Response Of Benthic Macroinvertebrate Communities Research Articles

Responses of multi-faceted benthic macroinvertebrates alpha and beta diversity to flooding in a highland floodplain

Flooding is an important process in natural fluvial floodplains. How the flood shapes aquatic community diversity in highland floodplains is still poorly understood. The aim of this study was to unravel the multi-faceted responses of benthic macroinvertebrate diversity to flooding and habitat environments in the Baihe River Basin from a taxonomic, phylogenetic, and functional perspective. We examined the alpha and beta diversity patterns of benthic macroinvertebrate communities in the mainstream, tributaries, and oxbow lakes during the normal water and flood periods. The results showed that the traditional alpha taxonomic diversity (TD) varied across habitats, despite minor changes after flood pulse. Alpha phylogenetic diversity (PD) decreased and alpha functional diversity (FD) markedly increased after flooding, with functional traits transiting toward risk avoidance. While all the three facets of beta diversity significantly responded to habitat differences, beta TD and PD shifted in response to flooding. Species turnover prominently increased in beta TD and PD after flood pulse, which contrasted with a weaker response of this process in FD. The explanatory power of significant environmental factors on both alpha and beta diversity was reduced by flooding. Compared with traditional TD, cooperating multi-faceted diversity could better depict the responses of benthic macroinvertebrate communities to flooding. The assessment and conservation of aquatic biodiversity in highland floodplains should take into account the three facets of alpha and beta diversity.

Implications of taxonomic and numerical resolution on DNA metabarcoding-based inference of benthic macroinvertebrate responses to river restoration

It is essential to explore and define the level of taxonomic identification and quantification approaches for diversity and biomonitoring studies, given their potential influence on assessing and interpreting ecological outcomes. This study assessed the response of benthic macroinvertebrate communities to restore and construct gravel bars in a dam-impacted river, with non-dam influenced tributaries serving as reference sites. Additionally, we evaluated the performance of different taxonomic and numerical (i.e., abundance vs. presence/absence data) resolutions of DNA metabarcoding with consequent comparison to morphology-based identification and how it affects assessment outcomes. DNA metabarcoding detected 93% of the morphologically identified individuals and provided finer taxonomic resolution. We also detected significant correlations between morphological sample abundance, biomass, and DNA metabarcoding-read abundance. Furthermore, we observed a relatively high and significant congruence in macroinvertebrate community structure and composition between different taxonomic and numerical resolutions of both methods. This indicates a satisfactory surrogacy between the two approaches and their varying identification levels and data transformation. Additionally, community–environmental associations were significant for all datasets but showed significant varying associations with physicochemical parameters. Our observations imply that coarser taxonomic resolution could be highly advantageous for DNA metabarcoding-based applications in situations where the lack of taxonomic information, e.g., poor reference database, might severely affect biological assessment quality.

Responses of Benthic Macroinvertebrate Communities of Two Tropical, High-Mountain Lakes to Climate Change and Deacidification

High-mountain lakes are among the most comparable ecosystems globally and recognized sentinels of global change. The present study pursued to identify how the benthic macroinvertebrates (BMI) communities of two tropical, high mountain lakes, El Sol and La Luna, Central Mexico, have been affected by global/regional environmental pressures. We compared the environmental characteristics and the BMI communities between 2000–2001 and 2017–2018. We identified three principal environmental changes (the air and water temperature increased, the lakes’ water level declined, and the pH augmented and became more variable), and four principal ecological changes in the BMI communities [a species richness reduction (7 to 4), a composition change, and a dominant species replacement all of them in Lake El Sol, a species richness increase (2 to 4) in Lake La Luna, and a drastic reduction in density (38% and 90%) and biomass (92%) in both lakes]. The air and water temperature increased 0.5 °C, and lakes water level declined 1.5 m, all suggesting an outcome of climate change. Contrarily to the expected acidification associated with acid precipitation, both lakes deacidified, and the annual pH fluctuation augmented. The causes of the deacidification and the deleterious impacts on the BMI communities remained to be identified.

