bluuebunny/crossref_metadata_2025_split huggingface dataset:
Drift dispersal of mayfly nymphs in the presence of chemical and visual cues from diurnal drift‐ and nocturnal benthic‐foraging fishes
Authors: Miyasaka Hitoshi , Nakano Shigeru 
Published: March 2003

1. The drift of Baetis thermicus nymphs in the presence of chemical, visual and hydrodynamic cues, considered individually and in combination, produced by different predatory fishes was examined experimentally in laboratory streams. Masu salmon (Oncorhynchus masou) and freshwater sculpin (Cottus nozawae) are typical drift‐ and benthic‐foraging fishes, respectively.2. Observations of fish swimming in the streams revealed differing diel periodicity between the species; sculpin were nocturnal foragers and salmon diurnal.3. The drift rate of Baetis by night increased in the presence of chemical cues from sculpin, with other cues having no interactive effects. In contrast, the drift rate increased primarily in the presence of both chemical and, particularly, visual cues from salmon, although no additional effects were found for any non‐visual cues. Visual cues could enable Baetis to assess precisely the predation risk from foraging salmon by day, whereas Baetis could not use visual cues to detect sculpin either at night, because of the low light intensity, or during the day, because of the low activity of sculpin at that time.4. In natural streams, which are often inhabited by several predatory fish employing different modes of foraging, invertebrates may be able to precisely assess the risk and effectively to avoid predators by using cues unique to each.
Under‐ice blooms and source‐water odour in a nutrient‐poor reservoir: biological, ecological and applied perspectives
Authors: Watson S. B. , Satchwill T. , Dixon E. , Mccauley E. 
Published: March 2003

1. Algal taste and odour is usually associated with open water blooms and eutrophic systems. However, some algal species can produce high biomass under ice‐cover, even at low nutrient concentrations, that can impact water quality. This paper describes a winter odour outbreak in oligotrophic Glenmore Reservoir (Calgary, Alberta, Canada), the major algal species, volatile organic compounds (VOCs) and some treatment implications.2. Using sensory, chemical and microscope analyses, we monitored odour, algal biomass and taxa, bacteria and major nutrients. In a preliminary assessment of the effectiveness of standard water treatment with this type of algal biomass and odour, we used bench‐scale tests and sampled raw water from the Glenmore treatment plant at successive treatment stages.3. In the winter of 1999–2000 Glenmore ice‐cover was delayed, nutrients were characteristically low (TP < ∼5 μg L–1), but organic carbon and bacteria were higher than in previous years.4. During this period there was an increase in algal biomass dominated by the mixotrophic chrysoflagellate Dinobryon divergens. Temporal dynamics of this species were inversely correlated with bacteria, and biomass declined following the establishment of ice‐cover, while depth profiles showed the highest abundance at subsurface layers. This suggested that the population outbreak was triggered by high bacteria abundance but depended on a minimum amount of light, consistent with in vitro studies of other mixotrophic chrysophytes.5. Other non‐bactiverous taxa were also numerous, notably Asterionella formosa, cryptomonads, dinoflagellates and the synurophyte Synura petersenii.6. Raw water odour was characteristically fishy, mainly caused by the VOCs 2,4,7‐decatrienal, 2,4‐heptadienal and 2,4‐decadienal. Based on algal population and VOC dynamics, these compounds were attributed to Dinobryon. Trace amounts of 2,6‐nonadienal (S. petersenii) and 1,3,5 and 1,3,6‐octatriene (A. formosa) were also detected. It was concluded that 2,4,7‐decatrienal was the major source of the raw water odour.7. Sensory and microscopic analyses of pre‐ and post‐treatment samples in the treatment plant indicated a complete removal of odour, but only a 30–60% removal of algal biomass and evident rupture of residual algal cells. Laboratory experiments showed that using standard treatment, chlorination rapidly oxidized 2,4,7‐decatrienal and 2,6‐nonadienal but had little effect on 2,4‐hepta‐ and decadienal.
Longitudinal distribution of macroinvertebrates in two glacier‐fed New Zealand rivers
Authors: Milner Alexander M. , Taylor Russell C. , Winterbourn Michael J. 
Published: March 2003

