Avoidance Behavior of Ruffe Exposed to Selected Formulations of Piscicides

Ruffe were introduced into Duluth Harbor, Minnesota in the early 1980s, probably by release of ballast water from sea-going freighters. Since then, it has become the most abundant species in the fish community. The sensitivity of ruffe to a number of piscicides has been demonstrated, however, the feasibility of using piscicides to control populations depends on whether ruffe can detect piscicides and move to untreated water. We used a two-choice preference testing system to evaluate avoidance or attraction reactions of ruffe during exposures to the lampricides TFM and bayluscide and the general fish toxicants rotenone and antimycin. We used a second testing system to evaluate the potential for benthic ruffe to move vertically in the water column to avoid piscicides dissolving from experimental bottom-release formulations of bayluscide and antimycin. Near-lethal concentrations of TFM and rotenone tended to repel ruffe. Antimycin and bayluscide did not seem to repel ruffe in the avoidance chamber, but bottom-release formulations (antimycin granules—0.25% a.i. and bayluscide granules—3.2% a.i.) did cause increased swimming and surfacing activity among ruffe in column tests. We conclude that TFM and rotenone could be used to treat entire bodies of water, while bottom-release formulations of antimycin and bayluscide may have more application for treating localized concentrations of ruffe.     

Effects of hydropeaking on benthic invertebrate community composition in two central Norwegian rivers

Hydropower regulations can have dramatic impacts on river ecological communities. The operation of hydropower stations is related to power demands, but their releases in the receiving water body causes sudden changes in flow, which in turn affect the biota. The effects of such flow variations on benthic invertebrates is not fully understood. Here, we studied the effects of duration and intensity of hydropeaking on benthic invertebrates in two rivers over a 3.5‐year period. We used both quantitative (Surber) and semiquantitative (kick samples) sampling methods to compare the ramping zone with the permanently water covered zone downstream of the hydropower plant, and with corresponding unaffected upstream areas. The ramping zone had a different invertebrate community composition and lower benthic density than other areas, especially after hydropeaking. Mayflies and chironomids were most negatively affected by hydropeaking and oligochaetes largely unaffected. Chironomids and the mayfly Baetis rhodani were able to recolonize the ramping zone and almost reach densities similar to deeper areas within 48 days following hydropeaking. The relative abundance of filter feeders tended to increase and gatherers/collectors tended to decrease from the ramping zone towards the deep, permanently water covered areas. In corresponding areas upstream of the power plant, the relative abundance of different functional feeding groups was the same in the mid‐channel and shore sites. Our study shows that hydropeaking has clear impacts on the functional structure of benthic invertebrates below the power plants. The ecological impact of hydropeaking on invertebrate communities should thus be taken into account, for example, by reducing the amplitude and duration of flow fluctuations.     

Der Einfluss der Ufervegetation auf die Wassertemperatur unter gewässertypspezifischer Berücksichtigung von Fischen und benthischen Evertebraten am Beispiel von Lafnitz und Pinka

This study is based on the results of the transdisciplinary research project BIO_CLIC. The aim of this study was (1) to synthesize and reflect the scientific knowledge, (2) to understand the potential of riparian vegetation on water temperature and (3) to ameliorate the impacts on the aquatic habitats of benthic invertebrates and fish at the rivers Lafnitz and Pinka. These objectives had been achieved by detailed field investigations, the assessment of abiotic environmental parameters (water temperature, riparian vegetation, shading and morphology), the comparison of effects of dynamic processes (incl. water temperature, riparian vegetation, change of river morphology) and biotic habitat use of benthic invertebrates and fish assemblages. The results provide an environmental and biological overview of potential local impacts on water temperature during heat wave periods and additionally taking into account diverse climate scenarios. Three hotspots at each river were selected to characterize specific river types with respect to river morphology, riparian vegetation, thermal regime, as well as the biocoenosis of fish and benthic invertebrates. The temperature regime influences all life stages of fish species and benthic invertebrates. They prefer different temperature regimes along a river continuum that correspond with typical species assemblages. Our evaluation of water temperatures for longitudinal biozenotic zones showed significant differences for shaded and unshaded river reaches. The river type specific mean water temperature for trout and grayling zone in summer is between 11 °C and 16 °C and for barbel and nase above 16 °C. Temperature changes of 2 °C lead to a shift of species composition preferring ?warm-water“ species. River reaches with functioning riparian vegetation are able to mitigate these effects of extreme water temperature increase.     

