bluuebunny/crossref_metadata_2025_split huggingface dataset:
The rise and fall of Asterionella formosa in the South Basin of Windermere: analysis of a 45‐year series of data
Authors: MABERLY S.C. , HURLEY M.A. , BUTTERWICK C. , CORRY J.E. , HEANEY S.I. , IRISH A.E. , JAWORSKI G.H.M. , LUND J.W.G. , REYNOLDS C.S. , ROSCOE J.V. 
Published: May 2006

SUMMARY

The changes in abundance of Asterionella formosa in the South Basin of Windermere between 1946 and 1990 are described and analysed. The average seasonal cycle for the 45‐year period shows an overwintering population of about 10 cell ml−1 which increases with an exponential rate of 0.09 loge day−1 to an annual maximum of 4000 cell ml−1 by about Day 124. There is then a rapid decline at an exponential rate of loss of 0.29 loge day−1 to values which typically are less than 0.01 cell ml−1 in mid‐summer. By about Day 240 a second period of rapid increase occurs with an exponential rate of increase of 0.18 loge. day−1 to a plateau of about 7 cell ml−1 in late autumn and early winter.
This average pattern is subject to considerable year‐to‐year variation. The timing and extent of the increase in the autumn was particularly variable. The rate of increase in the spring was strongly positively correlated, and that in the autumn strongly negatively correlated, with the day at which the exponential phase started. Rates for these two phases of increase were not statistically different when expressed in terms of time from mid‐summer, which reinforces earlier conclusions that light availability is the main factor governing the rate of spring increase and suggests that this is also the case for the autumn increase.
Eight descriptors of seasonal development showed statistically significant changes over the 45 years. Early winter populations declined from 27 to 4 cell ml−1, and linked to this the day at which cell concentrations exceeded 50 cell ml−1 occurred later by 24 days from Day 54 in 1946 to 78 in 1990. The lower early winter population appears to be linked to a lower end of year population as this decreased between 1946 and 1968 from 46 to 2 cell ml−1, and then increased slightly to 7 cell ml−1 in 1990. The start of the spring exponential increase occurred on Day 57 in 1946 and started earlier by 19 days in 1968 but then occurred later, at Day 76, in 1990. The duration of the spring increase got shorter by 23 days, from 67 days in 1946 to 44 days in 1990. The maximum rate of increase rose from 0.065 loge day−1 in 1946 to 0.112 loge day−1 in 1990. The annual maximum declined from 9863 cell ml−1 in 1946 to 2278 cell ml−1 in 1968 and then increased to 6159 cell ml−1 in 1990. The annual geometric mean decreased from 61 cell ml−1 in 1946 to 5 cell ml−1 in 1968 and remained nearly constant subsequently.
In many cases, the precise underlying causes of these changes were not apparent. However, the increase with time of rate of increase in the spring appeared to be linked to a later start and hence growth under higher light. There was no significant cyclical change in any of the descriptors studied.
Size dependence of composition, photosynthesis and growth in the colony‐forming freshwater ciliate, Ophrydium versatile
Authors: SAND‐JENSEN KAJ , GEERTZ‐HANSEN OLE , PEDERSEN OLE , NIELSEN HELLE SKOVGAARD 
Published: May 2006