1. Environmental variables, benthic algal biomass and macroinvertebrate fauna were examined from September 1999 to January 2000 (austral summer) along two glacier‐fed rivers in South Island, New Zealand.2. The rivers were characterized by high flow variability, high turbidity and physically disturbed beds. Water temperature ranged from <1 °C near the glacier margin to 10 °C further downstream.3. Epilithic algal biomass was very low (<0.1 mg m–2) in months characterized by heavy rainfall, but ranged from 1.1 to 14.4 mg m–2 following an extended period with negligible precipitation.4. Abundance and diversity of invertebrates in both rivers was low. Dominant taxa were Chironomidae (Orthocladiinae, Podonominae, Diamesinae), although mayfly species (Deleatidium: Leptophlebiidae) also occurred at most sites. A species of Eukiefferiella (Orthocladiinae) was collected at all sites and was the most abundant invertebrate close to the glacier margins. No meiofauna were found in either river.5. Faunal diversity increased at the lowermost stations where species of Plecoptera, Trichoptera, Coleoptera and non‐chironomid Diptera also occurred.6. The faunas of the two New Zealand rivers conformed to the conceptual model of Milner & Petts (1994) in that taxon richness increased downstream with water temperature. However, invertebrate abundance increased downstream in only one of the two rivers. Also in contrast to the model predictions, Leptophlebiidae and Orthocladiinae, rather than Diamesinae, dominated the fauna at the coldest sites.
Invertebrate drift in a glacial river and its non‐glacial tributary
Authors: Saltveit S. J. , Haug I. , Brittain J. E. 
Published: March 2003

1. Invertebrate drift was studied in a glacially fed river and a non‐glacial tributary in western Norway. Samples were taken during two consecutive 24‐h periods in May, July and October 1997. The 3 months are characterized by snowmelt, ice melt and rainfall runoff, respectively. The main glacial river has colder, more turbid water, especially during the period of maximum ice melt during summer.2. Chironomidae, especially the genus Diamesa, dominated the drift in the main river in May and October, constituting 97 and 99% of total numbers, respectively. Simuliidae, Plecoptera, Ephemeroptera and Trichoptera were the other main components.3. A comparison of drift and benthos data revealed that the tributary was of little significance for colonization of the main glacial river. Only some additional species in very low numbers were recorded downstream of the confluence.4. During July significant differences in diel drift pattern of Chironomidae and Simuliidae existed between the glacial and non‐glacial reaches. There was a mid‐day peak independent of discharge in the glacial river, but this peak was not noted in the tributary. Species of the genus Diamesa appear to be adapted for daytime drift, possibly evolved through the absence of predators and competitors that are typical of rhithral systems where nocturnal drift is more usual.
Direct and indirect impact of two common rotifer species (Keratella spp.) on two abundant ciliate species (Urotricha furcata, Balanion planctonicum)
Authors: Weisse Thomas , Frahm Angela 
Published: March 2003

1. We investigated the potential competition and feeding impact of the common rotifer species, Keratella cochlearis and K. quadrata, on the abundant prostomatid ciliates, Urotricha furcata and Balanion planctonicum, in laboratory batch culture experiments. All four species have similar feeding preferences, co‐occur in many freshwater environments, and are thus potential competitors for the same algal food.2. Two small Cryptomonas species served as food for the ciliates and the rotifers in the experiments. Growth rates of each ciliate species were measured when they grew alone and when they were paired with one of the rotifer species.3. Both rotifer species reduced the growth rate of U. furcata, probably primarily by direct feeding on the ciliates. Growth rate of B. planctonicum was unaffected by K. cochlearis, but was drastically reduced by grazing and/or mechanical interference of K. quadrata.4. These results suggest niche partitioning of the sympatric ciliates with respect to their rotifer competitors/predators.
Changes in abundance, composition and controls within the plankton of a fertilised arctic lake
Authors: Bettez Neil D. , Rublee Parke A. , O'Brien John , Miller Michael C. 
Published: March 2003

