bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regional coherence of climatic and lake thermal variables of four lake districts in the Upper Great Lakes Region of North America
Authors: Benson Barbara J. , Lenters& John D. ,   dagger, Magnuson John J. , Stubbs Maryan , & Timothy K. Kratz ,   Dagger, Dillon& Peter J. ,   sect, Hecky Robert E. , Lathrop Richard C. 
Published: March 2003

1. Within a region with common climatic conditions, lake thermal variables should exhibit coherent variability patterns to the extent to which they are not influenced by lake specific features such as morphometry and water clarity. We tested the degree of temporal coherence in interannual variability for climatic variables (air temperature and solar radiation) among four lake districts in the Upper Great Lakes Region. We also tested the degree of coherence of lake thermal variables (near‐surface temperature, eplimnetic temperature, hypolimnetic temperature and thermocline depth) for lakes within these districts.2. Our four lake districts included the Experimental Lakes Area in north‐western Ontario, the Dorset Research Centre area north of Toronto, Ontario, the Northern Highland Lake District in northern Wisconsin, and the Yahara Lakes near Madison in southern Wisconsin. Seventeen lakes were analyzed for lake thermal variables dependent on stratification. Another five lakes were added for the analysis of near‐surface temperature.3. The analysis tested whether for monthly and summer means, the climate (air temperature and solar radiation) across the four lake districts was coherent interannually and whether variables which measure the thermal structure of the lakes were coherent interannually among lakes within each lake district and across the four lake districts.4. Temporal coherence was estimated by the correlation between lake districts for meteorological variables and between lake pairs for lake thermal variables. Mean coherence and the percentage of correlations exceeding the 5% significance level were derived both within and between lake districts for lake thermal variables.5. Across the four lake districts, summer mean air temperature was highly coherent while summer solar radiation was less coherent. Approximately 60–80% of the interannual variation in mean summer air temperature at a site occurred across the entire region. Less than 45% of the variation in solar radiation occurred across sites.6. Epilimnetic temperature and the near‐surface temperature were highly coherent both within and between lake districts. The coherence of thermocline depth within and between lake districts was weaker. Hypolimnetic temperature was not coherent between lake districts for most lake pairs. It was coherent among lakes within some lake districts.7. The influences of local weather and differences among lakes in water clarity are discussed in the context of differences in levels of coherence among lake thermal variables and among lake pairs for a given variable.
Response of the cyanobacterium Gloeotrichia echinulata to iron and boron additions – an experiment from Lake Erken
Authors: Hyenstrand Per , Rydin Emil , Gunnerhed Malin , Linder Jeff , Blomqvist Peter 
Published: March 2003

1. This study considers whether the availability of iron and boron are important influences on the development of the cyanobacterium Gloeotrichia echinulata in Lake Erken, Sweden.2. In an in situ experiment, phosphate and nitrate were added to all enclosures, but pelagic colonies of G. echinulata only increased in abundance in enclosures to which iron had also been added.3. An even greater increase in the abundance of G. echinulata occured in enclosures in which the additions of phosphate, nitrate and iron were complemented by additions of boron.4. Boron additions, together with phosphate and nitrate but without iron, did not stimulate the growth of G. echinulata.
Allozyme diversity and population genetic structure of the caddisfly Orthopsyche fimbriata and the mayfly Acanthophlebia cruentata in New Zealand streams
Authors: Smith Peter J. , Collier Kevin J. 
Published: March 2003

1. Allozymes were used to measure genetic variation within and among regional populations of the caddisfly Orthopsyche fimbriata and the mayfly Acanthophlebia cruentata in North Island New Zealand streams.2. High levels of genetic differentiation were recorded in populations of O. fimbriata within and among catchments separated by more than 100 km, but little or no differentiation in populations separated by around 10 km. The Auckland isthmus appears to be a major barrier to north–south gene flow, with nearly fixed allelic differences at one locus. Genotype frequencies conformed to Hardy–Weinberg equilibrium.3. Acanthophlebia cruentata had low levels of genetic variation; the results are unexpected given that O. fimbriata apparently has greater potential for dispersal. The limited genetic data for A. cruentata provided evidence for genetic differentiation among populations separated by around 100 km, or more, within catchments and some differentiation between catchment populations separated by only 25 km.
Seasonal and spatial distribution of dissolved and particulate organic carbon and bacteria in the bank of an impounding reservoir on the Enns River, Austria
Authors: Brugger Albert , Reitner Bettina , Kolar Ingrid , Quéric Nadia , Herndl Gerhard J. 
Published: March 2003