SUMMARY1. Ophrydium versatile is a symbiotic ciliate which forms gelatinous colonies up to several centimetres in diameter in transparent temperate lakes. The ciliates are evenly spaced at the colony surface and constitute a small proportion of the surface area (7%) and volume (3.1%) of the colony, but a large proportion of organic carbon (74%) and nitrogen content (82%) (exemplified for 1 cm3 colonies). The majority of the colony volume is formed by the jelly. The biomass proportion of ciliates scales inversely with colony size, following the decline of surface area to colony volume. The largest colonies found in Danish lakes in early summer contain almost 1 million ciliates, and assuming they derive from a single ciliate undergoing exponential division, they need twenty generations and, presumably, almost a year to reach maximum size.2. The ciliates contain numerous symbiotic zoochlorellae that constitute about 10% of ciliate volume and more than half of the carbon content. Zoochlorellae dominate oxygen metabolism of the assemblage, resulting in low light compensation points, a large diel photosynthetic surplus, and a marked dependence on light for sustained growth and ciliate metabolism. Estimated gross photosynthesis (7ng C ciliate−1 day−1) of Ophnrydium from shallow, clear waters in June greatly exceeded the estimated carbon contained in filtered bacteria and small algae (1.9ng C cilicate−1 day−1). Nitrogen and phosphorus content of the prey, however, may provide the main nutrient source consistent with the correspondence between mass‐specific rates of nutrient uptake and measured relative growth rates (average 0.067 day−1, generation time 10 days).3. The large Ophrydium colonies require increased allocation of photosynthetic carbohydrates with increasing colony size to maintain the jelly. The large colonies tend to become gas‐filled, floating, mechanically destroyed and their ciliate inhabitants abandon them as swarmers. Colony formation, however, should offer protection against predators which may be more important for the natural abundance than the costs of growing in a colony.
Disturbance and the temporal variability of invertebrate assemblages in two Andean streams
Authors: FLECKER ALEXANDER S. , FEIFAREK BRIAN 
Published: May 2006

SUMMARY1. Monthly variation in patterns of invertebrate density was examined in two streams in the Venezuelan Andes that differed in elevation, geomorphology, and disturbance regime.2. At one stream, located in the Andean piedmont, invertebrate densities displayed large fluctuations and between‐month variation differed by as many as four orders of magnitude. Major declines in invertebrate numbers were generally associated with frequent disasters, defined as channel‐shifting spates and drought.3. At the other stream, a montane site located at higher elevation, invertebrate densities varied by tittle more than an order of magnitude over the duration of the study. Reductions in invertebrate numbers between successive months generally occurred during the rainy season.4. Monthly invertebrate densities were inversely related to rainfall at each site. In addition, a highly significant positive relationship was observed between invertebrate density and the number of days elapsed since the previous major rainstorm event. Relationships between rainfall and invertebrate densities differed between streams, however, with significantly steeper regression slopes being found at the piedmont than the montane site.5. We suggest that disturbance plays a seasonally important role in structuring neotropical stream communities in which changes in discharge are severe and unpredictable. Our data contrast with studies from tropical floodplain rivers in which rainy‐season floods are predictable events that cannot be readily characterized as disturbances.
Estimating the abundance of subterranean propagules of submersed aquatic plants
Authors: SPENCER DAVID F. , KSANDER GREGORY G. , WHITEHAND LINDA C. 
Published: May 2006

SUMMARY1. Data on sample means (x|) and variances (s2) of propagule abundance for five typos of aquatic plants growing in a variety of habitats were collected. The data set consisted of 379 values for x| and s2, based on 4942 individual sample units (sediment samples), drawn from the literature or from data collected as part of this study.2. Regression analysis relating log s2to log x| yielded an equation which was solved for the number of sample units (n) required to achieve a given degree of precision. For precise estimates [standard error (SE) = 20% of x|], values ofnbetween twenty‐seven and 234 are required when propagule density is low (<200m−2), whereas eight to twenty‐six sample units are required when propaguie density is high (200–1000 m−2). For larger SE (i.e. 30% of x|),ndecreased by about 50%. Sampler area (20 to 1600cm2) did not affect estimates ofn.3. Time required to collect and process sediment cores (collected with either a 5, 10, or 15cm corer) was approximately 7, 10, or 13min, respectively. Combining this information with the required number of samples is useful in planning studies designed to measure changes in the abundance of underground propagules of submersed aquatic plants.
Longitudinal effects of herbivory on lotic periphyton assemblages
Authors: McCORMICK PAUL V. , LOUIE DENISE , CAIRNS JOHN 
Published: May 2006