Responses of benthic macroinvertebrate communities to a Bti-based insecticide in artificial microcosm streams

Bioinsecticides based on the bacterium Bacillus thuringiensis subsp. israelensis (Bti) are increasingly being applied directly into aquatic compartments to control nuisance mosquitoes and blackflies and are generally considered environmentally friendly alternatives to synthetic insecticides. Bti-based insecticides are considered highly selective, being Diptera-specific, and supposedly decompose rapidly in the environment. Nevertheless, their safety to non-target species and freshwater ecosystems has been questioned by recent studies, which in fact document possible indirect effects in aquatic food webs such as the decrease of prey availability to predators. This work aimed to evaluate the potential effects of a Bti-based insecticide (VectoBac® 12AS) on a freshwater macroinvertebrate community and on stream ecological functions by using artificial microcosm streams. Artificial microcosm streams were colonized with a macroinvertebrate community plus periphyton collected in a stream together with Alnus glutinosa leaf packs. They were exposed for 7 days to different Bti treatments (0, 12, 120, 1200 μg/L), which are within the recommended concentrations of application in aquatic compartments for blackfly and mosquito control. Besides invertebrate community structure and abundance, effects were evaluated regarding leaf decomposition and primary production as measures of ecosystem functioning. Community structure was significantly altered in all Bti treatments after 7 days of exposure, mostly due to a decline in chironomids, followed by oligochaetes, which both belong to the deposit-feeders’ functional group. Direct effects on oligochaetes are surprising and require further research. Also, reductions of leaf decomposition due to Bti-induced sublethal effects on shredders (reduced feeding) or mortality of chironomids (that can also feed on coarse organic matter) observed in our study, represent potential indirect effects of Bti in aquatic ecosystems. Our short-exposure experiment evidenced some negative effects on stream benthic invertebrate communities and on ecosystem functioning that must be considered whenever Bti is used in water bodies for blackfly or mosquito control programs.

Responses of benthic macroinvertebrate communities in tropical Asian streams passing through an industrial zone

ABSTRACT Industrial zones have been key drivers of growth across Asia but are also the source of water quality deterioration in surrounding rivers and streams. This study examined the effects of industrial zone located at the San Cristobal sub-catchment of Laguna de Bay, the Philippines on the spatiotemporal variation in water quality and benthic macroinvertebrate communities. Sampling sites were established in upstream and downstream sections of two tributaries of San Cristobal River, and the main channel of Diezmo River, and were sampled in 2018 during dry (February and April) and rainy (June and October) seasons. Results showed significant spatial difference with declining water quality (low dissolved oxygen; high levels of ammonia-nitrogen, phosphate-phosphorus, and total suspended solids) at the downstream sites. Consequently, benthic macroinvertebrates responded via change in community structure and composition (decline in pollution-sensitive taxa from upstream through downstream) to water quality degradation related to industrial land use downstream. Furthermore, seasonal variation was observed in benthic macroinvertebrate communities due to the absence of spate-induced disturbance, allowing benthic macroinvertebrates to proliferate in the rainy season. Findings of this study reveal that benthic macroinvertebrates can be used as bioindicators in the evaluation of the ecological integrity of surface river and stream systems that pass through industrial zones.

The response of benthic macroinvertebrate communities to environmental pressures in streams and rivers: A case study of Taihu and Chaohu Basins