1. An oligotrophic arctic lake was fertilised with inorganic nitrogen and phosphorus as (NH4)2 NO3 and H3PO4 for five summers. The loading rate was 1.7–2.5 mmol N m–2 day–1 and 0.136–0.20 mmol P m–2 day–1 which is two to three times the annual loading of lakes in the area. The heterotrophic microzooplankton community was enumerated during the experiment as well as 1 year pre‐ and post‐treatment.2. The structure of the microplankton community changed from a nutrient limited system, dominated by oligotrich protozoans and small‐particle feeding rotifers, to a system dominated by a succession of peritrich protozoans and predatory rotifers. These peritrich protozoans and predatory rotifers were not present prior to fertilisation and never constituted more than a small fraction of the biomass in other lakes at the research site. The average biomass of the rotifers and protozoans was more than seven and a half times larger by the end of fertilisation than it was initially.3. Because of the increases in numbers of individuals in these new taxa, the structure of the microbial food web changed. When fertilisation stopped, most parameters returned to prefertilisation levels within 1 year.
The use of AUSRIVAS predictive models to assess the response of lotic macroinvertebrates to dams in south‐east Australia
Authors: MARCHANT R. , HEHIR G. 
Published: March 2003

1. Sites immediately below seven dams in Victoria and 12 in southern New South Wales (NSW) were sampled for macroinvertebrates using rapid bioassessment techniques. Specimens were identified to the lowest taxonomic level. The dams had different operating and discharge regimes and thus potentially different downstream effects on this fauna.2. The AUStralian RIVer Assessment Scheme (AUSRIVAS) predictive models for macroinvertebrate composition were applied to the families and genera observed at Victorian sites and to the families only at the NSW sites. Lists of predicted taxa, their probabilities of occurrence and ratios of observed to expected taxa (O/E scores) were obtained from these models.3. The mean O/E score for Victoria was 0.46 at the genus level and 0.63 at the family level; for NSW the mean score at the family level was 0.62. There was no significant difference between family level scores for the two states. Thus about 40% of expected families were missing at all sites. Family level scores were highly correlated (r=0.84–0.86, P < 0.001) with numbers of families or species at a site.4. There was no correlation between family O/E scores (or family and species richness) and the degree to which current discharge levels below a dam differ from the natural patterns. Thus increased hydrological deviation did not result in greater biological degradation. In addition, there was no association between these biological characteristics and whether dams released surface or bottom water.5. All the dams seemed to cause much the same disruption to the fauna. Of the families predicted to have widespread occurrence, 9–12 were found at most sites (tolerant taxa), while a larger number (14–24) were missing (intolerant taxa). The limited recolonisation below dams may well be because of the fact that dams act as barriers to drift, the most prominent route for invertebrate colonists.
Ferox Trout (Salmo trutta) as `Russian dolls': complementary gut content and stable isotope analyses of the Loch Ness foodweb
Authors: GREY J. , THACKERAY S. J. , JONES R. I. , SHINE A. 
Published: March 2003

1. Conventional collection methods for pelagic fish species (netting, trawling) are impractical or prohibited in Loch Ness, U.K. To investigate trophic relationships at the top of the Loch Ness food web, an alternative strategy, angling, provided samples of the top predator, the purely piscivorous ferox trout (Salmo trutta).2. The gut contents of these fish provided further samples of prey‐fish, and subsequent examination of prey‐fish guts revealed their dietary intake, analogous to the famous nested `Russian dolls'. Each trophic level separated by gut content analysis provided further complementary samples for stable isotope analysis and thus information on the longer term, assimilated diet.3. Ferox trout exhibited considerable cannibalism to supplement a diet of Arctic charr (Salvelinus alpinus). However, conspecifics stemmed from a lower isotopic baseline in relation to charr, so ferox trout exhibited a lower trophic level than predicted (4.3) by using the δ15N values. Charr displayed dietary specialisation with increasing length, and isotopic values supported by the gut data placed the charr at a trophic level of 3.5. The isotope data also indicated that charr carbon was primarily autochthonous in origin.
Simple predictions of instream habitat model outputs for target fish populations
Authors: LAMOUROUX NICOLAS , CAPRA HERVÉ 
Published: March 2003

