducted a comparative analysis of the effects of forest conversion to pastures on the taxonomic, structural, and functional composition of macroinvertebrates (benthic and leaf-associated) in montane and upper montane streams (ecosystem type) of the south Ecuadorian Andes. Taxonomic composition of benthic and leaf-associated macroinvertebrates was different between ecosystem type and land use. Also, major differences in the structural and functional composition of benthic and leaf-associated macroinvertebrates were mainly promoted by land use in both ecosystem types. Forested streams showed higher diversity than pasture streams, sustaining more shredder, scraper, and predatory invertebrates. We also observed differences in the macroinvertebrate communities between benthic and leaf-bag samples. Leaf bags had lower diversity and more collector invertebrates than benthic samples. This study highlights the large effect of riparian forest conversion to pasture land on macroinvertebrate communities, and the importance of using appropriate sampling techniques to characterize aquatic assemblages. We also recommend the maintenance and restoration of riparian vegetation to mitigate the effects of deforestation on stream communities and ecosystem processes.     

Abundance trends for river macroinvertebrates vary across taxa,trophic group and river typology

There is mounting evidence that terrestrial arthropods are declining rapidly in many areas of the world. It is unclear whether freshwater invertebrates, which are key providers of ecosystem services, are also declining. We addressed this question by analysing a long-term dataset of macroinvertebrate abundance collected from 2002 to 2019 across 5009 sampling sites in English rivers. Patterns varied markedly across taxonomic groups. Within trophic groups we detected increases in the abundance of carnivores by 19% and herbivores by 14.8%, while we estimated decomposers have declined by 21.7% in abundance since 2002. We also found heterogeneity in trends across rivers belonging to different typologies based on geological dominance and catchment altitude, with organic lowland rivers having generally higher rates of increase in abundance across taxa and trophic groups, with siliceous lowland rivers having the most declines. Our results reveal a complex picture of change in freshwater macroinvertebrate abundance between taxonomic groups, trophic levels and river typologies. Our analysis helps with identifying priority regions for action on potential environmental stressors where we discover macroinvertebrate abundance declines.     

Influence of riparian condition on aquatic macroinvertebrate communities in an agricultural catchment in south-eastern Australia

Riparian vegetation is known to affect aquatic macroinvertebrate communities through contributions of organic matter and shading. Despite the widespread degradation of riparian vegetation in Australia, there are relatively few studies examining the effect of changes in riparian vegetation on in-stream macroinvertebrate assemblages on individual catchments. In particular, information is lacking on the responses of macroinvertebrate communities in catchments dominated by agriculture, where farms that are managed at the paddock scale result in riparian vegetation condition varying over relatively short distances. In this study, macroinvertebrate assemblages were assessed from 12 reaches along a 25-km section of a small agricultural stream in south-eastern Australia. Riparian condition was assessed using in-stream coarse woody debris (CWD) levels and the rapid appraisal of riparian condition (RARC) index, a numerical system for categorising the health of riparian areas that incorporates sub-indices reflecting habitat continuity, vegetation cover, plant debris levels, native vegetation dominance, and other indicative features. There was a significant positive correlation between RARC scores and macroinvertebrate taxon richness (p < 0.01), and also between CWD scores and macroinvertebrate taxon richness (p < 0.05). In contrast, there was no significant correlation observed between riparian condition and the other macroinvertebrate indices (abundance, Shannon diversity, SIGNAL and SIGNAL2). Macroinvertebrate communities were significantly different in stream reaches from different riparian condition categories (ANOSIM; p < 0.05). Our results indicate that efforts to rehabilitate riparian vegetation may have a positive effect on in-stream biota even when implemented at a relatively small scale by individual landholders.     

