Determining algal assemblages in oligotrophic lakes and streams: comparing information from newly developed pigment/chlorophyll a ratios with direct microscopy

1. Pigment analyses by high performance liquid chromatography (HPLC) are commonly used for determining algal groups in marine and estuarine areas but are underdeveloped in freshwaters. In this study, 15 characteristic pelagic algal species (representing five algal groups) of oligo‐ / mesotrophic lakes were cultured and pigment / Chl a ratios determined at three light intensities. 2. With the exception of cyanophytes, light treatment had little effect on pigment / Chl a ratios. This justifies the use of the same pigment / Chl a ratios during seasonal studies where light conditions may change. 3. The determined pigment / Chl a ratios were tested on seasonal samples from five oligo‐ / mesotrophic lakes and three streams using CHEMTAX software. Pigment ratios of both pelagic and benthic algal communities from the lakes and streams were analysed to determine whether the pelagic algae‐based ratios can be used for benthic algal communities. 4. HPLC combined with CHEMTAX was useful for identifying freshwater phytoplankton classes and for quantifying the abundance of phytoplankton groups. However, although correlations were significant for six of seven phytoplankton classes studied, they were weak and varied with season. 5. HPLC was valid for quantifying benthic diatom groups in stream samples, whereas for lakes more benthic algal groups were recorded with HPLC than with microscopy and correlations between the two methods were not significant. 6. The use of both HPLC and microscopy is recommended as a cost‐efficient method for analysing many samples. It is crucial, however, that the CHEMTAX software is calibrated with the correct information, and the user is aware of the limitations.     

Diversity of rotifers from northeastern U.S.A. bogs with new species records for North America and New England

In order to assess the effects of pollution on recruitment of brown trout (Salmo trutta f. fario L.) exposure experiments with brown trout early life stages were performed in two differently contaminated small streams near Stuttgart, southwest Germany, and in a control situation in the laboratory. Pollution in the more polluted stream is mainly due to effluents of municipal sewage treatment plants and to the influx of surface waters from areas of intense agriculture activity. Additionally, the water carries high particle loads, especially after rainfall events. Water quality of the less polluted stream is occasionally influenced by agriculture activity in the vicinity. For the exposure of trout early life stages incubators were used, which allowed frequent examinations without serious disturbance of the exposed organisms and thus the development could be monitored over time. Compared to the less polluted stream and the control, in the more polluted stream high mortality rates, the lowest hatching success, and lowest values for growth occurred. In the less polluted stream, mortality rates were comparably low in prehatching stages, but high in hatchlings and juveniles due to heavy infestations with protozoic ectoparasites Chilodonella cyprini (Moroff, 1902) and Ichthyobodo necator (Henneguy, 1883). However, pollution-related effects were not detected in this stream. Differences in developmental rates between the different treatments were correlated with different water temperatures in the two streams and the control. For the more polluted stream, previous studies have indicated embryotoxic potentials mediated by pollutants. The present study indicates that in this steam, additionally, fine solids which infiltrate stream gravels may seriously affect development of brown trout early life stages.     

Fish early life stage tests as a tool to assess embryotoxic potentials in small streams

Early life stage (ELS) studies with brown trout(Salmo trutta f. fario L.) andstone loach (Barbatula barbatula L.)were performed between 1995 and 2000 toevaluate embryotoxic potentials in twodifferently polluted streams in southwestGermany. With both species, semistatic exposureexperiments with water samples and sedimenteluates were conducted in the laboratory.Additionally, brown trout ELS tests wereperformed in flow-through systems in thesemi-field and in the field. Thus, differentlevels of complexity of environmentalconditions were addressed which allowed thestudy of effects of xenobiotic contamination,temperature, and sediments on the success ofembryonic development. Additionally, effects ofwater from the polluted stream on fertilizationof brown trout eggs were determined. In themore polluted stream, xenobiotics caused anembryotoxic potential for both brown trout andstone loach, and viability of exposed browntrout eggs was drastically reduced by suspendedsolids in the water which covered the eggs.Additionally, fertilization rates of browntrout eggs were significantly decreased inwater of the more polluted stream. In the lesspolluted stream, low water temperature andinfestations by protozoic ectoparasites causedmortality of embryos. In this stream, pollutionand sediment effects were not observed. Resultsmade evident that in the more polluted streamrecruitment of brown trout was drasticallyimpaired.     