1. Bottom‐up approaches based on individual behaviour can help to identify key variables influencing populations at larger scales. Instream habitat models have been developed to predict the consequences, for populations in stream reaches, of fish preferences for particular hydraulic conditions observed at the scale of individuals. Conventional instream habitat models (e.g. PHABSIM) predict habitat values for species or life stages in reaches, and their changes with discharge. Despite their worldwide use, they have been subject to continuing criticism and have been mainly limited to site‐specific case studies.2. We ran conventional instream habitat models in 58 French stream reaches dominated by brown trout. Using non‐linear mixed effect models, we demonstrated that the outputs of instream habitat models (habitat values for three trout life stages and five other species) are predictable from average characteristics of reaches (discharge, depth, width and bed particle size).3. Our models closely reflect variations in habitat values within‐reaches (with discharge) and between‐reaches. Within‐reach changes are linked to the Reynolds number of reaches, while between‐reach changes depend mainly on the Froude number at median daily discharge. These two dimensionless variables combine discharge, mean depth and mean width of reaches. Independent model validations showed robust model predictions that are consistent with studies of habitat values for brown trout made in larger streams from western North America.4. Our results contribute to identifying the main hydraulic variables governing estimates of fish habitat values. They should facilitate habitat studies in multiple streams, at the basin or larger scales, while reducing their cost. They should enhance the biological validation of habitat model predictions, which remains critical.
Global patterns of diversity among the specialist birds of riverine landscapes
Authors: BUCKTON S. T. , ORMEROD S. J. 
Published: March 2003

1. Despite the growing view that biodiversity provides a unifying theme in river ecology, global perspectives on richness in riverine landscapes are limited. As a result, there is little theory or quantitative data on features that might have influenced global patterns in riverine richness, nor are there clear indications of which riverine landscapes are important to conservation at the global scale. As conspicuous elements of the vertebrate fauna of riverine landscapes, we mapped the global distributions of all of the world's specialist riverine birds and assessed their richness in relation to latitude, altitude, primary productivity and geomorphological complexity (surface configuration).2. Specialist riverine birds, typical of high‐energy riverine landscapes and dependent wholly or partly on production from river ecosystems, occur in 16 families. They are represented by an estimated 60 species divided equally between the passerines and non‐passerines. Major radiation has occurred among different families on different continents, indicating that birds have evolved several times into the niches provided by riverine landscapes.3. Continental richness varies from four species in Europe to 28 in Asia, with richness on the latter continent disproportionately larger than would be expected from a random distribution with respect to land area. Richness is greatest in mountainous regions at latitudes of 20–40°N in the riverine landscapes of the Himalayan mountains, where 13 species overlap in range.4. Family, genus and species richness in specialist riverine birds all increase significantly with productivity and surface configuration (i.e. relief). However, family richness was the best single predictor of the numbers of species or genera. In keeping with the effect of surface configuration, river‐bird richness peaks globally at 1300–1400 m altitude, and most species occur typically on small, fast rivers where they feed predominantly on invertebrates. Increased lengths of such streams in areas of high relief and rainfall might have been responsible for species–area effects.5. We propose the hypothesis that the diversity in channel forms and habitats in riverine landscapes, in addition to high temperature and primary productivity, have been prerequisites to the development of global patterns in the richness of specialist riverine organisms. We advocate tests of this hypothesis in other taxonomic groups. We draw attention, however, to the challenges of categorically defining riverine organisms in such tests because (i) rivers grade into many other habitat types across several different ecotones and (ii) `terrestrialisation' processes in riverine landscapes means that they offer habitat for organisms whose evolutionary origins are not exclusively riverine.
Endogenous regulation of environmentally induced sexuality in a rotifer: a multigenerational parental effect induced by fertilisation
Authors: Gilbert John J. 
Published: March 2003