为了解河流大型底栖动物对环境压力的响应关系，以人类干扰程度不同的太湖流域和巢湖流域为研究区，系统调查区域内河流大型底栖动物，结合水体、沉积物理化数据及生境质量状况，运用空间分析和多元统计分析等方法，探讨了大型底栖动物多样性及典型物种对关键环境因素的响应规律.结果表明，太湖流域和巢湖流域的环境质量和大型底栖动物群落结构均差异较大，巢湖流域的生境质量优于太湖流域，巢湖流域平原区部分点位的水体营养盐（特别是氮浓度）高于太湖流域平原区.巢湖流域丘陵区的敏感型物种（主要为水生昆虫）密度远高于太湖流域丘陵区，太湖流域丘陵区的耐污型物种（寡毛纲）平均密度稍高于巢湖流域丘陵区，而巢湖流域平原区的寡毛纲霍甫水丝蚓（Limnodrilus hoffmeisteri）和苏氏尾鳃蚓（Branchiura sowerbyi）平均密度远高于太湖流域平原区.广义加性模型建立的响应关系曲线表明，栖境多样性和总氮浓度可以作为生物多样性的指示因子.铜锈环棱螺（Bellamya aeruginosa）、椭圆萝卜螺（Radix swinhoei）、河蚬（Corbicula fluminea）、霍甫水丝蚓、苏氏尾鳃蚓、黄色羽摇蚊（Chironomus flaviplumus）等特征物种与特定环境因子的响应关系显著，这些物种也可以作为环境监测的指示物种.底栖动物-环境梯度的响应曲线能够定量地描述底栖动物群落对环境因子的响应关系，有利于深入了解水体水质、营养状态及生境质量与大型底栖动物群落结构的相关关系，进而预测不同人为干扰下大型底栖动物群落结构的变化趋势和演替过程.

Taxonomic and Functional Responses of Benthic Macroinvertebrate Communities to Hydrological and Water Quality Variations in a Heavily Regulated River

Aquatic macroinvertebrates are frequently used to evaluate river system conditions and restoration project performance. A better understanding of macroinvertebrate community responses to multiple stressors is a primary challenge for river science. In this paper, macroinvertebrate responses to hydrological and water quality variability were studied in the regulated Oglio River (northern Italy). We hypothesized that in regulated rivers the hydrological, rather than the physico-chemical conditions, would affect macroinvertebrate communities and biomonitoring tools (taxonomic metrics and functional indices). Repeated sampling (six times a year) was performed at four sites downstream of four dams in a 30 km river stretch during 2014 and 2015. Data were analysed using a linear mixed effect framework, to take into account random variation due to site and sampling date, and with multivariate analysis to track changes in community structure. A total of 69 families and 134,693 organisms were identified. The investigated metrics were mainly affected by the coefficient of variation of discharge, minimum discharge, ammonium, and temperature. The short-term dynamics of hydrological and physico-chemical variables were generally less important than the overall random effects as drivers of macroinvertebrate-based metrics. However, the relevance of a random effect (site, time, their interaction) differed depending on the biological metrics analysed. Understanding potential differences in response to short term and short stretch conditions would benefit biomonitoring and restoration procedures in both regulated and natural rivers.

Response of benthic macroinvertebrate communities to climate change

Aquatic ecosystems are impacted by climate change. However, the level of impacts, especially on macroinvertebrates, are not well known, which is the goal of this study. Here, three biotic indices were used. The Saginaw River Basin, the largest watershed in Michigan was selected for this study. Since no know modeling package exists to evaluate the impacts of climate change on these biotic indices, a coupled modeling approach was proposed. First, the Soil and Water Assessment Tool (SWAT) was setup to estimate streamflow and water quality for all stream segments. Next, the results from the SWAT model in combination with long-term biological monitoring data were used to develop biotic indices predictive models using a two-phase approach. An assemblage of 42 climate scenarios (2040–2060) were obtained from the National Aeronautics and Space Administration, which are biased corrected and statistically downscaled. The dataset provides two extreme Representative Concentration Pathways (RCPs) to account for best (RCP 4.5) and worst (RCP 8.5) case scenarios. The climate data were incorporated in SWAT and biotic indices predictive models to understand stream health conditions in the watershed. Results showed that the majority of streams have a probability of declining in values of biotic indices while streams that currently have excellent conditions are the most vulnerable streams to the climate change. This modeling approach provides a new mean to link more strongly biota indicators with flow regime indicators, which is of prime interest for the implementation of ecohydrology principles.