1. Interstitial bacterial abundance, production and ectoenzyme activity were investigated over an annual cycle in an Austrian river when infiltration of oligotrophic river water into a river‐bank was artificially enhanced. These microbial parameters were related to porewater chemistry and the concentration of particulate (POC) and dissolved organic carbon (DOC).2. Porewater chemistry reflected the hydrodynamic mixing of infiltrating river water with riparian groundwater. Seasonal fluctuations in the microbial parameters resulted mainly from changes in temperature and organic matter supply. Seasonal change in porewater chemistry in the river‐bank was detectable laterally only within the first metre of the sediment and decreased rapidly with increasing distance from the sediment–water interface.3. The DOC concentration decreased only slightly during lateral transport through the aquifer, while total organic carbon (TOC) concentration as well as abundance and activity of interstitial bacteria were reduced by up to one order of magnitude within the top metre of the sediment. Retention of incoming particulate matter structured the lateral distribution pattern of TOC concentration. The POC and not the DOC pool was the main source of carbon for interstitial bacteria and, therefore, the quality of POC determines the distribution of microbial metabolism within the riparian zone.
Particulate organic matter inputs to a glacial stream ecosystem in the Swiss Alps
Authors: Zah Rainer , Uehlinger Urs 
Published: March 2003

1. Traps for litterfall and for lateral transport of organic matter were sampled over a 1‐year period along longitudinal and lateral transects in a glacial stream system (Val Roseg, Swiss Alps), which is characterized by single‐thread reaches and a large subalpine floodplain.2. Allochthonous inputs to the glacier stream were low close to the glacier terminus but increased as woody riparian vegetation and forests develop. Annual inputs varied from 0.4 g ash free dry matter (AFDM) m–2 year–1 (direct input) and 0.7 g AFDM m–2 year–1 (lateral input) in the proglacial area to 23.0 g AFDM m–2 year–1 (direct input) and 10.7 g AFDM m–2 year–1 (lateral input) in the lowest reach with adjacent subalpine forests.3. Direct inputs of organic matter decreased exponentially from forests at the floodplain edge to the floodplain centre, while lateral inputs of organic matter correlated linearly with distance to trees. Direct litterfall dominated litter input close to the forest, while lateral transport was the major pathway for channels more than 20 m away from the forest.4. A conceptual framework is developed illustrating the influence of terrestrial vegetation and fluvial morphology on organic matter input along the continuum of glacial streams.
Distribution of rotifer assemblages in North Island, New Zealand, lakes: relationships to environmental and historical factors
Authors: Duggan Ian C. , Green John D. , Shiel Russell J. 
Published: March 2003

1. The geographical distribution of planktonic rotifer species was investigated in 31 lakes in the North Island of New Zealand.2. A total of 78 species was recorded. Species richness, previously thought to be low in New Zealand, was found to be comparable with that of northern temperate lakes with an average of 21.1 species found per lake. The large, deep oligotrophic Lake Taupo had the lowest richness, and the artificial reservoirs the highest.3. The distribution of species, investigated using multivariate techniques [Cluster analysis, canonical correspondence analysis (CCA)], was most strongly associated with trophic state gradients. For example, Conochilus unicornis, C. dossuarius and Ascomorpha ovalis were associated with more oligotrophic conditions, and Brachionus budapestinensis, B. calyciflorus and Keratella tropica with more eutrophic conditions. Inorganic turbidity was also of importance in determining rotifer distributions in some shallower lakes.4. Some species, for example K. australis and C. exiguus, appear to be limited in distribution by poor dispersal abilities.
A continuous study of the total drift of freshwater shrimps, Gammarus pulex, in a small stony stream in the English Lake District
Authors: Elliott J. M. 
Published: March 2003