An ecological study of amebas from a small stream in Northern Florida

Summary An ecological study of amebas in the Hogtown Creek, which serves as a water-shed for the northwest quadrant of the city of Gainesville, Florida, indicates that the species which inhabit the creek are those typical of slow-flowing, moderate to warm freshwater streams of slightly alkaline nature. The Creek is essentially an unpolluted rural stream at its source; but receives both industrial and civil pollution in its course through the city. In the course of its flow some seven miles beyond the major entry of pollution, it recovers, and becomes again a rural stream with little significant pollution. Amebas disappear from the creek at the point where industrial pollution enters, and are found again in small numbers at two to four miles downstream. Thereafter, in the course of another three miles, amebas appear in greater numbers. Active amebas were not found whenever the pH of the stream became acid, at whatever station. None of the species known to be acidophilous were seen, with the exception of Difflugia oblonga, which may be ubiquitous. Some indication is noted that certain amebas prefer waters of certain temperature range, particularly within the genus Difflugia. In that genus D. lobostoma, D. tuberculata, D. urceolata, D. amphora, D. oviformis and D. acuminata were present more often in waters above 21° C.; whereas D. oblonga, D. globulosa, D. corona, D. gramen, and D. elegans were more often present in waters at temperatures below 21° C. Both naked and testate rhizopods were more numerous at or near pH 7.6; and in general both naked and testate amebas were more numerous at temperatures slightly below 21° C. It is suggested that any species of ameba may have a more or less restricted range of tolerance to any particular physical factor in the environment, with a presumed optimum for each factor, resulting in the appearance and disappearance of various species as the factors vary.Supported by Research Grant NIH-E-1158.     

皖南凹耳臭蛙地理分布格局与生境选择

凹耳臭蛙(Odorrana tormota)是一种小型山溪蛙类,由于叫声独特,种内具有超声通讯功能而引起国内外相关专家的广泛关注。首次针对皖南凹耳臭蛙地理分布、生境选择以及人为干扰强度对种群密度的影响进行了研究。共调查了9县1区32条不同的山溪,发现其中的16个有凹耳臭蛙分布,除黄山区的香溪和浮溪具文献记录外,其余14个分布点均为首次报道。基于现存凹耳臭蛙分布点的水系关系,推测该物种在皖南的分布呈现出以青弋江、新安江和水阳江三大水系为纽带、间断分布的格局。对其中10个分布点222只凹耳臭蛙生境选择的统计结果表明,在夜晚活动周期内,该物种对乔木、灌木丛、草本植物、岩石、沙滩和倒伏朽木等不同生境的选择具有显著差异(F5,54=25.75,P0.001),栖息在草本植物和灌丛中蛙的数量明显多于栖息在其它几种生境类型中的蛙类。暗示溪流沿岸的草本植物和灌丛对该物种的生存和繁衍具有重要意义,乔木对其非活动周期的隐蔽可能具有不可替代的作用。根据人类活动对其栖息地破坏程度,将人为干扰程度划分为强、中和弱3种不同强度,对不同干扰强度下种群相对密度进行单因素方差分析。结果表明,中等干扰强度下的种群密度显著高于其它两种强度下的种群密度(F2,13=8.155,P=0.005)。推测适度的人为干扰可能增加了栖息地内昆虫的种类和数量,对蛙类的生存和繁衍更为有利。但随着人为干扰强度的增强,对溪流沿岸植被的破坏更为剧烈,种群密度显著下降。     

The water mites (Acari: Hydrachnidia) of streams in The Netherlands: Distribution and ecological aspects on a regional scale

The water mites of running waters in The Netherlands have been surveyed for the period 1987–1992. The aims were to investigate their present distribution, to make a comparison with historical data and to identify differences in water mite assemblages on a regional scale. The investigation covered 821 sites in eight different drainage areas. In spite of the scarcity of historical data, it may be concluded that in the course of this century about 40% of rheophilic water mites have become extinct. In canalized streams lentic species are dominant. In springs and spring streams, lotic species can survive, but the assemblages consist mainly of euryoecious water mite species.Multivariate techniques were used to show regional differences. These differences are mainly determined by stream hydraulics. The area of Zuid-Limburg can easily be demarcated by its relatively high number of rheophilic species. The man-made streams (sprengen) at the east side of the Veluwe area are characterized by a number of species which indicate undisturbed circumstances. The response of water mites to pollution of running waters is discussed.     