Spatial and temporal trends in invertebrate communities of Great Lakes coastal wetlands,with emphasis on Saginaw Bay of Lake Huron

The shallow-sloping coastal bathymetry of Saginaw Bay (Lake Huron) supports broad fringing wetlands. Because benthic invertebrates form an important forage base for fish, wading birds, and waterfowl that utilize these habitats, understanding the drivers of invertebrate community structure has significant management implications. We used Great Lakes basin-wide data from 2002 to place Saginaw Bay wetland invertebrate communities and their environmental drivers into a basin-wide context. Various aspects of community structure were highly correlated with fetch and watershed agriculture across the basin. Saginaw Bay wetlands had relatively high fetch and watershed agriculture and supported unique invertebrate communities, typified by high abundances of many insect taxa. Wetlands from other regions around the basin tended to have more crustaceans and gastropods than the Saginaw Bay wetlands. A 1997–2012 time series from three representative Saginaw Bay wetlands revealed substantial shifts in community structure throughout the period, especially from 2001 through 2004. These years followed a 1-m decline in Lake Huron water levels that occurred between 1997 and 2000. Major community changes included decreasing insect abundance, especially chironomids, and increasing crustacean abundances, especially Hyalella azteca (Amphipoda). While factors in addition to water levels were likely also important, our time series analysis reveals the marked temporal dynamics of Saginaw Bay wetland invertebrate communities and suggests that water level decline may have influenced these communities substantially. Both the spatial and temporal community patterns that we found should be considered in future bio-assessments utilizing wetland invertebrates.     

PATTERNS OF BENTHIC INVERTEBRATE RICHNESS AND DIVERSITY IN THE REGULATED MAGPIE RIVER AND NEIGHBOURING NATURAL RIVERS

Fluctuating flows common in hydropeaking operations present biota with contrasting and challenging environments. Taxa that require a narrow range of water velocity or are not adapted to withstand sudden changes in discharge will likely be eliminated or competitively disadvantaged under such circumstances, perhaps leading to reduced biodiversity. I investigated the whole river, longitudinal and lateral patterns of benthic invertebrate abundance, Shannon–Wiener diversity, and rarefied taxa density and richness in the hydropeaking Magpie River and 16 neighbouring natural rivers. The Magpie River had greater abundances of benthic invertebrates than natural rivers, particularly near the dam. General differences in benthic community characteristics were largely based on the near absence of Odonata and Plecoptera and an abundance of snails and worms in the Magpie River. Family density, richness and diversity were greater in the regulated Magpie River and unregulated upper Magpie River than found in natural rivers. Longitudinally, family density, diversity and particularly richness increased downstream in the Magpie River. Laterally, diversity did not show any trends with increasing depth along transects, except at near the dam where it decreased sharply with depth, velocity, and an abundance of filter feeding invertebrates. Taxa density did not show any lateral trends in natural rivers, whereas in the Magpie River, it increased with water velocity and depth. The results of this study are contradictory to the general findings of others implying reduced biodiversity below hydropower facilities. Possible explanations are examined and contrasted with other examinations of benthic invertebrate response below hydropeaking dams. © Her Majesty the Queen in Right of Canada 2012.     

Invertebrate communities in Compensation Creek,a man‐made stream in boreal Newfoundland: The influence of large woody debris