1. The objective was to determine the major factors affecting the downstream dispersal (drift) of freshwater shrimps, Gammarus pulex. Sample replication and frequency are major problems in the quantification of drift. For the first time, these problems were avoided by sampling the whole stream continuously so that all the shrimps drifting downstream at the sampling point were caught in a net emptied at dusk and dawn in 1966, and every 3 days in 1967.2. There was no consistent seasonal pattern in drift rates, but a high proportion of annual drift was taken in only a few samples. There was a nocturnal diel pattern of drift with peaks soon after dusk and just before dawn. A power function described the significant (P < 0.001) relationship between drift and flow, and was used to neutralise the dominant effects of flow by standardising total drift over 24 h, nocturnal drift and diurnal drift (drift per 50 m3). These were all significantly (P < 0.001) related to benthos density, but not to date, temperature, or length of the night or day.3. The relationship between drift values and the independent variables, flow and benthos density, was well described (P < 0.001) by a multiple‐regression model. Adding temperature, date, and/or the length of the night or day did not improve model fit. Variations in flow and benthos density explained 94% of the variation in total drift over 24 h, 97% of the variation in nocturnal drift, but only 44% of the variation in diurnal drift. A power function described (P < 0.001) the relationship between total drift and the volume of water sampled over 3‐day periods in 1967. Flow explained 95% of this drift variation; it was unnecessary to add another variable such as benthos density.4. The significance of this study is that it avoided the problems associated with the quantification of drift samples. Therefore, the conclusions are more robust than those of many previous studies. A high proportion of the annual drift losses would have been undetected by intermittent sampling. Temperature, season, night or day length had no significant effect on drift densities, and the relationship between drift and benthos densities was proportional, not density dependent. The nocturnal increase in drift could not be interpreted as an antipredator behaviour. The dominance of flow and benthos density was apparent but the quantitative relationships posed further questions, especially those related to drift distances at different velocities.
Comparative demographic impacts of `info‐chemicals' and exploitative competition: an empirical test using Daphnia magna
Authors: MITCHELL S. E. , CARVALHO G. R. 
Published: March 2003

1. Crowding `info‐chemicals', metabolites released into the environment that act as signals to conspecifics as well as other organisms, have often been shown to cause phenotypic plasticity in cladoceran life‐history traits including morphology, reproductive strategy and sex induction. Effects on population demography and diversity, however, have not been examined directly.2. Replicate laboratory populations of the zooplankter, Daphnia magna, were started with 250 juveniles and allowed to develop for 8 weeks in 10 L flow‐through aquaria with food levels of 1 mg CL–1. Two crowded water treatments from different clonal sources were compared with untreated water as a control.3. The presence of crowding chemicals affected initial population structure, through reduction in parthenogenetic female body lengths, brood sizes and juvenile densities. However, the timing of population density maxima and subsequent population structure, clonal composition and diversity were similar among all treatments.4. Clonal richness remained slightly higher in untreated populations because of increased prevalence of rare clones.5. Exploitation competition had greater impact on population structure than the relative concentration of crowding chemicals, indicating that density dependent effects were mediated primarily by competition for common resources.6. Crowding info‐chemicals may play a greater role in community structure than in single species population structure because of taxonomic diversity in species' response that may be unrelated to the source species density.
Photosynthetic efficiency and seasonality of autotrophic picoplankton in Lago Maggiore after its recovery
Authors: CALLIERI C. , PISCIA R. 
Published: March 2003