Algal epilithon and water quality of a stream receiving oil refinery effluent

Changes in epilithic algal communities colonizing introduced substrata were determined in a stream polluted with oil refinery effluent at Digboi (Assam, India). The number of algal taxa was reduced but the growth of blue-green algae, particularly two species ofOscillatoria, was encouraged. Epilithic biomass (as chlorophylla) also declined at polluted stations. The algal community of the upstream station was markedly different from the community occurring just after the confluence of effluent; however, the differences were gradually reduced downstream, indicating improvement in water quality. Of the various criteria tested for possible relationships with the level of pollutants, species richness, Shannon diversity and biomass showed significant relationships. The study demonstrates the usefulness of algal criteria for monitoring oil pollution in running waters.     

Leaf litter breakdown budgets in streams of various trophic status: effects of dissolved inorganic nutrients on microorganisms and invertebrates

1. We investigated the effect of trophic status on the organic matter budget in freshwater ecosystems. During leaf litter breakdown, the relative contribution of the functional groups and the quantity/quality of organic matter available to higher trophic levels are expected to be modified by the anthropogenic release of nutrients. 2. Carbon budgets were established during the breakdown of alder leaves enclosed in coarse mesh bags and submerged in six streams: two oligotrophic, one mesotrophic, two eutrophic and one hypertrophic streams. Nitrate concentrations were 4.5–6.7 mg L⁻¹ and the trophic status of each stream was defined by the soluble reactive phosphorus concentration ranging from 3.4 (oligotrophic) to 89 μg L⁻¹ (hypertrophic). An ammonium gradient paralleled the phosphate gradient with mean concentrations ranging from 1.4 to 560 μg L⁻¹ NH₄‐N. The corresponding unionised ammonia concentrations ranged from 0.08 to 19 μg L⁻¹ NH₃‐N over the six streams. 3. The dominant shredder taxa were different in the oligo‐, meso‐ and eutrophic streams. No shredders were observed in the hypertrophic stream. These changes may be accounted for by the gradual increase in the concentration of ammonia over the six streams. The shredder biomass dramatically decreased in eu‐ and hypertrophic streams compared with oligo‐ and mesotrophic. 4. Fungal biomass increased threefold from the most oligotrophic to the less eutrophic stream and decreased in the most eutrophic and the hypertrophic. Bacterial biomass increased twofold from the most oligotrophic to the hypertrophic stream. Along the trophic gradient, the microbial CO₂ production followed that of microbial biomass whereas the microbial fine particulate organic matter and net dissolved organic carbon (DOC) did not consistently vary. These results indicate that the microorganisms utilised the substrate and the DOC differently in streams of various trophic statuses. 5. In streams receiving various anthropogenic inputs, the relative contribution of the functional groups to leaf mass loss varied extensively as a result of stimulation and the deleterious effects of dissolved inorganic compounds. The quality/quantity of the organic matter produced by microorganisms slightly varied, as they use DOC from stream water instead of the substrate they decompose in streams of higher trophic status.     

Using indicators of fish health at multiple levels of biological organization to assess effects of stream pollution in southwest Germany

The health of fish populations and assemblagesin two degraded streams in south-westernGermany were investigated in order to validatethe use of biomarkers for the assessment ofsmall streams as part of the Valimar project.In the more severely polluted stream,recruitment was impaired and populationabundances were low. Extinction ofsite-specific species and appearance of nonsite-specific species has resulted in a shiftin the species composition from thatcharacteristic of unpolluted reference streams.In the less severely degraded stream, abundantrecruitment and relatively high densities ofadults indicated healthy, self sustaining fishpopulations. Missing species, however,indicated some effects of human influenceswithin the reference stream. The reproductivestatus of adult stone loach, Barbatulabarbatula, was not affected in any stream asreflected by normal production of eggs andreproductive behavior. Indices of energystorage differed between the investigated sitesbut could not be related to pollution. Theevaluation of biological integrity based onfish assemblages revealed that both sites inthe more severely impacted stream were in poorcondition. The two reference sites wereclassified in moderate and good condition,respectively. By excluding effects of migrationbarriers on the fish assemblage there was astronger correlation between chemical waterquality and biomarker responses. The resultsindicate the importance of assessing theeffects of pollution within the content oflongitudinal gradients in streams and theusefulness of measuring health effects overseveral levels of biological organization.     