Stream invertebrate diversity reduces with invasion of river banks by non‐native plants

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Effects of different management regimes on aquatic macroinvertebrate diversity in Australian rice fields

The maintenance of invertebrate diversity within agricultural environments can enhance a number of agronomically important processes, such as nutrient cycling and biological pest control. However, few Australian studies have been undertaken which specifically address the effects of commercial management regimes on rice field biodiversity. In this study, we compared aquatic macroinvertebrate communities within Australian rice fields cultivated under three commercial management regimes: conventional-aerial (agrochemicals applied, aerially sown), conventional-drill (agrochemicals applied, directly drill-sown) and organic-drill (agrochemical-free, directly drill-sown). These comparisons were undertaken using a combination of community assessment approaches, including morphospecies richness, abundance, diversity and community composition. In general, greater biodiversity existed within macroinvertebrate communities that developed under organic management regimes than under conventional regimes (i.e., higher morphospecies richness and Shannon diversity). Although there were significant differences in several parameters across management regimes early in the rice-growing season, as the growing season progressed the invertebrate communities that developed in the different management regimes became more similar. Only community composition analyses showed significant differences late in the growing season, with functional differences across aquatic faunal assemblages suggested by increased predator abundance in communities sampled from the organic management regime. In order to improve biodiversity within these aquatic environments, management techniques need to be examined individually and the most disruptive processes identified. Alternative management procedures can then be developed that minimise biodiversity loss whilst still delivering required agronomic outcomes.     

Functional Changes in Littoral Macroinvertebrate Communities in Response to Watershed-Level Anthropogenic Stress

Watershed-scale anthropogenic stressors have profound effects on aquatic communities. Although several functional traits of stream macroinvertebrates change predictably in response to land development and urbanization, little is known about macroinvertebrate functional responses in lakes. We assessed functional community structure, functional diversity (Rao’s quadratic entropy) and voltinism in macroinvertebrate communities sampled across the full gradient of anthropogenic stress in Laurentian Great Lakes coastal wetlands. Functional diversity and voltinism significantly decreased with increasing development, whereas agriculture had smaller or non-significant effects. Functional community structure was affected by watershed-scale development, as demonstrated by an ordination analysis followed by regression. Because functional community structure affects energy flow and ecosystem function, and functional diversity is known to have important implications for ecosystem resilience to further environmental change, these results highlight the necessity of finding ways to remediate or at least ameliorate these effects.     

Differences Found in the Macroinvertebrate Community Composition in the Presence or Absence of the Invasive Alien Crayfish,Orconectes hylas

Introductions of alien species into aquatic ecosystems have been well documented, including invasions of crayfish species; however, little is known about the effects of these introductions on macroinvertebrate communities. The woodland crayfish (Orconectes hylas (Faxon)) has been introduced into the St. Francis River watershed in southeast Missouri and has displaced populations of native crayfish. The effects of O. hylas on macroinvertebrate community composition were investigated in a fourth-order Ozark stream at two locations, one with the presence of O. hylas and one without. Significant differences between sites and across four sampling periods and two habitats were found in five categories of benthic macroinvertebrate metrics: species richness, percent/composition, dominance/diversity, functional feeding groups, and biotic indices. In most seasons and habitat combinations, the invaded site had significantly higher relative abundance of riffle beetles (Coleoptera: Elmidae), and significantly lower Missouri biotic index values, total taxa richness, and both richness and relative abundance of midges (Diptera: Chironomidae). Overall study results indicate that some macroinvertebrate community differences due to the O. hylas invasion were not consistent between seasons and habitats, suggesting that further research on spatial and temporal habitat use and feeding ecology of Ozark crayfish species is needed to improve our understanding of the effects of these invasions on aquatic communities.     

Flow‐related disturbances in forested and agricultural rivers: influences on benthic macroinvertebrates

Flow disturbances and conversions of land‐use types are two major factors that influence river ecosystems. However, few studies have considered their interactions and separated their individual effects on aquatic organisms. Using monthly monitoring data from two streams with different land‐use types (i.e. forest and agriculture) in the subtropical Central China over three years, we accurately predicted the changes of macroinvertebrate communities under flood disturbances and land‐use type conversions. The dominant taxa and main community metrics significantly declined following flash floods. Several mayflies and chironomid had rapid rates of recovery, which could reach high abundance in three months after floods. And most of the community metrics recovered more rapidly in the forested river than that in the agricultural river. Stepwise multiple regression (SMR) models were used to investigate the relationships between biotic metrics and hydrological and temporal variables. For example, SMR revealed that floods reduced the stability of benthic communities, and the length of low flow period was of considerable importance to the recovery of the fauna. Two‐way ANOVA indicated that intra‐annual fluctuation had more (e.g. the total abundance and wet biomass), equal (e.g. total richness, EPT richness, percent EPT abundance, and Margalef index), or less (e.g. tolerant value) influence on macroinvertebrate communities than land‐use types. Consequently, the effects of floods on macroinvertebrates should be taken into account when macroinvertebrates are used as indicators for assessing river ecosystem. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Aquatic insect β‐diversity is not dependent on elevation in Southern Rocky Mountain streams