1. Lago Maggiore is a deep subalpine lake that has regained its previous oligotrophic state during the last decade after going through a process of cultural eutrophication and subsequent restoration. Autotrophic picoplankton (APP) have been studied in Lago Maggiore since 1992, with the primary production of the fraction being measured in 1994 and 1995. In 1998, we began to study the population structure and photosynthetic characteristics of APP after the restoration of the lake. We also compared the seasonal dynamics of APP and nanoplankton biomass and production. In this paper, we show the trend of annual and interannual dynamics of APP from 1993 to 1998.2. Since 1993 and 1994, APP have almost tripled in numbers (mean values: 1993=44 × 103 cell mL–1 1998=123 × 103 cell mL–1) and in production. On average, APP produced 16 gC m–2 year–1 in 1994 and 41.2 gC m–2 year–1 in 1998, accounting for 10 and 20%, respectively, of total phototrophic production.3. Although nanoplankton dominated in terms of biomass and production in the first 6 months of the year, APP were able to compete successfully with them in periods of P limitation. In September 1998, APP carbon fixation actually surpassed that of nanoplankton, reaching 13 mgC m–3 h–1 at 3 m. In a comparison of the daily chlorophyll‐specific photosynthesis rates of nanoplankton and APP, the latter proved to be more efficient in fixing carbon, particularly in summer and autumn.4. While the spatial distribution of APP abundance and production followed the isotherms of 18 and 20 °C, and was strictly related to water stratification and thermocline appearance, the APP efficiency [mgC (mg chl)–1Em–2] had its maximum at the bottom of the euphotic zone, with irradiance in the range 0.5–18 μE m–2 s–1.5. The existence of a significant regression between APP abundance and carbon fixation (P < 0.001, r2=0.92, d.f.=17; APPprod=10.6 × 103 cell mL–1 + 15) enabled us to infer APP production from cell numbers, and supports the view that picocyanobacteria production is closely dependent on its standing crop.6. Lago Maggiore is a good example of how APP in a stabilised oligotrophic system can, under favourable conditions, increase in numbers and effectively exploit the few available resources. We can conclude that the APP population reacts to the reduction in P‐levels, but only after several years of stable low nutrient conditions.
The seasonal dynamics and distribution of Chaoborus flavicans larvae in adjacent lake basins of different morphometry and degree of eutrophication
Authors: LILJENDAHL‐NURMINEN ANNE , HORPPILA JUKKA , ELORANTA PERTTI , MALINEN TOMMI , UUSITALO LAURA 
Published: March 2003

1.  Seasonal dynamics, spatial distribution and population size of the phantom midge Chaoborus flavicans in different parts of the eutrophic Lake Hiidenvesi (30.3 km2) were studied.2.  Density of larvae was low in the shallow, most eutrophic parts of the lake, while the deep Kiihkelyksenselkä basin was inhabited by a dense population. In the deepest part of Kiihkelyksenselkä (33 m) density was 13 989 ± 3542 m–2 in May, declined to 1102 ± 274 m–2 in July and recovered to 7225 ± 1314 m–2 by October. In spring and autumn the majority of larvae were benthic while, during high summer, few larvae were found in the sediment.3.  Horizontal distribution fluctuated seasonally. On 3 June < 5% of the population inhabited areas shallower than 10 m. On 6 July the limnetic fraction was still restricted to regions deeper than 10 m, but 43% of benthic larvae were found between 6 and 10 m depths. In October both limnetic and benthic larvae were concentrated in areas deeper than 20 m.4.  Within the lake, distribution was mainly regulated by stratification characteristics, degree of eutrophy being less important. The seasonal horizontal movements were probably induced by food shortage. Larvae could not meet their energetic demands in stratified areas and dispersed to shallower water, reducing predation risk by use of the benthic habitat.
Hydropsychid (Trichoptera, Hydropsychidae) gill abnormalities as morphological biomarkers of stream pollution
Authors: VUORI KARI‐MATTI , KUKKONEN JUSSI V. K. 
Published: March 2003