SUMMARY1. The longitudinal effects of herbivory on stream periphyton assemblages were examined in laboratory stream channels, each of which consisted of an upstream chamber, which either contained snail grazers or not, and downstream chambers, none of which contained grazers. Periphyton assemblages of two ages (0–21 days old and 21–42 days old) were sampled in both upstream and downstream chambers to detect proximate (i.e. localized) and longitudinal (i.e. downstream) effects of herbivory.2. Both proximate and longitudinal effects were detected, although they differed in their impact on the periphyton assemblage. Periphyton biomass and cell accumulation were lower in grazed than in ungrazed upstream chambers throughout the experimental period. Accumulation rates on initially bare tiles were substantially higher downstream of grazed than of ungrazed chambers, but grazing had no effect on cell densities in established (21–42 day old) assemblages downstream.3. Longitudinal effects of herbivory were not due to quantitative differences in the flux of propagules or nutrients from grazed and ungrazed chambers. Although not tested in this study, it is hypothesized that differences in the physiological condition of exported propagules may have contributed to differences in downstream colonization rates in grazed and ungrazed streams.4. The magnitude of longitudinal impacts of herbivory and the importance of different causal mechanisms are predicted to vary depending on the standing crop and productive capacity of the periphyton assemblages as well as the consumptive demand of the herbivore guild.
Recurrent response patterns of a zooplankton community to whole‐lake fish manipulation
Authors: HE XI , SCHEURELL MARK D. , SORANNO PATRICIA A. , WRIGHT RUSSELL A. 
Published: May 2006

SUMMARY1. In a series of whole‐lake manipulations conducted from 1984 to 1991, planktivorous fishes were alternately removed and restocked in a small mesotrophic lake, resulting in dramatic changes in the zooplankton community.2. Response patterns in the zooplankton community, which include species and size structure, and within‐year community variability, were examined. Variation in the zooplankton community in unmanipulated years was much lower than that in manipulated years, regardless of direction of the manipulation (i.e. decreasing or increasing planktivory).3. The succession of zooplankton species abundance was repeated in the second removal of planktivorous fishes. The community shifted from small‐bodied cladocerans, copepods and rotifers, through an intermediate state with high abundance of Holopedium, to an assemblage dominated by large‐bodied daphnids.
The role of drought in the impact of climatic change on the microbiota of peatland streams
Authors: FREEMAN C. , GRESSWELL R. , GUASCH H. , HUDSON J. , LOCK M.A. , REYNOLDS B. , SABATER F. , SABATER S. 
Published: May 2006

SUMMARY1. Simulation of climate change (summer drought) stimulated autotrophy in a stream draining a Welsh peatland. Biofilm autotrophic biomass (chlorophyll) increased by 145% and was correlated with an increased overall metabolic activity (r = 0.75, P<0.05). Bacterial population densities were not significantly affected.2. The increased autotrophy was probably related to a decrease in the organic:inorganic ratio of nutrients released from the wetland to the stream.3. Bacterial reserves of poly‐β‐hydroxyalkanoate (PHA) fell by 51%. Increased nitrate concentrations were inversely correlated with autotrophic diversity (r=−0.88, P < 0.001).4. The increased autotrophic biomass represents an increased nutrient supply for the higher trophic levels which could promote higher productivity within the stream ecosystem as a whole.5. The simulation also caused a cooler (11%, P<0.01) streamflow from the drought‐impacted wetland, which could mitigate against any adverse temperature‐dependent effects of future climatic change.
Glacial rivers: physical habitat and ecology
Authors: MILNER ALEXANDER M. , PETTS GEOFFREY E. 
Published: May 2006

SUMMARY1. This review examines the physical habitat and ecology of glacial rivers which have been relatively unstudied compared with rivers originating from other sources.2. Typical glacial rivers have summer temperatures below 10°C, a single seasonal peak in discharge, which in the Northern Hemisphere typically occurs in July, a diel fluctuation in flow which usually peaks in late afternoon, and turbidity levels in summer that exceed 30 NTU. These variables contrast with those in snowmelt/rainfall streams, particularly in summer, and make conditions more extreme for the biota.3. Where maximum temperatures are 2°C benthic invertebrate communities are dominated by Diamcsa (Chironomidae). Downstream, temperatures increase, channels become more stable and valley floors become older. Orthocladiinae (Chironomidae), Simuliidae, Baetidae, Nemouridae and Chloroperlidae become characteristic members of the invertebrate community.4. Fauna may be displaced, or at least colonization delayed, by channel instability; the variable age structure of the valley floor will influence the faunal gradient, which may also be reset by the effects of tributaries, lakes and valley confinement.5. We propose a qualitative model that outlines zoobenthic community gradients determined by two principal variables, water temperature and channel stability, as a function of distance downstream, or time since deglaciation.
Macroinvertebrate communities of streams in western Nepal: effects of altitude and land use
Authors: SUREN ALASTAIR M. 
Published: May 2006