Benthic invertebrate communities were examined in Compensation Creek, a man‐made stream in south‐central Newfoundland, Canada. Samples taken in September 2006 and September 2007 from large woody debris (LWD) were compared with samples from benthic environments to determine whether LWD supported a more diverse and abundant invertebrate community. Benthic habitats in a nearby natural stream were also sampled. Taxa composition was similar between the man‐made and the natural stream, highlighting successful colonization for the majority of taxa. Within Compensation Creek, taxa richness was higher in benthic habitats than on LWD, likely influenced by the successional age of the stream and surrounding habitat. The more complex benthic substrate provided refugia and allowed for the accumulation of fine detritus as a food source. Scrapers were almost completely absent from LWD and collector‐gatherer abundance was greater in the benthos. Collector‐filterer abundance was more than six times greater near the pond outflow than farther downstream when discharge was high, but abundances were almost equal when discharge was reduced. Riparian vegetation has not fully established around the man‐made stream, whereas it is overhanging and extensive at the natural stream, leading to more leaf‐litter input for shredders. As the morphology of Compensation Creek changes, the invertebrate community will continue to develop and likely increase utilization of accumulated detritus at LWD. Copyright © 2009 John Wiley & Sons, Ltd.     

Disturbance by aquatic plant management in streams: Effects on benthic invertebrates

The effect of aquatic plant removal on benthic invertebrates and their habitat was studied in two macrophyte-rich streams of the Swiss Plateau. In each stream, habitat conditions (macrophyte biomass, current velocity, water depth) and invertebrate densities were monitored in a control reach and in a reach where plants were removed by cutting. Biological samples were taken and physical parameters measured on three dates before and six dates after plant removal in both reaches. Responses to plant removal were similar in both streams; macrophyte cutting initially decreased mean plant biomass (ca. 85%) and total number of invertebrates (ca. 65%). Variation between replicates was, however, higher in one of the streams, causing fewer effects on plants and invertebrates to be statistically significant. Plant cutting affected mainly taxa that used macrophytes as habitat (e.g. Simuliidae, Chironomidae), whereas highly mobile taxa (e.g. Ephemeroptera) and taxa living on or within the bed sediments (e.g. Trichoptera, Bivalvia) were less affected. Taxa that decreased after plant removal recovered within 4–6 months, although recovery of macrophytes was quite different in both streams. Invertebrate recovery also seemed to be seasonally dependent, with cutting having a less severe impact during summer than spring. Our results suggest that macrophytes in streams should be removed only in summer, preferably leaving some plant beds to act as refugia for phytophilous invertebrates. © 1998 John Wiley & Sons, Ltd.     

Factors structuring macroinvertebrate communities in a headwater stream and its springs in the Upper Austrian Limestone Alps

The Almbach, a headwater stream in the Upper Austrian foothills of the Alps bordered by mountain pastures was studied to gain insight into the benthic macroinvertebrate community and its habitat. Two springs, one of them fenced in to prevent livestock access, and two more sites of the headwater section were investigated. A discriminant analysis (DA) based on hydrochemistry and phytobenthos revealed three functions with 86% of all samples correctly classified to the four sites. The first function clearly separated the two springs with phosphorus and oxygen as the most important discriminating factors. Spring sites and headwater sites were split up by the second function mainly due to nitrate concentration, but no differences could be detected for the two stream sites. With the exception of the fenced spring, indicator taxa could be assigned to all sites by means of an Indicator Species Analysis (ISA). Polyvalent taxa groups such as Gastropoda and Ostracoda were indicators for the unfenced spring site. This is in accordance to observed low abundances of sensitive plecopteran taxa and suggests a negative impact of livestock trampling on the invertebrate community. Redundancy Analysis explained 99% of the macroinvertebrate‐environment relation. The first axis separated springs from stream sites and was correlated with nitrate, pH, water temperature and phytobenthos eveness. Phosphorus was responsible for splitting the unfenced spring and the downstream station from the fenced spring and the upstream location along the second axis. Ephemeropteran taxa like Habrophlebia sp. were related to elevated pH, increased water temperature and low nitrate concentrations. In accordance to the ISA, nitrate played an important role for tolerant Gastropoda and Ostracoda at the unfenced spring. Copyright © 2010 John Wiley & Sons, Ltd.     