Fish species richness and stream order in Washington State streams

Synopsis We sampled fish at pairs of sites of the same stream order on opposite sides of drainage divides in the Cascade Mountains and in the southwest portion of Washington state. Elevation, gradient, drainage area, and stream order were significantly correlated with number of fish species collected at a site. Elevation accounted for the greatest portion of the variation in number of species and stream order for the least, but in low gradient, low elevation streams, stream order was significantly related to number of species. Species richness was greatest in low elevation, low gradient, high order streams. Species richness of a site reflected species richness of the drainage: in paired comparisons, sites in a drainage with a richer ichthyofauna had more fish species than sites in a drainage with fewer species. Addition of species with increasing stream order occurred in most streams, but replacement was more frequent than in other studies relating fish to stream order. The apparently higher frequency of replacement in this study appeared to be a result of headwater introductions of brook charr, Salvelinus fontinalis, and a tendency for cutthroat trout, Salmo clarki, to occupy headwaters when in freshwater.     

The use of Callitriche for water quality determination can be misleading: An example from the Po Valley in Northern Italy

In the context of the European Water Framework Directive (2000/60), aquatic macrophytes have become important elements for ascribing the correct ecological value to water systems. Callitriche includes macrophyte species which are widespread and particularly sensitive to environmental cues. High plasticity and morphological variability of these plants have carried to great difficulties in their correct taxonomic determination. Diverse populations of Callitriche of the Po Valley (Northern Italy) have been studied. Plants of Callitriche spp. were collected in Northern Italian rivers with mesotrophic and eutrophic waters and their morphological, karyological, and molecular features were analyzed. Populations with a different chromosome number equal to 10, 18, or 20 were found. Chloroplast rbcL DNA showed the presence of three different sequences. Moreover, the presence of heterozygous rDNA-ITS sequences suggests the existence of a considerable number of hybrids. At ecological level, only one taxon lives in eutrophic waters, while all the others live in mesotrophic ones. Different morphological characters and chromosome set suggest the presence of a new taxon among Italian Callitriche populations. In conclusion, this research underlines that the possibility of Callitriche taxon misclassification, using only the “canonical” macro-morphological approach, is significant and that the incorrect determination of these plants would lead to erroneous evaluation of water quality.     

Pathogenic and Nonpathogenic Acanthamoeba spp. in Thermally Polluted Discharges and Surface Waters1

During spring and autumn, the total number of amoebae and the number of Acanthamoeba species able to grow at 37°C were determined in six thermally polluted factory discharges and the surrounding surface waters. The isolated Acanthamoeba strains were studied for growth in axenic medium, cytopathic effect in Vero cell cultures, and virulence in mice. Although more amoebae were isolated in autumn, the number of Acanthamoeba species was lower than in spring, when the percent of pathogenic strains among the isolates was highest. Higher concentrations of amoebae were found in warm discharges, and more virulent strains occurred in thermal discharges than in surface waters.     

Emergence of blackflies (Diptera: Simuliidae) from a small forested stream in Ontario

Three species of blackflies were found in emergence-trap samples taken overa period of 8 months from a second-order, forested, cold-stenothermal stream in southern Ontario. The emergence phenologies of the two common species, Prosimulium mixtum and Stegopterna mutata, are described and compared with their phenologies in other streams in North America. Hypotheses are presented for the poor faunal diversity and prolonged emergence of the two species in the stream studied. Emergence data are used to describe the pupal distribution in the stream.Wing-length measurements showed a distinct dimorphism in P. mixtum: females were larger than males. Adult size (except of P. mixtum females) varied among sampling sites in the stream and, in the case of S. mutata, this variation was time dependent.     