SUMMARY1. The influence of altitude and land‐use changes on macroinvertebrate assemblages from riffles in forty‐three streams in the Dolpo region of western Nepal were examined. Sampling sites ranged in altitude from 850 to 4250m, and land‐use patterns fell into five categories: alpine, forest, grassland, pasture and agricultural land.2. TWTNSPAN classification of physicochemical data separated streams into groups on the basis of climatic and physical factors. Streams from high, cold, alpine areas were separated from those in warmer, lower, agricultural areas.3. In all, 138 macroinvertebrate taxa were collected from fifty‐three insect families. Ephemeroptera were most common, especially Baetidae.4. Taxonomic richness declined with increasing altitude. Ten insect families were significantly more abundant in lowland streams, and five were more common in alpine streams.5. TWINSPAN and DECORANA revealed distinct invertebrate groupings of the forty‐three streams surveyed. A high percentage of the variance (79.3%) in ordination space was explained by DECORANA axes 1 and 2. Altitude, temperature, stream width and land use were implicated in structuring invertebrate communities.
Macroinvertebrate community structure and altitudinal changes in the upper reaches of a warm temperate southern African river
Authors: PALMER CAROLYN , PALMER ANTHONY , O'KEEFFE JAY , PALMER ROBERT 
Published: May 2006

SUMMARY1. The Buffalo River rises 1200m above sea level, drops 600m in the first 7km, and a further 100m in the next 30 river kilometres. Macroinvertebrates were sampled, and environmental variables measured monthly in 1987, at four sites along this part of the river.2. Flow at the headwater site (1120m a.s.l., 1 km from the source) was seasonal, though pools remained and subterranean flow was continuous. Twelve macroinvertebrate taxa were found exclusively at this site, where conductivity, pH and nutrient concentrations were low.3. Flow at the foothill site (530m a.s.l., 7km from the source) was perennial. The invertebrate community, although distinct from that at downstream sites, lacked the unique taxa of the headwater site. Conductivity, pH and nutrient concentrations were higher.4. The two sites downstream of the foothills (450m a.s.l., 18km from the source, and 410m a.s.l., 31 km from the source), had similar invertebrate communities. Conductivity, pH and nutrient concentrations were higher than at the upper sites.5. Community structure changed most between the headwater and foothill sites. This paralleled changes in river steepness rather than changes in measured physicochemical variables.
Theoretical habitat templets, species traits, and species richness: aquatic Coleoptera in the Upper Rhône River and its floodplain
Authors: RICHOUX PHILIPPE 
Published: May 2006

SUMMARY

To test predictions of the river habitat templet and the patch dynamics concept, trends in species traits and species richness of aquatic beetles were related to the spatial‐temporal variability of eighteen habitat types in the alluvial floodplain of the French Upper Rhône River. One hundred and twenty species of beetles were used in this analysis.
The basic information was obtained either from the literature (for most of the species traits) or from observations made at approximately 500 sampling sites in the Brégnier‐Cordon and Jons sections over the past 19 years (for habitat utilization). This information was structured by a fuzzy coding technique and examined by ordination analyses.
Analyses of the relationships among nineteen species traits revealed a clear distinction according to traits such as body form (for adults), functional feeding type and food (adults and larvae), attachment to the substrate and dissemination potential (adults and larvae), and patterns of aquatic and/or terrestrial life of adults and larvae. Species traits such as number of descendants per reproductive cycle, and number of reproductive cycles per year or per individual showed less contrast, because these traits are rather homogeneous in aquatic beetles.
Analyses of the habitat utilization by the aquatic beetles revealed a vertical gradient that separates interstitial from superficial habitats, and a transverse gradient for the superficial habitats, which extends from the main channel towards permanent oxbow lakes and temporary waters.
The significant relationship betweeen species traits and habitat utilization demonstrates that most beetle species use a particular set of habitat types with a particular set of species trait modalities.
Species traits of aquatic beetles are homogeneous but evidently very successful and are adapted to many potential conditions of spatial–temporal variability. Because of this homogeneity, observations on aquatic beetles do not support trends of traits in the framework of spatial–temporal variability predicted from the river habitat templet.
The observed species richness of aquatic beetles is low in habitat types with a low spatial–temporal variability, increases as spatial variability increases, and tends to be highest at intermediate temporal variability. This pattern matches predictions of the patch dynamics concept.
Theoretical habitat templets, species traits, and species richness: Trichoptera in the Upper Rhône River and its floodplain
Authors: TACHET HENRI , USSEGLIO‐POLATERA PHILIPPE , ROUX CHANTAL 
Published: May 2006