Assessing Contamination in Great Lakes Sediments Using Benthic Invertebrate Communities and the Sediment Quality Triad Approach

Sediments in many Great Lakes harbors and tributary rivers are contaminated. As part of the USEPA's Assessment and Remediation of Contaminated Sediment (ARCS) program, a number of studies were conducted to determine the nature and extent of sediment contamination in Great Lakes Areas of Concern (AOC). This paper describes the composition of benthic invertebrate communities in contaminated sediments and is one in a series of papers describing studies conducted to evaluate sediment toxicity from three AOC's (Buffalo River, NY; Indiana Harbor, IN; Saginaw River, MI), as part of the ARCS Program. Oligochaeta (worms) and Chironomidae (midge) comprised over 90% of the benthic invertebrate numbers in samples collected from depositional areas. Worms and midge consisted of taxa identified as primarily contaminant tolerant organisms. Structural deformities of mouthparts in midge larvae were pronounced in many of the samples. Good concurrence was evident between measures of laboratory toxicity, sediment contaminant concentration, and benthic invertebrate community composition in extremely contaminated samples. However, in moderately contaminated samples, less concordance was observed between the benthos community composition and either laboratory toxicity test results or sediment contaminant concentration. Laboratory sediment toxicity tests may better identify chemical contamination in sediments than many commonly used measures of benthic invertebrate community composition. Benthic measures may also reflect other factors such as habitat alteration. Evaluation of non-contaminant factors are needed to better interpret the response of benthic invertebrates to sediment contamination.     

Benthic Community Structure and Composition Among Rocky Habitats in the Great Lakes and Keuka Lake,New York

Benthic invertebrates were collected from 12 rocky sites in Lake Michigan, Lake Superior, and Keuka Lake, New York. Proportionate abundances of benthic components occurring in rock scrape (131 spp.) and pumped (167 spp.) samples (190 spp. total) were compared using coefficient of community (CC) and percent similarity of community (PSc). Pumped samples were judged better estimators of benthic community structure and composition than were rock scrape samples because they more thoroughly and instantaneously sampled the benthos. Rock scrape samples in particular were subject to loss of Amphipoda. Comparisons among sites using CC, PSc, and cluster analysis indicated two major clusters of sites, one dominated by Chironomidae and the other dominated for the most part by the amphipod Hyalella azteca. No water chemistry differences of biological importance were noted during the fall and no biological interactions, such as fish predation, could explain observed benthic community differences. The factor which best accounted for differences in the benthic community among sites was physical characteristics such as water temperature, shelter from excessive wave activity, and rock configuration. However, despite differences, the most remarkable feature among rock sites was their similarity since dominant taxa of Amphipoda, Chironomidae, Acarina, and to some extent Naididae, were quite predictable, although rank order of dominance changed from site to site. Similarity among sites was attributed to similar trophic conditions, while dissimilarity was attributed to physical characteristics acting within and upon each site.     

人工阶梯 深潭改善下切河流水生栖息地及生态的作用

本文通过野外试验研究了人工阶梯深潭对下切河流水生栖息地及生态的作用，试验河段位于西南山区的吊嘎河上150m侵蚀下切严重的河段，布置15级人工阶梯，对水流 (水深、流速、水面宽、流量)、河床底质、河床微地貌和水生底栖动物物种及数量变化进行了5个月监测。试     

Trophic interactions among algal blooms,macroinvertebrates, and brown trout: Implications for trout recovery in a restored river

Positive correlation between trout abundance and dissolved metal concentrations along the Upper Clark Fork River (UCFR; Montana, USA) have forced restoration practitioners to seek underlying causes of reduced fish density beyond heavy metal contamination. Throughout the river, nutrient enrichment and summer algal blooms may be hindering full recovery of trout populations. In this study, we evaluated the community structure and metal body burdens of benthic invertebrates and characterized existing trophic linkages between brown trout and dominant invertebrate taxa before and during summer algal blooms in a downstream reach of the UCFR where fish densities are low (20–30 trout/km), and where metal contamination is relevant but minimal compared with upstream. In spring, estimated invertebrate abundance was 1,727 ± 217 individuals/m² and dominated by Ephemerellidae and Baetidae families. During summer algal bloom, invertebrate abundance increased 15‐fold (20,580 ± 3,510 individuals/m²) mostly due to greater abundance of Chironomidae, Hydropsychidae, and Simulidae. Copper body burdens (130 ± 42 ppm) were higher than any other heavy metal regardless of season, but detectable concentrations of arsenic, cadmium, and lead were also found. A Bayesian mixing model combining metal burdens and stable isotopes showed that in the spring, trout of average size (355 ± 65 g) relied mostly on epibenthic taxa (Ephemerellidae and Hydropsychidae), contrasting with small (<100 g) and large (>400 g) trout relying heavily on Baetidae, a major component of invertebrate drift. Foraging segregation related to trout size did not occur during summer algal blooms, which may reflect increasing influence of benthic algal proliferation or indicate the indiscriminate use of pool habitats as thermal refugia over summer conditions by trout of different ages.     