Macroinvertebrate community responses to duration, intensity and timing of annual dry events in intermittent forested and pasture streams

Intermittent streams comprise the majority of stream length in many parts of the world, particularly dry regions. Many dry regions are expected to experience longer and more intense dry periods as the global climate changes. The response of benthic macroinvertebrate communities in intermittent streams to current variability in dry-period duration and intensity may predict their future response to climate change, but such responses require quantification in different stream types and climate zones. I compared the macroinvertebrate community among drier and wetter years from 2008 to 2012 in intermittent forested and pasture streams in a relatively warm, dry region of New Zealand. I predicted that macroinvertebrate communities would decline in density and taxonomic richness with increasing dryness, and that drought-sensitive Ephemeroptera, Plecoptera and Trichoptera (EPT) taxa would show a stronger response than Diptera and non-insects. EPT richness and density did decline with increasing dry period duration, whereas total macroinvertebrate density and richness, and Diptera richness, showed weak and/or non-significant relationships. I predicted that loss of remnant pools (a potential dry-season refuge) would cause a decline in macroinvertebrate richness and density, but found no significant difference between years with and without pools. I predicted that years when flow resumed late in the autumn (when temperatures are too cool for insect flight) would have lower EPT richness and density than years when flow resumed early, and results confirmed this. Intermittent pasture stream communities showed a weaker response to dry period duration than communities in intermittent forested streams, as taxa relatively tolerant of agricultural stressors are also relatively tolerant of drying. Results suggest that global climate change will cause a loss of drought-sensitive species from intermittent streams in this region.

Spatial and temporal heterogeneity in a subtropical reservoir and their effects over the benthic macroinvertebrate community

AIM: The objective of the present study was to demonstrate the influences of the environment spatial heterogeneity on benthic macroinvertebrates considering transverse and longitudinal gradients as also seasonality. METHODS: Four samplings were performed: two in the wet and two in the dry season in the riverine, transitional and lacustrine zones in the littoral and profundal regions of Itupararanga reservoir, SP, Brazil. Abiotic characterization of the water and of the sediment was performed. The biotic characterization was based on richness, dominance, diversity, and density of organisms, as well as on the relative abundance of predominant taxa. Two-way ANOSIM analyses were performed for both biotic and abiotic components, in order to test the significance of the differences in the longitudinal and transverse directions as well as of the differences between seasons. RESULTS: Compartmentalization was present in both directions, longitudinal and transverse. In a general way, the littoral region presented higher diversity values when compared with the profundal region, and the riverine zone presented high densities and high percentage of taxons, which usually indicate organic pollution. The differentiation between the transitional and lacustrine zones was determined mainly by taxonomic composition. Seasonality was also observed and the transportation of small particles, the entrance of nutrients, and the presence of macrophytes were considered as determinants for differentiation. CONCLUSIONS: Together, these results demonstrate the responses of benthic macroinvertebrate communities considering distinct sources of variation: longitudinal heterogeneity, determined by the increasing distance from the forming rivers that leads to a gradient of physical and chemical conditions; transverse heterogeneity, determined by the proximity with the land environment and depth differences. Seasonal heterogeneity was recorded during the period of this research and it was determined by variations in water flow, in temperature, and in the carrying of matter, nutrients and organisms.

Characterizing differential responses of benthic macroinvertebrate communities to floods and droughts in three different stream types using a Self‐Organizing Map

ABSTRACTWe investigated the spatial and temporal changes of benthic macroinvertebrate communities in response to floods and droughts in three different stream types: perennial, intermittent, and ephemeral. Benthic macroinvertebrates were collected monthly (or biweekly) at six different sampling sites from July 2006 to January 2008. Species richness and abundance were extremely low at all sampling sites during the flooding period, but the communities subsequently recovered rapidly within 1 month. The effects of floods and droughts on benthic macroinvertebrates manifested differently among the three different stream types. Species richness and abundance had a negative relationship with the amount of precipitation in the perennial stream type, whereas no significant relationship was observed in the ephemeral stream type. A Self‐Organizing Map, an unsupervised artificial neural network, classified the samples into four clusters based on the similarities of community composition, reflecting the different effects of floods and droughts on the different stream types. Our results suggest that floods and droughts are the defining characteristics of streams, spatial heterogeneity (i.e. the perennial stream type) can decrease the effect of temporal heterogeneity, and both spatial and temporal heterogeneities are important for structuring the environmental condition and benthic macroinvertebrate assemblages. Copyright © 2012 John Wiley & Sons, Ltd.