SUMMARY1. Sexual reproduction in the heterogonic life cycle of many rotifers occurs when amictic females, which produce diploid eggs developing parthenogenetically into females, are environmentally induced to produce mictic females. Mictic females produce haploid eggs which develop parthenogenetically into males or, if fertilised, into resting eggs – encysted embryos which develop into amictic females after an obligatory diapause.2. A Florida strain ofBrachionus calycifloruswas used to test the prediction that amictic females hatching from resting eggs (Generation 1), and those from the next few parthenogenetic generations, have a lower propensity to produce mictic daughters in response to crowding than those from later parthenogenetic generations. In 10 replicate clones, populations initiated by amictic females from generations 1, 5, 8, 12 and 18 were exposed to a standardised crowding stimulus, and the proportion of mictic females in the populations was determined. These proportions varied significantly across generations and clones. They were very low in the early generations and gradually increased to a mean of about 0.5 at Generation 12.3. The mechanism for the transgenerational plasticity in response to crowding is not known. One possibility is that resting eggs contain an agent from their fertilised mictic mother's yolk gland that prevents development into mictic females and is transmitted in increasingly low concentrations through successive parthenogenetic generations of amictic females.4. This parental effect may contribute to clonal fitness by ensuring that a clone developing from a resting egg will attain a higher population size through female parthenogenesis before maximising its commitment to sexual reproduction, even in the presence of a crowding stimulus from a high population density of other clones. Therefore, the number of resting eggs to which a clone contributes its genes should be maximised.5. The clonal variation in propensity to produce mictic females in this strain indicates genetic variation in the trade‐off between maximising population growth via female parthenogenesis and increasing the probability of producing at least some resting eggs before local extinction from the plankton.
The effect of small zooplankton on the microbial loop and edible algae during a cyanobacterial bloom
Authors: Ventelä Anne‐Mari , Wiackowski Krzysztof , Moilanen Marianne , Saarikari Vesa , Vuorio Kristiina , Sarvala Jouko 
Published: March 2003

SUMMARY 1. We studied the effect of the small crustacean zooplankton on heterotrophic micro‐organisms and edible phytoplankton in a eutrophic lake during a cyanobacterial bloom.2. Small (15 L) enclosures were filled with natural or screened (100 μm) lake water and incubated for 5 days in the lake. Screening removed crustacean zooplankton but the initial density of rotifers and phytoplankton remained the same in control and removal treatments. Changes in the abundance and biomass of bacteria, autotrophic picoplankton (APP), heterotrophic nanoflagellates (HNF) and ciliates were measured daily.3. The crustacean zooplankton, dominated by the small cladoceran Chydorus sphaericus, did not affect cyanobacteria, the main phytoplankton group during the experiment.4. The removal of the crustacean zooplankton induced a higher abundance of ciliates and reduced that of the HNF, indicating the importance of ciliates in controlling HNF in this system.
Genetic structure and dispersal of Macrobrachium australiense (Decapoda: Palaemonidae) in western Queensland, Australia
Authors: Cook Benjamin D. , Bunn Stuart E. , Hughes Jane M. 
Published: March 2003

SUMMARY 1. The freshwater prawn, Macrobrachium australiense (Decapoda: Palaemonidae), is an abundant species throughout the rivers of western Queensland, and it is thought to have effective dispersal capabilities. Given the very low topographical relief of the western Queensland landscape and the vast nature of episodic flooding, it was predicted that widespread dispersal in this species would occur within, and possibly between the four major catchments of the region: the Darling, Bulloo, Cooper and Diamantina. We analysed eight polymorphic allozyme systems and a fragment of the cytochrome c oxidase subunit 1 (COI) mitochondrial DNA (mtDNA) gene to determine the extent of recent and historical patterns of dispersal at nested spatial scales, within and between catchments.2. Large and significant levels of allozyme and mtDNA differentiation were revealed among all catchments, indicating that dispersal of M. australiense does not occur across catchment boundaries, although this species is reportedly capable of overland movement. In contrast, no significant patterns of genetic differentiation were resolved between major subcatchments of the Darling and Cooper, or between sites within these subcatchments, indicating that populations of M. australiense are panmictic within catchments.3. The MtDNA data resolved two divergent and reciprocally monophyletic clades, with the first representing the Darling catchment, and the second corresponding to the Bulloo, Cooper and Diamantina catchments. We postulate that extreme variation in historical climatic patterns and palaeohydrologic conditions played an important role in shaping the population structure of M. australiense throughout western Queensland during the Quaternary.