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太子河大型底栖动物摄食功能群对河岸带土地利用类型的响应

为研究太子河大型底栖动物摄食功能群对河岸带土地利用类型的响应关系,于2012年5月对太子河流域底栖动物和水环境因子和土地利用类型进行野外调查及数据分析。结果表明：1）太子河流域底栖动物群落在4种不同土地利用类型内具有极显著差异,平均丰度、Shannon-Wiener多样性指数和Pielou均匀度指数在森林用地中最高,分别为8.86、0.73和0.94,平均密度在森林耕作用地中最高（782.75个/m²）,除食碎屑者功能群（S）,其他摄食功能群在不同土地利用类型内无差异（P > 0.05）。2）太子河土地利用类型与水环境因子之间的Pearson分析表明,森林用地与EC、TDS、TN、NH₃-N、COD_Mn之间呈显著负相关性,与DO、IOS之间呈显著正相关性;耕地与DO和IOS之间呈显著负相关性;城镇用地与EC、TDS和TN之间呈正相关性。3）太子河土地利用类型与底栖动物功能群之间的Spearman分析表明森林用地与食碎屑者（S）、刮食者（SC）和收集者（GC）呈正相关性。耕地与食碎屑者（S）、滤食者（FC）之间呈负相关性,城镇用地与刮食者（SC）和收集者（GC）之间呈显著负相关性。4）底栖动物功能群和水环境因子之间的典范对应分析表明,食碎屑者（S）功能群主要受底质指数（IOS）驱动,其他功能群与环境因子之间无相关性。因此,水环境因子和底栖动物群落参数比摄食功能群更能反映人类活动对土地利用的改变,水环境和底栖动物群落研究可为河岸带土地利用保护提供理论依据。     

Assessing the influence of wildfire on leaf decomposition and macroinvertebrate communities in boreal streams using mixed-species leaf packs

1. We investigated how compositional differences in riparian leaf litter derived from burned and undisturbed forests influenced leaf breakdown and macroinvertebrate communities using experimental mixed-species leaf packs in boreal headwater streams. Leaf pack mixtures simulating leaf litter from dominant riparian woody-stem species in burned and undisturbed riparian zones were incubated in two references and two fire-disturbed streams for 5 weeks prior to measuring temperature-corrected breakdown rates and macroinvertebrate community composition, richness, and functional metrics associated with decomposers such as shredder abundance and % shredders.
2. Leaf litter breakdown rates were higher and had greater variability in streams bordered by reference riparian forests than in streams where riparian forests had been burned during a wildfire. Streams bordered by fire disturbance showed significant effects of litter mixture on decomposition rates, observed as significantly higher decomposition rates of a fire-simulated leaf mixture compared to all other mixtures.
3. Variation among sites was higher than variation among litter mixtures, especially for macroinvertebrate community composition. In general, fire-simulated leaf mixtures had greater shredder abundances and proportions, but lower overall macroinvertebrate abundance; however, the shredder abundance trend was not consistent across all leaf mixtures at each stream.
4. These results show that disturbance-driven riparian forest condition and resulting composition of leaf subsidies to streams can influence aquatic invertebrate community composition and their function as decomposers. Therefore, if one of the primary goals of modern forest management is to emulate natural disturbance patterns, boreal forest managers should adapt silvicultural practices to promote leaf litter input that would arise post-fire, thereby supporting stream invertebrate communities and their function.

     

Turnover patterns in fish versus macroinvertebrates — implications for conservation planning

Spatial patterns in taxonomic richness and turnover for fish and aquatic macroinvertebrates are compared to assess the relative usefulness of each taxonomic group in mapping biodiversity patterns. Fish and aquatic macroinvertebrate species data for sites down the longitudinal axes of nine rivers in four provinces along the eastern side of South Africa were analysed. Fish and aquatic macroinvertebrate data from previous studies and recent river surveys were used in analyses of species richness and turnover. Fish proved to be not useful for mapping biodiversity patterns, as measured by turnover, whereas aquatic macroinvertebrate species patterns exhibited predictable patterns of turnover with downstream distance. Average turnover rates could be decomposed into turnover of common (‘core’) species, which were accelerated by presence of rare and narrow-range species. Disruptions to the river continuum impacted on the rate of turnover. Consistent with other research on South African rivers, aquatic macroinvertebrate communities could be grouped into upland versus lowland assemblages, and also be defined by longitudinal zones. Fish biodiversity patterns should be viewed at a riverscape scale, whereas macroinvertebrate patterns are more easily discerned at a segment-reach scale, and applied to reflect connectivity and environmental gradients respectively.     