Responses of benthic macroinvertebrate communities to altitude and geology in tributaries of the Sepik River (Papua New Guinea): the influence of taxonomic resolution on the detection of environmental gradients

Summary1. Benthic macroinvertebrate communities were sampled in 30 tributary streams at altitudes from sea level to about 3000 m draining three geologically distinct regions within the catchment of the Sepik River, Papua New Guinea. The fauna of this near‐pristine river has been little studied, and the impacts of ongoing and anticipated human impacts on the Sepik are uncertain.2. Data on community composition were analysed at different levels of taxonomic resolution (species or morphospecies versus family) to compare their responses to environmental variables such as altitude and geology (reflected in water chemistry), and to indicate their potential utility for the detection of environmental change.3. A total of 183 000 macroinvertebrates representing 250 species were collected, predominantly insects (232 species and >99% of individuals). The fauna was co‐dominated by Diptera (42% of individuals; 32 morphospecies, mainly Orthocladiinae, Simuliidae and Chironominae) and Ephemeroptera (36%; 48 species), although the Trichoptera showed the highest species (67) and family (13) richness, with Coleoptera ranked third (43 species). Naucoridae (Heteroptera) and Crambidae: Acentropinae (Lepidoptera), each represented by 13 species, were distinctive faunal elements. Mayflies were represented by only four families, one consisting of a single species.4. Multivariate analysis of the species‐level data set revealed that community composition was influenced by geological region, but the effect was largely due to altitude as most streams in one region (the Central Highlands) were at higher elevations (>800 m) than streams in the other two regions (<500 m). However, altitude had no direct effect on species richness. A secondary influence of current speed and a subsidiary effect of water chemistry (pH and N‐NO3) on community composition were also detected. Naucorid bugs showed evidence of altitudinal zonation and some species replacement, plus a tendency for certain genera to be associated with highland or lowland streams.5. Analysis of the family‐level data set failed to uncover strong effects of any environmental variable, either individually or in combination, although some sensitivity to altitude plus slope was detected.6. These findings suggest that attempts to use macroinvertebrates to detect environmental change in New Guinea streams will require species‐level monitoring of community composition.

The response of benthic macroinvertebrate communities to climate change: evidence from subtropical mountain streams in Central China

AbstractEcological effects of climate change on terrestrial and marine ecosystems are increasingly apparent but evidence from freshwater is scarce, particularly in Asia. Using data from two subtropical Central China streams, we predicted the changes of some benthic macroinvertebrate communities under various climatic scenarios. Our results show that the average annual air temperature, in the study watershed, increased significantly (P < 0.05) by 0.6 °C over the last 30 years (1978–2007), whereas the average annual water flow declined by 30.9 m3 s–1. Based on the winter sampling of benthic macroinvertebrates at four stream locations over last six years, we observed that macroinvertebrate abundance and Margalef diversity dropped with increasing water temperatures or decreasing smoothed sea surface temperatures (SSST). The winter macroinvertebrate abundance and biodiversity declined by 11.1% and 6.8% for every 1 °C water temperature rise. In contrast, increases in future SSST by one unit would increase winter macroinvertebrate abundance and biodiversity by 38.2% and 16.0%, respectively. Although many dominant taxa were predicted to persist when water temperatures increase by 1 °C, several scarce taxa, e.g., Orthocladius clarkei and Hippeutis umbilicalis, could be at a level of potential local extinction. Our identification of these links, between climate change and stream macroinvertebrate communities, has wide implications for the conservation of mountain stream ecosystems in the upper Yangtze River under scenarios of climate change. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Sedimentation effects on the benthos of streams and estuaries: a cross-ecosystem comparison