SUMMARY

For Trichoptera occurring in two sites of the Upper Rhône River (France) we examine: (i) relationships among species traits; (ii) habitat utilization of Trichoptera species; (iii) the relationship between species traits and habitat utilization; (iv) trends of species traits in the framework of spatial–temporal habitat variability to test predictions of the habitat templet concept; and (v) trends of species richness in the framework of spatial–temporal habitat variability to test predictions of the patch dynamics concept.
Of the sixteen species traits selected, twelve have high correlation ratios for the seventy‐five species used in this analysis; these traits are related to behavioural, morphological, or physiological aspects. Traits related to reproduction or life cycle have lower correlation ratios.
An ordination by species traits separates the five main families into three groups: (i) Hydropsychidae and Polycentropodidae; (ii) Hydroptilidae; and (iii) Leptoceridae and Limnephilidae. An ordination of the habitat utilization of the species in ten habitats indicates that the Hydropsychidae occur preferentially in the main channel, Hydroptilidae, Polycentropodidae, and Limnephilidae occur in backwaters or oxbow lakes, and the Leptoceridae are ubiquitous.
The Hydropsychidae exhibit a relationship between species traits and habitat utilization, i.e. they use similar habitat types with similar species traits. The species traits of the other four families are similar but their habitat utilization is quite different.
The Hydropsychidae occur in lowest spatial–temporal variability habitats and Limnephilidae in the highest. Therefore, net spinners and filterers are characteristic of habitats with a low spatial–temporal variability, whereas shredders and case makers using plant material are characteristic of habitats with high spatial–temporal variability. The trends in species traits show little agreement with trends predicted from the river habitat templet.
Trends of species richness in the framework of spatial and temporal variability do not follow the predictions of the patch dynamics concept because richness is similar in all superficial habitats. This implies that each habitat, in spite of large differences in their spatial and temporal variability, offers Trichoptera a similar but limited number of ecological niches.
Sulphate reduction in the hypolimnion and sediments of Lake Kinneret, Israel
Authors: HADAS O. , PINKAS R. 
Published: May 2006

SUMMARY1. Lake Kinneret is a warm (13–30°C) monomictic lake. Between January and June a heavy annual bloom of the dinoflagellate Peridinium gatunense dominates phytoplankton biomass (250 g m−2). At the beginning of the summer, degradation and decomposition of the Peridinium biomass occurs, serving as a trigger for intense sulphate reduction in the hypolimnion and sediments.2. The rates of sulphate reduction in the sediments varied seasonally from 12 to 1700 nmol SO4.−2 reduced cm−3 day−1 in December and July, respectively. The availability of organic matter and sulphate is high in June after the crash of the Peridinium bloom and the beginning of stratification and is lowest in December before overturn.3. Sulphate concentrations in the hypolimnion range between 0.52 mM and 0.20 mM during mixing (January‐April) and before overturn (December), respectively. The depletion in sulphate in the hypolimnion is stoichiometrically correlated to the increase in sulphide. The lake is not depleted of sulphate at any time, so the sulphate reduction process in Lake Kinneret is not limited by sulphate concentrations except in the sediments just before overturn.