Flow permanence and macroinvertebrate community diversity within groundwater dominated headwater streams and springs

The response of aquatic macroinvertebrate communities to flow permanence within limestone springs and headwater streams was examined across the English Peak District. At the regional scale, macroinvertebrate communities of perennial and intermittent springs displayed significant differences in the number of taxa, macroinvertebrate community abundance, diversity indices (Shannon and Simpson indices) and the Berger–Parker dominance index at intermediate discharge. However, no significant difference was recorded between intermittent and perennial sites at high discharge or when all sampling occasions were pooled. At the catchment scale, the number of taxa, community abundance and Bray–Curtis similarity coefficients within the River Lathkill differed significantly between intermittent springs and other habitats. At both the regional and catchment scale the macroinvertebrate communities of intermittent springs were characterised by a small number of taxa displaying life cycle adaptations to intermittent aquatic habitats, particularly Trichoptera.     

Macroinvertebrate communities of karst springs of two river catchments in the Southern Limestone Alps (the Julian Alps, NW Slovenia)

The macroinvertebrate communities of 16 karst springs in the Southern Limestone Alps (Slovenia, SE Europe), were studied from May to September 1999, together with the major chemical parameters of the water and selected physical characteristics of the springs. The springs are located in an area of 800 km², between 410 and 955 m a.s.l., and drain into two rivers whose catchments are separated by mountain ranges up to 2864 m. The Soča river drains into the Adriatic Sea and the Sava into the Black Sea. Springs showed relatively large fluctuations in discharge and small variations in temperature (normally about 1 °C) during the period of study. Seventy macroinvertebrate taxa were collected. Chironomidae (Diptera), Limnephilidae (Trichoptera), Enchytraeidae (Oligochaeta), Tricladida (Turbellaria) and Belgrandiella kuesteri (Gastropoda) were the most widespread taxa, collected from the majority of sampling sites. The environmental characteristics showed a great heterogeneity, and there was a large variation in the taxonomic composition and relative abundance of taxa between springs and during seasons. The coexistence of taxa with highly divergent ecological requirements is characteristic of the spring communities studied. They range from stygobionts and spring-restricted species to ubiquitous species. The differences observed in spring fauna in the two river catchments were probably dictated by differences in local environmental parameters and not by the geographical location in the different river catchments.     

Reduced breeding success of Pied Flycatchers Ficedula hypoleuca along regulated rivers

Most large rivers in northern Sweden are regulated to produce hydropower, with subsequent effects on flow dynamics and aquatic insect communities. Several studies have shown that aquatic and terrestrial systems are intimately connected via the export of emergent aquatic insects, but few have assessed how human modifications of aquatic habitats may influence this connection. We compared breeding success of the insectivorous Pied Flycatcher Ficedula hypoleuca in near‐riparian upland forests along two regulated and two free‐flowing large rivers in northern Sweden over 3 years. The regulated rivers showed lower aquatic insect export to the surroundings, as a consequence of regulation‐induced loss of suitable aquatic insect habitats. Survival of Pied Flycatcher nestlings was 10–15% greater along the free‐flowing rivers. Females breeding near the free‐flowing rivers also started egg‐laying earlier and with greater synchrony than those at the regulated rivers, and showed a smaller decrease in weight during breeding than did females along the regulated rivers. However, there were no differences in occupation rate, clutch size or number of successfully hatched juveniles between regulated and free‐flowing rivers. As regulated rivers showed lower abundance of flying aquatic insects, which may also reduce the abundance of terrestrial invertebrate prey, regulation‐induced changes in the export of emergent aquatic insects may explain both directly and indirectly the observed reduction in Pied Flycatcher breeding success along regulated rivers. Large‐scale river regulation may therefore impair the breeding success of insectivorous birds through impacts on prey availability.