Connected ecosystems can be detrimentally affected by the same stressor, such as occurs when excess fine sediment moves from streams into estuaries. However, no previous study has directly compared sedimentation effects across these ecosystems. Responses of benthic macroinvertebrate communities to sedimentation were predicted to vary between streams and estuaries, because of intersystem differences in the physical environment and representation of species traits. To compare these responses, fine terrigenous sediment was added simultaneously to replicated plots in stream-run habitats and the adjacent estuary. Although sediment addition to streams caused reduced invertebrate densities after 1 week, no changes in taxon richness or consistent changes in community structure were detected, and densities had recovered another week later. In contrast, sediment addition to estuarine sites caused large declines in invertebrate densities and changes in community structure, which remained evident at the innermost sites 16 days after addition. Across both systems, sedimentation effects were detectable only for some of the common taxa, and biological traits were not predictive of effects. The potential for more severe effects in estuaries should be considered when predicting the implications of land-use changes that may increase sedimentation, and when setting guidelines for maintaining stream and estuarine condition.

Responses of benthic macroinvertebrate communities to natural geothermal discharges in Yellowstone National Park, USA

We examined responses of benthic macroinvertebrate communities to natural geothermal discharges in 32 streams in Yellowstone National Park (YNP), USA. Geothermal discharges played a major role in structuring benthic communities in YNP, as downstream communities were characterized by low species richness, reduced abundance of EPT taxa and increased abundance of tolerant caddisflies (Trichoptera), chironomids and non-insects. While some taxa were a subset of tolerant organisms that were also common at references sites, others (the damselfly Argia sp., the caddisfly Oxyethira sp. and the exotic New Zealand mudsnail Potamopyrgus antipodarum Gray 1843) were found almost exclusively in geothermal streams. Because geothermal waters are a common feature of YNP, monitoring programs designed to assess long-term status and trends of Yellowstone’s aquatic ecosystems must account for the influence of these discharges. To separate geothermal effects from other potential anthropogenic disturbances in YNP (e.g., atmospheric deposition, road construction, wastewater, global change), we developed a multimetric index based on responses of benthic communities to geothermal discharges. Streams were placed into one of four geothermal categories based on conductivity (reference = 600 μS/cm, respectively). The index clearly distinguished among these categories and showed a well-defined threshold response to geothermal effects at very low levels of conductivity. Although the index was specific to geothermal effects, the approach used to develop the index has broad applicability for other systems where impacts of stressors must be assessed within the context of natural environmental gradients. Our findings may provide important insights into how benthic macroinvertebrate communities respond to global change. Reduced discharge and warmer temperatures predicted for Rocky Mountain streams may favor the establishment and expansion of exotic species such as New Zealand mudsnails (P. antipodarum), which are highly tolerant of geothermal influences.

Response of benthic macroinvertebrate communities to highway construction in an Appalachian watershed

Highway construction in mountainous areas can result in sedimentation of streams, negatively impacting stream habitat, water quality, and biotic communities. We assessed the impacts of construction of a segment of Corridor H, a four-lane highway, in the Lost River watershed, West Virginia, by monitoring benthic macroinvertebrate communities and water quality, before, during, and after highway construction and prior to highway use at upstream and downstream sites from 1997 through 2007. Data analysis of temporal impacts of highway construction followed a Before-After-Control-Impact (BACI) study design. Highway construction impacts included an increase in stream sedimentation during the construction phase. This was indicated by an increase in turbidity and total suspended solids. Benthic macroinvertebrate metrics indicated a community more tolerant during and after construction than in the period before construction. The percent of Chironomidae and the Hilsenhoff Biotic Index (HBI) increased, while percent of Ephemeroptera, Plecoptera, and Trichoptera (EPT) decreased. Our 10-year study addressed short-term impacts of highway construction and found that impacts were relatively minimal. A recovery of the number of EPT taxa collected after construction indicated that the benthic macroinvertebrate community may be recovering from impacts of highway construction. However, this study only addressed a period of 3 years before, 3 years during, and 4 years post construction. Inferences cannot be made concerning the long-term impacts of the highway, highway traffic, runoff, and other factors associated with highway use. Continual monitoring of the watershed is necessary to determine if the highway has a continual impact on stream habitat, water quality, and biotic integrity.