Drift of ostracod crustaceans in adjacent intermittent and permanent streams

Ostracods were studied in the drift of adjacent permanent and intermittent streams in Southern Ontario. More species were drifting in the permanent stream than in the intermittent one. The latter developed a pool fauna during early summer and stagnant water species were predominant. Both standing and running water species were common in the permanent stream. Eleven were recorded in the drift and all but one of them are strong swimmers. I. bradyi, the only poor swimmer usually lives among vegetation and it is suggested that truly herpobenthic ostracods are less subject to drift than the others. The pattern of ostracod drift over a period of 13 months in those streams was different. The numbers drifting at the upstream and downstream stations of the same stream in a given month was variable. Ostracods were the major component of crustacean drift in both streams. Stream drift is considered as a mechanism of ostracod dispersal.     

Alterations of selected metabolic enzymes in fish following long-term exposure to contaminated streams

In order to assess the suitability ofalterations in activities of selected metabolicenzymes as biomarkers of chemicalcontamination, juvenile brown trout (Salmotrutta f. fario) and adult loach (Barbatula barbatula) were exposed to nativesurface waters from Krähenbach andKörsch, two differently polluted smallstreams in Southern Germany. As biomarkers ofexposure, a set of metabolic enzymes comprisinghexokinase, phosphofructokinase,glucose-6-P-dehydrogenase, malic enzyme,cytochrome c oxidase, succinate dehydrogenase,citrate synthase, alanine aminotransferase,esterase, superoxide dismutase, catalase, acidphosphatase as well as acetylcholinesterase(brain) were measured by means of establishedenzyme assays. In parallel studies, loach andbrown trout sampled from corresponding fieldsites were investigated to elucidate therepresentativeness of a stream bypass system.Although the episodic exposure scenarios ineither natural stream resulted in considerablevariability of enzyme activities, biochemicalchanges in both species allowed a cleardiscrimination between the two differentlypolluted streams. Similarities in changes ofenzyme activities between fish exposed in thebypass system and the field reached levels of63% and 73.1% in brown trout and loach,respectively. In conjunction with biomarkersfrom other studies, alterations in metabolicenzyme activities were able to serve as a toolfor the sensitive identification ofenvironmental pollutants, which in turn form fromthe basis for an improved understanding ofunderlying toxic processes and an interpretationof toxicant-related effects.     

Impact of nutrient enrichment and alkalinization on periphyton communities in the New Jersey Pine Barrens

The impact of residential and agricultural development on stream periphyton communities in the New Jersey Pine Barrens was examined by comparison with communities in undeveloped areas. Watershed disturbance resulted in stream water primarily characterized by greatly elevated pH levels and nitrate concentrations. A total of 53 periphyton species were encountered in bimonthly samples over a one year period in the three disturbed and three undisturbed study streams. Species richness was significantly greater in the disturbed streams based on three criteria: the average number of species per stream on each sampling occasion (disturbed = 6.3; undisturbed = 4.9), the average number of species per stream for the entire year (disturbed = 19.3; undisturbed = 16.0), and the total number of species found in streams within a type (disturbed = 40; undisturbed = 31). Species composition also changed significantly as the result of disturbance. There appeared to be replacement of species characteristic of undisturbed Pine Barrens streams with species peripheral to the region. The expected effects of both elevated pH and nitrate were consistent with these results.     

Abundance of Three Bacterial Populations in Selected Streams

The population sizes of three bacterial species, Acinetobacter calcoaceticus, Burkholderia cepacia, and Pseudomonas putida, were examined in water and sediment from nine streams in different parts of the United States using fluorescent in situ hybridization (FISH). Population sizes were determined from three sites (upstream, midstream, and downstream) in each stream to compare differences in the occurrence and distribution of the species within each stream and among streams. Physical and chemical variables measured reflected differences in environmental conditions among the streams. In the water, B. cepacia numbers were highest in the agricultural, Iowa stream. P. putida numbers were highest in the southern coastal plain streams, Black Creek (GA) and Meyers Branch (SC). Compared to the other two species, the abundance of A. calcoaceticus was similar in all the streams. In sediment, the greatest abundance of all three species was found in the Iowa stream, while the lowest was in Hugh White Creek (NC). Detrended correspondence analysis (DCA) explained 95.8% and 83.9% of the total variation in bacterial numbers in water and sediment of the streams, respectively. In sediments and water, B. cepacia numbers were related to nitrate concentrations. A. calcoaceticus in water clustered with several environmental variables (i.e., SRP, pH, and conductivity) but benthic populations were less well correlated with these variables. This study reveals the potential influence of various environmental conditions on different bacterial populations in stream communities.     