Refugia and Local Controls: Benthic Invertebrate Dynamics in Lower Green Bay,Lake Michigan following Zebra Mussel Invasion

In many aquatic ecosystems benthic invertebrate abundance has increased following zebra mussel (Dreissena polymorpha) invasion. We examine the impact of zebra mussel density on the abundance and distribution of benthic invertebrates and postulate refuge from predation as a mechanism for the increases we found in some taxa. Benthic invertebrates in zebra mussel druses and in adjacent sediment samples were surveyed at sites in six locations representing various trophic conditions in lower Green Bay. Mean invertebrate density and taxa richness were significantly higher in the druses than in the adjacent sediment. Species diversity in the druses was inversely correlated to turbidity over the study area. Sediment samples were dominated by oligochaetes and chironomids. Amphipods were the most abundant taxa in most, but not all, of the druse samples. Other taxa present included leeches, hydra, mayflies, and caddisflies. The effectiveness of druses as refuge from predation for amphipods was investigated under laboratory conditions with various predators (perch, round goby, and rusty crayfish). In mesocosms, predation losses averaged 75% lower where zebra mussels were present. In the absence of mussels, predation loss to perch and round goby was 100% and 66% to crayfish. We conclude that the increased abundance of other invertebrates in druses in lower Green Bay may be due to increased refugia, however the assemblage composition at any given site varies with local conditions.     

Use of mesohabitat‐specific relationships between flow velocity and river discharge to assess invertebrate minimum flow requirements

The benthic macroinvertebrate community in the sixth order lowland River Spree (Germany) was investigated in order to assess ecological effects of a flow reduction. The benthic habitat was composed of visually distinguishable mesohabitats. Eight mesohabitats were delineated, Dreissena‐bank, unionid mussel bed, rip‐rap, coarse woody debris (CWD), alder roots, stable sand, shifting sand and mud. The mesohabitats differed in their physical structure and hydraulic nature. These functional habitats were partly inhabited by distinct invertebrate assemblages. The use of mesohabitat‐specific relationships between flow velocity and discharge seemed the most appropriate approach in order to assess the impact of flow reduction on lotic fauna. In combination with the species‐specific optima and tolerances for flow velocity, this approach can be used to develop a minimum flow level that mitigates the effects of flow reduction and enables the persistence of rheophilic invertebrates in their specific mesohabitat. Copyright © 2001 John Wiley & Sons, Ltd.     

Biodiversity characteristics of small high-altitude tropical man-made reservoirs in the Eastern Rift Valley, Kenya

The biodiversity characteristics in eight small (0.065–0.249 km²) public man‐made reservoirs in the central part of the Eastern Rift Valley, Kenya, were studied between 1995 and 1998. A total of 71 phytoplankton species belonging to approximately 50 taxa were identified. Chlorophytes and cyanobacteria dominated the crop. The dominant taxa included Botryococcus, Syunura, Microsystis, Anabaena, and Cosmarium. A total of over 40 zooplankton species were identified. The community was composed mainly of crustacea, rotifers and protozoa. The most dominant group was Keratella but Brachionus and Nauplius were equally abundant. The diversity and abundance of benthic invertebrates was not high, and only 18 species were identified throughout the study period with the range of species number being 1–7 per reservoir. The benthic fauna was mainly composed of Lumbriculidae and Chironomid worms. A total of six monthly bird counts found an average of 60 birds per reservoir, and a total of 49 species was identified. Ducks, geese and coots dominated the waterfowl, especially during the dry season. Large‐scale breeding by Black‐headed Heron (Ardea melanocephala ) and Little Egret (Egretta garzetta ) was observed in one of the sites, and other species were also breeding in the reservoirs. The population of waterbirds in reservoirs was closely related to the biomass of benthic invertebrates, and the findings of the study indicate that the structure and dynamics of life forms within small man‐made reservoirs can serve as excellent sensors and indicators of the state of watershed health.     