Testing biotic indices for marine zoobenthos quality assessment in the Polish sector of the Baltic Sea

According to the EU Water Framework Directive (WFD), the status of coastal and transitional waters should be determined on the basis of phytoplankton, macrovegetation and benthic invertebrate classifications. A number of biotic indices have been designed to establish the ecological quality of European coastal waters based on the response of benthic macroinvertebrate communities to natural and man-induced changes in environmental conditions. Species richness and Shannon–Wiener (H′), simple indices characterising species abundance, distribution and diversity, as well as multimetric indices like Benthic Quality Index (BQI) and Benthic Coefficient (BC), which also incorporate the sensitivity/tolerance of species and taxa distribution, have been tested to evaluate macrozoobenthic communities at monitoring stations within the Polish zone of the southern Baltic Sea. The examined communities' locations differed as regards the spatial and temporal anthropogenic stress and the data series covers the period 1987–2005. BQI, developed for Swedish coastal waters of the south-eastern Baltic, has proved a promising tool for zoobenthos status evaluation also in Polish marine areas, showing responsiveness to environmental disturbance and regional differentiation. Ecological status classification using BQI showed good status of zoobenthos at shallow stations as being prevalent between 1987 and 2005. In the SE Gotland Basin between 1979 and 2005, a dramatic decline from good to poor status occurred around 1998.

Response of benthic macroinvertebrate communities to El Niño related drought events in six upland streams in south-central Ontario

We examined the effects of extreme drought events on benthic macroinvertebrate (BMI) community structure in six forested upland streams in south-central Ontario, Canada, during a 9-year period. Variation in the mean winter El Niño – Southern Oscillation Index was strongly correlated with drought conditions (zero flow days) in the study streams. Drought onset and duration varied among study streams and among years. Below-average precipitation coincided with the occurrence of drought, although it remains unclear if snowfall and rainfall contributed equally to the impact of decreased precipitation. Increased relative abundance of Ephemeroptera, Plecoptera, and Trichoptera (EPT) one year following drought and decreased relative abundance two years after drought indicated high resistance but poor resilience. In contrast, chironomids showed poor resistance and high resilience. Although these patterns were not consistent across all streams, temporal coherence among streams was found in percent EPT, percent chironomids, and percent dipterans, suggesting that drought acts as a disturbance mechanism that simplifies benthos community assemblages. Biocriteria developed from 22 nearby reference streams indicated that abnormal BMI communities occurred only after recurring episodes of drought, indicating that the effects of drought are cumulative. Headwater streams may prove to be sentinel ecosystems for monitoring the impacts of climate change.

Biological Monitoring: The Dilemma of Data Analysis

Biological Monitoring: The Dilemma of Data Analysis

Structural responses of benthic macroinvertebrate communities from different stream orders to zinc

AbstractIt is well established that benthic invertebrate community structure and function shift in a predictable fashion along longitudinal stream gradients as a result of variation in environmental conditions. Our research is concerned with experimentally testing whether this shift in community structure influences the response of benthic macroinvertebrates to heavy metals. Using artificial streams, we compared effects of Zn on natural assemblages of benthic macroinvertebrate communities collected from Little Beaver Creek (LBC; a third‐order stream) and the Big South Fork of the Cache la Poudre River (SFP; a fourth‐order stream) of the Cache la Poudre, Colorado, catchment. Organisms collected from LBC and SFP were exposed to 0 or 130μg/L Zn in indoor experimental streams for 7 d. In general, similar taxa were found at both sites, but densities were generally higher at SFP than at LBC. We observed significant effects at the community and population level as a result of Zn, stream order, and the interaction between Zn and stream order. Specifically, mayflies from both sites were sensitive to Zn, but the magnitude of the response varied between sites. Our results indicate that benthic macroinvertebrate communities from different stream orders may vary in sensitivity to Zn.