Macroinvertebrate/sediment relationships along a pesticide gradient in Danish streams

Twenty-nine Danish streams were investigated in September 1998. The streams drained catchments of varying hydrology, topography, soil type and land use. In each stream, the newly accumulated streambed sediment was sampled and subsequently analysed for pesticides. In each stream, five replicate macroinvertebrate samples were taken in the same sediments as the pesticide samples. In addition, five samples were taken in riffles to provide a complete picture of macroinvertebrate community composition. The number of detected pesticides reflected soil type and land use: in agricultural catchments on clay soils the average number of pesticides were 4.3±2.2; on sandy soils 2.6±1.0, while only 1.5±0.6 pesticides were found in streams without agricultural activities. The macroinvertebrate composition showed clear changes along this gradient of sediment pesticide concentrations. The number of the amphipod Gammarus pulex was negatively correlated with sediment pesticide concentration, while the number of Oligochaeta and Hirudinae was positively correlated. The findings indicate that pesticides have a potential to structure macroinvertebrate communities in Danish streams. However, agricultural impact is more than pesticides, and several other factors, such as channelisation, affect the macroinvertebrate community and these are not easily separated.     

Flow intermittency alters longitudinal patterns of invertebrate diversity and assemblage composition in an arid‐land stream network

1. Temporary streams comprise a large proportion of the total length of most stream networks, and the great majority of arid‐land stream networks, so it is important to understand their contribution to biotic diversity at both local and landscape scales. 2. In late winter 2010, we sampled invertebrate assemblages in 12 reaches of a large arid‐land stream network (including perennial and intermittent headwaters, intermittent middle reaches and perennial rivers) in south‐east Arizona, U.S.A. Intermittent reaches had then been flowing for c. 60 days, following a dry period of more than 450 days. We sampled a subset of the perennial study reaches three more times between 2009 and 2011. Since intermittent reaches were dry during these additional sampling periods, we used assemblage data from two other intermittent streams in the study network (sampled in 2004–05 and 2010) to explore interannual variability in intermittent stream assemblage composition. 3. Invertebrate richness was lowest in intermittent reaches, despite their often being connected to species‐rich perennial reaches. The assemblages of these intermittent reaches were not simply a subset of the species in perennial streams, but rather were dominated by a suite of stoneflies, blackflies and midges with adaptations to intermittency (e.g. egg and/or larval diapause). On average, 86% of individuals in these samples were specialists or exclusive to intermittent streams. Predators were 7–14 times more abundant in perennial than in intermittent reaches. 4. Despite being separated by long distances (12–25 km) and having very different physical characteristics, the assemblages of perennial headwaters and rivers were more similar to one another than to intervening intermittent reaches, emphasising the prime importance of local hydrology in this system. 5. The duration and recurrence intervals of dry periods, and the relative importance of dispersal from perennial refuges, probably influence the magnitude of biological differences between neighbouring perennial and temporary streams. Although perennial headwaters supported the highest diversity of invertebrates, intermittent reaches supported a number of unique or locally rare species and as such contribute to regional species diversity and should be included in conservation planning.     

Environmental effects on species richness of macrophytes in Slovak streams

The effect of 19 environmental variables on species richness of macrophytes was studied in 39 Slovak streams. The studied streams were poor in species; in total, 88 macrophyte taxa were found and the average number of macrophytes per sampling site was 4, ranging from 0 to15. The most frequently occurring macrophytes were filamentous algae (occurrence at 38.6% of sampling sites), followed by Rhynchostegium riparioides (28.4%) and Phalaris arundinacea (19.3%). The strongest environmental gradient in the sampling site detected by factor analysis (factor 1 explains more than 32% variability) is related to the portion of artificial banks, shading by woody vegetation along banks, flexuosity of stream course and the portion of natural land cover in the contact zone of the stream, and can be interpreted as a natural-anthropogenic gradient. The following variables had the highest correlations with species richness of macrophytes: shading by woody vegetation (r=?0.507), portions of artificial bank (r=0.488), flexuosity (r=?0.457) and distance from stream source (r=0.388).