Benthic Invertebrates of the Nearshore Zone of Eastern Lake Huron,Georgian Bay,and North Channel

Samples of benthic invertebrates were collected by divers during 1980 from 86 stations in the nearshore zone (depths of 5 to 20 m) of Lake Huron, Georgian Bay, and North Channel. Six general categories of substratum were encountered: rock, gravel, hard clay, sand, silt/sand, and silt. Abundance of invertebrates varied with depth and substratum, ranging from 456 m^?2 to 45,701 m^?2. Clay and gravel usually supported the largest populations, rock the smallest. A total of 218 taxa were recognized, including a first record of the naidid Ripistes parasitica in the western hemisphere. With only a few exceptions, individual taxa were distributed throughout the study area. The most abundant groups were Nematoda, Oligochaeta, Mollusca, and Chironomidae. Ephemeroptera and Trichoptera occurred at 83% of 5 and 10-m stations. Nine communities of invertebrates were recognized on the basis of ordination analysis. Differences in community composition appeared to reflect degree of exposure to wave action and local geology. Comparison of these results with those of earlier studies illustrated the much greater efficiency achieved through direct sampling by divers. Estimates of invertebrate standing stocks were up to an order of magnitude greater in the present survey, and the variety of organisms was much greater since all types of substrata could be sampled. There were no indications of increased eutrophication or unusual environmental stress within the study area.     

Role of discharge and temperature variation in determining invertebrate community structure in a regulated river

This paper quantifies patterns of discharge and temperature variation in the regulated river Lyon and the adjacent, unregulated river Lochay (Scotland) and assesses the importance of these patterns for benthic invertebrate community structure. Invertebrates were sampled at sites in each catchment in autumn, winter and spring during the 2002–2003 hydrological year. Metrics were used to characterize the discharge and temperature regimes in the period immediately preceding invertebrate sample collection. Metric values were then used in a canonical correspondence analysis (CCA) of the invertebrate sample data, in order to assess the significance of individual metrics and the overall importance of flow and temperature variability for community structure. The variance in the invertebrate data explained by this CCA was compared to that from a CCA using a range of environmental data from the sites (stream‐bed algal cover, channel hydraulic, sedimentary and water quality characteristics). This comparison allowed assessment of the relative importance of environmental variables versus hydrologic and thermal regimes. Invertebrate communities in the Lyon were relatively poor and uneven, with Ephemeroptera, Plecoptera and Coleoptera poorly represented. Distinct site and seasonal clusters were evident in the CCA ordination biplots, with Lyon and Lochay sites separated in dimensions represented by geometric mean sediment size, water temperature and algal cover. The cumulative variance values from ordinations using the discharge and temperature metrics were consistently highest, suggesting that differences in invertebrate communities showed a stronger relation to patterns of discharge and temperature variability than to the broader suite of environmental conditions. Although there were marked thermal differences between sites, temperature metrics appeared no more important than discharge metrics in explaining differences in invertebrate community structure. A number of the temperature and discharge metrics appeared similarly important, suggesting that no one aspect of the hydrothermal regime was any more important than others in helping to understand differences in invertebrate community between the study sites. Copyright © 2007 John Wiley & Sons, Ltd.     