1. The use of morphological gill abnormalities of hydropsychid larvae was assessed in Hydropsyche siltalai larvae exposed to cadmium in the laboratory and Cheumatopsyche lepida and H. pellucidula larvae collected from a polluted river. Two biomarkers were evaluated: (1) Hydropsychid abnormality incidence (HAI), referring to the proportion of individuals with at least some abnormalities, and (2) Hydropsychid gill abnormality indice (HYI), referring to the average number of abnormal gill tufts for all individuals.2. Abnormality–contaminant relations for both biomarkers were established by studying gill responses along gradients of increasing cadmium and organochlorine concentrations. A cadmium gradient was verified in laboratory exposures, whereas the concentrations of polychlorinated dibenzo‐p‐dioxin (PCDD), dibenzofuran (PCDF) and diphenyl ether (PCDE) of the aquatic moss Fontinalis antipyretica were used as measures of an organochlorine gradient in the field.3. Morphological abnormalities were easily distinguished as heavy darkening, malformation and/or reduction of single gill tufts. Darkening of the gills appeared to start either at the basal or distal ends.4. A marked increase of HYI values with increasing Cd concentration reflected a clear abnormality‐contaminant relation, whereas the mere dicotomic classification of larvae as normal or abnormal (HAI) was less informative. High values of both HAI and HYI were associated with high contamination. A significant positive correlation was found between organochlorine concentration in mosses and biomarker values for H. pellucidula, but not for C. lepida.5. We conclude that HAI indicates deleterious effects, but fails to quantify the severity of degradation. Use of individual gill tufts, as response units in deriving HYI, revealed a simple solution to the quantification problem. Further research into the ecological meaning, physiological background and patterns of gill abnormality is recommended for assessing the applicability and relevance of hydropsychid gill biomarkers.
Community persistence in Broadstone Stream (U.K.) over three decades
Authors: WOODWARD GUY , JONES JOHN I. , HILDREW ALAN G. 
Published: March 2003

1. Few detailed long‐term data sets exist for fresh waters with which to examine large‐scale temporal changes in community composition. Consequently, insight into community persistence has been restricted to a few, contingent case studies. We collated and analysed data for the aquatic macroinvertebrate community of Broadstone Stream in south‐east England, spanning three decades. The pH of this naturally acid stream has risen progressively since the 1970s, and we sought to examine the potential effects of this environmental change upon the community.2. Persistence within Broadstone was high when compared with other systems that have been analysed using similar methods. The stream was characterised by a `core' community of eight taxa that were always present, and contributed 75–97% of total invertebrate abundance, with a trailing limb of progressively rarer and more acid‐sensitive taxa. There was little species turnover, although the time‐series exceeded 20 generations for most species.3. Despite this high persistence, a long‐term response to rising pH was detected: species indicating profound acidity (identified apriorifrom independent studies) have declined since the 1970s, whereas indicators of moderate acidity increased. The structure of the community food web has also changed since the 1970s, with increased predator diversity and abundance, and a lengthening of food chains following the invasion of a new top predator.4. These changes in the community appeared to be driven by an interaction between pH and climate. The unusually hot, dry summers characteristic of the 1990s may have raised pH during the more sensitive (i.e. early) stages of the life‐cycle, and thus provided a window of opportunity for less acid‐tolerant taxa to colonise and become established. Changes in pH appeared to set the boundaries of the available local species pool, within which biotic interactions ultimately shaped the community.
Restoration strategies for river floodplains along large lowland rivers in Europe
Authors: BUIJSE A. D. , COOPS H. , STARAS M. , JANS L. H. , VAN GEEST G. J. , GRIFT R. E. , IBELINGS B. W. , OOSTERBERG W. , ROOZEN F. C. J. M. 
Published: March 2003

1. Most temperate rivers are heavily regulated and characterised by incised channels, aggradated floodplains and modified hydroperiods. As a consequence, former extensive aquatic/terrestrial transition zones lack most of their basic ecological functions.2. Along large rivers in Europe and North America, various floodplain restoration or rehabilitation projects have been planned or realised in recent years. However, restoration ecology is still in its infancy and the literature pertinent to river restoration is rather fragmented. (Semi‐) aquatic components of floodplains, including secondary channels, disconnected and temporary waters as well as marshes, have received little attention, despite their significant contribution to biological diversity.3. Many rehabilitation projects were planned or realised without prior knowledge of their potential for success or failure, although, these projects greatly contributed to our present understanding of river–floodplain systems.4. River rehabilitation benefits from a consideration of river ecosystem concepts in quantitative terms, comparison with reference conditions, historical or others, and the establishment of interdisciplinary partnerships.5. We present examples from two large European rivers, the Danube and the Rhine, in which the role of aquatic connectivity has been extensively studied. The Danube delta with its diversity of floodplain lakes across an immense transversal gradient (up to 10 km) serves as a reference system for restoration projects along lowland sections of large rivers such as the Rhine in the Netherlands.