INFLUENCE OF ENVIRONMENTAL INSTABILITY OF GROUNDWATER‐FED STREAMS ON HYPORHEIC FAUNA,ON A GLACIAL FLOODPLAIN,DENALI NATIONAL PARK,ALASKA

Macroinvertebrate community distributions were investigated within the benthic and hyporheic zone of five groundwater‐fed streams, on a floodplain terrace, in a glacierized catchment in Alaska, in summer 2008. The streams were characterized by a distinct gradient in environmental instability and provided an opportunity to determine whether the local variability in environmental instability of groundwater‐fed streams (reflecting differences in lengths of groundwater flow pathways) are of sufficient magnitude and frequency to influence macroinvertebrate community distribution. Individual measures of surface‐water temperature, streamflow, streambed stability and sediment size were incorporated into a multivariate index of environmental instability (IEI), using principal components analysis. In the hyporheic zone, a logarithmic association was observed between macroinvertebrate diversity and IEI and a quadratic association between abundance and IEI. The increase in diversity along the gradient of instability reflected a greater evenness of taxa caused by reduction in abundance of Chironomidae, combined with an increase in abundance of several less dominant taxa (Limnephilidae, Empididae, Baetidae and Simuliidae). At the surface, a quadratic association between diversity and IEI was observed, consistent with the intermediate disturbance hypothesis. Chironomidae, Nemouridae and Empididae presented contrasting surface and hyporheic distributions, indicating use of the hyporheic zone as a refuge. Moreover, covariance in the surface and hyporheic distribution of Limnephilidae and Chloroperlidae suggested the use of the hyporheic zone as an extension of the benthic habitat. The data indicate that local variability in environmental conditions between groundwater‐fed streams is sufficient to induce differences in macroinvertebrate communities and in the response of individual taxa. Copyright © 2012 John Wiley & Sons, Ltd.     

How freshwater biomonitoring tools vary sub‐seasonally reflects temporary river flow regimes

Characterizing temporary river ecosystem responses to flow regimes is vital for conserving their biodiversity and the services they provide to society. However, freshwater biomonitoring tools rarely reflect community responses to hydrological variations or flow cessation events, and those available have not been widely tested within temporary rivers. This study examines two invertebrate biomonitoring tools characterizing community responses to different flow‐related properties: the “Drought Effect of Habitat Loss on Invertebrates” (DEHLI) and “Lotic‐invertebrate Index for Flow Evaluation” (LIFE), which, respectively reflect community responses to habitat and hydraulic properties associated with changing flow conditions. Sub‐seasonal (monthly) variations of LIFE and DEHLI were explored within two groundwater‐fed intermittent rivers, one dries sporadically (a flashy, karstic hydrology—River Lathkill) and the other dries seasonally (a highly buffered flow regime—South Winterbourne). Biomonitoring tools were highly sensitive to channel drying and also responded to reduced discharges in permanently flowing reaches. Biomonitoring tools captured ecological recovery patterns in the Lathkill following a supra‐seasonal drought. Some unexpected results were observed in the South Winterbourne where LIFE and DEHLI indicated relatively high‐flow conditions despite low discharges occurring during some summer months. This probably reflected macrophyte encroachment, which benefitted certain invertebrates (e.g., marginal‐dwelling taxa) and highlights the importance of considering instream habitat conditions when interpreting flow regime influences on biomonitoring tools. Although LIFE and DEHLI were positively correlated, the latter responded more clearly to drying events, highlighting that communities respond strongly to the disconnection of instream habitats as flows recede. The results highlighted short‐term ecological responses to hydrological variations and the value in adopting sub‐seasonal sampling strategies within temporary rivers. Findings from this study indicate the importance of establishing flow response guilds which group taxa that respond comparably to flow cessation events. Such information could be adopted within biomonitoring practices to better characterize temporary river ecosystem responses to hydrological variations.     

泰晤士河潮汐河段水温和水化学特性对无脊椎动物的影响分析

采用长系列数据，分析了影响泰晤士河潮汐河段生态状况的主要因素。1915～2006年的监测数据表明其生态状况经历了污染、恢复和稳定3个阶段，20世纪40-60年代是污染最重的时期，伴随着较高的水温、氨氮和生化需氧量以及较低的溶解氧含量，该时期少有底栖无脊椎动物的记录。自60年代以来，随着水质的恢复，无脊椎动物也逐渐增多，其数量的波动与水化学指标，尤其是溶解氧具有相关性。尽管1960年以前的无脊椎动物和水质资料缺失比较严重，但仍需彻底整理和分析所有数据，以便在以后的研究中建立水质指标与无脊椎动物群落间的定量关系。